stringer replacement advice
 

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