We used peel-ply on Befur. I think we failed to squeeze enough epoxy thru the peel ply and had quite a thick coating. I agonised about the overlaps and eventually decided to leave them in place to provide structural strength.

When I then sanded, I took care not to reach the cloth, but just tried to reduce the "tiger-stripe" sags. (I am told you can get thixotropic additives to help with this.)

Finally I used an epoxy sanding filler to smooth out the double-layer overlaps.

There are pics of the two stages here (on the blog)

Cladding

Filling

... seems a long time ago.....(fitting out progresses slowly)

Garth - your project sounds fascinating.  Can I persuade you to write it up for the magazine? 

I'm interested in your comments about peel ply.  From reading around the subject, the feeling that I got was that it is really for structural glass rather than sheathing.  As you surmised, the glass on SibLim is purely to make a harder surface to protect the underlying (rather soft) okoume/gaboon ply.  I can imagine that it's perfect for fillets such as you described, particularly because it can be a real schlep to get those edges faired and smooth.

BTW thanks for the comment about the extra cost of using peel ply.  I did rather wonder.  And you have to throw it away at the end - I loathe making more rubbish than I absolutely have to.

Arne: you are quite right that you want plenty of epoxy on the job at the end.  However, the Gougeon Bros seem to get quite excited about the idea of the glass floating in epoxy, rather than adhering to the hull, so when you have finished laying it down, it should have a matt finish, which shows that it has wetted out, but is not totally saturated.  Then you put another couple of coats on top to get your epoxy build up.  Particularly at this time of the year, the epoxy throws off a 'blush' (more like a slime!) of amine, poetically referred to as 'amine bloom', which needs washing off with fresh water which has a little household ammonia in it, otherwise the epoxy won't stick.  If you get a fresh coat on within 24 hours (probably longer in the cool weather that we are presently experiencing), there's no need to sand between coats.

I've done a lot of glassing in my time.  It's one job I feel thoroughly comfortable with.

I don't know much about junk rigs but I have some experience with sheathing and peel ply.

I think Annie's method of making butt joints in the sheathing will work just fine assuming the plywood takes all the structural loads and the glass is there primarily to protect the wood. 

On my boat, I wanted the sheathing to be more structural with out week spots between the cloth panels.  What I did was lay out alternating panels athwartship.  This let me work in between the panels while glassing and also let me grind tapers in the edges, 2-3 inches.  Then I layed the remaining panels - overlapping the first ones.  Grinding them flat produced what is effectively a scarf joint in the glass.  This wasn't nearly as nasty a job as it sounds like or as I thought it would be.

Peel ply is pretty easy to use but it is pricey if you plan to use a lot of it.  Nylon shower curtain works well but there is not really much cost advantage.  I have read that the Dacron (polyester) peel ply is better than the nylon as the nylon may leave a residue.

Peel ply works well for reducing excess resin.  You still use the resin of course but its easier to remove.  Its also good if you want to bond to the surface without sanding.  I am mostly using it on my bulkhead to hull fillets.  After applying the fiberglass tape, rather heavy 18oz Biax, I lay the peel ply over it, and smooth with a squeegee and/or paper towel.  This ensures the tape is fully wet out, wont need any additional coating, and even produces tapered edges.  All this eliminates the need to sand the fillets which is a huge time saver.

I generally let the epoxy fillets set up before I glass them. I bought a round nosed burr to quickly sand the fillets that chucks in my hand drill.  The burrs are intended for wood carving.  This is currently my favorite tool.  https://kutzall.com/collections/ball-nose    (fine grit works for me)

'Everyone' suggests that I should use the Peel ply technique, but I haven't for several reasons.  The first is that I've never used it and so need to learn a new technique, which I'd rather not do.  (Thus far, each time I learn a new skill, eg scarphing plywood, just as I'm starting to get the hang of it, I finish the job!)  The second is that I'm not sure how it would help with the issue of smoothing out the joins in the glass - I guess you'd peel off and then scrape/plane them smooth.  Most importantly, however, is that I follow my other 'bible' The Gougeon Brothers on Boat Construction, as closely as possible and they strongly emphasise using minimal amounts of epoxy to glue down the cloth.  I would be concerned (a new technique, remember!) that I might end up with too much epoxy, which effectively floats the cloth.  In theory, great efforts with squeegees would obviate that, but I'd then end up with lots of excess epoxy to try to use up, or, more likely, to dispose of and I'd still be worried that I had an uneven coating.  So I stick with the method that I know, and trust that it will all be OK. 

I'd like to try the peel ply technique sometime.  Maybe I will build a new dinghy one day, and I'll use it then.  :-)

A hundred years ago when I was building Burt Rutan aeroplanes and we were doing overlap joints with multiple tapes, we used what Burt called 'peel ply' which was just strips of I think terelene (or something similar) curtain lining, very thin and which absorbed epoxy well to overlay the joints.  Having squeeged out the excess epox from the two or three or more tapes (say a series of five, four and three inch wide tapes used in sequence, widest nearest the join) cut from woven cloth on the bias so that they would lay down in difficult corners) we would apply the peelply over the joint, wet it out, squeege hard, leave an unepoxied end showing and the next day when it had gone off we just stripped it off like a band-aid.  We got a nice smooth elided joint with very little excess epoxy.  This made a very strong and light joint. Always a bonus in aircraft. Nowadays I guess boatbuilders use commercial tapes with woven edges. Perhaps this might make it more difficult to get a smooth join  However as we cut ours from the original bolt of cloth as above and then used the cling film trick to prep. the tape we could apply them in the most awkward corners, sometimes inverted and using a mirror - I still have nightmares! I might add that we never had a joint that failed.  For those aeroplane builders among you I speak of the Long Eze generation of Rutan designs and not the Spaceship One! David