Thursday, March 10, 2011

High-peaked Gaffs

Some of you may have noticed that all of my gaff sail plans have a short hoist (luff) and a long, high-peaked gaff. To many, this is a somewhat strange-looking shape compared with the more commonly seen longer luff, shorter and lower peaked gaff.

Pegasus 18.5

So, why do I do it that way?

The main reason is to keep the mast as short as possible. This may not be such an issue in a boat which sits on a mooring, but for a trailer boat, every inch you can remove from the length of the mast is important. Added length in the gaff means reduced length in the mast - although there are diminishing returns, as the peak halyard needs to intersect the gaff at as close to a right-angle as practical. This is so that the gaff stands well, with minimum sag, when under a weight of wind - in the process reducing twist in the sail. The result is that the mast needs to project quite a distance above the gaff jaws, and a quick glance through your boat books will show that many designers and builders make the mast too short above the jaws, and the halyard then works at a very inefficient angle. This is one of the reasons that gaff rigs have a bad name for windward work.

The second reason for my use of long, high-peaked gaffs is that the light, flexible gaff tends to bow around the halyard attachment point when the wind gusts, automatically flattening the sail at just the right time. Also, by tweaking the peak halyard, you can produce very effective sail shape adjustments when changing point-of-sail, or during varying wind conditions. The high-tech racing boats spend hundreds of thousands doing this with carbon-fibre and stainless steel - here we can do it (in a cruder, but effective way) using home-made wooden spars and a bit of line.

I frequently draw a tiny, short-luffed jib for these rigs. The short luff and small sail area means that the little sails stand well, even though the masts have no shrouds or backstays of any sort. However, the effect of the jib is remarkable, as it smooths the airflow around the section of the sail attached to the bulky , turbulence-inducing mast. The jibs are so small that the rig can be used with, or without the jib, and will still balance well.


  1. Hey Ross, just found your blog - very nice! I was re-visiting a sprit rig for my Dierking-designed outrigger. Turns out he's been using one in Fiji. I'll stitch one up this summer-looks like it works well.

  2. Dear Charlie,

    Thanks a lot for the comment. I hope things are working out for you, and I've been thinking about you on odd occasions. I recently had the opportunity to do some gliding once again - aerotow was tricky, but the thermalling was great. The Laqatois (not certain of the spelling) in Papua New Guinea use sprit rigs for racing, with the best sails made down here in Australia. Keep in touch - hope all is well. Ross