Thick sail
Thick sail
(OP)
I am designing a rigid sail system for a sailing boat. The boat is a 30ft. long trimaran with an estimated maximum speed of of 18-20 knots, but normally operating in the 8-10 knot range. The sail will be approximately 30ft span and 5ft chord with a rectangular planform. The aerofoil section I am presently using is an Eppler E395 12.5%.
Is this a suitable aerofoil for this purpose, or would something else be more appropriate? Although I have good boating knowledge, my aeronautical experience is limited to building model aircraft, so may be lost if answers get too technical.
Thanks in anticipation.
Solidsail.
Is this a suitable aerofoil for this purpose, or would something else be more appropriate? Although I have good boating knowledge, my aeronautical experience is limited to building model aircraft, so may be lost if answers get too technical.
Thanks in anticipation.
Solidsail.





RE: Thick sail
Also, would you consider building some taper in your sail? Remember, a rectangular planform means the lift is roughly equal along the span, maybe even a little less at the base because of wind interference around the boat. So you'll have to build a stronger mast and shroud lines compared to having a tapered sail.
If you've already thought these through, please enlighten me. I'm just a modeler, and former cat-sailer too (never used the BS-AE)!
RE: Thick sail
Thanks for the reply.
I've designed a reversible version of this aerofoil, so it works both ways. It's a bit of a complicated mechanism at the moment, but I'm working on a simpler version.
I'm intending to mount the sail on the existing mast, which was designed for a much bigger conventional sail. I'm more concerned with getting the maximun power from the new wing than reducing the forces.
RE: Thick sail
Once you've determined the airfoil you're looking for, search the NACA reports at http://naca.larc.nasa.gov/ for lift and drag characteristics, as well as pitching moments. There, you should at least find something close enough to extrapolate from.
RE: Thick sail
Best of luck,
Mike
RE: Thick sail
How far along have you come with your design?
STF
RE: Thick sail
Something like a standard bermuda sail shape, but shorter fore and aft, with the advantages of higher performance than a standard Bermuda rig. You should also be able to jibe quite happily, since the sorter boom won't put as much strain on your rigging or tend to knock your brains out!
Have you considered placing the leading edge ahead of the mast and having the mast at the thickest part of the cord? Just an idea, but it would provide a more streamlined setup overall.
Regards
John
RE: Thick sail
Thanks for asking.
Mike
RE: Thick sail
John
RE: Thick sail
STF
RE: Thick sail
If you get a copy of Abbott & Von Doenhoff's Theory of Wing Sections, you might find some relevant data. An airfoil code like XFOIL might help, too. Another book by Domasch, Sherbey, and Connolly, Airplane Aerodynamics, would make the process of finding coefficients easier. TOWS is available at Amazon.com, and AA can be found on used-book sites, such as Alibris.com.
STF
RE: Thick sail
RE: Thick sail
I allow for the variable wind speed from surface of the water to the top of the mast through tapering the foil (Leading edge constant). It's relatively easy to do because when the foil is adjusted it adjusts in unison throughout the whole (Bottom to top) foil. So, The boundry layer near the surface through the top of the mast the force on the mast should be uniform thus maximizing lift.
regards,
Mike
RE: Thick sail