It depends on how much fiberglass is in the hull to withstand the hard knocks and abrasion... if you could provide a name to ID, might be some help. Generally, fiberglass alone isn't considered the best choice available when it comes to durable construction, with expedition-grade kevlar, Royalex, and the newer materials like Tuffstuff and T-formex being more suited to contact with rocks.

Still, if it's very heavily built, it could be durable enough and I'd hesitate to throw a blanket over all fiberglass canoes. One way to check whether you've done any damage in the past is to press down on the upside-down hull with the heel of your hand in various spots and feel if the fiberglass has gone soft or mushy anywhere as a result of being bashed around too hard.

Repairs can be done in the field with duct tape to stop minor leaks, or at home or even in the field if you know what you're doing with a fiberglass patch. Abrasion over the long-term with year after year of rocks grinding down the hull, especially at the keel line near the bow and stern can also be a problem, and applying extra fiberglass layers there can help replace the worn-away glass.

If there isn't any significant damage yet, you might be able to carry on business as usual, but I'd take it easy considering the age and outside storage with exposure to sunlight and UV that might have caused deterioration and weakening. I have an old fiberglass canoe from about 1970 that still is able to take some abuse, but it's probably lighter in construction than yours and patches have been necessary.

 

Last edited by frozentripper (8/09/2017 6:39 am)

I don't know how useful this is to the conversation, but my limited experience with fiberglass is that it is stronger that one would expect.  In the early 80's on a scouting trip, two brothers brought a 10' fiberglass canoe that they had made.  It weighed fourteen metric tons, and cut through the water like a clawfoot bathtub.  It spent the week on the horizon in back of the group.  Brother 1 was in the bathtub, Brother 2 sterned the 17' Grumman another boy and I were in. 

Brother 2 got angry with Brother 1 over a grab-your-hat-and-throw-it-in-the-river-so-we-can-pass-you incident, so Brother 2 got us to full speed heading toward the fiberglass canoe, yelling "Ramming Speed!!" which was at rest, beached on a sandy portage entrance.  I thought he was just messing around and was going to slow and/or veer off, but when I realized he actually intended to hit it, I stopped paddling (in fact out of reflex I braced for a brief second, but on the wrong side....which lined us up even closer to the center of the bathtub), so the momentum of three teenage boys, all their gear, and a 78 pound aluminum canoe, minus one second of bracing, t-boned the fiberglass canoe almost dead center.  The crunching was horrific.  I thought for sure it was destroyed, but there was zero damage to the little bathtub.  The damage came when the father took the two brothers a little deeper into the woods for a father-to-sons talk.  Much hash was settled during those few minutes. 

So - I think as long as the fiberglass isn't really brittle, you're in pretty good shape.