A 65 M Wing Sail Trimaran Project

I’m planning to design and build a 65M wing sail trimaran and I wondered if there was anyone else interested in participating? I imagine that a group with a range of skills and expertise would produce a better result in a shorter time than an individual working alone. Obviously the advice and guidance from members of this forum would be greatly appreciated, but it would be great if there were some members who were interested in being more actively involved.

The goal would be to produce a 65M trimaran design optimised for a wing sail (and of course the wing sail). Other design criteria would be determined as part of the project.

Please let me know if you are interested, or just join in along the way.


Before starting this project I would would like to have some success criteria. There are a few basic criteria that I have in mind:

  • minimal pitchpoling;
  • Able to tack reliably;
  • able to fly the main hull.

In terms of speed I thought that it might be good to aim to be competitive with a particular length monohull around a conventional course. Does anyone have a suggestion as to what might be a reasonable target (i.e. what class of monohull)? For example, could a 65 cm trimaran ever compete with an IOM?

Yes, he can! :cool:

Actually a RG65 monohull doesn´t have a chance against a RT65 Armageddon
or against a RTR65 Ragnarok.
Neither upwind, halfwind nor downwind.
Designed by me and produced by Siri and/or Roland.

But right now I couldn´t tell you, which of the profen IOMs would have the best chances on a regular triangular racecourse.
I just started digging into that (IOM-)topic myself.

Proof to me that I´m wrong…:rolleyes:

Ok, being competitive with an RG65 round a triangular course sounds like a realistic target. Although, if the wingsail works properly, it might be possible to beat a IOM down wind?

Hi Jim,

Apples & Oranges, any multi-hull (wing or soft sail) will out run similar scale mono-hull as the multi has less wetted area and no keel fin/bulb, focussing on having a stable multi-platform that you can control reliable & handles on all points of the wind would be a more realistic goal. …after all if you pitch pole what’s the point of having a faster boat if it can’t complete the course ?..bit like tortoise and hare scenario

Just look at Oracle OR-17-1 $illions spent & ended going belly-up !

Cheers Alan

Hello Alan,

I completely agree. My problem is that I don’t know of anyone else in my area sailing small multis. Consequently once I’ve made a boat I can’t really asess if it is any good. I thought that if there were some "rules of thumb’ regarding how a particular length multihull should perform against particular length monohull (such as handicapping rules or something similar), then I could sail against a monohull as a way of testing the success of my design. I guess the other thing I coud try would be to build another common boat from the same class (not that there are many 65 cm tris), and sail them against each other.


If I where you,
I wouldn´t care about other multis right now.

Find someone in your area with any IOM-Boat und
just try to sail better than him with your own trimaran.
If you can beat him, you definitely will know where you stand.
Then find a better IOM-boat and a better IOM-sailor -
and beat him as well.

That´s the way I would go.

Hi Jim, understand your situation, I’m similar in having AC 120’s and no-one locally with similar boat to sail against …ended up building my own fleet so I can bench mark my boats as prep for competition for when I travel to another country (Italy) for competitions.

Makes sense to me now with the way you starting, working a handicap system and improving the handicap vs IOM is far better than sailing alone …for sure !

Looking forward to seeing your progress.

Good sailing, Alan

First draft of plans for the hull and floats, likely to be revised as the plans for the wing sail take shape. I’m trying to keep the design as simple as possible. The boat will have a single wing sail (no jib), set up as a swing wing. The servo for flap control will be in the wing itself, as for a model plane. I would like to try a canting mast, but will initially build it without.

Plans below, suggestions welcome:


Take a look at this idea, maybe good alternative wing with less weight than solid wing :rolleyes:


First draft of plans for the hull and floats, likely to be revised as the plans for the wing sail take shape. I’m trying to keep the design as simple as possible. The boat will have a single wing sail (no jib), set up as a swing wing. The servo for flap control will be in the wing itself, as for a model plane. I would like to try a canting mast, but will initially build it without.

Plans below, suggestions welcome:


Looks worth considering. The control system for the change of camber shown at ca. 20 seconds in will require some thought to achieve on a model scale.

With “soft wing” looks camber control is done same as normal soft sail (clew adjustment) and main boom & can use normal vang to control twist …does not get much simpler :wink:

Is the rotation of the sail around the mast and the position of the main boom controlled separately?

If you look at 33 & 41 sec you can see the wing shaped ribs and boom rotate around the mast (inside the soft wing) independent of each other, the wing ribs and main boom use simple “T” struts with collars in the centre that just slide over the mast and also allow for free rotation.

The soft wing could be made quite simply with Kite material (keep it light) that could be sewn or glued into type of sock that fits over the wing ribs with maybe something like little Velcro to hold the foot of sail to the bottom wing rib.

The back & front stays need to be fixed to top of the mast/crane so don’t interfere with the sail rotation and no doubt the shrouds as well, if your’re using them.

Just need sheeting point on the boom with Vang for twist control & adjustable clew for camber and your away flying !

Cheers Alan


A bit rough in the execution, but seems to work:


I made the front section out of foam and inserted a micro servo in the base to control the boom. I imagine that this setup would work nicely as a swing wing. I only constructed the bottom section of the sail, so a bit hard to be conclusive.


Looking good Jim ! the shape of the camber is nice and smooth for good air flow of the sail surface (better than foam) only question is the comparison of weight between the two options ? remembering still need to add wing ribs.

I like the servo in the front section at the base of the wing, but it is weight in the wrong place, maybe something have to live with for simplicity, but would be nice if could get that weight lower somehow.

All the same it looks very promising, well done !

Cheers Alan

The weight of the servo is an issue, but the simplicity of having it in the sail is attractive. I put the flap control for my foam wing in the hull, which worked ok, but some potential work was lost due to friction and the whole assembly became cumbersome. My guess is that for a small boat there wont be much advantage in terms of weight due to the addition of the ribs and boom, but for larger boats there may be. As you allude to, the real advantage may be in the performance of the aerofoil. As the foam wing I will make will have essentially the same control (swing wing and servo in wing) I will make both and test them on the same platform.

Some things to note: I think that for a good aerofoil the ribs will need to be able to slide somewhat; the correct choice of rib material (in terms of flex) will be crucial.

ps. Thanks for the tip.

Jim so far you have done solid wing and a soft wing, to complete the deck you may want to try combination of the two by using a “solid wing shaped rotating mast section with soft sail”, this would eliminate the need for ribs in the wing sail…it may be even lighter again !?

Don’t want to get too technical at this stage but have attached drawing showing air flow efficiency with different wing mast sections, the trick is to have smooth sail chamber that does not create pockets or separation bubbles, want to keep air attached to the sail surface for maximum drive efficiency.

Hope this is of some help.

Cheers Alan

Back on the idea of the “soft wing” option, maybe you don’t need to use ribs ! let the wind shape the sail naturally, personally I trust nature rather than trying telling it how I want it to work with pre-determined curves, you can’t fool mother nature but it sure can make a fool of us :wink:

I’ve learnt that water and air does not like corners in any shape or form…