Drips and runs and sags in inside epoxy

[Adamv]

Greetings to one and all.

A week ago I glassed the inside of my Bob's Special. When I did the outside, it went exceptionally well, but the inside...well...not so hot. I ended up with lots of little drips and runs. Actually, it is more like th epoxy sagged along horizontal lines (the cloth is up nicely against the wood at least). I think that I let it get a little too cool in the shop to avoid air bubbles. Perhaps the epoxy was too thin.

At any rate, the drips and sags are there now. Any tips for dealing with them? To what extent do I need to level them before sanding? Is there a handy, though readily available tool for scraping them? Any other options?

Adam

[Glen Smith]

You should scrape them as flush to the rest of the epoxy as you can before sanding. You can use an ordinary paint scraper for this but you must reshape the blade first so it has some curvature to it and no corners to dig into the epoxy. You can do this quite simply with a file and then resharpen often.

[Tom in MN]

you are not alone, brother. I think the most difficult part of building a canoe is inside fiberglass layup. If your shop is cool, it is likley the epoxy was too thick to spread thin enough to where it did not sag under its own weight. Use the scraper that Glen recommends with rounded corners and try to scrape off the high spots. Then sand and hopefully everything will appear even and level. I typically do not fill the weave on the inside of the canoe to leave it a little rough. If the finish is dull, it will not show as readily. It is tough to get the runs out completely as you start cutting into the cloth in the adjacent areas if you sand too much. That is why the scraper is the best tool.

good luck, you are over the hump and will be paddling soon.


Tom

[Arctic]

you are not alone, brother.

Aye, Same problem for me- lots of scraping ahead- all part of the process.

Good Luck,
Mark

[Adamv]

You should scrape them as flush to the rest of the epoxy as you can before sanding.

I was afraid you'd say that. Anyway, I went out to good old Canadian Tire today and got myself a paint scraper, which was promptly modified with a curve to match the turn of the bilge on the Bob's Special. After a couple of hours of scraping, a couple beers and a sore arm, I think it's getting there. I've got it pretty good, not perfect, but way better. At least there are no serious peaks from the drips/sags. Things are much more level. I'm hoping the sanding will take care of the rest.

I must say, it was consoling to hear that I am not alone.

Thanks again fellows.

Adam

[AlanWS]

Next time, you can reduce the work by a factor of 10 simply by scraping a bit sooner. One day after glassing, it's easy. A week after glassing, it is much more difficult.

[John Michne]

Adam -

I know that the following will not be of any help after the epoxy cures, but it may be useful for your next boat.

The best way to deal with sags and runs on the inside epoxy coats is to prevent them in the first place. When you apply a coat of epoxy, don’t walk away as soon as you are done. Stay with the job, and periodically go around the whole hull with a squeegee, pulling up runs as they start to develop. You will be doing this about every 10 or 15 minutes at the start, but the frequency and number of runs will decrease as the epoxy sets.

- John

[mbolton]

I have a soft 4 1/2" rubber sanding disc (I found at Home Depot) that chucks up in an electric drill that I used to sand the inside of my boat (except for the ends where I still used my scrapers) and to knock down sags in the epoxy after I had epoxied the inside. I found this to work remarkably well.
Mike

[Peter Kotowych]

Hi Adam,

On Saturday I fired up the heaters and put a second coat on the inside of the hull.
Now I am using 3/4 inch replacement blades for cutters to scrape off the runs. I can't think of the name of the knife, but often they are disposable and you just break off the tip and have a fresh new blade.

I got the idea from Erich Eppert and it works well. Just bend it (being careful not to apply too much pressure and break it) and scrape away with the middle being the contact edge. It is like a cabinet scraper, but you don't have to sharpen it. Just dispose of it and get a new blade. I think I bought 50 blades for $10. As others have stated, it is a lot less effort the day after you apply the epoxy.

Pete

[Adamv]

Thanks to everybody for the words of wisdom and advice.

I've been scraping and sanding (indeed, I should have scraped much sooner. I guess I'll know for next time) and its shaping up. I don't think I'll get it perfect, but that's ok, it'll just match its builder!

I sure am looking forward to getting the varnish on it to bring the shine back.

Thanks again everybody.

[ealger]

Adam, we've all found out that the best learned lessons are those we teach ourselves!

Some areas that you might not view as perfect can be made to look a little better by using a "matt" varnish on the inside of the hull. A matt varnish does several things. It hides epoxy blemishes, reduces the glare from the sun and helps to produce a non-skid surface.
Ed...

[Adamv]

Thanks for that tip Ed. Using a matte finish sounds like a great idea. I particularly like that it will cut down on the glare and make the inside not quite as slippery. Should I worry about two or three coats giving the wood a "cloudy" finish? I know I can use a coat or two of glossy and then put the matte on the final coat, but I only have one quart of high gloss and I suspect that I will need it all for the outside of the hull.

Adam

[ealger]

Adam, I can't speak for all varnishes, as I've been using HMG Matt varnish on the inside of my canoe hulls. I apply a single wet out coat of epoxy on the glass cloth after applying a seal coat of epoxy to the raw cedar. I then apply 3 or 4 coats of HMG Matt and it has always been quite clear without being cloudy.

I let each varnish coat dry and buff with a red Scotch Brite pad in between coats. ( A common green Scotch Brite pad will suffice).
Ed...

[Rick]

Adam,

Should I worry about two or three coats giving the wood a "cloudy" finish?

Dark-toned woods, eg. mahogany, will not look as dark with a matte finish when compared to gloss, while the difference isn't that great with lighter woods like pine.

You can test this by brushing both matte and gloss onto a piece of wood, so that half the area is covered by each and compare. My preference is with the more brilliant color that gloss gives, but matte also looks good.... your call.

[Adamv]

Thanks all for the help.

Mike, thanks for the tip about the rubber sanding disc! To anyone following this post, spend the $10 and save your arms the workout. It gets into the bilge area very well.

Pete, I'd already done the scraping by the time I read your post. However, I've actually used a similar technique with the trapezoidal-shaped blades from my utility knife, scraping in an up and down pattern with the drips. Worked pretty well, but not quite as well as the modified paint scraper.

Ed and Rick, thanks for the assurance that the matte varnish won't give the wood a cloudy look. I'll only be using it on the cedar on the inside of the hull, most of which is pretty light in colour, so, given Rick's comment, I'm not too worried about it. Besides, I'm planning on only using two coats.

Ed, I'll take your advice about the Scotch Brite pad. I've browsed some other posts where you've mentioned this secret weapon. Does the Scotch Brite company give you a commission?

Thanks again everybody!