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[flashtwo]

Hi Mayhemers,

I've always understood that the glass fibre cloth is held together with an "adhesive" (applied during manufacture),  which dissolves when the resin is applied.

If this is correct, does it matter which resin is used - polyester or epoxy?

Ian.

[TailUK]

Chopped strand mat as bound together with starch and may present problems with epoxy.  Woven mat may be more suitable.

[flashtwo]

Hi TailUK,

I thought there some sort of adhesive, but I didn't realise that it was starch and on the chopped mat - many thanks for explaining that.

I plan to use 100g (4oz?) twill woven cloth as I understand it follows hull compound curves better than the other weaves. It is going to be used as the final layer on top of two layers of Sapele veneer. The boat is the 75inch  Edwardian Steam Launch that is being descirbed in the Steam section.

Ian

[Neil]

I plan to use 100g (4oz?) twill woven cloth as I understand it follows hull compound curves better than the other weaves. The boat is the 75inch  Edwardian Steam Launch that is being descirbed in the Steam section.
Ian

What you building a full size battle ship!!.
I think for a model that size you'll be quite adequate with the equivalent of 1oz chop strand and a maximum of 3 layers . 2 1/2 layers would be better.
neil.

[SailorGreg]

As has been said, the woven cloth doesn't have any binding agent to hold it together like the chopped strand mat does, so you can use either polyester or epoxy resin.  (You can only use polyester with the CSM.  Epoxy doesn't dissolve the binder, meaning you end up with an unholy mess!)  The size of your boat means you are getting toward needing full-size practice, so a quick look at a site like this - http://www.wessex-resins.com/westsystem/final-sheathing-of-a-canadian-canoe.html might help you.  Or just google "sheathing a dinghy" or "sheathing a canoe".  You won't need the same weight of cloth as the full size boats - your 100g is plenty heavy enough and you only need one layer.
You can use ordinary 4" foam paint rollers from the local hardware shop to roll the resin into the cloth if you are using epoxy.  I don't know if they work with polyester as I've never tried that - they might just dissolve, leaving you with a very messy finish 
Have fun with the sheathing - it's going to look great when the sapele gets its first coat of resin!

Greg

[Subculture]

You can get two types of chopped strand matt. Styrene bound, suitable for use with polyester and vinylester resins, and powder bound, which can be used with any type of resin including epoxy.

Powder bound matt is more expensive than styene bound, so unless you're using epoxy resin, there is no advantage. Cloth laminates give a lighter more flexible laminate than CSM, but not as rigid. Therefore laminators sometimes sandwich a layer or two of CSM in with cloth to stiffen the composite structure.

I would use epoxy resin for your boat, it's much nicer to use than polyester, and the extra cost is not huge for one offs like this. I highly recommend Reactive Resins for epoxy resin, a Cornish based supplier. Really nice resin, and very good prices. For other types of resin I have used CFS, who are also excellent.