Reasons for Excessive Pitch Sensitivity? - Page 2 - RCCanada - Canada Radio Controlled Hobby Forum
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Old 07-13-2016, 07:34 PM   #11
OLD PRAIRIE RED NECK
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Re: Reasons for Excessive Pitch Sensitivity?


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I added a wind to a 4 Star 40 to make it a Bipe and on the first flight realized I had upset the balance between wing area and tail feather area.

Being a bit lazy I took the rudder and elevator off and more than doubled their area. The result was a VERY sensitive elevator! Rudder was fine. I decreased the elevator throw on the linkage only to 1/4", (not electronically to preserve resolution), added 80% Expo and she tamed right down.

I really believe doing the change in the programming would have given me far too much dead band and the results would not have been satisfactory.
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Old 07-13-2016, 09:08 PM   #12
Mike Sebastien
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Re: Reasons for Excessive Pitch Sensitivity?

80% is way to much exponential. When you have that much and you move the stick and hit the curve you have a crap load load of throw. Exponential rates are meant to desensitize neutral not correct bad aircraft design
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Old 07-14-2016, 06:16 AM   #13
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Re: Reasons for Excessive Pitch Sensitivity?

How true.

For someone not understanding what Mike means, regardless of how much positive or negative expo programmed in, full deflection of the stick still has the same deflection of the surface. With large amounts of expo, (negative for Futaba, while Positive with JR) then the less actual control movement you will have moving the stick close to neutral.

That may deaden sensitivity near center stick, but large values mean the stick has to move further to get the same deflection. The stick movement beyond that then has to give you from the slight amount of control deflection to full for less and less stick.

The result is a wide dead band, with a sudden alteration and acceleration of control movement to equivalent stick movement as you continue away from center. The larger the expo the more pronounced this becomes.

I have actually been caught with this, most often on maidens where a guess at expo values, even if close to all other craft and relatively moderate, shows completely different behavior. I learned to start with lower settings and work up from there if required.

I find Futaba not as sensitive to that slope unless you increase to 30% or more. JR seems less.
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Old 07-14-2016, 06:52 AM   #14
Mike Sebastien
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Re: Reasons for Excessive Pitch Sensitivity?

I usually start with 15 to 20 % (Futaba) on the elevator and never really find a need to change it. If it is pitch sensitive I decrease the control throw.

There was guy in the 80's who designed the Phoenix pattern aircraft series. He did very well flying pattern in the states. He was once asked why he never uses dual rates. His reply "I adjust the control throws to my liking and then only put as much stick in that is required for the maneuver." I have followed that advice
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Old 07-14-2016, 07:41 AM   #15
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Re: Reasons for Excessive Pitch Sensitivity?

Yes Mike if you reread my post it was bad design that I was compensating for. I strongly suspect this to be the case with Gary's plane also. I'm thinking the horizontal tail is trying to operate in the downwash from the wing.

As far as there being a right and wrong amount of expo - that is a highly individual thing. Whatever works for you is perfect and whatever works for me is too. Personally I don't like flying planes that are "hair trigger" around the center of the sticks where a blink of an eye or a nip from a bug is the difference between 10 feet off or scattered down the runway on final! No "Turret's Syndrome" flights for me thank you very much!

If you are getting true dead band from expo then there is something wrong with your radio. Control movement should be totally smooth without interruption though the full range. The only thing that should change is the rate of that motion.
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