Designer Update to the Carbon Rig for 29er
Bethwaite360 is committed to supplying all components of high performance sailing, specialising in 49ers, 49erFX, 29ers, Tasars and Lasers – boats and parts. We will supply and deliver to all countries at the best price and will ensure prompt service and delivery.
Sailing Equipment, Sails, Spars, 49ers, 49erFX, 29ers, Tasars, Lasers, Foils, Ropes
post-template-default,single,single-post,postid-22333,single-format-standard,theme-stockholmNEW,stockholm-core-2.0.2,woocommerce-no-js,select-theme-ver-6.1,ajax_fade,page_not_loaded,,qode_menu_,qode-single-product-thumbs-below,wpb-js-composer js-comp-ver-6.4.1,vc_responsive
Title Image

Designer Update to the Carbon Rig for 29er

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


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.


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.


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 []
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.


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.

No Comments

Post a Comment