I have to agree with Mr Hughes on this one. Unless you are very careful on amounts and locations where the foam is placed, it can destroy a boat and yes, been there seen that. It can be done, as shown by Scott Meyers in one of his videos:
The message is don't try it in a closed space. In an open space like the sponsons pictured it can be shaped to fit. I've had experience with both. The closed space try resulted in a scale boat that's now a wall display in my local hobby shop.
I'm sure they have made improvements in this stuff but on some of it if the skin gets cracked it absorbs water and swells. Given the pounding the average RC boat takes cracks are probably inevitable. I saw a guy pull chunks of it out of a boat and squeeze the water out of it.
Bob....dont....dont....don't use the spray foam stuff from the box stores....that stuff absorbs water....its terrible for boating...i have started using the green or pink insulation foam rough cut and glued in position then trimmed with a hot wire if possible...or sanding block and elbow grease.
NONONONO don't do it been there done that bad idea the reaction will kick off ( especially I hot weather ) again and will blow the deck off and distort the hull and it will take alot of effort to get out and get the boat back to the proper shape again
When someone uses a thing unwisely it doesn't automatically become a bad thing. Used correctly, pour foam is awesome. It adds both strength AND flotation, and what's not to like about that? Here's the short deal for those who don't want to watch the whole video;
* Pour foam expands. A lot. Use in an open area only. C'mon man!
* Pour foam contracts again slightly as it hardens, and will distort a thin flexible surface. Best practice is to use in wood boats only.
* Pour foam will not 'react again' (the little atom buggers become different atom buggers during the initial reaction and cannot switch back).
* Pour foam will not absorb water when cracked. The reaction creates a kazillion tiny bubbles, not one giant bubble that would lose its bubblyness if cracked. Let's use some common sense here. See c'mon comment above ^^^
* Pour foam does not become squishy when wet. On the contrary, it is brutally hard and will remain so indefinitely.
* Pictured here is a way to make your boat very strong and very floaty (is that a word?).
* This boat pictured is four years old, looks like new, was nitro, now electric, won last weekend.
* Go build a boat!
Anybody that thinks pour foam won't absorb water has never restored an old boat. I have gutted boats that had been in dry storage for 2 years that the foam was full of water. There are so many better ways to add floatation. Depending on brand it can contract for years warping any surface that it has bonded to.