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 Post subject: Gelcoat Repair
PostPosted: May 24th, 2005, 7:45 am 
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Joined: May 2nd, 2005, 9:40 am
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Location: Richmond, ON
I am planning an 8 day trip down the Esnagami and noticed a few chips in the gelcoat of my fibreglass canoe. They aren't big (not even the size of an end of a pencil). I can see the fibreglass but it is not damaged. My concern is that it is located in the bow where the canoe takes the brunt of the blows from rocks.

The question is: Should I repair these small scratches before more damage is done or should I wait till it starts penetrating the fibreglass?


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PostPosted: May 24th, 2005, 9:32 am 
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Location: Bancroft, Ontario Canada
If it's a good canoe and appearances matter, I usually repair and paint soon after. If it's an old bashed-up hunkajunk, the repairs can wait.

It sounds like appearances matter since you've noticed some minor dings. If there's a chance that water could be getting under the fiberglass and causing some delamination, probably best to repair. If the dings are still waterproof, you might be able to wait until after your trip and then repair any additional damage that's on the hull. Hard to say without actually seeing the damage.

Either way, you should have some repair materials on hand if you plan on doing the repairs yourself, and now might be a good time to start.

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PostPosted: May 24th, 2005, 9:53 am 
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Appearances are not important to me, I just don't want these scratches to go any deeper. Last year our friends put a hole in their canoe. Fortunately it was on the last day of our expedition.

To repair it I hear I need to sand it down, activate the old gelcoat with Styrene then work gelcoat paste into the v-groove. Does this sound right?


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PostPosted: May 24th, 2005, 10:25 am 
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That sounds about right, except that wiping down with acetone first is sometimes recommended to clean off any oils or waxes in the area so that the styrene won't be blocked. In theory, the styrene is supposed to soften the base gelcoat so that a chemical bond can form with the base and the repair paste. This is supposed to be like welding the two together rather than a mechanical bond only.

Some use the gelcoat repair paste only, without styrene, after roughening up the scratch with sandpaper and they've said it bonds well enough. I've used an epoxy with filler mixed in the same way.

If the paint's going to be a gelcoat paint, it probably won't bond well to epoxy. I used a two-part polyurethane (Endura) to paint over and that bonds well to both gelcoat and epoxy.

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 Post subject:
PostPosted: June 5th, 2005, 9:06 pm 
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Location: Sudbury, ON
frozentripper, it looks like endura recommends a primer coat http://www.endura.ca/marine.htm.
Did you get away with a topcoat by itself and how well has it stood up to abuse?

roddy


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PostPosted: June 6th, 2005, 10:39 am 
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Roddy, that link doesn't work, but I read the marine info at the Endura website.

As far as I know, two-part polyurethane paints such as Endura are compatible with polyester gelcoats, as long as the gelcoat's washed and rinsed free of any grease and oil, then sanded well to provide a good surface for the Endura to bond to.

The primer is used mainly to fill in scratches and craters, then smoothed with sandpaper. Endura dries very thin and will not hide surface imperfections like gelcoat will, so the primer may be necessary for a good finish. Regular epoxy can also be used as a filler/primer over gelcoat if you've got some around.

I went with Endura purchased from Smithcraft in Toronto and their instructions, with good results and a durable finish. You can also contact the tech staff at www.endura.ca and see what their recs are, chances are they'll recommend filling surface imperfections with the primer first. If a perfect surface isn't important, the primer probably won't be necessary.... worked well without primer for me, with a finish that was good for several years.

Rick

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 Post subject:
PostPosted: August 11th, 2005, 7:52 pm 
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Location: Barrie, Ontario
For the most part, gelcoat is not structual, as the gelcoat offers little but a cosmetic finish and an easy way for the manufacturer to get a nice looking part out of the mold. If the fiberglass underneath is in good shape, it will likely survive well without further repair. Of course if you are picky about your boat.....

...for repair, dewax/degrease with something like actone or new laquer thinner and a clean cotton cloth. Sand the area with something coarse. If any chemical bond is going to happen, it will be only moderate with the little bit of incompletely cured resins from the original construction. Otherwise the bond will be mechanical, which is why cleanliness and abrasion are so important. Try not to sand much at the underlying fiberglass, that is the real structure of the boat. Fill in with waxed gelcoat, allow to cure, sand flush and polish.

All of which sounds much less time consuming than it really is...


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 Post subject:
PostPosted: August 12th, 2005, 7:05 am 
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Location: Richmond, ON
Yeah I just found out about the gelcoat being cosmetic. I had put it on and tinted it but it didn't really cover the off-color fiberglass resin. I don't mind the brown patches on my green canoe anyways...battle scars.


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 Post subject:
PostPosted: August 12th, 2005, 2:12 pm 
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Location: Brampton, Ontario Canada
I gelcoat and repair all cracks in the gelcoat. I must have a dozen or more green shade colours to mt green canoe. I do use a Turtlecar wax and the wax crayon that omes with it to wax my canoe every spring. It make the canoe look better and for the first trip out it seems to be faster but the multi green colouring is still there.
Bill

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