Sacrificial layer for gear-up protection.

On Monday, May 18, 2015 at 12:58:45 PM UTC-7, Jonathan St. Cloud wrote:
Also a pilot that does not have the skills to address the emergency at low altitude has the option of just landing gear up. I am of the belief knowledge is good, what you do with it is TOTALLY up to you.

The pilot also has to realize that he doesn't have the skills to handle the situation and ignore the radio call, something that may not be obvious on short final after after a 5+ hour flight, possibly while suffering from dehydration, mild hypoxia, hunger, and/or needing to pee. I'm always surprised at the number of pilots in these threads that have apparently never made a single mistake in their flying careers, I wish I was that perfect...

Back on topic...is there good material to protect the underbelly of a sailplane?
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 getting thin. Something Teflon Based? I see from a previous post, not an easy material to bond to something else.

On Monday, May 18, 2015 at 5:38:43 PM UTC-4, PBA wrote:

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 getting thin. Something Teflon Based? I see from a previous post, not an easy material to bond to something else.

UHMWPE or the material from gap seals (and using GOOD double stick tape for either) makes a good "wear material" for the bottom of the spar box carry through. Something on the order of 0.040" is fine, biggest thing is to NOT go so thick that you remove the clearance between the box & the spar bottom..
Of course, lifting the wing all the way in is free, some sort of protection is worth it.

Charlie,
Thanks for your reply. I have some gap seal tape. I may try that. I do my best to keep the spar up, but the damage has been done over the past 30 years...

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 sailplane?
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 getting 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 from about .005" to .020". Available from McMaster-Carr or Amazon etc.

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 openings, you'll want .005" (or there'bouts, and acrylic adhesive).

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

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

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

Hi Bumper
Please send me two feet of this material to fit the spar s

On Wednesday, May 20, 2015 at 3:01:47 PM UTC-7, wrote:
Hi Bumper
Please send me two feet of this material to fit the spar s

I'll include a couple of feet with your order of a MKIV "high tech" yaw string (it will be folded to fit in an envelope, offer good through 21 May 15 :c).

Or, you can get your very own roll on Amazon ($6.02 w/free shipping w/"Prime") 5 yds, 3/4" wide, .007" thick.

http://www.amazon.com/TapeCase-423-5...ription-iframe