Friday, August 27, 2010

Doping the wing

The wing has been covered with Ceconite and ironed taut. Applying dope until it encapsulates the fibers will relieve the tension on the fibers while locking the fabric together, and making a base the silver and color coats can stick to. There are three different dopes for Ceconite - one green, one blue, and one clear. If you look inside an inspection hole and the fabric looks pink instead, it's probably poly-stits instead. The best way to tell is to check the paperwork; the second-best is to look for the stamp on the fabric showing which STC it's under. Some newer systems can use the polyfiber or ceconite fabric for their base, so even the stamp's not a sure thing.



When sufficient dope has been applied, the cloth will turn translucent like a wet t-shirt. Do not apply too much, or you'll get a run on the inside of the fabric, that'll show all the way through the top coat of paint - no way to hide it.



The shininess shows that the dope is still laying on top of the fabric - unlike cotton, polyester will not absorb liquid, so the dope must be brushed til it penetrates the fabric. When you start to feel a resistance to the brush, you're done either way, as the dope has dried too much to really work further.




The more opaque look here shows the dope has penetrated the fibers and encapsulated them.



While waiting for the last of the dope to dry, my IA showed me how to make the cloth patches that secure inspection rings - and yes, that is a coffee can lid. It's the perfect size!



Placing powerful lights under the wing shows the shadow of the ribs like bones in an Xray, making it much, much easier to put the rib reinforcing tape directly on top of the rib, despite the cloth in the way. We had to do it rather quickly, though, so the lights wouldn't heat the underside of the wing.



Spent the rest of today laying out the holes for ribstitching, and poking them in with a needle.



The spacing in the propwash must be no more than 2.5 inches, and 3.5 inches apart outside of the propwash. However, they must be only 1.5 inches apart at the leading and trailing edge, and even though the aileron cove stops far short of the main wing's trailing edge, I still want all the stitches to line up so it looks neat. Neither top nor bottom are flat, and are both different curves - so the bottom is 1 inch shorter than the top at the main ribs, and the aileron cove is also shorter on the bottom than on the top. All holes are to be directly above each other anyway. Confused yet? Fractions and math are involved for optimal layout, as well as a measuring tape, a pencil, string and some tape or clothespins to secure it to be sure it looks right when all the math is done.

By the end of the day, my head hurt, I desperately need to catch up on sleep, and I got the entire wing ready for rib stitching tomorrow.

2 comments:

Old NFO said...

And you were higher than a kite after smelling dope all day... :-) Looking GOOD Wing!

Old NFO said...
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