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Old Sep 17, 2011, 09:14 AM
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Alberta,Canada
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Originally Posted by AL1EN View Post
My stock habu with HK 4s 4000mah 40c lipo I have to add 3oz on the tail to balance it on the recommended 4" from the leading edge of the wing. Is that right? I need help.!
Have you cut any foam out of the back of the cabin to slide the lipo back??I try to avoid adding weight like the plague...
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Old Sep 17, 2011, 09:34 AM
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United States, MI, Lambertville
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I can't really move the battery back any more. What are you guys doing when u use your hk 4000mah 4s?
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Old Sep 17, 2011, 09:43 AM
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Canton, Michigan USA
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Originally Posted by AL1EN View Post
I can't really move the battery back any more. What are you guys doing when u use your hk 4000mah 4s?
I don't use a 4S 4000, I use a 5S 3000 but the battery is moved back as much as possible and the receiver is moved back as well to help with that goal of positioning the big heavy battery aft. Foam was trimmed to help with positioning and cooling.
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Old Sep 17, 2011, 09:53 AM
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United States, MI, Lambertville
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I trimed the sides of the tray to fit the 4000mah but not sure how much further back I could go there big batteries. Also by placin a 1 1/2oz in the thrust cone I can get my CG 1/4 off on the nose heavy side from the recommended 4". Bad I dea? What will 1 1/2oz due to performance?
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Old Sep 17, 2011, 10:04 AM
I fly em', there for I am.
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United States, CA, Tehachapi
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Originally Posted by rimripper View Post
Well I run a seperate cc bec with a 3s 460,I had to charge it once this year,it was running a AR7600 and hs 82mg's,and yes you must disable the internal bec of the esc,to use a seperate one.

I like to run the seperate lipo for the sake of knowing that if I have a esc failure in flight,I can still bring my money back down to me,I have a friend who was running his bec of the flight pack,he hit lvc on the lipo,and for whatever reason,he could not gain control of his plane....he was lucky as he was low enough,it only came out with battle scares.
This is the exact reason I have chosen to install External BECs in all my bigger electric planes! It goes back to when I ran nitro---Way back--- Anyway, I remember getting deadsticks all the time and for various reasons. I was still able to bring them in because I still had power going to the rcvr and servos!

I've also had the same situation with electrics. Where the esc died because I was still learning electrics and I pulled to many amps through it. Anyway, I would have been able to save the plane if I still had power to the rcvr.. But because the BEC was through the ESC, I lost the plane.

So why run an external BEC??? Because it very little weight and it's added security of you have to dead stick it in because something went bad with the ESC or the ESCs BEC. Hell, I have an ESC on my bench right now with a dead BEC built in and that worries me about intigrated BECs. Yeah, a BEC could go bad as well but, so can many other things. The external BEC is designed to only do that, be a BEC. So I trust it a lot more than something that's added to an ESC.

I hope that explains why I personally will run External BECs. Just added security to help bring the plane down in one piece or atleast be able to try rather than just putting down the transmitter and watching the show...
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Old Sep 17, 2011, 10:11 AM
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Canton, Michigan USA
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Quote:
Originally Posted by AL1EN View Post
I trimed the sides of the tray to fit the 4000mah but not sure how much further back I could go there big batteries. Also by placin a 1 1/2oz in the thrust cone I can get my CG 1/4 off on the nose heavy side from the recommended 4". Bad I dea? What will 1 1/2oz due to performance?
You do all you can to move things around to eliminate adding extra ballast since extra weight increases wing loading and landing speeds. You are already going to have higher landing speeds because your 4000 mah pack is probably 20% heavier. Just take a look under the canopy and see if you can move it back more. If not, simply fly it as is with the tail ballast and make adjustments when landing.
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Last edited by Prof100; Sep 17, 2011 at 10:25 AM.
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Old Sep 17, 2011, 10:12 AM
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United States, CA, Tehachapi
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Originally Posted by AL1EN View Post
I trimed the sides of the tray to fit the 4000mah but not sure how much further back I could go there big batteries. Also by placin a 1 1/2oz in the thrust cone I can get my CG 1/4 off on the nose heavy side from the recommended 4". Bad I dea? What will 1 1/2oz due to performance?
For my first few flights on my Habu, I only had 4000mah 4S1Ps to use. They were from HK. I had no problem fitting them on there in the stock location. No mods at all... It was a little nose heavy but still very flyable.. So, adding a 1 1/2oz to the plane won't add that much weight and I really don't think it will effect enough to be noticeable. Couple of questions for you,

Where exactly are you adding the weight?

Are you running landing gear or not?

The reason I'm asking about where you're adding the weight is because I think now that I'm finishing my install of a 80A ESC and 5S pack, I'm pretty sure I'll have to add some weight. I was thinking of where to put it and initially I was thinking inside the tail cone. But I think that will effect the thrust...

As for asking about landing gear, I'm not sure how much it all weighs but, I'm sure it's more than 1 1/2oz....
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Old Sep 17, 2011, 10:23 AM
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United States, MI, Lambertville
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My photo bucket wont let me upload right now so I could show u the room I'm working with in the battery compartment/cockpit.
I have the gear on.
And I just got some stick weights and place them in side the exhaust cone for now so there flush with the out side edge. It does creat a little obstruction so idk if I can use it.
My hk 4000 must be big then I had to rim the 1/4" of foam on each side of the tray to fit them
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Old Sep 17, 2011, 01:07 PM
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Alberta,Canada
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Originally Posted by AL1EN View Post
My photo bucket wont let me upload right now so I could show u the room I'm working with in the battery compartment/cockpit.
I have the gear on.
And I just got some stick weights and place them in side the exhaust cone for now so there flush with the out side edge. It does creat a little obstruction so idk if I can use it.
My hk 4000 must be big then I had to rim the 1/4" of foam on each side of the tray to fit them
If you can,pick up a 5s 3000 40c or in that amp range,the Habu will really shine then.
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Old Sep 17, 2011, 01:35 PM
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What I did was moved the esc behind the reciver into that hole the Ali y harness goes thru. that seemed to fix my CG without weight needing to be added to the tail. Only issue I can see is not enough ventilation to cool the esc
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Old Sep 17, 2011, 02:05 PM
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Alberta,Canada
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Originally Posted by AL1EN View Post
What I did was moved the esc behind the reciver into that hole the Ali y harness goes thru. that seemed to fix my CG without weight needing to be added to the tail. Only issue I can see is not enough ventilation to cool the esc
Which will end the flight if it burns,try to make sure it can breathe good,on 4s it shouldn't be to hot,unless you wot the whole time and there is absolutely now air flow.
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Old Sep 17, 2011, 06:11 PM
Will fly for food
Maryland
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One issue with built in BECs is that many of them are linear regulators. The reduce the voltage by converting the excess power into heat.

So for higher cell count packs, they cannot safely drop the voltage. Also, the higher the cell count, the less amps they can deliver safely.

Some higher end ESCs have switching BEC which do not have these problems.

But for higher amp draws (large number or large high speed or high torque servos) a separate BEC is a good idea.
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Old Sep 17, 2011, 06:34 PM
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Canada, ON, Hamilton
Joined May 2011
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Originally Posted by Pinecone View Post
One issue with built in BECs is that many of them are linear regulators. The reduce the voltage by converting the excess power into heat.

So for higher cell count packs, they cannot safely drop the voltage. Also, the higher the cell count, the less amps they can deliver safely.

Some higher end ESCs have switching BEC which do not have these problems.

But for higher amp draws (large number or large high speed or high torque servos) a separate BEC is a good idea.
Seperate External BEC or Life Pack..External BEC for the Habu for sure!! Weight is factor.. the cc 10Amp BEC is fine.
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Old Sep 17, 2011, 06:42 PM
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Canada, ON, Hamilton
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Hey Rim Ripper

http://www.rcgroups.com/forums/showt...t=1503738Check out my new Toy...Think the Habu can handle this one??? Its pushing it a little too far!! Tell me what you think??
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Old Sep 17, 2011, 06:42 PM
Mike Mc
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South Carolina
Joined Dec 2010
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Originally Posted by ZACATTACK View Post
A BEC is a voltage regulator....Dont understand?? So is a voltage regultor heavier then a voltage regulator and a 2S liPo!!??? NO!! If your voltage regulator is providing 4.8V-6V as you stated..your voltage regulator is defintely not regulating!! Your question makes no sense...Sorry..wish I could help..If you wanted 4.8v-6.0v to your battery RX,you dont need a regulator to do that,a Nimh or Nicad battery will do that.
My ESC does not have a BEC. My voltage regulator reduces the voltage from roughly 16 volts down to voltage useable by my receiver. It is wired into the ESC's input leads. I don't need a second battery with my voltage regulator.
Can't you wire your BEC to the input lead of your ESC and not install the two cell lipo?

I run my Habu as it comes out of the box. As hot as the ESC gets I thought the idea of a separate BEC might be worth considering. The talk of adding a second battery confused me. My reaction was to think "why not just install a flight pack?". Not trying to stir anything up. Just trying to understand.
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Last edited by rmmc; Sep 17, 2011 at 06:48 PM. Reason: clarify
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