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Trim/Sub Trim & DR - What is the efficient way of setting it?

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Trim/Sub Trim & DR - What is the efficient way of setting it?

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Old 06-22-2007, 12:22 AM
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fadi
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Default Trim/Sub Trim & DR - What is the efficient way of setting it?

Hello
I need to setup the travel of my surfaces as per the manual on a new plane.
My transmitter is a programmable model, with the option of setting percentages on the dual rate menu, the travel menu; and it provides a sub trim menu as well.

the original settings are 100% everywhere, and 0 on the sub trims, however this is much more travel than what I need.
I found for example, that I need to reduce the low rate to 30% and the high rate to 55% on the ailerons to reach the factory settings.

Now, the question is where shall I dial these settings?
Should I keep the DR on low setting to be 100% and reduce to 30% in the travel menu? then adjust the high rate percentage...
Or shall keep the travels at 100% in each direction, and dial 30% in the DR menu?

Which option will give me a finer and precise range? What is the difference anyway in these two methods.
Finally, how shall I setup the sub trims? Is that required?


Thank you for your time
Cheers

Fadi
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Old 06-22-2007, 07:00 AM
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Default RE: Trim/Sub Trim & DR - What is the efficient way of setting it?

Most newbies don't like this answer to that question but...............

Do the setting in your airplane. There is an excellent article in Model Aviation this month about rigging servo-to-surface and it explains why it's best to get the rigging right.

What you've doing to get the suggested throws strongly suggests that you really need to look at the rigging in the airplane. If you're getting way too much surface deflection, you need to look first at the servo arm. Move the pushrod connection toward the servo, not away. Use the hole closest to the servo. Now look at the elevator or aileron movement. If it's still too much, the go to the horn on that surface and move the connection OUT one hole and check the surface travel again.

When you do all the adjustment in the radio instead of the airplane, you usually make a bad setup for the servo and even worse setup for the servo.
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Old 06-22-2007, 07:06 AM
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Default RE: Trim/Sub Trim & DR - What is the efficient way of setting it?

So how do you use your neat new computer radio?

Well, dual rates actually aren't really for setting end points or neutral points. They are used for controlling how sensitive the airplane flies after you've got the surface deflections sorted.

Most people set the switches to give 100% for High and some value around 50-70% for Low. Then decide when you want to use the rates in flight. For example, you probably want to use high rates to snap roll. It takes more elevator to stall the wing, a requirement for a snap, and more rudder/aileron to do a fast snap. But some airplanes will snap out of everyday loops if the elevator moves too far, so you may want to do loops and such on Low rates to reduce the snap tendency.

So forget about setting travel with dual rates.
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Old 06-22-2007, 07:11 AM
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Default RE: Trim/Sub Trim & DR - What is the efficient way of setting it?

But setting throws with the End Point adjustment is a great thing for a radio to do. After you've set the airplane's servo-surface rigging properly, that is.

Just use the travel menu for that. It's there to give just what most of us want, a fine tuning tool to set the throws.
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Old 06-22-2007, 07:25 AM
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Default RE: Trim/Sub Trim & DR - What is the efficient way of setting it?

However, I've gotten one detail out of sequence.

After you rig your new airplane and have adjusted to get the recommended throws, what do you do? Maiden it, right. And what happens? It needs a couple clicks of aileron trim and maybe a few clicks of elevator trim. What to do about that? and what's the best radio adjustment to deal with trim?

It's really a good idea to move the trim settings off the radio and onto the airplane. That way you won't ever lose the settings that apply to the airplane by a mistake with the radio. So you also want to lengthen or shorten the pushrods (screw type clevise/pushrod setups were designed just for this job) to adjust the trim into the airplane. And you want to do this soon after maiden and before you get real serious sorting your dual rate proportions etc.
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Old 06-22-2007, 07:32 AM
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Default RE: Trim/Sub Trim & DR - What is the efficient way of setting it?

da Rock,

Great explanation. I'm rigging a plane now doing those exact things. Kinda fun...if you can call geometry fun.
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Old 06-22-2007, 07:35 AM
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Default RE: Trim/Sub Trim & DR - What is the efficient way of setting it?

BTW, you've not mentioned EXPONENTIAL

You really should try it. It's a really good thing to use and you only get it on the better radios. I've yet to run into anyone who has given it an honest test who doesn't use it.

I've had a student recently who just couldn't get over the nerves. And he flew like it. And after setting about 50% expo in his radio, the guy was amazed at how less stressful it was to fly. And darned if we all weren't amazed at his sudden progress too.

And one of our 2nd year flyers finally bought a step-up radio. And he was grousing about how he'd wasted his money because he didn't really need all the stupid stuff it'd do, etc etc. I asked him what he thought of expo and his answer was, "what?" So we slapped 30% on that expensive purchase and guess what...... he shut up and has been smiling ever since. Soon I'm gonna show him some of the other things that radio can do for him. Just might make a techie out of him yet.

Try the expo. You'll find that flying straight is not so hard. And landings and takeoffs are easier 'cause you have finer control. Finer control around neutral is the big selling point.
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Old 06-22-2007, 07:38 AM
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Default RE: Trim/Sub Trim & DR - What is the efficient way of setting it?


ORIGINAL: meaden

da Rock,

Great explanation. I'm rigging a plane now doing those exact things. Kinda fun...if you can call geometry fun.

Heck, meaden,
All this stuff is fun ain't it. Darned if I didn't catch myself doing some simple physics formulas the other day and smiling. This modeling stuff sneaks up on us if we aren't careful.

Hey, wish ya' lived closer. We've got a great bunch and an excellent field and good modelers are always welcome.
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Old 06-22-2007, 08:10 AM
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Default RE: Trim/Sub Trim & DR - What is the efficient way of setting it?

LOL, it is all physics and geometry. Along the lines of "I went to a fight and a hockey game broke out."

Thanks for the invite. I don't get up that way much. I tend to go south to FL (family down there.) Your welcome to come fly in the cross winds of Stone Mountain!
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