In the fall of 2003, while the Cheetah was down waiting for new cylinders from ECI, I decided to install the replacement instrument panel overlay I bought from Fred Kokaska at the 2003 AYA convention in Georgia. This is getting to be a pretty popular project for Grumman owners, as the old plastic overlays are getting ugly and falling apart. Fred's replacement overlays are aluminum, and all the standard instrument and screw holes are cut on a CNC machine of some kind, and all line up perfectly. Mine had been sitting in my house since the convention, but I think there must be an old avation adage about the usefulness of an instrument panel in a house. So began an Airplane Project.
The Old Panel Overlay
This is what I started with (click the picture for a larger view). Not bad for a 25 year old overlay, but I never cared for the color much, and if you look closely you'll see quite a few cracks. If you're a Grumman pilot you'll also notice that this is not a standard Grumman panel: there's a 3ATI hole for the Argus moving map, and a large rectangular hole for the GPS above it. Neither of these were pre-cut in the replacement overlay.
The first step was to remove the old panel overlay. (This is definitely not owner maintenance - I arranged to be supervised by my A&P for this project). To do this, the deck over the instruments and the eyebrow had to be removed, followed by every screw in the overlay. The knobs had to come off the VORs, DG, and TC/autopilot (with a .050" allen wrench for the set screws), and the retaining nuts had to come off all the switches. Finally, the fuses in the panel and the ALT warning light had to come out, which meant cutting the wires they were connected to. The ALT warning light has four wires coming off of it. I labelled carefully.
With all the screws removed, the overlay came off without a fight, albeit in five pieces. Behind it is an ugly aluminum sub-panel, coated with the remains of the glue that once held the overlay in place. I've heard that in some cases, this glue still has a hold on the overlay, but I was lucky.
Right Side of the Panel Without the Overlay
(I have a picture of the left side of the panel without the overlay, but it came out very badly. Looks like I was shivering.)
Back at home, I pieced together the remains of the old overlay, and decided that it was intact enough to use it as a template for cutting the new one. With my trusty Blue Sharpie for marking, I began a slow process involving measuring 500 times before cutting.
First I traced the outline of the old overlay onto the new one. Fred's aluminum overlays are slightly larger than the originals, and if you've got one of Gary Vogt's replacement eyebrows like I do, they need trimming or the eyebrow won't fit around them. After tracing the old overlay, I found I needed to remove about 1/8" around the curved edge of both panels. I decided to do this with a flat bastard file, because I could go slowly enough to be very precise. The straight edge of the right-side overlay needed trimming also; to keep it straight I clamped two pieces of scrap oak I had lying around along either side of the edge, and filed the metal flush with the oak.
The Altimeter
I needed to cut a completely new rectangular hole in the left panel for the GPS, and enlarge an existing round hole into a square one for the moving map, but even with a completely stock panel there would still have been metal cutting to do. The altimeter, VSI, and VOR receivers all have little tabs on various sides that surround their adjustment knobs. These tabs aren't pre-cut in the overlay. It would have been pretty easy to cut these out with a Dremel and a routing bit, but the file had made fairly quick work of the edge of the panel, and I decided that in the time it would take me to make a template for the tabs, which are not all quite the same shape, I could file out the cutouts. I used a round and a flat bastard file to do this; it took about fifteen minutes to do each tab. The old overlay worked as a template for the tab shape, though I had to make several trips to the airport and do test fittings to get it exactly right. Some of the cutouts for the tabs around the NAV radios (I have Narcos) in the original plastic overlay were larger than they needed to be, which I didn't discover until after I had cut the new ones. The knobs on the radio cover this up nicely, though.
Two Bastard Files and a Nibbler
For the GPS hole, I bought a nibbler. The new overlay is made from .040" stock, and a nibbler cut through it easily, but I found it was better not to nibble all the way to the edge of the hole, because the metal does distort somewhat around the nibbler bit. I stopped about 1/8" from the edge and finished the hole with a file. The same technique worked to enlarge the hole for the moving map.
During the many test-fittings of the panel-in-progress, another thing became apparent: the instrument holes in the new overlay were exactly the right size for the instruments. This would be a problem, obviously, when the panel was painted. I did some searching on the Grumman Gang archives, and found that the installers who had gone before me advised enlarging the instrument holes between .006" and .010" to allow for the thickness of the paint. I used a 2" sanding drum on a handheld electric drill to enlarge the holes. The drum was large enough that it kept the holes round, and running it around the periphery of the holes at low speed a few times took off the right amount of metal. (I used calipers to check). I should have taken a little more metal off around the airspeed gauge - it has a squared-off bezel and is just slightly larger than all the other instruments, and was a very tight fit in the end.
Unibit and Deburring Tool
Then there were the smaller holes I needed to drill for non-standard fuses, switches, and screws that had been added to the panel at some point in the aircraft's life. I used a #1 Unibit in a handheld drill for all of these. The Unibit is a step drill bit that goes from 1/8" to 1/2" in 1/32" increments, and with a little practice it doesn't leave a burr on the front-side of the hole, like a regular drill bit does. As long as you drill pilot holes with a small sharp standard bit first, the Unibit won't wander during drilling. This is a Cool Tool.
Once all the instrument holes were cut and enlarged, I used a hand deburring tool from Aircraft Spruce to deburr the holes and the edges of the panel. This tool is just a pivoting blade set in a handle. When you pull the blade along the edge of a cut, it slices off the burr in one or two passes. It works on flat edges or along curves equally well. For deburring drilled holes, I put the point of a larger drill bit against the hole and twisted it once or twice by hand.
Several more trips to the airport later, I was finally satisfied that everything was the right size, and ready to paint the new overlay.
The Old Glovebox Door
The left and right halves of the overlay were finished, but there was one problem: the old glove box door. It still worked, and it wasn't cracked, but it was going to make for one ugly gray-green wart on the new panel if I didn't replace it. Obviously I wasn't going to be able to buy a replacement anywhere, so I started thinking about how to fabricate a new one.
The simplest replacement would be a simple sheet of aluminum cut to the same size as the existing door, with rounded corners. Fred Kokaska himself suggested another possibility: forming the edges of a slightly larger piece of metal so that they rolled in towards the panel, much like the existing door. Evidently someone has done this with a beater bag and a mallet, and had good results. I think you could also do this with a bead roller, which would probably require less skill (but more money...funny how it always seems to work that way.) I decided against these more complicated solutions because I was running out of time. I wasn't sure how well a flat glove box door would resist bending, though. The door would be stabilized along its lower edge by the hinge, but I wasn't planning to put a stiffener at the top edge. I didn't want it to end up feeling flimsy. In the end got a scrap of .050" 2024 at the local FBO. I think .040" probably would have been just fine too.
For a knob I visited Home Depot's cabinet hardware section, and picked the only black plastic knob they had. I looked for a magnetic closure there, too, but they were all big and ugly. So I went to Radio Shack and bought two pairs of rare earth magnets. These are tiny - they're 1/8" in diameter and about 1/16" thick, but they're incredibly strong for their size. My extremely non-scientific in-store analysis suggested that four of them would be strong enough to hold the door shut, as long as I was smart enough to align the opposite poles towards each other when I installed them. I was planning on gluing one pair to the door, and the other pair to the front of the lip of the glove box, where they would be squeezed against the back of the panel when the glove box was screwed back in.
I traced the old door onto the sheet of aluminum, and cut it slightly oversize with a Dremel and cutting wheel. Then I filed it to size with wood clamped in place along the edge to keep things straight. I cut the corners off with tin snips and filed them until they were smooth. This all took about an hour.
I drilled out the rivets holding the hinge on the old door, and drilled holes in the new door using the hinge as a template. (Clecos are a wonderful thing.) I haven't gotten around to buying a rivet squeezer yet, so I took the parts to my mechanic and we riveted the hinge to the new door.
Left Side of the Overlay Before Painting
Right Side and Door Before Painting
All the metal cutting was now finished, I had a pair of panel overlays and a door, all needing paint.
But paint, or powder-coat? Most people are already familiar with painting. Powder-coating is basically a process of taking ground-up paint, spraying it onto a charged surface (the charge makes the particles stick), and then heating the part in an oven until the paint melts and flows into a nice finish. Powder-coating generally results in a harder surface than the same paint would if it were applied as a liquid, but it's also more expensive for one-offs like panels. You can sometimes find a powder-coater willing to run your part through with a much larger job, and save the setup costs, but not if you're going to be picky about the color, and I knew I was. I decided to powder-coat anyway, because I wanted the harder finish, but there are lots of great-looking painted panel overlays out there. Powder-coating usually doesn't use a primer coat, so I attacked the new overlays with a Scotch-Brite pad to give the paint some texture to stick to.
There are several different formulations of powder available. Epoxy is the hardest, but doesn't stand up as well to direct sunlight, and panels tend to get a lot of that if the airplane lives outside. I picked aliphatic polyurethane, which is a little softer but much more stable.
And there was still one other thing to think about, before I even got around to picking the color: different powders have different finishes. You can get textured finishes, wrinkles, and crackles if you're so inclined, although any of these finishes will limit your color choice considerably. I decided I wanted a smooth but low-gloss finish, and settled on a light beige color. I ended up using DuPont powder, mostly because their website had the best information (paint companies, apparently, have yet to embrace the Internet.) Dupont's powder part numbers have as their last digit an encoded gloss value: just take the number, multiply it by ten, and you've got the percentage of light that is reflected by the paint. The powder I eventually used was part number UFL602S4, so the value was 40%. I was a little worried that this might be too much, but having flown with the panel it's fine. The color is "Square Beige", which is so light that it's almost white.
Painted Overlay
Overlay with Placards
I found a local shop with some experience to do the powder coating. It took a few days, and cost $100, including the cost of the powder. I had to buy 2 1/2 pounds of the powder, even though the panel used much less than that.
They did a good job, though.
Now the panel needed lettering. I got the Grumman-specific placards for the panel from Fletcher Aviation. These were black-inked placards on a self-adhesive silver background, which once I got them installed, I wasn't all that happy with. I also needed to label some switches and fuses that weren't included in the set. I started looking around for alternatives. Aircraft Spruce carried a set of dry-transfer letters, in black, that would stand out well on the panel and give it a much more finished appearance. The set pre-dated GPS, and so it didn't have labels for some of the fuses that protected more modern equipment in the panel. But it did include a small alphabet with three copies of each letter, and as it turned out it wasn't hard to build words from fragments of other words. In fact it worked well enough that I replaced as many of the stick-on placards with text from the dry-transfer set. (If you ever try this, practice first - I had to remove one set of letters and start over).
I put a coat of clear polyurethane over the dry transfer letters to protect them, and the panels were finished.
Installing the Overlay
As luck would have it, I picked one of the coldest days of the winter to install the new overlay. This is probably why the picture at right is blurred - shivering again. Once my feet got numb it wasn't too bad. Seeing the overlay in place after all this work probably kept me warm.
A credit-card shaped piece of plastic helped to flex the lower panel plastic off the panel enough to allow the new overlays to slide underneath it without cracking anything. Then I started screwing the panel back together.
I had gotten some new black-oxide coated brass instrument screws in different lengths from Aircraft Spruce, since some of the old ones were looking a little crusty and old. I also replaced the four high-strength screws that hold the whole panel in place with new ones. A few of the holes in the panel ended up slightly off or slightly too small, so I enlarged them with a needle file. (Some masking tape on the overlay would have been a good idea while filing, because the file slipped and put a small scratch in the finish. Oh well.) The filed parts aren't visible with the screws in place, but it did slow the installation down a good bit. It takes much longer to put four screws into each instrument than you might think, and some that were slightly off didn't become obvious until three screws were in place.
The Finished Panel
If I remember right, it took me about five hours to get the overlays installed. I was lucky enough not to have any major suprises during installation, and everything still worked when we tested it after I finished.
Flying behind the new panel is fantastic. I like the high contrast between the instrument faces and the panel. I don't know if it actually makes my scan better, but it's sure easier to pick out an instrument on the panel before shifting focus to it. One concern I had when picking out the color, that the setting sun behind the panel would be a little blinding, just isn't so. It's never that bright.
Of course, now some of the other original interior parts look a little shabby by comparison. Especially the seats...