Starch on sails

[MESSIS]

I have been told that using (spraying) starch on sails I can achieve more stiffnes of the cloth making the sails look full of wind. Is that a fact?

[wefalck]

In principle yes. However, I would refreain from using such organic materials that are prone to microbial attack, commonly called mould. Other people seem to have used diluted PVA glue or, in my case, sanding filler. Matt acrylic varnish could be another option.

[MESSIS]

How shall I apply the sanding filler or the varnish?

[MESSIS]

I believe the acrylic  varnish spray will be a very practical applycation prosses. Spraying the sails inside side..... I dont know...  if thats correct.

[JerseyCity Frankie]

I've tried starch (powder form, mixed in water) and was disappointed. It IS good for firming up fabric you iron flat in order to cut with a razor though, it completely halts any tendency for the material to Frey at the cut. But it won't make sails hold a shape and as mentioned by Wefalk above, it's a food item and microbes will eat it. In my current build I'm using two part epoxy, check it out in my Yawl Dulcibella log link below.

[MESSIS]

Thank you Frankie.... I wont use it. Am thinking as wefalck advised me to use mat varnish. Though I dont know how exactly I should do so.

[Altduck]

Messis,

 

I don't know how to do this, but I'd suggest you experiment with some scrap fabric material and different stiffening materials, mixes and application techniques before treating the sails on your model.

 

And please let us know what you find that works and doesn't work.

 

Good luck,

[John Garnish]

I would use diluted PVA adhesive, brushed on.  Fix the sail in a realistic position - (perhaps not on the model) - and then use a hair dryer to blow the sail into shape and dry the glue at the same time.

[John Garnish]

11 minutes ago, John Garnish said:

I would use diluted PVA adhesive, brushed on.  Fix the sail in a realistic position - (perhaps not on the model) - and then use a hair dryer to blow the sail into shape and dry the glue at the same time.

I should have mentioned that the formed shape of the sail will still be quite fragile, so you should avoid handling it more than necessary.  That means that you should have fixed the sail to the yard and attached to it all the necessary rigging lines (tacks, clews, braces, buntlines, bowlines, etc.) before forming it to shape.  

[wefalck]

Some people use air-baloons as formers. One has to check first, whether the choosen varnish doesn't eat the baloon though.

 

A completely different technique is to hide a stiff wire in the bolt-rope of the leeches and feet of the sails.

[MESSIS]

You mean inflate the sir balloon and place the wet with varnish or pva sail on the ballon until it drys?

[wefalck]

Exactly ! Depending on how much you inflate it, you can adjust the roundness.

[MESSIS]

Am thinking that the safer way to do this is the mechanical and not the chamical approach. A still wire 1/2 mm (1/89) or less depending on the scale is safer.... no danger of messing up the sails if something goes wrong with tha varnish or fillers etc. A wire cannot harm and it can also be corrected or even withdraw until you have the desirable result. Isnt so wefalck?

 

Am thinking to go for it. Do you think 1/2 mm diam for 1/89 scale is reasonable?

[wefalck]

Probably to thick. Try to find stainless steel or bronze wire of 0.3 mm diameter. Brass or copper may work, but coudl be too soft.

[MESSIS]

Ok thank you.  I saw you are in France. So I let you know, am working on L'Hermione and I plan to come to France in May and visit Rochefort.

[MESSIS]

Do you think that the wire method  can be succesfull without the use of any chemical as varnish, glue or filler?

[MESSIS]

I rather go for an acrylic varnish spray with the help of an air ballon.... but am afraid that when the varnish (sprayed on both sail sides) drys out it can may be stay stucked on the ballon.

What do you think?

[MESSIS]

Thank you Frankie.... I am going now to see your a work. And I ll come back to you with my questions or comments. Thats a relieving help you just gave me.

[BANYAN]

If you are worried about the varnish reacting with the balloon try another forming method such as a sand filled bag.  Get the sand bag into the shape you want, drape the sail over it and spray on the varnish.  Just be sure to be using  a colour fast fabric for the bag, or put a layer of glad/cling wrap over the bag between it and the sail to be sure.

 

cheers

 

Pat

[thibaultron]

For the problem that the surface in contact with the balloon/bag is smooth, perhaps cover the "mold" with similar cloth, apply the paint/epoxy, etc., let it set then spray it with some sort of mold release. After that put the real sail on. that way the mold surface would be textured, not smooth, and both sides of the sail would be textured.

[wefalck]

The problem of getting a sleek surface in contact with the 'former' (balloon etc.) only arises when you soak the fabric with the stiffening agent. There is really no need for this.

 

Otherwise, you can also suspend the fabric on its four respectively three corners, e.g. by pushpins driven at an oblique angle into a board, and apply the stiffening agent then. I did make sails from single pieces of model-aircraft silk ('silk-span') in this way, by soaking it lightly in poster-paint (today I would use acrylics). This closes the open weave of the fabric, while still keeping it flexible and as the material is hanging through while wet, you get the slightly billowing effect. Such sails are not translucent, however.

[MESSIS]

Like this....

 

Do you apply the stif. agent in both sides or only on the side where the wind blows?

[src]

Frankie, have you, or anybody tried thinning the epoxy down with denatured alcohol?  I suspect it weakens the epoxy but it should saturate the fabric and not fill the weave. 

Also we sometimes use alum to stiffen fabrics for backdrops. Does anybody know if that would be an option for this?

sam

edit. On second thought when we have used alum when the fabric was not stretched properly. I think it might make the fabric shrink. Probably NOT the intention here🤔

[wefalck]

I gather the alum was used, like sodium silicate, rather as a flame-retardant on theatrical fabrics than to stiffen them ?

 

I really wonder, whether this is a good use of epoxi-resin. Of course you end up with a sort of fabric-reinforced resin shell, but it seems a bit messy in comparison to using one or the other type of varnish.

[thibaultron]

They make stuff you can brush on rotten wood trim to harden it. Then you use filler to restore the surface. This has fungicide in it. It is thin and soaks into the wood. Maybe these compounds would work. I think one brand was Dr. Wood.

[src]

Weflack, I dont know about the flame retardant aspect of Alum, perhaps some do use it for that, your handle on chemistry is far beyond mine. I do know that when we do work with any kind of fabric we are required to use an IFR (Inherently Flame Retardant) fabric. For us at least flame retardancy has not been a reason that I am aware of for using Alum.

Sam