Old as Dirt!
Join Date: Nov 2008
Location: Tampa Bay Area
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I just realized the in my earlier post I referred to a "solid 3-1/2" pole when I should have said "single 3-1/2" pole". With the Forespar "pole", there are actually two poles, the outer being 3-1/2" and the inner--extendable portion--3". A single 3" pole would likely do although for the little difference in cost, I'd be incline to used the larger diameter pole but you could likely get away with 3". If your sail is 120% of the J, the pole should be of that length as well or perhaps somewhat longer, considering that it will be extending from the mast. Ideally one would want to match the length from the mast to the tangent point of the clue with the sail forming a smooth flat arc about the headstay (think of the shape of the sail running nearly dead-down-wind when the leach of the sail actually is serving as its "leading edge"). So long as you are using a topping lift and foreguy, a partial furl in the sail won't matter much to the sail.
As for the loading on the pole. if you set up a vector diagram of the sail's clue with due regard for the angle and magnitude of sheet loading, you'll be (or might be) surprised at the amount of compression loading on the pole. As a strut in compression over a fairly long unbraced length, one wants as much radius of gyration as possible hence larger diameter, lighter wall, has it over smaller diameter, heavier wall, but that will likely really only become an issue in fairly strong winds when most people will be disinclined to use a pole anyway.
"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."