hey im just getting in the game of electrics. I just put togetter a ikarus Yak shock flyer and can't decide whether or not to go with 2 or 3 cell lipo. I want to get at least 10 min out of the batteries but I want to keep weight down. I'm not to sure what i should do i here. Thank you for the help

oh by the way i will be running a balsa products 21 motor and 10 anp speed controler


Corey

I don`t know your motor, but I would sugges to go for 3S LiPo. Then you can increase/reduse the power and consumption over a wider range by changing props. Look at some 3S-packs at about 450mAh.

First off you have to look at what you intend to be doing with the plane.

If your flying it outdoors, definatly go for the 3 cell. Your gonna need the extra power.


If your flying it indoors, go for a 2 cell. Its much lighter, and lighter planes fly MUCH better indoors. Id recommend a Thunderpower 7.4V 730mah. Weve been using them here for a while now, and they are SUPER light, and perform great. Combined with a AXI 2204 it makes for a perfect plane. Flight times are around 7-10 min. You just dont really need a 3cell indoor. If you do want a 3cell, Thunderpower also makes a 3cell that is about the same dimensions and just a touch heavier than the 2 cell listed above.

OH yeah, I also am running the BP21 motor from balsapr.com
Ive been running it on the battery listed above, and it works flawlessly. Easily hovers and has power to pull out. You may want a larger ESC though. 10 amps is on the tad on the low side for that set-up. Ive been using the e-flite 20amp ESC with NO problems.

Ive also flown it outdoors with that set-up. It flys great. A 3cell would be better for outdoors, but the little 2cell will pull it just fine. It will still go vertical with the 2cell.

Here is the set-up Im running

BP21 brushless outrunner from balsapr.com
E-flite 20amp brushless ESC
Bluebird 4ch reciever
Bluebird BMS-306 on ailerons
Bluebird BMS-303's on elevator and rudder.
Thunderpower 2cell 7.4V 730mah LiPo

All on a F3A shockflyer. Hovers no problem, has plenty of power to spare.

@bdavison what prop are you useing on that set up, or what would you suggest

I went through ALOT of props before I found the one I really liked.

Here's the props I tried and what I thought of them


GWS 8.4 - Not enough prop. It flew slow and smooth, but lacked the punch I needed for 3D maneuvers.
APC 8.6 - Nice prop, but WAY too punchy. Couldnt get a smooth throttle response from it. I kept having to jockey the throttle around to maintain the correct thrust. It seemed like it wanted to jerk the plane around instead of flying it smoothly.

GWS 9.4 - Much better, but seemed to cavitate a little due to the flexabilty of the blades when I really popped the throttle to it which gave this aweful fluttering buzz noise.

APC 9.4 - PERFECTION AT LAST. Smooth throttle response, hovers just a tad below 1/2 throttle, and has instant punch-out when I hit the throttle. The stiffness of the prop means no cavitation when you punch it. Im sticking with this one on the F3A, as its the best one Ive found. It seems to pull the plane much easier and more smoothly.

They say max prop for the BP21 should be a 8.4 but I honestly think that's really conservative. It flys much better on a 9.4
Ive been using the 9.4 for a while now with no adverse affects. I havent checked to see how many amps its drawing, but the current equipment Im using is handling it fine. No overheating or anything. Im using the E-flite 20amp ESC and of course the Thunderpower lipo above.

Oh and just so you know.

The BP21 is supposed to put out about 11.3oz of thrust on the 2cell lipo...with a 3 cell lipo it puts out a WHOPPING 21oz of thrust. Imagine what 21oz of thrust will do on a 7oz airplane.

hey thanks alot for the info

No problem....
Enjoy, and let me know how your plane works out.

Thanks for the info bdavison on the props i am still awaiting all my electrics to be delivered i order about a week ago still not arrived think i will be making a few phone calls later today i will definetly have to give the APC 9.4 ago i'll catch up with you when i get sorted

hey i'll try to post my yak and see what you think


Corey