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How much expo do you use?

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Old 05-23-2002, 12:43 AM
  #1
snsmith
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Default How much expo do you use?

Just curious...what exponential rate do you guys typically use? I typically use something in the -25% range (Futaba 8U) for low rate and -40% on high rates, but I've heard of people using as high as -75%.

Any disadvantages to using a lot of expo? I've read that too much expo can be bad (or bad habit forming), but I can't really imagine why. Nonetheless, I've resisted the urge to use more although I think it may be helpful in some situations.

Thoughts, opinions, comments, etc. welcome!
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Old 05-23-2002, 01:08 AM
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akflyer
 
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Default How much expo do you use?

On some models I do not use any expo, on others I use 25-50% and on 3d planes and rates I use 65-75% on the elevator and around 30% on rudder and ailerons. I can not think of a senario that using expo would be bad. I flew my Pizzaz with an 8U at first and had the expo dialed in. I changed it to a 6XAS and boy howdy did it get lively with out the expo. I used to fly on high rates all the time, even take off and landing, but now have had to start using low rate on the elevator to get her down without an eratic fight path on final.
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Old 05-23-2002, 01:40 AM
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Joe Petro
 
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Default How much expo do you use?

I usually use -40% on high rate, and 0% on low.
On my Wasp, I actually use +40% on rudder as it makes hovering much easier.

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Old 05-23-2002, 01:41 AM
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BobbyRichardson
 
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Default How much expo do you use?

I normally used around 30% on all my planes except when I am doing a 3D type of maneuver, then I use up to 65% on elevator and rudder.
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Old 05-23-2002, 09:15 AM
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Niall
 
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Default How much expo do you use?

On my pattern plane I am using 50-60% expo on ailerons. I find it helps me keep the wings level and makes correction that bit less noticable as you don't tend to rock the wings from side to side. On elevator I am using about 30% while on rudder I use 50%, this allows me to feed in tiny bits of rudder, again making it less noticable to the judges (i hope .
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Old 05-23-2002, 09:35 AM
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Geistware
 
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Default How much expo do you use?

Iusually used from 20% on low rates to about 60% on high for elevator and aileron. I seldom use expo on my rudder.
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Old 05-23-2002, 10:51 AM
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Default How much expo do you use?

I use around -30% on my Laser 3D -- works well
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Old 05-23-2002, 12:11 PM
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George E.
 
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Default How much expo do you use?

On my knife I use 0% expo on the ailerons and elevator and -7% on the very sensitive rudder. I have 45deg throw on the elevator and rudder and 35 deg on the ailerons. Most of the time the plane is flying slow or in a stall and I don't like moving the sticks all over the place
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Old 05-23-2002, 12:47 PM
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Default How much expo do you use?

Remember that for a rotary output servo a linear response is given with roughly -16% / -18% expo, so when running 0% expo you are actually flying with the center more responsive than it should be if you were running a truly linear setup.
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Old 05-23-2002, 01:28 PM
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George E.
 
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Default That's how I like it

I realize that but I am am just getting back into the hobby after a 15+ year break and I never had expo. Now I have a computer radio but I am just used to very sensitve sticks. It's much easier for me to hover without having to move the sticks too far.
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Old 05-23-2002, 01:58 PM
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kris1
 
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Default How much expo do you use?

I find that the starting point for setting up expo is eaisest as follows:

when I set up expo I move the sticks in a normal fashon, as I would in flight, with the model on the ground. If i can move say the elevator stick without any judder on the ailerons then that is the correct place to start. If there is some movement on the ailerons the increase the expo. Do the same for the elevator and that is one stick set. It is similar for the thottle and rudder stick. Then I will try a flight and tune some more.

Cheers

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Old 05-23-2002, 05:04 PM
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snsmith
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Default How much expo do you use?

Chad, that's an interesting point that I hadn't considered...the nonlinear aspect of the rotary servo response.

I guess we need to consider how non-linear the control surface response is as well...I'm sure the resulting pitch/yaw/roll moment of 10 degrees of control surface deflection is not exactly twice that of 5 degrees of deflection. I'm trying to remember back to my fluids and aerodynamics courses, but I'm too far removed from college to remember much...
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Old 05-24-2002, 06:08 PM
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Default How much expo do you use?

I will have 100% dialled into the Majestic 2M, its quite the norm to have 60-80% on 3D Conditions with these kind of planes.
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