M20F Plastic Surgery - With Pictures

[canamex]

I purchased my '67F N9611M a few years ago and have flown the pants off of it, going from my home base of Mexico City to Airventure (2x), Victoria BC (6x), the Caribbean, lots of places all around the western US and all the way up to Yellowknife NWT via Saskatchewan. I've flown N9611M over 650 hours and that means I've spent a bit more than that inside of her. As cozy as she is, she was in need of a little help.

While the seats, carpet, and lower upholstered panels were re-done by the previous owner, they left the plastics as-is, cracked in some places, ruptured screw holes in many places, and a general yellowing effect which didn't look great with the brighter upholstery. Below is a photo of the original interior:

As you can see, the previous owner decided to leave the original upholstery on the arm-rests and the "vintage" plastic panels look a little dated. Frankly, had the panels been structurally sound I probably wouldn't have touched them but hours of long x-country flying had taken their toll on the arm rest seams and from time to time my elbows would get pinched from the open seams. I also had a theory, still to be tested, that the panels in their condition were letting a bit more noise into the cockpit than originally intended.

With all this in mind, a couple of months ago I began the process of disassembling the interior of the aircraft in order to move all of the pieces to my workshop and begin the restoration process. This was the second time I had removed some of the interior, the first being during my pre-buy, but this interior removal was certainly more thorough and involved more electrical connections and visits to Mooneyspace to figure out how to get those darn circular vents off.

The de-install went well and I found an airframe still with zero corrosion and only mildly decaying foam fiberglass insulation and foam, generally in pretty good shape for an old bird!

Once at my workshop, I surveyed the damage and found that there were three intact panels in total, all window frames, and the rest had some form of cracks, punctures, or other deformations with the worst offenders being the footwell side plastics, the ceiling panel, the door, and the pilots side lower panel.

In my research, I had found that there were two main schools of thought when repairing and re-beautifying the panels. One, was to follow the Aero-Comfort system of reinforcing the panels and then covering with a fabric or leather. I had spoken to Hector a couple of times and was impressed with their product and found him to be knowledgeable and helpful, however I really enjoy my 1000lb+ useful load and wanted to add as little weight to the aircraft as possible. While super-lightweight coverings do exist, and would have solved another problem with the window joins (which I'll get to later), the weight consideration, getting FAA approved products into Mexico, and cost all played a factor in deciding to restore the panels via option two.

Option two, which I went with, was to fix the panels from behind, and then paint. The trick would be to figure out how to fix them so that they wouldn't break again, at least not for a long time, and then how to paint them in both a color and sheen which fit with the existing upholstery scheme.

First thing to figure out was what material we were working with. According to the manufacturer, Spartech, it's ABS plastic. Yes, there are some special mixes and flame retardant elements in there but it's ABS.

The next thing to figure out was the best way to repair ABS plastic. After exhausting the interior plastics threads here on Mooneyspace which all offered different options for plastics reinforcement including glue, fiberglass, and tape(!) solutions, I turned elsewhere for inspiration and found it in a lovely video from an Australian gentleman. It seems that the best way to reinforce ABS plastic is with ABS plastic!

Being in Mexico City, it can be difficult to acquire the right, certified materials for any job and while they do exist, proper caution is wise. Case in point, after visiting a construction market to purchase ABS welding rods, I tested the rods and found that they were smoking considerably on a piece of test material. When I returned to the market to ask the vendor about the product he'd sold me, he confessed it wasn't pure ABS and instead had a PVC mix at somewhere around 15% which was causing the smoking and would have resulted in an inferior repair. I had read somewhere that Lego blocks are manufactured out of 100% pure ABS plastic, and so went off on a hunt to dig up some white Legos. Luckily, Mexico City has a lot of Lego and just around the corner from my house was a Lego seller with several 40 gallon drums filled with used Legos, sorted by color. Scoop!

After bringing back the legos and verifying with a test piece, I started to weld the panels back together. Some photos below showing the extent of the welding pre-sanding.

Below you'll see a before and after sanding of a hole repair.

And a couple of shots of the footwell panels which were quite damaged from years and years of use. Special note: these panels were especially de-formed and I was able to straighten them using a heat-gun on the low setting before then welding them.

I'm not sure how to post my own videos here but I have some nice ones of shaking the panels and flexing them to try to break them again and they're flexible and strong as can be expected. The only time I managed to re-break one was when I flexed it on a non-sanded weld. Maybe it was the thicker plastic section hitting the thinner section at an angle?

With all of the panels welded and sanded, it was now time for paint. I chose an oyster white to soften the appearance of the interior and went to work. In the first picture, you can see the difference in color between the yellowed original panel, the original color seen where the strap covers had blocked UV exposure, and one coat of the new color.

And below is all of the panels laid out for painting, with the floor panels in the bottom left playing around with colors.

After rattle-can coats of paint on each panel, they were ready for install, and yesterday I went out to the plane to begin assembly. I'm re-doing the headliner but have been itching to fly so thought I'd put together the plane to see how things look before final assembly.

And once again, the before picture for reference.

Installed, the panels look very good. There are a couple of paint imperfections, mostly in deep corners, and I think a better paint product (or maybe more skill on the part of me, the painter) would have solved this issue.

That's where I've gotten for now, next up is:

• headliner and ceiling panel install
• de-install of the panels to upholster the arm rests with the same material as the seats
• install of freshly painted passenger headphone jack covers (more on that next time)
• sourcing and install of those thin window joining strips

I'm looking for help with adhesives recommendations for both foam to aluminum and foam to vinyl, as well as if anyone knows where to find those little strips which go between the windows?

 

[Supereri73]

What a wonderful write up. Thanks for this. Another interesting way to do something similar is to melt the pvc in acetone and then use it like a putty. I've done similar when building plastic models for filler.

[Z W]

Looks great.

I buy ABS plastic filament in rolls on Amazon for 3D printing.  Might be a good alternative to sourcing used Leggos and comes in lots of colors.  Would be a lot like TIG welding I'd think.  Never tried it myself.

[Fly Boomer]

7 hours ago, canamex said:

I purchased my '67F N9611M a few years ago and have flown the pants off of it, going from my home base of Mexico City to Airventure (2x), Victoria BC (6x), the Caribbean, lots of places all around the western US and all the way up to Yellowknife NWT via Saskatchewan.

You are truly a "Traveling Man".  Ricky Nelson sang about you!
 

[canamex]

I'll try both of those, @Supereri73 and @Z W , thanks for the suggestions. I chose the thinnest 1x6 legos I could find to make it the most like TIG welding as possible but filament would certainly help get to a finer result! I Now I just need some more Royalite panels to repair...

[Nokomis449]

Excellent write up on the process, thanks for the inspiration as my 68G could use the same TLC.  Would love to see the videos if you can post a link.

[milotron]

This is a great write up and inspirational as I have the same project planned in January while waiting for my prop to get overhauled.

Do you have any pictures of the finished areas of the repairs? Were you able to effectively match the texture of the panels?

 

The SEM paint products work exceptionally well for this on the panels that I have already repaired.

[Mooney-Shiner]

I like this tool for plastic repair:

[AH-1 Cobra Pilot]

One of these will simplify getting the plastic to the right spot.

https://www.amazon.com/gp/product/B08HM4133L/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1