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Old Jun 19, 2012, 07:31 PM
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Joined Jun 2012
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Help me pick out motor, ESC, battery, and servos for my first scratchbuilt.

Hi all,

I'm nearing completion of my first homemade plane I need help picking out some of the electronics that will work with the plane.

I really don't know how to pick the correct motor based on kv, power output, and thrust ratings. ESC would depend on the motor. For the servos, I decided on a set of HXT900.

2200kv motor.
http://www.hobbyking.com/hobbyking/s...dProduct=12919

2200mAh Battery - too big?
http://www.hobbyking.com/hobbyking/s...Lipo_Pack.html

Here's the plane. I won't be attaching the wings until after I receive the electronics.

Wingspan - 45 inches. Length - 25 inches.
Made from Dollar Tree foamboard, packing tape, and hot glue.

http://imgur.com/XhplS

Thanks!
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Last edited by MightyRed; Jun 19, 2012 at 07:43 PM.
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Old Jun 19, 2012, 08:37 PM
Lost but making good time
Joined Nov 2008
1,345 Posts
Mighty,

Usually one begins by picking a prop size that is around 1/4 the wingspan of the aircraft. The airframe specs...wingspan, wing area, and total weight of the airframe along with how you want to fly the plane will dictate the power setup. Before you get into that...I'll attach a thread to read, you might want to compare your airplanes specs with the specs I'm adding. There is something in the proportions of the wing to the rest of the airframe that seems a little off...or it could just be me.

http://www.rcgroups.com/forums/showt...oflyzon...Read at lease the first 16 entries in this thread. You will have a good method to follow to set up your planes power system.



Regards,

Hankg
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Old Jun 19, 2012, 09:54 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,140 Posts
What Hankg said! Your motor weight is about right (50 grams for 150W or power) but the Kv is way too high.

You want to use about a 10" prop and need a motor with a Kv of 950 to 1100 or so. Motors in the 50-70 gram range will be about right. A high Kv is not going to work with the 10" or so props you need to use.

The HXT900 servos are good, get a spare or two just in case.

The battery is OK too, you'll get decent duration and it won't be too heavy.

Get a bottle of Gorilla Qjuick PU (about $5 at Home Depot) and use that more than the hot glue for the foam to foam joints. Spritz with water so it foams up and geting into the foam and fills some of the voids at the joints.

Is that a square PVC pipe fuselage? That may be a bit too heavy but it might work.

Can you already fly? If not, a low wing plane with a flat wing is going to be a handful to learn to fly with. If you can modify your wing design to be like the one used on this plane it will make that plane much easier to fly and much more crash resistant:

Trainer type plane - http://www.rcgroups.com/forums/showthread.php?t=1281056

That is a polyhedral tip wing and will produce a very stable flying plane. It will also be quite aerobatic as you skill improve so don't look at it as being sort of lame, newbie only, trainer type plane.

You can build with the semi symmetrical foil you have in the photo but the KF airfoil seen in the Trainer Type Plane build details will be a much better wing choice. You can build flat, even in two pieces, and put two spars in it (1/4" dowels, arrow shaft, etc.) and you'll have a nice flying tough wing.

Use the Go Advanced posting method and upload your images to the servers here instead of using then Imgur thing. That get the images stored here and keep them here. Size them down to 800 x 600 or so, scroll down from the Go Advanced posting method, and use the Manage Attachments button to up load them.

Jack

Jack
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Old Jun 19, 2012, 10:22 PM
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Joined Jun 2012
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Thanks guys, I'll check that thread out!

Jack, the fuselage is foamboard. I have a 4CH plane that I recently started flying again, so not a complete flying virgin.
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Old Jun 19, 2012, 10:42 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,140 Posts
Quote:
Originally Posted by MightyRed View Post
Thanks guys, I'll check that thread out!

Jack, the fuselage is foamboard. I have a 4CH plane that I recently started flying again, so not a complete flying virgin.
OK, you may be OK with the low wing flat guy then. Getting a two piece wing low mounted on a fuselage can be challenging, I thought maybe a high wing with a one piece wing would be easier.

You can join the two panels in the center with a wrap of clear duct tape and using the PU glue if you have some spars in the wing. I'm a KF wing guy and really like them don't mess with any thing else any more, that is how well they fly...

You can see the way I joing the polyhedral tips on this wing here to get an ideas as to how I was talking about use the tape and glue for the joint. This wing did not have a center joint but had a joint for the polyhedral tips:

http://www.rcgroups.com/forums/showthread.php?t=1474665

Jack
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