Canadian Canoe Routes

restoring Kevlar canoe - Epoxy did NOT cure????!!!
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Author:  rhader [ August 15th, 2013, 7:30 am ]
Post subject:  restoring Kevlar canoe - Epoxy did NOT cure????!!!

Hey Guys,

I picked up a 10-15yr old kevlar Sorois River Quetico canoe that was in need of some repairs and some cleaning up.

I have built a couple of fiberglass cedar strip canoes so I went to Noahs marine in Toronto and picked up some Epoxy resin that was suggested for typical kevlar builds. I did a bunch of fine sanding and filled in a bunch of spots - all went well...

Now I sanded the whole canoe for a final thin coat of Epoxy resin to clean everything up before I gave it a prime and final paint coat.... As I am planning on painting it to cover up all the 'touch ups'...

Now I sanded everything and it all looked great! BUT when I applied the epoxy resin coating it was nearing 9pm I have a semi finished shop plenty of room and hydro 70% insulated - but didnt think too much about it as it is August and should be fine. Temps between 20C 70F or there abouts atleast inside the shop.

Now the next morning when I checked it 60% of the resin did NOT cure / harden... WTF??? There was some left over in the container I had used that cured no problem so what happened?
Temperature drop overnight? that night it did drop to 11C or so but being inside the shop it doesnt reach that temp at all... so should have been fine....???

I gave it another day sitting in the shop and nothing. When I could I mixed a second batch making sure I was measuring the hardner as accurately as possible and thinly coated the areas that did not harden - again this is about 9pm now... I had started a fire in the woodstove this time to try to keep the temps up a little more and it was warm in there!!
Now checked it this morning and although MORE of the resin had cured there is still 20 - 30% that did not and is still tacky and wet...


We are planning on using the canoe the last week of August and I need to get it finished this weekend....

any thoughts???

I am hoping it warms up today and I can let it sit in the sun???

Author:  pblanc [ August 15th, 2013, 10:04 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

What brand of epoxy are you using? Does the maker have a website with some type of support and contact info? If so, I would contact them.

Had you applied a prior coat of epoxy before this final coat? If so, did you wash or sand the boat before the final coat? If not, it could be an amine blush retarding the cure.

Otherwise, if it appears that the epoxy is curing, albeit slowly, I would continue to just wait. I have encountered situations with various epoxies curing much more slowly than anticipated in which they eventually did cure.

Author:  rhader [ August 15th, 2013, 10:39 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

sorry I should re-phrase that. It is a POLYESTER Resin....

I believe it i s a 'waxed' resin but I will double check.

And no I had not applied a prior coat of epoxy before this at least on the entire canoe... I had touched up the bow and Stern which had previous repairs that were simply butt ugly.. I cleaned them up made them look nice and filled in some other repair spots to even everything out.. .but I had not applied a coat to the entire canoe... This was the first coat that I had applied a coat to the entire hull of the canoe.

I spoke with Noahs Marine they suggest that I give it some sun and some heat and hopefully it should cure. I did not realize but I guess I can add some extra hardner next time to ensure curing on colder nights...

any thoughts?

Author:  littleredcanoe [ August 15th, 2013, 11:07 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

You might check out the differences re epoxy vs polyester resin. To complicate things it seemsSR boats are epoxy rather than polyester resin coated.

Author:  pblanc [ August 15th, 2013, 12:13 pm ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

I don't have any experience with polyester resins but I am informed that the ratio of resin to catalyst might need to be adjusted for ambient temperature. I suspect that conditions were such that your mix was somewhat catalyst-poor but will eventually cure.

For future work I would strongly suggest using either epoxy or vinylester resin. ... yester.htm

Author:  rhader [ August 15th, 2013, 12:19 pm ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

hindsight being 20 / 20 it seems that would be the case... I am not sure why the guys at the shop suggested the Polyester resin instead... I am going to try to give it some heat with both sun and heat gun and see how that fairs / cures....
With any luck it will work...

That being said Now that it has taken so long to cure it has caused some runs and some spots that will definitely require some sanding. Should it be re-coated with a resin?? and at that should I switch to an Epoxy resin??

Author:  Marten [ August 15th, 2013, 8:31 pm ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

I have had this problem in the past and believe it has to do with the thin coating. To make a thin coating set you can put cellophane over it or spray it with a special coating that is removed later. I hope someone with the proper terminology weighs in on the subject.

Author:  Canoeheadted [ August 16th, 2013, 1:53 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

Stop putting layers on and let this stuff cure up.
Do this kind of work at 9:00 am not pm.
Of course you can up the hardener.

I'm not too sure about fiberglass but there are specific cold temp. epoxies out there that work great. It's what I use up here just for that reason. Cold Cure is what I have now. (it used to be System Three)
Your SR is epoxy. If you really want then sand it down to eliminate the runs and scuff up the smooth stuff and go over it with a skin coat of epoxy. She'll be brand new.

Author:  rhader [ August 16th, 2013, 7:17 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

To all and Canoe head. I placed the canoe outside in the sun for a couple hrs when I got home from work and it definitely seemed to do wonders the one side at least where the sun was beating on it and hardened more of the coat up.
Still a little tacky in places I brought it back inside and started the woodstove got the shop up to a good 30C which of course is much more sitting directly in front of the woodstove... I then took my wife's hair dryer and went over as much of the tacky spots as I could in the next couple of hours...
At the time it didn't seem to be hardening to quickly but I checked it this morning and it is much better.
Now I put it on a table with wheels so my wife could push it out in the sun for the day when the sun comes up as I generally leave at sunrise or shortly before (ugg)....
Hence not trying this before.

And yes thank you - obviously it would have been ideal to start the coat at 9am not 9pm... I am limited to evenings and weekends and it just happened to be 9pm by the time all the work was done on the canoe last Sunday where I could actually coat the entire canoe...

So now I am hoping this evening after a day in the sun it will be good to go???

Now that being said I will need to give a good sanding due to the mess that it has made... Should I re-coat with an EPOXY resin??

and at that what system EPOXY resin should I be looking for??? a COLD cure epoxy resin??

Many thanks guys!

Author:  littleredcanoe [ August 16th, 2013, 7:51 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

I suggest going paddling and let nature do the sanding. I don't know about the adherence properties of epoxy over poly resin. You might be making a deeper hole.

Some years ago we made a similar mistake. Epoxied a Wenonah that had a vinylester skin. It took a while to dry. When we realized our mistake we just paddled it. Now its ready for some more new skin as the interim mistake has worn off. We didn't seem to have an adherence problem but like you we had runs..not a big deal. They went away with wear.

What I would like to see is some references as to what resin bonds to what resin and what does not seem to work. Materials sometimes befuddle me.

Author:  rhader [ August 16th, 2013, 7:56 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

Hey LRC,

Yeah I would do that except that now it does look like a complete mess due to the hardnening disaster (which isnt quite over) and I was planning on painting it with a primer and a paint to cover up the patches that I had made. Not to mention to cover up the discolored coatings that the rental shop (Killarney outfitters) had used previously. Im not sure what they used but they just slapped it on and it discolored the canoe quite a bit.

So my plan was originaly this:

1) patch it all up (done)
2) then give a good solid coat of resin (F`d that up)
3) prime it
4) 2 coats of final paint...

SO that being said - I will need to sand this polyester resin down and should I re-coat it with another resin? either more polyester / or Epoxy?? I should mention that this is also a WAXED Polyester Resin. I am not sure if that changes anything?

Author:  rhader [ August 16th, 2013, 7:59 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

I also did some reading and found lots like this:

so bottom line is POLYESTER Resin is terrible... I have no idea why the shop recommended it..

In future Use Epoxy or Vinylester I guess...??

Author:  littleredcanoe [ August 16th, 2013, 8:17 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

No insight onto the prep process but our house was covered in oil based stain. Its rough sawn sanding there. The new stains are not oil based and will not penetrate the wax layer of the old stain.

Hence my husband scrubbed off the entire house..manually with TSP. That took a year.

If you sand off. use what SR does..Epoxy.
You can color me confused.. Paint over epoxy? Why not just sand the thing now and apply paint? Too many layers of stuff and you will add significant weight.

Author:  rhader [ August 16th, 2013, 8:31 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

Well there is no way I can sand off everything I was actually molded the Bow and Stern using this stuff as there was some ugly repairs that had some gaps - I spent some time doing this and there is no way that I could remove this without destroying the canoe. I could likely get MOST of the coat applied on the entirety of the actual hull but that's about it.

I picked up a marine paint and primer the primer will help for bringing out the color. The reason for the coloring of the canoe was just due to how discolored it was from the previous 'repairs' from the Outfitters repairs...
As it is a light canoe I will weigh it when finished but I am OK if it adds a little bit of weight and strengthens the canoe and lasts for the next 20 plus years...

Author:  pblanc [ August 16th, 2013, 9:03 am ]
Post subject:  Re: restoring Kevlar canoe - Epoxy did NOT cure????!!!

I am reluctant to offer much advice because I have no experience with polyester resins.

Here is an excerpt from "The Epoxy Book" published by System Three epoxies:

"Caution must be observed when using epoxy resins along with
polyester resins
. Observe the general rule that epoxy resins may
be applied over cured polyesters that have been dewaxed and
well sanded but polyesters should never be used over cured epoxy
resins. Unreacted amine in the epoxy inhibits the peroxide cata-
lyst in the polyester causing an incomplete cure at the interface.
Sanding does not get rid of unreacted amine. The result is a poor
bond even though the surface appears cured. Debonding
will be
the inevitable result. "

The Epoxy Book is a fair resource for those working with epoxies: ... y_Book.pdf

It may be that unreacted amines in the epoxy resin of your SR are interfering with the cure.

If you have no further structural issues to deal with what I would do is nothing for several weeks other than the keep the boat as warm as possible. For epoxy resins the cure rate slows after the resin leaves the liquid state and gels and cure may continue for several weeks. I assume the same might be true of polyester resins.

After a few weeks when the resin is presumably as cured as it is going to get I would wet sand the entire boat starting with 180 grit paper and proceeding in stages down to 600 grit or so. If you are painting the boat you don't need to go finer. I would then thoroughly wash and scrub the boat with soapy water, rinse, and go over the whole thing with denatured or isopropyl alcohol and a lint-free rag.

I would then apply a quality "Hi Build" marine primer such as thus made by Interlux or Z-Spar (Petit), and again wet sand and wash. The primer should fill in any low spots. Cover with a quality one or two part marine polyurethane paint. Don't worry about using conventional marine polyurethanes "beneath the waterline". Admonitions against using these paints below the waterline pertain to boats that reside in the water continuously for prolonged periods of time (weeks or months) which canoes usually don't.

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