Adding Kevlar to cockpit floor or seatpan?

After seeing first hand the eggshell strength properties
of glass cockpits when they hit objects, I have been
thinking about how much protection I don't have between
my spine and terra-firma.

I have the astronaut foam, and otherwise it is just
the seatpan and glass. I was chatting with my A+P
about this while we had the seatpan out during my annual.

Has anyone contemplated and/or added kevlar to their
cockpits? Or is this just a nutty idea? I assume
their would be a weight and balance issue, and also
determining if the layup would in fact to any good.
Comments?

I think that the ASW-24 and -28 (maybe the -27 as well) are built with a
kevlar layer in the cockpit. It does not improve strenght, but provides
splinter protection when the cockpit shatters. Fiberglass when broken is
extremely sharp, so the kevlar makes the shell stay together and not
splinter.
I may be wrong, so anyone with more knowledge feel free to correct me!

Good flights (winters almost over...)
Jose M.

"Stewart Kissel" escribió en el
mensaje ...
After seeing first hand the eggshell strength properties
of glass cockpits when they hit objects, I have been
thinking about how much protection I don't have between
my spine and terra-firma.

I have the astronaut foam, and otherwise it is just
the seatpan and glass. I was chatting with my A+P
about this while we had the seatpan out during my annual.

Has anyone contemplated and/or added kevlar to their
cockpits? Or is this just a nutty idea? I assume
their would be a weight and balance issue, and also
determining if the layup would in fact to any good.
Comments?

And Schempp-Hirth gliders for many years. Apart fom
Kevlar material issues the modern German cockpits all
have structural features to improving impact performance.

Having had 2 syndicate partner's over the years who
had major cockpit destroying impacts in our all glass-fibre
gliders I think that the safety concerns are very real.

To design, manufacture, prove and get the approvals
for retrospective structural modifications to the cockpit
might be very difficult and would likely cost more
to an individual than changing gliders.

John Galloway



At 09:30 19 January 2005, J.A.M. wrote:
I think that the ASW-24 and -28 (maybe the -27 as well)
are built with a
kevlar layer in the cockpit. It does not improve strenght,
but provides
splinter protection when the cockpit shatters. Fiberglass
when broken is
extremely sharp, so the kevlar makes the shell stay
together and not
splinter.
I may be wrong, so anyone with more knowledge feel
free to correct me!

Good flights (winters almost over...)
Jose M.

'Stewart Kissel' escribió en el
mensaje ...
After seeing first hand the eggshell strength properties
of glass cockpits when they hit objects, I have been
thinking about how much protection I don't have between
my spine and terra-firma.

I have the astronaut foam, and otherwise it is just
the seatpan and glass. I was chatting with my A+P
about this while we had the seatpan out during my
annual.

Has anyone contemplated and/or added kevlar to their
cockpits? Or is this just a nutty idea? I assume
their would be a weight and balance issue, and also
determining if the layup would in fact to any good.
Comments?

Kevlar, or other fibers(Spectra) have been added to cockpits and other
parts of fuselages for many years.
The benefit of Kevlar is that it stretches a long way before it fails.
This can extend the deceleration distance during impact and prevent, or
reduce the secondary impulse that occurs when the structure fails. It
also can serve to contain other broken fragments.
A common structure now incorporates carbon fiber( very strong and stiff
but fails catastrophically) with Kevlar or other material of similar
characteristics which fail at longer extension to provide a stiff,
strong and progressively failing structure.
I think it is safe to say we can thank Gerhard Waibel for leading this
innovation. Others now incorporate these improvements.
As to "home improvement", that would obviously depend on the weak
points of the subject glider and experience and capability of the
person working on it.
Long answer with no firm conclusion.
UH
J=2EA.M. wrote:
I think that the ASW-24 and -28 (maybe the -27 as well) are built
with a
kevlar layer in the cockpit. It does not improve strenght, but
provides
splinter protection when the cockpit shatters. Fiberglass when broken
is
extremely sharp, so the kevlar makes the shell stay together and not
splinter.
I may be wrong, so anyone with more knowledge feel free to correct
me!

Good flights (winters almost over...)
Jose M.

"Stewart Kissel"
escribi=F3 en el
mensaje ...
After seeing first hand the eggshell strength properties
of glass cockpits when they hit objects, I have been
thinking about how much protection I don't have between
my spine and terra-firma.

I have the astronaut foam, and otherwise it is just
the seatpan and glass. I was chatting with my A+P
about this while we had the seatpan out during my annual.

Has anyone contemplated and/or added kevlar to their
cockpits? Or is this just a nutty idea? I assume
their would be a weight and balance issue, and also
determining if the layup would in fact to any good.
Comments?

John is correct in his points. To add just a bit of detail to the
current contruction technique that I'm aware of. In the cockpit, SH
uses a weave that looks to be about 50/50 carbon fiber woven with
Kevlar. The plan is that the carbon fibre gives very high strength and
the Kevlar gives good toughness so that if the strength of the carbon is
exceeded that the kevlar will hold things together. I'd be guessing,
since I haven't actually seen it, but I wouldn't be surprised if all the
major manufacturers were using this same materal in the cockpit areas.

John Galloway wrote:
And Schempp-Hirth gliders for many years. Apart fom
Kevlar material issues the modern German cockpits all
have structural features to improving impact performance.

Having had 2 syndicate partner's over the years who
had major cockpit destroying impacts in our all glass-fibre
gliders I think that the safety concerns are very real.

To design, manufacture, prove and get the approvals
for retrospective structural modifications to the cockpit
might be very difficult and would likely cost more
to an individual than changing gliders.

John Galloway



At 09:30 19 January 2005, J.A.M. wrote:

I think that the ASW-24 and -28 (maybe the -27 as well)
are built with a
kevlar layer in the cockpit. It does not improve strenght,
but provides
splinter protection when the cockpit shatters. Fiberglass
when broken is
extremely sharp, so the kevlar makes the shell stay
together and not
splinter.
I may be wrong, so anyone with more knowledge feel
free to correct me!

Good flights (winters almost over...)
Jose M.

'Stewart Kissel' escribió en el
mensaje ...

After seeing first hand the eggshell strength properties
of glass cockpits when they hit objects, I have been
thinking about how much protection I don't have between
my spine and terra-firma.

I have the astronaut foam, and otherwise it is just
the seatpan and glass. I was chatting with my A+P
about this while we had the seatpan out during my
annual.

Has anyone contemplated and/or added kevlar to their
cockpits? Or is this just a nutty idea? I assume
their would be a weight and balance issue, and also
determining if the layup would in fact to any good.
Comments?

carb.com has some visual samples of a carbon/kevlar hybrid cloth. The
kevlar part can be yellow, blue or red and looks quite appealing. I
plan on using as the inside ply one layer of this material when I build
my HP-24.

Cheers,
Brad

So if one layer of that was glassed on to the floor...would
it perform as well as an inside ply? Or does it gain
strength inside the sandwich...ie plywood?




At 17:01 19 January 2005, Brad wrote:
carb.com has some visual samples of a carbon/kevlar
hybrid cloth. The
kevlar part can be yellow, blue or red and looks quite
appealing. I
plan on using as the inside ply one layer of this material
when I build
my HP-24.

Cheers,
Brad

this is avialable on HpH 304C/CZ gliders already
tim

"Stewart Kissel" wrote in
message ...
After seeing first hand the eggshell strength properties
of glass cockpits when they hit objects, I have been
thinking about how much protection I don't have between
my spine and terra-firma.

I have the astronaut foam, and otherwise it is just
the seatpan and glass. I was chatting with my A+P
about this while we had the seatpan out during my annual.

Has anyone contemplated and/or added kevlar to their
cockpits? Or is this just a nutty idea? I assume
their would be a weight and balance issue, and also
determining if the layup would in fact to any good.
Comments?

This seems to be at odds with a recent edict by the
BGA who have banned the use of carbon fibre and kevlar
instrument panels because of the danger when they break.
Both materials break with sharp jagged edges they say.


At 09:30 19 January 2005, J.A.M. wrote:
I think that the ASW-24 and -28 (maybe the -27 as well)
are built with a
kevlar layer in the cockpit. It does not improve strenght,
but provides
splinter protection when the cockpit shatters. Fiberglass
when broken is
extremely sharp, so the kevlar makes the shell stay
together and not
splinter.
I may be wrong, so anyone with more knowledge feel
free to correct me!

Good flights (winters almost over...)
Jose M.

'Stewart Kissel' escribió en el
mensaje ...
After seeing first hand the eggshell strength properties
of glass cockpits when they hit objects, I have been
thinking about how much protection I don't have between
my spine and terra-firma.

I have the astronaut foam, and otherwise it is just
the seatpan and glass. I was chatting with my A+P
about this while we had the seatpan out during my
annual.

Has anyone contemplated and/or added kevlar to their
cockpits? Or is this just a nutty idea? I assume
their would be a weight and balance issue, and also
determining if the layup would in fact to any good.
Comments?

Earlier, Stewart Kissel wrote:

So if one layer of that was glassed on to the floor...would
it perform as well as an inside ply? Or does it gain
strength inside the sandwich...ie plywood?

Dunno how relevant this is, but in no particular order:

Kevlar can be nasty stuff to work with. The fibers are very tough, and
you need special scissors to cut it effectively. It's not so bad to lay
up and laminate. But once it's laminated and cured, it is troublesome
to drill or sand - what you get is a fuzzy hole or a fuzzy edge. And
then you have to deal with that fuzz. If you just throw resin at it,
it's easy to end up with tough little Kevlar-cored resin spikes that
stick out and poke you.

I'd guess that one layer of Kevlar inside a cockpit tub won't do you
much good in terms of raw impact protection. However, I think it will
help keep all the rest of the bits of the cockpit stuck together, and
that can help in a crash. It also might hurt. Crash sequences are very
hard to predict, so beyond general guidelines it's pretty much a roll
of the dice. But of course, kudos to Gerhard Waibel for his work in
evaluating and implementing meaningful crashworthiness improvements
backed up by actual test results.

If you do consider adding a layer of Kevlar, I'd suggest you add a
layer of glass on top of it to encapsulate it.

Also, consider carefully the weight you're adding, and that it would be
very difficult to remove. You're probably looking at about 2 square
yards of coverage; with 5 oz kevlar and 8 oz glass and then doubling
the fiber weight to account for the resin you're looking at the
ballpark of 3 lbs. That might not sound like a lot, but you'll
definitely be thinking of it on your next carry-out retrieve.

One more thing, in my experience stuff like this tends to look easier
than it is. Add two layers of stuff to an established concavity? No
problem - right? That is, until you consider that the surface has all
sorts of detail contours you'd have to work around. There are mounting
provisions for the seat and seat pan and control stick, there are
rudder cable tunnels and fixtures, the list goes on. I mean, it's
doable, but it can get to be a lot harder than you might expect.
Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com