Digital on SUPRA Elevator??

[vintagesailplnr]

Hi:

My AVA's have reasonable rounded LE on the stabs. my new SUPRA has an extremely thin stab with a very sharp LE.

Will an analog servo make this ship like a "kerosened" squirrel?

Will analog servo's precision be OK for this stab??? I would think +/- 2 to 3 degrees off "neutral" would make this ship very interesting??????
TIA

Would appreciate any suggestions for types of servos

The threads on RCuniverse seem to have digital servos all around!
Jim

[little flyer]

Digitals are the way to go, Jr DS 368, Jr DS 3421 and airtroncis 761's are all good choices.

[jtlsf5]

Jim,
Digitals are certainly nice if you really need the power and centering precision. This comes with a price, namely higher current drain. You need to take a look at what you plan to do with the plane before you make a judgement that high priced digitals are needed.

If you are going to fly F3J, F3B, serious TD competition with max tension launches, then digitals are certainly preferred.

If you are only going to sportfly your Supra, digitals are probably overkill. You can easily get a long with a good analog servo for this application, provided they meet the size/power criteria.

A key consideration with the Supra is the amount of space you have available. The Supra was designed for small servos, a consequence of the small cross sectional area in the fuse, and thin sections in the wing. You need a certain amount of power to move all the surfaces with authority, and digitals certainly give you that in a small package.

JT

[baum58]

Well this is the storry on digit's

Analog + slopy install = crap

Digital + slopy install = expensive crap

Analog + the best install you can do = great start

Digital + the best install you can do = competition setup.

The best install you can do: no play in servo gear, clevisis or pushrods, no binding, perfect centering of all hinged surfaces.... no flex on servo install, no flex on push rods. I hope you all get the idea here...

Digit's install: first elevator, infact the JR3421 is best, flaps next, same servo if it fits or a JR 368 or airtronics 761, I have never found the need for a digital for the rudder...

Peter

[bigjohn]

Well this is the storry on digit's

Analog + slopy install = crap

Digital + slopy install = expensive crap

Analog + the best install you can do = great start

Digital + the best install you can do = competition setup.

The best install you can do: no play in servo gear, clevisis or pushrods, no binding, perfect centering of all hinged surfaces.... no flex on servo install, no flex on push rods. I hope you all get the idea here...

Digit's install: first elevator, infact the JR3421 is best, flaps next, same servo if it fits or a JR 368 or airtronics 761, I have never found the need for a digital for the rudder...

Peter

This is where it is at. Lemme just add that you can make use of the precision of a good analog servo by using correct servo gearing.

You want to use a short servo horn with as much servo travel as possible (ATV > 100). This is because the servo moves in steps. Depending on the radio, could be 512, 1024, 2048 or more steps. For each step, if you have a longer servo horn, the motion of the step is bigger. For precision, you want less motion per step.

So, you set up the servo horn short, boost the ATV as high as is practical. Then make the elevator control horn long enough to result in the correct servo throw. Of course you can fine tune with ATV settings, but if your ATV is set below about 80% you are cheating yourself of servo power & precision.

That will give you the best advantage regardless of servo type. A digital servo is only necessary if good setup doesn't satisfy you.

[baum58]

All OK exept: the rudder, Here I go for best speed, the longest servo arm possible for the best servo speed and rudder speed possible. I copied the setup of my Pike Perfect to my Super Ava, Fazer and Supra.

Peter

[bigjohn]

I'd love to hear how rudder speed on a sailplane could be important enough to optimize. 20+ years flying sailplanes and I sure can't think of a reason.

[baum58]

3 reasons........ landings, landings, oh ja landings. If you are off line on approach the rear needs to come around and rudder will do the job, not ailerons. With flight modes the rudder is turned down and only in high mode in landing mode.


Peter

[atmosteve]

Jim, just fly it, who cares what servo's are asked to do the job as long as they are a reasonable quality mini style. Pseudo techno threads like this bore me to shits..

[baum58]

once you (Steve) get your hand on a propery setup glider you will not go back....... work on the setup regardless if you fly with digital or not.....

Peter

[atmosteve]

Peter you are more than welcome to fly any of mine anytime if you visit, sincerely. :)
They may not be the silver carpet ride you expect, but that will hardly be the fault of the hardware. I was setting up aircraft when you were picking your nose and figuring out how to fold a paper airplane perhaps? I don't know.
;) Anyway your words were drawing a very long bow, not wise.

Sorry to be driven off topic guys, it's my fault.
Let the relevant info roll on. :)

[vintagesailplnr]

Hello guys:
THANKS for the help on servos. I am going with mini (40+ oz torque) digital on elevator and maybe on flaps and analog on all others.

I agree witrh the slop in setup - I can deal with that, but I cannot make a sloppy servo better.

No one recommended Hitec - I've never had a problem????? What am I missing or have I just been lucky?

THANKS AGAIN!!!!
Jim

[mlachow]

OK, so have you switched to a 9303 2.4 yet? Less latency between stick input and servo moving....

Or try something like a JR Z3650 servo which moves pretty fast. That way you can get back some of the precision you are throwing away.

3 reasons........ landings, landings, oh ja landings. If you are off line on approach the rear needs to come around and rudder will do the job, not ailerons. With flight modes the rudder is turned down and only in high mode in landing mode.


Peter

[mlachow]

Will analog servo's precision be OK for this stab??? I would think +/- 2 to 3 degrees off "neutral" would make this ship very interesting??????


Precision has nothing to do with analog vs digital. It does have to do with servo quality.

Go to a contest and listen when guys turn on and get ready to fly. If you head the beep, beep, beep when they are recentering , again, ask what servos they use and make sure you avoid them.

Of course, with the price of a Supra, which I'm sure you hope to be flying for a few years, the savings on some inexpensive servos doesn't seem to make sense.

The place where the Digitals really help are when you are really placing flight loads on the airframe, like during launch, or landing.

I think one of the few places where I would consider an analog servo today would be spoilers. Just in case you overdrive them to avoid killing batteries.

[Robglover]

I have built a bunch of Supras using all 94761s. I'll continue to use them. And yes, Peter is right about the setup/install.