It's been raining all spring here in the Northeast, so I'm spending way too much time fussing over an ancient Goldberg Eagle trainer in the shop. I was checking the wing for warps and washout when I decided to check the wing-tail rigging angle.

Much to my surprise the tail came out 2-1/2 degrees positive compared to the wing mount platform. A lifting tail? I checked the plans and sure enough, the designer put the LE of the tail several degrees up compared to the wing's flat bottom.

Aero theory can give you a headache, but I always thought tails should lever downward to balance a CG well ahead of the center of lift. Pitch stability is a good thing in a trainer, especially the way I fly.

Anyone have any idea why Goldberg would have angled the tail up that way?

- Balsacutter

Well you should be so lucky to have me find your question. I have had an Eagle for some time
now, and after several bad crashes learned a lot about incidence. My first rebuild of the
aft section of the plane gave me a serious porpoising plane at once on takeoff. Had a difficult time in flight, and scary landing in one piece. My new Robart Incidence meter showed once the
longitudinal axis was level that I had a + 1/2 degree on the wing, and a +3 degrees on the horizontal stab. So in flight, the horizontal stab was driving the wing into a negative angle, and
that is why I had to give such a large amount of up elevator on the takeoff roll. Ok, to the fix. I
remove the horizontal stab assembly, and made a wedge shaped platform for it to sit on. Had to
keep changing the wedge angle until the stab was at '0" degrees as shown on my construction
plans. Glued everything back together, and the plane flew like a ***** cat. Since that crash, I
had another serious crash which entailed a complete aft fuse rebuild from the rear dowel pin
to the tail. Went through the whole same process of incidence angles again, and have made
two flights on the plane with no control problems at all except the new TT .42 after break-in has
cause both flights to end in dead stick not on the runway with no damage from landing in
tall grass. My Eagle 63 is an earlier version of the Eagle 2 so my plans may be different from
yours. I used a long steel ruler to find the longitudinal axis from the horizontal stab to the
center of the engine c/s. Right now I am rebuilding a crashed trainer given to me, and just
did the incidence check. Both wing and horizontal are at a +1 degree. It will be a wait and
see situation when this model is on the takeoff roll, and breaks ground as to whether these
reading will be good or bad. Since they are both the same, I think the plane will fly ok. Any-
way, hope I have said something here that is helpful. Get back as I would like to know how
your plane flew after you have made any changes.

Rich S.

OK, your measurements on the stock plane were the same as mine, 2-1/2 degrees postive difference between tailplane and the wing. If I understand you correctly, you took the positive tailplane angle out with the mounting wedge, and you liked it better?

Mine seems to fly OK, with no fussy pitch sensitivity. Although it does take a lot of speed and up elevator to get it unstuck on takeoff as you say.

CG is right on the spar. Maybe Goldberg knows something about the funky airfoil (very small LE radius, entry point way down low right on the flatbottom line) that required a lifting tail to balance... With these popular, high-volume production products you gotta assume they had time to think this stuff though and fix what didn't work right.

I'm just trying to understand it...

- Balsacutter