Sfalkner
New member
Grateful for advice and opinions.
I have a 1974 Alpa 11.50 (Italian) with some spongy/springy patches on the foredeck. When I tap the deck with a ball hammer I get a dull thud in the areas of springiness. I therefore assumed that I had damp in the balsa sandwich core and eventually resolved to fix the problem by removing the top layer of fibreglass, digging out the degraded wet balsa, drying, replacing with Airex foam and re-glassing the top. I had misgivings about doing this as it would be nigh on impossible to match the moulded non-slip pattern which is arranged rather like a teak deck with “planks” of diamond-pattern non-slip about 2” wide separated by smooth “caulking” strips about 1/2” wide.
Today I bit the bullet and made two double cuts with an angle-grinder in the “caulking” strips as a tester. The thin strips of top layer FG were removed leaving an opening about 6” x 1/2” and I was able to dig out some core material with a small screwdriver. To my surprise it was neither balsa nor wet. Rather it was somewhat crumbly foam and quite dry.
Sorry about the long intro. Now to my questions:
What is the foam likely to have been in a boat of this age?
Could the foam have broken down in structure over the 48 years to cause the springiness without ingress of water?
If so, and I were to make frequent cuts as I already have in the “caulking” strips and inject epoxy resin which might then spread sideways under the moulded “planks” might I achieve a sufficiently solid deck and avoid cutting large chunks out which would destroy the moulded “planking” pattern?
Thanks in advance for any thoughts.
I have a 1974 Alpa 11.50 (Italian) with some spongy/springy patches on the foredeck. When I tap the deck with a ball hammer I get a dull thud in the areas of springiness. I therefore assumed that I had damp in the balsa sandwich core and eventually resolved to fix the problem by removing the top layer of fibreglass, digging out the degraded wet balsa, drying, replacing with Airex foam and re-glassing the top. I had misgivings about doing this as it would be nigh on impossible to match the moulded non-slip pattern which is arranged rather like a teak deck with “planks” of diamond-pattern non-slip about 2” wide separated by smooth “caulking” strips about 1/2” wide.
Today I bit the bullet and made two double cuts with an angle-grinder in the “caulking” strips as a tester. The thin strips of top layer FG were removed leaving an opening about 6” x 1/2” and I was able to dig out some core material with a small screwdriver. To my surprise it was neither balsa nor wet. Rather it was somewhat crumbly foam and quite dry.
Sorry about the long intro. Now to my questions:
What is the foam likely to have been in a boat of this age?
Could the foam have broken down in structure over the 48 years to cause the springiness without ingress of water?
If so, and I were to make frequent cuts as I already have in the “caulking” strips and inject epoxy resin which might then spread sideways under the moulded “planks” might I achieve a sufficiently solid deck and avoid cutting large chunks out which would destroy the moulded “planking” pattern?
Thanks in advance for any thoughts.