The blue and white can of foam sealant that kwmtrubrit is talking about is Dab Tex Mulit-Purpose Insulating Foam Sealant. It is a latex-based formula that will not overexpand and much easier to use than the yellow high expanding foam. It is white foam, it will clean up with water for reuse and it can be tooled or shaped while wet if done quickly. It is not fuel proof but it can be sealed with latex paint and then fuel proofed with polyurethane. I have used it on planes, boats, cars and my home. If you fill whatever you are working on about 90% it will not overexpand. At $3.50 a can, and you can reuse it if cleaned, its a good product for R/C use.