I was discussing this the other day. Given that wing masts can be very efficient (see Little America’s Cup cats etc) BUT are a pain to take down in a hurry. Makes them impractical for most purposes. Right? But with small RC boats, this situation doesn’t occur (in fact in IOMs the rigs are complete and I have never seen anyone pack up a sail).
So my question is why so few wing masts on models. I know that the aerodynamics can scale down. Would have thought it an ideal opportunity to get some real performance gains.
The complex on board control elements of a wing sail would be very, very hard to engineer and control via r/c.
Likely by the time you were done you would have a very heavy, very complicated device and one that you would not be able to obtain necessary feedback from the boat to properly trim.
So far as I’m aware, other than perhaps a few lone hobbyists, no one has been able to get an r/c wing sail to work, and certainly no one has gotten one to be fast.
As to a wing mast, I think you will find that the measured sail area you give up isn’t made up by any aerodynamic gain from the wing shape. Plus, the model wing mast is either heavy or not rigid enough. Check out the Walicki Skapel for a succesful aero mast, carbon fiber, stiff, aerodynamic and it rotates. Current cost approximately $300 US. While I personally love and use the mast I think you will find most people find the cost/value relationship out of line.
I have tried a solid foam balanced wingsail on a 12inch model.
Performance was actually very very good some of the time,not all the time though.
It was an experiment for a mass produced rig that would be very cheap to produce.I discontinued experiments when I realized that it would be differcult for Joe average to use the rig in practice.i did not go down the road of flaps etc as it was getting away from the idea of simplicity and low cost.
In short…It has potential.
If you use a single element (flap) wingsail, it is effective and can be, as Brett noted, fast - but has a very narrow angle of attack where it works well. A two element system (trailing edge flaps) will give great results, and can be fast, have a wider effective angle of attack, but as Roy noted, it has control issues to be worked out. In general, a wingsail can be much smaller than it’s softsail counterpart, and generate the same or more power. As you add more flaps, the technology/control must keep up. A few are being used by r/c landsailors, but most are having their flaps set manually for optimum conditions.
Finally, the rig will be a bit heavier than a conventional rig, so a wide beamed platform is usually a help (think multihull) and there are no (that I am aware of) wingsils allowed in any US AMYA recognized class at the moment. Room to experiment, however with the 1 meter multihulls or the bigger F-48’s or 2 Meter multihulls. Maybe some day we will have enough on the water to warrant a recognized class. (in fact, even wing “masts” are allowed in only a few classes).
Dick Lemke
F-48 #US-06
MultiONE #US-06
Class 3 Landyacht #US-196
Minnesota, USA
Are we talking rigid wings or flexible ones (as in lateral mast movement eg Finn mast)? Just for interest sake what would likely occur if one planted a flex wing about the same height and area as an IOM A rig in an IOM and just tested it? Upwind, wherever, wind speeds. Just curious. Even without leading and trailing edge devices. Okay it’s apples on oranges but it would be great to compare anyway.
Nick Lindsley
Australia 0418 727-727
Intl +61+418-727.727
Yes John - this is an example of a wing mast with a soft sail. Currently there is a nice write up in latest AMYA Publication (thanks to Mark Gee - class secretary for 10R Class where it is legal.) on building a rotating wing “mast”.
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I guess I was off and talking about a solid “wing” concept - more like this one that Jean Margail (FR) was playing with on his 2 Meter catamaran. This one has no flaps to induce camber, and has a pretty narrow angle of attack according to my correspondence with Jean.
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Dick Lemke
F-48 #US-06
MultiONE #US-06
Class 3 Landyacht #US-196
Minnesota, USA
Nick,
If you’re talking about solid “wing” airfoils (with or without flaps), I’d agree with Roy, Dick & Brett about issues of complexity & weight aloft.
For the scale of our models, I think the best way to go is a wingmast in combination with a “soft” sail, which will act in unison to create an efficient asymetrical airfoil. A rotating wingmast constituting 20-30% of the total foil chord offers the opportunity to create a wide range of cambers for differing wind conditions. It is possible to create a simple means of automatic adjustment of foil draft as the boat gains speed. “KISS” should be the philosophy behind any of these designs. Significant weight reduction can be achieved by using glass or CF vacuum bagged over a foam core.
Wingmast stiffness is an important consideration. Roy mentions the stiff carbon foil rig used on his Skapel. However, a fair amount of lateral mast bend is indeed desirable for gust absorbsion & sail flattening. This is well evidenced by modern day iceboats: http://www.iceboat.org/images/02-03/2-22-03Monona/IMG_2641.JPG
Application of wingmast rigs on rc models has occured for years on landyachts, iceboats & multihulls. Mark & Whitney Gee have had recent success in the 10 Rater Class. Mark recently made this assessment of the potential for displacement monohulls:
"The wingmast and gooseneck used in that article was developed jointly by myself and my father, Whitney. The masts were used on identical 10R hulls, and since my boat was already completed with a traditional rig, my father was the one to get the test run on the new mast. It worked very well for him and led him to build and use a second mast at the Nationals last year. If you reference issue #137 of Model Yachting, the last page in that issue shows two pictures from the 10R Nationals. You should be able to pick out the wingmast boat from the profiles, but I believe it was sail #22.
We have had pretty good luck with the design. It definitely demonstrates more power than traditional rigs, can point equally as well, and works best on a reach. No doubt that wingmasts can maximize their performance on ice boats and catamarans, but we have seen attractive advantages in the 10R fleet anyway."
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