August 2008

During the August 2008 OCSG Loch Tummel meet, I had a chance to discuss various ideas with DaveS on how to improve my Raptor's performance, particularly into the wind. He had seen my website photos of EddieVB's boat and traveller system but thought that marked improvements could be made in another way. The main problem that he saw with the Raptor's rigging was that the outhaul line has to fulfill two functions, to unfurl the sail and to tension the sail's leech, and he doesn't believe both functions can be done well. In order to tension the leech, it is necessary to tension the outhaul line either by unfurling the sail entirely and pulling against the mast or by cleating the furling line and pulling against it with the unfurling line. The leech is then further tensioned by pulling down on the boom with the mainsheet. The result of this leech tensioning is that the foot of the sail is pulled flat and loses its aerofoil aspect and hence its power, while the head of the sail retains its shape and power. This makes the Raptor more liable to capsize, since most of the drive is coming from the upper part of the sail, where it has the most heeling effect. If the leech is not tensioned, the sail will twist and "spill" air, with a resultant loss in power.

DaveS thought it important to retain the Raptor's very useful roller furling sail system, so wanted to devise some way of tensioning the sail leech while still allowing the foot of the sail to have some shape. A brainstorming session was held while at the Loch Tummel meet, with input from DaveP, SteveR and JeffB. In the end, JeffB devised a system which everyone agreed was the most elegant solution to my problem. Initially, a 4 mm line was tied to the main sheet block eye strap near the end of the boom, routed through the grommet at the sail clew, down through a block tied to the boom just aft of the fairleads, and forward to another block attached to the upper part of the step. DaveS will mount a small cam cleat in front of the cockpit on the port side to allow this line to be cleated, but during the Tummel meet I used the main sheet cam cleat for this purpose and simply held the main sheet, without cleating.

I tried this initial setup during a trip to the east of the loch on Monday afternoon and found a couple of problems with it. Firstly the angle of the line from the block to the cleat was too steep, making it difficult to cleat and liable to pull out. Secondly, when on a starboard tack, the leech tensioning line trapped the furling line against the mast step.

As a result of these two problems, I moved the mast step block down to the port side of the metal bridle on the mast step, where the two outhaul line blocks and one mainsheet block are attached. This location provided a shallower angle to the cleat and meant the leech line didn't interfere with the other mast step lines. I also attached a shackle to the sail clew, allowing a straighter run for the leech tensioning line.

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