SHEETING ANGLES FOR SINGLE SAIL BOATS
Hi Michael,

Your question isn’t really about lug sails. But it is a general question about the front sail in any boat. As you only have one sail … it is the front one :)

Many people get confused by sails with mast and boom on boats with a single sail. They might be used to sloops and want to bring the mainsail into the middle using a bridle. This is wrong. A sloop sailor would never do it with their front sail – the Jib. So the front sail, even if it has a boom and is attached to a mast needs to be at the correct angle for a jib.

For most boats the angle of the lower part of the front sail and boom for going upwind is normally about 10 degrees. It is well worth measuring this out from the downhaul position on the deck of the SCAMP. It is a really important angle. At the centre is bad for the front sail of any boat. Having an idea of the angle will give you a feeling for whether you are pointing high or trying to get speed.

When there are waves and gusts in the wind the boom will have to move outside this angle to the point where the boat has good speed and heel is not excessive. Then you can try to bring the sail in closer gradually, being careful to watch the tell tales to make sure they keep working.

Now to be more specific about your situation – front sail with a boom and a rope traveller.

We want he boom out at that 10 degrees and the mainsheet attachment below. On a balance lug mainsheet controls twist much more powerfully than the downhaul, and the downhaul takes over when the sail is well eased = in any but very light winds the downhaul needs to be VERY tight. So in general we want the traveller block to slide from side to side.

The mainsheet will only control twist if the block on the traveller is more or less under the end of the boom.

Now a little trick. If the ends of the traveller are at or inside the 10 degree angles you (mark with tape or marker) then the traveller should be tight so the block goes right to the ends of the traveller.

If the 10 degree line is inside the ends of the traveller then the traveller should be a little loose – this allows the block to slide inboard from the end of the traveller. It also allows you to position the traveller block by hand if you have normal mainsheet tension. The block will stay there until you have to loosen mainsheet tension.

The mainsheet is much more powerful at controlling twist than the downhaul. But on the Balance Lug the downhaul is OK at controlling twist when the sail is eased as you suggest.

Hope this helps you visualise what is happening.

Michael Storer