Canoe Discoloration Mystery Question

[Mike McCrea]

This is the discoloration in question:

IMG-0232 by Mike McCrea, on Flickr

The backstory. That is a glass and polyester canoe, and it blemished in that fashion when new and little used. The manufacturer replaced it with an identical glass & poly canoe, which proceeded to do the same thing.

The same make/model canoe was bought at the same time in kevlar and did not discolor. Both stored side-by-side under a carport in Florida. The discolored glass & poly canoe has dark green gel coat, the unblemished kevlar version has a much lighter Sand colored gel coat.

My immediate thought was that it looked like bacterial surface growth, some dinoflagellate, algae or protozoan from a scummy water trip, or even some airborne pollen or pollutant combined with Florida humidity to form a canoe Petri dish.

Brush scrubbing the inside with a magic grime remover solution of white vinegar and Dawn did nothing, and that mix will take off even the toughest grime. The discoloration seems to be encapsulated under the resin or in the cloth.

Both canoes were factory fresh hulls, but unlike the easily dimpled foam core on a brand new Royalex canoe, I have never seen a “freshness” issue with a composite hull. Maybe still smelling faintly of resin, but that quickly faded, and I think of it akin to new car smell.

It could be the temperature difference between Dark Green and Sand colored gel coat, but that doesn’t seem likely, or it would be a more common issue in hot or sunny climes.

Same for the difference between a kevlar layup and a glass & poly build, that discoloration doesn’t appear to be a common issue. We have glass & poly canoes, and I’ve worked on a bunch of others, some decades old, and I have never seen that mystery before.

Has anyone seen that kind of encapsulated discoloration before on a composite hull before? Any ideas about how, what, why?

 

[Glenn MacGrady]

Never saw this on a canoe, but fiberglass boats in Florida frequently get brownish or rusty stains from organic materials in the water such as tannins. One cleaner used is Star Brite Instant Hull Cleaner, which is mostly hydrochloric acid, so wear gloves and a respirator.

Another possibility is a chemical reaction with the resin formulation used in the glass/poly hull, which presumably must be different from the formulation used in the Kevlar hulls. Why not ask the manufacturer?

Not clear exactly what the picture is showing. What are the green areas interspersed with the stained areas—paint?

 

[Mike McCrea]

Glenn, it is definitely encapsulated in the resin and fabric, not removable on the surface by scrubbing. The manufacturer did not have an explanation for the embedded discoloration.

“Not clear exactly what the picture is showing. What are the green areas interspersed with the stained areas—paint?”

There is no paint anywhere on the canoe. The lighter areas are the original hull interior, the darker areas are the embedded discoloration that developed. There may be some clue in that the discolored areas are somewhat banded laterally across the hull.

The dark green/black(?) areas along the sides are some OEM reinforcement on the chines, maybe graphite.

My best guess at this point is that it was some combination of factory fresh resin and Florida heat and humidity.

 

[Woodpuppy]

We can mess up about anything down here in Florida. Factory fresh or not, I would expect the internal layer of fabric and epoxy/resin to be water and air tight. I’ve never seen that in a canoe, but plenty of unsealed foam in boats takes on that sort of mottling. My vote? Paint it so you don’t have to look at it!

 

[yellowcanoe]

We can mess up about anything down here in Florida. Factory fresh or not, I would expect the internal layer of fabric and epoxy/resin to be water and air tight. I’ve never seen that in a canoe, but plenty of unsealed foam in boats takes on that sort of mottling. My vote? Paint it so you don’t have to look at it!

It looks like mold in the foam stiffeners encapsulated by the epoxy and resin to me. Uglee for sure. Do you think so and is it possible that there was too much moisture in the foam when it was encapsulated?

 

[Woodpuppy]

It looks like mold in the foam stiffeners encapsulated by the epoxy and resin to me. Uglee for sure. Do you think so and is it possible that there was too much moisture in the foam when it was encapsulated?

It’s certainly possible. And the same stock of foam, assembled into a canoe in the same environmental conditions, should produce the same results. As in, not surprising it happened to the replacement canoe as well?

 

[goonstroke]

That banding must be a clue. Is that a seam between two sections of foam at the front of the ribs? Or is the laminate more porous there for some reason?

Could they have vacuum bagged with not quite enough resin, so the inside is not totally wetted out / sealed? It'd be hard to test that theory without possibly making a contrasting stain.

I think it looks a bit like cinnamon. Too bad green doesn't really work with a cinnamon roll.

 

[Mike McCrea]

The lateral banding of the discoloration does seem a clue.

I had not considered the possible presence of moisture in the foam or fabric during manufacture, and with the blotchy appearance of the discoloration that, combined with moisture and something bacterial in the air during layup, and sufficient Florida heat soon after manufacture, may have been the perfect storm to create Petri dish conditions encapsulated in the resin.

Thinking about that theory, laboratory incubators can be set to control humidity and CO2 levels. Perhaps a combination of new construction, moisture in the layup, incanoebator conditions and voila, a new cell line is born.

I have e-mailed some further questions to the owner; how quickly the discoloration occurred, and whether it started small and continued to grow, were the original canoe and the replacement manufactured at the same time. I believe the original was purchased factory fresh from an outfitter, and the replacement plucked soon after from that outfitter’s racks.

If this is or was some bacterial growth encapsulated in the fabric or foam I’m curious if it may eventually weaken the layup or structure of the canoe. I have heard/read that one layup advantage of a glass/polyester build is that Vinylester resins will chemically bond with the poly, kind of dissolving a bit of the poly surface for improved adhesion. Perhaps sufficient moisture would cause patchy bonding and leave pockets for bacterial growth?

It would be nice to hear from someone with composite manufacturing or lamination expertise. Where is CEW when we need him?

 

[yellowcanoe]

Calls for a movie: "The Invasion of the Foam Eating Mold" along the lines of flesh eating bacteria. I can steal the pic and e mail CEW.

 

[Mike McCrea]

Please do. If anyone would know it would be him.

My current man on the grassy knoll theory is that a factory worker with a head cold sneezed in the hull during lamination and created an invasive canoe cell line, which will eventually escape, devouring neoprene booties throughout south Florida.

The fungus is already amongst us.

 

[Glenn MacGrady]

Who is the manufacturer of this mystery canoe? How old is the canoe?

I take it this canoe is not in your shop and you have not tried commercial acidic washes (hydrochloric, muriatic), bleach or acetone to further test the encapsulation-under-the-resin hypothesis.

The picture is at an odd angle. It that a foam diamond bottom with ribs? Is the discoloration only on the foam parts of the interior hull?

I have a new hypothesis. The dark stain is water—trapped water. If the canoe was upside down for a long time in heavy Florida afternoon rains, water could have accumulated under the aluminum gunnels, saturated the exposed edges of the hull laminate and foam ribs, and then wicked up the hull in the summer heat that follows the rain, especially along or within the foam. If the canoe was under trees, wicking rain water could also contain organic particles.

 

[Mike McCrea]

I’m not going to name the manufacturer; they build great canoes, and have for more than 50 years; this is a mystery anomaly. No doubt some folks here recognize the construction and layup. I believe the canoe is now a few years old, but the discoloration, or at least initial discoloration, happened almost immediately.

I believe the canoe has foam ribs, and some graphite on the chines, but I have only seen a two photos of the boat and the other is little different, although the discoloration is more widespread. The discoloration is throughout the hull, not just on the ribs

I am confident that the discoloration is encapsulated under the resin. Someone more canoe knowledgeable that I, who has seen it firsthand, declared it to be so even before the Dawn and vinegar scrub.

The trapped water hypothesis is a possibility, but I’d think the odd discoloration would a more common occurrence. I’ve never seen this before, and since purchase the canoe has been stored under a carport.

I have asked a couple of specific questions of the owner, but doubt the answers will shed further light.

 

[Glenn MacGrady]

It's a lot harder to find a missing car when the make is not named. So, I'm going to assume this is a Wenonah until told differently.

That tells me the canoe is vacuum bagged.

The discoloration is throughout the hull, not just on the ribs

If the cryptic dark areas are throughout the entire hull and aren't some sort of injected material, chemical reaction or trapped water, there logically would seem to be only one thing left: the resin itself. Perhaps the mottling is due to areas of thicker and thinner resin, caused by a leaking or otherwise faulty vacuum bag process.

the discoloration, or at least initial discoloration, happened almost immediately.

Based on the facts recited so far, this is clearly a manufacturing defect. Aesthetics are important. I would have demanded a replacement, or multiple replacements, until I got a flawless canoe or a big blem discount. A large company like Wenonah, with an important reputation in canoe racing and recreational canoeing, would surely have made good.

 

[Woodpuppy]

The discoloration is throughout the hull, not just on the ribs

Ah! I didn’t realize that. I thought it was only on the foam. The green color of the hull’s exterior (gel coat?) obscures the splotches where there is no foam.

Perhaps a contaminated batch of resin or fabric used on the interior? The width-wise linear appearance of the splotches suggests something about the resin and the way it was rolled on. The fabric weave angle would change from the middle of the boat where I’d expect it to be fairly perpendicular to the length of the boat and skew/stretch as you approach the ends. But we can only see the middle of the boat in this pic.

Does the linear nature of the splotch pattern remain perpendicular to the length of the boat, or does it follow the weave of the fabric? The answer to that question might support fabric vs resin contamination.

If the manufacturer was willing to warrantee replace the boat, I would bet they have a range of affected models / serial numbers nailed down. Not many would be happy about their new expensive boat turning colors like that, so I expect they’d have heard from the boat owners.