Hello. I am having difficulty hiding the edges of the cloth the join the bulkeads to the tandem kayak I am finishing up. I have read through the forum and applied all feathering techniques. Scraping, sanding with multiple grits, etc. Surprisingly, with every attempt, the visibility of the edge does not change - even though to the touch, it is a perfectly smooth transition. The strips are bias cut. Would love anyone's perspective on why in the world the line continues to show, with zero improvement despite scraping and sanding. Any thoughts on what is happening (or not happening)? Some images attached. Thank you very much.
It may be an optical effect instead of roughness. That is, you may have sanded across the ends of the glass fibers and they’re either acting as light pipes or they’ve become frosted glass tubes diffusing the light.
Try wiping them down with denatured alcohol and see if they get less obvious. If they do, you can stop sanding; the varnish will take care of it.
Laszlo
Thank you, Laszlo. You may be on to something.
I’ve been experimenting with a tiny section, where I literally sanded through the glass and the line is still there. When I run my finger over it, it’s perfectly smooth, as if the line I am seeing is not physically there (hence your "optical” point?). I can’t make sense of it. Originally, I laid up the strip (epoxy coat #1), then 2 fill coats without scraping the edge. I wonder if too many coats before addressing the edge created some sort of imprint on the underlying substrate. It’s baffling.
As for your point on the denatured alcohol, each test I have done (file, scrape, sand, different grits), I continuously do the wipe to gauge effectiveness in the test, and as I get deeper and deeper through the material, the line remains the same (more of less). I think the optical point may be what’s going on - I just don’t know how to get rid of the line. I’ll likely leave it be, since it’s not a super visible part of the kayak. I’m just really interesting in understanding what may be at play in case it repeats down the road.
Curious what you think of another theory I have. Being my first boat, everything is a bit new. When I used the knife to cut the fiberglass after the initial lay up, I wonder if I pushed too hard on the blade (rather than lightly scoring it). Is it possible that the line is actually NOT the line of the tape I laid down, but rather damage done to the glass on the bottom of the inside of the hull. They would be exactly aligned since it was the same knife cut. And if I went too deep, I may have created the slivery appearance of a line to the substrate underneath where I laid the bulkhead tape. I wonder if that is what is going on here…
Eric,
Personally, I would move on. It is inside the hull and nobody is ever really going to notice it except you (especially if you paddle with a sprayskirt) Boats are meant to be paddled not treated as works of art.
David
P.s. I think the line is a result of the knife cut as your last post suggested.
Yeah, knife cut sounds plausible to me, too. And David is right - at some point you have to shoot the boatwrights and go boating,
Laszlo
At least it’s a neat, uniform line. It looks intentional and not at all bad.
Hi Everyone - I really appreciate all of your perspectives!
Trying to fully understand technique here so my external seam taping does not repeat this and for future projects (this is my first).
So from the comments and reading earlier posts on the board, the potential issues are:
Hard knife pressure (blemishing the underlying substrate), cutting technique (cutting through cloth vs. just score and tear), and premature fill coats (that bonded tiny fibers to create “light tubes”). I am understanding this correctly?
I will be doing the external seam tape next, so want to make sure I understand the steps, since that will be highly visible.
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Lay up the fiber glass seam tape, squeegee off excess
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Once tack free (and BEFORE fill coats), score (not cut) the cloth while “tearing” excess away
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Scrape and sand the edges to knock them down (after ~48 hours of curing for ST Clearcoat)
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THEN add 2-3 fill coats before feathering in with rest of the boat
Is this on the right track?
Thanks again for all your help!
Eric