A Sail and Sailmakers thread...

Peg the sail out - tight luff so it goes flat, a tight string between top and bottom, and measure it at 200mm intervals along the luff.
Measure the mast bend every 200mm with a sail up the mast   - apply the magic correction factor and they will match.
Or... measure the mast bend, apply your correction factor and make the sail to suit at each point.
For an unstayed mast, fix the butt end, and hang weights off the top - easier to measure that way.



Edited by I luv Wight - 01 Apr 13 at 6:22pm

By who?
Not Hyde, nor that Elvstrom sail I had with the Blaze i don't recall.

When did they go out of fashion?

It's typical of one designs, well it's the same for everybody so who cares.

And I doubt anyone tunes battens these days either.

Some are tapered full length.
Most dinghy battens are softer in the context of the rest of the rig than windsurf battens so don't drive the shape so much, I.e the sail still holds its moulded shape regardless of the batten taper.
Un tapered are more the go at the top of sails anyhow where max depth 50%aft camber is ok.

As for luff curves and sails, my feeling on it is that most sailmakers will just mess about with te luff curve empirically on a known mast until they are happy. I think that at dinghy sizes very little true engineering goes into it as this would be more expensive than a few recuts.
Big leadmines a different story, when the sailmakers and rig guys make full structural models of every rigging component in a coupled model, loaded to mimic sailing loads, and Cfd aero models, and basically iterate around the loop until everything converges on the same answer. Obv sending the £200k main for a recut is a big hassle and expense,
And more boats and rigs are custom.
Good luck finding a production dinghy mast maker in the UK who will furnish you with actual engineering data for their spar.
If you're clever and do the correct tests you could derive the data, and generate deflection data that a sailmaker may or may not chose to use.

Originally posted by Daniel Holman I think that at dinghy sizes very little true engineering goes into it as this would be more expensive than a few recuts.

So how often does this go on then, and at what level? Presumably development loft and team/pro jock. Or would your average Solo sailor spec a recut?

I just lost a load of script in that last post, but the essence was the luff curve difference between the sails originally designed for tin masts which don't bend that much and the sails that go with carbon masts having a deeper curve, not that either curve is anything other than minimal compared to my world and one curve was twice the dept of the other, again an anomlay that just couldn't occur.
Obviously dinghy sails use predominantly broadseam shaping to obtain their shape, but there seems to be a trend to luff curve use with the increasing number of carbon masts, so I'm trying to work out how it's done without having the mast to hand pre bent on the bench.