sail balance in a gaff cutter

[lilianroyle]

I have a 31 ft smack. The mainsail is 260 square feet, the staysail 60 square feet and the flying jib 90 square feet. The boat has too much weather helm. With two reefs in the main it is reasonably balanced but obviously I don't want to reef the main just to balance the helm regardless of the wind strength. I have played around with the balast and improved the situation a bit but I now want to get a larger jib for winds up say up to force 4. Can anyone give me an idea of the kind of area I should be thinking about for a fine weather jib for a boat of this kind
many thanks
Pete

 

[Plum]

Here is a thought: work out the centre of effort (area) of your jib, staysail and main, then, by taking moments about, say, the mast, work out the position of the combined centre of effort. Now, do this all again for the situation with the two reefs in the main. The result will be the existing centre of effort with the weatherhelm and the ideal centre of effort with a balanced helm. Now, with this information you should be able to work out how big the jib should be to get the centre of effort in the ideal position without the two reefs in the main.

If that is a bit too technical, borrow a bigger jib..........

 

[Strathglass]

The best way if possible would be to add a bowsprit. This would enable you to fit a larger foresail. Or can you set the mast further forward? A quick way to check the trim is to make a card models of the outline side view of your yacht including the hull rudder, keel and sails. The first one with the sails in the reefed position which is when you find the helm correct.
With the card cutout lying on it's side, find the point of balance longitudnally along the hull. Then experiment with a full main cutout and different foresail sizes until it balances at the same point. You then know the size of jib you require. This will give you some idea of how much additional sail area you require.
Iain

 

[brian_neale]

Can you clarify what you mean by "too much weather helm"? Is this on the wind, or off the wind? What wind strengths cause the problems? The issue here is that a gaffer tends to get fairly heavy on the helm with the wind anywhere aft of abeam, because the centre of effort of the main has swung well off the centreline of the boat. Common ways to avoid this are to pull down a reef, or to let the main out a little too far and let the forward part of it lift a little. Surprising just how much this can ease the helm, and because we are not usually talking race-tuned thoroughbreds here, performance is barely affected.

The sail dimensions that you give sound reasonable to me, assuming that you have a decent length bowsprit to get the jib well outboard.

Gaffers seem to have different views on light weather sails. Some use a lightweight jib (maybe a second-hand cruising chute?); some go for a large "tow staysail" which has a big overlap on the main. Can be difficult to get it to set, but some skippers swear by them.

(I have just taken delivery of a 28' gaff cutter, after sailing a 16' gaffer for a few years, by the way, so can sympathise! Now starting to develop even stronger arm muscles)

 

[Jacket]

have you tried talking to one of the smaller sailmakers who speciallise in gaff rigged boats? They've probably encountered this sort of problem before, and are normally happy to talk over your problems.

 

[brian_neale]

Good point - sailmakers who understand gaff rig include James Lawrence (based in Maldon, I believe, so understands the East Coast style!) and SKB near Falmouth - David Spargo (the S in SKB) has raced Falmouth working boats himself.