andy86na

My Feedback: (3)

I still have a stash of HS-5955MG's. They put out >300oz of torque on 6V. I believe 40% planes need about that much per elevator half, right? The question is, if I use one servo per half, will the elevator twist be a problemeven if there is enough torque?

I am building 40% TOC yak-54, if that makes a difference.

bubbagates

My Feedback: (32)

Two of the main things that determine servo power is weight of the plane overall, with fuel, and the intended use. I would say 300oz is close minimum and on that size plane, you never want minimum. I tend to go over be at least 25%. Also, if you are going with long servo arms, you will lose torque if you use the farthest out hole which a lot of people do to get max throws

Zeeb

My Feedback: (41)

Two other issues with your plan; if the model is setup for dual elevator servos, it not only has to do with the required torque but to some extent the flex of the elevator. While not as great as an aileron setup, it's still there and the structure may require multiple attach points. The other issue is that while the 5955's were pretty good servos, extensive testing by some third parties indicate that when warm the torque output (all servos lose some torque when warm) fell into the neighborhood of 240oz.

Besides other improvements, the 7955's do not suffer this type of drop in output when warm and the 7950's seem to have some issues showing up particularly with un-regulated Li-Po batteries or long servo leads seeming to contribute to the issue some users are having, but Hitec has not indicated any real solution for those who are saying there is an issue. With that in mind, if I were to pick a servo in the Hitec line for your application it would be the 7955's....[8D]

krayzc-RCU

My Feedback: (31)

i have a 40% Radiocraft Extra that has 2-8411 on each half. So that is about 380 for a total. now that better torque is out there flyers are using one servo on the RadioWave with great results. I will change mine out to one servo in the coming years. either 8711 or 7950 or so.

RichardGee

My Feedback: (156)

It is totally dependant upon the type of flying you and your aircraft are capable of.
Unless you will be flying your aircraft competively in IMAC beyond Basic, OR you will be doing 3D (not just trying to hover, but serious 3D), then multiple 300+ ounce servos on each surface is overkill.

I would agree that a long built up aileron should have two servos just because of the potential flex, but for elevator, it is not necessary unless you will be flying in the manner I described.

Keep in mind also, this ASSUMES you will not prop you aircraft for jet-like speeds! Speed can and will produce flutter, which will defeat 1 servo easier than it will defeat two.

A composite aircraft will not require as many servos on each surface due to its stiffer construction.

IF you have the potential to really tax your airframe then by all means, go with multiple high powered servos and play it safe.

Zeeb

My Feedback: (41)

Bill might have some differing input/thoughts on that statement and his experiences posted on a Comp-Arf build thread is why my 2.6 Comp-Arf has both servos installed in each wing rather than a single high torque servo as some use on that size Comp-Arf.....

Another set of issues with this question showed up on FG with regard to the PAU 43% Edge which came out with spots for 6 aileron servos and 4 elevator servos. After some issues with the wings on that model, PAU replaced all the wings and has said that if all the required servos are NOT used on ALL the control surfaces, they will not honor the warranty on the model.

JMHO.

bubbagates

My Feedback: (32)

Zeeb

You are correct. I will argue that statement anytime. Yes, the C-Arf's have stiffer aileron, but what about the LOAD on that single servo. Let's take a 40% C-Arf running 2 servos per wing, in the root as they are by design. Yes it works, now toss in a very violent snap and after a few of those, the servo(s) will strip. I've seen that happen more than once. In mine, I run the optional outer servo.

OK so now let's look at a 28lb (+/-) 2.6M. Same thing, you are placing all the load onto one servo. Yes torque will make a difference as well as running a Titanium geared servo but are you will to risk an expensive airframe to save roughly 5 ounces in servos by removing one per aileron. It's simply not worth saving that amount of weight versus the cost of 2 more servos and possibly having to replace a very expensive and well flying airframe

Folks, think safety here. You need to remember that you are now flying something moving around 70mph at 28lbs and turning a 27 inch prop. Is saving that few ounces worth it, not to me.

Yes you can save in certain spots but the way you expect to fly and the weight of the plane MUST be taken into account. Overkill is never a bad thing, in the long run you will be better off

My 2.6M (30lbs dry)setup is as follows 4 aileron servos (Hitech 5995's) Elevators (8611's, one each) Rudder (8711 one only) This setup has not changed since I built the plane, other than replacing gears on the elevator and rudder about every 100 flights. Typically for IMAC style flying 50 to 75 flights is the norm, since I'm into overkill, and my mechanical setup uses short servo arms and not needing a lot of throw, then my gears last longer. Plane is well over 1000 flights

My 40% Carden is setup as following, remember this is a Carden and the required amount of servos are installed, just about 25 percent more torque for each servo. I am just around 200 flights on this plane 2 8711's per aileron, 1 8711 per elevator, 3 8711's on the rudder. All servo arms are 1 inch arms. Plane is right at 38lbs

The white plane is the 2.6M C-Arf. The red and white one is the 40% Carden

Only the C-Arf gets any 3d and that's mild at best because with the short arms there is not a lot of throw

camss69

My Feedback: (46)

I would not run 5955's by themselves not enough torque.

I've run JR 8911's by themselves on a 42% Dalton Extra 300 and they did great.

rodney tanner

Taking the above comments into account for a 42% set up.
What is the conventional wisdom on using single aileron 7955s or 8711s on a 35% - 100/120cc IMAC Intermediate set up at around 26lbs?
Thanks in advance

andy86na

My Feedback: (3)

Made up my mind. Going with two 5955's servos per elevator. Too close to go with one. Maybe on a fully sheeted (stiff) elevator with an HV servo that puts out 500 oz-in one would be just fine. Not 5955's. Thanks all.

krayzc-RCU

My Feedback: (31)

good deal nothing like putting your plan in place