I am building a Sig Senior (not an ARF). I will covert it to a tail dragger but otherwise is will remain pretty much stock without ailerons.
I think a G-46 Turnigy would fly it just fine so I ordered one with some 5s 5000 batteries for long flight times. http://www.hobbyking.com/hobbyking/s..._46_glow_.html
Then I thought and was told that many fly with a G-60 so I went ahead and ordered one of them too. If I don't use it I will someday so it's not a big deal. http://www.hobbyking.com/hobbyking/s..._60_glow_.html
But I read on the Turnigy site that the 60 with a 13 x 8 prop will pull 47 amps and give 2850 thrust.
That should be 869.5 watts according to the math. Now that is the only prop they show it with an 18.5 pack so I donít know for sure what other props would do.
The 46 is shown best using a 15 x 8 prop and the 5S for 3150 thrust (even more) but drawing 44 amps so the draw is about the same. Math shows 814 watts.
So it appears that with the 5S batteries that I ordered I will not gain much using the 60. My Plush 60 Turnigy ESC only support a 6S pack also so I may just opt to use the 46.
At present I donít see much advantage with the other components that I have to using the 60 I have coming. I can only go to a 6S at present anyway as my battery charger is only designed for a 6 so I do have some limiting factors based on what types of batteries I can use and my charger.
Oh well, I can run some prop tests with both the 46 and the 60 on the bench on the shop and see what wattage I get on the meter.
I guess it's time to see what the watt meter shows on the bench with the two motors and some different props.
Lessons learned I guess.
Both Motors Will Do A Great Job of powering your Plane, the 46 motor is a 420 Kv Motor and the 60 is a 500kv motor, the 46 can be loaded down more with a big Prop because of the lower KV, the 60 will IMHO with a 6 pitch prop will give you longer flite times, you dont need a 8 pitch prop for a Sig Senior, The 60 motor with a 500KV and a 6 cell is right where I like to Be at, with 1000kv motor on a 3 cell, so 500kv on 6 cells is the same thing, and with a 6 pitch prop will work great,the amp draw will be lower and flite time greater too, Just My 2 Cents worth, Chellie
I am already regretting ordering the 5S batteries but they will be enough to fly this plane.
Should it survive (I am tough on things that fly) I may just move up to a 6S.
Sure is lots to learn about electric motors and props.
And I thought learning about radar/sonar and the like for the Navy years ago as a civilian was tough!
When you get to the larger models, selection of the power equipment becomes more important for a model that will fly well. Nice thing about electric power, its not hard to match the power of a glow engine with quality electric components. The electric versions properly set up will fly perhaps 6 minutes or so with a 30% reserve, as compared to a glow or gasser model that can fly several times that long.
On the other hand, methinks your model could be flown with a big wind up rubber band :D :D :D
Just about any reasonable power system that will put out about 100 watts per pound of airplane will fly your model.
You've made a giant advance in this electric stuff, that being your wattmeter. IMHO, trying to put different props and battery packs on an electric motor is similar to trying to drive a car without a gas gauge, speedometer, or anything else.
These electric motors are DUMB. To small of a prop, and your model won't be able to take off. To big of a prop, and your motor will put out gobbs of power. Until you get the magic smoke. That's where your wattmeter comes in. With it, you'll quickly find out if your motor/ESC/Battery pack is running at its most effective power range, without the risk of burning it up.
As for ailerons on your model, you might consider building the wing with ailerons, and rig up something that allows the ailerons to be fixed in place. That way, if you should want to convert to ailerons down the road, its just a matter of sticking in the two servos, and you're done.
Here is a whole bunch of reading material on these intermediate sized electric conversions.
Thread on 70 size glow engine conversion to electric
Hacker 6S2P A123 powered Models
Hangar 9 Kantana Model
Hanger 9 Twist 40 Model
AEAJR's Site on Electric Power
BEC Linear Current Rating
Is there a design calculator, maybe motorcalc?, that I can plug in values and props that will give me some answers? It would be nice to know in advance what I am getting into before I order and screw it up like this order.
Give this a try:
For the complete website:
It's been a pretty good starting (estimator) source.
TNX, I will give them a look over.
Motocalc is good, at least as good as the specifications provided by the motor supplier. Problem is, some of those cheap brushless motor specs are not worth the paper they are written on.
What I've done is use motocalc to compare to an existing brushless motor and prop. Then, if they don't match up, tweak the brushless motor KV spec to the RPM does match. That way, selecting another prop will get you a bit closer to what motocalc predicts.
I've found that even some of the name brand motors can be way the heck off in their specs. One required going from a 6S A123 battery pack to an 8S battery pack to match the the so called KV specs of that motor. That motor was a name brand. (Not Hacker. FYI, my 8 Hacker motor specs are pretty close.)
I am going to purchase a few sample props as I have nothing that big in my stash and try to two motors with the batteriesand see what real world is on the bench with the watt meter.
It may not tell me everything but I wouldn't know what to do with everything anyway.:confused:
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