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Dope, FineLine Tape, and Sharpie markers...

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Ivan

Active Member
Joined
Dec 8, 2003
Messages
38
Location
Manitoba, Canada
So, this isn't strictly homebuilding, but fabric and dope is same everywhere, and everyone likes a story, don't they?

To start, my dad's recovering his plane (Stinson 108-3), and I'm lending a hand whenever work and family allow. Last night, I was laying out and masking the registration on the wing. Never one to leave well enough alone, I thought I could improve on the old standby block letters and laid everything out based on a font I found--modified a little in thickness and spacing to fit nicely into the appropriate regs. Gonna be real classy, thought I.

I had set this all up in CAD, and printed out the full size sheets. To transfer to the wing, I punched holes around the perimeter of all the letters: once at every corner, at intervals around curves, but nothing excessive. Taped the paper to the wing, lined it all up with an inexpensive laser level (handy things to have when you're painting), and marked out the outlines. It took a bit of fiddling to find something that would leave a mark on the underlying dope, and would be visible against maroon. I finally settled on a new Sharpie marker with a nice point on it. It left the smallest of dots, but stayed put and remained visible. Marking off was a snap. <Insert ominous music>

I had picked up a shiny new roll of 3M FineLine masking tape. I've used it before, and nothing else compares. It's a very thin blue vinyl-like film; it follows a fair curve beautifully, it'll lie down flat over a bit of fabric texture (including pinked tape edges, inspection hole rings, and the like), leaves a sharp paint edge like you wouldn't believe, and I've never had it lift anything. (But I'm usually pretty careful) I used the 1/2" tape, and it went around all the curves present in 20" letters. I'll use 1/4" tape on 6" letters, though.

When I marked off the letters, I kept the marks 1/8" inside of where I wanted the edges. That way, I'd just mask 1/8" outside the dots, and all the marker dots would be entirely covered by the white trim paint. All went according to plan, and the masking went even more smoothly than the marking.

Masked off the rest of the wing, double-checked that the registration was correct (wouldn't that be embarrassing!). Time to shoot paint!

One coat of white covered well, and a second light coat would be perfect. But what's this? My little marker dots bled--they're now 1/16" black circles (nicely offset from the edge, of course). Perhaps that's as much as it'll bleed, and another coat will hide them well enough. After all, one coat of white has done a great job of covering maroon so far. So, we let it set as much as we dare, and shoot a second coat.

The letters look great, but the dots are as black as ever.

What We Should Have Done: We should have said, 'This is an absolutely flawless job, other than these dots, which we can worry about and touch-up later' and then pulled the tape.

What We Did: Dad knows from past work that nothing covers stuff like pen marks, dark paint, etc. like silver dope. If we're quick, we might be able to stop the dots with silver and still have time to get some white down. (We were worried about having too thick a layer of paint get too dry, and thus peeling up with the tape--if you're wondering what our hurry was.)

Spray a coat of silver. The dots still bleed some, but they're not too bad, and we can see that there is silver laying over the now-grey dots, so we figure that maybe we've stopped them. Or at least slowed them down enough to be acceptable.

While Dad's putting white back in the gun, I notice something new and disturbing. In all the spots where the third coat went on especially thick, the build-up of crazy solvents is finally taking it's toll on the plastic tape; it's starting to buckle and lift at the edges. Fantastic. However, there's white dope in the gun now, and we figure 'what the heck' and try it on one letter. The dots came back, well, to be optimistic, dark grey.

So we pulled the tape and called it a day.

Actually, in the spots that didn't get a very heavy third coat, the masking did a great job. It's just a little ragged in the solvent-soaked spots. But, all the tape came off without any residue, which I was worried about when I saw it lifting.

What's the new plan, you ask? We're going to let it harden for a couple days, and then I'll rig up some sort of little scraper to dig out the dope and marker ink, and back fill with white dope. Give it a rub with sandpaper to smooth it out, mask it again 1/16" outside the previous edge, and try once more. Unless, of course, anyone has a better idea.

Moral of the story: Don't use Sharpie under dope (and be wary of other felt pens too)! And, if you're going to use FineLine tape, keep the trim down to two (or three light) coats!

I hope this saves someone else some hassle.

Regards
 
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