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Old Nov 06, 2011, 02:37 AM
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WingCat's Avatar
Australia, VIC, Bendigo
Joined Nov 2011
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RC Wing Sail Catamaran

First time in the water. It is 2 metres from water to wing peak.

It sails. But it doesnít sail like a sail boat.
I can get it to go to windward easily enough.
I cannot get it to hold a broad reach. Mainly because
the servo that is meant to control the wing is not strong enough
to do that job on a reach. Going down wind is also a problem.
It is easy enough to get it going downwind
with the wings squared off. But on a couple of
occasions I was able to get it going downwind close hauled
and I mean it was going hard.
Iím not sure how I got it to do that but it is doable.
Clearly it is a skill I will have to develop.




When it went nose in it didnít look like pitching.
It just slowed [violently] or stopped dead.
The stays are way too flexible. They are properly
swagged stays made using 1mm whipper snipper cordage.
Might have to hunt up some 1mm stainless cable.




It is also subject to lateral twisting. A dolphin striker
with tensioning cables will be added to dampen the unwanted twisting.




The angles between the Wing Mast and the Trailing Wings are pretty important.
However, with white on white these angles are very hard to see;
even when the boat is only a few yards away.




Then, it went and performed best with just the wing mast.
It seemed to sail faster and more responsively without the trailing wings.
Probably because the rear wings were not being trimmed properly
when they were attached ????




Iíve sailed a few radio controlled yachts but this is very different.
Some of the bursts of acceleration had to be seen to be believed.

So far..... I reckon;
[1] There is too much weight in the daggerboards.
[2] The daggerboards still have too much surface area.
[3] The wing servo needs to be replaced with a really powerful servo. and
[4] The skipper needs to learn how to trim a set of wings.

Cheers - WingCat
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Old Nov 06, 2011, 08:14 AM
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Joined Jan 2010
215 Posts
Looks great!

I am by no means a specialist with multi hulls or wing sails for that matter. But, you are going to have a challenge on your hands. First, the stays should be SS wire stays to accept the loads....and then your beams are going to have to be strong enough to handle those loads(lateral twisting). On sail(wing) trimming...you won't be able to trim this like a normal RC sailboat...as you discovered when going downwind, sheeting in, and going fast...that is probably how it will work. I mean that as this boat starts to pic up speed, it will create its own apparent wind that will move forward. So the faster you go, the more you will sheet in regardless of your angle to the true wind...It will take practice I am sure.

Hope this helps,
Brian
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Old Nov 07, 2011, 04:47 AM
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Australia, VIC, Bendigo
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Thanks Brian.

All comments welcome.

Cheers - WingCat
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Old Nov 07, 2011, 06:13 AM
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Joined Jul 2005
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Few things that might help, whilst this may seam obvious something to let you know what direction the wind is come from will help with the trimming of the sail. Next you need to understand how wings work a little to be able to trim them correctly. Also an idea of the opperating range of the wing design would also help. If it is based on a NACA 0012 design then from meorey stall occurs at about 14-16 degrees from the wind. However the most efficant position ie higest Lift/Drag Ratio is some where around 4degrees.

Having the flap attached should increse the efficancy of the whole wing as it is incresing the chord angle of the wing, essentailly making one side longer and more curved than the other so incresing the pressure difference between the two sides. Also lift is calculated using its surface area so even leaving the movable section attached in the streight position should generate more lift than leaving it off.

It might help you further to stick soft tufts of wool on to the wing so that you can visually see if the flow is attached or seperating.
http://upload.wikimedia.org/wikipedi...ts_on_wing.jpg
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Old Nov 07, 2011, 08:21 AM
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Australia, VIC, Bendigo
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Hi Yogibear,

Thank you for those pointers. Will definately attach tell tales in a number of places. Not as mant as on that aircraft wing.

One other thing I noticed. If I freed up the wing mast and just used the rudders in conjunction with the chord adjustment, the wing mast seemed to find a useful angle of attack and the boat would sail well enough. I have no idea if that angle of attack was optimum or not. But it was interesting.

I've attached a couple of pics taken during construction.

It all started when I saw this sketch.














These daggerboards and rudders have been discarded.
The new ones have less than 1/2 the surface area.


Cheers - WingCat
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Old Nov 08, 2011, 05:06 PM
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Dick L.'s Avatar
Minnesota, USA
Joined Aug 2002
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Work hard to remove as much torsional twist in the platform that you can. In a beach-cat class - picking up the bow on one side should translate to identical (as possible) height from the ground as the other. Having a very "stiff" platform will work wonders. The shrouds only need to support the wing - no need to have "banjo tight" - let the wing work to it's best position when flat (no camber) then gradually add camber - these do not need to carry as much camber upwind as a soft-sail. Also reduce weight where possible. For off-wind work, lighter is better - and conside it a "leaf" being blown by the wind. Definitely boards are over-long --- did you have problems with the boat tipping? Rudders are a bit big as well. Again, keep in mind you want to keep the water flowing past board and rudders for steering, and turn easily with a reasonably wide radius. Hard turns and lack of weight will stop it dead - which you can use to advantage at the starting line. Hard rudders will brake the thing - which can be helpful ---- or not.

Best regards
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Old Nov 11, 2011, 03:09 PM
Dan Elliott
United States, TN, Nashville
Joined Jul 2011
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Hello WingCat, I have also been trying to create a working wingsail model. Check out my wingsail @ Dan Elliott's thread wingsail catamaran.
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Old Nov 12, 2011, 02:06 AM
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Hi Dan,

Your post is the reason that I ended up on this site

Sooooo much to learn.

Cheers - WingCat
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Old Nov 14, 2011, 01:10 PM
Dan Elliott
United States, TN, Nashville
Joined Jul 2011
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No Kidding? That's why I love this site. I've talked with people all over the world about wingsails. I'll be looking forward to your next post WingCat!
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Old Nov 14, 2011, 08:06 PM
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Looks good! I am in the process of building a wing sail catamaran but am going to put a soft sail on it and learn the boat before moving on to a wing. I am making a mold to produce more then one boat. I think the wing might be too thick maybe that is causing some of the downwind problems. Thin is fast and light is fast. a new carbon wing might be something to try.
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Old Nov 15, 2011, 09:53 PM
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Hi fellow wing sailors,

Bit more can be gained from this link.

http://www.ivorbittle.co.uk/Articles...0the%20web.htm

I will definately be building a couple of these gates.


Cheers - WingCat
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Old Nov 26, 2011, 12:23 PM
Dan Elliott
United States, TN, Nashville
Joined Jul 2011
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This I like! A very clever solution WC.
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Old Jul 24, 2012, 12:34 PM
Dan Elliott
United States, TN, Nashville
Joined Jul 2011
110 Posts
Hello WingCat, I finally got my 60" wingsail in the lake last week, check out my thread for some pics. Topics, Sailboats, Wingsail Catamaran Model, Dan Elliott
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