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Altering the luff curve for a stiff mast tip.

	OK. here goes. This is a pic looking at the head of my 4.0 wave sail. I was quite happy with it until I got a new Gaastra RDM mast. The mast is quite stiff at the top and there was more leech tension than I would like. you can see there is only a hint of looseness between the top 2 battens.
	Another pic of the same. The silvery cloth is a pentex scrim as used in offshore racing yachts if they can afford it. Again you can see there is not much looseness or pre twist.
	Now things get interesting. I have taken the sleeve and luff tape off. To slaken the leech I am going to reduce the curveature of the luff above the batten above the boom. I have taken 20mm off with the max difference at the 2nd batten down. You can see the bit I have cut off lying allongside. The head does not suddenly curve in as it looks its just the sail is not lying flat. The luff curve is nearly a straight line from the 2nd batten down upwards. I used a long flexy stick to fair the new curve in.
	I didn't want to cut any thing off the luff at the end of the batten above the boom but I did want to reduce the curve between the bottom 2 battens this is what you can see here. I took 5mm off. That now centers a lot of the luff curve on the batten above the boom which could give rotation problems on a normal mast but isn't a concideration with the RDM.
	And now its rebuilt and re rigged having broken my ribbs by using my chest to sleeve the mast. You can see it is looser than in the top pic.
	Just to show the new amont of pre twist. Just as I like it. so now it suits the mast nicely.
	But what will happen if I rig it on a very average mast? Here we see the sail rigged on a normal mast and now the leech is too loose
	Here is another pic of the sail on a normal mast and you can see the tension has dropped right off between the top 2 battens. I suppose it would be ok when it is really windy but I normally use this sail in force 8 to 10 anyway.

There ends a lesson in luffcurves. I hope this all makes sence it is quite a nice example of how the luff curve determins the whole character of the sail.