Join Date: Feb 2000
Location: Annapolis, Md
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Behind mast roller reefing
There are a number of potentially damning issues with using a behind the mast furler on a wooden spar. In order for a behind the mast furler to work the furler gets installed with a separation of from the mast. It is also placed under a lot of tension in order to prevent the stay from sagging so far that the furler binds and experiences too much wear or in the worst case binds. This combination of loads really places a lot more bending and compression stress on a mast in a manner that concentrates these loads equally at the masthead and gooseneck. Wooden spars are designed and tapered to reflect loadings that are distributed along the luff with the center of their forces roughly 1/3 of the luff above the boom. Similarly wooden booms are generally designed to take distributed loads rather than the kinds of concentrated loadings involved in the single point tack attachment of a roller furling mainsail. In other words, in most cases a wooden spar would not be sturdy enough for the loads involved with a furling mainsail.
The unlikeliness that your spars would withstand the loading in heavy air not withstanding, you will also experience a decrease in performance and the risk of ending up with a lee helm, a pretty dangerous condition that should be avoided.
I would suggest going to a dutchman or lazy jack system with perhaps a downhaul to bring the sail down more easily.