anxious boater wrote:
I have a 1969 fiberglass (polyester) hulled houseboat. It's a Thunderbird
Drift-R-Cruise. All the engine stringers and three interior stringers are
shot. Everything I have read so far basicly says to epoxy the stringers in,
fillet and glass over. I am certain the first two steps were omitted, either
when this boat was built or this job was done in the past. Some of the
inside stringers aren't even resting on the hull interior surface. From what
I can see, water leaked in at the bow (and other places) and simply migrated
to the back of the boat. The rot is really bad starting in the bildge (the
stringers oozed out when I started cutting!) and improves some moving up
closer to the bow. Is this poor boat building, or just the way it was done
back then?

Now I'm not so sure that I should put the new stringers in using the current
methods. For example, will the vibration from the motors cause cracking in
the hull glass if they are epoxied in, solid as a rock?

Thanks,
Steve


Back in 1969, a common boat bulding philosophy was to depend on wood
for strength and then to "protect" the wood by encapsulating it in
fiberglass. Remember, there were still a lot of brand new wooden boats
built in the late 60's. A look at your stringer would help determine a
lot about the builder's original intent. If when sawing into the
stringer your're finding a great big chunk of wood covered by only a
couple of layers of glass cloth, (which it sounds like you are, from
the description), the builder considered the wood itself the structural
component. In later years, the role of wood in stringers began to
change. The wood was reduced in size and used somewhat more as a form
around which to laminate
a stringer. In cases where there is a smaller piece of wood the builder
was relying more on the strength of the laminate than the core. A lot
of modern boats are bulit with hollow stringers (like a box beam) or
use foam instead of wood for the core, and all the strength of the
stringer is in the laminate and it's shape.

You should get a highly qualified marine surveyor and maybe a naval
architect to look at your specific situation. Sometimes there is a cure
available by building up an extra few inches of thickness on your
existing laminate to "take up the slack" from the rotting core and
restore adequate strength. Othertimes, not.

I suspect that with a 1969 boat you will need to yank out the current
stringers entirely. If the rot appears localized, you will certainly
want to take out a couple of feet of material beyond the point where
you think the rot ends. Drilling small pilot holes into the stringers
and examining the drill scavagings will let you know about places where
the wood is wet or soft, and you can use a moisture meter to good
advantage in your situation.

As far as replacement or repair technique, most likely you are going to
be restricted to redoing something close to the original build. There
would be no point in even attempting to "build up" existing stringers
with additional layers of material if the stringers are no longer
attached to the hull.

Here's hoping you like this boat a lot. What you're about is no small
undertaking.