Horizontal stabilizer

Well I think I ignored my homework a bit too much today, but here's another update on the tail.

I figured out a way to get a straight line across an 8-foot tube. I made little idential end plates and strung a string between the plates. By pulling the string really taut, the line that the string created was a non-rotated reference along the span of the tube. All that remained was to mark off the string with Sharpie and pull the tube out of the jig.

My kitchen area hopefully has a flat floor. The linoleum was definitely flatter than my carpet, so that's why I did the work there.



Here is a closeup of one end of my jig. Yes it's cardboard! It's actually a few layers glued together with 3M spray adhesive. I know my cardboard stuff apparently. I made a cool little circular cutting bit out of a spare piece of 1" tube. I used my spiffy new round file to sharpen the ID so the OD of the tube would cut through the cardboard. A bit of pressure and viola, matching end plates! The string shown fits into a little notch that was match-cut into the cardboard, so I know as long as the floor is flat, there isn't twist in the reference line.




The next step was to start working on the trailing edge tube of the horizontal. It had several inserts that had to be made that slide into the main tube. A few rounds of electrical tape space the 7/8" OD inner tube to fit the 1" diameter by 0.035" wall thickness. The center doubler is 10" because it has to capture the rear fuselage mount and the center hinge, which also is the closest to the torque rod that transfers the stick force to the elevator.

You can see two wooden pieces that I cut from scrap to space out the tubes to be 18" chord. It's nice to have a spacing reference while I wait for the carbon rod to show up to make ribs.


Here is another shot of the horizontal stab with the wooden rib spacers and the tube inserts in their appropriate spanwise locations. The leading edge tube has already been riveted into place with the tip tubes previously bent to shape.

I don't think I realize this 8 foot long thing is really as big as it is. My roommate even said the same. My theory is, we've built RC planes with larger wingspan and area than the horizontal stab, so I think we're in denial of the eventual size of the wing!




Here is a real close-up of the innermost doubler tube. The black rounds of tape make a snug fit when sliding the sleeve into the main tube. You may be able to make out my marks for the sleeve alignment. I generally use a marked spare tube of some smaller diameter to push the sleeve down the main tube until it's at the mark. Then I try not to move the main tube much and I drill the first 1/16" hole. After that, the little aluminum chips smear a layer of the tape's adhesive in the hole enough the tube really doesn't want to slide around.




After dinner and some Simpsons, the trailing edge tube is all done up in proper fashion! I installed the three hinge eye-bolts up at 30deg from level. One eye bolt for the horizontal stab tail strut I must have misordered, so I have only one of those installed right now.

I was doing some research while dinner was cooking, using eyebolts for hinges like this does mean that they can potentially rotate and prevent the hinge from operating. I have been brainstorming ways around this. Mostly I have come up with ways to double-up on the eye-bolts or to use a single hinge axis with a long piece of steel rod threaded through all the eye bolts. For now, I'm going to keep moving and keep thinking about it.

I should mention that working with aluminum over carpet is probably not the smartest work environment. I'm keeping things pretty well vacuumed, but geez one day I'm going to step on some shard and walk funny for a while.



This is a close up of the tip joint between the stab and the elevator. The round tip tube spec'd at 30" was about an inch and a half too long, so I used my pipe cutter to trim it a bit. Now the tube fits cleanly into its slot and preserves the 18" chord. The pipe-cutter was only $12 and is a really super quick and precise way to trim the tubing.

I haven't started work on the elevator leading edge (the smaller diameter tube). I guess that's next once I get through some school work tomorrow.






One last shot of the horizontal tail tip showing my collection of tools laying around. This part is too large to fit on my RC building table, so the floor is getting some good use; then I clean up and vacuum.