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Old Oct 22, 2012, 05:11 PM
Electric
Joined Oct 2009
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fan

The local hobby shop should carry these 5v fans in the car section. Runs fine on 6v rx power.
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Old Oct 22, 2012, 05:54 PM
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Quote:
Originally Posted by RTaylor View Post
Wait doesn't it call for 3s lipo what am I missing. Is it you guys just wanted more? I will start tonight with building thank you for sharing build challenges and work arounds.
Randy
Yes, 3S is recommended.

For electric sailplane setup:
- 6+ channel Transmitter and Receiver radio system
- 25-size brushless outrunner motor
Maximum Burst Current: 44A (15 sec)
http://www.horizonhobby.com/products...70kv-EFLM4025A

- 60-Amp brushless ESC
- 11.1V 3S 3200mAh 30C Li-Po Battery
- Servos - (2) Micro servos and (4) Thin Wing servos
- Folding propeller and spinner
- Charger for flight battery

approximately 500-550 watts with a 14X8 prop

At a target weight of 5 pounds = 80 ounces

110 watts/pound.

If you want to go 4S the recommended prop is smaller.

You might save 2 ounces by going to a smaller, higher C pack. Probably not worth it.
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Last edited by aeajr; Oct 22, 2012 at 05:59 PM.
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Old Oct 22, 2012, 06:00 PM
RCHN #150
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Lawrenceville, GA
Joined Nov 2007
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Quote:
Originally Posted by Craig Greening View Post
The flap to elevator mix lives in the mixing menu, labeled FLP > ELE. It defaults to zero values, so if you started with a blank model it sounds like you have a mix active somewhere else.
Thanks. That was it. I had copied my Radian setup, and forgot about that.

Rick
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Old Oct 22, 2012, 06:03 PM
RCHN #150
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Lawrenceville, GA
Joined Nov 2007
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Quote:
Originally Posted by aeajr View Post
(1) As has been said, down elevator with flaps is almost mandatory.

(2) Your radio is very smart.

(3) I would stay with the recommended spektrum servos.
(1) Yes - the trouble is I had WAY too much elevator, and could not remember what I had done.

(2) Way smarter than me, see (1) above.

(3) Absolutely.

Rick
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Old Oct 22, 2012, 06:07 PM
RCHN #150
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Lawrenceville, GA
Joined Nov 2007
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Quote:
Originally Posted by RTaylor View Post
Wait doesn't it call for 3s lipo what am I missing. Is it you guys just wanted more? I will start tonight with building thank you for sharing build challenges and work arounds.
Randy
Yes. However, knowing that higher voltage is "easier" on our ESC and motor than high amps, I thought with a relatively low kV motor, I would give it a try. And, having a CC ICE Lite 75 lying around, I figured why not try it. The CC ESC will give me power data . . .

I am also using a smaller battery - 2100 mAh.

So, after I get this trimmed and the camber set, I will start some measurements and see what we have.

Rick
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Old Oct 22, 2012, 06:28 PM
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Red Bluff CA
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Did you get your folding prop from esprit then?
Randy
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Old Oct 22, 2012, 06:49 PM
Electric
Joined Oct 2009
422 Posts
Aeronaut CAM Folding Propellers will be the better blades to choose from IMHO, mainly due to the higher rpm handling. Esprit RC has good prices on a full collection.

14" blade will handle up to 11,000rpm.

http://www.aero-naut.de/en/products/...camcarbon.html
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Old Oct 22, 2012, 08:57 PM
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So what do you guys think would be a good starting point on prop size if we wanted to go 4s w/ the power 25 motor?
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Old Oct 22, 2012, 09:17 PM
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I am a big beliver in reading the instructions.

3S–4S Li-Po or 10- to 14-cell Ni-MH/Ni-Cd
11x8 to 14x7 prop

4S prop would get the 11X8, maybe 12X7. Pushing to the limit might be 12X8.
You must use a wattmeter to check if you vary from the recommended 11X8 prop for a 4S pack.
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Old Oct 22, 2012, 11:32 PM
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well, I would agree....but the instructions are giving prop ranges for a sport/3d plane, not a glider that will be on power for 30 seconds at the most.

Quote:
Originally Posted by aeajr View Post
I am a big beliver in reading the instructions.

3S4S Li-Po or 10- to 14-cell Ni-MH/Ni-Cd
11x8 to 14x7 prop

4S prop would get the 11X8, maybe 12X7. Pushing to the limit might be 12X8.
You must use a wattmeter to check if you vary from the recommended 11X8 prop for a 4S pack.
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Old Oct 23, 2012, 06:47 AM
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Originally Posted by txg8gxp View Post
well, I would agree....but the instructions are giving prop ranges for a sport/3d plane, not a glider that will be on power for 30 seconds at the most.
Motors and props don't care what kind of plane you are flying. They care about watts, amps and volts. This motor is good for about 500 watts. So you can prop and pack for higher speeds or for higher thrust. Gliders like thrust more than speed.

The starting point is clearly stated in the instructions. Even the base specs provide the starting point. But you have to know how to read them.

Props are like gears on a car or on a bicycle. A road bike and a mountain/trail bike may both have 10 speeds but the road bike will spend most of its time in higher gears while the mountain bike will spend most of its time in the lower gears. The road biker typically cares more about smooth higher speeds relative to the mountian biker who cares more about low speed torque to handle dirt, rocks and obsticles.

So you can set this motor up for high speed flying, like an F27 striker or you can set it up for high torque acceloration which would be best for a glider.

The small prop goes with the higher voltage battery because the motor will be spinning faster. It will typically produce less thrust but more top end speed. This is like running in high gear. You go faster but your acceloration is slower.

The larger prop goes with the lower voltage battery because the motor will be spinning slower. You will typically get more thrust and less top end speed. Your top speed is less but your low end "pulling away from the light" is much stronger. Great for a 30 second steep climb.

For gliders you typically want to go with the larger diamater slower moving prop as you are more interested in thrust and acceloration for 30 seconds for a solid climb than flat line top speed. A larger slower turning prop is more efficent and is typically better suited to a glider.

So, in this case, for this motor and this glider, I would go with the 3S pack and the 14" prop. And that is the combination that the MFG recommends. This is the reason behind the recommendation.

The specs say 14X7 to run at continous amps max. The recommendation for this glider is a 14X8 which will probably run you close to the burst amps spec for 30 seconds.


That is how you prop a glider. That is why the MFG made their recommendation for 3S/14X8.
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Old Oct 23, 2012, 08:48 AM
Electric
Joined Oct 2009
422 Posts
Hot air

Someone please tell me where the hot air exhaust is

The spinner and two side inlets give lots of cool incoming airflow, but where does the airflow escape?
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Old Oct 23, 2012, 08:52 AM
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Ireland, County Kerry, Kerry
Joined Dec 2005
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Quote:
Originally Posted by DeadstickDuck View Post
Someone please tell me where the hot air exhaust is

The spinner and two side inlets give lots of cool incoming airflow, but where does the airflow escape?
It doesn't escape: it stays on board so as to contribute to lowering the effective wing loading ...

Chris
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Last edited by Woodstock 1; Oct 23, 2012 at 09:10 AM.
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Old Oct 23, 2012, 09:31 AM
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Funny Chris.

There should be a escape location, even if it is a small one. Since this is intended to be a 30 second or less run, a certain amount of heat build up can be tollerated.

If you were to run constantly then you will likely need to open up some heat escapes.

But for the short burst, there is probably enough leakage to let the heat out over the length of time between short motor bursts.
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Old Oct 23, 2012, 09:41 AM
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Joined Dec 2005
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On a serious note, it is a good point though: I've seen a few electric gliders with massive air vents hogged out of the nose, but little by way of a matching exhaust....
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