As I turn around making small sails for my Mini, I will dump here some findings and ideas. I don't know if I will go the complete to doing the sails... Let's see.

Why:
Land yacht sails is a niche market. Masts are not as standardized as for windsurf sails. So LY sails have to be considered as one-off variations on a theme. Not many sailmakers. Sails at the end can be expensive. There not a significant second hand market in my country. And second had sails may not fit my mast. For hobbyist, there is a rationale for DIY.

Two different path (at least):
There is good success in tinkering on windsurf sails, with 2 different approaches:
- use the sail as is by adapting the rig: straight mast + cuni + high boom,
- reusing the materials, be recutting the sail to fit the geometry and operation of classic LY.

Primary driver for windsurf sails is the downhaul to bend the mast <=> lot of tension on the mast panel
Primary driver for LY sails is the mainsheet and leach tension to bend the mast <=> lot of tension in the leach.

I will design a LY sail, where main control is the mainsheet. Recutting the Windsurf sail, just reusing the materials.

Masts:
Classic are Alu masts. However there is good success with Windsurf masts. Here SDM low carbon masts are cheap, especially in common length like 430-460. People turn to RDM masts with much higher Carbon percentage (80%, 90-100%). So large second hand market for 430-460 C30 masts. They are as stiff as C80 or C100. They are just heavier (not a problem in LY) as not as fast (return slower to initial position after gust). Sailworks has good success with their Mini Skeeter sails on a Carbon mast (quite long = 520cm).

So here, it is more easy to find a carbon mast, than to find suitable alu in needed variant and diameters. Windsurf masts are quite consistent. So what you design could be used more easily by somebody else on the other side of the planet.

Seems that they only need a internal reinforcement tube on 75-100 cm. No external reinforcement needed.

The longer the mast, the stiffer they are. IMCS increases with lentgh. I'm on the light side. I will prefer a small mast on a longer extension, for more tolerance to gusts.

Shape of LY sails - retro- engineering will next chapter.

From Windsurf sail to Land Yach sail:
- have to modify the luff curve, as not operating in same conditions as during windsurf. Especially much less downhaul,
- have to cut the bottom to fit the LY boom,
- try to keep the Head and Clew, and their reinforcements,
- try to recycle as much cloth, and stuff like battens, batten sleeves, full pocket,
- may need to build a specific "mast panel".

Looking at R&J sails and Sailworks mini skeeter sails, I think that a 25% mast panel should be OK. This minimizes a bit the new stuff compared to the recycled ones.

In LY sails, the loads seem to be driven by the clew and or the boom. This looks illustrated by the radial cut from Frog sails, Libre sails, some seagull sails... This is very LY specific. It won't be possible to achieve when refurbishing windsurf sails.

kennatt said..
not sure but were the WS sails, just being recut to suit the bend of a standard LY ally mast. If you are going to use a standard W S mast then would you need to recut the luff curve. Would'nt the WS sail be ok for the mast,and only need the base altering ie straight to accept standard LY boom You could adjust the cut to suit the reduction in size,
.I've used small 3.5 WS with open top sails on masts rated for 5.3s and although a bit too stiff still worked reasonably well,lot harder to downhaul but still set ok.Couldn't afford four of five masts in the early days,until I recieved sponsership from local retailer then had a mast for each sail 3.5 to 10.5 formulae . (seems like a lifetime away now) Well I supose 35 years ago is a life time for some.
I see you have a Plume,think they are centre sheeted(Or maybe not) If they are then would you need to consider that into your calculations. There is a marked difference if the pressure on the sail from rear and centre sheeting. (I'm at present in long term expirement into the performace of both sheeting point's it's amazing the different feel they give)

Very interesting read up ,keep at it will be interesting to see the outcome'

My Plumekart is not "center sheeting" (www.plumekart.com).

Practicing LY, I discover aspects that I had not noticed initially, as never done (seen) like that in sail boats. Example: as the tack is not attached to the mast with a Gooseneck, then the seeting point mosex the tack fore and aft, modifying the bottom shape of the sail quite a lot... Definitively, native LY sails are not set as windsurfer (WS) ones.

Condition for reusability / recutting, from what I understand, is to find WS sails:
- with little seam shape (flat mould, around 2%-3% draft),
- with "High" aspect ratio (high/width). I think that sails fom end of the 1990s, early 2000 have higher aspect ratio than today, which should be a good feature.

This forum feedback, is that it works ! Good !

How much do those Plumekarts go for and are they readily available or build to order?

rtz said..
How much do those Plumekarts go for and are they readily available or build to order?

I bought it through that website: www.plumekart.com/ . The young guy plays the salesman role, but does not looks to me really proficient about details of the design and usage. The designer, Pierre Cornuwell is.

The catalogue price is around 3200? I think. Early in the year, they proposed reduce prices, so I paid about 2300?. My understanding is that they have a few built. I'm very happy with the chassis. Not somuch with the sail mast combination. There seems to be a flaw somewhere.

Yes, those minis are not designed for centered sheeting. Even the competition models from that designer have a similar pulleys arrangement. By the way, I think that finally I should have taken a competition model. Pictures here: www.facebook.com/PlumeCharavoile/photos/?ref=page_internal

I had taken few measures on my 7.0 windsurf foiling sail (power at bottom + flat top + little pretwist + designed for CC windsurf mast). It gives the curves below. I like them:

Hi there, its been awhile since I've been on the forum.JMF1 you may need to factor in the wind speed over the sail on WS v LY sails, a WS sail is 'nominally set' for a windspeed +/- a variation on the water. for example 15 knots +/- 5 knots this actually is a VERY small window of windspeed the sail needs to cope with.
A LY may be sailing in 15 knots of wind +/- 5 knots then you need to add apparent windspeed to that, a Mini LY may do 3-4 times the actual windspeed so a sail needs a workable window of shape from 15knots - 45/50 knots of wind almost hurricane force. And to think I about it the rig / sail needs to adjust from a low wind speed to a high wind speed with minimal adjustments from the pilot while sailing.