Hatz Biplane Association

I was figuring out the position of the aileron stops for the torque tube and realized that rod end bearing (Aurora XAM-4) puts a limit on how much the torque tube can rotate. The misalignment angle for the rod end bearing is 13 degrees from the Aurora specifications. There are two rod ends, One at the torque tube and one at the elevator linkage idler. That means that the max rotation the elevator linkage rod ends will allow is about 26 (2 x 13) degrees. The torque tube needs to rotate 60 degrees to move the ailerons from 25 degrees up to 15 degrees down. The rod end bearings limit the aileron up deflection to about 12.5 degrees and the down deflection to about 10.5 degrees. This is pretty much what Eddy found when he measured the angle from 2.5 inches up and 2.0 inches down shown on the plans.

So it looks like the limitation is the 2.5 and 2.0 inches up and down. If the aileron stops don't limit the rotation of the torque tube, the elevator linkage rod end bearings could be unscrewed from the linkage tube or damaged. The Makelan CD does have a picture of the aileron stops in the aileron linkage folder.

I guess the question; is 12.4 up and 10.4 degrees down enough travel for the ailerons? They are big ailerons and there are four.

[attachment=0]Aileron Details RV Style-Small.png[/attachment]

I was doing the calculations on the aileron travel and discovered the "secret" formula that Ebby was looking for. The amount of travel depends on where the bell crank is in the arc. See sketch below. The basic formula is the sine of the angle but it gets complicated because there is the bell crank arc and the aileron arc.

I used the aileron linkage lengths from the plans and put the aileron idler at the neutral position. To get 25 degrees of aileron up (1 9/16" of linkage travel) the bell crank swings about 30 degrees. On the opposite wing, 30 degrees of bell crank travel only moves the aileron linkage 1 1/16". That calculates out to about 15 degrees aileron down.

As Ebby discovered, if you want to change the aileron differential, just change the bell crank neutral position in the arc. Moving the bell crank closer to the top of the arc increases the differential. If the bell crank is at 90 degrees to the aileron linkage at the neutral position there would be no differential. The up movement would equal the down movement. The problem is the spar is in the way for this to happen. You want some differential though to counteract the adverse yaw.

To get the 25/20 degree differential shown on the plans, turn the bell crank neutral position about 10 degrees clockwise from where I show it.

Something interesting is that at full up deflection, the opposite aileron on a Tiger Moth is in the neutral position. It does move, but it goes across the top of the arc so it end up back in the neutral position at full deflection.

The question I have is, what should the differential be? 25/15 from the aileron linkage lengths given or 25/20 as shown on the plans?

[attachment=1]Aileron Bell Crank Details 2.png[/attachment]

[attachment=0]Aileron Details.png[/attachment]

Hi Ebby,
I covered my wings with the Stewart system. I did use the batting on the leading edges, held in place with spray contact cement per their instructions. The process uses lots of cement!!! I wish I tried the roller, brushing was a bit of a pain.
Al

I followed Mike's rigging suggestion and observed I had 24.6 degrees up aileron and 17.9 degrees down aileron without any stop adjustments. These measurements are close to the 25/20 listed in the plans and I infer these are the limits of aileron movement and not necessarily the "flying specifications". Using the stops I can adjust the throws to nearly any value within the previously mentioned upper and lower limits. Taking Mike's flying advice I will adjust my starting "flying specifications" to 2.5" up and 2.0" down.

Using the electronic protractor, with my ailerons having a 12.25" top skin, 2.5" up at the trailing edge gave a reading of 11.9 degrees and 2.0" down gave a reading of 9.6 degrees. YMMV

In the Stewart video, it is mentioned that the felt can be purchased at my local craft store. After visiting, WalMart, Hobby Lobby and Michael's I couldn't bring myself to purchase any of their offerings for felt. Returning home I placed an order with ACS for polyester batting.

I am using the Stewart system and will follow the instructions given in the video which sound very similar to the polyfiber method. I communicated with Jason at Stewart and he recommenced using foam roller to apply the Ekobond rather than a brush to minimize disturbing the polyester structure. A big difference in the two methods is in the Stewart video they apply two coats of Ekobond to the felt before covering and it sounds like the Polyfiber method only attaches the fabric to the rear of the forward spar. My leading edges are wood. By not filling the pores of the batting am I setting up a situation where condensation will settle in the batting causing rot?

All of this advice is great as my gut feeling is I am getting close to the end of this build.

The leading edge batting also keeps the fabric smooth when your leading edges expand and contract due to heat. Works especially well where aluminum sections overlap. Without it, the fabric will sometimes gather and wrinkle from the underlying movement.

Polyfiber makes a polyester bat for this purpose. I used it. This is a very common practice with Stearman restorers. It does all that you stated. All imperfections are hidden under the bat and makes a nice cushioned leading edge..

Installation notes for Polyfiber system

1. Do not over stretch the bat. Just lay it in place. When you shrink the fabric the bat will be compressed.
2. Let the bat wrap to the inside of the spar.
3. Glue the bat to the back of the spar (only to the back) with Polytac
4. Do not flood the fabric with the first coat of Polybrush
You want to keep from saturating the bat. If you do soak the bat, You will end up with hard spots.

5. Once the fabric is sealed with the first coat - your good to go.

I have also used this on several Stearman wings and would not do a wing without it.

As far as aileron deflections. As said before, I have 2" and 2 1/2". While flying and observing the aileron movement in very steep turns, little aileron movement is required. Having flown Stearmans, I am very impressed on how responsive the Hatz is in roll. I do have upper and lower ailerons. Which I think makes a big difference.

Michael
N9648B

I'll be rigging this weekend and will do a comparison of angular and linear measures for the throws. One of my first attempts was fixing a vertical stick just aft of the aileron trailing edge with the aileron at neutral (0 degrees). Then I placed a mark 2.5" above neutral and 2.0" below neutral and moved the stick to see what that looked like. It didn't look like much of a deflection in either direction. I certainly am not saying that its wrong because the plans do reference those measurements and I haven't seen any Classic owners show me first person how much their ailerons deflect. To me it just didn't look like enough. I didn't have my electronic protractor at the time so I couldn't get an angular measurement. I will have a better fix on the comparison this Saturday.

I don't know how much of a difference this will make but I have ailerons on the bottom wings only and extended them to the wing tip. My theory was if I only had lower wing ailerons, I would have a more docile roll.

On another note, I saw in the Stewart Systems video the use of felt applied to the leading edge of the Piper wing and was wondering if anyone building a Hatz used felt on their leading edges. From what I gather, the intent of using felt is to mitigate imperfections and provide a measure of protection from bumps and bruises. Thoughts?

Hi Folks,
Thanks for the input, will make use of this when assembling the aileron set up.
One thought about the aliminum ailerons: In fact, for us this has been the biggest challenge in the hole building of our Vintage Hatz have been the ailerons. The problem is finding the correct shape for the skins near the tip in order that it naturally blends into the wing tip bow. We assembled the ailerons attached to the wing and glued a sandwich with both top and bottom skins and a wood triangle. We used a slow curing elastic 2 komp. sealer because we feared that a rigid epoxy would fail in shear when torsion is applied. The aileron trailing edge we supported by attaching a straight lumber to the wing trailing edge and used a lot of spring clamps. This is not an easy task because the clamps tend to slip away from the triangle shaped trailing edge.

Not all 4 ailerons came out exactly the same and for a future project we would build a jig for this task for the goal to achieve a perfect shape. The big problem is that the aileron hinge line comes as far toward the tip as about 2 to 3" . Therefore a wooden aileron with some separate hinges can be built much easier.

At last, of course, it's a personal taste, but our aim has been to build the wings to look like on a Waco QCF....

We wish all Hatzers and their honeys a Merry Christmas and a happy New Year!

Hans & Sam, H.C.#78, Switzerland

Some where in the plans the 25 - 20 degrees is stated at 2" and 2 1/2". I do not know if this (2 - 2 1/2" converts to 20 - 25 degrees)? But these numbers worked well for me. I know on the ailerons, I also pressed my own skin and it was a hard choice to trash them. But some one just starting might investigate this. I made the switch after seeing John Hanson's plane at OSH (he has fabric ailerons)

Michael
N9648B

I'll give your method a try and see how the deflection angles match the plans. To me 25 up and 20 down seems high. As far as the aluminum ailerons go I've got too much time invested in pressing my own skins and fabricating to change horses in mid stream and build wood and fabric replacements.

Thanks much for your rigging recommendation.