Simple wing sail

I thought that I would provide some details of a very simple wing sail that I have made for a small trimaran (initially mentioned in another thread “Testing a small trimaran”). I haven’t come across this method in my searches, but it is so simple that I can’t imagine that it hasn’t been used before, so my apologies if I am repeating work previously described others. I should begin by saying that it isn’t a high performance wing sail, and may not be particularly durable. However, it only cost me ca. $40 AUD in materials and took ca. 4 hours to make. Therefore it might be an interesting option for those who are curious about wing sails, but don’t want to spend the time and money required to produce a high performance one. I should also state that the technique probably isn’t suitable for large boats. Of the trimaran classes it may only be suitable for the 65M class (I guess that my boat fits in this class being 400 mm in length).

I won’t give detailed instructions or plans, partly because the design isn’t optimised, and partly because the technique is so simple. I’ll just point to the crucial features of the design and construction.

To begin with, the main wing. The construction method is based on a method used to produce simple depron foam model planes using 3mm and 6mm depron foam sheet. A description of the method is provided on the following site:

The only significant differences in my approach was that I:

  • used double (5mm width) and single (1mm and 40 mm width) sided tapes rather than glue;
  • used a 6mm o.d. carbon fiber tube rather than the spruce spar on the leading edge of the wing (with a few cm protruding from above and below the wing);
  • made the wing with one internal 6mm foam piece, cut in a shape that made 3 sections.
  • used 6 separate pieces of 3 mmm depron sheet, 2 for each section.

The 3 flaps are made from single layers of 6 mm depron foam sanded into wing shaped profiles.

The flaps are attached to the main wing in the following manner. At the top and bottom of each of the 3 sections of the main wing a piece of teflon tube (3 mm o.d., 1.5 mm i.d.) is taped to the trailing edge (with a small spacer, I used a piece of the 3mm foam, to provide a small gap between the main wing and the flap). On the leading edge of each of the flaps, two pieces of CF tube (3 mm o.d., 1.5 mm i.d.) are taped in such a position that they are immediately above the teflon tube on the wing when the flap is in the correct position. The wing and flaps are then attached by passing a length of carbon rod (1 mm o.d.) through the tubes on the main wing and flaps. Each of the flaps are joined by a piece of tape on each side.

The CF tube on the leading edge of the main wing has another CF tube (3 mm o.d.) threaded through it. This thinner tube is positioned in a hole on the deck, and at the top it is attached to the stays that hold the whole assembly in place. The wing sail rotates around this inner thinner tube.

A couple of pieces of carbon tube are attached to the lower edges of the main wing and flaps as attachment points for the sheeting system cords. The approach to control of the main wing and flaps is shown below:

Due to the size of my boat each cord is controlled by the same sail winch and consequently it is not possible to adjust the position of the flaps relative to the main wing (except during the setup). In a larger boat it would be possible to add another servo, and thus be able to control the flaps independently. Despite this, the boat seems to sail ok, but did take a bit of experimentation to determine the lengths for the two cords that provides reasonable angles between the main wing and flaps over a range of main wing settings.

By adding a third lead off the continuous loop, a jib can also be controlled.

Some details of the completed structure:

Height: 540 mm
Width: 160 mm (max)
Final weight: 70 g

Some footage of the sail in action:


It is certainly different to sailing with a conventional sail, providing alot more power for a similar surface area. Too much power in this case, my next sail will be a bit smaller.

Now for a disclaimer: Everything I know about wing sails I’ve learnt in the last week. It is therefore very likely that I have made numerous errors in the design. Any tips, comments and refinements would be appreciated.

Thanks for sharing - this sure looks like an easy way to start experimenting with wing sails

thanks for sharing your build.

even with a simple construction like this and on a small boat you can already see the performance of a wing sail - there has been a few trials already on a Mini40 cats and tris but finding the tricky balance of weight, efficiency in a small package for a boat that is still not big is key to success. The acceleration of these boats in any wind higher then light gently breeze is difficult to handle whereas with standard sails the sails shape changes, absorbing some of the power but yet providing quick response and acceleration.

Like any new technology I’m sure it’s a question of time after trials and errors that someone comes out with at platform and wingsail which outperforms regularly rigged multis. But we’re not there yet… give it time and maybe … I say maybe…


I agree that it is going to take time to develop a good platform, the build time on each sail will make trial and error a prolonged process. On the up side, they are fun to play with. Here is my latest modification, let me introduce the Swing Wing:


ok, since I’m not a multi-hull guy… could a wing sail be made to be competitive with a comparable soft sail…

I’m, thinking RG65 class. where maybe you could do with a bit wider hull to help keep some stability… but will it payoff in lighter air were a wider hull with more wetted surface is a penalty?


A couple of thoughts on your observations. Regarding the problems with boats to date in strong wind conditions: I have only seen one boat for which there appears to be more than one wing sail, and that is the boat described in a recent post that won the “Round the Island Race”. Most boats with soft sails would have several sets of rigs for different conditions. Perhaps the same approach is required for wing sails?

Your observation that soft sails can absorb some of the power of a gust of wind is interesting. Looking at the 2-section type of wing sail, there appears to be several ways of achieving something similar. Much of the power comes from the position of the flaps. The cords that control the flaps could have springs or elastic added that would allow the flaps to respond to a gust. Another approach would be to make the connections between the flaps somewhat elastic.


I have been following this subject with interest, and seem to remember reading somewhere that a wing should provide less lateral loading than soft sails, meaning a wider hull may not be necessary.

I will see if I can dig out the source…



I think it was here… Very interesting and practical.

Hi Marc -
reference the 18 Sq. Meter Class, circa early to mid 1980’s…

Sail area is limited to 18 sq. meters (approx 194 sq. feet)

Softsail boat with full sail area used a 32 foot tall mast
Wing boat (with smaller sail area - not sure of final measurement) was 28 feet tall

Not only were they very competitive the boat with the solid wing (leading edge and single flap) had much lower center of effort, thereby reducing the “tipping” tendency. As for comparison, the early meetings of these two had the wing much faster. By the end of the second year of competition, the softsail was often winning. On any given Sunday, it was a coin toss who would win (sailor and tactics) and the class is a single-handed class 18 feet long x 11-12 foot wide and no weight limits.

As one of the persons involved in the development and early promotion of the US Class for the RG-65, it can most certainly be sailed with a solid wing. If you try - just use a single panel to experiment, and control speed by angle of attack of the wing to apparent wind. Keep in mind, unlike multihulls, you are still hauling around a chunk of lead under the hull ! :stuck_out_tongue:


BTW - this class (18 Sq. Mtr.) did not use jibs - only mainsails that never were reefed. The owners found that they were able to point higher upwind than a boat with a jib, and it was one less thing to worry about and trim when sailing single handed. Downwind, a well sailed 18 Square was easily able to catch and pass a Supercat 20 !! Upwind it was the skipper that made the difference.


I agree that a solid wing will be more efficient than a soft sail. being thats its more efficient, Ie it creates more lift which equals more lateral movement…??
Also you have the weight penalty as i’m pretty sure the wing is heaver than a soft sail…

got me thinking now…

got until march… hmmmmmm


I guess I could build a single panel main with no flap and see how it does and if I need/want more performance I can add a flap, maybe use sail material and make a soft flap?

With the jib, though it helps balance the boat cE… with just a main “wing” the CE will be too far aft using the current mast step for a conventional rig…NO???

Maybe one day dick I’ll come over to the dark side of mulit hulls…

well i was working on the deck for my IOM…and had a hairbrained idea… bend some plywood, tape it and put down 6oz glass…

Marc -

I think your CoE of the wing will be just a touch behind the mast - and may be acceptable (at least for trial). The multi’s are always sailing with a decent amount of weather helm, which allows the boat to 'hunt" and lifts. Being on-board you can feel the weather helm kick in when a gust hits. This gives you the choice of sailing higher, or footing off slightly for more speed. I recall seeing photos of someone’s RG65 with solid wing - but can’t remember who/where. Seems like it might have been from Argentina or Chile … I could be wrong. I will see if I saved any photos - but doubt it.

These are photos of a friend’s 2 meter with single panel wing. Was simply too powerful, so he reduced size and added a single trailing edge flap. Keep in mind, flaps only add camber - angle of attack is the starting point.

Give it a try.


Interesting tread !
Sorry to enter in this discussion, I appreciate a lot reading about sails. Very rare topic !
According to my limited knowledge on rigid sail, I see that the factor ‘speed’ is almost totally ignored.
What I mean by that is that if the boat cannot develop and reach a good speed, the benefit of the rigid sail is lost and can be less performing then a soft sail. By good speed I mean over 10Kt or more.
I wonder if a compromise could be considered with the use of thicker mylar sheet and eventually in one single piece !
Certain diagrams in my books show testing comparison between soft sail and masts and solid metal sheet without mast.
The solid sheet, often aluminum, is producing the best results. Of course one cannot imaging to put an aluminum sheet on our models, but a compromise material why not !
Sorry again


A late entry, but a good entry. I’m wondering about your definition of rigid sails. Do your books include comparisons of soft sails with wing sails?


well the glass came off the panel ok

still abit flexible… but a couple ribs and some camber will solve that.

just need to lay up the other side. then the fun.

how much chord and how much camber. and what shape. rectangle, or tapered trailing edge… similar to what the AC boats are running…

Hi Jim,
rigid is like the wing of an aircraft and with thick profile while the soft sail is considered of thin profile.
Thin profile accept larger angle of attack that Rigid sail cannot and stall rather easily.
Recent AC45 races showed how many times catamarans where stopping after turning around a buoy. Not very nice to see !!
Displacement hull like mono-hull cannot make use of rigid sails because these boat cannot develop sufficient speed as such to render the rigid sail more efficient.
Unfortunately books are not making comparison tests yet.
The compromise often used is the batten sails as on surfs.
The rigid sail is composed most of the times by two profiles, one in the front and one in the rear called flap. The most important to reach the efficiency is to adjust the gap/window between the two profiles. Failing to do that, the rigid sail will loose his potential and the soft sail will be a better choice.
This all what I know.
For sure if the boat cannot go fast, the rigid sail is useless.
One day I will prepare a batten sail from thicker mylar sheet 150g/m² against the usual 75g/m², knowing that the CG will shift higher due to weight as happen already with the rigid sail.
That’s all

Thanks for the clarification Claudio.

I’m loathed to enter the debate regarding wing sails for monohulls, as it seems to an area you have all discussed before and it appears to be a contentious topic: However, there does appear to be plenty of room for experimenting at a model scale, and this thread does appear to have some useful suggestions regarding aerofoil selection.

From the discussions I have read it seems to be generally accepted that the weight of the wing (particularly at elevation) is a crucial factor for monohulls. This is probably a crazy idea (and I appreciate that the two sails work differently, and hence would need to be set differently), but I wonder if it would be possible to have a 2-part sail where the lower section could be a wing and the upper section a soft sail? Does anyone know if this approach has been tested, or have any insight on how it could be made to work? If feasible, this might also resolve the problem of requiring multiple sets of wings for different wind conditions - the lower wing element could be kept constant and the upper soft section changed to suit the conditions?

If I have well understood, the rigid sail does not need to be reduced in size vs. wind force as the soft sail has. The rigid sail can be properly oriented to cope with the situation, while the soft sail need to be reduced in surface.
The mix you propose is part of the experimental work you may carry on…

Claudio: I think that you are correct, by adjusting the twist some adjustment can be made to account for the wind force. However, I have read that one of the weaknesses of winged sails when compared to soft sails is the inability to reduce the total surface area to respond to changes in the wind. Perhaps varying the twist isn’t sufficient in some cases? Can someone better informed that I elaborate?

Having built a wing without knowing anything, I’m now doing some reading and appreciating how much there is to learn. Whilst reading I’ve found an explanation for some unusual instability I observed whilst testing my wing sail. When using a jib I had a couple of capsizes, bow over stern. I can now see that this was probably backwinding, which is a bit difficult to pick up with a rigid sail. Examples in the footage below:



do you have a cross section of the wing you’d be willing to share…

I’m sure I could just “guess” at an NACA symmetrical foil… and pick one… or create one in Delfship…