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Can 3/8" Balsa Core Go Over 35" Span on Deck Without Structural Bracing?
rhys wrote:
On 26 Apr 2006 08:04:31 -0700, wrote: Does anyone know whether 3/8" balsa core material (sandwiched between fiberglass skins) can go over a 35" span on a deck without any structural bracing? One area of the deck has some water damage and is "kind of" delaminated. The problem may be coming from an improperly sealed inspection hole. I am trying to drill many holes on the deck and inject thickened epoxy into the core to fix the damage. But I discover that the balsa core is only 3/8" thick (the thickness of the deck with core and skins is only 1/2"), and it needs to go over a 35" span in one direction without any structural bracing (the span over the other direction is around 9 feet without any structural bracing). Before I spend time injecting epoxy and all this, I need to figure out if 3/8" balsa core is strong enough to go over a 35" span. If this is not strong enough, I will have to abandon this project and leave bad enough alone (I don't have access to the bottom of the deck to add structural bracing); the reason is that the problem will come back even if I fix it with injection of epoxy. Any idea? Thanks in advance for any info. A question: Why use balsa core at all, knowing what you know? You could use foam core and encapsulated marine plywood for the deck gear through-bolted spots. Balsa core was a great solution to the overkill, heaviness and structural problems of all glass decks, but there are so many better options these days. R. I am under the impression that the replacement core material for patching is better off to be the same as the original core material. Then the repaired area and the surrounding unrepaired area will have the same rigidity; in case the deck flexes for some reason, we will not have crack along the edge of the patched area. Anyway, I haven't decided on whether I should replace the balsa core in the delaminated area. I am still hoping that I can simply injecting thickened epoxy to re-laminate the balsa core back to the skins -- as long as the 3/8" balsa core can handle a span of 35". Therefore, I was not thinking of replacing the core material. Having said that, do you think a piece of 3/8" marine plywood can go over a 35" span without intermediate bracing? What I am trying to get at is to see if the delamination problem that I have is the result of this situation # 1: Under-strength deck -- Excessive flexing -- Break the seal around the inspection hole -- Water intrusion and delamination Or the situation # 2: Improper sealing around the inspection hole -- Water intrusion and delamination -- Excessive flexing If I have the situation #2, I will attempt to inject thickened epoxy around the inspection hole, and to re-laminate the area. If I have the situation #1, I will have to find a way to strengthen the area, not just re-laminating the area as long as I still want to use balsa core. And that can be tricky because I don't have access to the under-side of the deck, and I cannot add structural bracing in that area. In this case, I will really hope that I can find some core material that is stronger than balsa core. And that brings us to my original question: Can 3/8" balsa core go over 35" span without intermediate bracing? Jay Chan |
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