Staining ribs (specifically, how not to)


Name says it all, people.
Upon getting a project or two off of my form, I've come up with a few dark spots on some of my ribs. I'm using 20 guage galvanized strips on the form itself - theoretically, the only spot where any rust/corrosion should be a problem is where the screws are, and the edges. Of course, the darker spots are showing up nowhere near either of those spots - they live somewhere just below the waterline (probably where the bend of the rib is putting the most pressure on the form - the most severe part of the bend) and it's mostly once I get to ribs 14 or so (counting from rib 1 at the bow or stern). Now, as you know, I'm crazy, so I used red cedar - could this be something in that particular wood (like some kind of resin coming out after the soaking/boiling process?) Or is it just the friction of the metal against a rib as I'm hammering tacks.

Question is of course, what does one recommend to eliminate such stains (which are a pain to sand out, and sometimes don't seem to come completely out). I know varnishing the form has been done (I think) and I believe Mr. Seliga used a huge sheet of plastic. Just wondering if anyone had a cool trick before I put the WHITE cedar ribs that i'm using for this next boat down (yes, yes, I am capable of doing something right - well, sort of right).

Thanks for the patience, and reading through a long post. Happy post-day-of-thanks.
Clear packing tape over the metal bands should prevent it. After it gets chewed up you can remove it.;)

Hi, If you are boiling ribs it is possible that the last few in the tank will be stained as a result of the 'tea' from boiling the first ones. Sounds like your stain is from something else tho? I usually ignore these minor variations.
Without seeing it, my first thought is that it's most likely the resin in the wood coming out. I use a fair amount of red cedar in my musical instrument work and see pitch/resin stains often. In my case I think the heat generated by resawing the blocks into tops softens it up enough to flow. It just disappears as I sand the instrument.

And you're correct about the most severe bend being the spot where the resin is squeezed out. When bending guitar sides the bends at the waist and upper bout are where the most spots show up in any of the woods I use. The curve just helps push it to the surface.

Covering the metal banding won't help with eliminating the pitch stains but it will keep the metal from staining the wood as the other say. The only thing that I have found that helps get rid of the pitch when I'm bending guitar sides is blotting paper between the wood and the stainless steel sheets I use. It absorbs most of the pitch but I wouldn't recommend that for a canoe. It can and often does get "glued" to the wood and be a real PITA to get off. I don't bother with it anymore, sanding is much easier and faster.

Here are a couple photos of raw guitar top with visible pitch spots.


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Packing tape. Genius. This is why I come to you people. Although, yes, it may just be the resin - certainly sounds like it from your description (side note - I'd love to build a hollowbody electric someday, but that's another couple of books to read, and probably some more tools to buy). Some of the spots have been a little larger than the ones you've attached, but yeah... Resin + tea = stains? I'll try the tape and WHITE cedar combination tomorrow afternoon and let you know how it turns out. Thank you again for all of your help and tolerance.
Ok, so I bent the middle 14 ribs this evening (small boiler + only one pair of hands = only a few ribs at a time). I'm trying the "tape on the form" method first, and if that doesn't work, we'll turn to varnish. Turns out white cedar really does bend a lot easier than red. Holy crap. I only broke one, and I think it was a grain thing, not a technique thing. I'm kind of amazed. I LIKE it. I had gotten kind of good at bending red cedar, but this was EASY. More updates to come...
well, the packing tape doesn't work all that well actually. i found that the points of the tacks would pick up little bits of tape and catch them in the curl. and instead of staining on the inside, you get all these tiny bits of tape - albeit clear tape, but bits all the same. its a toss up which is worse.
i just varnish the bands each time i build a new canoe and then every once in a while i scrape it all off and start again. you might be getting worse staining down at the bottom of the band if is has been cut there and not bent underneath the form - the galvanizing is only on the surface so you might be getting extra staining from the cut edge. that would be a place where tape would work as no tacking is likely to happen that low on the form.
hope this helps.
Well... I'll give a full report on the drawbacks I guess since I've already got the bands bent around the tape covered metal bands. No planking yet - ribs are drying into shape. It's also been freezing here, so the motivation to go out and plank is low. And no, the bands wrap under the form - the staining seems to come right at the tightest part of the bend, but we'll see what the tape does. Fingers crossed - do you have to hand pick all the pieces of tape out of there (I suppose so - sanding would probably just melt them to the wood or something)? Andre, you weren't putting me on, were you? I know it says "dumb questions guy" but usually the dumb actions follow the dumb questions.