Friday, May 1, 2020

New Instrument Panel

April 22, 2020:

You can see the first version of my panel here (see July 23, 2014), but a year ago I remade the panel again, because I wanted a black panel and a bit more room to add panel-mount USB ports to power/charge a Samsung Galaxy Tab S8 to replace my handheld Garmin GPS, which was just too small and has a complicated menu system). So I bought a small sheet of 1/4" thick UHMW-PE (ultra high molecular weight polyethylene) plastic and the next larger size steam pan. It worked well, but I had a LOT of radio noise that I thought was coming from the tablet, despite adding ferrite, clamshell chokes all over the place.

Then this year, I bought a fuel gauge to add to my cluster, which gave me opportunity to investigate new panel materials, because 1/4" was just too thick. My first material choice was blank circuit board stock that I thought would help reduce/shield radio noise, due to one side being copper that would theoretically become the sixth side (lid) of an electrically enclosed box. Sadly it was wasted, because I improperly measured the inside corner radii of the steam pan, so the gauges didn't fit. The PC board was also too thin at only 1.6 mm thick, so my next choice was going back to plastic. I bought 1/8" thick HDPE plastic sheet, revised the plan drawing with larger corner radii, and again discovered the two large instruments were still 1/16" too close to the pan side walls. The panel fit, but the center bowed out a bit, because the material was too flexible. I also "laminated" the inside with aluminum foil, to take the place of copper, but in-flight usage proved there was no radio noise shielding.

As they say, the third time is a charm and this time I didn't strike out.

This is the new, cram-it-all-in instrument panel redesign, which I made in Adobe Illustrator. It fits a standard, 1/3 Size (12" x 9") steam pan.

This time I used 3/16" thick phenolic grade XX board. It's the perfect material, because it's hard, light, extremely stiff, easy to cut, and has a glass-smooth finish on both sides. Phenolic is pressure laminated, epoxy impregnated layers of paper, cloth, or fiberglass. Grade XX is paper and thus the most economical.

I applied two layers of masking tape to the board to prevent my jig saw from marring the glossy finish. After tracing the paper template cutouts with a pen, I drilled mounting screw and saw blade "access" holes.

I tweaked a standard metal cutting blade by grinding about 1/8" off the back edge to make it thinner for easier cutting of the 2-1/8" holes. High speed on the motor and slow progress around the inside of the lines to get nearly perfect cutouts.

All holes were smoothed and adjusted for fit with a Dremel sanding cylinder (less than 1/32" in a few places had to be removed).

Tape removed, surface cleaned and degreased, and two coats of Krylon Fusion Gloss Black applied. Dust specks made for easily seen bumps, but who cares. I should have slightly sanded the gloss finish of the board before spraying to give the paint some bite. Even though it's made to adhere to plastic, I could see signs that it didn't bond to the epoxy resin.

Gauges, switches, 12v and 5v USB power, and +/- terminal strip installed. Oh, and some ferrite chokes and 0.01 uF capacitors on the 12v lines to the radio jack (left) and USB (center) to remove RFI. Dual socket USB panel mount unit is from AC Spruce and touted as RF noise-free. I can confirm that, yes, it is. It was my previous USB panel-mount unit, NOT the tablet, that was generating much of the radio interference that would break through my radio's level 7 (of 9) squelch. Without the engine running and LED strobes on, I can achieve a squelch level of 2. With the engine running, that goes up to 4. The strobes, even though made of LEDs, ups the squelch to 5 or 6. There's no effective way to filter the RFI generated by the DC-to-DC constant-current converters in those units. I've added shunt caps and ferrite chokes, to no effect.

The new panel finished and labeled, ready for installation. The thermometer is the smallest and simplest I could find at Walmart 10 or so years ago. It's held on by two small squares of "peg and peg" tape. That is, the material is like velcro in a way, but instead of two kinds of tape, one with hooks and the other fuzzy loops, this tape is made of hundreds of stiff, pin-head-like "pegs" in a tight grid array that interlock when pressed together.

Ta DA! GPS map provided by a Samsung Galaxy Tab S8 10.2" running Backcountry Navigator app, which records tracks, allows custom overlays (I made local class C sectional plots), waypoints, and has several free maps, such as this USGS topographic.

My 19 year-old Icom A4 radio is still going strong. I "hacked" the AA battery pack by adding a pigtail hard wired to the +/-contacts.

I also added a Flightcom IISX intercom, in order to record air-to-air coms on a really old Samsung MP3 player/recorder, when my flying buddies get back in the air with me.

Fuel sender mounted to the upper angled side of my Phantom tank. I drew a 2-5/8" dia. circle on the tank, then used a soldering gun, with a spade tip, to melt-cut the hole (pulsed the gun for 1 - 2 seconds every 2 seconds to prevent burning the polypropylene plastic).

The sender requires three wires to connect it to the fuel gauge... +12v, Gnd, and Signal (0 - 5v full scale). I used a shielded 4-conductor cable (two conductors not used).

This is a 10-06661 Swift fuel sender 18" bendable FMW from AC Spruce for $83. The tiny white jumper wire below the three red LEDs has been cut to put the unit into 5 set-levels mode... empty, 1/4, 1/2, 3/4, and full, which were manually set by pouring 1 gal into the empty tank and setting that as empty, then adding 1.5 gal for each of the next 4 level sets until full calibration of the old shaped tank.

An inside view of the tank from the fill neck so you can see the bent sender tube and supplied 3" dia. mounting plate.

I cut about 5" off the end of the 18" sender tube and bent it about 80 deg, so that the end of the tube is about 1" above the floor of the tank. The 1/8" thick metal mounting ring has a notch on one side to allow it to be inserted through the 2-5/8" dia. hole in the tank. It holds the sender to the tank via five bolts that compress the sender and ring against the tank.

A rubber gasket on the outside supposedly seals the sender, but the mounting method does not seal the bolts, because only 1/4" of the outer edge of the sender body and gasket is compressed against the tank, leaving the bolt holes through the sender body exposed to sloshing fuel.

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