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Question from one of our visitors....can you help?
I live in France on the Atlantic coast, and want to convert my 6meter traditional wooden flat bottomed work boat into a sailboat. I fish in the Bay of “Marennes” which empties at each low tide. Traditionally all the old workboats had a centerboard well which takes up a lot of space, and requires a major rebuild of the boat if I want to convert the boat to a sailboat.
I have an aluminum mast and sails as well as the tiller /rudder from an old Fireball racing dinghy. That ought to be enough sail to do the job for fishing.
The double leeboard design interests me as an easy, efficient way to do this. It sees to me that the lee side board serves to prevent side slip under the force of the sail when broadreaching, and the windward board helps to provide resistance to heeling (its resistance will be a function of the boat speed), which is very prevalent on a flat bottomed boat.
By definition, the lee side board will be pushed against the hull of the boat, creating a traction force at the pivot point, and compression at the hull. This board will be self stable. The windward board will have the same forces under heeling, but under certain conditions I could imagine a problem at the pivot point as it could be pulled away from the hull and its only support is the pivot. One Idea I have is to design the leeboard in such a way that the hydrodynamics of the foil force the board into contact with the hull at all times. The faster the boats speed, the harder the board is pushed against the hull. Unfortunately, the drag increases as well.
Another idea I have is to link the two boards at the tip with a small free floating airfoil that will insure that each board is under two point contact. Like a spoiler on a car. The foil will go up against the bottom when the boards are retracted (lucky me, the bottom is flat!).
My only real hitch is that the hull is not vertical, but tapered from the gunwales to the waterline, which means that the boards will not be in a true vertical in the water. I could bent the boards at the waterline on down so that the unwetted surface of the board is always against the hull, or fit a spacer block against the hull at the bottom to allow use of a flat board.
This is where I am in my thinking. Do you have any advice, or ideas that could help me?
Disclaimer: Always wear life preservers, drink and party responsibly, sail at your own risk, and please pass the word that leeboard sailing is now a blast from the past that will soon be in the news as being the latest sailing craze.