Should a fillet or any other area filled with epoxy/wood flour mix be dentable or diggable with a thumbnail 3 years later? Some spots are even softer than that! It sure seems that some areas are actually badly mixed bondo,,, while chizelling it out, occaisionally got a whiff of styrene,,,tho mostly it smelled "oily". HELP! These are the predominant areas that the fiberglass is peeling and cracking.
Not sure why you have this problem, but no, it should never be that way. Was it exposed to the sun without UV protection? Was it always this way or a new thing?
I recently got this boat. A weekender built about 3 years ago. I've found a lot of interesting quandaries. For instance, the joint at the bottom and transom mated at the inside corner, ie. L then was filled and rounded over. I can dent those areas 1/32 with my thumbnail, more at some places. The same with the fillet along the keelson. Unfortunately, there are also areas like that along the chines too,,,, <sigh>
Are you sure it's epoxy and not an adhesive/sealant like 3M 5200. Though 5200 can become quite hard, it's never going to be like a rock. This is a common material to see used in a Weekender.
Cut a slice off of the boat and look at the cut edge. If it looks white or nearly so, it's probably a sealant.
Epoxy can tolerate considerable mixture deviation, but if it's off enough to prevent the reaction from happening, then you usually just get a goo, sometimes with a skin on it, but a goo underneath.
Epoxy breaks down from UV, but doesn't get gooey. It changes color until it physically looks burned (it is actually), the surface becomes very rough and it's extremely brittle after prolonged exposure.
Can you post some pictures of the stuff?
From the smell, it seems Paul has the right of it.
This stuff, for the most part is light brown, some more pinkish, like a weak mix of bondo,,,there were some areas so soft, I could roll it between my fingers,,like plumbers putty! I'll get some pictures today.
I wonder if it could be waterproof caulking material. That sometimes comes in bone, light brown, or other tints, for bathroom applications. If the builder couldn't find 5200, they may have used it as a substiute. Just a thought.
Greg
I've heard heat can soften Epoxy,,,,how soft would it be at 85 to 90 deg?
And does it , like most things, expand when it heats up?
Epoxy will lose approximately 50% of it's tensile strength at 150 degrees, but doesn't soften, nor does it melt. It will burn, but these temperatures are much more then sun light can provide.
Up to about 120 degrees you're "post curing" epoxy, which makes it harder initially. At 140 degrees there is no noticeable difference in softness or tensile strength.
It's possible they used polyester resin with a bad mix. Unlike epoxy, polyester is quite sensitive to it's hardener content ratio. A "lean" mix will not cure, but remain putty like. The amount of hardener missing from the mixture will determine the puttyness of the batch. It's also a common beginner mistake to not mix well enough, leaving resin or hardener rich areas within the batch. This is why they use two different colors, so streaks and less then well mixed areas can be seen.
When mixing epoxy, pigments or any reasonably viscous liquid, I use a flat plate, rather then a cup or mixing tub. It's too easy to leave unmixed goo in the corners of a cup or tub. I smear the ingredients on the surface and scrape it back and forth with long strokes, "folding" it in on each stroke. This is the way printing press operators mix their colors, before placing in the press. It insures a complete mix. Any areas not mixed well are clearly visible as streaks and can be "folded" back into the rest for mixing. This technique has the side benefit of spreading out the epoxy in a thin sheet, which keeps it from building up heat and causing it to kick off sooner then necessary. I can increase the working time of the goo by 40% with this technique, more on large batches.
That's a great technique to know. So far, my only epoxy experience is in construction use, not coatings or boatbulding, fiberglassing, etc.
I am familiar with bondo though, and have seen situations where it remained "less than fully hardened"