I've been practising the positive Humpty Bump in my Skybolt, but I am not sure if I am "pulling" at the correct speed at the top of my vertical upline. I've been pulling at 60 mph, which of course is much faster than the hammerhead pivot. Also, how hard is the top pull? I'm not getting a float on top --- should I be floating as in a loop? Any advice greatly appreciated!
Thanks,
Cary Rodin
Victoria, B.C.

• RE: Humpty Bump technique,TomParsons, 15:09z, 09-30-02
  • RE: Humpty Bump technique,CRodin, 15:57z, 09-30-02
    • RE: Humpty Bump technique,TomParsons, 14:19z, 10-01-02
      • RE: Humpty Bump technique,TomParsons, 17:26z, 10-11-02
• RE: Humpty Bump technique,aboyd, 03:43z, 10-13-02
  • RE: Humpty Bump technique,CRodin, 14:37z, 10-20-02
    • RE: Humpty Bump technique,aboyd, 01:41z, 10-22-02
      • RE: Humpty Bump technique,TomParsons, 15:11z, 10-22-02
• RE: Humpty Bump technique,RickB, 18:58z, 10-17-02

Getting ready for next year's Sportsman sequence? I'm curious to hear what the experts say about this, too. I would think that you'd have to have a little float, otherwise you'd be pinching the half-loop (non-constant radius), right?

Tom P.

You're Right Tom,
I am starting to work on next year's Sportsman! I only flew one contest this summer and while I will probably fly Sportsman again next year I'll also try the Intermediate sequence over the winter, too. How about you?
I agree that there should probably be some float on the humpty bump... but it doesn't "feel" like I'm getting much. I'll experiment with different airspeeds over the top and report back!
Thanks for the input,
Cary Rodin
Victoria, B.C.

I have not flown in any contests yet. In fact, I have been to just one contest, as a volunteer. I've been trying since late spring to buy an airplane without getting saddled with a piece of junk, and I am this close to making a deal on an S-1S. It's anybody guess which will happen first- I buy the airplane, or my head explodes from exasperation.

If somebody made me go learn how to do a humpty without asking any questions, I would start by flying some loops and noting the airspeed and Gs at the 90 degree point of the loop. That would be my starting place for airspeed and pull for the half-loop part of the humpty. I'm curious to hear your report on what you found worked best, compared to the numbers at the 1/4 point of a loop, in your Skybolt.

Tom P.

Cary-
>I would start by flying some loops
>and noting the airspeed and Gs at the 90 degree point of
>the loop. That would be my starting place for airspeed
>and pull for the half-loop part of the humpty.

I just re-read this, and I now realize that I am stupid. Yup, one clue short of having a clue. One beer short of a six-pack, one candle short of a chandelier, etc.

My silly answer doesn't work, because you have to draw a line before the half-loop, and you slow down on the way up. Duh. Even if you started faster than normal loop entry speed, I don't know if the difference would matter much. So just forget what I said.

Tom P.

P.S. Thanks for the good wishes on my airplane!

Anyone thinking about competing should get a copy of the IAC "red book" which is the rule book for contest flying.

In the judging criteria, it says that for a humpty, the length of the vertical and the radius of the half-loop at the top are NOT relevant.

As long as there is a vertical established both up and down, and if you've got a constant radius, it's a "10".

Sure, a longer vertical and smaller radius might look cooler, but don't start there.

Most people slow down way too much before the pull or push. All you have to do is clearly establish a vertical upline - to avoid a judge's conference and a zero - and it's a humpty!

If you can fly a round loop, you can fly a constant radius humpty. It can help to use a slightly higher entry speed.

When they're starting out, most people tend to find the pull humpty easier than a push humpty. The negative G is so light in the push humpty, I don't think it's really very relevant to the difficulty. I have a theory, though.

Think about what's happening with the propeller as you slow down, in a pull humpty with a lycoming: the gyroscopic precession caused by the pull will naturally cause a yaw to the right. However, the effect of the slipstream contracting is that it will strike the left hand side of the vertical fin and rudder, tending to yaw you left. They cancel each other out. This is nice.

Now think about push humpty: the push will cause a yaw to the left (with a lycoming) and so will the slipstream. Oops. You may find yourself running out of right rudder in these circumstances. This is clearly seen during an outside loop, for example.

So, avoid the problems caused by the propeller at slow speed and high power. Keep the speed up in the humpty.

You will learn all about the effects of gyroscopic precession, slipstream, torque in other maneuvers such as the hammerhead.

Hope this helps,

--
aboyd@igs.net ATP
http://www.webhost-canada.com/~boyd/team.htm

You're right, ABoyd.... I had to use a lot of right rudder on the push humpty. I also needed a little left rudder on the pull humpty. Thanks for your explanation re: gyroscopic precession and slipstream effect. It really helps to visualize the forces at play. By the way, didn't you contribute a couple of aerobatic articles to COPA Flight magazine? Any more articles on the way? I enjoyed your contributions. There certainly isn't much written about aerobatics beyond Sport Aerobatics.
Thanks again for your help!
Cary Rodin
Victoria, B.C.

I should mention that you might consider gap seals on your elevator and rudder. They can help a lot in improving your flight control authority, especially when doing outside stuff, because they stop the high pressure air "leaking" past the gap between the fixed and movable parts, and instead it pushes where you want it to.

Gap seals are really simple and cheap to make, for a homebuilt anyways. 3M bookbinding tape is really good, but even cheap packing tape will work for a flight or two before it tears off.

Measure what you want to gap seal, from the hinge. Cut a piece of tape a couple inches longer than you want, and fold one third of it over lengthwise. Then, cut the piece of tape to precisely the length you want, and stick it on the forward, fixed horizontal stabilizer or vertical fin. The folded-over part goes at the rear, and doesn't stick to the movable flight control. For best performance, gap seal both sides.

I think you'll be impressed at the improvement, especially when you consider the bang for the buck!

On the single-seat Pitts, gap seal the ailerons, too. I personally don't think it's worthwhile on the two-seat Pitts with the symmetrical ailerons - you can hardly notice the difference in roll - but it doesn't cost very much to try.

>I should mention that you might consider gap seals on your
>elevator and rudder.
>...
>On the single-seat Pitts, gap seal the ailerons, too.
My airplane has gap seals on the rudder and elevator, but the home-made aileron gap seals have been removed. The seller told me about his method, which involves sticking the seal to both the fixed and movable sides of the gap. But your method, where the trailing edge is free-floating, sounds cleaner. Does this method work on the (in my case) larger aileron gaps?

Tom P.

I had one of our instructors watch me from the ground as I flew the sportsman sequence. I also used to try and "float" over the top of the loop and humpty, but he said my loops weren't round.

He had me pull hard and maintain my pull over the top and said the loops look good that way.

Since I'm flying a high drag Great Lakes bi-plane, perhaps the higher g's prevent me from losing too much speed during the vertical.

Rick