The leeboard is made per the drawing. If you want to stay very basic you can
get away with just rounding all the edges. If you want to make it a bit more
efficient you can taper it towards the leading and aft edges. Generally the
thickest point of a "foil," as they call them, is a third of the way
back from the leading edge. Some say leaving the trailing edge squared off is
more effective then rounded. That's a bit over my head, but if you want to
research it Jim Michalak is the guy to go to. Here are a couple of his
articles on leeboards:
http://marina.fortunecity.com/breakwater/274/1998/0615/index.htm#Pivoting Leeboard Design
Here's a quote from one of his recent newsletters:
The leeboard - always best to laminate it from thinner plywood to avoid
warpage. So if the leeboard is to finish at 3/4" thick you should make it
from two layers of 3/8" plywood or three layers of 1/4" plywood. What
I like to do is to make one lamination exactly the right size and the others a
bit oversized. Then apply lots of glue between the layers, place the layers on
top of each other on a flat surface and tap light nails through the stack so
that the layers can't slide around on each other. Then place something like
concrete blocks on the stack of layers to aply pressure. Then walk away until
the glue has set hard.
Trim the glued up leeboard blank to final shape. Then streamline the front
and aft edges that will flow through the water. Don't just round the edges with
a router bit. It doesn't have to be carved to a full airfoil shape but I would
suggest something like this:"
Read the whole thing here: http://homepages.apci.net/~michalak/
and browse his boat plans. He has some great ones, and very reasonably priced.
He also has some
great articles in his archives on leeboards and rudders.
The pivot bolt on Summer
placed the same distance from the aft edge and the top edge of the leeboard.
That distance will be 8" for external chine logs, and 6 1/2" for
internal or stitch and glue. The difference is because with external chine
logs the leeboard will bear against the gunwale, the pivot bolt spacer, and
the chine log when deployed. The other version is bolted flat against the side with a plastic spacer to
and touches the underside of the gunwale when deployed. It sort of "bump" stops against the gunwale in the down
A 3/4" thick backing plate of 3 pieces of the 3" wide ply is
fastened to the inside of the side, opposite the leeboard. This reinforces the pivot
bolt mounting point and distributes the forces over a wider area.
This leeboard idea I got from
my friend Richard Frye. It will work with internal chine logs or stitch
||I find no perceivable difference in the tacks. My theory
about why these simple leeboards work so well is that on the shallow
tack they are more vertical, and on the deeper tack they are more
slanted in the water.