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Dupe Winger
06-16-2007, 03:15 PM
I have a Jack Stafford B24 kit which I would like to build using electrics. I would like to have some help on what size motors and ESC's as well as what battery arrangement I would use. I do want to set this model up with retracts , operating bomb bays and bomb drops as well as flaps. The full scale effect.
Any assistance on this build would be greatly appreciated.??

Sky Sharkster
06-16-2007, 06:04 PM
Hello Dupe Winger, Welcome to Wattflyer!
Some of our readers may not be familiar with the larger (normally) glow kit manufacturers, so I've included the specs for the Jack Stafford Models B-24 "Liberator":
Power Class; Glow .20-.39 (4)
Wingspan; 90.0 Inches
Wing Area; 740.0 Square Inches
Wing Loading; 28 Oz./Sq.In.
Length; 54.0 Inches
Weight; 10.50 Lbs.
Airfoil; Not Specified
Min. Channels; 4, Servos; 5
For a start, I'd say 4 of the E-Flite 25 brushless outrunners, each with a 40-45amp speed controller;
http://www.e-fliterc.com/Products/TechnicalSpecs.aspx?ProdID=EFLM4025A
If the addition of the operating features adds several pounds, you might need a larger motor size. These would require (4) 60amp EScs;
http://www.e-fliterc.com/Products/TechnicalSpecs.aspx?ProdID=EFLM4032A
And (for each motor) a 3s or 4s LiPoly of about 3000mAh-4000mAh. If you could get a 4s Lipoly with 7000 mAh or higher, you could use one of these for each set of 2 motors.
This would be a pretty expensive set-up!
Hopefully, you'll get some other suggestions.
Good Luck,
Ron

pd1
06-16-2007, 09:08 PM
No suggestions, out of my league.
I sure would like to see a build thread.
Paul

CHELLIE
06-17-2007, 12:49 AM
Wow thats a big plane :) here is what I would use if I was going to convert to electric on that plane, use 1- 120 amp esc to run 2 motors,

4- 3520-6 towerpro outrunners 700kv-700watts $25.00 each at UH
https://www.unitedhobbies.com/UNITEDHOBBIES/store/uh_viewItem.asp?idProduct=4948
2- Hextronic 120 amp ESC, and disable bec with 4 cell being used, $49.95 ea. at UH
https://www.unitedhobbies.com/UNITEDHOBBIES/store/uh_viewItem.asp?idProduct=4316
2-Thunder Power 4500mah 4s 22c 99amp lipo $209.00 ea from Cheap battery Packs
http://www.cheapbatterypacks.com/main.asp?sid=762865&pgid=showlipos&man=TP&cat=EXT
1- Pro BEC 3 AMP $39.95 ea
http://www.horizonhobby.com/Products/Default.aspx?ProdID=SQBDBEC005V

approx cost $657.85 this motor combination will fly a 28lb plane as you have 2800watts with 4 motors, you can use all of your accesories :) take care, Chellie

Ps using 1 esc and 2 motors will work, but it might be better to use 4- 60 amp esc, incase 1 of the esc fails you wont loose 2 motors on one side of the wing
http://www.wattflyer.com/forums/showthread.php?t=18905

Boomerang
06-17-2007, 01:59 AM
You don't have to know how to set up models like this, you just have to know someone who does! See link below:

http://www.geocities.com/ivansplans/

He has lots of experience with models just like the one you want to build. For a big lumbering 4 engine bomber the simpler, cheaper brushed motor option may be more suitable. I have used this system with great success.

A kit designed for glow engines may be built far too strongly & too heavy for electric conversion. Sure, a model will fly at almost any weight if you provide enough power to drive it through the air fast enough. It tends to lose a little of that 'full scale effect' if it's flying like a missile!

I noticed Ron posted the specs of the Stafford B-24. The weight, 10 1/2 lbs, made me laugh! I have a similar size scratch built B-29 (glow powered) and before I built it I weighed the servos, battery, reciever, retracts, tanks, engines, wheels, all I could think of to go in the model.

The total weight without a single stick of wood? 9 1/2 pounds.

Good luck! - John.

skiman762
06-17-2007, 02:28 AM
Wow thats a big plane :) here is what I would use if I was going to convert to electric on that plane, use 1- 120 amp esc to run 2 motors,

4- 3520-6 towerpro outrunners 700kv-700watts $25.00 each at UH
https://www.unitedhobbies.com/UNITEDHOBBIES/store/uh_viewItem.asp?idProduct=4948
2- Hextronic 120 amp ESC, and disable bec with 4 cell being used, $49.95 ea. at UH
https://www.unitedhobbies.com/UNITEDHOBBIES/store/uh_viewItem.asp?idProduct=4316
2-Thunder Power 4500mah 4s 22c 99amp lipo $209.00 ea from Cheap battery Packs
http://www.cheapbatterypacks.com/main.asp?sid=762865&pgid=showlipos&man=TP&cat=EXT
1- Pro BEC 3 AMP $39.95 ea
http://www.horizonhobby.com/Products/Default.aspx?ProdID=SQBDBEC005V

approx cost $657.85 this motor combination will fly a 28lb plane as you have 2800watts with 4 motors, you can use all of your accesories :) take care, Chellie

Chellie
I thought with brushless motors each had to have it's own ESC
I've never had a plane with twins so I'm just going by what I've read here on WF

CHELLIE
06-17-2007, 02:33 AM
Hi Skiman :) I inquired with Kosh on using 2 motors with 1 esc, and he said it can be done, as long as the motors are the same, I asked that question because I will be building a 310 skymaster soon, using 2 brushless motors, and wanted to use 1 esc for 2 motors, as long as the rated amps on the esc will handle the 2 motors, take care, Chellie

Dupe Winger
06-19-2007, 12:28 PM
Thank you all for the responses you have given. I feel building this model with electrics is a better way to go than the original fuel set up. Electric power is going to be more expensive than fuel but I think will be worth it later on for convienence. If there are any manufacturers out there that would like to contribute electric power for this model I would like to do the build on line and use their equipment. I think this could be a fun project to follow and am excited about building it. My Dad was a top turret gunner on a B24 and I think he would have been pleased to see this plane built in his squadron colors.

watt_the?!
06-19-2007, 09:01 PM
if you want to keep the costs down, go for brushed geared setups...very cheap. this will allow the use of scale props or a selection of larger than scale diameter props which will give you the thrust such a plane craves.

Be careful on speccing the electrics based on the glow recommendation- glow being what it is, most cant use scale props and end up overcompensating in terms of speed and skimping on thrust.

another reason why electric would be best. In fact, for such a large plane you could very well use nimh packs to power it as well as the brushed motors.

another significant cost savings..and easier on the upkeep.

i think from memory an olympus gbox and 600 class brushed motor is only $25 or so...and youll need no more than a 20A ESC which these days are $20 or even less.

edit: oh and you can power multiple brushed motors with 1 ESC too!

Bomberguy
06-21-2007, 03:03 PM
Dupe Winger
I've converted one. Check out this thread, it has pictures of it.
http://www.wattflyer.com/forums/showthread.php?t=17789

Grasshopper
06-21-2007, 03:10 PM
Dupe Winger
I've converted one. Check out this thread, it has pictures of it.
http://www.wattflyer.com/forums/showthread.php?t=17789

Hey Bomber Guy, Have you maidened it yet? Sure would like to see photos or video of it.

Dupe Winger
06-21-2007, 03:38 PM
What is the total cost for the electric conversion? I started looking up these components and the cost is rising pretty high. Your model is a real beauty. Are you going to enter it in any competitions? Thank you for all your support..

Bomberguy
06-21-2007, 06:01 PM
Grasshopper
Haven't done the maiden yet. We where out doing taxi testing and hit a rut in the runway and broke a part off the landing gear fork. A fellow club member is going the weld it back together for me then its off to the maiden flight.
Dupe Winger
Yes, it does add up fast. Maybe check out United Hobbies for the power system. I may have gone over board on the battery packs seeing that at WOT I'm inputting 406 watts and pulling 32+ amps at 10400 RPM.
Yes, the plan is to enter it in competitions. I hope to have it at the NATS in August.