Low Expanding Foam

[Jon]

I'm scratch building the hull of a ship in 1/350 scale. With two kids and a flurry of new releases in 1/350 injection molding has made it tough to focus on my scratch building subject. Glue has caused my sheet plastic to expand forcing the front of the ship to lift. I cut away some of the offending pieces but now having trouble figuring out how to build up the bow.

My idea is to fill the bow with Low Expanding Foam, that stuff you use to fill and insulate gaps in your house. Foam in a can. Any one ever tried this before? The basic hull framework is there, I think enough to hold the foam in place. If it over flows a bit, I'll just shave it down. I'm going to give it a go in a few days but want to see if any one has tried this yet? I know the stuff dries pretty hard and isn't tacky so thought it might work for this.

Thank you,
Jonathan Somerville

[Francisco P. de Nanclares]

I have seen a guy building a small forward section of a model from the main deck up with foam cut to shape after cured, but that was open. Not sure about closed spaces though.

Here is the link. It�s in Spanish, but go to page three and scroll down. This particular ship sported a humpback, or whatever the correct name for this shape is, on the forecastle, and this was the modeler�s test with foam.

http://www.u-modelismo.com/foromodelism ... opic=904.0

If you are interested, I can translate the tip for you.

Cheers.
Pachi.

[Jon]

Hi Pachi

The foam that I plan to use is that spray foam. I guess I didn't say that up above, so my own fault. I'll check that link and see how this was done though.

Jonathan

[Jon]

Hi Pachi

Yes, I checked it out, it is the spray foam you are talking about. Mine is enclosed but only on the sides and bottom. Based on what I just saw, I'm now more confident, I'll post my results here.

Thank you very much.

[Sean Hert]

Jon-

I used the spray foam once- it ran all over, and as it expanded over the evening, it popped the balsa skin I had CA'd to the frames free. It even distorted some of the ply frames.

Now, this was in a larger scale, but I have forsaken it for anything other than open framework.

[Jon]

Thanks Sean

I don't think it will be an issue as the top of the hull is still open so will push out this way, plus there are lots of open spaces still in the hull. I can't wait till I can give it a go. I'm actually looking to use it around the house as well as once the can is started, you can't stop and use it the next day. One time use only.

[Sean Hert]

Actually, I've poured a little acetone down the tube and melted the left over foam out and used it again.

I've got a 1/2 can in the garage now. Hmm, maybe I'd better check on that.....

[ScottOram]

I used the foam to build up mu hull for the "plug".

[Jon]

Hi Scott

Thanks for this post and photos. Neat to see how you did your project. I sprayed my foam and it expanded a little more than I expected only because the can said it would cure at about 20 mins to the touch. I took that as meaning it would stop expanding too at that point so sprayed a bit more to fill some gaps but it kept expanding for just over 12 hours. This pushed some bulkheads a bit too much but think it will be easy to fix. Even though not done shaping the hull, I think this method works pretty good and will use it again.

This is my first scratch built ship and I can't wait to get working the foam and shaping it but been too busy. I've learned a lot doing this project and once done can't wait to scratch build again.

* Oh, and thank you Scott for your photos of CV-64 on Carrierbuilders...

Jonathan

[ScottOram]

I had similar experiences. I would spray it and let it cure, then cut away the excess. Well that would remove some of the harder outer shell and the uncured center would then begin expanding some more, until it was cured all the way through.

If you look at the second picture you can see some of these "wet" spots. Two hours later they were expanded bubbles poking through.

[Jon]

Last night I was able to cut away the main excess foam and to my surprise the bow settled back down again. It had lifted about a quarter of an inch when the foam cured. I'm very pleased with the results. Now I just need to know how I can cover the foam so my paint doesn't crack with changes in temperature/humidity. Any help on what you used to cover the foam would be extremely helpful. I'm thinking of trying applications of that auto body filler compound.

Thanks,
Jonathan

[Sean Hert]

Make sure you use a polyester or epoxy based, catalyzed putty. Self hardening ones, AKA solvent based, will eat through it.

I've done that....

I've heard of using spackle, but I haven't tried it.