Hatz Biplane Association

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 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?

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.