Roll Trim

[Dave Clifford]

Has anyone come up with a better idea for the plans built roll trim mechanism or know of a source for an electric roll trim similiar to the Alex Strong electric pitch trim system? It would be nice to be able to trim both roll and pitch electrically with a coolie hat switch on the stick. Just finished building the per-plans parts and figure there's got to be something else out there.

[Marc Zeitlin]

Originally posted by clifford

Has anyone come up with a better idea for the plans built roll trim mechanism or know of a source for an electric roll trim similiar to the Alex Strong electric pitch trim system?

Well, if you were on the "old farts" (as Mr. Slade calls them) canard-aviators list, you'd have long ago been exposed to the "Wright-Hanka" roll trim system. Go to the mailing list website and click on "files". It's down near the bottom. Simple and nice, if you believe you need electric roll trim.

[Dave Clifford]

Marc,

I am on the "old Farts" canard aviator list but for some reason I can not post messages or questions any longer. Are you saying its not necessary for roll trim or just a neat electric system instead of a lever.????

[Marc Zeitlin]

Can't help you with the access - I'd check with the administrators.

 

With respect to the roll trim, I find that I trim for climb, then once for "n" hours of cruise, then once in the pattern. If I burn all the fuel in one tank before switching, I'll trim then, too. None of this is difficult to deal with even if trimmed completely in the wrong direction, and if the Navaid is on, I'll never know I'm out of trim.

 

If I were going to install an electric roll trim, the Wright-Hanka system is what I'd use, but I've decided it's not worth the effort at this point. Maybe if I had come across it while I was still building....

[FloridaFlyer]

Marc, just thought I would give you my 2 cents worth... I have not built any airplanes but have been lurking here for a couple of months. I have no idea of the extent of your flying experience and am not trying to insult you. My flying background includes C150/152, C172/172XP, PA140/180, Citabria, Piper Cub, T34C, KingAir 90, P-3 Orion (Electra), 737-200/-300/-500/-700. Out of all of these airplanes, only the 737 has electric roll trim. It is usually set on the ground and not touched the entire flight. Occasionally, you may make a fine adjustment in flight.

 

Electric pitch trim makes sense to me because pitch trim changes with power/airspeed. Roll and yaw trim don't require that many changes. If I were building an airplane, I would not even consider adding electric motors anywhere that I don't have to. Not only does it add extra weight and complexity, it is also an additional source of fire. The only exception that I'll make to this is that when I build an airplane, it will likely include a two-axis autopilot which will of course require pitch/roll servos.

 

I just thought of this as I was writing this post. Does a pusher exhibit P-factor induced yaw like a tractor configuration? I would think it is at least significantly reduced.

[Jon Matcho]

I just noticed an unanswered question...

 

Does a pusher exhibit P-factor induced yaw like a tractor configuration? I would think it is at least significantly reduced.

I'm only a student, have not piloted a canard or any plane for any length of time for that matter, but what I know from my research is that canards can exhibit P-factor as much as any other plane, particularly when in a high angle of attack as in the case of a rapid climb.

 

Spiral propwash, on the other hand, does not happen with a canard/pusher aircraft.

 

Sometimes it takes upwards of 2 years to be able to answer some questions.

[Wayne Hicks]

Here's an example of an electric roll trim system in use on a few canards:

http://www.maddyhome.com/canardpages/pages/waynehicks/chapter_17_1.htm

 

But as Marc said, you don't really use the roll trim too much during a flight. More or less set it and forget it.

[Jon Matcho]

Here's an example of an electric roll trim system in use on a few canards...

Now that I know about this 'benign failure mode', I'm convinced it's definitely the way to go. I would think you could do all of this without the electric servos/actuators as well, no?

[argoldman]

I woluld make one modification of the above mentioned trim/spring mechanism. That is to mount the assembly so that the hoop spring is down from the mounting points rather than up. In the mounting orentation, as drawn, it is possible that a breakage of the spring failure could, under the right circumstances get jamed due to the segments being drawn down by gravity. The segment, shorter now, has less flexion and might cause a problem (there is not a lot of levarage in the roll aspect of the control stick.)

 

Mounted with the loop dependant, any fracture would allow both remaining ends to fall away from not only eachother but all of the other mechanism.

 

The roll trim is used principally to correct for the added weight of the passenger or if you have a R/L tank setup, asymetric fuel load. Not used a lot in flight, but necessary.

 

You could achieve the same effect without servos by using a push-pull cable, a lever, and a means of friction for the lever fo example that used in the plans. Instead of the springs and cables, you need to fix the shield end to a non-movable point, the central cable to the lever. At the other end, fix the shield where the servo goes, and use the cable (with, appropriate fittings,) in the same manner as the output shaft of the servo.

 

What you will gain using the manual system is weight, complexity, and it could end up nearly the cost of the electric system.

 

Another approach, that I have seen on Veri-ezs is a small hinged trim tab on one aileron which is actuated by a small trim motor. There is also a manufactrued device, similar, called, I think EZ TRIM.

 

Keep those wings level (or change your AH and T&B to match what you have.

[Wayne Hicks]

"one modification... is to mount..down...rather than up."

 

----> My thoughts exactly. You beat me to it.

[argoldman]

"one modification... is to mount..down...rather than up."

 

----> My thoughts exactly. You beat me to it.

Two upside-down minds with the same thought