TOPIC:

HI



Having changed a few things over the winter..... I put on weight... I need to increase the power ratio to windward and on reaches. I have no problem in increasing the power for reaches when the settings are right for beating but in order to increase power all round should i lenghten or shorten the spreaders, or angle forward/back?



Maybe there is no "magic" answer but it would be nice.



Derek Gibbon

7176

Derek, My understanding is that you lengthen the spreaders to stiffen the rig and increase power. I got this from a copy of a McNamara article in Y&Y many years ago, Trev

For maximum power the mast needs to be held in the shape that the sailmaker designed the sails for.

In general - longer spreaders stiffen the mast athwart-ship, raking them further forward stiffens the mast fore and aft.

However it is never quite as simple as that, because rig tension also plays a part: - If you have spreaders that are too long with a low rig tension, the spreaders can actually increase side bend (the wrong way) by pushing the middle of the mast to leeward thus closing the jib slot.
- Similarly if you have the spreaders raked too far forward and you apply rig tension you can invert the mast which will mess up the shape of the main (and the jib slot) by putting too much fullness in the front.
Things are further complicated by wanting to control pre-bend, with the spreaders raked forward it is more difficult to put prebend into the rig, so light airs sailing is compromised, but the amount of pre-bend required will depend on your sails.
As with many things it is a compromise. Start with the settings in the tuning guide for your sails and then make small adjustments at a time and record the results.

JohnW2008-07-08 10:13:24