Funbuild 5 Stinson Model A Tri-motor - Page 4 - RC Groups
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Jan 28, 2012, 07:26 PM
It's a Great Day to Fly
LenBFP's Avatar
I went out and looked at what was on the motor, it was a 7x5; the memory is not what it once was. It does crank with that prop, it is one of the HK props.


The spreadsheet looks fine. It looks like a 6x3 is the sweet spot for the 10 gram motor.
Last edited by LenBFP; Jan 28, 2012 at 07:38 PM.
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Jan 28, 2012, 08:17 PM
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glewis's Avatar
Yeah, 6x3 and the 5x4.3. I was thinking about clipping a 7x3.5 down to 6" and testing it too.
When I get the 45" span plan from Cleveland I might reduce it to 40". Then a 6" prop would be the scale size. Heck, I could just use the 6" on the larger model and get over the slightly smaller than scale prop.

Jan 28, 2012, 09:10 PM
redlite's Avatar
Sub'd...rare subject, this will be fun...

Jan 29, 2012, 10:01 AM
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E-Challenged's Avatar
Glad to see you not get it all built, have a bad maiden, and have to up-convert to more power setup. Many of the twin or more motor designs will be challenging in terms of selecting the right power system compromize and keeping wing loading down to where the model is a pleasure to fly. I have built a number of too-heavy models that only get one flight per session and have to go home for landing gear repairs. The real Model A wasn't really a floater and seemed to get around with authority.
Jan 29, 2012, 01:03 PM
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glewis's Avatar
I hear ya man. Already made that mistake three times now.
First time on my Guillows B-17 then the Hughes Hercules and the Sterling Black Widow.

The B-17 flies, but barely and could use more power. The power system is already as maxed out as it will go and will have to be replaced.

Used surplus cheapie motors on the Hercules and it barely flew. Upgraded to the same size N-20 motor but a lower Kv version and it flies good now.

The Widow flew ok on the 4 blade props but was down on power. Changed to 2 blade props and flies good but I want to use the scale looking props. Have a pair of blue wonder motors to re-power it with.

Once I see the Cleveland plan I'll have a better idea what power to use. I might be able to use the 10 gram motors if the structure is light enough, but somehow I doubt it.... This time I'll err on the side of too much power if possible and use something that I can add a cell if necessary.

So now sitting here I'm twiddling my thumbs waiting for the plan to arrive and need something to do in the meantime.
Went sniffing around my stash and found a 17.5" span Dumas Cessna 337 kit. Humm, I have an AR6400T out of the PZ Mosquito that I could use....
Enter a kit AND a plan built model in the same funbuild? Who me???

Last edited by glewis; Jan 29, 2012 at 01:08 PM.
Jan 30, 2012, 06:24 PM
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glewis's Avatar
Ordered the plans Saturday and no confirmation email.
Hope this isn't an omen....

< tapping foot impatiently >
How 'bout now....

Maybe I should use this downtime to make up a set of motors. I need to spend some time at the lathe turning bearing tubes and radial mounts anyway.

Jan 30, 2012, 09:06 PM
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E-Challenged's Avatar
A little extra power is a good thing. I would make up three scale props for display and fly with what works. Problem is getting tiny outrunners with low enough KV to spin relatively large props on 2 cells with an option for 3 cells and (smaller props) if needed.
Getting plans from Cleveland may take some time, it's a small part-time operation but they eventually deliver.
Jan 31, 2012, 12:21 PM
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glewis's Avatar
Think I've decided to just go ahead and make my own motors.
This way I can tailor the kv to a specific prop.
I'll start out with the 20mm stator size and if they prove inadequate I can swap in a set of the biggger 22.7mm ones.

The bearing tube is the same size for both versions so the radial mounts won't have to be removed. A motor swap is as easy as loosening the retaining set screw, pulling the motor out of the mount, stick the bigger version in and tighten the screw.

I checked my stock and have only one bearing tube left.
Looks like I'll pass the time waiting for the plan by running the lathe and making up a set of motors.

Jan 31, 2012, 01:37 PM
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E-Challenged's Avatar
Next you'll be rolling your own speed controls. Isn't that fine wire for low KV tedious to wind neatly onto tiny stator arms? I'm impressed!!
Jan 31, 2012, 02:44 PM
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glewis's Avatar
It's actually easy to wind, it's the keeping count that's the hard part. Sometimes you have to unwind a turn or two to get the wire to lay just so, then was that 9 or 10 turns? Crap! strip it off and start over....
Really suks if it's at the end of the third coil and all the wire on that phase has to come off...

Nope, the parts to make my own esc would cost more than buying one already made. Same deal with motors, but there is some benefit to winding my own in being able to customize the Kv.
Jan 31, 2012, 04:38 PM
Registered User
Originally Posted by E-Challenged
Next you'll be rolling your own speed controls. Isn't that fine wire for low KV tedious to wind neatly onto tiny stator arms? I'm impressed!!
Me too, that's pretty hard core.

I'm sure I saw one of these at EAA in recent years and I'm sure I would have photographed it because it is so unusual. If I can find the files I'll post them.

Jan 31, 2012, 05:52 PM
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glewis's Avatar
Thanks guys.
Guess making my own motors isn't a big deal for me.
Custom wound my rc car motors way back when too, so this is just an extension of that insanity.

Been doing it since the very beginning of the cdrom conversions. Would strip down a pile of cdrom drives to find only a few motors that were suitable for conversion. With parts from it got much easier.

Now with the cheap motors from China it isn't worth the effort unless I need something that isn't available. The parts to make mine cost more than a lot of the motors available from Hobby King.

If you can find your pics please post them! I haven't found that many pics of this aircraft online.

Last edited by glewis; Feb 01, 2012 at 06:40 AM.
Feb 01, 2012, 12:00 PM
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glewis's Avatar
Spent some time at the lathe last night making some aluminum swarf.
Got 4 good bearing tubes turned and screwed up a 5th one. I'm no professional machinist and do manage to make a few,,, make that many, scrap pieces...
I only have enough 20mm motor parts to make 5 motors so tonight I'll make up the last tube and the radial mounts.

Not sure what the prop size will be yet.
I fired off an email to the Golden Wings Museum and asked if they could provide some info on the diameter of the full scale prop.
I received a reply from Craig at the museum within 5 minutes!
He said he will go measure the prop on the aircraft and get back to me!

Feb 01, 2012, 03:17 PM
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E-Challenged's Avatar
Craig at the museum should be able to provide landing gear details and maybe suggestions for modelling it.
Feb 03, 2012, 09:06 PM
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glewis's Avatar
Here's the reply I got from Craig at the Golden Wings Museum.
I asked him about the landing gear and he took some pics and sent them to me.
Thanks Craig!

From: Golden Wings Museum []
Sent: Friday, February 03, 2012 10:59 AM
To: Glenn Lewis
Subject: RE: Stinson model A

The propeller is 99 inches long. I believe they are Hamilton Standard blades. Attached are 5 photo's of the main gear. Again, I'm not exactly sure of the retract mechanisms work, but hopefully these will help you.

Please send me progress photo's of your model, we're always interested in seeing models of these aircraft.

Good luck!


Looking at the pics of the landing gear now I'm really confused....
Combo oleo strut and hydraulic cylinder?


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