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Old Feb 03, 2012, 03:49 AM
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Originally Posted by Jurgen Heilig View Post
How can you get "more bang for the buck" than with a prop, which is already included in the kit?

Whatever alternative prop you'll buy, it will cost you additional money.

Jürgen
£1 for an added 10min 'mixed' flying? Worth every penny

And even if I can find a folding version @ ~ £6, still better value.
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Old Feb 03, 2012, 03:52 AM
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53859 Niederkassel, Germany
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Originally Posted by AshtonFlyer View Post
It's not the folding aspect that I was thinking of, in fact I think it's great. It's the prop pitch.

MotoCalc:

"The diameter (7.0in) to pitch (6.0in) ratio is less than 1.5:1, which will result in reduced propeller efficiency at low speeds (the propeller is stalled). Although this is not likely to affect flying characteristics, it may make take-off or hand launching difficult."
...
You are not "prop-hanging" your EasyStar II, so nothing to worry about a stalled prop. You also need to take into consideration the relatively low rpm of the prop.

Jürgen
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Old Feb 03, 2012, 03:55 AM
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Originally Posted by AshtonFlyer View Post
£1 for an added 10min 'mixed' flying? Worth every penny
...
If you can get that much more, then you probably have a severe mismatch between your drive system and the supplied stock prop.

Jürgen
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Old Feb 03, 2012, 06:30 AM
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Quote:
Originally Posted by Jurgen Heilig View Post
If you can get that much more, then you probably have a severe mismatch between your drive system and the supplied stock prop.

Jürgen
Conversely, MPX might have deliberately underpowered the stock system by adding an unsuitable prop?


Difference between using stock folding and 7x4 prop: 4.5mins on a 20C 1200mAh 3s lipo (~14.5 vs ~18.5 mins)

I based this on "stock motor" 2830-1100 using eCalc (1100kv/0.05res/1A no-load/max 18A/20A ESC) - some of these settings were taken from 'equivalent' motors that had matching kv, size and wattage, because the stock has no full specs available yet.

But the same improvement occurs with any 'similar' motor (kv & W) when changing the prop from 7x6 to 7x5 or lower.

And another constant is that a 7x6 causes launch issues (prop stall thrust) regardless of the calculator used. WeboCalc refuses to even consider a 7x6.

If there's an error in the calcs, I'd be grateful if someone can show me where it is.
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Old Feb 03, 2012, 07:08 AM
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Originally Posted by AshtonFlyer View Post
...
And another constant is that a 7x6 causes launch issues (prop stall thrust) regardless of the calculator used. WeboCalc refuses to even consider a 7x6.

If there's an error in the calcs, I'd be grateful if someone can show me where it is.
Please, don't get me started on WeboCalc.

Most calculators have problems with dynamic conditions, i.e. a flying model. In theory, a prop with a diameter/pitch ratio of 1:1 is about ideal, but only in cruise mode. Running more pitch allows you to run your prop/motor at lower rpm, thus being more efficient due to lower prop tip speeds and being a lot less noisy.

Jürgen
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Old Feb 03, 2012, 07:10 AM
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Originally Posted by AshtonFlyer View Post
Conversely, MPX might have deliberately underpowered the stock system by adding an unsuitable prop?
...
For less power, it is much simpler using 2S instead of 3S or moving your throttle stick.

Jürgen
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Old Feb 03, 2012, 07:36 AM
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Thanks for replying Jurgen - I suspected 'real life' would alter the final results of the calculators, which I why I bought 3 alternate props to try with my new 1130kv motor, even though the calcs specified one (7x4) as the optimum.

My son is currently using the 7x6 folding on his HS, with a 1750kv motor, and considers it a good improvement on his stock motor/prop combo.

I will hopefully get some time this weekend to look at all prop variations with the 1130kv Keda on a wattmeter.
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Old Feb 03, 2012, 08:58 AM
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I've finished! My first fixed wing/foamie/Easy Star 2 build is done, it's balanced and ready to fly.

I've learnt quite a bit and I'm looking forward to getting out with some other pilots to show me the ropes. It's a basic set up right now with power gear close to spec (I couldn't find an RR, shame) but with a UBEC running the servos and a few extra plugs in the wiring loom ready for FPV gear at a later date. I've set up the fuselage side of the aileron wiring but not in the wing yet. I've been advised to start with just Rudder/Elevator so that's what I'll do but I do want to step up and fly with Ailerons too.

I was gonna post a picture but it's just all white right now and I'm sure you know what a white ES2 looks like. I'm undecided on colours but I know I don't want to use those supplied graphics, they make it look like a kids toy! I'm thinking black under the wings, horizontal stabiliser and fuselage wrapping up over the nose. White on top and maybe a bright colour on the wing tips and vertical stabiliser. 'Dynorod orange' maybe (that's day glow ish orange if you don't like in the UK). I've seen one similar on the forums somewhere and really liked it.

I dare say I'll be back with a crash story soon...

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Old Feb 03, 2012, 09:01 AM
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There was a veryyy sleek black n' orange AXN Clouds Fly recently.

Do you have a watt meter you could run and post output please? Saves me changing 1 prop
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Old Feb 03, 2012, 09:55 AM
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Quote:
Originally Posted by AshtonFlyer View Post
There was a veryyy sleek black n' orange AXN Clouds Fly recently.

Do you have a watt meter you could run and post output please? Saves me changing 1 prop
I do, I can only bench test right now though. What watts do you want? I don't know what cruse throttle will be yet but I can do a % of throttle.
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Old Feb 03, 2012, 10:35 AM
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Stock prop
Keda 20-26 1130kv
Hobby WingFun Fly 18A
Flightmax 2200mAh 20c

50%ish stick= 3.5A/40W
100% stick= 11A/125W

The above is rounded to the nearest .5

Don't know if this is what you need. Is this good or bad?
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Old Feb 03, 2012, 11:05 AM
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That's fine! Much appreciated, thank you.

I'll be doing my wattmeter tests either tonight (if I'm allowed access to the kitchen table) or tomorrow.

It'll be good to compare the pitch changes

Oh, I forgot to ask - what's your AUW? I can't remember if you posted it or not.
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Old Feb 04, 2012, 02:43 AM
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Quote:
Originally Posted by AshtonFlyer View Post
Conversely, MPX might have deliberately underpowered the stock system by adding an unsuitable prop?
Unsuitable for what? It seems to me the the stock power train is entirely suitable for the intended purpose.

Like I've said before, if you want ballistic performance you might consider replacing the fuse with something more suitable, like an F-16 for example.

My advice to you, for what it's worth, is to just go flying.
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Old Feb 04, 2012, 03:35 AM
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Originally Posted by Gerry__ View Post
Unsuitable for what? It seems to me the the stock power train is entirely suitable for the intended purpose.

Like I've said before, if you want ballistic performance you might consider replacing the fuse with something more suitable, like an F-16 for example.

My advice to you, for what it's worth, is to just go flying.
I don't think the wings would fit on an F-16 fuselage.
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Old Feb 04, 2012, 03:53 AM
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Originally Posted by Flypoppa View Post
I don't think the wings would fit on an F-16 fuselage.
Good point. Best change the wings as well. Also put an EDF in it.
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