Flaky epoxy

[ErktheRed]

I skimmed through some past posts and I didn’t see what I was looking for. Its mostly about full repairs or scratches, and I’m not worried about scratches at this moment. It’s possible I overlooked a post or didn’t read thoroughly.

The hull of my canoe is flaking in sections and I’m not sure the correct way to go about this. It’s also possible that it’s my fault. When I bought the canoe, the outfitter did a quick job of applying new epoxy over the scratched hull. I asked for a boat that wasn’t repaired, but here we are, and it’s fine. I sanded down all of the raised chunks and sharp edges to what I thought was far enough but not too far. I did not go into any fibers while sanding.

Here are some pictures of what I mean


So my question is.. what’s the best course of action for this? Sand it down and renew the epoxy?

Leave it be and paddle it?

Apply a coating over this as is?

 

[pblanc]

Hard to be sure of what is going on. It would be helpful to know what type of epoxy was used to restore the surface finish and what surface prep was done before applying it. If the surface prep was not adequate the bond might have been poor in areas contributing to epoxy flaking off. Some epoxies are prone to water blush which is another possibility. If the involved area of the canoe has seen prolonged UV exposure and the epoxy contained no UV blockers, UV degradation could be causing the epoxy to become cloudy and detaching.

I would probably give the entire hull a good wet sanding and then thoroughly wash it. It may be advisable to use a surface prep and dewaxing agent on the hull before applying any additional epoxy. An example is shown in the link below. I have had good results using a low viscosity penetrating epoxy such as System Three Clear Coat which I apply with disposable foam brushes and which levels very well. After it cures it is a good idea to apply a couple of coats of a good marine varnish with UV blocker.

Surface prep/dewaxer

 

[Boatman53]

I have to say that last pic looks like a Viking in a horned helmet, Eric the Red.
The problem from the pics looks more like a clear coat finish that is pealing and epoxy flaking. Is the company still in business? Ask if they put clear coat over the epoxy. Unprotected epoxy degrades rather quickly in the sun.
Jim

 

[Jim Dodd]

X2 what Boatman53 stated.
Looks like gel coat did not bond well.
Maybe the Outfitter, would warranty for you !

Jim

 

[ErktheRed]

It’s hard to tell, but I did wet sand this with a high grit, but you can see that there’s a few small raised areas that I didn’t sand completely off. Being my first time doing anything like this, second time with sanding a cloth material, I was hesitant on how far exactly to go. But maybe I should call the outfitter, who I don’t speak badly of, these were something to move out quick. And I did get a good canoe out of the deal. But I recall at the time of purchase they used the same stuff that Northstar does. Won’t hurt to garish though.

Is Total Boat’s dewaxer/surface prep ok to use on this?

 

[Cruiser]

I would take a look at the hull where it has peeled off. That gives you a clear view of how the surface was prepped for the epoxy coat.

If it has any shine, they either didn't rough the surface or didn't rough it enough. Regardless of what epoxy they used, it would require proper surface prep or the epoxy will have nothing to hold onto. Basically, to prep the surface you need to remove all the "shine" and create scratches for the epoxy to be able to hold well (similar to varnish), if you don't it starts to peel.

Another thing to consider, is that if they put a coat of epoxy on, what did they add to protect the epoxy from UV ? That would be a requirement for any epoxy then and will be a requirement going forward for you.

 

[Alan Gage]

I'd be curious if it was actually epoxy they used or just some sort of clear coat. I once coated an old composite canoe of mine with an expensive cross linked clear top coat and it looked great until I started peeling the tape and big pieces of top coat came with it. I sanded it all back down and did a better job of surface prep. The 2nd time around it worked fine.

I'm inherently lazy so unless working on a canoe was something I was doing for a good time I'd just paddle it as-is. From the pics I've seen there probably wasn't anything wrong with the original finish other than looking weathered so the top coat just prettied it up. You won't hurt anything other than aesthetics by simply paddling it.

Alan

 

[pblanc]

X2 what Boatman53 stated.
Looks like gel coat did not bond well.
Maybe the Outfitter, would warranty for you !

Jim

There is no gel coat on that boat. At least there wasn't when it left the factory. It is "StarLight" aramid resin-coated layup. Northstar, like most other builders of composite canoes these days uses vinylester resin. That boat is skin-coated or resin-coated with no exterior polyester gel coat layer.

Epoxy should bind well to a skin-coated boat constructed with vinylester resin if the surface prep is adequate. As has been mentioned, this involves sanding the hull so as to provide a "footing" for the epoxy as well as thoroughly cleaning the hull and dewaxing as needed. A final wipe down with lacquer thinner or acetone is also recommended to remove any residual water moisture. And the boat needs to be thoroughly dried, using a hair drier or heat gun if need be.

My guess is that the outfitter who did "a quick job of applying new epoxy over the scratched hull" did not pay sufficient attention to surface prep in this instance.

 

[Glenn MacGrady]

I don't have experience to add because I've never re-coated a canoe with epoxy, but it's not clear to me from the posts so far as to how one protects the epoxy coat from UV. Are there special epoxies for this, do you add some sort of UV inhibitor, do you varnish over the epoxy, or what?

 

[pblanc]

Some epoxies have UV inhibitors. Some don't. The easiest way is to apply a couple of coats of a good marine varnish. Intermittent UV exposures of a few hours duration will take a long time to degrade most epoxies. For boats stored outside or car topped significant distances frequently will see epoxy degradation from UV exposure sooner.

 

[Jim Dodd]

There is no gel coat on that boat. At least there wasn't when it left the factory. It is "StarLight" aramid resin-coated layup. Northstar, like most other builders of composite canoes these days uses vinylester resin. That boat is skin-coated or resin-coated with no exterior polyester gel coat layer.

Epoxy should bind well to a skin-coated boat constructed with vinylester resin if the surface prep is adequate. As has been mentioned, this involves sanding the hull so as to provide a "footing" for the epoxy as well as thoroughly cleaning the hull and dewaxing as needed. A final wipe down with lacquer thinner or acetone is also recommended to remove any residual water moisture. And the boat needs to be thoroughly dried, using a hair drier or heat gun if need be.

My guess is that the outfitter who did "a quick job of applying new epoxy over the scratched hull" did not pay sufficient attention to surface prep in this instance.

Yes, from the Factory, it wasn't Clear coated. Prepping the hull was probably skipped by the Outfitter. If he used either Epoxy or Clear Coat resin ? I think the results would be similar.
I would contact the Outfitter, about Warranty .

 

[ErktheRed]

I’ve been MIA lately, just now taking some breaks. The wife and I have started multiple projects at the same time. A camper van conversion. I new bike build for me. We just put a new roof on. Yard/garden maintenance. The list goes and goes.

I just read through everyone’s responses, two cents and recommendations. I must admit, I was wrong about the epoxy, I e been doing a lot of wood working and epoxy is something that’s being used. I haven’t reached out to the outfitter yet, it slipped my mind, but it won’t hurt. Even though I’m sure I’ll get a “no” response. The guy told me he uses the same vinylester resin that North Star does, but the prep work does look weak. There are some shiny spots beneath. I’m sure these canoes were something to move quick, everyone was hurting financially last year. And they did!

I have no problem using my canoe as is, it functions just fine. But there is apart of me that while driving down the road I want it to look good too. I see some very beautiful canoes driving around, and they’re flawless. As well


I appreciate everything everyone has said, and apologies for responding so late.

P.S. I did fix and river the gunwales, only the first one was scary in not going too far with the drill.

 

[alsg]

Why did the outfitter skim coat the entire boat with epoxy? If the goal was simply too refresh the finish and hide cosmetic surface scratches, going straight to varnish would have been a better solution IMO because once a skim coat of epoxy was applied it was going to need to be varnished over anyway. So the epoxy skim coat just adds weight. Epoxy on a boat always needs to have a UV inhibitor (either varnish or paint) applied over it. Yes, there are some epoxies with built-in UV inhibitors but it isn't likely the outfitter used them and, in any event, those aren't a permanent solution in an outdoor environment (nor are varnishes/paints, which have to be renewed periodically).

Does UV Resistant Epoxy Exist?

Some epoxy can be made to be UV resistant for outdoor application? But for How long? Click here to read more about.

www.zeraus.com

Assuming the outfitter applied varnish over the epoxy, it could be the varnish peeling due to insufficient surface prep.
And If the outfitter didn't apply varnish over the epoxy after skim coating, it is the epoxy peeling. Could be insufficient surface prep or UV degradation from not applying a UV inhibitor.

Regardless, the solution ultimately is to sand everything back down to an uncompromised, intact surface, and then varnish. You say you wet sanded with a "high grit"and left some high spots. Sounds like you weren't aggressive enough. I'd take everything down again with 150 grit to make sure you are down to a uncompromised surface and that there's enough "tooth" for varnish to grip. If you accidentally sand too far in a spot and get into the fabric slightly you can touch that area up with epoxy to seal it. Otherwise, skip the epoxy and just varnish with a good quality marine varnish.

 

[Glenn MacGrady]

Why did the outfitter skim coat the entire boat with epoxy? If the goal was simply too refresh the finish and hide cosmetic surface scratches, going straight to varnish would have been a better solution IMO because once a skim coat of epoxy was applied it was going to need to be varnished over anyway. So the epoxy skim coat just adds weight.

Al poses an interesting question. Can anyone think of a reason, or a rebuttal, as to why or when it would make sense to apply entire coats of epoxy+varnish rather than just varnish for superficial scratches/flakings on a composite hull?

 

[LarrySw45]

Epoxy is expensive. Varnish is not.
I doubt that the Outfitter applied a full coat of epoxy.
Epoxy unprotected degrades in a pretty short time.
Larry S

 

[ErktheRed]

aslg, do you oppose to the idea of an orbital or a mouse sander? I understand either won’t hit the contours right, and I lose the sense of feel with them

 

[alsg]

aslg, do you oppose to the idea of an orbital or a mouse sander? I understand either won’t hit the contours right, and I lose the sense of feel with them

Perfectionists hand sand. I use a random orbit with a soft interface pad on the exterior (and, truth be told, interior as well).

 

[alsg]

Looking at the photos again, this looks exactly like the varnish failure I had a few years back when I was refinishing my cedar stripper. I was using Helmsman over epoxy. I don't know if it was a preparation issue, a weather issue, recoating too soon or bad batch of Helmsman, but after 2-3 coats it flaked off. I sanded it all off and reapplied 2-3 more coats of the Helmsman and it flaked off again. I threw out the Helmsman, sanded it all off again, applied Epithanes and it was good to go.

Two more things about varnishing. First, the instructions will tell you to thin the varnish. Thinning an initial varnish coat is to allow it to get into the wood. Not an issue when varnishing over epoxy. You can and should use it full strength over epoxy -- unless you are having an issue spreading it.

Second, if you thin varnish be careful what you use. Some of the newer, low/no VOC paint thinners/mineral spirits don't play well with varnish. If the varnish manufacturer recommends a specific or proprietary thinner (Epithanes does for instance) make sure you use it. DAMHIK.

 

[Mike McCrea]

Whatever was used I’m going to go with either poor prep work, or incompatible materials.

“Can anyone think of a reason, or a rebuttal, as to why or when it would make sense to apply entire coats of epoxy+varnish rather than just varnish for superficial scratches/flakings on a composite hull?”

Probably not applicable to this situation, but I epoxy coated and then painted the Dirt Magnet Malecite.

“I washed and scrubbed five times to get rid of the weave embedded dirt. Wiped the hull down with acetone. One coat of West Systems 105/206 rolled on and tipped out. The hull seemed quite thirsty and I’m glad I opted to do a coat of epoxy first. Plus that epoxy coat filled most of the exposed weave”

https://www.canoetripping.net/threads/dirt-magnet-canoe-question-ii.85159/

 

[pblanc]

Skin-coated boats have nothing more than a thin coat of resin covering the structural fabric and that gets abraded off. Once the fabric weave becomes exposed the fibers themselves start to become denuded of the resin matrix.

When either the aramid fibers of a skin-coated boat become exposed and denuded of resin the fibers themselves take up water to some degree. This can easily be appreciated because the fabric actually retains a damp feel for some time after immersion.

It seems to me that recoating with some type of resin makes more sense in this circumstance than simply covering the fibers with varnish.