Do a print out of the pages involved with the "How to re cut a sail board sail" www.seabreeze.com.au/forums/Land-Yacht-Sailing/Sail-making/How-I-recut-sailboard-sails-to-suit-landyachts/

Also give him a link to that on the forum so he can have a read through for himself.

When we had the "Sandpiper" sails made we actually went to a sail maker that was happy to come out for a sail BEFORE he started to make them..... that alone changed his thoughts towards land yacht sails and how they were constructed.

15 minutes sailing a land yacht for a sail maker might save you 2-3 sails of experimentation before he gets it right.
(put on a BBQ and a carton of beer, bring his wife / kids along if that's what it takes)

3x sails @ $500+ OR 15 minutes sailing + BBQ + Beer = GREAT day out Bargain !!!!!!

I get the general gist of what you want and could suggest that you try what I had done to my sails both for the mini (Schrodinger's Cat) and and Occum's Razor.
That is I followed Paul's Formula though I had to use my own Judgement for the Sail Head s and Foot s. His curve has proved to be a very effective and as for any Looseness in the fore part of the sail pre-Luff there shouldn't be any. The sail should Sheet Down Clean and tight, any shape is gained through wind Pressure and Batten Taper. Least ways this is what I gleaned from Paul and my Sail Maker.

What I found under Sail is that these Sails become very active at around 12 to 15 knots and accelerate heavily. As a qualified Sail Maker you guy is used to making Sails that Require a great deal of power/Lift to overcome the Drag of the water, you have no such problem with a Land Yacht or very little to speak of. Therefore you require very little Power/Lift to move you and your sail gains it's power with speed i.e The Flatter the Faster.






Once again I take the liberty of telling you you should Print the pic out A4 and show it to the SM. He will get the idea. Flat as a Bed Sheet made of Silk.
Ron

PS The top one is for SC and the bottom one is OR.

sabydent is wanting to start from scratch for a sail....... not go down the recycle path for sails (he's done that on his first yacht)
The conversion of sailboard sails is far from ideal, yes they work but a sail designed from scratch for the exact purpose works a hell of a lot better, and that's what sabydent is trying to do.

As I said get a sail maker involved very early in the project as we did with the "Sandpiper" and often a new person into the sail maker industry works better as they have very few preconceived ideas of how a sail should be and often has an open mind. There seems to be very few innovations in sail design over recent years of land yacht sails unlike whats happening on the water sailing area.
Do a google search on 'Speed sails' and have a look at some of the designs that are happening rather than the 15-20 year old sails that are being used from the tip currently use on land yachts.

Have a look at birds that soar the ocean, or sail plane gliders, or high performance prop powered planes and see if you can see any common things that exist in the shape and designs of the wings...... take your time research the subject and understand VERY well how a sail works.
Ignore jet powered plane as wing shapes often are that shape because they are nearing the speed of sound where other factors come into to play.

Ron the discussions you had with your sail maker was how to best use / re cut the sail you already had not build it from scratch.

Sail performance comes from many things including draft, the position of that draft, the aspect ratio, the overall profile and most of those things were already in place when the original sail was made.

Getting an open minded sail maker out to use a yacht early in sail development is virtually essential unless you wish to spend lots of $$$$ on sails.

If you are into SERIOUS reading on the subject I would recommend the book
aero-hydrodynamics-of-sailing by the author Czeslaw A. Marchaj (ISBN 0-229-98652-8) WARNING!!!! it is HEAVY reading

You might be able to down load an e-book version here
ww1.ebookbrowse.com

When you were wanting advice on re-cutting your sail the subject of new sails never came up..... The advice you were after was given, successfully.
So if you were going for a custom made new sail probably a lower CE would be more beneficial and probably an elliptical tip to minimise drag.... Just these 2 things would add to stability and slightly increase your speed.

sabydents request was totally different from yours.