Roger Long wrote:
It's not vulnerable to much unless there is impact and flexing.

I'd say even then, it's not any more vulnerable than the rest of the
hull, given a proper job.

... I
wouldn't want to just fill the hole on a solid layup (which my boat
is) as there isn't much to hold the patch in. The fiberglass should
be tapered back so there is a good, long scarf for bonding.

Sure, that's part of doing it right. I assumed you were comparing the
cap/plug to a proper repair, not just slapping in some putty.

... You're
right that it wouldn't be expensive to do yourself but I'm thinking
yard time (after all, my time is worth something too and unenjoyable
jobs like grinding fiberglass don't have their own rewards). By the
time it is ground, filled, faired, and re-painted, it will cost a bit
either in other things you didn't get done or out of the checkbook.


Agreed. But... if the boat is already hauled for other work, and you
already have other fiberglass work in hand, doing a patch on a former
thru-hull hole is no big deal. I spent more time on the work pictured in
putting up & taping a drop cloth in place to keep grinding dust from
getting all over the engine room.

With a cored hull, you can and should dig out as much core as you can
reach to seal if from the water. This will create a good mechanical
as well as adhesive connection since the patch will extend between the
skins.

Agreed. In this case it would be important to make sure the core is
thoroughly dry & still bonded, and to use material compatible with the
core. Not many hulls are cored below the waterline though AFAIK.


The cap and fill will last as long and reliably (actually more so due
to the watertight fill) than the rest of the through hull plumbing.

Sure, but that's the point. A thru-hull is a vulnerable point. It's a
hole in the hull, a potentially disasterous leak. Vulnerable to
grounding or other impact, flexing, corrosion, freezing, electrolysis,
and occasional misadventures. As opposed to a hole that has been
fiberglassed over, which is vulnerable to... umm, you haven't explained
that part yet...

That's good enough for me. Getting plastic through hulls, especially
the ones near the waterline that can freeze, replaced with bronze is a
much more important issue.


If that's already on your work schedule, then removing & fiberglassing
over the old unused thru-hull during the same haul-out is a trivial
addition IMHO. But hey it's your boat

Fresh Breezes- Doug King