Avionics access panel seal

[Shawnson]

The seals on my access panels look a bit different than what I have seen posted elsewhere. Does anyone know where to source this tube-style seal? This is on a 76 M20F.

 

[Ragsf15e]

Nasty stuff.  3m weatherseal moldable putty.  Real fun to work with.

 

[Ragsf15e]

https://www.aircraftspruce.com/catalog/appages/windowsealant.php

[Shawnson]

2 hours ago, Ragsf15e said:

Nasty stuff.  3m weatherseal moldable putty.  Real fun to work with.

 

No, this is like a molded rubber gasket.

[Slick Nick]

Where’s that door seal guy? He makes all kinds of stuff like this. 

[Hank]

Didn't Jose used to recommend a particular size and shape from the Aviation aisle in the big orange box store?

My C has some even nastier, sticky black stuff under there.

[Hank]

2 minutes ago, Slick Nick said:

Where’s that door seal guy? He makes all kinds of stuff like this. 

@Gee Bee Aeroproducts

[Ragsf15e]

1 hour ago, Hank said:

Didn't Jose used to recommend a particular size and shape from the Aviation aisle in the big orange box store?

My C has some even nastier, sticky black stuff under there.

It’s usually the sticky black stuff which is the 3m caulk sticks.  I’m sure you could make other stuff work.

[Shawnson]

1 hour ago, Hank said:

Didn't Jose used to recommend a particular size and shape from the Aviation aisle in the big orange box store?

My C has some even nastier, sticky black stuff under there.

I read a thread about the square weather strip stuff from the box store. I dont see how it would work on mine. My panels sit flush against the rest of the skin. I thought about just gluing some round silicone tube down but since it looked like a formed gasket I thought maybe there was a part number.

[47U]

On 4/8/2026 at 9:02 PM, Shawnson said:

I read a thread about the square weather strip stuff from the box store.

Aviation isle at Home Depot.  I think this version would work for your style access panels.  There are several size variations.  You do NOT want the sticky stuff (in my opinion).

 

I used a slightly larger version.  It came as two beads together on the roll and I split them before install.  On the early ‘60s access panels, you don’t want to put the seal in the drain channel.  This stuff holds up well, it’s be maybe 10 years since I put it on.  Full disclosure, I have a hangar and use a Bruce’s cover when RON away from home.

[Ragsf15e]

The sticky stuff is a pia to work with, but it seals well and will form to the shape.  It can be hand rolled like clay to make whatever thickness you need.  It works, but did I mention it was kind of a pia?  Whatever you use, make sure you have a good seal and the cover is secure.  You don’t want a “cheap” or “easy” fix to let in water and destroy your very expensive avionics!

[Matthew P]

On 4/9/2026 at 11:33 AM, Ragsf15e said:

The sticky stuff is a pia to work with, but it seals well and will form to the shape.  It can be hand rolled like clay to make whatever thickness you need.  It works, but did I mention it was kind of a pia?  Whatever you use, make sure you have a good seal and the cover is secure.  You don’t want a “cheap” or “easy” fix to let in water and destroy your very expensive avionics!

So, what I've done is used tge 3M sealant but instead of placing the panel directly on it, I cut a thick piece of sheep plastic and laid over it so I can remove tge access panels without getting that stuff everywhere and when I need to access the brake reservoir, just peel the piece of plastic back, refill then reseat the plastic..so far, no mess and no issues

[Ragsf15e]

29 minutes ago, Matthew P said:

So, what I've done is used tge 3M sealant but instead of placing the panel directly on it, I cut a thick piece of sheep plastic and laid over it so I can remove tge access panels without getting that stuff everywhere and when I need to access the brake reservoir, just peel the piece of plastic back, refill then reseat the plastic..so far, no mess and no issues

Sounds good as long as you still get a good seal between the plastic and the caulk.  No matter how pia it is, you don’t want water in there!

[Gee Bee Aeroproducts]

I have many specific sizes of P seal

All 1-1/2 long

3/8 bulb used on the PC7 stab , we just finished this is charcoal grey silicone pre sold 1k feet

-1/2 used on the T34 canopy 

works well on the RV10 canopy 

5/8 lightweight 

5/8 std

-7/8 bulb

all similar to the cabin door seal 

Shown in the center picture 

 

There is nothing better than our two part clear silicone cement.

 

 

[phxcobraz]

On 4/8/2026 at 11:12 PM, 47U said:

Aviation isle at Home Depot.  I think this version would work for your style access panels.  There are several size variations.  You do NOT want the sticky stuff (in my opinion).

 

I used a slightly larger version.  It came as two beads together on the roll and I split them before install.  On the early ‘60s access panels, you don’t want to put the seal in the drain channel.  This stuff holds up well, it’s be maybe 10 years since I put it on.  Full disclosure, I have a hangar and use a Bruce’s cover when RON away from home.

This is exactly what I did on my C. Works great. I actually cut the strip down the middle so it would spread/flatten a bit more, and it seems to seal up great, while not bumping the panel out as much.

[47U]

1 hour ago, phxcobraz said:

I actually cut the strip down the middle so it would spread/flatten a bit more, and it seems to seal up great, while not bumping the panel out as much.

I reposted the access panel pic, not sure where it went.

The early vintage access panels are a little more challenging because of the small center section rectangular panel where there was provision for a comm antenna.  I used a close-cell foam weatherstrip on that piece, which is completely flat now.  The panel is pretty flimsy and is deformed by the screws, not sure if mine is original.  I should make a new one out of some left over .090” from my left-side panel replacement.  Someone made a one-piece panel which is probably better for sealing, but then you have to remove the whole thing if you only need to work on one side (like the hydraulic reservoir).  So far, the self-stick has held up well.  I’m using plastic washers under the screws, too, but not sure if that’s necessary.