sail balance

[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

 

[Peterduck]

It's a nearly impossible ask with the information that you have given. You also need the Centre of the Lateral Area of the hull, the centres of the area of each sail and its position before or aft of the centre of the lateral area of the hull. The combined Centre of Effort for all sails should be about 10 % of the waterline length ahead of the Centre of the Lateral Area of the hull. Even then, it is likely that this position may be slightly out. One of the imponderables is that the position of the Centre of Lateral Resistance [the point about which the boat balances when under sail] actually varies according to the boat's speed through the water. Now, add to that the effect of heeling, where the curvature of the hull on the leeward side is much greater than that on the windward side, causing the boat to round up, and you are starting to get some inkling of the complexity of the problem. A common problem is the shortening of the bowsprit for one reason or another. a 30ft smack would expect to have a 10 -15ft bowsprit. This upsets the whole balance of the boat. Find a sailmaker with an interest in Gaff Rig, and talk to him about it.
Peter.

 

[Guest]

I have a replica of the Spray with a 16 ft bowsprit and also a large Gaff main the jibs are set on a traveller on the bowsprit which allows it to be moved in and out to balance any reefing in the main. size of jib flown depends on conditions. I found on a voyage from South Africa the boat sailed itself for days on end once the correct balance was achieved