Constructing wings for boats might seem a little daunting to people familiar with sails, but in reality it is not difficult.
The method I use would be familiar to anyone who has made flying model aircraft or even fullsize light aircraft that use traditional wooden frame with cloth covering.
Cloth wing coverings, both for models and fullsize aircraft are being superseded nowadays by plastic films which after covering, are shrunk by heat to produce a drumtight finish.
These wings can withstand any forces they might encounter from the wind, when they are in use, but are less durable than sails when handled by people. You just have to be careful and don’t stand on them!
You might think that heat-shrink plastic film coverings primarily produced for model aircraft would be unsuitable for the larger kind of sailing wings, but I have found them surprisingly strong and have never so far torn any.
As an example: the covering on a sailing wing I made over six years ago is still perfectly usable. I also have model wings over twenty years old which are still ok. Admittedly, these wings have been kept indoors when not in use. How they would fair in the open has not been proven, but even if they only lasted one season, it is not difficult to re-cover a wing and quite quick too.
The design is based on the classic “D” box for strength, and everything comes from this. The “D” box is the area between the leading edge and the thickest part of the aerofoil where the mainspar is. This area is covered with thin plywood and therefore forms a “D” shaped tube upon which the rest of the wing is attached.
Mainspar is plywood (with lightening holes).
Leading edge is balsa (this makes it easy to carve for good aerofoil shape)
“D” box filling is polystyrene foam (cut to shape with hot wire cutter).
Leading edge covering is 1mm ply.
Trailing edge is pine strip.
Battens are also smaller pine strip.
Everything is glued with PVA adhesive which is particularly good for attaching the plywood covering to the polystyrene foam. This adhesive may be thinned with water where necessary.
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