New 27' trimaran design by Kurt Hughes

[Samnz]

Samnz,

This is a very interesting thread. Would you care to qualify the above statements?

And in general, I do hope the thread remains civil. It would be a pity if it ended up as war of word attacks and counter attacks!!!

regards

I was meaning "any of yours" in relation to Garys 3x foiling tris and a skimmer he designed, built and sails on. Not "any of yours" in terms of the whole forum!!!!
I would love to see Gary come and do a race and prove to the non believers how well they do/dont perform!!!
(Iv asked him in person 10+ times to come and race)
Gets a bit tiring hearing how slow/conservative the 8.5s are when he refuses to come race against us!!!

 

[cavalier mk2]

We cruised in company with a friend in Canada who has what is basically a racing Cross 36 design stretched to 44 feet. With a old style cutter type rig with a huge fortriangle and 150% genoa he was way faster than us in the lightstuff but needs to roll up jib as the wind goes over 10 knots. I've been trying to come up low cost solutions for drifters and contemplating a log canoe style topsail to get the rig higher for the zephers.

 

[kiwi_bob]

Not sure how this turned into a critique of the 8.5M rule. For this boat what are the actual dimensions? Do we know it wouldn't fit within the rule - looks like it may be too wide and too high but do we have any actual facts here??

 

[Corley]

Thread drift is fine by me it's discussing a pretty vague subject anyway a few concept renders for a fast charter boat.

This particular Kurt Hughes design would be too beamy for the 8.5 rule so I guess that rules it out for now. I'm sure if he was approached to design a tri expressly optimised to the 8.5 rule and it's parameters he would do it justice. This design is intended to have high aspect rig with a decent amount of accomodation for a small trimaran. He does composite boats too so the boat would not have to be built in cylinder mold could be foam sandwich or carbon/core construction. On my boat for example he has provided beam scantlings for glass and carbon construction.

 

[cavalier mk2]

What is the weight difference Corely?

 

[jamez]

Not sure how this turned into a critique of the 8.5M rule. For this boat what are the actual dimensions? Do we know it wouldn't fit within the rule - looks like it may be too wide and too high but do we have any actual facts here??

This new design appears to be a development of the carbon beamed redux of the H26 that kurt put up on his website a while back.

http://www.multihulldesigns.com/designs_stock/26tri.html

I looked at building the H26 and corresponded with Kurt about building it with a strip main hull. The rig was within the 8.5 airdraft height (12 metres on the study plans) and had two berths, so all the boat needed to qualify for the 8.5 rule was about 100mm more headroom and to be built with a foot less beam, which Kurt said wouldn't be a problem. It would also be relatively simple to stretch it .4 of a metre to make the most of the 8.5 box.

Such a boat would have to be quick as there is not a lot to it, and that includes interior space. There are pics of Caiman's (the yellow H26 on Kurts site) interior here some where - its pretty tight. The double berth shown is about 1.1 metres (3'6") wide and has max overhead clearance of about 600mm (2'). That's not a criticism, the boat is what it is and is definitely angled toward performance rather than accommodation space. The boat is a great example of Newicks rule IMO.

So the new 27 could certainly fit the 8.5 box if designed with above mods in mind. The question that comes to me is whether the boat would actually be quicker with 6.5 boa as it should be able to lift the centre hull earlier?

 

[Gary Baigent]

We need to know the rig height - and Kurt has usually been pretty conservative with his rigs (except for his F40) - but this 27 might be different because it carries foils, has a wide beam (square platform) and I'd guess has a very powerful rig to make full use of the extra righting moment achieved by the beam and the foils.
So this boat looks a much higher powered version of a Kiwi 8.5 ... and no way in hell will it fit the NZ 8.5 rule. And why should it? The KH27 is a minimalist craft (hence low headroom) and oriented to power and speed, not a half cruiser, half fast design.
In some ways it reminds me of the Polish X 25 design whose figures, weight, beam, SA suggests it a much more performance oriented trimaran than the similar Seacart 26 - and more applicable to a comparison with Kiwi 8.5 than the larger Seacart 30, which is an entirely different and larger boat.

 

[cavalier mk2]

Kurt tends to over ama his boats, perhaps with foils weight could be saved by trimming them down?

 

[jamez]

We need to know the rig height - and Kurt has usually been pretty conservative with his rigs (except for his F40) - but this 27 might be different because it carries foils, has a wide beam (square platform) and I'd guess has a very powerful rig to make full use of the extra righting moment achieved by the beam and the foils.

I would certainly expect the KH 27 to have a proportionately larger rig than the KH 26. It will be interesting to see the details as they become available. If the kH 27 ever gets developed enough to become a stock plan I'm sure it will be found in the racing section of Kurt's site.

So this boat looks a much higher powered version of a Kiwi 8.5 ... and no way in hell will it fit the NZ 8.5 rule. And why should it?

By that analogy Charlston (F28 racing in Auckland) would also be a higher powered version of a Kiwi 8.5, but I've not heard to anyone refer to it that way. I did not say it should be altered merely suggested that it could. Surely many of the design features could also apply to a minimalist NZ 8.5? Whether someone should bother when there are already purpose designed 8.5 tris coming on stream is a different question.

In some ways it reminds me of the Polish X 25 design whose figures, weight, beam, SA suggests it a much more performance oriented trimaran than the similar Seacart 26 - and more applicable to a comparison with Kiwi 8.5 than the larger Seacart 30, which is an entirely different and larger boat.

In what way is the X 25 (Exploder wasn't it?) comparable to a NZ 8.5? The SC 30 at least has reasonable headroom and some pretense at an interior - (particularly the new FCR version) which the other two don't have. Shrink an SC 30 down to 8.5 metres and the result would be very similar in many respects to Jt's Meltdown.

 

[Gary Baigent]

Gary Baigent quote:
"In some ways it reminds me of the Polish X 25 design whose figures, weight, beam, SA suggests it a much more performance oriented trimaran than the similar Seacart 26 - and more applicable to a comparison with Kiwi 8.5 than the larger Seacart 30, which is an entirely different and larger boat."

Jamez quote:
"In what way is the X 25 (Exploder wasn't it?) comparable to a NZ 8.5? The SC 30 at least has reasonable headroom and some pretense at an interior - (particularly the new FCR version) which the other two don't have. Shrink an SC 30 down to 8.5 metres and the result would be very similar in many respects to Jt's Meltdown."

No, no, Greg, my fault for confusion, there was mention of the SC30 being similar to the NZ 8.5 in its 6m beam. By the way the SC30 rig is around 15 m tall off deck, far more extreme, even scaled down to 8.5.
My comment was that the SC26 is more in line with the 8.5 and that the EX25 is a more high performance design than the SC26; lighter, taller, more SA, wider and with foils (as SC26 also has). And that the EX25 would be on the same performance scale as the Hughes 27.

 

[jamez]

Gary Baigent quote:
And that the EX25 would be on the same performance scale as the Hughes 27.

Thanks for clarifying Gary. Incidently the Seacart FCR I was referring to has a 13.1 metre stick.

 

[Corley]

What is the weight difference Corely?

Just making an approximation on the difference of weight in the laminations over the approximate suface area at a good resin ratio it looks like the saving will be about 40kgs over the equivalent glass lamination (thats the main beam the rear saves about 30kgs, smaller beam section and less surface area). It's positive in other ways too since the carbon has a better fatigue curve retaining more of it's strength over a longer period of time. The weight saving could be more but the ripstop sections add some weight back into the lamination, no way I'd go without them though . The scantlings also allow for either balsa or WRC strip planking as a core material for the beams which of course has some impact on their weight. I also looked seriously at paulownia strip plank but if the balsa will do the job it still works out lighter overall.

Since the F40's had a minimum weight of 1800kgs Kurt did not go all out to save weight but since the class is defunct now it's worth looking for weight savings that dont compromise strength the most obvious area is in the rig. Kurt's aluminium stick on Gecko (his F40 trimaran) the bare section weighed 360 lbs (about 163kgs) and used stainless rigging. If we migrate to even a non optimal off the shelf mandrel wound carbon stick and synthetic rigging our weight savings are considerable. It also removes weight from where you dont want it lowering your CG and improving pitching and other boat handling characteristics.

Theres a few other areas where we can save weight too the cylinder mold hull shells on Kurt's boat had a vac bagged balsa core if we went with a suitable closed cell foam instead of balsa due to the surface areas there is a good saving to be made in the overall weight of the hull shells. You do concede some shear strength though so it has some caveats.

I'm not really concerned about the weight in terms of performance although obviously there are some benefits but more from a perspective of increasing the boats payload to an adequate level. As some of the races I'd like to enter have minimum fixed requirements in terms of fuel you must carry etc. We are looking at whether a fuel cell and a small battery bank and an electric outboard like a torqeedo might be adequate with a small petrol generator for redundancy.

 

[cavalier mk2]

i like the payload idea, otherwise you end up in the lighter boats need more beam spiral. For much of our needs a Torqueedo could just about do it. It doesn't really work out to be lighter though.

 

[Corley]

The boat just about exhausts the beam idea allready being close enough to square L/B. I'm thinking of weight distribution we can centralise the fuel cell and genny to try and keep the weight low and out of the ends may yet end up with a standard longshaft petrol outboard. The Honda seems to be the lightest by a decent margin they dont seem to have a longshaft model these days though?

The beam scantlings are a bit heavier than normal to enable fitting different floats in future eg If we decide to fit floats suitable for lifting foils. It's not likely but the options there. The boats demountable so you can change floats or even the main hull if you want in the future it's all pretty modular.

 

[cavalier mk2]

I found Honda impellers less durable and the layout harder to service. The bean counters used combination covers to save materials and parts but it means larger disassembles for routine service which your mechanic will appreciate. They still had longshafts last time I checked. Green as I am it is hard to compete with the weight of gas engines. It always bothers me that their is a price premium on the technology we should be developing. We make up for it by sailing well and not using the motor much anyway. Weight out of the ends and aloft does the most good for sure. Sometimes I'll carry the sails forward though as it dampens the rise in a chop for a smoother transition. If the sails don't get shaken up the boat sails faster. Offwind is when they need to move aft for top speed. Modular is a great concept. Building the strength in at the start will give let you develop things more easily.