Sealing cowl/avionics bay covers against water?

[justincarter]

Hello all.

This is my first post.

I have a '67 M20F based in the North-east of England. Its a pretty rare bird in these parts so there is relativley little expertise available in the area (or even in the whole of the UK really) which is why Im asking the for collective knowledge of the forum.

As you may know it rains quite a lot in the UK and during a flight back from Germany to the UK (after an annual during which the top cowl and the avionics bay covers had been removed) you can imagine my alarm when I was in marginal VFR and rain and my feet (and no doubt therefore my avionics!!) started getting wet.... the flight ended uneventfully and i hadnt fried my avionics but the whole episode leads me to ask......

What solution have folk found the best for sealing a) the joint where the rear edge of the top cowl overlaps the front of the avionics bay covers and the joint where the rear of the avionics bay covers overlap with the fuselage just below the windscreen... against water ingress.

i.e. whats the best way of sealing the cowlings to prevent water getting into the avionics bay?

At present, there are some old neporene strips (which look very tired) underneath the avionics bay covers (between the frame that the avionics bay covers are screwed to and the covers themselves) but nothing really in the gaps a) and above.

 

thanks very much in anticipation of your replies!!

Best wishes from sunny England!!

 

Justin

 

 

 

[sleepingsquirrel]

There is a service bulletin for a metal strip which could have been purchased in years past. Where I'm from duct tape works well. I would recommend this 200  MPH tape instead of the 100 MPH stuff. 

 http://www.ebay.com/itm/2-RED-RACER-DUCT-TAPE-200MPH-IMCA-/400242713410?pt=Race_Car_Parts&vxp=mtr&hash=item5d30532342

[sleepingsquirrel]

This is the link to the service bulletin, but the 200 MPH tape is easier and less expensive.

 

http://www.mooney.com/images/pdfs/sb-pdf/sbm20-97.pdf

[Steve65E-NC]

      In my 20 year experience with a 65E, rubber gaskets just do not work.  And, I lost a DG and AI trying it (the water poured right onto the intake filter for them).  Five minutes after takeoff both instrument faces were full of bubbles (if this happens to you act quickly to get the instruments to a rebuild house and dried out). 

   I now, and for the last 18 years,  use the recommended 3M Strip Calk Part No. 08578.   The box has 60 feet stored in strips between two pieces of wax paper.  It does not dry out and can be reshaped for reinstallation.  One box will last for decades.  I put it on all four sides on airframe at faying surface of cover before putting cover in place.  I surround all screw holes but keep drainage channels clear.  A little usually squirts out at spots around outside  and I trim it with  a sharp piece of plexiglass to avoid damage to paint.  It can be applied with top cowel either on or off.  I carry a baggie with a few strips in my ready tool kit to add to any areas that are weak if I have to do a field access to the bays.      

[takair]

Thanks Squirrel.  I was not aware that SB was out there.  Looking at it, it looks like my 64 has it.  I even seal it in a similar fashion with a strip of weather sealant on the outer side of the channel, but did not think to put it on the inner side.

Justin...if you have a similar installation, i think sealling it like the SB would help.  When I bought my plane, somebody had caulked the channel.  It leaked.  Basically the channel is there to drain extra water.  Keep it open.  The problem with any type of caulk is that it needs to be reapplied each time to keep its integrity.  Over the years I have found a few things that help. If kept outdoors, use an aircraft cover that covers the avionics bay.  This helps keep water out when on the ground.  Next, clean up old attempts at sealant and install fresh weather strip or sealant in a similar fashion to the SB. Weatehr strip allows easy future removal.  I add a dab of RTV to each screw to help seal there.  WHile there are sealed nut plates, they still tend to leak.  If I know I will have the plane outside without cover, or if I know I will be flying in rain, I add a bead of RTV to the outside of the cover.  It is not pretty and must be reapplied after removing the cover, but it seems to help.  Squirrels speed tape would do the same.  Mooney also used to add a plastic rain shield over the radios, inside of the bay.  Many have been removed.  In my case there is not enough room to reinstall it.  If you have room, you can fashion one out of aluminum or plastic....or find an original.  It basically redirects the water to your feet.  While I love the convenience of the bay....this is a significant downside.  Ultimately, you could install a 201 windshield to stay dry and go fast at the same time.  Good luck.

[takair]

Quote: Steve65E-NC

      In my 20 year experience with a 65E, rubber gaskets just do not work.  And, I lost a DG and AI trying it (the water poured right onto the intake filter for them).  Five minutes after takeoff both instrument faces were full of bubbles (if this happens to you act quickly to get the instruments to a rebuild house and dried out). 

   I now, and for the last 18 years,  use the recommended 3M Strip Calk Part No. 08578.   The box has 60 feet stored in strips between two pieces of wax paper.  It does not dry out and can be reshaped for reinstallation.  One box will last for decades.  I put it on all four sides on airframe at faying surface of cover before putting cover in place.  I surround all screw holes but keep drainage channels clear.  A little usually squirts out at spots around outside  and I trim it with  a sharp piece of plexiglass to avoid damage to paint.  It can be applied with top cowel either on or off.  I carry a baggie with a few strips in my ready tool kit to add to any areas that are weak if I have to do a field access to the bays.      

[Steve65E-NC]

Rob, Yes, I use the black 3M strip stuff.   No problem with bending panels on my 65E with SWTA 201 windshield.  If I ever felt something was about to bend or kink I would drag out the old hair dryer.   No bending  problem before windshield install when panels were slightly larger and rectangular either.  I also now have a good cockpit cover and I am careful to cover the panels if I am tied down during transit.  When I had the instrument problem I was without good cover and the plane set outside in the rain for a day or so before flight.  I never see any drips inside when I wash the aircraft.   

[1964-M20E]

I use 1/8" thick by 1" neoprene foam rubber gasket material and it seems to work well and if I suspect I'm getting leakage a little siliconized latex caulk from Home depot from the outside with eh panels attached works wonders and comes off fairly easily.  The 3M stuff is a pain to clean off IMHO.

[justincarter]

Well thanks for all your replies - As it happens, i did fashion a piece of perspex to sit over the radio stack (although i had no idea this had once been an official item!). I never leave the aircraft outside in the rain uncovered.  Ill try to arm myself with both some 200mph tape and the 3M stuff and see how i get on with each. Thanks again for your help!!

justin

[Immelman]

+1 on the 3M strip caulk rubbery sticky material. Lay down a bead - you work if with your fingers - maybe 3/16" or so, and screw the panel down over it. It will compress to a good inch-wide layer. Yes, re-doing it when the panels are reopened is a pain in the butt. The sealant on there can be reshaped/reformed to seal the panel again, every few openings maybe a little more has to be added to ensure there is enough for a good seal.

[mbroady]

Hi Justin, no solutions to your problem (in fact I leave mine out with no cover at Liverpool with no problem but am just ordering one to be on the safe side) but just to say hello- not many of us in the UK. I have a 1976F and love it to bits, although she doesn't always love me back! Maybe see you around sometime.

Mike

[jwilkins]

My '62 C leaked despite all attempts to seal the panel until we taped a heavy plastic sheet down with the 200MPH duct tape, THEN put the 3M caulk tape on top of the duct tape. In case you live in a cooler area as we did back then, the 3M caulking squishes (technical term) down much better when it is warm. The diversion panel underneath is a really good idea. Your radio stack doesn't get wet and the water on your feet lets you know the panel is leaking again.

It is possible to get these panels sealed up, it just takes time. Even with the plastic sheet, diversion panel, and 3M I still ran a very small bead of silicone sealer around the outside. The sheet and duct tape, plus 3M sealant was working but I liked the idea of reducing the amount of water they would need to deal with.

The 3M sealant can be worked under the screw heads to seal without bonding, too. 

I put a G430 in the C back in the dark ages when the avionics guys said it was a waste of money to put that much radio in a 62 C. There was even a magazine article that said something like "Well, if you put a G430 in, for instance, a 1962 Mooney of course you will never get your money back" The old stack we tore out had rusty trays and water stains so I was paranoid about leaking on the radios. After doing the plastic sheet, 3M and diversion panel, every subsequent annual looked dry underneath.

 

 

[Sabremech]

I use some PR1422 A2 when I put my panels back on. I spray some mold release on the panel before tightening it. They come off with a little work and no leaks. 

[Guest]

Apply a very light coating of grease to the aircraft side. Apply a bead of ( now called )Pro Seal to the covers, secure with Clecos for a few days. Remove Clecos clean threads and torque screws. You now have a reusable water tight seal.  I use approx 23 inch pounds. Never a leak on my Mooney 16 years, also what I use on experimentals. 

[MARZ]

I've been toying with the idea of elimnating the three individual covers and going with a single piece across the cowl - any thoughts? 

[animalmover]

I just tape either side of the seam ( 1/8 - 1/4 inch away ) with painters tape and lay a bead of clear silicone down. Cleans off easy during annual.  Has worked great for years.

[Cris]

welcome to the forum Justin!

I also own a 1967 M20F in England, I am now returning to Fairoaks after a couple years in Madrid. We should meet up!

It seems on mine there are liberal amounts of silicone sealant along the top cowling panels, not the prettiest solution but I have never had an issue with water leaks.

 

[podair]

welcome to the forum Justin!

I also own a 1967 M20F in England, I am now returning to Fairoaks after a couple years in Madrid. We should meet up!

It seems on mine there are liberal amounts of silicone sealant along the top cowling panels, not the prettiest solution but I have never had an issue with water leaks.

(for some website bug  I got upgraded to an M20S above! Sorry Chris)

[justincarter]

Thanks very much to you all! Some really helpful suggestions there. Hopefully, my enacting your tips will save me from the nightmare of electrical/avionics failure in the clag!!

 

You UK based F drivers- ill drop you a PM...

 

justin

[sleepingsquirrel]

Just to report, on tape which I have been using, cleaning off the tape residue may cause me to look for a different method. While tape is easy to put on. It can cause damage to the paint. The residue is difficult to remove when renewing the sun worn tape. I did this today and put tape back on as usual , because it is so easy and cheap and I'm lazy and not ready to try the masking and bead laying down someone mentioned. Maybe I shouldn't have used a blow torch to remove the residue!

[0TreeLemur]

Reviving old thread because I'm curious if anyone has a photo or a drawing showing the plastic rain diverter that keeps leaking rainwater off the radio stack?   I think that is a heck of a good idea given the amount of money that is in that pile of hot boxes, and the likelihood of a leak above.

-Fred

[takair]

2 hours ago, Fred₂O said:

Reviving old thread because I'm curious if anyone has a photo or a drawing showing the plastic rain diverter that keeps leaking rainwater off the radio stack?   I think that is a heck of a good idea given the amount of money that is in that pile of hot boxes, and the likelihood of a leak above.

-Fred

I had to remove mine because I ran out of room to fit it.  I can dig it up and take a picture, but I think most modernized Mooney’s will have the same issue.

[0TreeLemur]

14 minutes ago, takair said:

I had to remove mine because I ran out of room to fit it.  I can dig it up and take a picture, but I think most modernized Mooney’s will have the same issue.

Recent experience suggests that my radios would benefit from something.  If you can find yours and post photos it would help me learn from that to fashion something workable.  Thanks!

[takair]

On 5/28/2019 at 9:32 PM, Fred₂O said:

Recent experience suggests that my radios would benefit from something.  If you can find yours and post photos it would help me learn from that to fashion something workable.  Thanks!

Looks like the same plastic as interior.  10” x 9”.  Missing corner is 1.5 x 1.5.  Bent to fit.

[TheTurtle]

i bought the strip caulk but it looks like a mess.  I take my IP cover off fairly regularly and the strip caulk looks gooey especially in the high heat and sun here.

I just went to los depotos and got some double hump weather stripping.  similar to this.  https://www.homedepot.com/p/Frost-King-5-16-in-x-1-4-in-x-17-ft-White-D-Center-EPDM-Medium-Gap-Weatherseal-Tape-V25WA/100017014

seals tight and there is no goo.  It's been on for about 2 years now with no issues.