Luckily there is a local seller here in Turku area. They even ordered a full roll of yellow Outguard (from Germany, I suppose) last year, when I needed only two meters for the top panel of the Joe 17's sail.

I decided to return the favour and buy some 25m of the same yellow fabric now for the sail of Galion 22.

In hand the 190 gms Outguard feels very, very strong. Plus it has a plentiful choice of colours :)

The strength and other technical details can be estimated from the data sheet, if one is capable of reading it. I am not...

Thank you all for your replies!

David wrote:

Conversely, 8 oz 100% cotton canvas has been making a comeback for medium weight car-camping tents, and I see that 3% shrinkage must be allowed for in this example. Other than that, so long as the cloth has been tightly woven and then proofed against rot and mildew, it will have an acceptable life. But if it is of high quality, I would have to query whether it would cost less than polyester cloth. 

This looks not bad. A pity that nobody has experience concerning the durability!

David wrote:

I think the best course for amateur sailmakers is to find those outlets in your own country that sell bankrupt stock, 'ends of lines' and cloth that is graded as 'second quality' because of cosmetic defects, not because of structural defects. In the UK, one such is englishseadog on eBay.co.uk who acquired the leftovers when the makers of Haywards sailcloth ceased production. Is there anyone similar in Germany or neighbouring countries, Frank? 

Thats a good hint! I have to dig a little bit more for remaining stock. The problem is that the internet and ebay in particular is full of cloth. Many of them lack of specification and trustworthy data about weight and material. Right now buying new cloth in Germany feels a little bit like gambling. I think it would be better to live on watersport enthusiastic islands like UK or NZ then here :)
 
But I found a cheap exemplar of "Make Your Own Sails by Bowker and Budd" and ordert it. Thats a good thing, thank you for that pointer!

Jami wrote:I'll be using Swela Outguard for the 25-28m2 sail I'm making for my Galion 22.

This seems very promising! Even more because of thats a german company and the price fits our budget. Now I m just not sure if 190gsm is enough weight for a 6panel 40sqm sail ....

Thanks David, although I'm surprised that you can comment on UV damage.  I didn't think you had ever kept a sail (or even particular sail planform) on a boat long enough for UV to be an issue!

David Tyler wrote:So it's the same chemical composition as Dyneema, then, which we know to be very abrasion- and UV- resistant. I suspect that Gore Tenara thread is similar. Could be worth a try, though I seem to remember coming across someone who had found it difficult to use, a long time ago.

Yep, its like Dyneema or Spectra. I think Tenara is a different material (fluoropolymer).  The sailrite site mentions that there can be some difficulties sewing with Tenara because it is so slippery (some customers are downright irate about it on the forums).  It may be that the UHMWPE thread would have some of the same problems.  Sailrite has a video about Tenara with some tips to help make it work, it may be some of the same techniques (smaller needles and letting the thread unroll horizontally) might also help with the UHMWPE thread.

Smaller needles would make it easier on the fabric and on the machine, but I wonder if it might lead to more bent needles?  For those of you with experience, does regular polyester (V69) last about as long as the sail fabric, or would it be worth experimenting with a more UV resistant and stronger thread?