Leeboard Detail
From BluWiki
[edit] Leeboard Detail
Really, this should be made from a solid piece of wood, but in reality, most people make it from a piece of 3/8ths inch plywood, possibly reinforced part way down with a 1x2. The leeboard sits on the side of the boat, rather than in the center, providing slightly less efficiency, but more than suitable for our needs. Almost all puddle ducks are leeboarded. The leeboard is what keeps the boat from sliding sideways in the water, which provides forward momentum. Since it works in tandem with the mast, it also must be extremely strong, and mounted properly. What many people don’t realize is that leeboards aren’t beneficial when sailing straight downwind, and their drag in the water is actually a hindrance, so a movable leeboard is to your advantage if you plan to race your boat.
The leeboard should be placed slightly forward of your center of effort, and counteracted by a large rudder. Both the leeboard and rudder should have at least 3.5 square feet of submerged surface area, which is roughly 16x32”. If your rudder is larger than the leeboard, so much the better. There was a discussion on the effect of leeboard and rudder drag upon the PDRacer vs. advantage of more surface area, and it was of the general opinion that greater surface area trumped the drag issue by several orders of magnitude.
You could build your boat with a centerboard, daggerboard, or keel, but that increases the complexity of the build by about 400% and fixes your center of lateral resistance, limiting your options on sails in the future. A leeboard by comparison can be made in about 10 minutes and infinitely adjusted, while providing 96% of the capability of it’s more complex cousins.
High aspect vs. Low Aspect
High aspect (long, skinny) leeboards are preferable to low aspect, but require significantly more technology and money to produce something of good quality. Their decreased drag doesn’t offset their difficulty or expense to make, and also can make it harder to sail in shallow lakes/ponds. You can produce a low aspect leeboard from a 24” or 16” by 48” section of a sheet of plywood that will work quite nicely, especially if the top 24” are reinforced.
