Bonanza second row side window cracked - How?

On 6/8/2007 2:47:45 PM, "Viperdoc" wrote:

Regardless, the amount of work involved is
pretty extensive, and getting a good seal afterwards can be a challenge.

Wonderful.

Thanks for the heads-up, though.

--
Peter

On Thu, 7 Jun 2007 23:42:37 -0400, "Peter R."
wrote:

Today I spotted two four inch and one six inch vertical cracks in the side
window at the seat directly behind the pilot seat. The cracks are almost
perfectly straight and originate at the top frame more or less in the middle
of the window. The aircraft is a 1973 V35B and I would imagine that this
window is that old.

How does this happen? Old age? Cold to hot? Some other force that decided
that one month since my last aviation maintenance expenditure was too long?

my take on it is that the installation has probably always put extra
stresses in the plastic in that area. as the plastic is exposed to uv
radiation it gradually suffers depolymerisation, ie breaks in parts of
the chains of molecules that make up the plastic.

the plastic moves more with thermal changes than does the aluminium so
with thermal changes such as you experience in climb to altitude there
is some movement and stressing going on in the plastic. the plastic
shrinks faster than the aircraft.

over time the gradual reduction in strength and the stresses due to
temperature change meet each other and you get a crack.

how you treat the crack can add to it's severity.
in plastic the tensile forces pulling the plastic apart (it will never
crack in compression) are actually magnified by the shape of the crack
at the very tip of the crack. once a crack starts the stress buildup
at the tip of the crack will tend to make it propagate across the
sheet of plastic.
the method of halting the crack is to drill a small hole just beyond
the crack. the shape of the tip of the crack is then changed from a
sharp stress riser to a more broad distribution of stresses. if the
plastic in the area has sufficient strength to handle the reduced
stresses in the area then that is the end of the propagation of the
crack. an eighth inch drill is typically used.

in your guess above, deterioration due to age (uv radiation effects)
and Hot to cold leading to tensile forces in the plastic locally
exceeding its strength.

dont feel special. we all need to replace plastic windows
occasionally.

btw how your guy mounts the new window is important to having that
window last beyound the warranty period.

Stealth Pilot
Australia.

Viperdoc wrote:
Having replaced all of the windows recently, you are probably lucky that it
is the side window that opens. Regardless, the amount of work involved is
pretty extensive, and getting a good seal afterwards can be a challenge.

Those two are easy and replacing them will have no effect on the seal.
They are in a metal frame. The back windows would also be similarily
cheap. Copliots side front window would be cheap too unless you've got
one with an openable vent window within it, not many of those around.
The pilots side window, even with the openable window, is not that
expensive.

Yes, the windshield seemed the hardest. However, it did take a lot of
trimming to get it in without stress, along with drilling out a lot of
rivets.

If the other windows are old and scratched, a new one alone might look a
little out of place.

"Newps" wrote in message
. ..


Viperdoc wrote:
Having replaced all of the windows recently, you are probably lucky that
it is the side window that opens. Regardless, the amount of work involved
is pretty extensive, and getting a good seal afterwards can be a
challenge.

Those two are easy and replacing them will have no effect on the seal.
They are in a metal frame. The back windows would also be similarily
cheap. Copliots side front window would be cheap too unless you've got
one with an openable vent window within it, not many of those around. The
pilots side window, even with the openable window, is not that expensive.

On 6/8/2007 6:43:37 PM, "Viperdoc" wrote:

If the other windows are old and scratched, a new one alone might look a
little out of place.

The other windows are not too old looking, nor are they scratched up. The
windshield is probably eight to ten years old, as it is a Beryl D'Shannon
speed sloped windshield replacement (3/8 inch, I believe).

--
Peter

Peter R. wrote:




The other windows are not too old looking, nor are they scratched up. /snip/
Ha! Tell us that again after you install the new one...

Happy Flying!
Scott Skylane
N92054

On 6/8/2007 9:08:47 PM, Scott Skylane wrote:

Ha! Tell us that again after you install the new one...

If it ends up looking like a rose between two thorns you'll be the second to
know.

--
Peter