Sanding question

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Riverrat
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Sanding question

Post by Riverrat »

The fiberglassing went a lot better than expected. I put the wet out coat on and the second coat according to Ted's instruction in the book. I had to go out of town for a day, so sanding is required before the final caot since its been about 36 hours since the second coat. I started to sand this morning and I'm finding that I may not have put enough epoxy on in the second coat. I am seeing millions of little white dots,(sanding dust collecting in the weave). I haven't gone thru the weave to the wood and have only done about a 1 foot square before I stopped to ask; is this normal? Will these "white dots" come out? Do I need to sand more? Stop sanding and add more epoxy? I'm just lightly sanding with my ROS and 120 grit open coat.
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mtpocket
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Post by mtpocket »

Riverrat,

Can you suspend the ROS sanding for the moment and use a scotchbrite pad instead? It would be less intrusive in the epoxy but should give your next coat of epoxy some bite. The dots you mention sound like the high points of the fiberglass weave.
Riverrat
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Location: South Alabama

Post by Riverrat »

Can do. But, will the scotchbrite help to flatten out some of the runs also?
edit..I wiped the spot dowm with a damp rag and the "spots" went away. When it dried, they were back, but with the accumulation of dust gone, it's evident that you are correct, they are high spots in the weave. The areas around or in between the dots are glossy still.
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mtpocket
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Post by mtpocket »

I doubt if it will help much in that department. You can use a ProPrep scraper or maybe a paint scraper to remove the runs first. The runs will be thicker than the rest of the epoxy so you shouldn't have any trouble with hitting the weave while scraping. If you don't have a scraper you are comfortable with, use a hand sanding block and remove just the runs.

Good luck
Riverrat
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Post by Riverrat »

Thanks empty..I'll see how it works.
Professionals built the Titanic; amatuers built the Ark!
Riverrat
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Location: South Alabama

Post by Riverrat »

Scraped the runs off with no problem. The scotchbrite pad worked but did the same as the 120 grit paper...left white "dots". I must have been really stingy with the epoxy as it didn't go on thick at all. I used a squeege and tried not to leave any on the hull as Ted suggested. Guess I did to well at that huh?.. Anyway, have vacuumed the hull and wiped it down with warm water and dried it off. Now I'll wait a couple of hours to make sure its dry and add the last coat of epoxy. I hope it looks as good after the epoxy as it did when I wiped it down with the wet cloth. Of course, after it dried, the white spots returned. Perhaps they won't under the epoxy resin. Thanks agian for the help. Wish I could send a picture but my son borrowed my camera some months back and hasn't returned it yet.
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mtpocket
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Post by mtpocket »

The white dots might be nothing more than the little dimples of epoxy that pushed up during application. The epoxy turns a white color when sanded just like the glass does. You could get lucky and not even have a problem. I hope this is the case.
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Bassbug
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Post by Bassbug »

My experience, although limited, is that the white spots will stay. I assumed they were epoxy "dust" forced into holes in the epoxy layer. I was thinking that the weave was not fully covrered in epoxy before I sanded this area. I got the white spots when I layed a fiberglass layer, at the waterline, and I was trying to smooth the edge of this layer.

Additionally, I like to know how other builders smooth the extra fiberglass layer's "edge", either a full waterline protective piece or a stem layer.
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Patricks Dad
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Post by Patricks Dad »

Additionally, I like to know how other builders smooth the extra fiberglass layer's "edge", either a full waterline protective piece or a stem layer.
I'm no expert on this but we put an extra layer of bias-cut glass on our bow stem. The strip was 3-4" wide. We laid 4 coats (wetout + 3) of epoxy on the glass with each layer about an inch wider than the prior coat. This allowed for a gradual taper of the epoxy layers over the glass when we sanded. It seemed to work out pretty well.
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KARKAUAI
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Post by KARKAUAI »

For what it's worth, I used only two fill coats on my second canoe, in an effort to save weight. I found that I had a lot more spots where I could see the weave after sanding, but only a couple that didn't disappear when the hull was wet. I kinda feel like I've been on the ragged edge of getting into the glass itself, but when the finish was put on, all but the few spots that didn't disappear when wet were gone. If you can see these spots when the hull's been wiped with a damp rag, you'll be able to see them when the finish is put on. More epoxy won't get rid of them, either. Wet down your hull and if you can live with what you see, forget the spots. If you can't live with them, I'm afraid you're going to have to remove and reglass. I had one spot where I had to sand out an area that didn't wet out well, and the patched place came out pretty good. You REALLY have to be careful when removing the glass to not go through into unepoxied wood, though. That leaves some blotchy areas, but they're really not that noticeable of you aren't looking for them. From now on, I'm going to make sure I have more than enough fill coats to keep me from getting into the glass itself when sanding, even if it costs me a pound or two.
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Bassbug
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Post by Bassbug »

PD,

Is this correct?...you did not sand the edge of the stem glass once you wet it out...you just covered it with additional coats of epoxy, each a bit larger in size, then you sanded out the epoxy for a nice tapered edge.
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Patricks Dad
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Post by Patricks Dad »

right. no sanding until all. coats of epoxy were applied. Was that right? Did I miss something?
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Bassbug
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Post by Bassbug »

No you didn't miss anything. On the kayak I'm buildiing, I carefully sanded the edge of the protective glass after one fill coat, thinking it would blend better in the end. I've not epoxied everything before I sanding extra cloth....thus I was clarifying the process for myself.
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