Was hoping someone might briefly explain something to. I am relatively new to electrics and have a P-38 that I am thinking of converting. I have read in the Conversion forum threads pertaing to the conversion I would need, but am dumbfounded on why such a big pack and prop are needed. The 2 conversions I have seend are: 1. (I used 2 AXI 4130 16, 77 amp lithium supported speed controls, 3S4P8000 x 2 thunder power packs on each motor. 15X10 props pulling 42 amps) This one said he could get a run time of around 30mins 2. (It has AXI 41/30/16's, CC Phx 60's, Master Airscrew 3 blade (counter rotating) 16x10 cut to 15", TP6s3p6000ProLite's each side) This one has not stated a run time.

Now my questions, Why do you need such a large prop(15x10)? This plane calls for .40-.46 2 stroke glow. Mine has .60's in it with 12x6 3 blade props and flies great at 16lbs.

Also if you wanted a run time of only 10-15min, could 1/2 the battery size/pack? Say a 3S4P 4000 x 2 per side?

Thanks
D

Mr D ... EP motors usually turn at lower RPMs but its got torque, so the props are bigger and with a coarser pitch. What recommended to you is a lot of power. An AXI 4130/16 on 6S has about the same power as a 90 sized 4C. You plane is 16 lbs and if you take that set up we are taking being able to pull amazing verticals. Do you want to fly scale? Also, flying for 15 mins is a little much for scale EP planes such as warbirds.

I believe you can run with an AXI 4120/14 and 5S even. With 5,000 mAh packs you may safely touch 10 mins for scale flying. With 5S you can exhange volts for mAh and get more flying time.

The prop size depends on the motor you choose. In general, lower Kv motors will need more prop loading than higher Kv motors to pull enough current to get max power output. Low Kv motors have high torque and spin at lower RPMs, so more prop loading is required for max power. High Kv motors have lower torque but spin at higher RPMs, so much less prop loading is required for max power. The equation for prop loading is as follows:

Prop Loading = (Length^4) x pitch

If you want to use smaller props, you should get higher Kv motors with similiar power ratings.

As far as getting a smaller battery for shorter flight times, that works fine, just scale the mAh rating down for a proportional reduction in flight time. However, you must be sure the current rating of the smaller pack is high enough for your power system. For example, with a 77A current draw, you'd need a 8000mAh pack rated at a 10C discharge rate (80A), but you'll need a 4000mAh pack rated at a 20C discharge rate (80A).

TianCi are you suggesting to use only 1-5S1P 5000mah pack per motor? I would love the vertical, who wouldn't. My problem is, I am new to Electrics. I have this airplane that I am considering to convert as well as some small DF Jets( 1 uses a 3S1P 3000mah, the other a 4S1P 4000mah). So to spend $1500 on battery packs that I might possibly only use in this P-38 has me nervous.

So a more basic question, What would a great conversion be for a .60 2 stroke Nitro engine be? Wanting the same speed and power I would get from the 2 stroke, and run times of around 10min.

Thanks
D

<span style="font-size: larger;"><span style="font-family: Comic Sans MS;">VooDoo ... sorry not a pack per motor, she will be a real porker. With two motors, a 5,000 mAh pack may get you around 8 mins of flight, perhaps 10 if you fly her scale. </span></span>