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Old Jun 09, 2011, 05:25 PM
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Joined Jun 2011
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Components of an electric RC plane

I would like to build a electric rc plane (Foam) but im not sure about all the components.

Motor- BpHobbies outrunner 2217-6, 25 amp ESC, 11.1v 2200mah lipo, Four Bluebird 371 micro servos, 9" prop, carbon rod for the wing, push rods, horns for tail and ailerons. i also have some styrofoam that i intend to made the fuselage, wing and tail out of.

Is that all i need? if not, what's missing and could you show me a product that will work with the components that I already have?

thank you
James
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Old Jun 10, 2011, 02:50 AM
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Staffs, UK
Joined Nov 2003
10,383 Posts
Well you're going to need a transmitter and a receiver to plug the ESC and servos into (the RC part of "electric RC plane ).

Other than that, with the right design and some glue to stick it all together you're pretty much there. OTOH it does depend on what type of "styrofoam" you have because some works great and some is far too flimsy to be any use.

BTW the Foamies (Scratchbuilt) forum is a good place to look for designs and ideas on putting something like that together - http://www.rcgroups.com/foamies-scratchbuilt-428/

Steve
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Old Jun 10, 2011, 06:19 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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What Steve said!

Go to the Foamies (Scratchbuilt) subforum, pick a design for your first build (or a design that is close you what you want to build), and you can get a lot more help as you build. And the others that have built before you will be there to answer questions and help you.

Looking at the motor you have, 70 grams, about 200 Watts, you want to be looking at planes with about a 40" or so wingspan and that will fly at about 18 to 32 ounces or so. Some that might work for you are the Blu Baby 42, the Oshkosh Special, the OK 40 and some of the other high wing trainers.

I strongly recommend the builds with a KFm wing for their simple and quick building and there gentle stall and wonderful flying ability.

Styrofoam is a little on the brittle side and not a strong as foams like FFF (Dow Protection Board III) or Depron. It is generally used more for hot wire cut foam cored wings and that is not a good choice for getting started with.

If you are in the U.S. and can get FFF from places like Lowes or Home Depot, that is probably the best all around choice for a material.

Jack
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Old Jun 10, 2011, 06:59 PM
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Sammamish, WA, USA
Joined Jan 2010
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What 9" prop. I run that BP 2217-6 motor on a few planes and it is ideal with an 8x6. I would think a 9" will be pushing it a bit far.
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Old Jun 10, 2011, 07:26 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Lardog is right about the 9" prop being a little big for that motor. If you look at the prop testing data at flybrushless.com (the BP 2217-6 is a Suppo - A2217K/6T motor) you can see that:

http://www.bphobbies.com/view.asp?id...7&pid=B3945417

Look at the testing done for 3S voltages, around 10V. Don't let the 7-8V or so 2S testing entice your into thinking that you can use those larger props unless you plan on getting a 2S battery also.

Depending on the plane you build a motor with a little lower Kv would be a little more versatile.

You have a list with a motor and a prop and are looking for a plane, it is more normal to pick the plane you want to build, let that lead you to the prop size, and then pick a motor with a Kv and size that is right for the plane.

But a 1200 Kv or so motor would work with props up to 10" or so and also let you use regular and slow fly props better.

Jack
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Old Jun 11, 2011, 04:35 PM
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Joined Jun 2011
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Thanks for the help lads, I really appreciate it!
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Old Jun 12, 2011, 12:31 AM
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United States, AK, Fairbanks
Joined Aug 2009
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Quote:
What 9" prop. I run that BP 2217-6 motor on a few planes and it is ideal with an 8x6. I would think a 9" will be pushing it a bit far.
Quote:
Lardog is right about the 9" prop being a little big for that motor.
Hold it.... I run that motor on 3S (yep, three-cell lipos) with a GWS-HD 9050 or even the 9075 (that's right, a 9x7.5 prop) and it's just fine with good cooling. Very powerful setup when you feed it off a decent lipo, too.

I just have the motor completely exposed on the nose of the plane and with the 9050 it comes down pleasantly warm, sort of like you've just been holding it in your hand for a few minutes. The 9075 isn't too much worse, but you'd definitely want to run at least a 30A and preferably 35A ESC (I use a 25A Castle and it warms up a bit, but I've dulled the motor's power quite a bit with the ESC's programming).

I'd say just run the 9" prop and check the temperature often; depending on the actual prop you might end up generating a lot more heat than my setups do. If it gets real warm, switch to something in the 8" range.
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Old Jun 12, 2011, 12:42 AM
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Sammamish, WA, USA
Joined Jan 2010
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With an 8x6 on 3s, I use a 40A ESC and it pushes about 42A and 475W at WOT. You are using a 25A with a 9x7.5?!?

I guess you like pushing to the limit and beyond, eh?
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Old Jun 12, 2011, 06:48 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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The prop testing numbers at flybrushless.com are what were found to be safe limits that did not cause over heating in static testing. The results are aimed at newbie type flyers that might not have any depth of knowledge, a watt meter, or interest in doing any testing. They can put it a full throttle and nothing should burn up is the bottom line.

As we all know, if you test props, use a watt meter, moderate the throttle to less the full and to various settings as you fly, things can change a lot. And I think that is what explains the difference between Lardog's and TP16's prop choices and recommendations and the prop testing data at the link I posted.

The bottom line is that if you use a prop size or fly in a manner that causes the motor to overheat something can burn up. If you use your head, prop choice, the throttle, or simple native cunning and do not generate an excess of heat nothing will burn up.

Jack
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