Windshield sealant

I need to seal my plexiglass windshield in a few spots and happen to have
some GE Silcone II sealant on hand. It is spec'd as low odor but releases
methanol and ammonia as it cures. I have seen warnings against using
regular silicone sealant since the acetic acid it releases can corrode
aluminum, but I believe ammonia has a high pH (is basic instead of acidic.)
Does anyone know if Silcone II is 'safe and effective' as a windshield
sealant?

"Mike Noel" wrote:
It is spec'd as low odor but releases
methanol and ammonia as it cures.

Isn't Windex a no-no for use on plexiglass because it contains
ammonia?
--
Dan
C172RG at BFM

Mike,
Ammonia is a definite no for acrylic lenses, so I would avoid it on the
windshield also. Ask your A&E or check with the aircraft manufacturer for
suggested sealants.
Don
"Mike Noel" wrote in message
...
I need to seal my plexiglass windshield in a few spots and happen to have
some GE Silcone II sealant on hand. It is spec'd as low odor but releases
methanol and ammonia as it cures. I have seen warnings against using
regular silicone sealant since the acetic acid it releases can corrode
aluminum, but I believe ammonia has a high pH (is basic instead of
acidic.)
Does anyone know if Silcone II is 'safe and effective' as a windshield
sealant?

"Mike Noel" wrote in message ...
I need to seal my plexiglass windshield in a few spots and happen to have
some GE Silcone II sealant on hand. It is spec'd as low odor but releases
methanol and ammonia as it cures. I have seen warnings against using
regular silicone sealant since the acetic acid it releases can corrode
aluminum, but I believe ammonia has a high pH (is basic instead of acidic.)
Does anyone know if Silcone II is 'safe and effective' as a windshield
sealant?

Piper uses a Bostik urethane sealant, can't remember the Bostik p/n,
sorry.

You can order it by p/n from Piper also, the quickest place for a
Piper guy to find the proper p/n is to look up the s.b. on the rear
spar carry-through brackets (the sealant used around the new bracket
is the same sealant used on the windows), or they might find it in the
maintenance manual.

Not sure what Cessna recommends.

TC

"the barkers" wrote in
news:Z2Ddb.610687$Ho3.119000@sccrnsc03:

Ammonia is a definite no for acrylic lenses, so I would avoid it on
the windshield also. Ask your A&E or check with the aircraft
manufacturer for suggested sealants.

Ammonia will definitely craze plexiglass over time. However, this is a
minor surface imperfection. It's not going to significantly effect the
structural integrity of the windshield. Remember, we aren't talking about
"cleaning the windshield" with this stuff - just sealing the part that he
can't see through anyway.

Two gotcha's though:

1. Since the windshield is an A&P issue (unlike the side windows) if you
need to pull it to reseal it well then the A&P may be limited to what he
CAN use (mfr. recomendations).

2. Anytime you use Silicone based stuff on your plane, you should mention
it to the person who repaints your airplane in the future. It's real hard
to get the airframe completely free of it, and it can cause "fisheye" near
where it has been used. There is a simple additive they use in the paint
to prevent problems, but they need to know about it.

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

"James M. Knox" wrote in message ...

1. Since the windshield is an A&P issue (unlike the side windows) if you
need to pull it to reseal it well then the A&P may be limited to what he
CAN use (mfr. recomendations).

And when it comes right down to it, just because it's an A&P job versus an owner
PM job, doesn't affect the procedures or materials choice. If Elmer's ain't any good
for an A&P, it's no good for the owner-pilot.

"Ron Natalie" wrote in
m:

And when it comes right down to it, just because it's an A&P job
versus an owner PM job, doesn't affect the procedures or materials
choice. If Elmer's ain't any good for an A&P, it's no good for the
owner-pilot.

Quite correct. My comment was more that the A&P might be constrained by
mfr service information to use some particular sealant that was specified
when the aircraft was built (possibly 40 years ago). It may no longer be
the best choice, but it's still the one specified. By no means was I
advocating using one of LESS quality/capability.

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

"James M. Knox" wrote in message ...
"Ron Natalie" wrote in
m:

And when it comes right down to it, just because it's an A&P job
versus an owner PM job, doesn't affect the procedures or materials
choice. If Elmer's ain't any good for an A&P, it's no good for the
owner-pilot.

Quite correct. My comment was more that the A&P might be constrained by
mfr service information to use some particular sealant that was specified
when the aircraft was built (possibly 40 years ago). It may no longer be
the best choice, but it's still the one specified. By no means was I
advocating using one of LESS quality/capability.

And why do you think it's any more or less legal for the owner-pilot to do so.
If it isn't permitted, it isn't permitted. Your A&P may be more conservative
than you are, but the practices are supposed to be the same.

"Ron Natalie" wrote in
m:

And why do you think it's any more or less legal for the owner-pilot
to do so. If it isn't permitted, it isn't permitted. Your A&P may be
more conservative than you are, but the practices are supposed to be
the same.

That's an interesting question. Are they? [And I'm serious here... I
am not sure what the legal nit-pick answer is.]

For some things, it is clearly true. But as an owner/pilot under part
43.13 you are only constrained to "approved practices and procedures."
That is, I can't refill my oil sump with the latest miracle oil I
ordered from that SPAM I found in my in-box last week. And if I make my
own oil hose, I have to use the methods and techniques spelled out.

But what if I am repairing "decorative trim." I'm free to go down to
Home Depot and hunt through their rack of glues and fillers (all behind
a set of iron bars that would make Alcatraz proud).

Now in this case we are talking about sealing a water leak around the
windshield. Whether bright or not, I think you will agree that the
owner/pilot is legal to squirt most any little tube of stuff down into
the crack that he/she want to try. [Not talking about actually pulling
and resealing the whole thing - that clearly requires an A&P
regardless.]

The question is, can the A&P likewise go down to Home Depot to get his
tubes of sealant? Or is the A&P constrained to use the manufacturer's
instructions on the "proper" method to seal/reseal the windshield? I
know, for example, that the Piper manual calls out a particular sealant.
Does he have to use that (or approved equivalent)?

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

"James M. Knox" wrote in message ...

The question is, can the A&P likewise go down to Home Depot to get his
tubes of sealant? Or is the A&P constrained to use the manufacturer's
instructions on the "proper" method to seal/reseal the windshield? I
know, for example, that the Piper manual calls out a particular sealant.
Does he have to use that (or approved equivalent)?

If using other than the recommended sealant is not an approved repair for
the mechanic, it's not any more legal for you to do it. So both you and the
A&P have to ask yourself, is this an acceptable method? Not all manufacturers
bulletins are law (for the non-commercial operator).