Corky, Richard and Harry,

Corky was pretty close to having the method down that we used. I have heard of
those who have used polybrush for the bonding of the 2 layers. We don't. The
example of the tri pacer mentioned is interesting in that if the airplane is
still in standard catagory, the recoverer must have gotten a special field
approval for using the method. We have not used it on certified airplanes.
Only experimental. Jim Younkin did use the double cover method on 3
staggerwings he converted from D models to G models a few years ago. He got
the covering included in the long list of field approvals for those 3 airplanes
only. No STC for it. Double cover is not standard on staggerwings from the
factory.

The double covering we have done is based on the techniques used on these 3
airplanes. We made some changes in how the coatings are applied and have had
great luck thus far. I would be more than happy to discuss the way we have
done it with you directly. It is a bit too invloved to fully list here. If
you are wanting a bare minumum finish and gloss or slickness is not important,
don't double cover. If you have a low powered non acro airplane, don't use
this method. This is a method that is not only intended for a slick finish but
is more valuable as a tougher, stiffer, higher durability system for big
engines, big props, and hard acro.

The Staggerwing and pitts model 12 are good examples of airplanes that can
benefit from such a covering system. It is not approved of by Polyfiber nor is
covering wings and not using some form of mechanical fastener like stitches or
screws. There are airplanes out there that simply glue the fabric to the ribs
and have success because of the type of airplane it is ad the design of the
structure. Double covering is not the norm but rather is a special use fix for
a problem of losing tapes in the prop wash on big engine acro airplanes.

The weight difference is always a question. I can only give example from the
airplanes we have done which are pitts model 12s, 4 of them and the
McCullocoupe. We have a standard finish we like to see which is good enough to
place well at flyins. We use urethane top coat colors on all the airplanes we
build. So, if we want the same finish on a model 12, we have to fill the 3.4oz
heavy duty fabric with a few additional coats of polyspray, sand more, and
possibly sand the color to get a satisfactory gloss out of the course fabric.
This is by no menas a bury the tapes finish. The tapes will still be fully
proud above the base fabric. Still, with all that effort, the weave is still
strong through the paint and we have to use 4" tapes on the ribs to keep them
from blowing off the wings.

When we double cover, we end up with no tapes to blow off, 5.1 oz per square
yard of fabric weight, a fine weave fabric to fill that takes far less coatings
to do so and a finished fabric/coatings weight that is within 1 or 2 pounds of
single cover on a model 12.

A model 12 and a staggerwing have ribs that are very close together. When you
use 4" wide tapes over the ribs, you have double covered the wing 70-80% with
just very small strips of base fabric being exposed.

The process is not for the first time cover job. You need to know your way
around the fabric system before trying it. We advise our builders to go the
standard way unless they have experience and are willing to go it alone without
tech support from the covering supplier.

Labor time is about equal to the standard method. Base fabric install is the
same labor either way. Second layer can tape more time than taping would.
But, sanding is faster.

In terms of material cost, you can price 3.4 oz and 1.7 oz fabric for the size
airplane you are covering. Then price tapes. Coatings cost will be basically
the same.

Kevin