wrote:

I just found out about a method being used by some experimenters to
cover their wings that is intriguing. They are literally covering the
wings twice with fabric.

The technique involves covering the wing initially with a heavy grade
fabric, taughten it with the iron as specified, apply the rib tape and
then stitch the ribs as normal. Up to this point, everything is
absolutely by the book.

But then, they apply a lightweight second layer of fabric on top of
the original covering using polytack. The second layer becomes a
defacto enormous tape. What I mean is normally, the next step after
stitching is to cover the stitches and leading edges with pinked
tapes. In effect this method is doing that, it's just that the tape
is the width of the entire wing.

This second layer is then ironed with the iron at it's lowest
calibrated setting.

I got to inspect two wings side by side, one with the finished double
covering and the other one with just the single fabric (prior to it
getting the second layer). The difference between the two wings was
incredible. The double layered wing seemed like it was covered with
sheet aluminum compared to the single layered wing. Snap your finger
on the double layered wing and you heard a reasonant "PING". Do the
same to the single layered wing and you hear a dull "thud".

The guy doing the covering said that he understood that this method
for wing covering was a certified process for the Beech Staggerwing.
He's seen several airplanes with the two layers at airshows and they
really impressed him.

Why would anyone want to do this? Well it makes a very stiff fabric,
no bulging up between the ribs. It also eliminates the pinked tapes
applied on top of the stitches and elswhere because the second layer
constitutes those tapes. There is much less sanding required because
you don't have to spray and sand around each of the pinked tapes.
Basically you just spray the proper silver and primer, scuff slightly
and you're ready for the color coat.

Has anyone else heard of this method?

Corky Scott

I saw a Tri Pacer at Kerrville (SWRFI) a few years ago that had been\
double covered. The "look" of the wings is what caught my eye, and I
asked the owner about how it got to be that way.
He used 3.2 oz first, then a layer of 1.7.

You are absolutely right about how fine it looked.

However, except for the show plane finish, I'd be a little skeptical
about the extra weight (filling two layers of fabric!) as well as
strength of the final fabric cover (if the first layer were not finished
out normally).

The first layer of fabric should be properly filled with Poly Brush
(3 coats) before the outter skin goes on. Otherwise, I'd wonder about
how strong that outter layer of thinner fabric would be...

Another concern is about using Poly Tack to attach fabric to fabric.

The Poly Fiber manual specifically recommends NOT to do this because
Poly Tack, when dry, it too hard to stand up to the flexing of the
fabric.

That would mean using Poly Brush to attach the second layer - and how
now do we shrink the second layer???


Richard Lamb