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Expo ballpark

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Old 11-13-2005, 10:37 PM
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rainedave
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Default Expo ballpark

This post has nothing to do with Montreal.

I just bought my first computer radio - 6EXA Super - and I have set up the linkages so high rates set at 100% match the plane's instructions for max throw and low rates at 65% deflect to the recommended minimun throws. Easy enough.

Now, I would like to use a bit of exponential to smooth out accidental stick twitching around neutral (I'm getting back into R/C after a 12yr layoff and am a bit rusty). Having searched this forum I didn't find too much on what a good ballpark setting would be to start with. Someone said 10% expo on low rates and 20% on high. Does this sound about right? Or how about 15% for both? The plane is a plan built Sr. Falcon and I got the recommended throws out of the PDF manual for the ARF (I'm guessing their new ARF flies close enough to the original design).

Thanks in advance for any help. here's a thread on my project:

http://www.rcuniverse.com/forum/m_3426764/tm.htm

rainedav
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Old 11-13-2005, 11:17 PM
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Default RE: Expo ballpark

I use JR transmitters, but I think the expo settings are similar. At 10 or 15% I cannot tell anything is happening. I tend to use 50% or more. But you can always start out at 15% and go up from there.
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Old 11-13-2005, 11:24 PM
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carrellh
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Default RE: Expo ballpark

When you set the expo on your Futaba, be sure you use negative numbers. On Futaba, positive expo increases sensitivity around the center. I have mine around negative 50%, possibly a little more.
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Old 11-13-2005, 11:55 PM
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rainedave
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Default RE: Expo ballpark

Thanks. I may not really need it with this plane since it's basically a big trainer. I think I'll start with about neg. 35-40% on the rudder/nosegear high rate and then see if I actually need anything else.

On the other hand, I'm starting a little, scaled down Kaos for an FP .15 that will more than likely require some taming. At least in my hands.

Thanks,
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Old 11-14-2005, 10:33 AM
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Default RE: Expo ballpark

I run my Futaba at -60% for the 3D and "High" rates on my Funtana with -50% on the low rates, same thing for my GP Patty Wagstaff Extra. I don't personally care for running any expo on the throttle, but I know folks who do and -30% seems to be the number they use for the throttle.

It gets rid of any "twitchy" activity on straight lines but the full deflections come in quick when you need them.
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Old 11-14-2005, 07:30 PM
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Default RE: Expo ballpark

I don't have many airplane with dual rates or anything. but the airplane that I do have with dual rates and expo programmed I can't tell a difference. Even on Flight simelaters I can't tell the difference between 60 and 80. they all still seem to be quite sensitive. I don't get it I just can't seem to feel the Expo.
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Old 11-17-2005, 06:56 PM
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Default RE: Expo ballpark

I I guess I never realized how tight I feel the link between the airplane and the radio.
Let me explain...I started flying 3D (or trying) at the beginning of the summer.
I purchased a new 3D edge 540 from EF and after reading the forums decided on
40% expo on Ail and 60% on Elv to start with. When I flew the plane I noticed something
strange. Anytime I was in a downline and I pulled up elevator the plane felt as though it
did not want to react. Well that was a very uncomfortable feeling for sure. I tried moving
the cg all around to no avail, tried changing elevator throws and a few other things but it was
always still there. I finally pulled the equipment out of it and built an OMP Boxer bipe.
Guess what first flight and it was showing the same symptom's as the edge.
At this same time I was also flying a 3D foamy electric and never had any problem with it
but it was on another transmitter (RD6000) and had no expo, only dual rates.
Well that got me to thinking that I had never really used expo on any of my planes before
wonder if that could be the problem? I then dialed out all the expo and tried the bipe again.
Presto it was gone and flew rock solid. I guess I never noticed it on Ail because the ground isn't
rushing up to meet ya Anyway this episode cost me a lot of flying time this summer till I figured
out what was going on. Better to start with small amount if you are not used to it in my opinion.


Regards,

Tim Hudson
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Old 11-18-2005, 12:56 AM
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Default RE: Expo ballpark

Merlin1205, I've been thinking about a bit more. The last thing in the world I want is a delayed reaction and then sudden full throw. 50% sound like a lot. At any rate, if I use it at all, I'll start out with 10% and work from there. Thanks.
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Old 11-18-2005, 07:05 PM
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Default RE: Expo ballpark

Before flying the plane, or setting any expo, turn on transmitter and receiver. Move the sticks like you would while flying and actually see what the surfaces are doing. Also move the sticks slowly frm center to extreme and then move them quickly from center to extreme, watching what the surfaces actually do.

Then set negative xx% expo on the flying surfaces and repeat the observations. Do this at multiple percentages so you'll be able to see what it is actually doing.

It is not like a switch. Negative 50% does not mean you get zero servo movement until the stick is halfway to the extreme. It reduces the sensitivity some but it's not as extreme as I thought it would be before I tried it.

I did not put expo on the throttle, I just have it on the flying surfaces.
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Old 11-18-2005, 09:01 PM
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Default RE: Expo ballpark

10%~20% sounds like a good starting point. Generally, I don't like more than 40% since the surface starts to kick in all of sudden beyond a certain point. I would like to add that sometimes playing with the throttle expo can give you a more linear response. Good luck!
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Old 11-20-2005, 12:05 AM
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Default RE: Expo ballpark

Thanks everyone!
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