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Old Aug 12, 2012, 09:51 AM
A man with too many toys
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Aileron Differential

I am setting up my new SIG Rascal 72 EG and need some input of how much to program for the first flight. What do most of you use on semi-symmetrical airfoils?

.
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Old Aug 12, 2012, 10:16 AM
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Quote:
Originally Posted by RC Man View Post
I am setting up my new SIG Rascal 72 EG and need some input of how much to program for the first flight. What do most of you use on semi-symmetrical airfoils?

.
It ought to fly OK without any differential. I'd start off with none and see how much yaw you get from aileron input. If you need any at all, it's probably not much more than 5% reduced deflection on the down ail. Just my $0.02
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Old Aug 12, 2012, 10:30 AM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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Are control throws included in the assembly manual?

If not, consider contacting Sig directly - they have a little experience in the RC business' and a fair command of English

D
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Old Aug 12, 2012, 12:23 PM
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Are you asking about control surface throw range, or differential throw?

Most manuals (and certainly a SIG manual) will have throw ranges. But differential information is rarely included. For a non-symmetrical wing, I offset the aileron servo arms so that up aileron gets a bit more up throw than down. But with a high wing plane that is stable, you may not notice the difference.
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Old Aug 12, 2012, 01:24 PM
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Please post some pictures of your Rascal 72, along with some specs.

As for differential, on my original Rascal 40, no differential was needed.
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Old Aug 14, 2012, 07:51 AM
A man with too many toys
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I only had a chance to do a little flying and found that 15% was too much and 5% was close but it may need a little more. I need to testing to fine tune it. I am waiting for batteries and a Scorpion SII-3026 motor so it will be a while before I get back to flight testing.


After that I will post some photos in the other thread.

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Old Aug 14, 2012, 10:02 AM
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The only time you "need" aileron differential, is when, at full aileron throw, it causes adverse yaw, that is, when the down aileron causes enough drag to "pull" that wing backward.

Les
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Old Aug 14, 2012, 10:39 AM
A man with too many toys
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Originally Posted by LesUyeda View Post
The only time you "need" aileron differential, is when, at full aileron throw, it causes adverse yaw, that is, when the down aileron causes enough drag to "pull" that wing backward.

Les
I have found that the best way to tune aileron differential is to do aileron rolls. If they are not axial around the center of the fuselage then you need to adjust the differential. Most airplanes do much nicer looking rolls with differential and I have it on most of my airplanes. If you donít do rolls it will help coordinate turns but itís hard to tune just watching turns so most that donít do aerobatics donít use it.


If your transmitter has that option next time you are out flying give it a try and you should have better looking rolls after tuning.


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Old Aug 14, 2012, 11:16 AM
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Originally Posted by RC Man View Post
I have found that the best way to tune aileron differential is to do aileron rolls. If they are not axial around the center of the fuselage then you need to adjust the differential. Most airplanes do much nicer looking rolls with differential and I have it on most of my airplanes. If you donít do rolls it will help coordinate turns but itís hard to tune just watching turns so most that donít do aerobatics donít use it.


If your transmitter has that option next time you are out flying give it a try and you should have better looking rolls after tuning.


.
You hit the nail on the head; consecutive aileron only rolls will indicate the need for differential.

If the model does a barrel roll, the inboard aileron needs to raise more.
If it does an "outside roll" (model looks like it falls off a table), the inboard aileron needs less up throw.

One additional "fine tuning" recommendation and that is to do the rolls straight down with power off. Once the roll is tuned to accomplish tight axial rolls, then do them going up and down with power. If the model does barrel rolls, the thrust line needs to be pointed down. If it does the rolls "outside", the thrust angle needs to be pointed up.
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Old Aug 14, 2012, 11:59 AM
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High winged Cub type models need aileron differential and use of rudder with ailerons for smooth turns without "adverse yaw". Low winged warbirds can turn well with ailerons and elevator only , it's called "yank and bank" flying. Differential ailron movement ( mostly up,little down) is intended to reduce drag of the down-going aileron which resists turning in the desired direction.
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Old Aug 14, 2012, 02:08 PM
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Good question!!
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