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 Post subject: Gelcoat
PostPosted: May 2nd, 2006, 12:53 am 
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Could you: Mix epoxy with food dye to repair a gouge?


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PostPosted: May 2nd, 2006, 4:49 am 
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Not sure about food dye. Food dyes probably have poor UV resistance and may fade rapidly.

Many years ago I used to use the paint pigments from the paint stores to match faded colours on yacht repairs. Could not do bright colours but they did work and hold up for a few years.

No matter what you use you should test first. If it were me I would repair the scratches and then paint over the repairs. These days you can get little spray cans of automotive paint in a huge range of colours, They are easy to use, cheap, adhere well to prepared surfaces, come in a huge range of colours.

I am often baffled by people wanting to repair boats with gel coat etc. The professionals use patching pastes (similar or the same as auto body putty) and then paint. Gel coat is really poor stuff from a peformance standpoint an is really just a convenience for builders. If you buy one of those custom built yachts for big bucks they would never insult you by using gel coat. They use two-part polyurethanes.

Unless you have a canoe built with epoxy you have no need to use it for repairs. Buy some auto body patch and a paint can and Bob's your uncle.

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 Post subject:
PostPosted: May 2nd, 2006, 9:12 am 
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When you say "a convenience for builders," I am assuming they spray it in to lessen the amount of finishing required, but doesn't it also function as a sacrificial layer to withstand abrasion? With a canoe that doesn't have gelcoat, how deep can the scratches be in comparison, before repairs are needed? eg. one of the ultra-light kevlar or carbon kevlar canoes.

I am familiar with motorcycle racebike fibreglass bodywork and it's repair, but not so much with canoe construction, so I hope this isn't a dumb question!


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 Post subject:
PostPosted: May 3rd, 2006, 6:37 am 
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robertm wrote;

Quote:
but doesn't it also function as a sacrificial layer to withstand abrasion?


One could look at it that way but it is pretty poor at doing it, so poor that most people put bang pads on the bow and stern.

Gel coat is heavy, has almost no structural value, and is brittle. It develops cracks where there is flexure or impact.

It does serve to protect against UV penetration but that is better done by polyurethanes.

That said, it does not mean builders are unscrupulous for using it. A two-part polyurethane finish would be a huge improvement but would elevate costs and most canoe companies are cost sensitive. Apparently they believe that most customers would refuse to pay for a better finish.

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 Post subject:
PostPosted: May 18th, 2006, 11:07 pm 
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Asked the manufacturer of my canoe if they sold a repair kit...advice would have been appreciated also. They were kind enough to respond
Herewith:

.
[/quote]We do not sell a repair kit so you either do a crude repair yourself with
marine epoxy or take the canoe to one of our stores so the damage can be
professionally repaired by one of our repair technicians.
Quote:
Hope I can manage a "crude repair" ....took Winter's advice; used Bondo, so far so good. Too cold and humid to paint yet.


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 Post subject:
PostPosted: May 25th, 2006, 8:42 pm 
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So far, hog diggety dam, so good. Bondo is quite easy to work with, a bit hard to cover without primer...unfortunately I didn't think I'd need same as it isn't metal. Mismatched the paint but that's easy to rectify. Feathering the paint is a tad difficult. Find out next year the durability of the repair.


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 Post subject:
PostPosted: May 17th, 2007, 10:33 am 
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Location: Brantford, Ontario
any update on this thread or technique? my Langford lost its' smooth skin this past weekend.
Somehow in Killarney we managed to cause 3 damage spots. The canoe was pretty lined by 3 years of use, but this is different:

1. A gouge into the kevlar about the 1/4 inch round
2. A furrow that isn't thru the gel but looks like an indentation I'd make with a spoon handle, about 2 feet long
3. 2 spots where there is cracking of the gel, both about 3" long, one rounded silver dollar size

We field patched the worst spots with waterproof tape, but now I want to repair it. I am afraid water will suck intot he cloth in all three. Suggestions?

1. Bondo then paint
2. bondo then paint
3. ? Bondo a thin skin over the cracks then paint?

Marine supply best for source or just auto supply stuff?

thanks for your help experts.
Mark

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 Post subject:
PostPosted: May 17th, 2007, 11:02 am 
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Location: Bancroft, Ontario Canada
If the damaged areas don't feel soft or mushy, the glass and kevlar is probably still OK and epoxy plus some kind of filler should be able to fill in the gouges and low spots... the area should be dried out well and sanded to give some "tooth" for a better bond. Epoxy on it's own will probably fill in the cracks in the gel coat... any loose gelcoat should be removed and filled with the above mix.

If the cloth layers have been damaged and the hull has gone soft, additional cloth has to be applied, it sounds like this won't be necessary.

The hull and epoxy and filler should be washed off with a detergent, rinsed off and dried well, then the entire hull sanded smooth and painted. Or just the repaired areas could be painted if appearances aren't needed too much.

Good luck, hopefully that's enough info.... the epoxy and filler material should be available at a marine or auto repair place. I've never used Bondo so can't comment, it might also do the job, if filling low spots is all that's needed.

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 Post subject:
PostPosted: May 17th, 2007, 7:48 pm 
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Location: Brantford, Ontario
great info - the damage is fresh so no mush. the part that is more of a crack in the gel coat moves up and down slightly so it'll need to be chipped back enough to fill I suppose. Hate to do it but I guess it is similar to a drywall crack and won't fill by going over it thinly. sound about right? Epoxy sounds right . Thanks.

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As twilight drifts to even.
- Pauline Johnson -


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 Post subject:
PostPosted: May 30th, 2007, 3:46 pm 
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Location: Wellandport, Ontario
Bondo is ok but I don't find it durable. For gouges and scratches I have had good luck using epoxy resin and Cab-O-Sil to thicken it.
Lightly feather the damaged area then scuff with 120 grit paper to promote adhesion. Mix the resin per directions then add Cab-O-Sil to get a consistency between soft butter and peanut butter. Apply the mixture with a body spatula (buy cheap ones at Canadian Tire) and try to leave it smooth and just proud of the surrounding area. Once the epoxy has cured use 320 grit paper to smooth the area out.
Some info on Cab-O-Sil: http://www.eagerplastics.com/cab.htm
Noah's Marine carries Cab-O-Sil and epoxy resin.

Dan


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 Post subject:
PostPosted: September 12th, 2007, 1:23 am 
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Update: The bondo is still hanging in after a year. Has a scratch in it that's all. The auto paint is fine.


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 Post subject:
PostPosted: September 12th, 2007, 7:28 am 
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Since I posted earlier thought I'd pipe in with my fix - the missing spots of gel, chunked holes and anywhere there was a substantial gouge I filled with a putty from a marine store. It comes in a tube, with an inner and outer mixture. You break off a chunk of both layers, rub together and then apply. It forms a "tenacious bond" according to the instructions, can be used underwater (for cruisers & sailboats). I decided I had so little damage I wouldn't do the "big fix" but what needed doing, had to be done. Just 5-6 smallish spots.

So 4 months later and this stuff works really well. Not permanent I guess but I can see my entire gelcoat will need done in another year anyway. I received some great advice when that time arrives. The patches are pretty smooth, maintained the original fix, easy to use, cheap; it dries grey on my yellow boat but that is ok for now too.

I still have a severe concern that it takes so little to crack my gelcoat and as JW eloquently states, seems like a very poor finish for a quality boat. We have become so careful around rocks and getting in/out of the canoe it is ridiculous sometimes.

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Midway 'twixt earth and heaven....
Above, below
Drift with my drifting, dim and slow,
As twilight drifts to even.
- Pauline Johnson -


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 Post subject:
PostPosted: September 12th, 2007, 8:47 am 
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Hi Guys,

We have some damage on our canoe that goes down to the Kevlar. The gel coat and other layers above the Kevlar have come off (we think it was done with a hammer) but the Kevlar is not damaged. This is on the lower part of the hull.

I have purchased a West System Epoxy Repair kit. It is called the Maxi Repair Pack and it is a resin and hardener. I could not get the color match gel coat repair kit shipped across the border.

My question is.... from what I have read here... am I correct in thinking that using this repair kit and topping with some automotive paint should be enough for a good repair that will be durable and long lasting? Please correct me if I am wrong... I don't want to screw up the repair.


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 Post subject:
PostPosted: September 12th, 2007, 5:40 pm 
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Location: Milton on.
wild; add some microbubbles or other filler to the epoxy, smear it in a little higher than the surface, sand it flush and spray it. I've done this with my Scott several times and my old" green monster" had almost the entire bottom done this way at one time or another. :doh:
A little tip- if you can take a flake of the gelcoat to the auto store and try to use it to match the colour ( my scott is chrysler emerald green :roll: )


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 Post subject:
PostPosted: September 12th, 2007, 8:08 pm 
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scoutergriz wrote:
wild; add some microbubbles or other filler to the epoxy, smear it in a little higher than the surface, sand it flush and spray it. I've done this with my Scott several times and my old" green monster" had almost the entire bottom done this way at one time or another. :doh:
A little tip- if you can take a flake of the gelcoat to the auto store and try to use it to match the colour ( my scott is chrysler emerald green :roll: )



thanks ScouterGriz - there is a filler in the kit so we can use that and I'll see if a flake comes off - if not We-no-nah said they'd sent me a color swatch. Bryan will have to do the repair as I am not comfortable using anything with odors right now.


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