discoloring of wood after fiberglassing

[WJWBoats]

I am a first time boat builder and am building 15ft Bobs special and have run into a problem. After fiberglassing the outside hull I waited about two weeks then fiberglassed the inside of the hull. At this point I was fairly satisfied, the job wasn't perfect but I thought it looked pretty good. Today I turned the canoe over again so the outside of the hull was facing upward. I was shocked to see that dark stains had come up on the bottom of the hull. The stains are definitely underneath the epoxy and are not a surface stain . I will attach some pictures If anyone has any idea what would cause this I would appreciate hearing from you. Perhaps some dampness on the wood? I am feeling a little discouraged, it looks like the appearance of the hull is badly damaged

https://i.imgur.com/jLDGFWf.jpg
https://imgur.com/YNWBuIE
https://imgur.com/zXKrF3z

[Cruiser]

It seems very likely that "something" was left on the wood ... you don't give your surface prep process or the epoxy used, but looking at the patterns left, there is little doubt it looks like something was smudged and left on the surface. Residue from a rag or something.

If it really bothers you and the inside is clear, you could always consider a gel coat or exterior paint coat, not what I would personally like, but you are in a "what the hell do I do now" position. There is no fixing that issue now, short of redoing the whole exterior glass/epoxy, which I don't recommend.


Brian

[WJWBoats]

Thanks for the response. I have been thinking back over the process I went through and cant really come up with a source of the stain. I agree though it is most likely left on the hull from when I wetted down the hull, possibly a contaminated rag. It seems weird that it took a couple of weeks for it to appear.
The epoxy I used was West 105 resin and 207 hardener. I sanded the hull with a 120 and 80 grit sandpaper both with a disc sander and by hand. I wetted the hull with water and then I wiped it down with a rag dampened with acetone. When I applied the fiberglass I was pretty diligent about following the process outlined in the Canoecraft book
The idea of painting the hull definitely doesn't appeal nor does the prospect of starting over. I will go ahead and sand the hull and work through the next steps. Perhaps a semi transparent finish of some kind might disguise the stains somewhat and still leave the wood grain visible. I will have to do some research, of course additional suggestions are welcome. Thanks

[Jim Dodd]

It appears to me that something was wiped on the hull, prior to wetting out.

At this point I would either live with it, or paint the hull. Sad to see that happened !

I would not use Acetone on bare wood. You could have loosened the glue with it.

I don't use water either. just blow the dust and wet out !


Jim

[Cruiser]

As Jim has pointed out, using anything on the wood presents a risk. Acetone on a sanded surface brings nothing to the party other than risk .... plain water to raise the grain is about as much as I risk, even then I use caution with any rags.

Remember, what you are seeing isn't likely a "stain" but more likely something left on the wood that the epoxy has reacted with, so if there was a contaminant in that acetone or it leeched something from the rag or there was something on the lid ... you get the idea, it is a possible you wiped on the issue without ever seeing any evidence. Once the acetone evaporated, you might not even get it out with a sanding as it would have penetrated the wood since the acetone would act as a carrier.

Maybe give West a call and see if they have any ideas ... I haven't used their products, but have heard good things about their knowledge and help


Brian

[WJWBoats]

Thanks for your help. It is a little discouraging but I think I will finish the boat and live with the discoloring. The boat will look pretty good when it is in the water. If I do this again I will know better. Thanks again

[Jim Dodd]

I agree with Cruiser, that the Acetone could have reacted with the cloth.

My wife's finger nail polish remover has Acetone in it ! Scary stuff !

I'm sure you will enjoy the canoe just as much !

Jim

[Traveler]

Clear cedar inside and out is good, but a painted hull with clear inside ain’t so bad

https://imgur.com/XIj6WRQ
https://imgur.com/5cXArjh

[sedges]

If you used water on the inside after sanding, as you did on the outside, maybe it seeped through between strips and moistened the outside surface under the glass.

nothing should touch the hull after sanding and before glassing

I think painting the outside is a fine option. There are some pretty topside paint colors out there. Even some real cool duct skiff colors like Dead Grass! You can always do that later if you get tired of the blotchy finish.