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Sealing a Fiberglass Canoe

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    Splitting Cane

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Posted 01 May 2013 - 04:01 AM

Need a little help. I was given a 16' fiberglass canoe from a friend who happened to walk into an unbeatable Old Town deal. However he did say the canoe trends to weep on the bottom and possibly needs to be resealed. Can i do this by lightly sanding and then recoating with resin or do i need toreglass the whole bottom?

Any advice from those who have been there would be great.


#2 DrVette

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Posted 01 May 2013 - 12:15 PM

Just using resin on any "repair" is NEVER a good idea. I don't know canoes (i hate boats) BUT i do know fiberglass from years of custom car building and a lot of Corvettes.

The first thing is to determine what the original glass is. There are 3 types, woven sheet, chopped (or varrying sheet) and then there is the completely differnt SMC (sheet molded composite).
The first 2 use the same resin but different aplications of it. The third is so different that you MUST use a special resin and heat, or UV, set-up to cure...actually a vaccuum sealed oven is the best way.

Can you find any cracks or damage? If so please describe or post pics of it. Where that damage is on the panel will dictate how you should repair...In the center of the panel, at a corner or bend, or near a seam. Each is different procedure for prepping the repair. But basicaly all of them you need to find how far out, or deep, any cracks are. Then remove the surface down through the crack all the way to every end of each crack. This will allow you to build up the area one thin layer at a time to get the best adhesion (excet SMC must be done at one single time of several layers BEFORE it can set-up).
If there are panels meeting up look for a failure in the seem. If it is coming apart and small you might get lucky enough to get by with some slight sanding and a glue-joint of 3M panel bond. You use that to "glue" in other materials (wood, metal or non-vinyl plastics) as well. Just remember that as the resin sets-up it forces some compounds that are not part of the long-chain building to the surface and if you do not remove all of that nothing will bind very well to the original resin and fail sooner than later.

Try to get a better idea of exactly where the damage is and then i will try to help you put together a plan of attack for your repair.

after looking at some pics and descriptions of canoes it looks like most are a single mold lay-up. If you are that lucky and only have seeping you might look at shooting a gel-caot over the hull to reseal it. Like i said, i need a better look at what you are working with to know.



    Splitting Cane

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Posted 01 May 2013 - 03:38 PM

Thanks for the info. My info on the canoe is limited currently as i don't have the canoe at my house. The brand is a Gazelle which is only about 5 years old. Not sure if that helps any. I'll post picture some time next week.


#4 jumper

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Posted 01 May 2013 - 08:44 PM

If the canoe is truly fiberglass, locate crack and grind both sides<make sure to have proper dust mask or respirator>. While grinding you will notice areas where fiberglass is separated. Remove all separated fiberglass by grinding back till you get to solid working area. Replace with several staggered layers inside and out of fiberglass matte and resin, being sure to get rid of all air bubbles< dabbing with a brush helps in this process>. When dry, sand and recoat with proper finish. Good luck with your project!!

#5 ThomasR

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Posted 02 May 2013 - 01:22 AM

I'v repaired quite a few fiberglass water containers, they tend to get a small impact crack, where water seeps in between the layers.

the trick is to make sure things bond well, so the advice from Jumper is quite good.

what i would do is to apply one extra coat of fiberglass, followed by a coat of pure epoxy to seal it.
1 in 2 weave is quite flexible so should follow the contours quite well.
I would stay away from chopped fabric as that tends to be rough.
160g per square meter (sorry no idea in imperial) should do the trick i think, you can follow up with 40grams 1 in 1 weave to make the top coat a bit smoother (this is harder to bend though).

don't forget to coat with epoxy afterwards to seal the fabric well.

Should you want to go down the fancy route, you can always vacuum bag it wink.gif

one last thing: i wouldn't grind all the way through to fix holes, getting things back into shape is quite hard afterwards.
Personally i would just dry it out, sand roughly, apply 160g/m followed by 40g/m 1 in 2 weave and recoat with epoxy / polyester.
Best regards,


#6 Hatchet Jack

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Posted 14 May 2014 - 03:14 PM

The other folks covered the basics above but I'll throw this in too:

West Systems ~



It discusses in-depth repairs most likely more than you're interested in, but you'll have a good background how

to go about it after studing the PDF. If the hull is 'weeping', it's cracked somewhere too.


A lasting repair takes time and some moohlah. You're going to get a secondary (mechanical) bond so do it to the best of your ability. And I'll throw this in too - before grinding off the old & putting on the new, support the hull in such a way that it retains the original curve(s) & rocker.


Happy sanding scratching! ☺


"Oni byddi gryf, bydd gyfrwys...If you can't be strong, be cunning"

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