Wing Sail design

Alex, Macquarie Innovation is an attempt to maximize the force from the wing and there is no restriction on sail area. Also it is an assymetric wing as this craft only travels on starboard tack.
Your model needs to travel efficiently on either tack, hence the two wings to create an assymetric shape on each tack.
Also if you are limited to sail area, then like A class cats, go to high aspect for maximum drive for a restricted sail area, providing the hull can exert sufficient righting moment.
Centre of effort is roughly the geometric centre, but I have provided a link for you related to model yachts to give more info.
http://www.seadercraft.com/sail_crafting.html

 

I know its asymetrical but i meant the shape vertically. It seems quite wing like and would be easier to make than a eliptical section.

Isnt the only reason high aspect ratios are good because they can reach faster winds. Or is there better aerodynamic propeties to high aspect ratios.

There isnt really much point in having a high aspect sail on a model because the mast is so short if the only advantage is increased wind speed.
So you might as well get the extra chord length and make it more suitable in less windy conditions.

Would a solid wing be better if the boat capsized because with conventional sails you get water flooding the sail making it hard to upright. But if the solid sail was buyont you could get away with a shorter keel which means less resistance.

 

Alex, the shape or planform doesn't need to be exactly elliptical, and trapezoid with one pair of parallel sides (base and top) and the vertical edges straight but coming closer together at the top is almost as good.
In short, the theory behind the aspect ratio of sails and wings is quite complex, and there are heaps of sites on the web with diagrams and maths, but L/D (lift to drag ratio), is more favourable for high aspect ratios. No, it is not to do with wind shear and getting the top of the wing into stronger wind with a model. Check out high performance glider wings, and the reasons why they look like that. The downside is mainly that heeling force is greater with tall wings/sails, so you need a deeper or heavier keel.
The bouyant wing will not sink or fill with water, but this is not the main factor, as you want the hull to sail at certain angle of heel for a particular wind strength, which is your main concern.

 

So basically conventional sail for light winds and anything above 15mph use high aspect wing.

 

You've got it now!

Alex, good conclusion! Consider using a heavier lead bulb in stronger winds when installing the wing sail, so might need two different lead bulbs.
I just saw a nice pic of a two part rigid wing sail on the thread re " wing sail for an A cat"
http://www.geocities.com/mec_coleman/magazinecover.jpg

 

What size flap do you think would be best. I think possibly 30% As the fore section needs to be able to hold it into the wind
Just saw that as well

Which side do you think should be leading edge the left or right. I think i could get away with the 1 cm greater than allowed theyr not that strict.

Lets just pray for 30mph winds

 

Hi Alex, I have not done any of this stuff myself. I have already gone a little out on a limb giving you advice already. As far as the finer details, I'm afraid that your guess might be as good or better than mine. Good luck.

 

Ok Thanks for all the help. I might start a thread in the projects section.
Thanks tons
Alex

 

solid sail with extra utility

I had thought about a solid sail design such as used on this land vehicle
http://www.greenbird.co.uk/about-the-greenbird

or like this watercraft
http://www.sailingnetworks.com/news/read/5011

I did some research on carbon fiber and according to the technical specifications it would be rigid enough for a sail. Also you can mold the pieces by wrapping them around a mold and possibly vacuuming the pieces after applying the epoxy.

I had thought of making the wing in sections like a venetian blind were each piece could be taken off or moved. The reason I was thinking about this is because I would like to make each piece fit with each other in two ways. One way would be a sail for propulsion, the next would be to offset each piece. That way you could have the sail become a helix type electrical generator if the mast was fitted to a generator.

Here is a example of a tri helix power generator.

http://www.youtube.com/watch?v=s7k_Ja6DpjM&feature=related

It would be really helpful if this solid sail could be put to use as a power generator when anchored or in dock. If it was properly geared it would generate a large amount of power. A lot of people are ditching deisels for electic motors as seen on as http://www.electricyacht.com
Any thoughts on this?

 

This is a bit late I know but a lot of research has been done By a Dr Hugh Elkaim. You should be able to track it down on the web