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Old Jul 16, 2012, 10:51 AM
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Joined Jul 2012
7 Posts
Question
Easystar 2 setup with stock propeller?

Hello,

This is my first thread on this forum and I am building my first plane. In other words I am completely new in this hobby so please have patience with me.

I have bought an Easystar 2 from the Swedish webside RC Flight (http://www.rcflight.se/visaprodukt.aspx?id=1934). Since I did not know much I asked the site manager what setup I should use. I bought the equipment he recommended:

ESC: HobbyWing Flyfun 18A
4 servos: EMax ES08A 8.5 g 1.5 Kg
Battery: Gravity 2200 mAh 3S 30-40 C LiPo
Turnigy SK 2826 1240kv

I also asked if I could use the stock propeller that comes with the Easystar 2 - a 7"x6" folding propeller (18cm x 15cm) - and he said yes.

Now to my question:
Can I really use this propeller?
If the answer is no, which propeller should I get?

I plan to try FPV with this plane in the future if all works out, so it would be great if the propeller could work even with some extra weight.

Kind regards,
Marcus
---------------------------------------
Specs of engine:

Brand: Turnigy SK
Kv: 1240
Max Volt: 11.1 V.
Max Amp: 16 A.
Watt: about 150 W.
Length: 28 mm
Weight: 45 g
Shaft: 3 mm

Specs of ESC:
Brand: HobbyWing
Series: Flyfun (Pentium).
Max Amp: 18 A (Burst 22 A).
Weight: 19 g
Size: 24 x 45 x 11 mm
Capacity (celler): 2-4
Max A BEC: 2 A (5V)

Specs of plane:
Wing span: 1366 mm.
Body length: 977 mm
Flight weight: 700 g.
Wing Area: 28 dm2
Load per wing area: 25 g/dm2
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Old Jul 16, 2012, 12:23 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
20,728 Posts
The 7x6 is on the high side but may be OK.
The stock motor is an 1100 kv and your motor is a 1240kv so you are trying to spin the prop faster which draws more current.
It's always best to check the amp draw when a new prop size is used. One of these would do the trick. http://www.headsuprc.com/servlet/the...TER/Categories If you don't want to invest in one at this time, ask another RC'er to make the measurement for you. Too few amps and you are not getting the power you need, too many amps and you'll fry the motor and/or ESC and/or battery. The prop size determines the amp draw by the motor.
Based on the original motor and your new motor's specs, I'd go with a 7x4 to start with.

Of course you can always use the finger test. Fly for a couple on minutes and land. Can you hold the motor in your fingers for 10 sec? If not, drop down the prop size. If it's cool, increase the prop size. Warm to very warm is OK as long as you can hold it in your fingers for 10sec or more.
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Last edited by hoppy; Jul 16, 2012 at 12:43 PM.
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Old Jul 16, 2012, 02:35 PM
Wake up, feel pulse, be happy!
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United States, AK, Fairbanks
Joined Aug 2009
12,382 Posts
Checking the current draw is always a good idea, but that prop and motor combo sounds perfectly fine to me. I would be very surprised if it drew more than the motor is rated for.

The setup sounds somewhat anemic for an EasyStar, though.
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Old Jul 17, 2012, 04:59 AM
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Joined Jul 2012
7 Posts
Thank you both so much for replying so fast! I think I will try to be on the safe side for my first couple of flights and get me one of those 7x4 propellers to start with. Then I can try the one I already have later.

I have not heard of the finger test before but I will try it! I will report back when I have had my maiden flight.

Since the motor I got does not fit in the original motor mount I will also have to try to build a new motor mount. So I might not be in the air for another week or so.

Thanks again and wish me luck!
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Old Jul 17, 2012, 07:10 AM
Space Coast USA
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Space Coast
Joined Oct 2000
20,728 Posts
Finger test is good for all components - A Wattmeter is much better,
After landing the first couple of flights, feel the motor - ESC - and battery. If you can hold on to them with your fingers for at least 10 sec you are OK. If anyone of them is hot, the prop size needs to be reduced.
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Old Jul 18, 2012, 08:07 AM
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Beaumont, TX
Joined Feb 2007
1,332 Posts
And you could also do some reading and ask here:

http://www.rcgroups.com/forums/showthread.php?t=1525403
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