Second Thoughts (JohnB)
From the depths of my armchair, or if I am honest, the sloth of my retirement, I have been looking at the performance curves of various rigs. The Gaff rig appears to me, on second thoughts, to be well worth considering for a sailing canoe. Although it apparently lacks the performance of a Bermudan sail over the last twenty or so degrees, its lower centre of effort may well make it more able to be used at full power. Our little boats are short of the support that a higher rig might need.
Once off the wind a little the Gaff really comes into its own, a huge surge of power which it maintains for the next eighty degrees. This could be a great advantage.
The power hump has been explained by modern research and is a result of the steeply sloping gaff. It's called the roll over vortex. These advantages should be available with a lower centre of effort and a lower overturning force. It's interesting too to note that the very high aspect ratio Bermudan sail, 9, does not develop a markedly higher power curve than that of AR 6.
With a generous leading edge sleeve of some 12 or 18 inches on the mast and the gaff, the windward performance of the sail could probably be improved. Again, wind tunnel research suggests that the losses are mainly due to turbulence downstream of the mast and spar. There are further virtues to this rig. When Bermudan sails were first introduced in the early 1900's, sailors complained of the lack of control over the sail shape. The angle of the gaff has a considerable control over the shape of the sail, an aspect we do not pay enough attention to.
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