Balsacutter

My Feedback: (3)

Just bought my first computer radio, at Futaba 7CAP, and I'm looking forward to expo on the ail and elevator to calm down little twitchy little electrics.

A question so basic they NEVER explain it in the documentation: To decrease control sensitivity near the center but maintain full control at the extremes, do you program POSITIVE or NEGATIVE expo percentage????

MikeEast

My Feedback: (3)

On Futaba Radios a negative number will soften the controls around center, this is what you want. On a JR radio, just the opposite, a positive number softens the center.

Cyclic Hardover

My Feedback: (3)

To give you an idea of Expo, well, I really don't like it much. I only have about 10% dialed in on most of my planes. If you were fly somebody's plane who had, lets say 50%expo. The controls would feel very sloppy. You going to turn the plane and you keep moving the sticks over further and further and finally your sticks are way over at the stops before the plane reacts. Of course you would get use to this after awhile but I just don't like it.

If I were you, I would dial in maybe 15-20% at most and fly it like that until you get the feel of it.

MikeEast

My Feedback: (3)

Totally completely 100% personal preference. There is no realy "best" when it comes to expo. Its about what feels right and provides you with the best control to get the performance that you want.

I will say one thing that expo will provide and that is consistant "feel" between low and high rates.
That is, you add expo on your higher rates so that the control surface response has the same feel (and actual movement) between low rates and high rates. On 9C and higher end Futaba radios you can actually see a "curve" graph on the screen. This allows you to actually see the stick responce via the graph so that you can match the response EXACTLY where you want it but still get the big throws when you need it.

parrthd

i fly futaba and tune in -35% on ailerons and elevator....i use full throw on rudder on both high/low rates

i tuned up from a skysport 4 and i couldn't believe the difference. but like it's already been said, it's all about personal preference.

PipeMajor

My Feedback: (1)

Building on this topic, I have the expo rates on my Futaba 6XAS set to -20, -30, 0 and -20 on channels 1-4 (aileron, elevator, throttle and rudder) respectively. This is for a trainer but I'm thinking to pull them off since we're past the solo stage and starting basic aerobatics.

My question regards dual rates. My instruction manual has suggested throws for each of the primary control surfaces. Would I set those up as my high rates or low rates?

parrthd

let's say it like this.....my trainer i started with 80/100 after i got used to that i increased to 100/120 (or 140 i can't remember which- it's the highest setting on the 6exa) the plane flew nothing like the slow lazy trainer that i remembered. i literally outflew the airframe and after a wing failure (just gave way at the wing joint during straight level flight) and a repair, i haven't put any electronics back into it to try it out.

Dr1Driver

PipeMajor, I would set the high rates at slightly more than recommended and the low rates at slightly less.

I love using negative exponential on a real twitchy aerobatic plane. It make those landings a lot smoother.

Exponential can also help even out the engine response to the stick.

Dr.1

PipeMajor

My Feedback: (1)

Ok, that would make sense.
I'm sure my Futaba 6XAs doesn't have expo on the throttle. Upon examination, it does allow an expo value for ch 3 but I'm not sure how it would respond. Would you get the softness around the midrange throttle setting? I don't think a halfway closed throttle would equate to exactly a halfway engine speed. Suppose I could play around with it but never really missed not having it.

MikeEast

My Feedback: (3)

What DR1 is talking about is a throttle curve. It should be some sort of a mix in your menu (if available) that allows for you so set the throttle stick so that more stick moves = more/less throttle movement in certain places. Its a little different than a PMix as it has about 5 points that you set at different percentages of 100. The closer 2 numbers are together the more sensitive and responsive the throttle will be there. The further apart, the less responsive. On a 5 point curve you would set it up at something like 0-25-50-75-100 if you just wanted normal throttle response. Anywhere you move the numbers from there is going to alter the throttles response to the stick movement in that part of the range of the stick.

Cyclic Hardover

My Feedback: (3)

Expo reminds me of the old days when cars had regular brakes. Then you took some Cadillac out for a spin that had so called "power brakes". You stepped on those things and it was so responsive, the next thing you new, your face was kissing the windshield. If you go the wrong way and accidently dial in positive expo, your infor a wild ride.

B.L.E.

Reverse expo on the throttle channel is useful to make electrics throttle more like gas engines. Some ESCs have this function built in. The problem with electrics is that the rpm of the motor is too linear. Half throttle = half rpm = 1/4 thrust, quarter throttle = 1/4 full throttle rpm = 1/16 full throttle thrust etc. By using a reverse expo curve, the motor rpm is not linear but the resulting thrust is linear, or more nearly so.

shag555

I accidentally put in "positive" expo on a Futaba for a 27% Extra and nearly totalled it, it flew so erratic! That was the maiden flight too! Got it down and worked through the bugs till I realized that I input the expos the wrong way! Took them out to zero and it then flew like a trainer. Be careful. By the way, I have the same 6EXA radio but replaced it with a JR9303 after realizing the little Fut limitations.

MPB

PipeMajor

My Feedback: (1)

When I was taking BTW Driver's Ed back in the late 60's I found the GM cars all tended to have overboosted steering and brakes. It made for a pronounced lack of feedback and some exciting stops. I'd hop into my little VW with it's non-power but quick steering and std brakes and it was a delight (except in a crosswind [X(]). My old man latched onto a huge Dodge Monoco w/440 ci polluter for towing a travel trailer. It was so vague when the steering wheel was in neutral I had difficulty keeping it going straight down the road. In the late 70's I bought a Honda Accord with it's precision rack and pinion steering and a silky smooth 5 speed. It was like it was on rails - very solid feeling car despite being only 1800 lbs. I never cared for the GM hiway boats back then and still prefer the nimbler handling offerings from Japan today (even tho most of them are made here).

Going back to model airplane throttles, I'll agree the last ΒΌ of travel on the high speed end of my carb makes very little difference in engine speed. To get half power I'll likely have to have it ΒΌ open - not halfway. A geometric response curve would make sense but I think my brain is simply programmed to move it most of the way down to effectively throttle down. Same situation for my automobiles. I doubt in normal driving I ever press down more than 1" on the accelerator pedal.