Wing Sails

HI every body,
I would like to make a Wing Sail for my class M but not limited to.
Is anyone that has already tried this technique may suggest some solutions ? Rigid, semirigid, soft sail.
Just an interesting picture here below and an interestig adress :

Very interesting website, thanks!

If you do a search under “wingmast”, you’ll see a fair amount of past discussion on the subject. Most of it pertains to applications on multihulls & landyachts.

Bill K

Does a wingmast make a jib redundant? Or is there some benifit in a leading edge slot device still?


Thanks you Bill.
The question of FunnyBones is very interesting, personally I do not knows yet . Any hints ?

Nick & Claudio,
I would say no, the jib could very well be usefull. However on faster moving craft where boat speed will exceed windspeed (landyachts, iceboats & to some extent multihulls), there will be a point at which the jib will create more drag than lift & limit top end speed.

This is my starting idea. I would like to use a soft wingsail on my Class M
Any suggestion from someone that already tried similar construction %
I will be gratefull to have some opinions even the negative ones.
Thank you all.

Claudio -

any particular reason you are adding the balsa to the front of the mast to produce a curved entry for the sail? Since the mast is already round, it seems redundant.

For a while, many of the larger trimarans used “ribbon” jibs, which, as the name implies were merely long strips of cloth used to get a bit more flow over the main. In most cases, the solid wing sails (or soft wings) have sufficient power, that they seldom need more or speeded up airflow. The following flaps generally are used to add camber to the wing, and to preven detached flow. As Bill suggests, the speed of the boat will usually offset any jib improvements. Some multihulls, and most iceboats or land sailers will have a jib collapse from the speed/force of the wind. It is also known that some ccatamarans will actually point higher without a jib, than with one. Off-wind without a jib is another story. You have to take the bad with the good.

A fellow working for me is experimenting with a solid wing landyacht, photo below, but is still in the construction phase. He mentioned that even without any fabric/film covering, the boat was moving along his driveway with only the leading edge covered.

I was inspired by the aerodynamic notion where the circular rod presents a Cx = 1.2 and the elliptical form exibit instead a Cx = 0.11 ( Re =100000).
Thank for your advise about the jib.
Revisiting the question I’m actually intentioned to change drastically the surface ratios 85% for the main and 15% for the jib. The jib in fact will be very narrow and according to my view should acts as a front “flap” like on the real airplane wings more or less as you described with the “ribbon”. Obviously all that imposes a change on the hull desing and centering since the CE will be close to the main center and the mast shall be advanced toward the bow, etc.

I must say, I really like the shapes you’ve come up with. Here are a few comments:

-Will the CF tube be allowed to rotate?
-Will the backstay crane rotate in the tube?
-Although the curved mast looks cool, I doubt that the added complexity in construction is justified by aerodynamic gains.
-What is the “moletton” material? I’ve never heard that term.
-Lester Gilbert pointed out some valid concerns about sleeved sails in the “sailmaking” thread recently.
-We have a saying in this country: “The devil is in the details”. You may need to do a fair amount of prototype work to achieve the cross section shown in your idealized drawings. Keep in mind that the actual shape will be largely controlled by sail pressure, thus will be contantly changing to some extent.
-Will the change from one camber to the other be without wrinkles in the fabric & with minimal friction?
-I understand there are some sleeved sail rigs being used on 10 Raters in Britain. They are reported to be lighter than similar wingmasts made out of solid material. Weight aloft is always a major consideration, especially when 2m high.


actually the mast is fixed. The balsa profile (it will be a carbon sheet) supported by rings along the mast and the sleeve are attached together and are the rotating part including the sail.
Molleton : in my dictionary = battting, duffel, soft flanel, swan’s down. This synthetic material is largely used for quilting and support the washing machine. Used here as a soft filler to compensate wind pressure.
Here the sketch of what I would like to do. Expecting comments of course.
The bent mast, is actually left in the idea"s corner, obviously introduce an additional difficulty, but wrinkles along the Luff can be avoided by splitting the sleeve in panels .
I will watch for the Devil !

just a sample !

I think you’re onto a good thing, keep it up!! If your rig ends up looking as nice as your drawings, I will be very interested in seeing the pictures.

Nice, but probably heavy… have you tried the sail batten extending into the mast slot, like te Moths have ?

I’m trying for a RG-65 and will let you know


not possible on class M.
Only 4 battens of max 105 cm lenght.
No semirigid or rigid assemblies authorised - only soft sails.
My actual classe M mast + boom weight is 165 gr. The additional front sheet (2xglassfiber 60gr/m? + epoxy + 20 Rings) will be ~29.5 gr .
Total = 165 + 30 + 52 sail + 7gr jib boom = 254 gr escluding harnessing/scrouds.
Therefore the penalty in weight for de Rig will be in the order of +10%.
What about the increased efficiency ???
Really I do not knows .
Whait and see.

Hi Claudio,

Have you tried the sail design used on the Moth dinghies ?

the sail goes around the mast like for a laser, but here, it’s a lot wider, and the batten inside pushes the sail to curve the sail extrados…

Rgds Calou

I have visited several places and clubs describing their activities on RC Land/Ice -Sailing.
There are a lot of Photos here and there, but in no one ,it is described as the sail is made. i.e. see : htpp://
Have you any suggestion ? just to compare with my design and learning from others

I used to build them out of balsa with a spruce leading edge, but have since been using a foam core with a vacuum bagged skin of glass. These are alot lighter than the wood ones. Here’s a brief desciption previously posted under the “Wingmast as D-rig” thread:

“I’ve handcarved my foam cores in the past using NACA profiles derived from:
But as you say, it’s very difficult to get them anywhere close to “perfect”. More recently, I’ve been paying a guy in California
( ) to cut them on his CNC hot wire cutter, which is VERY accurate. Then I vacuum bag them in 6oz glass using a technique developed by the model plane guys:
( ). After it’s cured & trimmed, I cut in a sail luff groove using a hot knife. I’ve been using NACA 0022 profiles, but may try a bit thicker. In my opinion, the most important thing is to get a fair curve at the transition from mast to sail on the leeward side. My 68” (1.7m) masts have a straight taper from 4" (10cm) at the base to 2.25" (5.5cm) at the tip, so I don’t know if this would work with your curved taper"


thanks Bill,
On class M no rigid or semi-rigid Rig assembly are permitted.
Max 4 batten of 105 mm lenght.
I search for a soft sail Rig as presented in this tread, someone that have better experience.
This picture do not tell me if is a soft sail

Best Regards

Hope you can get going this fast with out the break up at the end.

Very umprobable with a sailing boat class M, but still I do not have any answer to my question above.

Sorry, I thought my other respnse answered your question. That picture is of one of my early wingmasts made of balsa & spruce. The sail is 4 mil (.1 mm) mylar (polyester film), so I guess you could say that it’s soft. It’s alot stiffer than Dacron or Trispi. The stiffness helps to obtain a fair curve with the wingmast on the leeward side (essential for an efficient airfoil shape). I have no idea whether this would be legal under the M rules. I know that the 10 Rater class allows solid wingmasts, but there is a point at which width starts to incur a measurement penalty.

BTW, I sailed on ice for the first time this winter. Was doing great until a moment of inattention caused it to crash into my foot & break some gears in the steering servo…;-( . Oh well, I’m sure I’ve got some replacement gears & tomorrow is predicted to be nice weather…;-).


ps; have you checked out Tom Speer? (check out the pdf version for better graphics)