I would say more, it's close to impossible to get the desirable result and that's why I glue instead of sewing.
If I get it right.. Well, it's worth it

Good luck with machining parachute silk. It is an absolute b----r !😉

Thank you so much everyone for the suggestions.
Funny how I used to shop at nylet but completely forgot, I guess the ageing process is in progress😉

Since we are on the subject i must add I never liked thick-ish fabric for a scale model. It simply doesn't act as it should. What it does however is a parachute silk. The movement is just so convincing. This is the kind of fabric I'm going to use for Bluenose.
For now Valdivia will receive (hopefully) similar to original kind of sails.

I did order ripstop nylon but then realized it has that silly square grid pattern. Won't do unfortunately.

Could be worth giving Martin a ring, he makes excellent sails and could probably point you in the right direction..
https://www.housemartinsails.co.uk/

Hi Andy, The company you need if you hvnt already tried is a company Called NYLET. I have been dealing with them for years, a mine of info, they supply fabric for all types of yachts from vintage to racing yachts. Just tell them what boat it is, they will probably know the vessel, they may have tempates even for the sails. Or can make the sails from your measurements. They have a very informative website for yachts persons.
I am or was, just into model rc flying seaplanes until introduced into 1 mtre yacht racing by a friend, sadly rip. But into rc yachts now. Cracking sport when winds too strong to fly planes. Hope this helps. Mike,flyer.🤞

Hello Andy
your description of the material you are seeking could be ripstop nylon. I have used this for many years both in kite making and also for sails on my boats. The lightest weight generally available is 2 oz / 60 gsm which I have found just fine for my boats. It is available on-line (ebay) and is only around £4 a metre. The next weight up (heavier) is 3.8 oz, ie nearly twice as heavy. I have also used this for boat sails but it is stiffer. Sometimes this is preferable.
With ripstop nylon the cut edges do not tend to fray, so I have turned the material just once for the hems. This makes for a flatter edge than turning it twice which is necessary with other types of material. Yes, I make all my own sails and machine sew hems. On some sails I have used bias binding along the edges rather than hem the material. It makes for a firmer edge when using the lightest sail material, which helps when it comes to sewing cringles.
Chugalone has given some excellent information for sail making which is appropriate to cotton sails that replicate the originals as close as possible. However, should you be wanting to create good looking working sails without needing to replicate the look of the originals then perhaps ripstop nylon is the stuff for you.
Happy sewing ! 😉

I made a sail out of real sail material that I got from a marine supplier. I ordered the lightest they had. So far it has lasted more than 40 years. Hope this helps

To stiffen the sail so it will keep the shape I wanted it, I made a 70/30 white glue solution and brushed into the cloth.

let it out in the Florida sun and it was dried in a few minutes.
After it dried front the first coat of the water/glue solution, I diluted the existing formula once again but this time to be 85% water and 15% glue.
This permitted me to spray it with a bottle in the back and front of the sail without detaching it from the jig.
I kept some paper towel to absorb the excess puddles.
I’m pleased with the final results.

Next step was to tight the ends in a way that will leave the sail in a relax and filled shaped.

I know that this section that I will explain does not apply to r/c models but it does if you build a static model.
There many ways to make the sails look filled, but I did this weird looking contraction to help me achieve that.

Hi when I get to mark out the sail for cutting the seams etc. I spray the sail with starch and this leaves a stiff surface to mark out the size.
Roy

Crew Cringles adjustments.
My original crew crinkles were made incorrect because they were open.
This is not correct due to the fact that when the sail gets full, the force of the air will rip the crew crinkle off the sail edge.
So to repair this mistake I sew four new closed cringles, preceded to cut off the original ones and replace them with the closed version.

As you can see here I passed the stitches through the boltrope and very close to each other.
There is about 560 hand stitches all around the sail.
I also made the Head earning cringles and the Crew cringles.
It is not the best ever but it looks good to me.

Coloring the Bolt Rope.
Looking through all my stash of mini rope, I found this one but I didn’t like the light color, so I mixed a wash with two different browns just to give a darker color.
I let the rope soaking overnight, dried it with paper towels and set it out to dry.
This is what I came up with. The original color is the left of course.

To create the hem, I had to iron ¼” on all edges, roll it over and iron it again, just to make it easier to sew.
One thing I found out today and maybe many of our fellow modelers know this already is the fact that you could attach a “Roller Hem Foot” for a super smooth hem.
My next acquisition will be a 3mm roller Hem Foot.
This is a lifesaver for rookie seamstress like me.

I got my sewing machine at my local fabric store.
While I was walking around searching for fabric to sew a sail, I noticed that this particular store had a small section where a lady was giving sewing classes but she was also a sales person for Singer and she had like 10 different kinds of sewing machines, all in sale. My machine was the cheapest one; (Singer Fashionmate 3342) it cost me only $102.00, two years ago.

Wile working with Model Expo and helping a client I had to look into the Benjamin Latham Instruction book and I found this very precise drawing about how to sew my sail seems and that is exactly what I did as you can see here in this picture.

I just want to put my 2 cents in this topic about sail materials.
This is what I did to sew my Galilee Boat sails:
The material used in the thread has to
match with that one of the sailcloth or it will make it shrink.
So, visit your nearest fabric place and I bought this Premium Muslin 100% cotton and cotton thread.
Since I was at the store, I bought two different colors, one has a denser texture that the other.
Here are some pictures:

Hi I usually use shirt material as it is a
reasonably dense fabric. I wash it first to see if it will shrink though.

Do you sew your own sails? Remember to keep the weft running with the longest part of the sail assuming it is 3 sided.
Just made a new sail for my yacht but I glue my seams, 'cos I can't work a sewing machine.
good luck
Roy

Hello,
It all depends on what kind of "fabric" you are looking for. You say that the original was similar to a waterproof jacket - that means a very light, thin, zero stretch, does not let air trough material. Well i've never found this material for sale and never even found out what it is called (every fabric has a name - commercial or technical). So i had to buy the said jackets and hack them to pieces. But there is an alternative - it is called ripstop and comes in different weights. For RC sailmaking it is used the polyester type as it has the desired behaviour in contact with water. You can find it in kites shops. I do not know any UK based kite shop but you can take a look here: https://www.metropolis-drachen.de/en/Kite-materials/Cloth-Fabric/Spinnaker-fabrics/.
The only problem with this ripstop is that it has that square pattern. Hope it helps.
Regards, Eduard.
P.S. Of course there is the Aliexpress alternative but i do not recommend. They have mostly nylon based ripstop and "jacket like" fabrics. So far i could not find anything on Aliexpress that will not stretch apart for some lower quality ripstops. And you will waste a lot of time searching trough the site and ordering samples that will take some time to be delivered. If you want some links from Aliexpress let me know.