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Power System for SU 35 twin EDF

Old 03-08-2006, 09:29 AM
3drc tim
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Default Power System for SU 35 twin EDF

I put this under "EDF/Jets" and it just bombed. Any help or thoughts would sure be appreciated. Thanks, Tim

I am building the Walkera twin EDF SU 35 (27 with canards.) I have read some other threads on this plane with upgrades on the airframe but not much consideration for the power system.

Weight (AUW) 32-36 oz.

75 mm EDF with 5 blades prox. 3" x 4.4" (pitch guesstimate)

Prefer 1-1/2 to 1 Power-to-Weight ratio, or low 16 to preferred 24 oz. thrust per motor

WS 42.5 1080 mm, WA prox. 300 sq. in., L 940 mm

Prefer less than 20 amp operation, but will consider up to 31 amps for use of 1 for each EDF, 2S or 3S 2100 15C battery per motor.

I bought mine at the WRAM show from They recommended upgrade motors of around 3200 KV to replace the Speed 400's? included with the kit. The plane is reported on this and other sites as a real draggy airframe with stock top speeds of 40 to 50 MPH. I want to go at least 80 to 100 MPH. The BalsaPR recommended motor is a MTM 400F outrunner motor (KV?) driving the Walkera 3" diameter 5 bladed rotor. Based on the EDF 75 – 4 blade 4.3 pitch and 6 blade 4.5 pitch from GWS, the pitch on this rotor is probably 4.4". Thrust and other information available on the Walkera EDF unit is limited. One site recommended using a Hyperion X22-S motor with this fan as it is used on the EDF 50 and 64 GWS units; but this seems too small (300 size.)

AT LAST the question(s)—can I make a pair of EFlite Park 400 3700KV or 4200KV motors work and get up to 24 oz thrust per motor? I am thinking that inrunner motors are the right configuration for this because of KV; would outrunners really work well on a ducted fan? Or what motors will I have to use to achieve these objectives?

Any help would sure be appreciated. I just do not want to have a mild mannered, slow flying, jet fighter of this distinction.

Thanks, Tim

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