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Old May 30, 2009, 02:55 PM
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Ok, here is what I am considering

11s 5000mah 1524gr
12s 5000mah 1718gr
11s 5500mah 1636gr
11s 4200mah 1259gr
12s 4200mah 1346gr

So, if you guys are getting decent flight times on 3700/3850mah, then I think I would be good going with the 4200 12s. Only 2500mah used in a 5 min flight? Thats very acceptable for what I am looking for.

I am just about to the point of my build where the gear is done and I can start checking the cog.

Plus, the 4200's are the new Hyperions that can charge at 5c and are supposed to put out some serious power. On top of that I use 6s in my other jet so I can uses them in multiple planes. I think that is what I will go with.
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Old May 30, 2009, 03:04 PM
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Surrey England
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N
Thats such an excellent photo it really captures the moment what it doesnt tell the world is the 20 mph cross wind which gusted lifting the wing 5 ft from touch down

Good flying
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Old May 30, 2009, 03:47 PM
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Techspy, 4200 seems like a good choice to me, and if the new Hyperions are as advertised you might find 11s is plenty of power with the Stumax (though if you have other uses for 6s packs then maybe two of those makes sense as you say).

If you're able to post power measurements please do -- I'm looking to buy a second set myself.
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Old May 30, 2009, 03:52 PM
Neil Jarvis
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From memory mines at 2700W 70A (approx)
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Old May 31, 2009, 01:21 AM
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Hillsboro, Oregon
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I just tried cooling the CC HV110 with these 17x17x8mm fans attached and blowing directly into the cooling fins on each side. There didn't seem to be much benefit: after a 3+ minute bench run with typical full / partial throttle mix, the fins were still too hot to touch (for more than a split second). Admittedly it was a bench run with no airflow through the fuselage, but still the result doesn't seem promising with these tiny fans.
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Old May 31, 2009, 10:09 AM
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From the reading I have done on controllers and the heat problem I have gleaned this.
The controllers run hot on the low to medium power and when you are "blipping" the motor. At high speed the controllers run less hot. In the air you are flying most times at higher speeds and you should have an air supply blowing over your controller(using an air scoop for example)so the controller should be o.k. I was told not to run the motor up and down on the throttle when on the gound as this causes heat build up no matter if you have fans and heatsinks on the controller.

SO ...I say why install all these extra batteries and fans for cooling when (if true)you only need to not run the motor up and down when on the ground or in your workshop. All you would need is a good air stream blowing over your controller when the plane is in the air.
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Old May 31, 2009, 11:12 AM
GRX
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Why not just drop $100.00 and get one of these

100 Amp HV Controller

Mount it like this and be done with it. I've run this setup in the Spark for well over 150 flights without issue. I'm using this unit in several large setup from 2KW to 4.7KW 10 - 12 cells and none of them have given me any trouble.
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Old May 31, 2009, 12:48 PM
Neil Jarvis
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My thoughts as well. I think too much money can be spent on something to only achieve minor top end improvements. I have two mounted this way without any problems, one on 11S 70A) and the other 12S (65A).
If your a connoisseur of air flow then I'm wrong.
Neil
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Old May 31, 2009, 01:06 PM
GRX
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Quote:
Originally Posted by Neil Guildford
My thoughts as well. I think too much money can be spent on something to only achieve minor top end improvements. I have two mounted this way without any problems, one on 11S 70A) and the other 12S (65A).
If your a connoisseur of air flow then I'm wrong.
Neil
I'd have to think that the impact on the airflow is minimal, On mine the hole is maybe 1/3 the size of the heatsink , pulls enough air that it doesnt heat up though. Much funner to fly it with a small inefficiency than to crash it cause my controller melted down on me
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Old May 31, 2009, 01:17 PM
Watt me worry?
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I can't speak for the Spark as I am not flying one yet...however on my Starfire I simply took a clear plastic spoon cut the handle off...sprayed the inside of the spoon the same color as my plane. I then cut a small hole in the fuselage mounted the scoop(spoon)over the hole....then placed the controller over the hole inside the fuselage. Low cost...still looks good and works.
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Old May 31, 2009, 03:37 PM
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Well I am making progress. A couple things of note. I mounted the air tank behind the fan bulkhead and it fit perfectly. This way I used space that was otherwise unused and every little bit of stuff I can move back should help with the cog.

I got the gear mounted and was able to use the front strut at full length. I had to trim the opening a bit and the wheel actually goes approx 1/4 inch past the bulkhead when it is retracted. Next I have to open up the gear holes in the wing for the 2.5" wheels I just got in.

Hey, how many channel rx' are you guys using? I have a 12 channel radio but am using a 7 channel in the spark but am running out of channels. Here is how I have it setup.

Ch1 elevators via a y adapter
Ch2 rudder and front gear via a y adapter
Ch3 throttle
Ch4 Aileron 1
Ch5 Aileron 2
Ch6 Gear
Ch7 Airbrake

Now I don't have a channel for the wheel brakes. I was thinking of putting it on the airbrake channel so they come on only when the airbrake is at maximum. Or make the wheel brakes come on only with the airbrake completely off. So when deploying the airbrake to slow for landing, the brakes are off. After touchdown and needed to apply wheel brakes, the airbrake would retract. With this setting the brakes would be on during the whole flight but unless there is a leak somewhere, this wouldn't be an issue.

I am using digital programmable servos so I can reverse them, change the throw, speed etc.

Any suggestions?

Ron, where did you order the NACA ducts?
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Old May 31, 2009, 06:03 PM
GRX
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I put the wheel brakes on a "Y" with the elevator, when you give it full down then it activates. no extra channel needed

NACA inlets available from BVM
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Old May 31, 2009, 07:00 PM
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Quote:
Originally Posted by GRX
I put the wheel brakes on a "Y" with the elevator, when you give it full down then it activates. no extra channel needed

NACA inlets available from BVM
I agree with GRX, that's where a great many guys put their wheel brakes including me. It makes it easy to apply brakes without taking your hands off the sticks and fumbling for a switch or lever. I have my speed brake setup on a 3-way flap switch. Up is normal flight, mid is take-off - 20% speed brake, slight doop on the ailerons and landing is full down on the switch - full down on the speed brake.

Harry
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Old May 31, 2009, 07:07 PM
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Good idea, I think I will do the same and put the brakes on full down elevator. Question about your "flaperon" setup. When you have the switch for 20% air brake and aileron droop, do you mix any elevator in? From my experience when you use flaperon, it tends to make the nose go up and induce a stall without elevator input.
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Old May 31, 2009, 07:24 PM
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Yes, I do, but I haven't maidened my Spark yet so I can't tell you yet the best setting yet. I've started with 10% and I'll work from there.

Harry
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