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Old Dec 09, 2002, 12:23 PM
YVR
Sean in YVR (Vancouver)
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Pulling to canopy in knife-edge?

The model in question is a Super Mini Diablotin - it doesn't seem to really like knife edge, but will sustain it at or near WOT with a lot of rudder input. As I've been stretching out the KE runs, however, I've noticed it pulls towards the canopy - ie the flight path is sort of banana shaped. Is this typical? Can someone more experienced than I explain why this happens, and how (if) I can correct it? Thanks!

Sean
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Old Dec 09, 2002, 01:02 PM
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Sean,
Yes, it is a trait of the Mini D (pulling toward canopy in KE). Gary Wright discussed this in one of his posts about why he shaped the E3D's canopy and rear deck the way he did (function over form). If you have a radio that allows mixing, you can probably compensate that way. I can't KE mine (I'm a mere mortal), but Gary flew it at this year's Sizzle in MD .....and he was able to KE it fine.
Ed
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Old Dec 09, 2002, 01:10 PM
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Sean in YVR (Vancouver)
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Hmmm. So would I mix in a bit of down elevator with rudder?
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Old Dec 09, 2002, 01:17 PM
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Quote:
Originally posted by YVR
Hmmm. So would I mix in a bit of down elevator with rudder?
Sean,
I have not done it, so can't say for sure. Perhaps someone who has can offer some input here ?
Ed
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Old Dec 09, 2002, 01:34 PM
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I'm an aerobatic novice and I was just wondering if the plane does pull a little in one direction and a little control is needed to offset it, isn't that part of the whole aerobatic experience instead of having the radio do the work? So if you add a little down elevator does it fly straight in the KE?

Kelvin
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Old Dec 09, 2002, 02:08 PM
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I'm still dialing in my E3D and it was pulling towards the canopy on KE. In the online maual, Gary suggests that one could dial in some "down" in the ailerons to counter some of the pitching tendancy.
Most of my aerobatic planes have been pretty neutral on the KE requiring only opposite aileron to counter roll coupling, with minor adjustments on the elevator to keep it going in a straight line. You can dial in computer mixes but you'll want it as a certain "flight mode" (ie when you want to do KE) rather than a constant mix. I like to manually tune the plane before I start adding mixes, but sometimes you can only go so far.
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Old Dec 09, 2002, 03:35 PM
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Just getting the plane to fly straight and level by fiddling with the trim tabs is not enough if you plan on doing anything above and beyond flying straight and level. There are a whole series of tests you can go through to trim a plane for aerobatics. One such trim chart is posted on the Great Planes website.

I believe the pulling-toward-the-canopy behavior is indicative of a slightly negative wing incidence. Drooping both ailerons slightly has the same basic effect as increasing the wing's incidence, but the proper way is to shim up the wing until the plane flies correctly, then sand the wing saddle to match.
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Old Dec 09, 2002, 06:19 PM
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Most models display some sort of interaction between the conrtrol axes. Simple to fix. Set up a free mixer on the TX with rudder as the driver and elevator as the slave. Mix in down elevator with rudder, it will have to be set in each direction. Then go fly and adjust to get neutral trim with rudder in knife edge.

You will probably find that the model rolls with rudder so simply set up another mixer with rudder as the driver and aileron as slave.

Trimming a model to make it neutral like this allows you to concentrate on getting your aerobatics just right without having to worry about interaction between the controls. Imagine trying to fly a nice slow roll with the model tucking in and changing roll rate when you apply rudder to maintain the line!! With mixing easy, well sort of.

Bob
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Old Dec 09, 2002, 06:46 PM
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Quote:
Originally posted by mkirsch1
Just getting the plane to fly straight and level by fiddling with the trim tabs is not enough if you plan on doing anything above and beyond flying straight and level. There are a whole series of tests you can go through to trim a plane for aerobatics. One such trim chart is posted on the Great Planes website.

I believe the pulling-toward-the-canopy behavior is indicative of a slightly negative wing incidence. Drooping both ailerons slightly has the same basic effect as increasing the wing's incidence, but the proper way is to shim up the wing until the plane flies correctly, then sand the wing saddle to match.
With the E3D, the wing is permanently fixed so you end up dropping the ailerons for incidence trimming. Other than that, one should fix the incidence however they can.
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Old Dec 10, 2002, 01:13 AM
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If the Mini Diablotin is anything like the Super, which I believe it is, then KE is generally hard. So you should feel good about being able to KE at all.

If you have a Tx where you can dial in the flaperon amount, you can fiddle with it in flight to get it right. It's usually a pretty small amount.

But if your plane is basically tracking well and NOT roll coupling, which is the biggest problem on Diablotins (E3D don't have this problem as much), then I would just steer with the elevator since it acts as your rudder. You need to learn to do this anyway because you may want to KE circle or KE across the field and come back by turning. It's a fun thing to do.

Make sure you crank up your expo to 100% so you can have fine control.

-- Kyle
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Old Dec 10, 2002, 02:17 AM
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Sean in YVR (Vancouver)
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Lots of good feedback - thanks all. I would say the "pulling to canopy" tendency is more pronounced than any roll coupling effect.

mkirsch1 - I looked at the GP website and couldn't see the chart you made reference to - if you have a link I'd appreciate it.

Based on the input here, I think I'll try playing with my flaperon settings - I was wanting to do that anyway to set up an "up ailerons" switch to work on parachutes/harriers, so I'll also program a slight "down ailerons" setting for KE and see how that works. And, of course, start trying to steer with the elevator!

Sean
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Old Dec 10, 2002, 03:23 AM
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The aircraft pulling to the canopy could also be due to too much dihedral, or the tail plane being too low on the Fuz. I found with my Seduction FS, that moving the CofG further forward, from the rearward CofG, reduced the tendency to pull to the canopy. It also made the plane much nicer to fly better low speed handling. The flat spins are not so flat, so I now cople the flaps to elevator to get round this..


I tend not to set-up mixing for KE, preferring to fly the plane, as the plane will have different flight characteristics for normal flight with mixing. I have set them on a switch, but keep forgetting to switch it when I need it.


Cheers

Kris
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Old Dec 10, 2002, 08:58 AM
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I would sure like one of you guys to fly my E3D. It flys with very little trim changes but I bet if someone experienced in aerobatics flew it they would probably suggest a lot of small changes to make it fly better and probably easier.

How did you guys learn all this stuff? I basically set up the plane to fly level hands off then proceed from there.

Kelvin
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Old Dec 10, 2002, 11:17 AM
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Quote:
Originally posted by kelvin


How did you guys learn all this stuff? I basically set up the plane to fly level hands off then proceed from there.

Kelvin
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The wingtips on the Diablotin also slow the rolls down and cause it to do that in knife edge. If you remove the tips and leave them flat like on the E3D it will roll better and knife edge better. It is known on fub-flys that the flat tip is better, seems everyone removes them on the magics, Laser 3d's and other popular ones.
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Old Dec 10, 2002, 11:20 AM
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Quote:
Originally posted by kelvin
How did you guys learn all this stuff? I basically set up the plane to fly level hands off then proceed from there.

Kelvin
Kelvin,
All the books in the world won't make you a better pilot, it all just comes down to practice, and lots of it.

Like Kris said it really can also depend on your CG. The E3D has a sweet spot on her CG where KE and hovering are very easy. I've found it to be about 1/2" behind the spar. Anything else and you will find that you need to do a lot of compensating in the roll axis, and some on your elevator (currently rudder if in KE)

Oh, you mentioned you trim it to fly straight and level, I started laughing when I read this (not at you, at myself) because one day I took off and just flew some circles, and I found that my E3D was out of trim. I never realized it in a summer of flying, just because I was never flying straight and level long enough. (I've since trimmed it.)
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