Hi Gardner,
I am also getting interested in building some form of 'soft wing'. Comments below.
--- In harryproa@yahoogroups.com.au, Gardner Pomper <gardner@...> wrote:
>
> All this discussion has made me anxious to try something. Since I am in the
> process of trying to figure out how to get a rig on my plywood proa, I
> thought that I might combine the efforts. I have a couple questions (of
> course) on how to calculate the shapes involved. Here is a description:
>
> I would like to try a soft wing sail with a short gaff rig and both top and
> bottom plates.
Wow I'm having trouble imagining wing + gaff rig + end plates... sounds very interesting.
> I would like to try a version of this on my plywood proa, but
> I don't have all the measuremts fro that, so let me use ToyyoT as an
> example.
>
> Luff: 32 ft
> Foot: 8 ft
> Head: 6 ft
> sail area: 224 sq ft
> aspect ratio: 4.5
>
> I would like to use Tom Speers paper for the foil, with a 30% ellipse as the
> wing part.
Is this the paper you refer to? if so I have been studying this also - and liking 30% - although I can't say why, just looks right!
http://www.tspeer.com/Wingmasts/teardropPaper.htm
> That would make the wing section 2.4 ft long. I would make this
> dimension constant all the way up, so that the trailing flat bit varies from
> 5.5' at the foot to 3.5' at the head. Both the head and foot endplates will
> be cut to extend 6" beyond the sail.
>
> So, given that this sail will rotate, the idea is to trim it so that it is
> always at the correct angle of attack. From
> http://www.kastenmarine.com/gaff_rig.htm, I would estimate that the rig will
> have a L/D of about 7.5 at an angle of attack of 10 degrees. So, how do I
> find the wing shape, as specified by Speer for a 30% elliptical wing?
>
> - Gardner
>
To your question - do you want the actual numbers for a wing shape? If so I found some for the Clark Y foil Tom mentions in the paper. I found these on a site that has the coordinates for lots of different profiles (hope I can re-locate that!). The big unknown is which profile to choose? I just want something simple (idiot proof) so was going to go with the Clark...
cheers Dave