Hello All,

I tried a search on "how to use exponential" and "setting up exponential" and could not get any solid info. Can someone help me out by explaining first what it is and then second how to use it??

Thanks in advance
Jeffrey

Fromt he Futaba website

3. What is Exponential and how do I set it?

Exponential is an adjustment to the actual curve of how the inputs are given to the servo in relation to how the stick is moved. Without expo, the servo gets exactly the same amount of movement command per millimeter of movement of the gimbal regardless of the gimbal's position (center, or extremes, for example). Many modelers use expo to soften the feel of the model's response around center to avoid over correcting. It is also recommended to add additional negative expo to high rates so that the high and low rates give similar distance of travel around center. This is helpful to avoid overcontrolling in panic situations or when changing rates.

Exponential is set independently for your 'high rate' and 'low rate' (called dual rate), by flipping the switch, just as you did setting the two dual rates.



Set up depends on which radio you have

Exponential is a good way to soften up the response around center stick, if it's too responsive. A twitchy airplane can be tamed down a bit with expo. However, if you're learning, you probably just want to reduce the throws mechanically or with the End Point Adjustment feature. Expo will become more important with wild aerobatics or 3D.

For instructions, it is important that you either ask for directions for your specific radio, or get real familiar with the manual. The manufacturers do NOT have a standard on Plus or Minus (+ or -) programming for this feature. It is possible to aggravate an oversensitive control by programming for expo with the wrong sign.

When you get past that, it's a matter of programming in a number, trying it, and adjusting it up or down according to your preference. Don't expect anyone to tell you "Enter +32% expo on elevator for perfect response."

Good luck,
Dave Olson

The examples above are correct, but can still be confusing, so I'll try to clear things up a bit.

Most people are familliar with Dual Rates. They are easy to understand, if you set your dual rates for 50%, you'll get 50% of full control throw when the stick is at 100%. By that logic, you'll get 25% of full control throw when the stick is at 50%, and so on.

The good thing about dual rates is that if you have a "Twitchy" airplane, using dual rates will smooth it out for you.

The bad thing about dual rates is that if you get into a bad situation, you only have 50% (Or whatever value you have it set to) to get out of trouble. (I've seen several crashes caused by someone forgetting that their dual rates were on and attempting a loop!)

Expo is the best of both worlds. The stick movement will result in less control throw at the beginning of travel, and more near the end. So for the first half of the stick travel (Where you need the controls to be "Soft" ) you get less movement of the surfaces, but when you crank the sticks, you still get full surface deflection.

I would like to thank everyone and especially MinnFlyer I now fully understand Expos!!! It makes perfect sense now and can’t wait to play with it on my Futaba 6EXA.

Jeffrey

Jeffrey...I started using expo with all my aiplanes a few years ago using a Futaba 8UAP and it has made all the difference in the world. There is no good setting for everyone as it all depends on your own feel of the airplane. However, I've found that a good starting point is -25% on aileron and elevator on both low and high rates. This setting is programmed in when I finish building and am setting up the throws before the maiden flight. I end up changing the expos as I get more comfortable with the airplane and get a feel for it's capabilities.

Hope this helps-Damon

Damon brings up a good point.

On Futaba Radios, the Expo values are set up in negative numbers, so if you want 30% you need to dial in -30% (Minus thirty percent)

JR uses positive numbers, and I don't know what the others use

Hitec is set up the same as Futaba.... I found out [link=http://scalebuilder.org/dr1maiden.wmv]the hard way[/link] []

Another less common use of exponential is to increase "feel" around centre. Some aircraft, for whatever reason (often because of turbulence due to poorly sealed hinge gaps), have more response to stick input at greater throws than they do around centre. Reverse exponential (- for JR, + for Futaba/hitec) can compensate for this by increasing stick movement around centre while not increasing movement at more effective deflections.

MinnFlyer's chart is pretty clear but one more thing would complete it for me. What is the percentage for the expo curve on it ?

I've been flying my Parkflyers Edge 540T with the surfaces set to minimum throws (inside holes - servos / outside holes - control horns) using the supplied TX. When I tried the 6EXA TX with it I was flying a bucking bronco !! Admittedly, I hadn't moved to the inside servo holes but I suspect it was partially because the sticks on the 6EXA are way smoother / have softer springs. I'd like to use this TX rather than the Parkflyers one and it seems that expo could be what I need to keep the model, as a relatively inexperience pilot, flyable.

If this is so, what would be good choices for the expo settings, for safe sports flying ?

Thanks

netdudeuk - One thing you can do is go inside your transmitter and adjust your stick spring pressure. I believe the procedure will be in your manual and is very easy. I have mine as high as they will go. Futaba also sells stiffer springs I've heard but I don't need that much. Stick length is also adjustable if desired.

I use expo on a few of my planes. I just checked the settings on my MT Extra 300. Keep in mind that on the 6EXA you can set a high and low expo rate. Mine are set to -20 on low rates and -50 on high rates. Most of the time I fly with low rates. Try adding some, perhaps -20 and see how it feels. If this isn't enough, you can add more.