Pitot Mast

Time: 5 Hours

Today’s task was to install or temporally install the SafeAir pitot mast. This will eventually hold the pitot tube for my airspeed indication. I plan on using a Dynon heated pitot tube that has a AOA capability built in. There is no reason to buy that now as I can’t drill it until the wings are on and I get the plane into a level flight position as you need to adjust the pitot to be level with that attitude. But I can install the mast now so that was the plan. I went over to my friends to take a loom at his and make sure my plans were valid on where I needed to mount it. From there it’s easy as they give you a template to use. First was to cut the template out and make some reference lines on the skin from the edge of the main spar.

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20140605-142603-51963862.jpgI then aligned the template on the skin after I applied some blue tape to protect the skin.

20140605-142936-52176167.jpgI then used the template and traced the inside of the cutout. After removing the template I used my unibit to drill a hole at each end that was close to the radius of the ends. I then removed the blue tape and replaced the template to use as a guide for cleaning up the edges close to the outline.

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20140605-172523-62723579.jpgI used my Dremal to do the work using various bits, the best being a 1/4″ drum sandpaper bit. I would work a little and then place the mast under the skin to see where I needed to remove material. As I got close I switched to using my hands and some 180 grit sandpaper. I’m real happy with the fit and I have a pretty even gap around the whole mast.

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20140605-172826-62906431.jpgI then checko’ed the skin back on the wing and slid the mast into position. I used my deep reach vise grips to clamp the mast into position. Once I was happy I had it just right I used my 12″ drill bit to match drill the three holes along the spar. I then slid the template back over the mast and used the two marks to drill the aft holes for the mast. I just want through the skin and marked the mast. I then removed everything and finished the drilling on my workbench.

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20140605-173255-63175533.jpgI had to countersink the two aft holes in the mast to accept the dimples from the skin.

20140605-173406-63246209.jpgAfter getting that done I decided to mix up a little ProSeal to put on the inboard and outboard end of the electrical conduit. This is just to make sure it never moves. I just used a popsicle stick and smeared it around the tube along the inside edge of the two ribs.

20140605-173651-63411995.jpgBefore putting the skin back on I wanted to work out how the pitot/AOA tubes run through the bell crank. I have seen several different ideas using clamps or zip ties. I decided to make an angle bracket the would tie to the two outboard bolts of the bell crank in which I could put two snap bushings in to hold the tubes. This is what I came up with and how it looks installed.

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20140605-174901-64141978.jpgWith those items done I only have one task left to do and that’s to rivet the outboard bottom skins. That will be my goal for the next 3 days.

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