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