Sacrificial layer for gear-up protection.

At 01:48 19 May 2015, bumper wrote:
On Monday, May 18, 2015 at 2:38:43 PM UTC-7, PBA wrote:
Back on topic...is there good material to protect the underbelly of a
sa=
ilplane?=20
I would be interested in protecting the base of the wing spar opening
on
=
the fuselage. Years of assemblies have started to wear a groove and it's
ge=
tting thin. Something Teflon Based? I see from a previous post, not an
easy=
material to bond to something else.

The material for that is UHMW PE tape, available in various thicknesses
and=
widths, with either rubber or acrylic adhesive. Common thickness ranges
fr=
om about .005" to .020". Available from McMaster-Carr or Amazon etc.=20

Note that as you approach 10 mills, the tape starts getting more rigid
and
=
is suitable mostly for flatter surfaces. For lining the fuselage spar
openi=
ngs, you'll want .005" (or there'bouts, and acrylic adhesive).

UHMW PE is almost as slick as Teflon, but has much higher mechanical
streng=
th. Teflon, will slippery, is not nearly as wear resistant or useful as
an
=
anti-abrasion liner. For tough jobs, UHMW is best.=20

bumper
I probably have a dozen rolls of UHMW PE in various calibers in my hangar
:=
d)

My friend and I had this problem on our gliders, a DG200 and Std Cirrus
respectively. Measure the depth of the groove. Lay up several sheets/strip
of
glass fibre on a layer of plastic sheet on a workbench. When cured cut to

length, check the strip fits the groove and brings the level of the unworn
part
of the fuselage. Attach in place with resin. When the resin has cured
file/sand
to a smooth finish, less than 10 minutes work each side. Result is a
durable
smooth surface for the spar to slide into the fuselage at the right height

bringing joy back to rigging again. An inspector checked our handy work
and
was most impressed. I may have to repeat again in another 1500
assemblies/43 years!

Gavin
Std Cirrus, G-SCNN, #173
SFV Südeifel, Utscheid, Germany