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...

Most gliders come with a sacrificial layer for protection. It is called rubber and it is on a little round thing tat you lower before landing. Checklists and mindfulness keep this thing as the number one protection against damage while landing! You could also install a steel plate but why, just use the wheel. Now the glide computers, independent micro switches and checklists are all guards against somehow forgetting to put the ship in landing configuration.

One poster wrote that radio warnings to a pilot on final is prohibited, really? If the verbal memonic check and the gear warning system were not working, I would want to know if my gear was up. I can fly and think, if I can safely lower the gear I would and have very low. If someone radioing you that your gear is up causes you to crash, the cause was not the radio transmission rather the pilot's failure to adequately aviate. If we adjust all radio transmissions for the absolutely lowest possible "skill" level, maybe we should require a higher skill level. I know accidents happen, but this is one that is avoidable with two checks before the radio transmission.

I heard of (but did not witness) an account of a pilot who forgot the gear in his glider, touched down several inches lower than recommended and had the presence of mind to pull back on the stick, simultaneously closing the spoilers, floated high enough to lower and lock the undercarriage, redeploy the spoilers and land with a normal rollout and stop. VERY minor damage to the belly of the glider. One can only hope that such presence of mind will occur to me when I (probably inevitably) screw up. Something to keep in mind- if you have some speed, are completely familiar with your aircraft and things are going to hell with grindy noises that will probably cost $300 per second, maybe a last minute save is possible. We have all landed, closed the spoilers and floated again, so a reasoned, planned and perhaps practiced response might give you enough time to get the round rubber thing out. Just a thought. Obviously a last chance scenario that should not replace proper training on landing checklists.

Mindfulness actions keep most accidents from happening. I was flying in the co-pilot seat of a high performance twin and saw the pilot check the gear lights, he had green, but did not bother to count. He need three green not two. He was mindlessly going through a landing checklist. I was mindfully flowing the check list. It is always best to actually include the brain not do by muscle memory alone.

On Saturday, May 16, 2015 at 9:42:47 AM UTC-7, wrote:
So you think having 3 green lamps in every real airplane is not a good idea to prevent landing on it's belly?

And when you deploy spoilers on the beginning of final lets say 300 AGL there is lots of time to put the gear down without geting panict by a "beep"..
But I would also prefer the voice module...

Muscle memory has gotten me in trouble on occasion. Primarily with the actions of opening and consuming bottles of beer in rapid and repeated succession.

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