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Is it necessary to have digital servos to be successful flying pattern or IMAC?

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Old 07-24-2009, 07:38 AM
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winglift
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Default Is it necessary to have digital servos to be successful flying pattern or IMAC?

I was curious what others might think about this. Is it really necessary to use the digital servos to perform pattern or IMAC maneuvers. The maneuvers are benign compared to 3D and TOC. I am new to pattern, but have been flying RC for many years now. I am getting the GP Extra 300 and wanted to set it up to learn pattern. RC magazine has a review of it and I noticed that he selected 3-Futaba S9650's; 1-Futaba S9252; and 1-Futaba S3155 servos for a grand total of $315! That got me thinking about the maneuvers of pattern and the servos used. Any comments, thoughts or recommendations welcome?
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Old 07-24-2009, 08:59 AM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

Digital servos generally center better, have higher holding torques, and provide the maximum resolution available. All of these are critical to precision aerobatics, whether it is IMAC or pattern/F3A. In fact, all three of these are also a huge benefit for 3D flyers, at least those flying large planes.

EDITED TO ADD:

But none of this should be construed to mean that you "need" digital servos. But you will find out very quickly that almost nobody uses analog servos in either IMAC or pattern.
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Old 07-24-2009, 09:13 AM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

Of course not. If you need higher strength or more exact centering then they are another way to make your life easier. Is it possible to fly good IMAC or pattern without them? Certainly. It was done for years before digital servos came along! Having said that, if the budget allows... I'd always put them in any competition airplane I was flying. Of course I also run 70% expo in those same planes so there is an argument that all that precision is somewhat wasted... but the increased strength and better centering are nice to have if you can afford it.
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Old 07-24-2009, 03:28 PM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?


Quote:
ORIGINAL: winglift
Is it really necessary to use the digital servos to perform pattern or IMAC maneuvers. The maneuvers are benign compared to 3D and TOC.
Opening disclaimer: "Digital" servos are actually microprocessor controlled analog servos, but that's a long explanation.

Are digital servos necessary, no. Advisable, definitely yes. One good example is with aileron control in a high G radius. The ailerons want to droop from the G's and will quite naturally have an effect on wing lift as a result. The idea is to eliminate or at least severely minimize that droop with an overwhelming countering force. An older analog servo can never match the digital servo capability to rapidly sense the slight movement off center and to agressively hold things in place. There is a much greater chance that a model with analog servos on aileron will have a rolling tendency due to uneven aileron droop than one with digital servos.

Snaps are another reason to use digital servos. You want a very agressive (high torque from the start) and rapid movement of the elevator to properly initiate a snap. You also want a very positive rudder response. Due to the violence of a snap, the rudder really benefits from a strong digital servo to hold it where you want it during the snap, and to move it positively and agressively to the position to stop the snap.
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Old 07-25-2009, 02:52 AM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

2 years ago, i definitely would have said, no..... IMO where they matter most is in the ailerons, they really add crispness... and yes i have compared digital vs analog in the same plane
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Old 07-27-2009, 03:47 PM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

Let's look at it this way... Digital servos are just another tool in your toolbox to help make your flying easier. Do you really NEED a pneumatic framing nailer to build that new house? Not really. You could just use the trusty old analog hammer. ...but that nailer sure makes things go much smoother!!

Seriously, I didn't start using all digital servos until last year, and that's all the way up through advanced. Now that I am using them, I'm doing less searching for neutral, fewer minor corrections, etc... The plane has that "locked-in" feel. I wouldn't want to go back to analog now!

gh
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Old 07-27-2009, 11:38 PM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

I did a very basic test comparing a standard analog servo and a standard digital servo - very basic.

I had an analog servo (Futaba 3004) in a plane. I adjusted the trim so the rudder was perfectly aligned with the vertical stab. I repeatedly moved the rudder left, then center, then right, then center, and watched where the rudder ended up. Rarely was it perfectly centered with the vertical stab.

I did the same with a digital servo (JR DS821) and found that it returned at least close enough to center that I couldn't measure the difference.

So, digital servos center better.

When we talk about IMAC or pattern, we are talking about precision aerobatics with a type of RC airplane. Having a servo that doesn't center well turns the precision part into a lot more work for the pilot. A loop with a rudder that isn't centered becomes a corkscrew if you don't correct for it.
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Old 08-01-2009, 11:45 AM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

Plain and simple...Yes.
But of course it comes with more things like the other mentioned.
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Old 08-28-2009, 10:23 AM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

Yes,..you can be competative with a non-digital (analog servo) in a plane under 27% in size. As already stated,..thats all we had to fly with not to long ago.

Digitals are the way to go, especially if you are wanting to work on 3-D stuff (rolling harriers, walls, blenders, waterfalls,etc). My 40% Carden Cap had all analog Futaba (non-digital) servos in it. The areas you will loose performance as I noticed several years ago, was in the 3-D area especially. You have to have the holding power of the digitals, my Cap would perform well, but the servos (analog) gave up on me a bit more than I was comfortable with executing low level 3-D stuff.

Precission flying,......the digitals are critical by todays standards for leveling the playing field with your fellow competitors. Example:My last major IMAC type contest in 2003,..again I was flying the CAP 232 and we had to fly in a 25+ mile per hour cross wind and still execute at a high level. I was the only guy still flying analog servos (non-digital) I had flown my known round(Unlimited) and all the way through the flight I kept saying to myself,...something is wrong with this plane(232 was a borrowed plane, my 39% 330 primary plane was lost several weeks prior to the contest,..all digitals),..it's not flying right? The short story,...the servos were being worked to the max in the wind (stalling the servo) and by the the sequence and giving up (analog servos make max. torque at 60 degree's of deflection, digitals make it instantly for the sake of comparisson) and we don't fly with that much throw for precission stuff. My 15 flights of practice on the plane were in light winds,..had no idea!!! I even stripped out a pair of giant 3801's on the rudder executing a snap in the wicked wind,..nylon gears(older popular equipment set-up from past years,..outdated itself).

The investment,..material and time we put into our planes,...you really do not want to skimp on servos in regards to analog-vs-digitals. like most everyone in the post has said,...analog will work fine. Keep it in the smaller stuff,....no point by todays standards to use them in anything bigger. If your expectation is max preformance,..digitals all the way. If you just want to fly around and thats all some guys want to do,...analogs are fine,.use 130+ ounce minimum (JR make s a nice servos ST-126 I think??,..162 ounces on 6.0 volts and I can buy them at the hobby shop for about $33 bucks.


Best of Luck,

Bill Holsten

Advantage Hobby Fliton Field Rep/Custom Airframes of America/Dragon Fire Customs/Desert Aircraft/Carden Aircraft/JTEC Radiowave/Guardian America. NSRCA, Dist2 FAI/F3A/IMAC Unlimited,.not active.

Ed Alt,...the dual reg's work AWESOME!,...Thank you!


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Old 08-28-2009, 12:29 PM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

Thanks very much for taking the time to answer this question. I really didn't see the advantage when I started comparing, but now I see how digitals are the way to go. I could not find any problems while flying some aerobatics using analog and compared the torque, response time etc between analog and digital servos. This was educational. Thanks.
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Old 08-28-2009, 03:45 PM
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Default RE: Is it necessary to have digital servos to be successful flying pattern or IMAC?

Right on!
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