A Pitot Tube and other Small Tasks

Since I was derailed from my plans of mounting the cowl (I needs extensive reshaping, see details here), I decided to work on other things while I wait for the prop extension and seek pre-op education for the cowl surgery. Progress has been slow and I don’t have much to show for the last week and a half. I spent a lot of time on the internet researching and also spent some time buying parts.

I did get some work done on electrical components. I finished my battery box and hold down for the electrical back up battery for the nose gear extension. This will be mounted up in the nose next to the main battery. For that matter, I also fabricated a hold down device for the main battery as well. Both are still partially incomplete as the back up battery box needs to be mounted, and retaining hardware needs to be added to the main battery hold down.

This box and clamp set up will retain the battery for the nose gear electrical back up.
This box and clamp set up will retain the battery for the nose gear electrical back up.
This is how I laid up the main battery retention strap. It will hold the battery in place using piano hinge and a cotter key.
This is how I laid up the main battery retention strap. It will hold the battery in place using piano hinge and a cotter key.

In addition to the battery boxes, I mounted some of the toggle switches in the panel, the ones that I knew where they should be located. These were the switches in the lower right corner. Basically they will be the DC Master Switch, the autopilot power, electric trim power, starter switch, and left and right ignitions. In order to fit them, they were spaced as close together as possible. I am hoping to start some wiring soon. I can’t wait to get something electrical working in the airplane. Even if it is only the click of the master solenoid.

From left to right, DC Power Master, Autopilot Power, Electric Trim Power, Starter Switch, Left Ignition, Right Ignition.
From left to right, DC Power Master, Autopilot Power, Electric Trim Power, Starter Switch, Left Ignition, Right Ignition.

 

 

 

 

 

 

 

 

 

 

Another thing I worked on was making the heated pitot tube. I copied the method used by James Redmon on his Berkut (www.berkut13.com). Basically it consists of a pitot mast nose, main body tube, an inner tube, an end cap, heater element, and a 1/8 inch NPT to plastic tube fitting.

I haven’t used my lathe in a while and had to do some clean up and maintenance first. With that done, It was actually pretty easy to make. I started by drilling a hole thru the center of the bar stock the proper size for a 1/4×28 thread. Then I turned down the nose bullet shape by cutting steps into the diameter of the bar stock. Once I had that, all I did was use a file to get rid of the steps and smooth out the bullet. The other end was then turned down to fit the main body tube. I am pretty proud of how it turned out.

Pitot Tube Nose

The end cap was then machined to fit the inner diameter of the tube. It was also center drilled all the way thru for the 1/4×28 thread. The piece was cut off and since the other end will be a 1/8 NPT fitting, the opposite side of the hole was enlarged for tapping. The holes were tapped.

The next part was a bit tricky. I had to add flats to this piece in order to be able to assemble the pitot tube.  I don’t have a milling machine to do this so I came up with all kind of Roob Goldberg ideas on how to make two flats parallel and to a precise enough size for a wrench to fit on them. What I ended up doing was use a collet block and simply took it over to my 1″ belt sander. Going slowly a little at a time, I was able to get the flats ground precisely enough to be able to fit an 11/16 wrench on them. I was shocked it worked.

The main body tube was simply a tube of 3/4 aluminum and the inner tube was 1/4 inch aluminum that were cut to length. The ends of the inner tube were threaded using a die. I trial assembled and then located a hole for the wires for the heating element. I drilled the hole and test fit the heating element to the assembly. It was really difficult to get the wires to come thru the hole, so I added a second hole adjacent to the first one and filed between them to make a slot. It took a long time to file in such a small hole.

The last part of the assembly was to make a phenolic collar to go around the tube. This will be how the pitot tube mounts to the airplane as well as be an insulator to dissipate the heat. The pitot tube was floxed to the airplane using a jig made of a 2×4 and I used a drill bit to hold the pitot tube.



 

 

 

 

 

Another thing needing attention was the fit of the left front console. The gap between them left side of the fuselage and the console as well as between the throttle and the console was too large. So I hollowed out the foam between the layers of glass about a quarter inch deep. I them taped up the throttle quadrant and side of the fuselage as a mold release. Micro was stuffed between the layers of glass and into the gaps. The end result is much better.

The gaps are acceptable now.
The gaps are acceptable now.

 

 

 

 

 

 

 

 

 

 

 

Since I was in the finishing mode, I also got started on finishing the canard airfoils. They are the only part of the airplane that are ready for finishing. So I prep sanded, slathered on micro, and got out the blocking tools. This is the result of about 3 or 4 hours of sanding, and I am happy to report that the contour checking templates are fitting to about 1/32 of an inch. I do have some areas to repair, and there is still a considerable amount of micro to take off on the left side, but I am well on my way for the top surface.

You can see some areas where I had air bubbles in the micro that need to be filled. I also got a bit aggressive in some areas that will need to be re-filled.
You can see some areas where I had air bubbles in the micro that need to be filled. I also got a bit aggressive in some areas that will need to be re-filled.
It is a bit hard to see, but the gaps here are about 1/32 of an inch.
It is a bit hard to see, but the gaps here are about 1/32 of an inch.

 

 

 

 

 

 

 

 

 

 

 

 

 

I did get a few more things done in the past few days, but we will save that for another post.

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