bob8619

Yeah its 6 volt. I don't think I need all that torque, the manufacturer suggested servos produce 58 oz-in at 6 volts, $10 cheaper and I have 57 oz-in at 6 volts. I must be missing something?

I_Fly

Consider other specifications from the recommended servos. Many folks would insist that a gas powered model requires metal or carbonite gears. The extra vibration can fatigue and break regular nylon/plastic. I don't know if this advice holds true for some of the smaller gas engines but this model is good sized and it would be a shame to loose it because the servos were not up to task.

kiwibob72

Bob8619, digital servos perform better re centering and all that Vs analogue servos, end of story.
If your running the optional E-Flight electric (digital) retracts, I'd stick with digital servos all round on that plane as it's not desired to run both digital and analogue off a single RX.
With regards to power supply systems, and the shear amount of amperage that can be drawn by using large numbers of digital servos (the retracts have a fail safe built in to them), a twin battery redundancy system like this (http://www.hobbyking.com/hobbyking/s...utor_RED_.html) should also be considered I.M.O. (I'll be running that in my H9 Blue Nose Mustang which has a total of 9 digital servos in it - each retract has it's own servo). As that new P47 is heavy for it's size (as previously discussed), ensure you have a strong elevator servo if nothing else.
On a side note, when it comes to component selection, I'd look at it this way. You have a very nice higher end 60 sized ARF kit. Your going to put into it a very nice high end 4 stroke gasser into it, so now we are looking at something that is starting to resemble a seriously nice high end quality plane. Would you want to lose it as a result of scrimping on something as crucial as servo choice?? High voltage servo's that are designed for 2S LiPo's are an good option as it can limit extra components like voltage regulators, and obviously handle the amperage demands of modern digital servos.
You model is just a 'system' of components working together to achieve flight. If part of that system is weak or substandard, then the whole system will inevitably go down ..... and in the case of expensive gas powered aircraft models, that often ends up in a pile of flaming bits on the ground.

rcguy59

My Feedback: (8)

No warbird NEEDS digital servos. Warbirds don't need as much torque as an equivalent size 3D bird, either. Since warbirds tend to have a larger number of servos, adequate battery capacity and voltage are still a must. As an example, my 20cc Ki-61 Tony has 8 servos, plus electric retracts. The RX battery also powers the ignition module. A 6-8 minute flight only draws an average of 90 mah from the battery (2500 mah LiFe) Digital servos do center very consistently, which is why I like them on the throttle. Other than that, I see no need for digitals unless you just HAVE to have them and don't mind paying the extra money for them.

bob8619

Absolutely not. I just cannot see how they can suggest a certain servo that wouldnt work. If their suggested servo is plenty good for this plane, how could a servo that is .05 seconds slower and 1 oz weaker be a problem? I fully understand now what makes digital high end servos better, but the two I am comparing are so close to being the same .

dirtybird

My Feedback: (5)

The opinion of many is digital servos are more reliable than analogs just because they cost more. Actually the reverse is true. Analogs are more reliable simply because they have far fewer parts than digitals. Digitals have a smaller dead band and center better at the cost of higher price and higher current draw. If you need better centering get the digitals.If yo dont you are better off with analogs..

Bozarth

My Feedback: (15)

Get the newest servos you can afford. The newer technology is better than the old, unless you are an old f**t.

Kurt

mr_matt

My Feedback: (10)

The torque specs are for stall. The analogs won't hit stal until they are maybe 15 degrees away from the commanded position. A decent digital would be 10 times better. Digital and analog can't be compared with stall specs

kiwibob72

Your looking at putting a larger (heavier, and more powerful) motor option into your plane over say a .90 or 1.10 4 stroke nitro (if you go with the 20cc gas option as discussed). The end result is it's going to be a little heavier, and secondly faster than the a fore mentioned nitro options. More speed = more load on a given control surface at equal movement.
While your slightly slower and 1oz weaker analogue servo may well work and be more than strong enough as war-birds control surfaces are tiny when compared to an equivalent sized aerobatic plane, we are now talking about mixing analogue and digital equipment (the e-flight retractable landing gear it's designed for), which I feel we could all agree, is not a desirable option in a perfect world. That's my only concern in fairness.
For reference, my nitro heli has fast and powerful digital servos all round as that is what is best suited on that type of model. My 57" Yak54 (aerobatic plane) uses analogue all round, as they are enough for that plane and the type of flying I wanted from it (sport/low-wing trainer only). My H9 P51 with the DLE20 in it has metal geared digital's all round and will use a twin battery power supply for piece of mind on my part (that 'system' mind set of mine), and lastly, my 30cc Sbach aerobatic that is waiting for me to get it out of the box. That thing will run twin power supply, high voltage metal geared high torque digital servos all round as that is what I want to know it'll do what I want when I want without question (ie that 'piece of mind' thing again!)
In a nutshell, each model is set up with it's intended use/size/power demands & weight in mind. While I personally have no issue over-specking a servo, I've never really liked the idea "just enough" from a component. Sure, all up flying weight of a model is a factor in any decision and that can be effected by our choice of components, but a few extra grams on a "well powered" model is not going to kill it.

Hossfly

Mr. Bob, I have been in RC a long time. Even owned a Hobby Shop for some 9 years in Mt. Prospect, IL. I was an ardent CL Stunt and Free Flight competition flier until the early '70s.
Had to learn RC as I was trying to sell the stuff. What that means is this industry, especially after the late '70s to into the '80s, RC sellers were definitely pushing fliers to have the latest and newest thing. They still are. There are folks that just have to have the latest and newest and they will tell you that it is a must. Well I have a number of digital servos in a case in my larger workshop. Never used one. When I get to doing some of my dozen+ wood kits of over 100" wingspan I will probably go with digital on ailerons and elevator. Digital gives one some extra snap and is quicker BUT it eats up battery VERY QUICKLY as compared . Good size analog is faster than me on the draw and is much easier on the battery. I do use some Lithum Ion battries. Stable and don't tend to build campfires which I have seen a lot of those "other things" do!

Our younger folks just have to have the latest thing. So be it. For a .60 - .90 size toy airplane, analog will serve you very well. Anything over 48# torque will fly you well providing a separate servo for each aileron. My 101" ws Eindecker gas burner has no problems with rather small analog. The rest is your choice. I use 1 60# or better for elevator and standard analog for everything else. Never a problem other than all those folks that think I am wrong, but I care not. My models just grow old. Every so often I cut one short, but that is never the servo's fault !!!! HA!

bigtim

My Feedback: (13)

I have several H-9 60 size Warbirds and use Futaba 3004 servos on all surfaces, they work fine for the size range unless your burning up the sky with a over powered plane that range is fine

cbooth1979

My Feedback: (22)

JR 821HV's are $30 ea and have 75oz of torque with 2s lipo,..and there digital? Seems like kind of a no brainer to me.

Airplanes400

My Feedback: (349)

We as humans, cannot even realize or comprehend what .03 of a second is. It's 3/100 (three hundreths) of a second. Humans cannot even speak a single syllable in that amount of time or do anything in that amount of time. We don't move the joy-stick any significant amount in three hundredths of a second! The only thing that can measure that amount of time is a computer. The human response time is .6 to .7 (6/10th to 7/10th of a second). For anyone to tell me they can notice the diffeence in the response time, is just their imagination. Digital simply uses smaller measures of position than analog does.

Here's a test ...
Try tapping your finger on the table thee hundred times in a second. You'd be lucky if you could do it 5 or 6 times, because 4 to 5 is average for us humans.
Not even the fastest military machine gun can fire 300 rounds per second ... that would be 18,000 rounds per minute!
So, as humans, 3 hundredths of a second is out of our comprehension and ability to perceive.

The only reason you see Specktrum servos being mentioned by Hangar9 is that Hangar9 and Specktrum have an agreement to co-market their products.

Analog servos will be fine. I still use them in my jets. Back in the 80's & 90's, all we had were analog servos with 48 or 72 oz of torque ... They were fine, and provided plenty of torque on any control surface. Plus, the BVM ducted fan jets were clocking 210 mph back then.

So, why do we suddenly need new and higher (300 oz torque) servos? Because the manufacturers are only pushing the digital & higher torque servos as a means for them to stay in business. There is no real benefit ... only perceived benefit.

It's just like the new & better speaker systems that are coming out these days ... They have a lower and higher megahertz range than the human ear can register. What's the point in that? So our dogs and cats can hear things that we dont while we listen to our music?!!

And the refresh rate on computer screens & TV's are also faster than the human eye and brain can register. What's the point in paying twice as much for that when we don't even see it!!!!

bob8619

Thanks everyone for your advice.

Kiwi, what is the harm in mixing analog servos with electric retracts?

j.duncker

My Feedback: (2)

No problems in doing that except you must have a separate battery pack for the retracts in case they jam.

bob8619

Oh I had guessed that they used the same battery as everything else

hogflyer

There's no issue running analog servos with electric retracts. If the retracts are pneumatic or mechanical then you want to match the servo to the rest - either analog or digital. What you don't want to do is run a mix of analog and digital servos, especially doing an analog servo on one aileron and a digital servo on another. - keep your servos either all digital or all analog.

One thing I haven't seen discussed is what radio and receiver will be used? If you flying Airtronics and want to use an FHSS-3 receiver then you have to run all digital servos. Spektrum DSMX from my experience does great with either analog or digital servos.

For most sport and sport scale flying up though .60 size standard analog servos work fine. I'm flying a Twist 60 on Futaba S3004's and they have more than enough power and speed. Servos like the S3004 probably have over twice the torque of the servos we used back in the late 70's for sport, scale and even pattern flying.

Hogflyer

PHall

And also where the torque is measured in the stroke of the servo. You should look at the torque curves. Digital is exactly that. On or off. Analog varies its torque through its range. Digital is all on or all off therefore much stronger through its range.

bob8619

I'm going with my Futaba S3003's since I have them. Worse case I'll just buy better ones down the road if I for some reason think they aren't working right.

Ok, so, for the eflght retracts for this plane, it requires its own battery? So if I go with gas I'll need 3 batteries?

hogflyer, I have the Spektrum Dx7s. Which comes with an 8 channel rx for some reason? Do you or anyone else by chance have any experience with these?

dogshome

Just chipping in - 7 standard size servos are a lot of weight load in a 58" plane. I'd be looking for metal-geared mini servos on ailerons, flaps and throttle personally. Also elevator if there are 2 servos on it. This has been successful on my 72" 15cc petrol Hien.

Sorry, didn't spot posts on page 2! 3003s fine.

I use 2 batteries. 2300 LIFE for retracts and radio, 4 cell NIMH for ignition. My theory being that if the retracts jam, the current available will either clear it or burn it out before the volts drop low enough to drop the radio. I'd rather have a light airframe and easier handling.

Have used combined LIPO and dual regulators for ignition and radio with success on aerobats (fixed undercarriage). Have not tried 3 ways though.


P.S. DSMX AR8000 receivers very reliable.

bob8619

Good info thanks.
Any idea why the dx7s comes with the 8 channel receiver? Can I somehow utilize aux3 for flaps?

dogshome

I doubt you can use Aux3

Don't know why it comes with an 8000? I've bought a couple of these Rxs split from transmitter kits - I have no idea why they do that?

HoundDog

My Feedback: (49)

Just go for it if the servos don't stand the load ,,,, They make new ARF every day. No one crashes just one if they stick with this hobby for any length of time. We have a guy we call Dollar Bill ... In the year and a half he's been in our clube he's KILLED more than 20 planes. Last time he was out he killed 2 on friday and 3 on Saturday. Not cheep park flyers. One was a Electric 110" Taylor Craft. His comment is he ordered 2 of each and had spares at home.

BarracudaHockey

My Feedback: (11)

You can't use Aux3 for anything but a battery input with a 7 channel radio.

Digital servos produce 100 percent of their torque immediately and use it to hold the surface into position, whereas someone already said, analogs don't produce full torque until they nearly get where they are going.

As for 921's, Spektrum says not to use them on gassers

bob8619

If I crash it I guarantee it wont be because I didn't use digital servos