sail size: look at boats of similar size, shape, and displacement. there
are two guidelines and one caution. first, in light winds you need 2 to
2.25 times the wetted surface of the hull. second, in stronger winds you
need 1 to 1.3 times the square root of the sail area divided by the cube
root of the displacement. make it closer to 1.3 for small boats. the
caution is not to put so much sail on that a nice breeze will blow the
boat over. there's no good way of calculating that. you have to look at
other boats. some people put reef points in their sails to make them
smaller when the wind blows stronger but small dingys usually don't have
them because nobody's supposed to sail boats that small in strong winds.
OTOH I've seen lots of racing dingys get blown over in strong winds. the
sail on my 11 ft one person skiff is 42 sq ft. I put reef points in it but
never use them.

shape: the aspect ratio of a triangular sail is the square of the height
divided by the sail area and should be about 4. I don't think you will
have to cut your 5 ft bolt into panels. you can put a curve in the edges.
use the calculations for the sprit sail on my website. they are good for
trianglular sails too.

reinforcing: add triangles up to 1 ft of cloth at all 3 corners to make
the sail double thick there. you can sew rope along the forward and bottom
edges of the sail.

mast attachment: I like a mast sleeve (like on a Laser) but you can sew
loops of sail cloth or light line to the front of the sail instead, one
every 12" or so. the air escaping around the mast on these sails reduces
power a bit. you don't see loops on boat used for racing. for pleasure
sailing it doesn't matter.

boom: not needed on a really small boat. if the bottom of the sail is more
than 5 ft consider a loose footed boom where the sail is only attached at
the front and back ends of the boom. the boom will hold the sail out
better when the sail is out ot the side.

that's the basics. you sould be able to find info in books at the public
library.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

William R. Watt ) writes:

shape: ..... I don't think you will
have to cut your 5 ft bolt into panels.

woops. I was thinking sprit sail here. You will have to make your sail
wider than 5 ft. The aspect ratio simplifies to twice the height divided
by the width. A 5 ft wide sail with and aspect ratio of 4 gives a 10 ft
high sail and only 25 sq ft, much too small. Increase the aspect ratio to
5 and the sail is 12.5 ft high and still only 31 sq ft. Looks like you'll
have to make the sail wider than the 5 ft bolt of cloth by cutting into
panels. You might want to include a boom in the rig.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

try looking up a freeware program called sailcut. it is a perfect
program for projects like this.

William R. Watt wrote:

William R. Watt ) writes:



shape: ..... I don't think you will
have to cut your 5 ft bolt into panels.



woops. I was thinking sprit sail here. You will have to make your sail
wider than 5 ft. The aspect ratio simplifies to twice the height divided
by the width. A 5 ft wide sail with and aspect ratio of 4 gives a 10 ft
high sail and only 25 sq ft, much too small. Increase the aspect ratio to
5 and the sail is 12.5 ft high and still only 31 sq ft. Looks like you'll
have to make the sail wider than the 5 ft bolt of cloth by cutting into
panels. You might want to include a boom in the rig.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned



--
remove "abcde" from e-mail address to reply

"I think it would be a good idea."
Mahatma Gandhi
http://www.quotationspage.com/quotes/Mahatma_Gandhi/ (1869 -
1948), when asked what he thought of Western civilization