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Old Aug 04, 2012, 11:55 AM
certified crash instructor
Scottsdale Arizona
Joined Dec 2009
2,215 Posts
Quote:
Originally Posted by ufale View Post
I was thinking of going with a 13.4 prop, a 3s 3300 batt., and a 40 amp eflite ESC. I currently have an ICE 75 amp esc in the plane, but it is pretty big and heavy. I will put it on a meter later to see how it performs.
40amp esc might be too small for a 3s application. If you pull around 700 watts on a 3s lipo you're gonna be around 58amps.
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Old Aug 04, 2012, 01:55 PM
Keep Flying
Swedesboro NJ
Joined May 2008
767 Posts
Took the yakker out for a couple quick flights today a bit windy [12mph]but i wanted to do some speed runs,i installed the eagletree speed sensor,first run level flight flying with the wind i got 81mph,2nd flight with the wind with a slight dive from a little above treetop i got 83,motor,esc are stock,using a 12x6apc with turnigy nano 3000 4s 25c.the yakker moves pretty good in its stock configuration

Ron
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Old Aug 04, 2012, 04:14 PM
Keep Flying
Swedesboro NJ
Joined May 2008
767 Posts
Quote:
Originally Posted by alucard0822 View Post
I ran most every prop I had that would fit through my Watt meter and scale for amp/watt/thrust, and then figured relative efflux(theoretic prop wash speed) assuming 15K RPM, don't have a tach, but it should be somewhere in that neighborhood. General rule is larger diameter=better control and more wash over the control surfaces, faster efflux=faster top speed, less "braking" when throttle is reduced, aerodynamics dictate how close to the efflux speed the plane can go, amp draw and watts are self explanatory. Going by Horizons ratings of 60A constant, and 75A for 15 second burst, all of the props I tested fall under that, so at worst, you should limit firewalling the throttle to 15 seconds on the higher draw props.

Thing is that at speed, a prop is drawing fewer amps than static, so even if a prop draws 70 amps when punching out of a hover full throttle, then 15 seconds later with this plane, it is probably going to be doing 60+MPH, and probably drawing less than the 60 amp continuous rating. Battery C rating and capacity also affect amp draw, on a fresh 3Ah 30C, it may draw 10 amps more compared to a fresh 2.65Ah 25C battery, or even the original 3Ah 30C when it is low on charge. Differences in conditions, altitude, and your individual setup including subtle variances in equipment, temp, vibrations, and airflow over the ESC affect it's efficiency, and how much it can take.

Tested on stock battery drained about 25% to 4v per cell.
10.5X9(PKZ Extra300 prop) 70A, 985W, 4#7oz thrust, 127mph

12X5.25(stock prop) 59A 880W, 5#13oz thrust, 74.5mph

12X6APC E-prop 74A, 1025W, 6#1oz thrust, 85mph

13X4APC E-prop 68A, 975W, 7#6oz thrust, 57MPH

The 12X6 and 13X4 APC props are fine, and work great, the 12X6 when you want to go fast, the 13X4 when you want to go slow, or fly 3D. The 10.5X9 loses too much thrust, and while it looks to be the fastest in the air(blistering fast from a dive), it takes forever to build speed. The stock prop would be a happy medium, especially given the lowest draw of the bunch, if 9 out of 10 weren't defective.
I remember back in the thread the calculated speeds being posted somewhere by alucard,i did a search and found the numbers he come up with,he was almost on the bulls eye,now i cant wait to try out a smaller prop,i dont have a 10x6 but i do have a 10x7apc ,should put me in the 100mph club with the yak LOL

Ron
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Old Aug 04, 2012, 04:23 PM
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Puerto Rico, San Juan
Joined May 2008
2,707 Posts
If you want 100mph use the pz extra 300 prop or APC 10x10e
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Old Aug 04, 2012, 04:57 PM
Keep Flying
Swedesboro NJ
Joined May 2008
767 Posts
Quote:
Originally Posted by DaxFX View Post
If you want 100mph use the pz extra 300 prop or APC 10x10e

I dont have the 300 prop lying around ,i was reading alucard post wrong,i thought it said 10x5 [DUH],i looked up the extra now i get it 10.5 x9.LOL,well i dont have one of those but i do have a 10x10,gotta see what the amps look like with that one,i also have a 9x9 and a 10x7 i run the 10x7 on my pulse 25 with a P25 1250 kv and that pulls 62 amps and screams so i gotta see what the amps look like on this,not really into making this a speed demon,just curious about the speed, and since i have the sensor still mounted on there i wanted to see what it can do,after i am done i will go back to my 12x6

Thanks Ron
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Old Aug 04, 2012, 08:38 PM
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ufale's Avatar
Joined Nov 2010
349 Posts
OK...here are my numbers: (stock motor, 75 amp Ice Esc, 2200 3s batter, 13.4 asc prop) 466 watts, and 40 amps. Would I have a problem flying this setup?
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Old Aug 04, 2012, 08:43 PM
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Puerto Rico, San Juan
Joined May 2008
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I dont think with 2200. You will kill the battery unless you have a 50c or higher. Also you will have only like 2 minuts rumtime
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Old Aug 04, 2012, 08:44 PM
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Old Aug 04, 2012, 08:48 PM
certified crash instructor
Scottsdale Arizona
Joined Dec 2009
2,215 Posts
It will probably fly but feel underpowered. You may want to try a 14x7 to bring the watts up. I use the 10 watts to every ounce method, you would be good for a 46 ounce yak. I would shoot for 600 watts, I probably wouldn't attempt flying at 440 watts but it's probably possible. Your lipo is too small, I bought a hyperion 2600mah, 45c, 3s, not sure if that's gonna be big enough.
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Old Aug 04, 2012, 08:50 PM
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Quote:
Originally Posted by slo-fly View Post
It will probably fly but feel underpowered. You may want to try a 14x7 to bring the watts up. I use the 10 watts to every ounce method, you would be good for a 46 ounce yak. I would shoot for 600 watts, I probably wouldn't attempt flying at 440 watts but it's probably possible.
What do you think my run time would be at 14 x 7? With a 2200 3s, or a 3200 3s?
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Old Aug 04, 2012, 09:05 PM
smoke is my wattmeter
Longview, Tx
Joined May 2008
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I had about a 4 minute flight with a 3s 2200 this morning. Haven't measured the watts with this battery but it's probably around 450ish. It wasn't a powerhouse but had enough juice to hover. Runtime is all about how you manage the throttle. I think I'd give the 14x7 a try. Be sure and check your balance.
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Old Aug 04, 2012, 09:18 PM
certified crash instructor
Scottsdale Arizona
Joined Dec 2009
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Quote:
Originally Posted by ufale View Post
What do you think my run time would be at 14 x 7? With a 2200 3s, or a 3200 3s?
I'm going to assume the 14x7 will pull around 50amps, you might see around 3-4 minutes run time on 2200mah, a 2600mah should go 4-5 minutes, 3200mah will be around 5-6 minutes, maybe 7 mins max.
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Old Aug 05, 2012, 03:28 AM
certified crash instructor
Scottsdale Arizona
Joined Dec 2009
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I finally got around to some 3s testing on the hyperion 3025-8 motor and a 12X6 vox prop and the results are in, 576 watts and 48 amps. It will probably fly pretty good just the way it sits. I highly recommend the hyperion 45c lipo for 3s applications, this lipo will take a beating and it throws down some power!
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Old Aug 05, 2012, 03:45 AM
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Is there a particular reason for running a 3s with this plane? Just curious...
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Old Aug 05, 2012, 03:58 AM
certified crash instructor
Scottsdale Arizona
Joined Dec 2009
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It's a weight thing. My hyperion 2950mah 4s weighs 12.5 ounces, the 2600mah 3s weighs 8 ounces. That and 3s lipo are cheaper.
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