Pitot tubes

[Jch]

I would like a different pitot tube than the KF tube. I am considering the Aerogizmo tube, but I don't know how to position it or where to get the information to do so. Anyone familiar with how to position a pitot tube?

[Dave S]

Jeff,

Going to a different type of Pitot tube gets into an area of experimentation.

If a person uses the location of the original design for the pick-up point, that should be a pretty good starting point. See where your original tube puts the open end where it would be installed.

What you are trying to do in locating the Pitot Tube is put the open end in the airstream where it will be minimally affected by flow over/under the wing/struts and off the prop.

Installation advice from the Pitot Tube Manufacture (if it is available) should be considered. There may be other differences than simply location.

Dave S
KF7 Trigear - Flying
912ULS Warp Drive
St Paul, MN

[jrevens]

I think this may be covering old ground, but I'm grateful that this subject was brought up now. I'm wondering if anyone has relocated their pitot tube further inboard, to the area inside of the lift strut attach point, and if the change was successful. I'm just thinking about minimizing potential damage from people at fly-ins, etc. It seems as though it would still be outside of prop-wash effects, and the lift struts might not create undesirable effects because of being well behind the pitot inlet. Has there been any experience with this?

[Dave S]

John,

Your thoughts about minimizing the potential earthling damage on the pitot tube is interesting....I thought about that a bit...it is in a real vulnerable position...so far I have been lucky.

However, I did make some changes in the original installation with the idea of at least minimizing the potential for damage to the stuff inside the wing.

Did two things.

1) Fabricated some reinforcing ending with an exterior tab as shown in the attached photo to provide some additional strength at the base. The tab sticks through the fabric and matches with a tab on the Pitot tube so the two parts are fastened together with small screws and hopefully if the pitot tube gets whanged....the pitot tube only and not the mounting and stuff inside the wing gets damaged.

2) Fabricated a pitot tube out of malleable copper tubing instead of the somewhat more rigid aluminum tube that came with the kit. The idea here is that the copper tube is soft enough to bend rather than break to prevent transfer of the force to stuff within the wing which may wreck something harder to fix. The copper pitot tube has a tab soldered to the base where the flange is matched up with the tab on the wing behind the fitting.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp Drive
St Paul, MN

[DesertFox4]

I'm wondering if anyone has relocated their pitot tube further inboard, to the area inside of the lift strut attach point, and if the change was successful. I'm just thinking about minimizing potential damage from people at fly-ins, etc. It seems as though it would still be outside of prop-wash effects, and the lift struts might not create undesirable effects because of being well behind the pitot inlet. Has there been any experience with this?

John- 10 years ago when I built my model 4, I moved the pitot tube inboard one bay so it would not be at risk every time someone, including me, walked under my left wing. It is kind of hard to see in this photo I found on my computer. It's location surprisingly suffered no affects from the lift strut
and is still out of the prop wash area. It is very accurate and has never been damaged. The struts protect it from pedestrians, hats, ect. The attached photo is a little misleading due to the angle taken. I'll try to get better photos next time I'm at the hangar and maybe take some measurements of its exact location.

100_3154.jpg

[jrevens]

Thanks to both Dave S and DesertFox4... that is exactly what I was looking for! You guys are great, and I appreciate it very much!

[DesertFox4]

More photos of the relocated pitot tube.
Pitot tube opening sits 1" below edge of strut fairing and works
perfectly.
pitot tube kitfo 012.jpg
pitot tube kitfo 008.jpg

pitot tube kitfo 018.jpg

pitot tube kitfo 017.jpg
Photo below shows pitot tube located 15.5" back from leading edge of wing.
pitot tube kitfo 011.jpg

pitot tube kitfo 010.jpg

[jrevens]

When routing the line, has anyone run their tube outside of the rear spar, instead of going all the way out to the wingtip, then back inside the spar tube (on a mod. 7)? If so, how did that work out where the tube enters the cockpit? Did you go in front or back of the spar tube?

Also, I've heard that builders (Mod. IV) used to drill a hole in the spar for the tube to enter, somewhere closer to the pitot location. Was that approved by the factory?

[Geowitz]

Also, I've heard that builders (Mod. IV) used to drill a hole in the spar for the tube to enter, somewhere closer to the pitot location. Was that approved by the factory?

That's the way mine is and it's in my 94' build manual that way.

[Dave S]

John,

My series 7 build manual included instructions to drill a hole in the rear spar.

I couldn't bring myself to drill a hole in the spar. I routed the tubing through the bays ahead of the rear spar, then around the rib adjacent to the fuel tank. Thereafter running it in the small space between the front of the rear spar and bottom rear edge of the fuel tank. The tubing comes out in front of the rear spar through the web of the first spar. This way no holes had to be drilled through eiher the spar or any ribs.

The attached photo shows some; but not all of the routing.

DISCALIMER AND WARNING - THE ZIP TIES YOU SEE N THE PHOTO SECURING THE TUBING TO THE REAR SPAR WERE A TEMPORARY MEASURE TO HOLD THE TUBING. ZIP TIES WERE REMOVED AND THE TUBING PULLED STRAIGHT. ZIP TIES WILL WEAR INTO THE ALUMINUM SPARS.

I also did a final securememt of the tubing by tacking it down to the ribs and the rear spar/fuel tank with some of the adhesive used for gluing the fuel tank in.

If I were re-doing it now I would probably loop the tubing back and secure it to one of the false rib stringers.

Sincerely,

Dave S
KF7 Trigear - flying
912ULS warp