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Jul 15, 2011, 04:46 PM
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So it's a single servo that drives a pushrod to bell-cranks on each servo? I would think simple torque-rods would work also. I might try that, though running 2 servos on a Y isn't a big deal these days, especially if you don't mind using the $5 servos from HK.
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Jul 15, 2011, 05:02 PM
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cherry629's Avatar
One servo in wing center,2 bellcranks rod from each meet in center of wing and were solderd together,this is the 3rd old kit built plane that I'v had with the same setup,this is the first that I got to work,This Stearman is a old Sterling Kit,64 1/2" wingspan,has a 120
Saito on it,it's heavy,Thanks Les
Jul 15, 2011, 06:17 PM
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E-Challenged's Avatar
Quote:
Originally Posted by cherry629
One servo in wing center,2 bellcranks rod from each meet in center of wing and were solderd together,this is the 3rd old kit built plane that I'v had with the same setup,this is the first that I got to work,This Stearman is a old Sterling Kit,64 1/2" wingspan,has a 120
Saito on it,it's heavy,Thanks Les
Use of a single servo was common in the 60's and 70's when most transmitters had only four channels.

I have the same setup shown on the plans of my old Sig 1/6 J-3 Cub. One servo for each aileron is easier to set up and is safer if one servo quits serving. You can also have differential ailerons with two servos if your transmitter is programmable for it using channels 1 and 6. If you angle the aileron servo arms forward, you can have mostly up and little down aileron motion similar to differential ailerons using a Y harness to channel 1 saving a channel for flaps or retracts.
Apr 18, 2017, 02:24 PM
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Finally getting started on mine. Stripped as much of the covering as I could... it came off the ribs and stringers pretty well, but really stuck down on the flat parts. When I bought it, I thought maybe it was covered in silkspan... but it's some kind of tissue paper. It was painted with a brush, brushstrokes one way, then perpendicular... so the finish looked like canvas. Had me fooled.

But what's the best way to get the rest of the paper covering off? I'm sure I could sandpaper it off, but that seems like a lot of work. Maybe acetone will loosen it up?

I plan to build mine up to look like this "Pemberton&Sons" Super Stearman. Built up turtle-deck with an AT-6 canopy over the rear cockpit, 4-aileron conversion, wheel pants, and pre-war Navy scheme.

Flying with the Pembertons (2 min 54 sec)


Pemberton 450 Stearman Acro (2 min 42 sec)
Last edited by warhead_71; Apr 18, 2017 at 02:32 PM.
Apr 20, 2017, 12:06 AM
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Getting it stripped down and repairing cracked ribs and stringers as I find them. Knocked out the shallow false floor so I can make a more scale cockpit. Debating whether I want to open up the front cockpit as well. And I cut out a square hole through the 1/2" ply firewall... that took forever. I'm going to build a slide-out power module... batteries, ESC, UBEC, motor, dummy radial, cowl... it will all come out as one unit. Also ordered some oleo struts that I'll mod to fit the wheels at 25deg, and braze up an aluminum torque-tube LG mount... similar to the real thing. Seems like it's built fairly light already, not sure where I get in with a Dremel to shave some ounces.
Apr 20, 2017, 11:35 AM
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Here's the gameplan for the oleo struts.

I'm starting with some slightly offset Oleo struts made for a P-47... HobbyKing has them for $35. I'll have to modify them on my grinding wheel to get the 25 degree axle angle. Then I'll build up the rest of the landing gear using some aluminum tubing and angle. I'll braze it all together with some low-temp aluminum brazing rods... should be pretty solid and let the Oleo struts do their thing. A lot cheaper than the 1/6 scale Robart robo-struts (almost $200)... which are hard to find anyway. I'll have to add a ply floor and hardwood braces that I can mount it to.
Apr 20, 2017, 12:45 PM
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You might find some helpful info in the gas to electric conversion forum. Modifying the fuselage to provide a motor battery compartment and easy access hatch so that you can locate the battery pack(s) right behind the firewall can involve some head scratching.
I like the setup on my Dynam WACO bipe. The top of fuselage from firewall to front cockpit removes for easy battery pack changes and is held by four magnets and U shaped metal keepers. Short nosed biplanes need battery packs located right behind the firewall and may need extra ballast in front of firewall to get CG right. moving other items forward such as elevator and rudder servos, etc. may reduce need for nose ballast. Don't attempt to fly tail heavy. Avoid heavy tail wheel assemblies or other unnecessary weight in tail. I like Monokote for a reasonably light , durable and easily patched covering on large models. Painting of Doculam can have masking/adhesion problems and patches after repairs punctures require repainting.

Good Luck!!
Last edited by E-Challenged; Apr 20, 2017 at 01:02 PM.
Apr 20, 2017, 01:19 PM
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I cut a 3.5" square hole through the 1/2" thick plywood firewall so I can build a slde-out power module. Batteries will actually be partially forward of the firewall, so I'll have all that weight as far forward as possible and hopefully won't require any extra ballast. I do plan to replace the heavy tailwheel with a lighter one. The heavy pushrods to the tail will be replaced with pull-pull lines. Servos moved up to the front cockpit. I'll also try to get my dremel in and hog out the formers a bit. Swiss cheese the ribs. And so forth. For covering, I'm going with the Hobbyking stuff. I've used it before. Lightweight and tough, similar to the Towerkote.

I have lots of biplanes... I know the drill.
Last edited by warhead_71; Apr 20, 2017 at 03:50 PM.
Apr 21, 2017, 11:41 AM
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I used battery protruding through firewall into cowl on my Tritle Reliant and a previous Berkeley Reliant and It worked well. Not a sliding tray setup but just a compartment with Velcro. I used a prop blade to release battery from compartment Velcro to enable removal.
Good luck with the conversion. Great old Sterling model.
Apr 30, 2017, 11:43 PM
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Oleo struts!!!

I deviated slightly from my above plans: I built the landing gear from 3/4" aluminum round tubing and 1" angle. These oleo struts themselves are not the ones I spec'd above either... these are meant for a 120-size plane but the perfect length for a 1/6 Stearman... I didn't have to add any extension tubes for the oleos. I still need to grind/drill a new angle for the axles. I did have to replace the springs with a lighter-duty ones as these are meant for a 20-30lb plane and mine will be only 8-10lbs, I hope. The whole thing is brazed together using benzomatic AL3 brazing rod and a regular propane torch. Ugly work... I needed a bit more heat. I might pick up some Mapp gas and touch up my blobs.

The gear will bolt into a 1/4" plywood floor that will be sturdily attached between formers F2/F3. I have lots of leftover angle-aluminum I can use reinforce the box-hole and LG floor.

Getting the old LG out was a huge chore. The infamous piano wire had apparantly splayed out during a hot landing and damaged the sheet balsa, cracked a hardwood support, snapped a few longerons... so the PO repaired it with copious amounts of wood blocking and epoxy. I had to drill out the mounting 4 bolts and cut the piano wire in 3 places with my Dremel cutoff wheel. After that, I was able to cut out more of that former so my power module can slide in deeper. That's my next project.

Pics aren't the best... my phone's main camera is busted so I have to use the selfie camera instead.
Last edited by warhead_71; Jan 09, 2018 at 05:44 PM.
May 08, 2017, 04:57 PM
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I actually rebuilt the LG legs using square tube as originally spec'd. I'm sure the round tube can handle more torque, but the square tube made it easier to mount both to the firewall and to the ply floor that was installed. I'll upload new pics tonight if I can remember. Got the axle mounts ground/drilled at the correct angle and set-screw into position so she is back on her wheels again.The stance is perfect and the oleos seem to work as advertised. I plan to use aluminum flashing to form a removable bellypan -- just like full-scale -- so I can get in and make adjustments/repairs if necessary. I'll also airfoil the legs with aluminum.

Next up: I'm working on the power module/box now. It's 3.5" square and 8.75" long... only the last .75" sticks out past the firewall to get the motor at the right depth. Big honkin' motor... it should really help keep her balanced. I can easily fit 4x 2200mah 3S lipos (series and parallel) all the way to the front of the battery box if I need lots of ballast in front of the CG. Or just a pair of 3300mah 3S in series. We'll see how she balances when I'm farther along. ESC and BEC will also affix to the module... hopefully I can hide it in the cowl with the dummy motor.
Last edited by warhead_71; Jan 09, 2018 at 05:47 PM.
May 08, 2017, 08:51 PM
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Biplanes without rigging wires look naked to me. I used chrome looking elastic cord from a sewing supply store. I made small eye fittings that glue into fuselage and wings. I made loops in ends of "wires" with aluminum tube "swages" and small S hooks to attach wires to eyes.
"Wires should be made to stretch slightly when attached. They will last about one year before going slack and needing replacement.
May 08, 2017, 09:12 PM
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Absolutely I'll add rigging wires. My Eflight Stearman has them. Tigermoth. Travelair. Even my Goose has them on the tip floats. On this Stearman I'm going to make scale-ish anchor points where rigging can attach to the struts. I usually use a small tension spring and non-stretchy silver cord (my daughter uses this cord to bead necklaces, etc). The cord never stretches much, but the springs keep it taut. I scavenge the tiny springs from discarded collapsible umbrellas. I usually find 2-3 umbrellas in the garbage every time it storms here... they can't handle the Chicago wind! Also a great source for small machine screws, piano wire, fiberglass rod... and I give the "canopy" to my kids to make into parachutes. ��
Last edited by warhead_71; May 08, 2017 at 09:33 PM.
May 08, 2017, 09:32 PM
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Proof of concept: The box slides in perfectly all the way back until it touches the front cockpit instrument panel. Probably deeper than necessary, but I'd rather have extra space than too little. Also gives me room to shift around batteries for balance.

It's a snug fit through the firewall plywood, but I need to add some "slides" to guide it through the second former.

I've also located the cross-pin that will hold the module in place. It will be disguised as the "snorkel" air intake on top of the nose of the plane. Perfect location for it because it just catches the inside of the battery box without taking up battery space. I'll add a brass tube to guide it.
May 09, 2017, 09:58 AM
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Also discovered that my cabane struts are a bit "sprung". Obviously she's done some ground acrobatics in her younger days. That piano wire is pretty stiff to bend in-situ... I'm afraid I'll crack or rip out the former if I pry too hard on it to counter-bend it back into place. Hardwood blocks are epoxied to the inside of the fuse where the cabanes exit and tore out some of the balsa planking -- PO's repairs. I think I'll just have to mount the wing-blocks to a 2x6 and twist it into position while I solder in some x-braces. This plane was also provided with a set of interplane struts that -- upon closer inspection -- do not seem to fit this plane. So I'll be making new N-struts as well.

For posterity's sake, anyone who stumbles across this thread and needs plans for the 1/6 scale Sterling Stearman, you are in luck! They are available at Outerzone:

http://outerzone.co.uk/plan_details.asp?ID=3704

Super handy to print out just the repair part that I need instead of trying to work off the crumbling and torn 50-yr old plans that came with the plane. Lucky for me we have a printer at my office that can do 12x18 sheets... big enough that I can fit major assemblies in a couple of sheets or design modifications on my computer overlaying the full plans.


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