Covering upper wing tank

[Meyertheflyer]

I'm unrolling the fabric to cover the right upper wing, but before I proceed, can someone tell me if I should coat the upper surface of the wing tank with POLYTAC, over the 2 coats of dried polybrush? I searched the forum data base but still am not clear. Thanks

[jtpitkin06]

Poly Tac only around the perimeter of the wing. Specifically the leading edge, the trailing edge and the end ribs. Then shrink the fabric, including the fabric over the tank.

After you shrink the fabric apply your Polybrush to fill the weave. Poly brush is also an adhesive so it will attach the fabric to the tank and ribs as you apply it.

JTP

[Meyertheflyer]

Thank you, I'm glad I asked before proceeding. What a great
Resource the forum can be.

[jiott]

My SS7 manual also said to coat all the rib capstrips (especially the undercambered botom ones) with Polytac (possibly two coats-my manual is out at the hagar) and LET IT DRY. Then apply fabric and shrink. Then soften the dried Polytac on the capstrips with MEK (maybe it was a diluted mixture of Polytac & MEK) thru the fabric to glue it down (use weights on the undercambered ribs). Then do the normal Polybrush applications. No Polytac on the tanks.

Jim

[HighWing]

There has been debate over the years on whether to use the Polyfiber Manual or the Build manual for covering instructions. Polyfiber doesn't accept the early Kitfox no rib lacing necessary advice. Polyfiber also recommends a final shrink at 350°. This temp would wasp waist the aft longerons in the early models and the factory recommended no more than 300° for this reason - lots of debate there. The rib issue is likely because Kitfox used the one inch capstrip where most other airplanes use half inch or so, and aluminum ribs less than that and with much less surface area for adhesion, rib lacing was essential. Also, the Polyfiber's manual was written as a one size fits all to comply with FAA standards in certified aircraft.

Both of my airplanes had the fabric glued to the rib cap strips as instructed in the build manual. This is probably not necessary with rib lacing, but we have all heard of the belt and suspenders guys - that's me. Both were also rib laced.

[N981MS]

Aaaah, the memories that picture brings back. Nothing like the smell of MEK in the morning.

I coated the top of the tank with polybrush and let dry. Later, when the polybrush is brushed onto the overlying fabric it "reactivated" the dried coat on the tank and really adhered the fabric well. I seem to remember someone commenting that it would be hard not to have a lumpy surface if you used poytak over the top of the tank. I don't remember who to give credit to for this but it has worked well so far.

[Meyertheflyer]

Thanks for the posts! I followed your advice and will brush on the first coat of poly brush. Another skill to enjoy.

[Jfquebec]

Great job....and your final shrink is at....300 or 350...

[Meyertheflyer]

Actually ended up about 310 degrees and it feels very taught without any warp age. I did put 3/8 inch aluminum stiffeners in the trailing edges. Finished first coal of poly-brush today.

[Dorsal]

Looking good!