Today I finished riveting the the inboard bottom skins. I also did some bench testing of the heated pitot tube. The guidance from Garmin is to not trim the aluminum tubing coming out. Other vendors recommend trimming to no shorter then 6". However I need to trim the tubing down to about 5" for good clearance from the aileron push tube. The reasoning behind the guidance from the vendors is that if your going to transition from the aluminum tubing to nylon tubing (which I am) you want sufficient tubing length to absorb the heat from the pitot tube. I guess the concern is that the first several inches of tubing could get hot enough to melt the nylon tubing. Some guys on the VansAirfoce forums mentioned they bench tested their units and never found the tubing to get very warm. So I decided to run my own test, since my plan was to trim the tubing down to about 4.5" - 5" and then transition to a 90 degree elbow with a push-to-connect adapter for nylon tubing. So I ran the bench test for an hour. The pitot tube itself get’s pretty hot, around 80C (175F). The aluminum tubing only get’s slightly warmer then ambient temperature though, even the first couple of inches. So I concur with the opinion of the builder community that trimming the tubing down shouldn’t pose a problem. Most of the heat is concentrated at the top of the pitot.
Bottom inboard skins riveted on
Bench testing the heated pitot tube
Trimmed the tubing and installed the push-to-connect elbows
