BOMBERGUY

My Feedback: (5)

Hi Guys,

First off let me say that I don’t know JACK about electric power. Second, your advice is not only for me but also for one of our customers who would like to use electric to power the model.

Details about the kit: It’s a Jack Stafford B-24D. I have built (Lawn Dart), and I’m finishing up a new glow powered one right now (almost done). Power is supplied by 4 Satio 30, 4 cycle engines. Dry weight will be about 16 pounds, wing loading is high (wing area is 740 square inches but it does have flaps). The Satio 30’s are plenty of power for the plane. Max diameter for the props are 10 inches due to nacelle spacing, scale props would be 9 inch 3 blade props. Lipo batteries are not out of the question.

OK guys, have at it. Remember to keep it simple. Like just tell me what’s need to be purchased to convert this kit to electric and I’ll past the information on to our customer.

Thanks,
John
www.JSModels.com

Greg Covey

Hi John,

Converting to electric power is quite simple and you have provided great information.

First, knowing the all-up weight of 16lbs, we will probably want 75-100watts per pound where 750 will fly the B-24D well and 100 will fly it awesome! Simply multiply 75 x weight of 16lbs to get 1200watts minimum and 100x16 for 1600 watts maximum.

Second, divide your total power by the number of engines (or motors in our electric case). 1600w/4 = 400 watts max. per motor.

You mention that Lithium packs may be ok but you didn't mention if brushless or brushed is better. Let's assume a brushless outrunner for a direct drive maintenaince-free solution with high efficiency.

Depending upon the space in the nacelle, you should be able to use a rotating can motor like the [link=http://www.hobby-lobby.com/brushless-axi2820.htm]AXI 2820/10[/link] motor with a 3-blade 9x6 prop or 2-blade 10x6. A 3-blade 10x6 prop could also be used with proper throttle management. You can use a 3-cell Lithium pack that can deliver 30amps continuous or a 10-cell NiMH pack. If you use a [link=http://www.hobby-lobby.com/kokam.htm]FM32003[/link] 3-cell Kokam 3.2AH pack, you can power two motors per pack since it can deliver 64amps continuous.

You will need one Jeti 40-amp brushless controller per motor and then you can "Y" cable the control lines to the receiver throttle channel. I would recommend using a receiver battery for this application but you can alternately connect one of the ESC's BEC supplies to power the receiver and servos. You'll need to disable the other three ESC's BEC cables by cutting the red (or orange) wire on the control cables.

With electric flight, you have great design flexibility and unparalleled reliability.

Good luck!

BOMBERGUY

My Feedback: (5)

Hi Greg,

Thanks for all the information. It's just what I was looking for and I'll pass it on to our customer. I may even take the one I'm building for our web site build and convert it to electric power.

Thanks Again,
John
www.JSModels.com