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Design

New Laser C5 rig evolution

12 March 2019

Getting into specifics, as commented early in the piece, I’m 95kgs as is Chris (though Chris is a whole lot more fit), so it’s pretty logical that the initial work has been done on the big rig.

The photos below are the Mk2 rig, the Flame rig was the Mk4 and the C8 is a Mk6 rig and in both cases the boat is being sailed by Tom Burton.   In the first photo, the shot is taken in the sound of Castle Rock, Middle Harbour and the other sailor in the Laser is Gerard West.

Standard Laser and Mk 2 rig


Flame rig (Mk 4)

Mark 2 rig
The grey shot is taken on Lake Macquarie in late 2014.

In the black/grey/white photo, the green line is horizontal (off the shore line), the blue line is parallel to the green, call it a waterline.  The red line is up under the gunwales aft, the boat is being sailed at 5.25° heel, pretty flat.  The 2 yellow lines are dropping from the CoG of the respective masts.  (Click on photos to enlarge.)

Again, I stress the Mk6 C8 mast is heavier, but it’s also straighter.  And I would expect the alloy mast to bend more lower down.

Some people have no idea what I am talking about re the Flame Rig, so I have included that also, it’s Dec 2015 and a Mk4 rig.

Just want to touch on a few points.

TGi – Temperature Gradient index.    I’m not an industrial chemist or a structural engineer, so I have been told this is a TGi thing, but don’t quote me on it.

I was born in NZ but lived all my life in Australia, and Australia is hot, much hotter than Europe and most of the US.   But nothing prepares you for the tropics.   And a lot of the people we are targeting live in Asia not far from the Equator.

We had a stark lesson not so long ago, we had supplied 20 odd masts for a single-hander to a sailing club in Singapore, and Singapore is less than 1° from the equator.   The kids came in for lunch, dropped the booms off (Pin head rigs) and got out of the sun and had lunch.  Came out after lunch, hook the sails up went sailing but something was wrong.   Cut a long story short, all 6 masts had got so hot that they had re-set, bent.    Took a week but as always is the case, we heard about it.   What we found out was someone in Singapore plugged the topmast “to make them float”.    What transpired was the core temperature of the mast rose to well in excess of 150C, well above the masts’ TGi.

It’s just one of those things, all these masts are made as part of a std production process, the tapes, the resins, all of that is designed for specific temperatures and if you want to go hotter, then the prices skyrocket.

To overcome this we leave the mast open, so it can behave like a chimney, with the hot air going up the inside, meaning that in Arabia, the Caribbean, Singapore, Brunei all of these places the mast will remain “within its TGi”.     You will never see this in Europe, most of the USA, in fact most places outside the tropics, but if you want a world-wide boat with a FRP mast you had better have a plan.

Vang loads One of the big differentiators is vang loads. In std Laser, be it Radial, 4.7 or Std rig, first thing you do when you get on board is strap on the vang as hard as you can, and once you have done that you pull it some more.

With a Square-head rig, it is very easy to over vang the sail.     First thing is the downhaul becomes your primary camber control.   We have even gone so far as to couple the Downhaul and the Outhaul together to make one Camber control.

This opens up the vang as a twist control, it de-burdens it as a camber control, and that in turn allows a lighter crew to ease the vang and opening the leech to de-power the top of the sail.   It also allows a heavier crew to firm up the vang, close the leech and power up the whole rig.

The boom is also a lot more substantial, so you simply don’t have to “vang it down”.

Mast bend One of the reasons we use a Square head is that the de-powering process is spread across 3 “design tools”.    The bend of the mast is one, and it’s very evident in the shot of Gerard and Tom, the mast bend of a Square-head rig is about 1.5-1.7% max, whereas the mast bend of a Pin-head or quasi Pin-head rig is 5-6%.   Added to that, the FRP mast has a smaller diameter.     And this is a x² law, so for every extra 1% in bend, and extra diameter, the elongation of the fibres is exponentially more.   “elongation of the fibres” = mast longevity, as in the less they move the longer the mast will last, and unlike alloy, provided you stay under a %, the elastic limit of the carbon which is about 0.9%, simply won’t fatigue.

1st and 2nd batten, I call it Euler Crippling load, I know Steve Clark calls it Buckling load, maybe it’s the difference between Aviation speak and Boat speak, but he is the same guy, 17th Century mathematician.  The top 2 battens on a square head also play a pivotal role in the depowering process, they can be set to trigger the “stand up” or “lay down” mode, and that in turn can be set by the downhaul tension.

Sail cloth, the choice of sail cloth and the rocking of the panels is also very important.   Again, stay within the elastic limits of the Mylar, rock the panels correctly and couple all that with the top 2 battens and the elasticity of the sail-cloth can be dialled in to get the mainsail to do the right thing at the right moment.

Full length battens, while on the subject of battens, we did try ½ battens, and we would have saved a bit more weight but the whole performance of the rig becomes compromised.

It’s a very small price to pay, about 400gms, for a far more complete package, that will last longer and behave consistently all the time.

Start line, people say you can’t start well with full length battens but just go look at any AC race, or closer to home, 49er and 29er racing, Int Moth Racing.  I know in the 49er class they have developed a technique to “crab to windward”.   It’s just a different skill set and the C5 kids will get it in the blink of an eye.

Performance, Theory vs Empirical. Tom and Gerard are highly skilled sailors who have worked very hard to get the very best out of the existing Std Rig.   The day the shot was taken, by me from Michael Blackburn’s rib, exactly what you would expect to happen happened, it was close but he who sailed the std rig won out, certainly upwind, not by much and for anyone to have stepped into a new set-up and expect instantaneous speed advantage is wishful thinking.   This was the first time they had seen the rigs.    Downwind, it was not so clear and the new rig had as many wins as it had losses.

This was the Mk2 rig, we are now at a Mk6 with the Flame Rig (Mk4) being the break through.

The simple fact of the Mk2 rig is the mast weighs 4.4kgs complete (it’s now a little heavier being check-in-able) whereas the std mast is 10.4kgs.   The centre of gravity of the Alloy mast is 3m (approx.) above WL, the Carbon rig is 2.5m.   That sum is pretty easy, 10.4 x 3m = 31.2kgs/m² inertia, whereas the Carbon rig is (say 5kgs with the heavier battens) 5 x 2.5 = 12.5kgs/m².

What this tells us is that if (when) a gust hits you and the rig starts rotating to leeward, it is going to take less than ½ the effort to stop that rotation.

The other key factor is what I call counter-RM [righting moment].    Let’s say Tom weighs 80kgs, a laser is 1.39m beam, Tom’s feet are ½ way, maybe, so 0.7m, his backside is say 300mm to windward of the gunwale and the CoB [Centre of Buoyancy] at 6° heel is 100mm to leeward, so he has 1.1m Arm.

Therefore, he is generating 80 x 1.1 = 88kgs/m torque (don’t ask me to go into SI’s).

The rig is hanging out to leeward of the boat and if you do that maths, looking at the photos you will see that a std rig, 3m up, is 475mm to leeward.

You can again can now do another sum, which is 10.4kgs x .475 = 5 kgs/m negative or counter RM.   The Carbon rig 5 x .356 = 1.7kgs/m counter RM.

So, some assumptions:

  • I am assuming all other things are being equal, the weight of the sail is roughly the same (but I have bounced the C-rig weight up because of the battens).
  • That they are going to hang to leeward about the same.   The alloy rig being a straight extruded tube will bend most as it comes out of the deck, at the max load point, whereas the FRP tube, is 4.5mm thick as it come out of the deck so it’s less likely to “kink”, as in, bend excessively at deck level.
  • This is a Mk2 C8 rig, and it has evolved dramatically over the last 4 years (how time flies when your having fun).
  • The weight difference between the 4.7 mast and the C5 is greater, but the kink to leeward will be less pronounced with the C5.

The simple reduction in weight, the dramatic reduction in inertia and the reduction in Counter RM, given the history of carbon rig conversions means that with time, the Carbon rig boat will get to max speed earlier, stay at max speed longer and/or point higher due to lower drag.

Julian Bethwaite

Laser C-Rig continued

7 March 2019

99% of design is from top down.   I’m big (95kgs) and when being asked to design for 45-60kgs your first reaction is to scale down.

But I am also lucky in that we tried to do that, with Takao WRT the 29er and we had learnt that it did not work.   The 29er is not a scaled down 49er, rather it is its own unique design and that’s possibly why 29ers are so much faster than the 49er at the extreme.

So, when we started to get bogged down with the C5, Takao suggested that we forget about “Flame rigs” and go right back to first principals.     We did an analysis on the Std Laser Rig, the Radial Rig and the 4.7 rig.    We knew the 4.7 was great in a breeze which is why it’s so successful in Europe, but it’s poor in light air, and with that in mind, we looked at 100s of photos of rigs and also of people sailing Lasers.   We also had a raft of data from Tom Burton from a program called SailEQ which is another spin off from this whole program.

We used the std rig as a base line, and we determined that a well-sailed Laser was sailed at 6° heel, as said before this is mostly to keep the skipper’s butt out of the water.  We also determined that the “lead” so the distance that the CoE of the sail is in front of the CLR was about 130mm.    In a boat sailed flat, this would lead to lee-helm but because a Laser is sailed at best, at 6° that results in the well known weather-helm.

What we found with the 4.7 rig was this “lead” was upwards of 300mm so in conditions of not so much wind where the skipper is sitting upright and the boat is less than 6° heel, and without mainsheet tension pulling the CoE aft, you do get a lot of, in most cases lee-helm and that has always felt awkward.

“Lead” is when the CoE is in front of the CLR
“Trail” is when the CoE is behind the CLR

CoE = Centre of Effort, the point on the sail where all the forces are resolved

CLR = Centre of Lateral Resistance, the point (in the case of a skiff) in the centreboard where the forces are resolved.

Lasers have Lead because when the boat is heeled it wants to round up, like a yacht, and a 49er has Trail because when it’s sailed flat there is no round up.  In a perfect world you carry about 10% of the side load on the rudder, it’s about 28% of the combined area so you load it up about ½ (kgs/m²) of the centreboard, hence wanting a little weather helm.

In a breeze, the kids in Europe are good, they strap their sails down to the deck, pulling the CoE aft and they sail often at heels far greater than 6° because it feels good.    Pretty obvious why.

The next thing we found when we actually measured the area, a 4.7 is not 4.7m² it’s actually a little under 5.1m².  In fact, we found all the areas across all 3 rigs are understated.    It all depends on how you measure the area, and to be honest, the area is just a number, what’s important is that you use the same system across the whole design spectrum.

Next bit gets interesting, in that we already knew that if you reduced weight aloft, as in going to a mast like a carbon rig, you have to increase sail area or you will skew the rig to lighter weights.   With the 49er we tacked on 170mm of mast height and approx. 1.5m² in area on a total area of 20.5m², but with the 49er we also wanted to increase crew weight, and to date, that’s exactly what’s happened.

We also had the Flame rig data and to a lesser extent information from the 29erC rig.

We knew we had to up the area, approx. 10%, so say 0.5m² was about the target, but we decided to hold that down to 0.4m² because the target was smaller Asians and it also allowed us to reduce the mast height so even though there was more area, the Arm (distance between CoE & CLR vertically) actually reduced.

To be honest, I don’t know where we ended up, because empirical testing always trumps theoretical but my guess is we are at 5.4 – 5.5m²

By this stage, we were committed to a square head, but the big issue with a square head is how big should the length of the top batten be.     If it’s too big/long then you have to use excessive downhaul tension to make it reactive.   Too short, and it may as well be a pin-head rig and you lose all the advantages.

The big advantage of a square-head over a pin-head is the mast bend is ½ !    Long term that leads to near indefinite mast life.    It also reduces problems with hoisting the main,  and having overly hooked leaches in light airs.

Ian MacDiarmid and I worked on this along with mast stiffness and position of the bend so that we could end up with reasonable downhaul tensions which allows us a wide range of crew weights and without excessive vang loads.   We reduced foot lengths, but the big breakthrough was being able to “splice” the mast at deck level.  This allowed us to drop the whole mast further aft, it allowed us to use a stiffer topmast and it got the Lead down into the 120-130mm in all wind ranges, so the helm felt good.   Later Takao made some unilateral decisions to reduce the “splice” to reduce the helm when sailed at 6° and Clive Watts (CST) was able to deliver us a “kinked” mast at deck level and that reduced weight and cost.

In December this year Takao and I played with vang lengths, which allows us control over lower mast camber.   Sure, we threw away some booms that had become Swiss cheese and the lower mast of the now C8, it’s quite hard to believe it’s still standing but we had something really special.

Late Feb this year I happened to be in Longchi, China, working on the 29erC rigs and I watched 2 smallish Chinese girls struggling with a 4.7 rig.   Everything Takao had talked about was there in front of my eyes.

Above is a work sheet which was the initial drawing for the proposed C5 rig, dated July 2016 (click on image to enlarge).

The Lead on the laser std is 136.83 but would obviously be less than that with the main sheeted hard down.    4.7 is 295.84, more than double.   What’s important when you do this is to remain consistent, so these may, in fact, not be the “actual” numbers, but they are relative.

We have the splice at 7.5° in this, we ended up less after Takao opted for less weather helm, we also ended up a bit bigger than this shows, with longer cord lengths.     I need to re-do those measurements.

Julian Bethwaite

Laser C-Rig history

6 March 2019

It’s been about 4 months since Eric Faust (Exc Sec of ILCA) showed the C5 video at Sarasota, which was then shown on Sailing Anarchy, Scuttlebutt and other social media platforms and some suggested that I should not add facts to spoil a good conspiracy theory.

It’s time to just set the record straight so the conversation can be re-centred.

C-Rigs, as they have become known, spun out of a far more comprehensive rig development project that Up Marine started in 2012.   In chronological order:-

Up Marine decided to use the Laser because of its superior numbers and simplicity.

Chris Caldecott (GM, PSA) found out about the project, mid 2014 and asked if we could ‘screw’ the development to generate a new carbon rig for the Laser.   MoU’s were generated and we altered focus a little.

At the 2014 ILCA conference (Nov), I am told, Chris showed photos and reported on the development.

2015 a Worldwide Patent was applied for (by Up Marine) and has been subsequently granted.

2015 ILCA conference (Oct), what is now referred to as the C8 rig, was reported in glowing terms and I am told that focus changed from the C8 prospect to the C5 and the plight of Asians given that the 4.7 rig which is hugely successful in Europe, has failed to gain traction elsewhere to any reasonable level.   Hugh Leicester (VP ILCA), Chris Caldecott and I met on the sidelines of the Sail Sydney regatta and Hugh saw the rig first hand.

There is correspondence between ILCA and PSA re the rigs, expressing “excitement”.

Just a side note, at this point the C-rig project had chewed through 28 masts, and 4 sails! It had been sailed by the likes of Tom Burton, Gerard West, Brett Perry and possibly 10 other biggish sailors. What has become known as the Flame Rig photo, the boat is being sailed by Chris Caldecott and the photo was taken by myself, in Chowder Bay Sydney 17th Dec 2015.

In February 2016, Prof Tracy Usher (Pres of ILCA) travelled from San Francisco to Sydney for the day to sail the C8.    Subsequent meeting at the Royal Sheaf hotel with Tracy, Hugh, Chris and myself started to map out a process but at this stage, the Asian issue and the lack of traction of the 4.7 started to come to the fore.

Mid 2016, lead builder started to move from PSA to PSJ, mostly due to the physical stature of the principals.     Chris is 95kgs and a big man, whereas Takao Otani (Owner, MD PSJ) is significantly lighter.

Plus, Takao and I had met in Montreal in 1978 under the watchful eye of the late great Ian Bruce and had become life long friends.    Takao was pivotal in the 49er and 29er programs being a founding partner.   The 29er just would not have happened without Takao, so there was considerable history between the 2 of us.

By late 2016 a complete re-thinking of the smaller stature rig had started and we trialled various breakthroughs, the biggest one was the spliced mast which allowed us to get the Centre of Effort in the right place WRT the CLR which in turn leads to weather helm (or in this case lack of it) without ridiculous mast bend, which leads to longevity and ease of pulling the mainsail up.

By Early 2017, what is now known as the C5 was being sailed out of RSYS, by their junior program and a rolling development program had been put in place in which the rig and the fitting development evolved at a rapid rate.    Nothing quite like arm’s length testing.

There were various meetings between Tracy, Eric, the late Jeff Martin, Takao and myself, mostly at WS conferences.

Early 2018 Takao visited Sydney and sailed the new C5 rig and was very impressed, it was a day of a lot of wind.  (Takao had not seen the C8 so I sailed it) and videos were made, these videos were sent back to Tracy and ILCA and a decision was taken that ILCA should generate (and pay for) a video before the next WS Conference, which was May 2018.

The weather did not co-operate so there were a few attempts but we did get the video to London in May, but it was not shown.   I was overseas at the time, this job fell to my son, Harry.

March 2018, Up Marine and PSJ entered into a formal contractual arrangement WRT the C-Rigs.

Mid 2018 both Tracy and Eric travelled to Sydney to, among other things, see the C5 which again happened at RSYS and the “talking head clips” that you see in the video were done then.

Also mid 2018 the project spun off the 29erC rig that is now being used in China extensively!

One of the C5 rigs was flown to Japan for Takao to test in the local market. That lead to some subtle but significant modifications.

There was a meeting on the sidelines of Sarasota WS Conference between Takao, Tracy, Chris, Jeff, Eric and myself re the introduction of the C5.

By late 2018 ILCA/ALCA had decided that the C5 should be released into a nationwide (Australia) trial.

Ken Hurling (Pres ALCA & VP ILCA) who was already aware of the project embraced this opportunity with both hands, and the minutes of those meetings are in the public space, so I won’t repeat them.

The last 4 months has been chaotic.

We took the decision, that if you are going to have a family of rigs, then you have to actually make them otherwise you have no idea of what pit-falls await you, so we did just that, C8 was relatively easy until we made the decision that all rigs should be of such a length they can be “checked in” as over size luggage on most commercial flights.    C5 & C6 are relatively easy.   C8 is more complicated.

Clive Watts (owner of CST) developed a new technique to “kink” the mandrel in the winding process, so it comes off the machine finished.  Click on image to enlarge.

The rig then went to Davenport, Tasmania to be sailed by as many kids as wanted to, it was flown back, and along with the C6 underwent 5 days of intensive testing and refinement by Takao and myself including Ian MacDiarmid tweaking the sails daily, fitting changes, re-running systems. This all happened Dec 2018.

ILCA wanted the C5 rig with a full specification “suitable for the LCM” so they engaged Clive Humphries (tech officer, ILCA) to generate the whole spec.   Clive travelled to China with Ian to oversee the whole sail making process, he also liaised with Clive Watts about the mast making process and he spoke with me and has a full set of drawings/3d files.

Feb  2018 some parts of the project have been spun off to be used on the 49er- FX rigs post Tokyo!

2 days ago, we (Chris, Ian, Clive Watts and I) put every rig in a Laser and checked the whole process and those 3 rigs, C5, C6 and C8 are on their way to Valencia.

The plan is to produce 100 C5 rigs for Australia over the next 4 months and scatter them across the country with a few leaking into Asia and no doubt to other parts to test the whole process that we have gone through to ensure it is fit for market.

Again, ALCA position, how they plan to do that along with PSA, is in the public domain.

Arms-length testing is critical, we have learnt that time and time again, nothing beats it.

From my POV, the C5 is near perfect in terms of a final product.

The C6, yes I have sailed it, and I have watched Takao sail it, but I have not seen a young 60kg girl/boy sail it.  It has been sailed extensively with glowing reports, but I can’t sign it off unless I see it with my own eyes.     That will happen mid this year maybe, and there will be maybe 5 rigs made.

The C8, in a previous incarnation, I have sailed many times, in everything from 5 – 30 knots, I have tried to break it, I have also capsized it and it’s a lot of fun.     We are not done on the “checked luggage” solution yet, but the rig looks good.   Chris has sailed it and believes it’s “fit for purpose!”.

Again, that will all happen later this year maybe, and there will be maybe 5 rigs made for test.

The feedback from Ken, the analysis of the feedback coming from SM, particularly the interest coming from Asia, in particular for the C5 concept would tell me that Tracy and the ILCA/ALCA have hit the nail right on the head.   This has been a clever, think outside the box, structured plan.

This will always be a situation in flux, and change is always painful, but if done well, it always leads to significant up-side, and if you need any examples of that, the Radial rig is a case in point as is the Carbon rig on the 49er/FX –  both have lead to significant growth in the classes and in the case of the 49er/FX massive reductions in running cost.

It will be a busy year.

Julian Bethwaite

Designer Update to the Carbon Rig for 29er

Update on Carbon Rig for 29er

Std rig and the Mk7 rig in Austria May 2017.

Wednesday, 11 July 2018 – Sydney

Preamble:

November 2017, after spending a considerable amount of time in Asia and Europe looking at the existing rig, I moved several spec changes to resolve “cannoning issues” (topmast moving into the mid-mast, and Mid-mast into the lower mast) in the Alloy mast and these were reviewed by World Sailing and the Class and I believe they are now approved.

First few months of 2018, given the damage to upwards of 52 near new jibs in one day, at the HK Worlds, a new reinforcing design, very similar to what worked so effectively on the 49er, was proposed and I had 2 of these jibs made and they are now in Europe.  We titled them “training jibs” based on the NZ/Aust usage.

April 2018, so they could be discussed during the builders meeting in London May 2018, I proposed several other changes to the Alloy mast again to ensure that with the impending Chinese order and the level of use these boats would get, which is likely to be double or triple anything that anyone has ever subjected a 29er to, they would stand up.  These are all fitting substitution changes, so like for like, just a different manufacturer/source.

May 11th in the WS offices we had our builders meeting and as is customary, towards the end we were joined by the exec of both the I29erCa and I49erCA.     Joan, Barry, Marcus, and David all joined us.

Right at the end of that meeting, questions where asked about the “training jibs” and about the Carbon Mast.

Until this point, from my point of view, carbon masts were off the agenda.

To cut a long story short, I was urged to request a spec change, which I did sitting alongside the President and Exec Sec a few days later at the ensuing World Sailing conference.   Others were going to contribute, but to date, none have.

18th May I was in HK, the topic of the builders meeting came up, the possible position of a new mast and new sails, was brought to light, this was passed onto the commercial partner in the Chinese program and they have enthusiastically endorsed and adopted both the “training jibs” and the new Carbon mast.

20th May, the tech officer of the I29erCA started the “training jib” spec change process, 21st May WS responded.    I don’t know where this is at.

I have painted a “grim” picture of the likelihood of the Carbon Rig’s acceptance by the I29erCA to the Chinese purchasers.  I have been quite explicit on 4 occasions, and 4 times they have come back and confirmed their wish to proceed with their commitment to the Carbon mast.  The last occasion was Tuesday July 10th.   This has now been confirmed in an email.

The way it presently stands, we will be supplying the impending initial Chinese order with upwards of 20 Carbon rigs and 40 “training jibs” to Shenzhen in September 2018.

Because of the Chinese commitment, we presently have orders for another 5 29erCRs outside of China.

Where we are at

Re the Mk7 rig, featured above, is in Arco, Lake Garda in Italy. I took the time to go and have a very good/hard look at this rig on June 30th, several weeks ago, and it’s in remarkably good shape for a rig that has seen 4 years of use across 6-7 countries on 2 continents.    It was not on a boat, but I see no reason why it could not be used at very short notice.

The Mk8 rig is in my front yard in Sydney, it was stepped in a boat a few weeks ago, measured, and it will have sails in under a week which will be tested before going to China as templates for the Chinese order.

Re Helsinki, we have run out of time and given the present climate, neither I nor either rig is likely to make either meeting of the WC or Exc at the Europeans.

The differences between the Mk7 and Mk8 rigs are very minor (see the back page).  The Mk7 rig is approx. 140mm taller than a std rig and has a semi squarehead/pin head mainsail profile.    The Mk8 rig is only 75mm taller than the std rig and has a full squarehead mainsail profile approx. 750mm in width which is very similar to a 49er in luff-length to head length ratio.    Based on everything Ian Macdiarmid (the sailmaker) and I know, the 29erCr will behave like a 49er rig, less like an 18teen/FX rig.

As for the rest of the measurement WRT the Mk8 rig, Goosenecks [GN] are the same position on all the rigs, the rest, in most cases 100mm higher than the std rig, 20-30mm lower than the Mk7.

Standard jib sits on the MK8 mast, the clew rises 2-3mm. The standard spin also flies off all the Mk8 Mast, you just want to tie a knot in the halyard 100-120mm down to get the correct flying shape.

The reason the forestay is higher on the Mk8 rig, along with the shrouds, is it’s the only way to get the mast to behave correctly.   That is also the reason for the introduction of the D1’s which go through the vang GN, (photo front/back page) no extra holes and the D1 is made of rope/spectra/dyneema.   The reason for that is that square heads need greater control over the lower mast and rope D1 is a very effective and inexpensive way to do it.  The 49er experience is you almost never move the D1’s, they are very much set and forget, so on the 29er they are simply anchored via a sliding splice to the existing chainplate adjuster.

Rope is also far gentler on the body.

With the rig, I have taken a comprehensive approach, so I have looked at everything above the gunwale.   Hence spectra D1’s etc.  We became aware if we re-model the boom section, using slightly increased wall thickness, ensuring continuous curvature would lead to a reduction of the price to 1/3 of the existing section, also losing 20% of the weight and almost no strength.    We have “borrowed” this technology from other projects like the c5 Laser rig.  (it is a c5/c8 Laser boom).  Other similarly borrowed technology includes a vastly simplified ram vang system.   One of these changes is that just about no one adjusts the outhaul, so we will couple that to the vang, pull the vang on, outhaul also comes on, let it (the vang) go, outhaul eases.

But, given shortness of time, we are cutting up perfectly good 49er spreaders to make 29erCR spreaders, very expensive way to do business.   We obviously expect given the fullness of time, the cost of these will drop significantly.

And we intend to borrow from the Laser class (similarly the 49er class is likely to adopt) a “compliance model”, which means we set a standard of compliance, very tight and anyone who can prove they can make a component to that standard is given a license to produce.

I will touch more on this later re costing.

Weight of the standard rig is 10.4kgs, Mk7 rig is 7.8kgs, Mk8 rig is expected to be about 7.2kgs.

Re reports and data, there are about 400 pages of written reports on the rig going back 8-10 years.   Then there is a plethora of data records.

Possibly the best compiled document is the thesis by Gottfried Gerhard Klampher, from the Uni of Vienna, Austria, which is in the public domain, completed earlier this year.  On the following pages I have referenced the key graphs, but the thesis is worth the read regardless.   It’s about 80 pages.

Above is the boat going to windward, the top graph is the unfiltered data, the lower graph is the same data but with significant dampening so as to generate a trend.

It’s very early days, and the new rig is not that well known, but the overriding thing which shows through is that the new rig is not so much faster but it’s a lot smoother, it’s easier to sail and the boat doesn’t slow down anywhere near as much.

If you look at the top graphs, time and time again both boats drop in speed, but the carbon rig boat drops less and recovers sooner and more than the current standard rig.

The wind in both these set of graphs is approx. 10-12 kts and the more consistent speed is common   across most wind strengths.

The 2 boats were within 10-20m of each other when this data was collected.

Below the upper graph is going to windward, the bottom graph is coming downwind.

Same wind as previous graphs.  Boats again were within 10-20m of each other (except the tack).

These are TWA’s (True Wind Angles)

Upwind, in the steadier starboard tack, both at the beginning and at the end of the graph, the Carbon rig holds a far steadier and higher AWA than the standard.

Downwind is more telling, the Carbon rig’s VMG is markedly better, both gybes.

 

The following is an attempt to pre-empt questions.

Why extra length of the mast and extra area?

Because if we do nothing, just switch the mast, we know the crew weight will drop approx. double/triple the reduction in rig weight.    This is true regardless of whether it’s an I14, 5o5, FD, 49er, Moth, B14, Cherub or a 29er.    It’s a very simple sum to increase the area and the “arm” (length of the mast) to restore the weight.   See the email towards the end of this document.

Why a square head?

If we had 1 million years to evolve the rig, then we would closely approximate those that have been at it for 1 million years, the birds and fish.     But we are mere mortals and we are not that good, so we try to approximate an ellipse (Spitfire wing tip or the wing tip of a 787 or A350).   Our material science is still primitive, and people bounce mast heads on the ground, so the top of the mast is bigger than it needs to be, it is simply not flexible enough to do a really good job, plus it’s heavy.  So, we start trimming the mast height back, we “truncate” the rig, we end up with a square head, and if it’s done well, we can achieve something special. A very elegant solution especially for all sailors.    For those just coming to grips with the 29er, it’s easier and it also allows those with experience to push the rig further into places they would not normally go and have fun safely.

Why Carbon?

Materials have changed, carbon is getting increasingly cost effective, particularly with respect to longevity.   The biggest advantage is environmental and cost effectiveness with time.    When you buy a 2nd hand boat, with a carbon rig, it’s almost impossible to “buy a lemon”.

Alloy yields every time you bend it, does not matter which alloy or what industry, which is why most aircraft must be retired after X number of cycles.    Well-designed carbon structures do not.

Carbon is smaller and lighter and the rig is ready.

Need to touch on inertia, it’s possibly the seminal point.   Sure, the rig is 3-4 kgs lighter, and in itself, that weight difference is important and real, but once you turn that into inertia, it becomes significant.

When you apply the inertia rule to all the other carbon rigs out there, it explains just about everything we empirically observe. That plus the air-dam factor, it all starts to make sense.

So what’s inertia?  You’re driving down the road, a cat runs across, you slam on the brakes, and you lurch forward into the seat belts, that movement forward is inertia.

Inertia is a X² law.

I know that the 3 Carbon sections of the Mk8 mast weigh 4.8kgs.

Therefore the “bits” – wires, spreaders, ropes fittings – weigh 2.2 to 2.4 kgs.

So the alloy/FRP section of the alloy mast weighs 7.8kgs, approx.

Reason for the maths is there is a simple way to do this sum and a complex, I like it simple.

The bits are constant, the height of the bits, the sail, so if we just look at the X² of the sections then we have 8² = 64 and we have 5² = 25 (I’m not good at SI units but I’m guessing this is Newtons).

Doing it the more complex way, include the whole mast, wire, ropes and bits, so the whole Mk8 mast weighs 7.2² = 51.8 & std mast weighs 10.4² = 108.16, we can add the sail, but it’s still <½ the inertia.

Call it Newton’s, whatever you like, the carbon rig has ½ the inertia of the alloy rig.

And yes, all sorts of exceptions and rules are being broken, the hull weight is in there, and the mass of the crew etc, but comparing apples with apples, it’s ½.

What does that mean?  When you go through a gust-lull sequence, and the rig starts heeling and then coming back upright, the amount of energy to stop the rig’s inertia is significantly less with the carbon mast than it is with the alloy mast.   This is sometimes referred to as “radius of gyration”.

Put an 8kg lump of lead on the end of a 3m pole and hold it with one hand, upright and walk about. Now the same pole but with 5 kgs of lead, walk about.   This is exactly what we are talking about.

The 2nd thing is air-dam, or it’s occasionally called a flipper-head.

Go get the bit of cardboard off the back of an A4 pad, curve it a bit and drive down the road at 35kph (7knts BS + 12knts WS = about 17knts AWS.  1knt = .55m/s = 2kph, so 17knts = approx. 35kph) and stick the bit of cardboard out the window and fly it.   Now rip ½ the top corner off approx. 45° and do it again. It becomes very obvious that the square head bit of cardboard generates more resistance.

Go from cardboard to Mylar, get particular about the “trigger” point of the #1 batten (known as Euler crippling (or buckling) load [ECL]) and what happens is that the whole inertia thing (due to the reduction in weight) is enhanced quite dramatically by the air-dam of the squarehead.

The net effect is you’re a young gun, silver fleet, out at the top of your range and you get hit by a gust, even before you ease the sheet or luff, the load in the leach goes up exponentially (it’s also an X² law) and the compression in that top batten goes up also as a factor probably in excess of X².

First thing that happens is the mainsail flattens off, right at the head where the most amount of righting moment (heeling) happens.    And normally that is enough, but if it’s a big gust, then as the load continues to increase, almost regardless of mainsheet tension it will continue to de-power and may even “trip” to leeward (if you exceed ECL).  If you’re skilled on the mainsheet this whole process is enhanced, and the trigger point can be set via vang and/or downhaul tension.     If you’re in the upper level of the weight range you keep the mainsheet on longer, then start using the vang, delay downhaul.  And if you’re light, you come down harder on the downhaul earlier, start easing sheet while drumming on the vang.

Then as the gust goes away, the reverse happens, if it has “tripped” (1st batten) it pops back, and powers up, faster than you can squeeze the mainsheet on.

The net effect is the boat becomes far easier to sail, with a wider weight range and it simply does not slow down nearly as much as the pin-head rig which the boat presently has.

So yes, simply pulling 3-4 kgs out of the system lightens the boat, there is less drag, but that’s really only a 1 – 1.5% impact on the overall weight of the boat, and that = faster and/or higher, but the big difference is the boat is far more easily driven, so it just does not slow down as much and it’s that much more fun and that much easier to sail!

Supply of carbon fibre (i.e. shortages).

Fourteen 787 aircraft are made a month, the whole plane weighs 120 tonnes (empty) and approx. a quarter of that is Carbon.

So that’s a little over 4,000 tonnes of carbon a month and we have not even started with A380’s, A350’s, military, medical, automotive and even the humble phone cases.

We are talking about using maybe a 1-2 tonnes of carbon a year with the 29erCR and the likelihood of there being a shortage of supply that will impact the sailing world is miniscule.

Booms

Both boom and vang systems can be used with either rig, you just have to switch out what we call the knuckle, and it can be switched back later.   We will make a “special” knuckle so existing booms/vangs can be used with the Carbon mast.   We can supply it with the rig at no extra cost.

The knuckle used on the 29erCR is the same one used on the existing 49er rig.

Other Developments

Some of you will have heard about the c5 Rig on the Laser, there is also a c6 and c8 rig.    Prof Tracy Usher, the Pres of the ILCA has been recently quoted as saying “we don’t see white sails and alloy masts in our future”.

The c5 Rig borrows most of its technology from other developments, across a range of classes, this is ongoing evolution.  All that being said, the Mk7 rig is still relevant, 4 years on.    The Mk8 rig will be a refinement of the Mk7 and it will be equally relevant for the foreseeable future.

The Mk 8 rig borrows technology from a wide range of sources, some unexpected and some more logical.  It cuts both ways.   The 49er class is presently undergoing a rig refinement process, including the “compliance model”.  I am working with Southern Spars initially, a lot of the development work that has been trialled for 4 years on the Mk7 will find its way back onto the 49er in the next iteration.  And that in turn will refine and improve the Mk8 rig, the c5, 6 & 8rigs and so on and so on.

The jib and the spinnaker need not change.   There is almost no need to change the jib beyond the ongoing spec change, the “training jib”, to include the zipper and extra reinforcing.   That is going to happen anyway and it may well be cheaper (zippers are cheaper than hanks).

There is an argument to change the spinnaker, it’s an 18 year old design, and if the spec change is unsuccessful, that may well happen quite quickly.

Logistics

The existing 29er mast in NZ is the most cost effective because it does not have to be transported around the world.  All the raw components of the mast come from NZ.  The most expensive place is the USA, because the components have travelled 3/4’s of the globe just getting there (and NZ have the most expensive complete boats because the hulls have to be imported from the UK, as a result, they are about to start building in NZ again so this will change, it’s just a question of logistics).

The Laser based compliance model which is already in place with the new Laser carbon topmast, we believe will result in Ovington sourcing more 29er parts in Europe, Zou Marine producing parts in Northern China all compliant, etc, all within a very tight band of tolerance and all cost effective.

It will also allow manufacturers to “pick and choose” where they purchase parts from, so shortages will be a thing of the past and this process will also transparently drive costs down.

But there is no way around the fact that to produce 3 carbon tubes is more expensive than extruding 2 bits of alloy with multiple sleeves, (& a FRP Tip) but by designing everything in, so there are no extra bits to be added on, we have cut the rigging time by more than ½ and we have increased reliability and repeatability dramatically.

This could be called the Ikea model, that being, because there are no sleeves, the 3 sections are tracked and fully machined, they are 100% complete, to the same spec pattern, it can be assembled with an Allen key in about 3 hrs by anyone, coaches, sailors or parents, so it’s bolt together, much like Ikea furniture.    It also means that we can supply every bit in its simplest and therefore at the least cost to the end user.   Think spares!  We can also adopt an Amazon supply model, so if for whatever reason a part can’t be obtained in San Francisco, it could be FedEx-ed over night from HK (or UK or Qingdao) so you can go sailing on the weekend.

Re introduction

Firstly, it simply can’t happen before September 2019.    The planned (and they are very good at it) ramp up of Chinese demand would suggest we will be “many” 29erCRs in China by then, and for me to manage that and worldwide demand is just not going to happen.    The up-side is we will have a near perfect supply system in place, initially out of HK/Shenzhen and operating in a “closed’ market like China, all the bugs will get ironed out before the rig goes world-wide.

The experience of the 49er class with a far more expensive “switch cost” was that over 450 complete rigs were ordered within the first 9 months and that was over 10 years ago.    It sent Southern Spars into a tail spin that we are only now sorting out properly.  The bugs had to be fixed on a global scale.

Those people buying a new boat in Europe, it will be a few % more expensive (the rig is about 1/3 of the cost).

Those in NZ will hurt the most, about 5% more (until they start building again).

Those in USA will be marginally better off, those in the UK, a few % better off.  AUS, no change.

In the event we can plan, and consolidate orders, prior to acceptance, then there is every likelihood that those bonafide sailors with existing rigs could get a 10% bulk order discount for 5 or more rigs.

The difference between what is being proposed here is what was stated above, there is likely to be quite a lot of 29erCR rigs in China by the time we adopt this, so the ramp up can be far more efficient!

At the end of the day

The really big winner in all of this is the boy or girl who buys a 2-3 year-old boat.   Other than a bit of TLC, some spit and polish to make it shine, they can go and play hard knowing that the mid-mast has not gone soft, that the top-mast has not “got tired” and the lower mast is not “kinked”.    As I said before, near impossible to buy a lemon with a carbon rig.

Mum and Dad will also be the big winners, no more coaches telling them they need a new mast, the mainsails won’t be stretched from pillar to post, they will last longer also.

It’s a simple empirical fact, we are selling a lot more 49ers these days, and the number of topmasts being sold is a shadow on its former volume, post the carbon rig.   That’s a simple fact and easily checked.

And the rock-star will have a rig that will set him/her up for his/her progression to the FX or the 49er or anyone of the other hi-end boats, even yachts, and he/she will have a ball doing it.

Have a great meeting.

Julian Bethwaite

~~~~~~~~~~~~~~~~~~~~

The following is an email that explains the workings on the next page, a few have asked how did I get there.   It’s very simplistic, but its backed by more complex calculations.   Maka = Ian MacDiarmid

From: Julian Bethwaite [mailto:julian.bethwaite@upmarine.com]
Sent: Wednesday, May 30, 2018 3:57 PM
To: Ian Macdiarmid ; Joan Mollerus ; JOHNSON Barry ; Chris Turner ; Carlos Debeltran ; John Clinton ; Mark Paul
Subject: 29erCR mainsail

Hi all,

Just had a phone call with Maka, we are very short on time WRT getting a main done in time for Helsinki, so I have just spent a few hours doing some maths and working this all out.

Barry, you will need this for the Spec-change.

Just keeping it as simple as possible.

The new CRig will be about 3 – 3.5kgs lighter.

History tells us, that if you do that, you lose about double that in crew weight.

So if we do nothing, crew weight will go from (and here you have to pick a number) 130kgs to 123kgs, or 5.4%.

If you take the existing UW sail area, (12.41m²) and factor that up by 5.4% you end up at 13.116m².

Take the jib away, because that’s not changing, you end up at 9.35m².    And then factor that back by the increase in arm of the mainsail, from 3.35m to 3.5m or 95% and you end up with a target mainsail area of 8.9m².

That’s the simple maths, I actually put this into a far more elaborate formula that my father and I have used for years, using radians, and lbs/ft, etc, and the sum is almost the same.   So I am moderately confident.

We can’t get there without increasing the mast height 50mm, and even still the headboard length is becoming quite long, up around 38% and I don’t want it any longer (FX is 42%, 49er is 28%).

We may use an end-plate on the mainsail to extend the weight range further up, without hurting the lower range, but that will be a suck it and see exercise.

Maka, if you want a more detailed DWG with lots and lots of measurements, I can do that.     Also, I have no doubt that other programs will measure things differently but I am measuring like for like, so it’s all relative.

JB

Red = existing standard rig, yellow = Mk7, blue = Mk8

The cuff at the bottom will be enlarged based on the experience of our testing and the AC and A-Class cats development.    The rig will very likely have winglets also, again from our testing.

Boom Gooseneck with vang sheave incorporated, similar to 49er system

Masthead fitting with GoPro mounts front and back, bigger sheave, M6 axle, and track capture

Mast gooseneck, bolt on with Allen key, radius slot at top to accept rope D1, 2 holes at bottom for exit of halyard, again radiused so as to act as low friction ring.  Grooves in base increase glueing surface area.

Square head vs pin head rigs

Square heads have been around for thousands of years, Vikings and the sails they had on their long boats, and I’m sure the Polynesians and their Proa’s preceded that also.

The Dhow Rigs are equally as old, “leg of Mutton Rigs”, formed into the original “Bermuda Rigs” in the 17th and 18th centuries.    Then came “Gaff Rigs”.

What I refer to as a Pin Head rig is really a Marconi Rig, developed mostly in Germany at the beginning of the 20th century.  Most notably “triangular sails”.  Manfred Curry in his 1946 book shows lots of photos dating back to 1935 of his father’s boats, and those boats had developed significant “roach” (curvature in the leach of the sail supported by the battens) and a level of mast bend.

I will now skip 50 years of development and I acknowledge that this is a great dis-service to many developers including my father.

In 1981, I tried and sailed a 2-handed 18 foot skiff (Prime).  Over the next 3 years that developed and what became apparent was with only 2 people, you simply did not have enough hands to do everything, so we needed to make the rigs automatic.


2-handed Prime 18ft skiff

The development happened at an extraordinary rate, 10 years later a GRP 18teen with a few carbon straps (to hold the mast), went around the std NE course in Sydney Harbour in under 50mins.   The “straight line” distance is 15.5nm, it was a heat of the World Championship, 3 windward legs, 2 downwind legs around the island, 1 straight to the bottom, not too many gybes, but plenty of tacks.

Sure, it was a highly refined boat, many aspects of it were honed but the biggest contributing factor was a highly developed “pin head” rig!    That record time still stands today and not even foiling Moths or MC32s can come close to it.

I doubt a square headed boat will ever be able to achieve that sort of time for a few years to come.

So, the very refined “pin head” rig was a bit of mathematical poetry.

First issue was the way the mast bent, biggest contributing factor was the height of the hounds, and altering this 20-40mm (in a 10-11m mast) made considerable difference to the point where there were 2-3 keyways (attachment points) for the forestay that could be selected depending on conditions.    We always tried to get an “exponential” bend, so the lower sections (alloy tube) bend far less than the upper mast (GRP wound tube).   We developed a whole system of % and depth to define this bend, and we would alter it by 0.5% occasionally.

Once we knew the luff curve of the mainsail, and the rate at which it would bend under different loads we then designed the roach of the sail.      They had to match, and there was again a very definite multiple, so if say there was 222mm of luff curve, we would have 222 x (say) 3 = 666mm of roach at that height in the sail.

 

© Sport the library/Jeff Crow
Sailing-18ft, Hayman Island 1993
AAMI/Mast Mount
1993-0010-8621-157

So why am I going into such detail?

Because of the analogy of a gust, and what do we want to happen in that gust.

Your standard gust lasts 9-12 seconds, it increases the wind speed on average by 25-30%.   So, if the mean wind is 10kts, then the gust is likely to be 13kts, and in 99.99% of cases, it will be skewed 3-5° off the mean wind direction.   The reason for that is it comes down from the layer or 2-3 layers above, and almost by definition those upper layers are screwed by Coriolis, so they are at different angles to the lower layer of wind.

But the most import thing about a gust is 80-85% of the energy is in the first 0.5-1sec.

You’re sailing in 10 kts, fully powered up, gust hits at 13 kts. Force goes up by X² so it goes from a nominal level of 100 to something approaching 169, and it happens in under 1 sec.    Do nothing you capsize, simple.    If you’re good and you can see it, you luff a little, and your sheet hand prepares to ease the sheet.   Get it wrong, you capsize.

With an automatic pin head rig, because the load increases, the mast bends more, and it bends more at the top than at the bottom.  If you have the roach right, then it progressively flattens at the head more than it does at the foot, so the CoE automatically drops, increasing your Righting Moment, and that in turn helps to “resist” the increase in force and again this all happens in under 1 sec.

The other side of the gust, the automatic rig also powers straight back up, long before even the fastest human being can tension the mainsheet.

By the time we got to 1993 and the AAMI 18teen foot skiffs, we had it, so you were actually pulling the mainsheet on in the gust, which meant the rig automatically flattened even more in the gust, which led to much higher pointing angles, and acceleration.

The “pin head” rig theoretically closely approximates an ellipse, therefore as you move towards the tip, the span-wise “pressure” loading drops and you minimise tip losses, vortices and the like.   If we were as good as the birds, we could probably effectively end plate with all the aspect ratio benefits that brings.

But we are nowhere and will never be as good as nature and the birds!

The first time I saw a square head rig was in the late 80’s.   Chris Cairns’ loft was upstairs from our factory and he was using the square head to try and emulate what we had with the pin head rig but on a Tornado which at the time had a tree trunk of an alloy rotating section mast.

It would not bend, so he used the bias of the sail cloth and the square head to emulate the head de-powering benefits of the pin head.  It was very clever, and it required some quite extraordinary detail in rocking the head panels to get the desired result.   We still do this today in the 49er mainsail.

With the advent of carbon masts, the ground rules changed.   The UTS (Ultimate Tensile Strength) of carbon and glass are in fact quite similar.  What is different is elongation to break.    Glass, if laminated, with epoxy or vinyl-ester is 5-7%, good Carbon is 1%.    It’s just a whole lot stiffer.   If you are looking for a mast to bend consistently at 4-5% and you’re using carbon as your base material, you either need to thin down the wall thickness or reduce the diameter.    But the overwhelming reason for using carbon is weight.   The base tube weight is approximately ½ that of its alloy counterpart and ¾ of the weight of the GRP topmasts.   And now, with advances in building techniques the cost is coming right down.  In 5 years’ time, any relevant class will have a carbon mast.

Thin wall tubes are fragile, so in 90% of the cases in the marine mast business diameter has dropped 15-30%, wall thickness has gone up from around 1.7mm to 2.2-2.5mm and this new breed of carbon mast is now extraordinarily tough and light with huge longevity.

But, the topmast simply does not like to bend anything like the old GRP topmast.

At the same time material science has evolved so that the Mylars used in sails have similarly advanced, and the extent to which you can dial in bias, warp and weft is simple and common place, especially if you are buying 1000’s of meters for classes like the 49er.

What we now do is design the bias stretch, we rock the head panels so we get the warp/weft aligned exactly and then complement that with the bend of the carbon mast to achieve something approximating the sort of automatic gust response of the pin head rig.

There is a lot of science to this.   The biggest contributing factor is the length of the square head.   Most sailmakers like excessive squarehead length.   Our experience of the 49er and FX sail plans, is that if you go too big, you lose “range” and the ability to alter the shape beyond a rudimentary level.    In the 18teens which are even more extreme than the FX, this has become very niche, they are fast in one setting and they sail the boats, so they are in that setting as often as possible.

This is not necessarily a bad thing, it’s evolution, and that process has many years to run.

If you get it right, then you may also endplate the top of the sail effectively, and that leads to Aspect Ratio benefits and considerable changes to CoD and CoE considerations.

Going back to the 18teens, they are pursuing this now extensively with mast head battens that are not too dissimilar to a 787-wing tip which when all is said and done, are copies of birds, think cranes at altitude in gliding flight.

We still have a long way to go, it will get refined further over the next 5-10 years.

It’s been 25 years since we put a cuff on the bottom of a 49er main, that is still surprising us as to its effects, square-heads will be a longer road yet again.

Julian Bethwaite
November 2017

The 29er Carbon Rig

History

This is the 5th or 6th carbon rig built for the 29er.  The first one was 45mm OD (outside diameter) mast approx. 200mm longer than the existing rig.

The second one was a variation on the first, but an increase in OD to make it more “friendly”!

There are also 2-3 rigs in NZ but neither would appear to be acceptable.

This one (the photo above taken in Austria) was a complete re-design based on the previous information. OD is 55mm. It’s an Australian CST rig, it was taken to Medemblik last year to be shown at the worlds, and at this stage it had already been sailed in Australia for over a year.

It’s a 2-piece mast, the joint is about at the spreaders, it has carbon spreaders, rigging is near identical to a standard rig other than the hounds are approx. 100mm higher and it has a set of 6mm Dyneema D1’s. Spinnaker hoist is also about 100mm higher. (This is a function of D1’s.)

Why D1’s? It’s a function of the square head, if you are going to use a square head, then you need to control the lower mast to a greater extent than any amount of stiffening the lower mast can be given via laminate modification.

Why Dyneema D1’s? Because wire is pretty brutal! It’s also remarkably cost effective and we have purpose designed the gooseneck fitting to resolve all the loads. Adjustment is via a sliding splice!

Why a square head? Very probably 3 key reasons:

a) If you go to a Carbon rig, then the weight of the tubes drops to approximately ½ that of a comparable alloy rig. But given that the tubes are only approx. ½ the total weight, in that the wires and halyards are the other contributing factor, the total weight drops by 1/3 – 1/4. But the weight is lower!  If you do nothing, then that reduction in weight will lead to a reduction in crew weight. There are a number of ways to counter this, one is to increase sail area, and you can do that by increasing hoist of the main, or by employing a square head.

b) Given that longevity of the rig is a key reason for the change, to achieve the sort of longevity that the 49er is currently enjoying, we exploit the “elastic yield” of both the mast and the sail cloth. So, what that means is we allow both the mast and sail to yield in a controlled and repeatable manner that does not exceed either’s elastic limit (once you exceed you do permanent damage). Presently the alloy rig exceeds its elastic limit every time you go sailing, same as an aeroplane, it’s only good for so many cycles. With the 49er, the mast would appear ageless, in that the likes of Outteridge and Burling were using 5 year old rigs in Rio.

c) There are considerable efficiencies from a square head if done correctly. There are also significant benefits WRT handling, that can be derived and this is bearing out in Austria presently. And I quote:

“What I can say in general is that it behaves a lot smoother than the old one especially in gusts and lulls…”
&
“The main is awesome… it feels really great and behaves really well”
&
“What I have to say is that the new one is quite a bit faster than the old one…as you can keep pressure longer in the sails (square top)”

All this is borne out via the data we are gathering also, it would appear that the new rig is much easier to sail (we also found this in the 49er) so it’s not faster, per say, but it just does not slow down, it’s far more forgiving, and that’s what we targeted.

A final point, when I originally designed the boat, I was pressed by the late Dave Ovington to go bigger and bigger in the jib. Probably went too far, so in part, the increase in mainsail area re-addresses this imbalance, and is one of the reasons the boat is now more balanced!

Where are we at now

Attached is one of the data files from Austria.  Brown is Carbon, Blue is Std. Wind is from the top left.

The rig has been around now for 2 years, for the first 18 months that rig was used extensively in Australia, UK, Holland, Finland, France, Germany and though a condition of use was that we received feedback, not an iota was ever received.

Pretty disappointing actually given the money and resources that had been poured into it!

The rig is now in Austria, being sailed against a standard rig, with crews swapping and generally good investigative protocols being brought to bear, it will be the subject of a Thesis/Masters.

Upside is we are now getting weekly feedback, not just words but hard data that can be analysed and some serious decision making can happen.

All this ends July 12th when the rig will be taken to Lake Garda, probably sailed a few more times and then be put on the “Rack” at Arco under the watchful eye of Nautivela, and for anyone who wishes to charter a 29er with a carbon mast, have a go!

Where to next

I am waiting for all the information I can get out of Austria, so nothing is going to happen for a month.

Chris Turner of Ovington Boats has ordered a whole new rig, so this will be a new 3-piece mast, new mainsail, new jib and new spinnaker & a new boom fit-out!

3-piece mast is critical because of logistics, you can ship anything under 3m easily! Probably 50-55mm OD, we need to do the maths, integrated sleeves, etc etc.

New main is obvious, square head.

Jib, no real change, other than we will probably opt for a zipper luff.

Spinnaker, likely to be 100mm longer in the luff, and 50-70mm shorter in the foot to compensate so the area remains the same, but given that the new breed of crews are driving the boat harder and faster it’s only a matter of time before we start over running the spinnaker (same thing happened in the 49er). We could easily end up with a spinnaker ½ m² smaller and a tad flatter, shorter % luff.

We will also take the opportunity to up-date the fittings, the ram vang will still work the same, but with a 49er style Gooseneck, issues like falling off will be gone, it will be much simpler to rig, and much neater, same goes for a significant part of the fit-out, no function change, but fitting lay-out yes!

That rig will probably get to UK in the Autumn, and what happens with it then is up to Chris.

If and when it’s ever adopted by the class is up to the ICA, TMH & WS.

I have done my bit.

I have some other projects that need my attention!

Jb

Forthcoming changes to the 29er

Being immersed in 29ers via Asia and southern central Europe and forecasting the boat’s use in 3, 4 and 5 years down the track, I would like to propose the following changes.

Three issues are affecting the long-term use of the 29er, and those are:

#1 – the cannoning of the mast sections into each other, under ever increasing rig tensions

#2 – switching to a new 49er style gooseneck should be a foregone conclusion and is just housekeeping, we should have done this years ago, but put it off so it was done at the same time as the carbon mast which obviously isn’t going to happen anytime soon

#3 – the deterioration of the watertight seal of the scuppers particularly in the Asian environment but is also now starting to show itself in southern USA & northern Australia

In detail.

#1 Cannoning of the mast joints.   This is the movement of the top-mast downwards into the mid-mast and the mid-mast into the lower mast, under increasing rig tension loads, in part because the boat is being pushed harder by the latest generation of sailors and in part because of the introduction of the turnbuckles, again because the boat is now being sailed by a more determined group.

Simply, the existing array of bolts and “spreader bars” are not sufficient.

Mid-mast into lower-mast is by far the simplest, there is already a sleeve there to anchor the spreader, we just need to increase the number of M6 MT (metal-thread) bolts by 50%.   Better still if we use CSK (countersunk) heads on the additional bolts as these will spread the load onto the 1.71mm wall of the lower-mast more effectively.

In detail, the internal sleeve that is used to anchor the spreader and secure the mid-mast and lower-mast together would be lifted 20 mm, and secured as it is presently.   The spreader would still be attached in exactly the same way and in addition to that in-line with the bolts attaching the spreader, approx. 20mm above the spreader we would add 2 x M6 MT CSK bolts going from the lower-mast, through the mid-mast and into the sleeve.   They would be approx. 10mm in length.

The top-mast into the mid-mast on closer examination is a little more complex.   There are 2 movements.    1st is the securing of the existing sleeve into the FRP top-mast.  Because it flexes, the existing sleeve moves inside the FRP laminate, there is nothing holding it (the sleeve) hard against the inside wall of the FRP, hence my comments above about going to a t-ball for the trapeze wires.

I have considered approximately 6 different options to secure the sleeve, and in terms of retro fitting and in terms of going forward, switching to the use of a t-ball and key plate I believe is the best solution.

By switching to a key-plate anchor, you have 4 x M5 rivets holding the alloy sleeve hard against the FRP tube.    We know that 4 x M5 rivets is enough to withstand about 4 tonnes which is more than you can ever subject a 29er to. Retro fitting, the ID of a Keyplate is 8-10 mm, the hole is 8-10mm, it is accessible from the joint, it can be done easily.   Even just adding 4 x M5 rivets approximating the position of a key plate above and below the existing spreader bar would dramatically alter the structural integrity of the sleeve/FRP joint.

T-balls are well known, simple, cheap, there could be even a negative (as in cheaper) cost consequence of the change.

Once you secure the sleeve into the FRP, then adding 2 x M6 MT CSK bolt, in nearly exactly the same way as I am suggesting we do at the Mid-mast/Lower-mast interface should take the structural integrity of the joint above the critical level and arrest the movement.

#2 Adoption of a 49er style gooseneck.    The kids are driving the boats harder, there are tell-tale signs of stress at the front of the boom. And the biggest bug-bear of the vang shoe falling off, especially in older boats, simply goes away.    6mm pin, it’s simply “fit for purpose”!


Proposed 29er gooseneck


Current 49er boom gooseneck, proposed for 29er boom

I would also seek to use grommets for the mainsheet blocks as people are moving to lash on blocks and the grommets are far more structurally sound.    They are already used on the Tasar boom which uses the 29er section and it has stopped their boom breakage problems.


Proposed 29er boom grommet

Sourcing parts direct from source will also be refined.    The alloy for instance could be milled at source in NZ, reducing weight, length, so enhancing logistics, and dramatically enhancing replacement options and the one-design nature of the boat.       We have already done this as a test with the 49er boom, reduced rigging time by 75% with the obvious reductions in costs.

Finally, it will be my intention to use the appropriate “fastenings” where needed.   If we go for T-Ball/KeyPlate trapeze then it is appropriate to use rivets.    In a lot of other places, it is appropriate to use MT’s.     This has to do with access (or rather lack of access) to riveters in many parts of the world.

#3 Scuppers.    Recently we replaced the post moulding screw on foot-rails with moulded in foot-rails.   The rationale was simple, that the screw on foot-rail was the source of many leaks, they were a source of on-going maintenance and a major cost to install and to warranty.

The resulting moulded in foot-rails do exactly the same job, but simply do it so much better.

Until early this year, we believed we had overcome all the major issues surrounding the scuppers, the switch to MMA adhesive, new mouldings, etc, gave us great hope.

No question they are better, but they are still not perfect.

In humid tropical climates, we are still getting rot quite quickly and even in LA, a 3 year old boat required complete replacement of the scuppers.

Therefore, I intend to replace the scuppers with a trench.

The similarities with the foot-rails are near identical, rather than post fitting, it’s moulded in, and the financial benefits (savings) are far greater with the trench than the post-fitted footrails.

It will do exactly the same thing.   And by my calculations at near exactly the same rate.

In detail, directly under the top rudder gudgeon, we would mould a trench from the top of the transom bulkhead, down to the top of the cockpit floor.  It would be approximately 60mm wide at the cockpit floor (+/-30 mm per side), growing to approximately 70-75mm wide under the top gudgeon plate (draw angle).    Basically, where the World Sailing hull number plaque is presently placed.     There would be suitable radiusing of the corners, etc.  We would also “let in” the new alloy top rudder gudgeon (see below) so the depth of the rudder stock does not alter.

We would replace the 2mm thick SS top gudgeon plate with 6mm Alloy plate and secure it with 2 x M8 MT CSK bolts each side (this is exactly the same sort of plate that we use on the SKUD).


Proposed trench at stern, looking aft


Proposed trench at stern, looking forward

There would be no changes to the angle of the rudder, the rudder stock or the placement of the drain bung, as the bottom of this trench is about 50mm above the transom flange.

The result will be no rot to speak off, no leaks, nothing to work itself loose.

Longer term, considerable cost savings, as there is no 2nd fitting, there are no 2nd mouldings.    The only fitting change is you screw down an alloy plate rather than a stainless plate.

These changes will be open for discussion at the LA World Championships 2017.

Julian Bethwaite
10 June 2017

Hull Shape Considerations

By Julian Bethwaite

A very interesting conversation developed on Sailing Anarchy week or so back and it has had me think about what is planing upwind, why can some boats do it and others can’t, even though they have similar righting moment (RM), and to a lesser extent, as we have just gone through a re-tooling process, what are acceptable variations to a one design concept.

It’s a biggish topic, but all inter-tangled because I’m not quite sure people get it.

I come back to the fundamental issue which is – what is the biggest difference between air and water?    Both are fluids and most naval architects would have you believe they’re similar.  Why?  Because most research has been done on wings and fuselages of aircraft.  A few % points difference in Coefficient of Lift or Coefficient of Drag makes a huge difference to fuel burn, so it’s worth investing $b in research because the savings are worth $b’s.   Whereas, the sum with respect to a sea-freighter, it’s still important, but a few % difference gets negated by how much cargo can be carried.

Air is compressible whereas water is not.

This even affects the car industry where water in the cylinders can bend crankshafts.

So when it comes to boats that are going to plane upwind, as compared to a boat that does not, mm’s count.

Going back to Sailing Anarchy, the argument centred around what was planing upwind?  Crack any boat off say 30° and spring the sheets, and within reason, most boats will plane.  Technically they are going upwind so they are planing upwind.

But the more meaningful definition to me and I believe to the assembled multitude on Sailing Anarchy was a boat that can plane upwind achieves a meaningful higher VMG than they would have had they remained displacement sailing and pointing.

So a couple of definitions:

RM = Righting Moment.  How far you move the crew weight and how much weight you move sideways from the CoB (Centre of Buoyancy)

hull-shape-diag2Righting Moment and Sail Carrying Power – click on diagram to enlarge

VMG = Velocity Made Good.   Very few sail driven boats can sail straight into the wind (a few with blades can, but most would consider those boats “out there”, and they are pretty slow) so you need to tack.  If you assume 45° tacking angle, that means for every 100m sailing through the water you are actually making ≈ 70m to windward (sine 45°). If you did that in 30 secs, you are doing 2.3 m/s VMG.  1knt ≈ ½ m/s (or 1.7ft/s) so your VMG is approx. 4.6knts.  Speed through the water is 100/30/0.5=6.666 knots.

This would be a good example of a Flying Dutchman sailing in displacement mode upwind.

So the next definition is displacement, often referred to as Hull Speed (HS).

Start from the simple formula, HS = (√ water line length) x constant.

Because my father was a pilot and speaks in imperial (feet and knots) I will stay there but there will be metric equivalents.   So length in this case is in feet, the constant for salt water is ≈1.4 and the result is in Knots (fresh water is very slightly different).

So take a 29er LWL = 14ft, so √14 = 3.741 x 1.4 ≈ 5.238knts.

So what does that mean?

Because of the nature, the viscosity, density and environment of the water that a sailing boat operates in, as it moves across the water it pushes the water down and out (from the surface of the hull at the bow, the bow wave) and what flows out, must flow back! It does and the time it takes for it to go out and come back to ostensibly the same point, in the case of a 14ft LWL boat, travelling at ≈ 5.2 Knts, that water flowing back (the stern wave) happens at the transom.     So if you travel slower than that, the stern wave will form in-front of the transom, if you travel faster than that it will form behind the transom.

If the stern wave happens behind the transom, i.e you are moving faster then HS, the boat will go nose up, as the stern falls down into the trough in front of the stern wave and you end up sailing “up the bow wave”!

Just like pushing anything uphill, it’s hard work and the heavier it is, the harder it is to push.

Same goes with a boat.   The result is you get a pretty significant spike in the drag curve.

So the attached graph is based on hard empirical data, peer reviewed, yada, yada, yada.

It is the 470, done May 2016 and it is the 49er, pre re-tooling 2005.

hull-shape-diag1Drag curves for 470, 49er and 29er hulls – click on diagram to enlarge

Picked these 2 boats because they are very similar in terms of weight, particularly hull/rig/foils weight (near identical) and they are also pretty similar in waterline length (LWL) but mostly because we have the data to hand.

The 29er curve is my best calculated guess.

With the 470 you can clearly see the hull speed (HS) bump, so for a 470 to exceed HS it needs a considerable increase in grunt.

The 49er has a much flatter drag curve at this point, what my father often referred to as a dynamically humpless hull!   49er has almost double the “grunt” (more correct word is ‘righting moment’ (RM), less correct is ‘power’) than a 470, but if you now look at the 29er curve, because it has similar RM to a 470 and would have a similar if not slightly lower drag curve than a 49er (because it’s lighter) then the reason why a 29er can’t help but plane upwind, most of the time, whereas a 470 has to hold off until circumstances are favourable, becomes obvious.

Switching direction a little, what is an acceptable tolerance when we retool?

We start with what is realistic.  Moulds move, does not matter how well they are built, +/-1mm in the length of a 49er/29er has to be accepted.

So when we re-tool, I insist on an absolute minimum tolerance of +/-1mm under the chine, it matters there, because water is uncompressible and that 1mm moves the water alongside it, and so on, and so on!

How far, the best example I have was Helen, who worked for me for 15 years, besides being an accomplished glider pilot and really amazing with FRP she also represented Australia at the 1976 Montreal Olympics in the one man (woman) scull, think we now call them K1’s.  In the St Lawrence seaway, at 10m deep, they achieve much faster times than in the rowing channel at 4m deep.    So if a K1, at its weight, affects water 4m down, a 29er has to be moving water more than that.    Add to that, Helen still paddles but these days up and down the Danube, often in a 2 woman K2.   Though it’s not meant to be competitive, can’t change her so they exploit the pressure wave, so when the water is restricted from moving down and out, it heaps up beside the boat, forming a pressure wave, and apparently the “grunt” required to paddle up this wave, by a following K2, is near insurmountable.

Coming up from the chine with a 9er, because they are sailed flat, it’s less critical, so +/-1mm at the chine, ¼ of the way up 2mm, ½ way up 3mm, ¾ of the way up 4mm and at the gunwale +/-5mm.

With respect to the deck, provided you don’t increase the beam, industrial tolerance here is +/-10mm and it’s now more about ergonomics than hydrodynamics so that’s just fine.

Those are my parameters, not ISAF’s or ISO’s.    I have imposed them every time we re-tool.

Both the 29er and 49er are re now represented accurately electronically and we can photo scan anytime relatively cheaply to verify a hull if we need to.

But it’s also horses  for courses.  Some people believe it’s a cube law, because it’s 3 dimensional, but I will hold with convention and accept it’s a square law, even still a 29er that regularly exceeds 20knts (occasionally 30) is bending double or triple the amount of water that the 470 does, so it’s only fair that tolerance is +/-1mm (where it counts) whereas the 470 is +/- 17mm over its entire surface.

I won’t get into “humpless hulls” now because it will consume another 3-4 pages, maybe next week’s edition.

Jb

 

Sails – Single Source vs Open

By Julian Bethwaite
Porto17 2015

Favourite topic of the month is sailmaker selection.

For as long as I can remember I have been pursued re open sail making versus single source sail making.

I have been wined and dined, but also accused, slandered and occasionally vilified.

As a result, I have developed a system that allows me to accurately judge the benefit of being a single source sailmaker class as opposed to sail supply governed by rules, and then a system that simply identifies who is the best sailmaker to award a contract to if we choose a single source supply.

The first thing we do is ask the sailors.

In the 49er class this is pretty easy as it’s a Fb driven association.

We tend to do this every 8 years seriously because the sailors like stability and it is approximately a 3 year turn around, not just for the builders but also for the sailors.

So what I am saying is that to switch from one sailmaker to another in the 49er, it can only happen in

a) an Olympic year, (and even that needs some pretty careful planning) and

b) the builders need to know about 3 years out, builders in this case don’t only mean the boatbuilders but it also requires the old sailmaker to retire workers and stock and the new sailmaker to build up stock and capacity, and it requires the boatbuilders to forecast far enough ahead to have adequate stock to satisfy the Olympic sailors till the end of the Olympics where the change is to take place.      Nb1

An unforeseen cost is that it is near impossible to get an existing hi-end sailor to test the new sails, so inevitably it becomes a live test.

I will give you an example!   We are just about to introduce sails into the 49er class that will better handle the increased downhaul loads that the 49er sailors are now subjecting the mainsails to.    We produced 10 suits of trial sails so that they could be tested.    These sails are off the same patterns, same size, on the same masts but have altered panels in the luff to better distribute the loads.    Everyone knows they are coming but no one wanted to use them because they were different.

So once again, we have a live test, and that’s expensive on the sailors!

So first thing we do is ask the sailors.

The next bit, there has never been a push towards open sailmaking in the 49er or 29er class and the attached excel spreadsheet probably explains why.

sail-price-comparisons-oct-2016

Oct-16 Source Currency if not $USD $USD Nb1 NB2 Nb3
Sail Type Web Cost Battens etc Assc costs Sail Cost Area Cost/sq m
49er Mainsail £1470 $1,475 $163 $100 $1,212 16.2 $74.81 Nb4
49er Jib £710 $713 $80 $100 $533 5.7 $93.43 Nb4
49er Spin £1,580 $1,586 $100 $1,486 31 $47.93 Nb4
FX Mainsail £995 $999 $100 $100 $799 13.8 $57.87 Nb4
FX Jib £575 $577 $60 $100 $417 5.4 $77.24 Nb4
FX Spin £1,095 $1,099 $100 $999 25.1 $39.80 Nb4
29er Mainsail £706 $708 $75 $60 $573 8.64 $66.38 Nb4
29er Jib £380 $381 $40 $60 $281 3.76 $74.83 Nb4
29er Spin £730 $733 $60 $673 16 $42.04 Nb4
470 Mainsail $1,162 $1,162 9.45 $122.96 Nb5
470 Jib $598 $598 3.59 $166.57 Nb5
470 Spin $805 $805 12.16 $66.20 Nb5
420 Mainsail $797 $797 7.4 $107.65 Nb5
420 Jib $469 $469 2.8 $167.41 Nb5
420 Spin $601 $601 9 $66.74 Nb5
Nacra Mainsail $1,907 $1,907 15 $127.14 No info, 2014 Pr
Nacra Jib $701 $701 5 $140.19 No info, 2014 Pr
Nacra Spin $1,115 $1,115 19 $58.70 No info, 2014 Pr
Laser Mainsail $604 $15 $589 7.1 $82.96 LP Web Price
Laser Radial Mainsail $604 Does not make sense $15 $589 5.76 $102.26 LP Web Price
Finn Mainsail $1,610 $70 $1,540 10.2 $150.98 Nb5
Optimist Mainsail $540 $15 $15 $510 3.3 $154.55 Nb5
RSX Mainsail € 996 $888 $888 9.6 $92.50 Pryde Web price
Nb1 = 9er sails are sold complete (see Nb4) in a bag, with full set of batten & a repair kits.  Their cost is as per Ovington web page
By way of example of the above, a set of 49er battens = £175.95 + Sail Bag £15 + Reapir Kit £25.    Total =  £215.95
£ 215.95 = $USD 287.11  Less 18% Vat Less 2,5% duty less 5% Logistic  = $USD 163.02
Nb2, Where a Class association fee is included in the price of the sail and not added afterwards
Nb3 = Sail Area as per ISAF page unless obviously wrong, in which case via the class rules, see http://www.sailing.org/classesandequipment/49ER.php
Nb4 = Ovington web page, https://www.ovingtonboats.com/index.php/shop/49er/sails.html less VAT (18.5%) less 2.5% Duty & less 5% Logistics
Nb5 = North Sail, North America site, see http://www.onedesign.com/tabid/25201/Default.aspx

I can’t claim credit for this format, it was started in 2000 by Tim Coventry of Laser fame, but I update it every 2 years. The rationale is if I go to any of the big sailmakers and ask for a price of a mass produced suit of sails, first question is what’s the area, and second question is how many battens does it have, third question is what’s it made from. They then give you a rough price! If you get past that point, who is doing the digitisation (as in whose design) and who is managing distribution comes into play.

In the attached spreadsheet we actually go to quite extraordinary lengths to get the numbers right. It’s important. We go to the Ovington page, as they have fully priced 9ers sails and we know the cost of importation, freight (often sea), duty and VAT.

We also can go into exactly the same page and find out the price of battens and sail bags and the repair kit. We also know how much the class association button costs and we can end up with a highly reliable cost figure.

Just so this is clear, a 29er mainsail on the Ovington site is £ 706. In that price is VAT, duty and logistics (freight and handling). If you remove all of those and convert it to $USD you end up at $USD 708 for a 29er mainsail in a bag, with battens and a repair kit with the class fee paid. If you now remove the cost of all those items, you end up with a cost of $USD 573 for a 29er main.

And then we go to say the LP Laser site and get the price of a Laser sail.

We specifically pick the North site for the cost of the other “notable classes” because those sails are made in the same facility as the FX sails are made, namely Sri Lanka.

Compare a 470 mainsail and a 29er mainsail because they are the closest in area, and these prices are as of September 2016.     But the empirical evidence is plain, and probably the reason no 49er or 29er sailors want to go to open sail making.

Just about every open class sail making is +$100/m²

Just about every single source class sail is sub-$100/m²

In the defence of the open sailmakers there are reasons why they are more expensive, and they include different designs for different masts, different demands from crews, who want different style sails (because they can) and the demand by those crews to use materials that are often expensive (again because the crews demand it) whereas with single source you simply don’t have those options.

While still on this spreadsheet there are other factors that have not been taken into account.

For instance, the number of sails, often there are 3 types of Finn mains, because you can.

When it comes to longevity of the sails, we demand that a sail be good for racing for at least 3 events in a worst case scenario, so for instance a 29er spinnaker is made from top end DP SCN 300 cloth silicon impregnated and we are just about to up-grade (over the next 2 years) to an even higher grade cloth (that will be introduced into the 49er this year.)    Its nominally 3/4oz and by definition will last significantly longer than ½ oz polyester used in other classes.   Again, if you are sailing say a 470 and can use ½ oz, why wouldn’t you!

49er sails are under higher load than the FX, bigger boys, pretty simple so the corner patches/piping are bigger and made of “sticky back”.    It’s expensive hence the increase in cost per m² over say an FX.

We could quite possibly cut back the size of the reinforcing in the 29er main and jib, but I think that is a false economy.

So if the decision is made to stay with single source sail making, we start to look at different sailmakers, and I personally run a test every 2 years.

That test comes in many different forms.

Presently I am in the process of developing some new products so I had need to seek some pricing and one of the sails I was seeking was near identical in size to a 29er mainsail.  So I spec-ed a sail near identical in size to the 29er, to 2 of the big sail making companies in the world.    Same number of battens, similar material, same potential numbers to be produced, as far as possible the same product.     They came in very similar price to Pryde (the current 49er and 29er sailmaker) but without battens, bags or sail kit!

29er 2013 Worlds11

More often, I get approached with a request to consider a new sailmaker to produce for one of the classes.   Presently exactly this is happening with 29er sails!  So in this instance we simply allow that process to run through to completion, that is yet to happen, and it will be interesting to get the results.

If the numbers are “interesting” we get into the ability to supply, distribution, warranty, stocking, materials and then the ubiquitous testing process.

Above I have highlighted Nb1 as the unforeseen costs of making a change in sail making.   The late Ian Bruce used to tell me that it cost about 7% to switch suppliers.

It’s probably true, but if we took that line then we would never switch, and if someone does come up with a new and better idea, and it’s impressive, then we will look at it.

Bottom line, I’m always looking!   Nothing remains the same, and I do miss the excitement of unbridled sail and mast development.

But until the sailors tell me that they are happy to pay open source sail making prices, I can’t justify the additional cost, particularly as the rules and complexity of the class would increase dramatically for little or no benefit.

But Norths are regularly approaching me, and they used to produce for us, Quantum have also made some overtures and if it ever did happen, we have got extremely good at developing a system whereby the sailors make the decisions and I just get to rubber stamp a change.

Julian Bethwaite
4 September 2016

WHY DOES SAIL AREA HAVE TO INCREASE IF YOU CHANGE TO A SQUARE HEAD?

The 29er Carbon Rig – Status Update on the page below is getting increasing traffic, started at about 2/day, it’s now well over 16/day and there is a lot of interest.

If I read the questions correctly, there is quite a bit of interest in the process by which we select the size of the rig, particularly the height and the workings around a square head.

What we know is that if you simply reduce the weight of the rig, by whatever means, (in this case by switching out Alloy for Carbon) and do nothing else, there is an “empirical fact” that you need less crew weight to drive the same rig.    That weight reduction has been of the order of 5-6% in the case of a stayed rig (like a 29er).   (On a rig like a laser, it’s a lot more, because the reduction in over-all weight of the mast is so much bigger!)

If the desire is to maintain the existing weight bracket, then one way to do that is to increase sail-area, especially up high, and probably the most effective way of doing that is a square head.

Square heads have other advantages also.

Recently we have seen the advent of a rash of new designs in aircraft, the 787 and the A350 being right out there.   My pilot friends tell me the fuel burn of these machines is dramatically less, they are that much less draggy, and a lot of that has to do with how they “wash-out” the wing tips.

We could do that also, but it would be expensive and we are not flying at 40,000ft so it is not the most effective way of resolving the problem given a skiff.

A well designed square head has a lot going for it and “washing out”, reducing “induced drag” is a very fortunate side effect.

Little known fact but bearing-away with a square-head 49er is a lot easier in 20+ kts than the old pin-head main, and I can attest to that personally.

Take an existing 49er.    The mainsails are being retired because the shape in the lower ½ becomes undesirable, mostly because it is flat off the luff, and hooked in the leach.

We never get to the point where the upper ½ loses shape or becomes undesirable before we lose the lower ½!

Even the changes that are due to come into effect straight after the Olympics, in the 49er, in which we will dramatically alter the manner in which we transfer the downhaul loads up the rig will not alter this phenomenon.

The lower ½ of the mainsail ages out probably twice as fast as the upper ½.   But a well-designed upper ½ (square head) prolongs/doubles the age-out factor of the lower ½.

So why?    When a gust hits a conventional (pin-head) rig, most of the effect is to increase leach tension, and as that increases it’s like tying a rope between the head and the clew and then tightening it.

The whole mast bends!    As it bends it pulls luff curve out of the main, as the main goes flat, loads go up, the greatest unsupported area in the main is the lower ½, so that region is subjected to maximum load and gets tired soonest!

2016 Nacra 17, 49er and 49erFX World Championships in Clearwater, Florida - Racing Day 5

With a square head rig, same gust hits the rig, the first thing that happens, if it’s designed well is the load or the leverage on the back end of the square head increases more than anywhere else, as a result it “feathers”, it moves to leeward until its aligns itself with the wind.  As it does that it pulls the mast head aft, as it pulls the mast head aft, bending the mast in the top ¼, it flattens the upper main, sure the loads go up, but the cords are so much shorter the cloth can handle that extra load much more easily than the lower sail and also it’s exactly where you want the sail to flatten off, up high, where it has the greatest effect.

When Chris Cairns first did this in the Tornado class it was very, very clever!

Square top Tornado

The added bonus, is a Carbon Square-head mast will bend around 2%, the existing pinhead rig bends double that, and the mean diameter of the Alloy rig is around 66mm, mean diameter of the Carbon rig is 48mm and it’s a X² law.      And that is the biggest reason why a carbon mast will last theoretically indefinitely whereas alloy has a very defined life span.   Just go ask the aircraft industry.

That’s why we should be going to a square head.    It is also easier to set up, bear aways at the top mark are easier, and it will last that much longer.  It’s just a no brainer!

Re rig height.    The B14 went Carbon, but then also increased sail-area without increasing mast height.   And maintained crew weight (nominally).

If we can limit the increase in mast height to around 50mm, then we don’t have to alter fore-stay lengths, spinnaker hoists and you could pull a new main up the old mast, not sure you can pull an old main up a new mast, it will sail, but you won’t be fast.

I am presently engaged in some other rig design issues not too dissimilar and it now appears this is, in fact, possible.    A lot of this comes from the FX class.

So don’t ever say the 49er has no bearing on the 29er!

Julian Bethwaite