Instrument Panel Overlay

[Onewinglo]

During my search for a 170 I have seen several airplanes with the instrument panel overlay missing. Is the overlay being reproduced? Or de we search the salvage vendors if we need one?
Thanks,
JP

[bagarre]

The 1952 and prior style overlays seem to be scarce.
No one is making them anymore but there have been several conversations on this forum about reproducing a few.
With the right press or hydroform it woudlnt' be that difficult.

The real trick is getting your hands on a complete set of bezles tho.

[48RagwingPilot]

I have the overlay from my '48, but have parted out several of the bezels. If interested, let me know.

[Ryan Smith]

Would a metal replica be absolutely necessary, or could composite (fiberglass or carbon fiber) be suitable? Composite molds are a lot easier to make than metal molds. I am confident that bezels could be made for these panels as well.

56D has all of the original trim panels, but they have been patched up and whatnot, so converting them to an 8-hole configuration would be a little difficult. Once I own the airplane, I will be looking into making a full set of carbon fiber interior trim pieces - door posts, trim panels, glove box; everything. It's not because I don't have them (sans glove box), it's because they're 60 years old, scarce, and may be in need of repair. Originality, to me in the context of these airplanes, is the shape, appearance, and feel of something. The part being metal holds little to no credence with me personally, just as I have the original (beat up) metal pants for our airplane, but will install Lahti Aerospace carbon replicas instead. The parts are going to be painted anyway, so I would rather save some weight and gain some strength than to say that my airplane is 100% original...because it never will be.

Anyway, $20K in startup costs for a low-volume metal part doesn't seem to make sense when there can be less than 10% of that invested in replicas that will be stronger, lighter and more easily reproducible without a machine shop. One can make beautiful layups in their garage. Most guys don't have a 30-ton hydroform press sitting around. Making metal replicas seems a bit daft, even for a deft metalworker. (just for Bruce )

[Karl Towle]

I have some ideas that may be useful to this thread. A friend of mine has a C170A with the Lycoming conversion. Here is a picture of his panel, which includes overlays that were custom made.

Although I don't have pictures of the forms he used, I copied his ideas and fabricated a form to make a custom overlay for my own '54 'B' model.

The form was made from 3/4" MDF wood as follows:
1) After the aluminum was completely fabricated for the panel, before it was populated, it was clamped to a piece of MDF and the hole saws used to make the panel, were run through the same holes, into the MDF (the pilot drill was pulled up inside the hole saw a bit).
2) A second layer of MDF was placed behind the first, and the 1/4" centers of each instrument hole were drilled through the second layer to give trapped air a place to escape. These two layers were screwed together with three screws from the back.
3) The outside of both layers of MDF was cut with a band-saw, and sanded to the exact shape of the aluminum.
4) A bull nose bit in a router was used to round all the edges of the form. Some detail work around the adjustment knobs for altimeter and DG had to be carefully worked, and the rectangle opening for the GPS had to be opened up to accommodate the panel dock.

The completed form was taken to Texas Aeroplastics at NW Regional Airport (52F). Jerry fabricated an overlay using burn tested material, and did it in a very short time. A sheet of thermoplastic is placed over the form, heated with infrared, and then vacuum is applied to suck the plastic down around the form. The secret is an accurate form to work with. When finished, the plastic itself needs to be prepped and coated with a plastic stain to the color of choice. They stock these materials as well. See: http://www.buyplaneparts.com/

Once the overlay is made, the back of each hole has to be accurately cut out. A Router, router table and a Dremel saw blade make the task of trimming the holes and the edges quite easy.

The overlay can be mounted to the panel in a variety of ways. To keep screws away from the face of the panel, very small 4-40 nut-plates were mounted around the perimeter of the panel, in the space between the back of the panel and the airframe. Then holes were drilled in the overlay matching the nut-plates and stainless 4-40 machine screws hold the overlay in place. The holes along the bottom require careful placement so the screws can be accessed with an extra-long Phillips screwdriver between engine controls, switches, avionics and the like.

When finished and installed, the overlay looks like this:

This overlay has been through many seasons of hot Texas weather with no problems. The mold is still on hand, so additional overlays can be fabricated. The one improvement would be to over-size the outside edges very slightly. As it was, the overlay shrunk just enough after being removed from the form to make it slightly tight when installing. Just the thickness of a strip of, say duct tape, around the perimeter should be enough to improve the final fit.

Hope these ideas can be of use.

Karl

[blueldr]

A very, very nice looking job, Karl. Congratulations.

[hilltop170]

Very nice work Karl! I'm assuming Texas Aeroplastics uses a thermoplastic sheet heated up in a vacuum chamber? Or is it layed up with cloth and resin?

[Onewinglo]

Karl,
Your overlay looks very nice. You did a great great job. Thanks for sharing your process.
JP

[johneeb]

Karl,
Both of those panels look great!

[Karl Towle]

Richard - Thanks for pointing out something I meant to detail in my post. I've edited it to include the thermoplastic-vacuum process. It's quick, easy, and relatively inexpensive.
Karl

[cessna170bdriver]

Karl,

I wonder if that form or something like it could be used to hydroform a thin aluminum sheet?