PDA

View Full Version : Playing with fire?



DanB
09-21-2008, 06:32 AM
Yesterday I was working along on a wing laying down the rib tapes and I noticed the edges of the pinked tapes actually curling up as I tried smoothing them down with Poly Brush. I was quite surprised at this phenomenon as I had not encountered it before (tail feathers and fuse are covered and taped).

I had followed the book laying down my first coat of Poly Brush, letting it dry then laying in a bed for the tapes. After letting that dry, one more wet bed, place the tape and brush it down, smoothing it out. I did make sure that the tape "curl" (the way it comes off the roll) was on the down side.

As I was going down the wing I tried a few things to see if I could save myself from becoming an ironing god (meaning an iron at 225 should secure these curls after they dry). Wet the tape first & lay it down...no good (& too messy), lay the tape and soak through the top without a wet bed...nada, I even tried peeling the tape up after I got it brushed in, turned it over and brushed it in again (which actually worked the best of all my trials but was too much a pain in the keester). I was half way down the wing when I resigned myself to knowing I will be spending time with the iron. Then I saw it...There was a little piece of lint on the wing and I tried to blow it off. It moved just a bit, but returned to it's point of origin. That's it! I'm battling an invisible foe called static electricity! So there I was, I identified the problem but didn't know how to slay the dragon. I thought of an anti-static spray product my wife uses sometimes, but didn't want to take a chance there might be something in it that could react with the Poly products. I did a search in the Matronics list and found a reference to using a 50/50 mix of rubbing alcohol and distilled water in a spray gun. That sounded good but wasn't sure if the rubbing alcohol was ok. Will wetting the floor resolve this issue?

So, here is a plea to those of you who have been down this road...What works?
Respectfully yours, Sparky

RandyL
09-22-2008, 10:51 AM
Dan,

You obviously know what you're doing having completed your emp and fuse -- the technique you are describing is exactly what I learned in covering class last weekend. They did cover (no pun intended) ironing the edges of pinked tape that didn't lay down properly and said you had to be real careful because the edge will curve if you iron unevenly. Just a suggestion, would a brisk but consistent pass with the iron down just the edge get it to lay down yet be fairly expeditious so as to not take hours?

Sorry I can't be more help!

RandyL
09-22-2008, 04:21 PM
Dan, I just got a tip from John McBean... he says ground the wing. Doh, we all should've thought of that. He says he always does that when he's wiping fabric down with pre-paint cleaning solvent or MEK because the friction on the polyester generates lots of static.

Hope that helps, seems like it would!

jdmcbean
09-22-2008, 04:23 PM
Hey Sparky !! I know why you referred to yourself as Sparky.

Try grounding the wing spar.. You will also find this useful when cleaning the wings prior to painting.

Short story... years ago 1937 there was a fire in the original Bradford Factory (later Piper Aircraft) They suspect that the fire was caused by your friend "static electricity" It was discovered that while cleaning the wings with solvent (today we would use C2210) the fumes will accumulate quickly on the inside of the covered wing... while wiping with a rag static electricity built and discharge igniting the fumes.

While covering our wings I found that grounding the spar and keeping our hand on the spar while wiping helped.

DanB
09-22-2008, 06:59 PM
Thanks for the reply's John & Randy. You are right Randy, I should have thunk of grounding the thing. I actually remember reading of a guy that not only grounded the part he was working on but went as far as wetting the ground and placing a ground strap in his sock that trailed in the water. I don't think that is really necessary, but I see the logic in it.
I will try grounding the spar John, thanks again.
Sparky out

mickey
09-26-2008, 11:59 AM
Same concept as building a new computer, but on a larger scale. You might even consider one of those anti-static wrist straps the computer builders use, and attach a longer wire to it. Then ground yourself to the spar, and the spar to.....ground. (A copper water pipe?) Then you can still work with both hands more or less free.

RandyL
09-26-2008, 12:15 PM
I was just thinking about this the other night as I was falling asleep... where to ground it? I came up with the idea of finding a screw that is the right size to fit into the ground hole of a wall outlet, then solder a 20' piece of wire to it with an aligator clip on the other end for the wing spar. Should work. Indeed, same idea as a computer tech's ground strap.

DanB
09-26-2008, 04:50 PM
Randy
Funny how we solve things when we are trying to make our brains go to sleep...I was just driving home today from work (no, I wasn't sleeping then) thinking about where to do my ground and I like your outlet idea. I was having thoughts about driving a rod in the ground just outside of the garage (Mickey's mention of the water pipe was my first choice but on the other side of the house). The alligator clip is the way to go for the spar end and I was thinking about using a #6 ring terminal for the end that attaches to the outlet screw. Stranded wire probably the best choice.
Thanks again for the assist...I love it when a plan/plane comes together.

John and Randy,
The spar grounding worked great. I ended up using 18 ga stranded wire and grounded it to the screw on an outlet. It was funny because I had some tapes cut and laid out down the wing and within a minute after grounding, half of them slid off onto the floor. Like you said John, it will sure come in handy when I prep the wing with cleaner getting ready to paint.
Thanks again!