OH MAN!! making a mess of my glass!!

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Erik
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OH MAN!! making a mess of my glass!!

Post by Erik »

Well, i did it, sanded right threw the glass :crying . in one spot right behind the end of the bow stem, at the keel line. i am seeing in other spots tiney pin hole sized spots, i am guessing that this is the very begining of the cloth.
So i think i should put another coat of epoxy on!?

should i put a little patch over this spot that i hit wood on? it is small, but in a very high wear area, the spot is about 1/2"x2" or so. i had wondered about a small patch in this spot and then a small skid plate to cover it and add some wear resistance in this spot.

the sanding i have just finished with is an 80grit with a random orbital sander, will all of these tiney scuffs and marks be visible under the final coat of epoxy? meaning do i have to do a finer sanding that is unidirectional?

once i have applied this final coat, when can i remove the hull from the molds and work on sanding the inside? i was thinking i could do this during the full cure for the outside epoxy, then put it back on the molds to sand, then glass the inside.
Tom in MN
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Sanding through glass

Post by Tom in MN »

I may be stating the obvious, but 80 grit paper is a little coarse to be sanding over glass. I never use anything coarser than 120 for sanding over glass. I would patch the areas and feather the edge and maybe you will not be able to see it.
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Erik
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Post by Erik »

i was really thinking that i should just bite the bullet and put another whole coat on.

canoe craft tells you to use 80 grit, and i had a pretty bad job and alot of sanding to do!
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Glen Smith
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Post by Glen Smith »

Erik, Canoecraft states, as I did, to start with 80 grit and switch to 120 grit when most of the gloss is gone. After seeing the photos you sent me, I told you it was time to switch but you apparently did not. You may also have been applying pressure to the sander instead of letting the sander do the job. This may seem to be a quicker way to do the job but it usually spells trouble.

At this point, it is probably best to patch any damaged areas, apply another full coat of epoxy then sand it with 120 grit paper just to remove the gloss.
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Erik
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Post by Erik »

Thanks Glen,

The photos that i sent you were a small test spot that i had done. I continued on the hull with 80 grit with no problems. The problem that i had was at the bow, the problem spot looked similar to the other rough spots, but instead of the cloth being burried with a rough texture on the epoxy, i think in this spot the cloth was not full, but i did not realize this. it looked very much the same as the rest of the rough spots as i sanded it, but instead of ending up with a smooth surface i hit wood.

The other thing that triped me up a bit, was that i had several helpers, each one took to a side of the hull and kind of formed a team. the result was a different application of expoxy on each side. one had far more sags and runs, and infact ended up with a thiner coat of epoxy. the other side was smoother and a better coating. next time i will have one helper, we will work together over the whole hull!!

So in any event, do i need to worry about the surface now, or just epoxy it? do i need to sand with a finer grit, directional with the wood, or will the swirly marks dissapear under the next coat of epoxy?

Thanks so much for your help!
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Erik
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Post by Erik »

Now what about the patch, would it not need 3 coats? would i build up some coats first on that one spot then do a full coat on the whole hull? or will the patch hold enough epoxy with one coat?
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Glen Smith
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Post by Glen Smith »

It appears that too many cooks have spoiled the stew!

If you sanded through the glass at the bow, the glass may have been floating away from the wood. You could apply a patch to this area then sand the whole hull with 120 grit to obtain an even surface. Once this is done, apply one coat of epoxy in an even thickness, allow to harden a few days, then sand with 120 grit to just remove the gloss. Keep the sander moving and do not apply pressure, let the sander do its job.
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Erik
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Post by Erik »

Glen, i will do exactly as you say. only remaining questions are:

-apply patch today - how many coats? one, two?

- let this sit for __ days before sanding with 120 grit

I am worried about the 120 grit sanding, as somone mentioned before, you can sand to deep with any grit, i think i should do this by hand, especially considering the fact that i am getting deep in other spots also. but i guess i am just trying to get out the swirly marks from the sander?
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Glen Smith
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Post by Glen Smith »

First of all, if you are using a R.O.S. for the sanding, you should not have any deep swirl marks unless you have been applying pressure to the sander or your paper is clogged up and the particles are scratching the surface.

To apply a patch, hand sand the area with 120 grit paper and extend sanding to about 1" all around affected area. Cut a patch of fiberglass cloth to fit the sanded area. Apply epoxy to the surface of the affected area, apply patch to the epoxy, add more epoxy, apply a piece of wax paper or clear plastic kitchen wrap (Saran Wrap) over the epoxy. Use a squeegee over the wax paper to smooth the epoxy and remove excess. Remove wax paper once the epoxy has hardened. If the patch is lower than the surrounding area, add more epoxy.

Allow the epoxy to cure for a few days before sanding. You can sand with anything you like but you must know your tools. Hand-sanding can remove too much epoxy if your are over zealous just as power sanding can. You have to know when to stop.
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Erik
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Post by Erik »

Thank you Glen.!!
JimND
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Post by JimND »

Glen has given you sound advice, and I would add a suggestion to consider. Sanding around edges like the keep or concave areas like the bow with a ROS with a stiff OEM pad can be tricky. It is easy to sand too deep, even for experienced sanders. Since this sand-through happened on the keel where the bottom flows into the stem, that might be your problem. I would suggest you may want to hand sand these edgey areas with a light touch.
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hoz
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Post by hoz »

The wax paper idea has been lambasted over on the Wooden Boat forum lately. Seems one fellow noticed wax had telegraphed off the paper onto the epoxy. Anyone who knows epoxy knows wax and resin don't mix. Any resin applied on top of that is likely to fail.

The general consensus is to wipe the area after peeling the wax paper with an acetone rag just to be sure, or stick with plastic or peelply.
someday I'll fly, someday I'll soar
AlanWS
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Post by AlanWS »

Rather than waxed paper, which can leave wax behind, or plastic food wrap, which is so thin that it shreds when you try to peel it off, I found that heavy polyethylene film works well. I put on a patch of glass cloth wet with epoxy, covered it with poly film, and smoothed it out with a roller, pressing hard particularly at the edges to feather them out. When it hardened, the poly peeled right off, leaving a very smooth patch with no weave to fill. Just make sure there are no creases in the poly, or you will have ridges.
Alan
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Erik
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Post by Erik »

I followed Glen's instructions, and i now have a repair which is totally unoticable. The rest of the hull is beauty!! i applied a very very thin coat which filled in all of the low spots and turned out really really nice! thanks to everyone for all the great advice.

Now, how long before i can sand the final coat? i am thinking i will use the random orbital sander with 320 grit for my final sanding. If i cannot touch the last coat for another 5 days, can i take the hull of the molds and begin working on the inside, return the hull to the molds to do the final sanding later?

since i intend to oil rub my gunnels and decks, is there any reason not to varnish the hull at this point rather than waiting to dry fit the decks and gunnels? perhaps the varnish reduces the quality of joint between the hull and gunnels? perhaps i could just mask this area off? if not what procedure do you recomend?

Thanks in advance!
Erik
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hoz
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Post by hoz »

Wait to apply the varnish. Sometimes the amines in epoxy can keep the varnish from curing and you end up with a major mess. A minimum of a week wait time (longer if possible) before varnishing is recommended.

I would also sand the resin only up to 120 not 320. You want some tooth for the varnish to grab on. The varnish coats should be sanded further between coats on up through the numbers.

I got carried away on mune and went all the way to 800, then polished using Meguiars.
someday I'll fly, someday I'll soar
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