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Old Oct 29, 2012, 09:37 PM
Tim
United States, AR, Fayetteville
Joined Sep 2012
47 Posts
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Scratchbuild is done - need batt/ESC/motor/prop recommendations!

Just finished my first ever plane. I've never flown an RC plane before, and my son and I are really excited to fly it! I've been flying a simulator for a few weeks, and I think I'm getting the hang of it.

I just weighed our plane. It weighs 1.54 lbs (with no motor or battery). I've attached images of the dimensions. Of course I'm looking to do this as cheap as possible, not looking for anything crazy powerful or fast. Just want it to fly!

Oh, and for what it's worth, I already have a small charger (this one), though I understand I might need to get a different one depending on battery recommendations.

Thanks for any suggestions/advice!!
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Last edited by loneboat; Oct 29, 2012 at 09:47 PM.
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Old Oct 29, 2012, 10:09 PM
I think I'm inverted. Maybe.
acetech09's Avatar
United States, CA, Pacifica
Joined Apr 2012
1,505 Posts
Is there a local RC club where somebody could test-fly that plane before you take it up? I've seen people sucessfully transition between simulator to a first scratchbuild before, but having somebody else check the design is a great step.

First thing to check with a scratchbuild is wing cube loading. Your first scratchbuild will always be heavier than it can be. At 435sq. in/1.54lbs dry weight, it's going to be a bit heavy, still flyable no doubt, but not the best for training. If you could lighten it at all, it would help you greatly.

At that point, I just go to eCalc and flyBrushless, plug in your dry flying weight, then start going through motors from my go-to motor supplier, Altitude Hobbies.

After a bit of toying around, it looks like the Suppo 2212/13 on a 3S with a 8x4.7SF prop would be the best bet. Pretty good thrust and battery life.

http://www.altitudehobbies.com/brush...-suppo-2212-13

And since you'll be drawing around 8-10A, a Suppo 18A ESC will be plenty, and give you one less thing to worry about.

http://www.altitudehobbies.com/brush...-brushless-esc

Suppo stuff is dead-simple to setup and use, and you'll get amazingly fast service from Altitude. It's my go-to motor store these days.
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Old Oct 30, 2012, 07:13 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,681 Posts
What the plan for the motor mounting? I see those two CF(?) tubes in front of the wing but you need something more to attach the motor to.

Jack
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Old Oct 30, 2012, 08:08 AM
Tim
United States, AR, Fayetteville
Joined Sep 2012
47 Posts
Quote:
Originally Posted by jackerbes View Post
What the plan for the motor mounting? I see those two CF(?) tubes in front of the wing but you need something more to attach the motor to.

Jack
They are CF arrows, so they have threaded ends. Those two shafts slide, so once I mount the motor on them (via the threads) they'll serve to adjust CG as well.
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Old Oct 30, 2012, 08:09 AM
Tim
United States, AR, Fayetteville
Joined Sep 2012
47 Posts
Quote:
Originally Posted by acetech09 View Post
Is there a local RC club where somebody could test-fly that plane before you take it up? I've seen people sucessfully transition between simulator to a first scratchbuild before, but having somebody else check the design is a great step.

First thing to check with a scratchbuild is wing cube loading. Your first scratchbuild will always be heavier than it can be. At 435sq. in/1.54lbs dry weight, it's going to be a bit heavy, still flyable no doubt, but not the best for training. If you could lighten it at all, it would help you greatly.

At that point, I just go to eCalc and flyBrushless, plug in your dry flying weight, then start going through motors from my go-to motor supplier, Altitude Hobbies.

After a bit of toying around, it looks like the Suppo 2212/13 on a 3S with a 8x4.7SF prop would be the best bet. Pretty good thrust and battery life.

http://www.altitudehobbies.com/brush...-suppo-2212-13

And since you'll be drawing around 8-10A, a Suppo 18A ESC will be plenty, and give you one less thing to worry about.

http://www.altitudehobbies.com/brush...-brushless-esc

Suppo stuff is dead-simple to setup and use, and you'll get amazingly fast service from Altitude. It's my go-to motor store these days.
Thanks so much for the recommendations/advice!
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Old Oct 30, 2012, 09:26 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,681 Posts
Quote:
Originally Posted by loneboat View Post
They are CF arrows, so they have threaded ends. Those two shafts slide, so once I mount the motor on them (via the threads) they'll serve to adjust CG as well.
OK, that will probably work if you can get some rigidity into it. Otherwise the torque reaction from the motor and prop will twist the shafts.

You might want to take a block of foam (2" or so pink or blue insulation foam will work well) with holes drilled through it and run the shafts through that to make a sort of nose block.

On the front end of the nose block you can attach firewall made from a piece of 1/8" or so model plywood. You can probably attach the firewall with screws in the threaded holes in the shafts and also use some PU glue (Gorilla Quick for example) to also glue the firewall to the front of the foam block.

That foam block should give you some rigidity at the fuselage nose and also a provide a place to mount the ESC and receiver.

And then, in the link that acetech09 posted, that "X" shaped motor mount can be attached to the firewall with small wood screws. And it will also give you a place to add some washer to make a thrust line adjustment should you want to or need to.

I've made a couple of planes where I used arrow shafts PU glued into blocks of foam to get some strength into the foam fuselage. It worked well. I think just the shafts as you have them there, without the foam, would lack the rigidity and anti-twisting strength needed.

Jack
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Old Oct 30, 2012, 11:58 AM
Tim
United States, AR, Fayetteville
Joined Sep 2012
47 Posts
Quote:
Originally Posted by jackerbes View Post
OK, that will probably work if you can get some rigidity into it. Otherwise the torque reaction from the motor and prop will twist the shafts.

You might want to take a block of foam (2" or so pink or blue insulation foam will work well) with holes drilled through it and run the shafts through that to make a sort of nose block.

On the front end of the nose block you can attach firewall made from a piece of 1/8" or so model plywood. You can probably attach the firewall with screws in the threaded holes in the shafts and also use some PU glue (Gorilla Quick for example) to also glue the firewall to the front of the foam block.

That foam block should give you some rigidity at the fuselage nose and also a provide a place to mount the ESC and receiver.

And then, in the link that acetech09 posted, that "X" shaped motor mount can be attached to the firewall with small wood screws. And it will also give you a place to add some washer to make a thrust line adjustment should you want to or need to.

I've made a couple of planes where I used arrow shafts PU glued into blocks of foam to get some strength into the foam fuselage. It worked well. I think just the shafts as you have them there, without the foam, would lack the rigidity and anti-twisting strength needed.

Jack
Good point about the torque twisting the shafts - thanks for the foam-block suggestion!
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