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Choose an electric power setup?

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angry_muppet:
I know it was suggested to keep the Euro Trainer I'm trying to get flying as an IC model...  But as I'm new to the whole hobby, I'd like to stay clean with electric, at least at the moment.  When I have more money (i.e. in 40 years when I'm retired...) I can go IC then!  ::)

Anyway, how does one choose from the plethora of options on our favourite Hong Kong site?

The EuroTrainer stats are thus:

Wingspan:1500mmMean chord:290mm (or thereabouts)Wing Area:43.5dm2"Empty" weight:1.6kgExpected "flying" weight:Approx 3.0kg (~400g motor, 900g battery, 100g wires etc)Wing loading:approx 69g/dm2 (22oz/ft2)
Using google, it suggested this http://flbeagle.rchomepage.com/software/webocalc_1.5.2/html/webocalc_metric.html.

This calculator suggests (using a 6s battery, chosen so I could use one pack across several models in my "Dream hangar"):

20C30CMotor900kV760kVProp10x510x5ESC70A60A
Would that seem to be in the correct region?

What would the effect be if I use a higher "C" rated battery with the low "C" setup?  Would it just be less stressed?

EI1638:
I would have expected the higher C to be associated with the higher current setup. What's missing from the info is the motor wattage. It's usual to derate the ESC (electronics don't like heat), and to give substantial overhead in terms of the esc.e.g. estimated peak current 50 A,  esc rsted 75 A. In many electronics designs it's not unusual to derate electronic devices by 50%, and sometimes more.

Based on the weight it looks like you need a 400, 500W system, as in the battery needs to be able to supply 500 watts for the expected flight duration, without damaging itself, the ESC, or the motor.

An example of a suitable system is the power pack for the Multiplex Acromaster. If I recall correctly this is around the 450 W mark, runs on 3S batteries. I'm not saying buy this as it is kind of expensive, being multiplex, but it is an example, with battery recommendations, of a motor, prop and esc that will provide what seems to be the right amount of power. Once the battrry and esc are sorted I find I sometimes replace the motor with a higher KV motor after a few flights. That would be because I dont want to overload the motor by moving to a higher pitch prop.

Chris

Happy Days:
A wing loading of 22oz/sq ft is a bit heavy for a trainer David. :o Ideally you'd be looking for no more than 15oz /sq ft. ;)

What size prop is on the model at the moment?

Keith

angry_muppet:
As is, the plane is a OS Max 40FP on a 10x6 prop.

Am I correct is assuming that a 1.6kg "empty" weight is realistic?  Obviously weighing on kitchen scales isn't the most accurate for a model plane...  ;D

The setup I was looking at was:

5000mAh 6S 40C http://www.hobbyking.com/hobbyking/store/__9965__ZIPPY_Flightmax_5000mAh_6S1P_40C.html
800W motor http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=17354
or a 1350W is cheaper? http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=18171

An ESC can be bought to suit when the motor and battery is sorted.

goreyflyer:
I have a sk3 motor in my 73" exrtra flying on 10s and its very good.

How about the easy match range:

http://www.hobbyking.com/hobbyking/store/__19028__Turnigy_G46_Brushless_Outrunner_420kv_46_Glow_.html

Fly on 5s

The higher c rating is needed for 3D and helis!
We use 20c on f3a planes!!

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