6 x 6 backing block x 638 = 22,968 pounds. That would lift this
particular boat, almost two of them, in fact.

My real question was whether the stuff appears to grab with close to
its potential strength on old fiberglass.

I'd certainly lay up a nice epoxy and glass backing panel in this area
if I could reach it. If 5200 holds even 60% of its book number on the
ground fiberglass, it's probably plenty strong though.

--

Roger Long



"BF" wrote in message
...
3M lists tensile strength of 5200 as 638psi in salt water, Emerson &
Cuming
26 Eccobond GP Epoxy has an adhesive bond strength of 2100psi.
No personal experience but the numbers don't look appealing.
BF


"Roger Long" wrote in message
...
Does anyone have any direct experience with how well 5200 sticks to
old but cleaned up fiberglass?

I have to put a new backing block in for a through hull in a very
awkward location. Since it's a Signet Knotlog, it has to be flush
and
there isn't much back up in the taper for a direct hit on some
floating object. I'd like the back up block to be actually backing
it
up.

Building up with fiberglass and epoxy working through a hand sized
opening is going to be tough. I'm wondering if a larger than normal
sized plywood backing block done with 5200 might not be nearly as
strong.


--

Roger Long