cyborg1

Hi, I fly glow planes and I'm just about to start electric flight. I have a foam Reaction ep jet that I just bought. Weight of the kit alone without batteries, motor, speed control and servos is about 500 gms. I'd like to ask for recommendations on what brushless motors, speed control, and batteries that should be used with this plane. I'd like to get the most speed out of it. The LHS recommended a 1300 kv motor with a 40 amp speed control running on 3 lipo cells. However, since this plane is one of the first manufactured, the recommendation from the LHS might not be spot on. What I'd like to know is:
1. How many KVs should be used for the motor? (keeping in mind that I'm aiming for speed)
2. How many amps should the speed control be?
3. Using 3 lipo cells, how many milliamps and Cs are required for speed and longer flight times?
4. What prop should I use for speed?
Thanks for your advice!

FlynFoam

My Feedback: (1)

I'm thinking something rated at 1600 - 1800 kv outrunner with a 5.25 x 4.75 prop. 20 to 25 amp controller and a 3S lipo rated for 20 amp continious discharge.
That should move it out pretty fast.[X(] Some speed, not much torque. Just make sure the motor is rated for 3S lipo and 16 to 20 amps.

Is this a pusher type jet or will the motor go on the nose?

Can you post any photos of the model?

Dr Kiwi

How is the motor mounted? - a 28mm inrunner in the tail might be easier than trying to fit a larger diameter outrunner.

cyborg1

Hi, the motor is mounted in the nose of the plane. I've tried a 1600kv motor with a 30 amp esc and 3s 2200 lipo pack. First flight was with a 8x4 apc, but no real speed, and longer takeoff roll. For the second flight, I switched to a 8x6 gws prop, and takeoff was almost immediate. No real speed tho. I'm going to try a 7x6 prop to see if I can get more speed, or a 7x8, which will need to be cut from a 10x8.

cyborg1

the 7*6 prop didn't have ant speed, so i tried an apc 8*8. speed was better, but after flyibg at 1/2 throttle for about 2 minutes, plane lost almost all power. probably was drawing too many amps. will use a 40 qamp esc to see if it will work or not. would it be better to use a higher kv motor and smaller prop? there's a stealth at my field that screams and goes really fast, but it's a pusher.

Dr Kiwi

It is no use fitting a larger (40A) ESC if you are, by your own admission, drawing too many amps with the 8x8... you'll fry the motor just the same.

If your plane is only 500g dry... then you can probably use a smaller, higher Kv motor with a smaller prop... something like a Suppo 2212/6 (~2200Kv) with a Zagi Carbon will get you: 10.8v, 17.80A, 191W, 19570rpm, 90.8mph, 565g, 19.89oz, 2.96g/W

If you want crazy speed a Grayson Super Mega Jet (2200Kv) on 4s and a 4.75x5.5 gets you this:
12.7v, 27.0A, 344W, 4060rpm, 125.3mph, 544g, 19.16oz, 1.58g/W

or, with a Graupner 6x6 CAM on 3s:
11.0v, 37.00A, 401W, 18720rpm, 106.4mph, 789g, 27.78oz, 1.97g/W

cyborg1

Hi Dr Kiwi, I just changed to a 2200kv motor and tried a 7x6 and 6x5.5 (both apc e). The 7 flew, but speed wasn't that great. I didn't even try to take off with the 6 inch prop as it seemed that thrust was not enough. I went back to the cutdown gws 7x7.5, and it seemed all right, but not much of a speed increase. With this motor and a 3s 2200 lipo pack, it was drawing about 33 amps at full throttle, using a 40amp esc. The battery pack was warm to the touch about about a 5 minute flight, flying at 1/2 throttle, with a few speed bursts in between. I don't know if I can get it any faster than this, but I would really like to. Attached is a picture of the plane that it was modelled after.