Wings – Structure

Wings 39 (4.0 hrs)

This entry was posted in Wings Wings - Structure on by

A couple of projects for today’s shop session. My buddy Jimmy gave me his motorcycle lift which I plan to use to support the center of the fuselage. Yes, its probably overkill. This thing will be supported with weight in it at only 3 points, but until that time I want as little risk to the structure as possible. This will allow me to support the middle easily at any orientation. I began by doing a full test of the rotisserie and rotating the fuselage completely upside down.

Next I measured the highest and lowest points.    

With the measurements in hand, I made a makeshift support. I will readdress later. Likely with a highly specialized milk crate. 

I also stopped at Lowe’s and picked up to extension bit holders for drilling out the middle two ribs under the wing walk doublers.     

The snap bushings supplied by Van’s are from Heyco and have an inner diameter of 0.27″. The tubing for the pitot and that AOA tube are 0.25″. I didn’t like the extra play so I ordered Heyco snap bushings (SB 432-243) with 0.24″ ID. I was worried they’d be too small, but it turns out they are an absolutely perfect fit.   

Next I ran the pitot & AOA tubing. Mike Bullock had needed to order some additional tubing for his AOA home-brew so I jumped on the order and ordered 100 feet of the green tubing. The blue tubing is left over from Mike. In the end, I”ll be able to sell all my extra tubing on VAF and save a bunch over using SafeAir1.   

The next problem I faced was determining how to route the lines around the bell crank. I came up with two options. The first option, shown below, routes the tubes around the outside of the bell crank. The one thing I don’t like is how severe the angle is on the green line (shown with arrow). Yes, it will probably be fine for 2000 hours, but I can do better.     

The second option was to route the lines under the bell crank as shown here.  

What I wasn’t sure of though, was how far down the bell crank will go. On the plans, using Van’s AOA, it stipulates leaving 5/8 of an inch. That being the case this should work. But again, I don’t like should. I did a lot of messing about here including mounting the aileron and playing with the position of everything.

That was as far as I got today. When I want to put my wings back into their corner, I realized that the ailerons will hit the rudder. I’ll have to flip the horizontal stab.    

Squire enjoyed sunbathing. It was a gorgeous day at the airport.   

Multiple Sessions (12.0 hrs)

This entry was posted in Fuel Tanks Fuselage Plans Wings Wings - Structure on by

This post encompasses several projects over three sessions in the hangar. First up I needed to figure out a way to mount the tail of the fuselage to my rotisserie stand. The axis of rotation is offset from the center of the tail. There are a couple of options for how to mount. I decided to make a padded cradle for the tail. I wrapped a cotton towel around the tail with duct tape. Then I clamped some 2x4s around very tightly to get accurate measurements. A short while later I produced this: 

I didn’t take a good picture of the front mount in my previous session, so here is that. 

And here is the final product for the tail mount. You can see how the center of rotation is offset and how I padded the tail in the cradle. The entire stand is sturdy, but it still makes me nervous. Especially while in the rotated position, its hard to tell how much of a torquing moment may be applied to the engine mount connections or any part of the frame. To protect against any mishaps I will continue to use the adjustable saw horses underneath. Additionally, I have a friend who is giving me an adjustable motorcycle stand. I am going to use that to create a center support that can be adjusted for any position near the center of gravity.

  

Here is the Hangar 51 mascot showing off his handywork.

That’s not a blue bow. Its poop bags. Keeping it classy.   

Next up, it was time to attach and torque the non-leaking tank to the wing. The screws get between 12 and 15 inch pounds of torque. I used torque seal to mark the bolts that were attached to the z-brackets.     

A trick I learned a little while ago that is seriously awesome; use a small dab of valve grinding compound on the tip of a your philips head screwdriver to avoid “caming” out of the screw head. Works wonderfully.   

I borrowed Mike Bullock’s screw driver click type torque wrench thing-a-majig. Works well.

I double checked that it work with my inch-pound bicycle torque wrench and a philips socket.

  

Squire enjoyed sunbathing. It was a gorgeous Sunday. 

I also drilled the second line that will hold either the AOA line or the pitot line. I still have two ribs remaining. The two interior ribs to the wing walk doubler are rather difficult to get at. I stopped at Lowe’s on the way home and hopefully I have a solution.    

My final project for the weekend was to complete the wing access panels. First I mounted the skins on the wings and match drilled. Then I deburred and dimpled.  Then I used a technique that I only just learned. Instead of using standard AN426AD3-3.5 rivets which require dimpling both the skin and the nut plate I used NAS1097 Oops rivets with the reduced sized machine heads. These only require a small countersink that you can do with your demurring tool in a few extra passes. Not only is it much quicker, but I think it results in a cleaner and more properly aligned product. There is no reduction in strength either. The nut plates bear the load… the rivets just hold the nut plates in place to prevent rotation.

You can see the results here:

And the final products.   

Wings 38 (5.0 hrs)

This entry was posted in Wings Wings - Structure on by

When I arrived at the airport today I saw a T-34 sitting on the line. From afar, I didn’t take much notice. There are plenty of T-34Bs around, but as I got closer I realized this was a T-34C, in which I have about a 120 hours from my military days. Unlike the T-34B, the T-34C is not available as a civilian aircraft so this must be from a Navy unit… most like Pax River. The turbo mentor used to be the aircraft used at NAS Whiting Field, and NAS Corpus Christi for primary flight training, but it has been replaced by the new T-6. Fleet military units still use it for aerial spotting and other misc tasks. Its way cheaper to fly and maintain than other fleet aircraft. Odd to see one at KDMW though. I didn’t investigate further… I have my own airplane to build… 

Back to my airplane. I have to determine how I’m going to run my pitot lines. I will definitely be doing a heated pitot tube with AOA, so really I have three runs to do. Wiring for the heat, AOA pressure, and pitot pressure. Currently I have the wire run and the pitot, but I’ll need a third spot for the AOA run. In the picture below from left to right you can see where I plan to run conduit for the wiring, and the pitot run. The tooling hole on the right will be used for AOA.   

My primary task for today was to dimple all the bottom skins.   

After dimpling, I attached the skins so that I could match drill the flap brace.    

I began, but didn’t finish, countersinking the flap brace. There are no instructions what to do here, but the best option is to countersink the middle piece so that the soft hinge material needs no dimple or countersink.   

Finally I cut the wing side of the hinges to length.