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Brian wrote: Thanks Mike, I used epoxy laminating resin, but I was too generous with it and the joints are far too thick.

Even with a thin layer of epoxy it would show.

I don't know why 'we' join foam with epoxy. I remember kits from the '80's always instructed us to join the wings using 5-minute epoxy and wonder if this is where the idea came from. I only ever use pva or aliphatic for joining foam. Much cleaner and gives time to align properly. And it doesn't really matter if the joint is perfect, although will be better if there are no big gaps. If you've never tried it, join a couple of scraps of foam together using pva and leave alone for 24-hours. Then try to break them apart and I'll guarantee that it will be the foam breaking and not the joint.

Never thought of using aliphatic glue, didn't think it would dry out as the foam isn't absorbent. I'll give it a try, better than hauling the wire cutter out and firing it up. Thanks Mike.

Cut some foam block and glued it with aliphatic glue. Left overnight, attempted to start shaping but the blocks fell apart. Think it was due to being cold overnight.
Experimented with the original resin bonded blocks. Gouged out the resin line and filled with Polyfilla one fill. Laminated a cowling using fibreglass tape and thinned Bostik PVA flooring adhesive. When dried, added three laminations of heavyweight model tissue (ex free flight power jobs) once again used the flooring PVA. Tried to speed things up by using heat gun, this looked good as some of the smaller wrinkles disappeared. Unfortunately got over enthusiastic and part of the foam core softened and collapsed. Good job there's no hurry. No photos, too embarrassing!

Brian wrote: Cut some foam block and glued it with aliphatic glue. Left overnight, attempted to start shaping but the blocks fell apart. Think it was due to being cold overnight.

I don't think that temperature would have that big an effect...we're not talking about the difference between tropical and arctic weather. How much glue are you using? You want to use as little as possible. I put glue on one of the blocks and press the two blocks together . Then slide them in order to spread the glue. Separate the blocks and look to see that the glue has been spread everywhere. Add a little more glue to dry spots and spread it some more using the blocks. At this stage the blocks are already very difficult to pull apart. And if it is easy to slide the blocks then you have too much glue.

An alternative if you really cannot get PVA to work is UHU POR. I use exactly the same technique for spreading this contact adhesive. Once spread you just separate the blocks and leave for about 5 minutes before pressing back together again. POR is also hot-wire cutable.

I put some glue on one surface and spread it thinly, applied the second block and "wrung" the blocks to get a good grip. Left overnight with a weight on top. The early morning temperature showed as just over nine degrees C. The blocks were bonded to a distance of about 10mm in from the outside edges. I think perhaps a full 24 hour cure is needed. Anyway, its all good fun and possibly informative. I'm using a very dense flooring quality blue foam, I wonder if a more open textured foam would get a quicker bond?

Brian wrote: I'm using a very dense flooring quality blue foam, I wonder if a more open textured foam would get a quicker bond?

Overnight is definitely not 24 hours.

The foam I use is exactly the same as yours.