64 M20c Avionics Cover Sealing?

[BellSouth.net News]

We are working on a 64 M20C Mark21, it does not have the "forward windshield
speed mod", still the factory design. There are two panels in front of the
windshield on the outside that cover the avionics assembly inside. They
have been sealed with silicone so many times that it took us 4 hours to
clean them up. I don't want to use silicone again. I'd prefer to use some
sort of pliable, removable sealant.

What is the preferred method for sealing those two panels (actually, there
are three as there is a small narrow one that covers the other two)? And
what do you use to seal the screws?

Any help would be appreciated?

Thanks in advance,
Alan - please remove the obvious email address extension to reply via email.

[Al Marzo]

On Sun, 22 Aug 2004 18:56:28 -0400, "BellSouth.net News"
> wrote:

>We are working on a 64 M20C Mark21, it does not have the "forward windshield
>speed mod", still the factory design. There are two panels in front of the
>windshield on the outside that cover the avionics assembly inside. They
>have been sealed with silicone so many times that it took us 4 hours to
>clean them up. I don't want to use silicone again. I'd prefer to use some
>sort of pliable, removable sealant.
>
>What is the preferred method for sealing those two panels (actually, there
>are three as there is a small narrow one that covers the other two)? And
>what do you use to seal the screws?
>
>Any help would be appreciated?
>
>Thanks in advance,
>Alan - please remove the obvious email address extension to reply via email.
>
Not sure, but if you check the parts book, it may show an official
gasket. Now I've seen RTV (silicone) used a bunch. I've also seen a
dum-dum type of compound, probably just 3M body sealant. The silicone
may be there for a reason known only to the previous owner!!!

[[email protected]]

On Sun, 22 Aug 2004 18:56:28 -0400, "BellSouth.net News"
> wrote:

Really depends what type of seal you are looking for/how much time &
effort you wanna put into it.

If you wanna do the "ultimate" fix I have had excellent results
bedding avionics access panels on all types of aircraft using PR1422B2
(or any AMS-S-8802/Mil-S-8802F, Type II equivalent) sealant as a
permanent fix.

If you get the sealant in SEMkits, it's easy to mix and easy to apply
with a slightly modified caulking gun. I would think your local Mooney
man would have access to the sealant and a gun though, it's commonly
used for wet-wing repairs.

You remove all traces of whatever sealant was present, and wipe it
down with either MEK (be careful on the paint and your liver) or
anhydrous isopropyl alcohol (everybody oughta have a gallon, get it a
larger pharmacies/medical supply stores).

Play around with some plain aircraft washers between the panel and the
fuselage, until you come up with a combination that puts the panel
flush with the fuselage. Mask around the fuselage opening, and around
the outside of the panel.

Lay some plastic sheeting (garbage bag or whatever) over the
components "inside" the openings to protect it from oozage.

Put either about three coats or pure carnauba wax, or a couple coats
of fiberglass release agent (paste type) on the "inside" of the
panels, wiping off in between coats.

Mix up the sealant and apply it in a uniform layer around the opening.
Using the aforementioned washers on every 4th or 5th screw, install
the panel, just snugging the screws. Carefully wipe off what oozes
out. Pull all the masking before the sealant dries.

Let the sealant dry overnight, remove the screws, and carefully remove
the panels. It will slightly difficult to get the first corner pulled
loose, but the panel will pull off easily once you get it started.

Clean off the panels with iso alcohol, remove the shim washers, use a
razor blade or a hobby knife to clean up your custom made seals on the
opening.

Reinstall the panels, tighten the screws, don't worry about it for 20
years or so. The seal is permanent, you don't have to do squat to it
when you R/R the panel.

FWIW, I've also used this same method to seal wet-wing fuel access
panels. The primary difference is the fuel panels use sealed
nutplates.

TC

>We are working on a 64 M20C Mark21, it does not have the "forward windshield
>speed mod", still the factory design. There are two panels in front of the
>windshield on the outside that cover the avionics assembly inside. They
>have been sealed with silicone so many times that it took us 4 hours to
>clean them up. I don't want to use silicone again. I'd prefer to use some
>sort of pliable, removable sealant.
>
>What is the preferred method for sealing those two panels (actually, there
>are three as there is a small narrow one that covers the other two)? And
>what do you use to seal the screws?
>
>Any help would be appreciated?
>
>Thanks in advance,
>Alan - please remove the obvious email address extension to reply via email.
>