a friend of mine has a balsa sandwich deck and a couple of small areas of less than a square foot are spongy. i know the 'proper' solution is major surgery, but i had a similar problem with my caravan floor. that is a polystyrene sandwich between two layers of ply and as the polystyrene sags the floor becomes spongy. the caravan fix is to inject a 'glue' which flows into the sagging bit and fills the void, setting solid. the caravan guys also have a 'water loving' glue that sets solid when it flows around areas where damp and water have penetrated sealing the rotten bit solid. is there anything my friend could do with his deck in a similar fashion?
the leaks that led to the rotten balsa are cured and the problem is isolated into a couple of small sections. what do the experts out there suggest?/QUOTE]
Hi Bob,
Because the caravan floor had a layer of ply each side meant that the moisture was not totally trapped so it couls dry out over time.
However this is not case when dealing with a fibreglass sandwich.
By using the water tolerant glue you will be trapping the existing moisture and this will lead to further rotting.
ALL moisture MUST be removed prior to sealing it up or the problem will continue to spread.
Replacing the sodden foam with a CLOSED CELL foam is the answer. Closed cell foam will not take on moisture and is not effected if moisture is present.
The injection will only work if the foam and underside of the deck are clean and dry, so don't waste your time with this method.
Do not use ply, it will also rot if it gets wet, the closed cell foam will not be effected by this.
Good luck and fair winds.