Pitot wiring

Posted on by Neal

Tonight I finalized the pitot wiring. I have a separate connector at the wing root for pitot heat. Since I had previously planned for a regulated pitot tube, I had three wires run to the pitot tube. With the unregulated model, I don’t need to use the third wire, so I’m leaving it in place as another spare wire.

I unpinned the pitot heat wire from the standard Vans wiring harness and connected it to the separate Pitot heat molex connector, then ran another ground wire from the pitot heat molex connector to the ground point on the fuselage. At the pitot tube end, I installed pins on the wires from the pitot tube, but held off on installing them into the molex connector. I need to wait until I have installed the mast, and the pitot tube, routing the wires through the mast in the process. If I install the connector now, there won’t be enough room to fit the molex connector through the mast.

Anyway, it was a fairly quick job to get this all finalized.

The four connectors at the wing root are a little overkill. The two on the left are standard Vans wiring harness. The third from left is the pitot heat connector, and the right hand connector connects spare wiring that runs to the wingtip.
This is where the pitot mast will attach. The wiring will plug into the molex connector on the right. The Pitot and AOA lines will attach to the white and blue lines respectively.
Feeling pretty good about progress so far.
I went ahead and retrieved the bottom wing skin from storage. This has some history, having been partially attached to a different left wing earlier in the build. I was very careful when I removed it from the original wing, and it’s in great shape.

Pitot tube

Posted on by Neal

Tonight I bent, flared, and fit the Garmin pitot tube. Doing this for the second time (first time was Dynon) was a lot faster, and easier because I could use the Dynon tube bends as a reference.

There are some interesting differences in the Dynon and Garmin pitot tubes. The Dynon is noticeably longer. The tubes are marked “pitot” and “AOA” on the Dynon, but unmarked on the Garmin. I added some heatshrink labels to identify the tubes, after gently blowing through them to confirm which was which.

I’m installing the unregulated Garmin pitot tube, so there’s no controller box needed. The switch on the panel will turn it on, and it’ll stay on until switched off on the panel. This is how it works on most aircraft, and since I’ll hardly ever use it, simple seems best.

Working on the pitot tube
Tubes need to be bent to allow clearance from the aileron pushrod, without contacting the spar
Some thought was required to remember to put the b-nuts on at the right time: after the tube is bent, before the tubes are flared.
The messy touchup paint job on the pitot mast. I could have done a better job, but I’ll worry about it later.

Pitot Mast

Posted on by Neal

I’ve decided to switch back to working on the wings, so I can finish them up and then move them to a hangar. That should give me a little more room in the garage to finish the tail fairing.

It has been a couple of years since I worked on the wings, and a bit of a saga. My original quick build wings were impacted by the Vans primer problem, and I sent them back. But I had already made up the bottom skin for the left wing, including a cutout and holes for pitot mast and reinforcing. I had started riveting the skin on when the vans primer problem was announced. I carefully removed the rivets, and saved the skin. Then I decided to switch from Dynon to Garmin, which meant a new pitot tube. Unfortunately the hole pattern is slightly different and the screws are different sizes between the two. Since the Gretz pitot mast I have is no longer available for sale, I wanted to keep the original mast and bottom skin, and find a way to make it work.

On closer inspection, the holes are in almost exactly the same place. The different is the screw diameter, with Dynon using something like a 3/16 and Garmin a smaller #6-32 screw.

Because the screws carry a sheer load, and because there is plenty of material supporting the screw, I decided to use something JB Weld to fill the void under the screw heads. I coated the pitot tube mount and the screws in boe-lube and then set them into the filler. In the morning the filler had dried, and I backed the screws out, then cleaned up the filler with a file and some sand paper. I painted the filled area with some powder-coat touch up paint. The finish looks rough, but I’ll worry about it when I paint the plane, eventually.