Scratch Build Design: Swappable Rockwell Bronco OV-10

[GunHog]

Servo connection and placement

“you're thinking of running the servo wire down one of the pods and up the rudder “

I'm thinking about it yes. Making the A to B connection is the most direct and less complicated method. The concern is something you and I have already referred to. With the twin configuration I’m not keen on placing a long control rod in the slip stream or in the prop wash. Flutter.

Now I’m quite sure your design will fly well, as it is based on a great AC.

I’ll bow out if any with more RC engineering and construction experience (Just about everyone as I’m an admitted noob) steps up and tells me it won’t be an issue. All I have to reference is my time as a pilot and aviation history buff. I read stories of the WWI pilots and their descriptions of flying aircraft (in combat) with exposed tension wires whistling and flapping in the air and early failing/limiting construction methods. IF I can avoid intentionally revisiting old mistakes I will.

I might waste a few foam boards figuring out a clean way and that’s cool. You’re making one of my favorite top 5 utility AC of all time. The AC130 is at the top of the list.

I work the next three days so no tinkering for me.

 

[GunHog]

Modeling info - OV10 Gear set http://shindinmachine.com/Bronco/bronconov05.html

Cool photo to drool OVer.

 

[GunHog]

This is close to my idea but with an aerodynamic cover over the servo box.

 

[JasonEricAnderson]

This is close to my idea but with an aerodynamic cover over the servo box.

AH I see! I was thinking you meant putting the servo out in the middle of the fixed part of the horizontal stab. This makes much more sense. I saw someone use a plastic spoon as a 'aero-bulge' type cover once.


Re: Photo
I knew there was a variant with a 20mm gun dome. This was the configuration of the plastic model I built as a kid and I hadn't been able to find a photo of a Bronco with the turret like that.

Last night I slapped together a wing minus the spar and realized I'm going to need to move the hole for the electronics pass through... since they don't currently lineup. I'm thinking I'll move the hole and notch assembly forward and try and center it in the space that the wing folds over.

This assembly was the last thing I added to the model so it figures that it would be way off. I need to rewatch that baby blender wing build video too.

 

[GunHog]

Servo

"I was thinking you meant putting the servo out in the middle of the fixed part of the horizontal stab. This makes much more sense. I saw someone use a plastic spoon as a 'aero-bulge' type cover once."

The plastic spoon was my first go to for a cowling covering the servo box...

I AM thinking of the center elevator for placement. I'm also wondering if a Clark airfoil (single fold with no spar) for the elevator rigidity would not be a bad idea. Then I started playing with single layer rudder mock-ups and they are very stable (like an egg) vertically but fragile laterally. This is a very beefy build, the only week link is the tail assembly if you think about the way the foam is used and stressed.

Just ordered the electronics for the build:
D2822/14 Brushless Outrunner 1450kv (USA Warehouse) x2 (Hope this is enough power)
HXT900 9g / 1.6kg / .12sec Micro Servo (USA Warehouse) x10
TURNIGY Plush 30amp Speed Controller (US Warehouse) x2
Turnigy 2200mAh 3S 20C Lipo Pack (USA Warehouse) x2


Three days to get everything cut and ready for electronics. Then I can measure everything for the wiring and harnesses.

 

[GunHog]

HobbyKing buddy codes for this build

D2822/14 Brushless Outrunner 1450kv (USA Warehouse)
http://www.hobbyking.com/buddy.asp?code=6FE3A61F-7D3D-4016-BC7B-5B2ED9B7E3D5

HXT900 9g / 1.6kg / .12sec Micro Servo (USA Warehouse)
http://www.hobbyking.com/buddy.asp?code=9CD92FB8-1F13-4572-9755-A6FF56F4DE16

TURNIGY Plush 30amp Speed Controller (US Warehouse)
http://www.hobbyking.com/buddy.asp?code=13AF833C-0CD8-427C-A9E5-72EC39AF010C

 

[Implicit]

The OV-10's main use wasn't for fixed wing ground support, but as a FAC. There were few braver men in the air than the FAC's and one of the absolute must-read military aviation books is Marshal Harrisons "A Lonely Kind of War".

 

[GunHog]

Build note: OK so B folding an A fold sucks..... just sayin.

Jason what was your plan for joining the wings and mounting them to the Fus?

 

[FeWolf]

The OV-10's main use wasn't for fixed wing ground support, but as a FAC. There were few braver men in the air than the FAC's and one of the absolute must-read military aviation books is Marshal Harrisons "A Lonely Kind of War".

Light Armed Reconnaissance Aircraft
YOV-10A - Original prototype.
OV-10A - Original production version. Distinguished by a long-wire HF antenna between the center rear stabilizer and the central nacelle.
OV-10B - Produced for Germany to use as target tugs, with a target towing pod mounted beneath the fuselage. A clear dome replaced the rear cargo door. The rear seat was moved to the cargo bay to look backwards out the dome.
OV-10B(Z) - A variation of the German target tug, with one J85-GE-4 turbojet mounted in a nacelle above the fuselage. A total of 18 aircraft were supplied to the Germans.[43]
OV-10C- Export version for Thailand; based on the OV-10A.
YOV-10D - The prototype used to developed OV-10D.

An OV-10D during trials aboard USS Saratoga in 1985OV-10D - The second generation Bronco developed by the U.S. Marine Corps. It was an extensively modified A-model airframe. The D-model added a powerful Forward-Looking Infrared night-vision system with a camera mounted in a turret under an extended nose. It is easy to differentiate a D-model from an A. The D has a long nose with a ball turret underneath, while the A has a short rounded nose. The D also has bigger engines, so it has larger fiberglass props that can be distinguished by their rounded tips. The A has squared-off aluminum props. Other noticeable external differences are the square chaff dispensers midway down the booms on the D-model (often covered with a plate when not in use) and infrared-suppressive exhaust stacks (they take air from the front and mix it with the exhaust before it exits, to reduce the heat signature given off and thus the ability of a heat-seeking missile to track the aircraft). The D-model began life as the NOGS program.
OV-10D+ - The next USMC upgrade, consisting of A and D aircraft being extensively reworked at MCAS Cherry Point Naval Air Rework Facility with new wiring and strengthened wings. Engine instrumentation was changed from round dials to tape readouts.
OV-10E - Export version for Venezuela; based on the OV-10A.
OV-10F - Export version for Indonesia; based on the OV-10A.
OV-10M (modified) - A four-bladed version of OV-10A; modified to accommodate bigger engines with larger fiberglass props. Equipped with square chaff dispensers midway down the booms and with new wiring and strengthened wings. Engine instrumentation was changed from round dials to tape readouts by Marsh Aviation for the Philippine Air Force.[44]

The proposed OV-10TOV-10T - Proposed cargo version of the OV-10, capable of carrying 8-12 troops or 4,500 pounds (2,000 kg) of cargo, studied during the Vietnam War but not proceeded with

 

[GunHog]

OV10 Build log 092413

First off, this is a really fun build. Thanks to JasonA for all his hard work!

Wings and spars
Cut and mated for alignment, fit and made the required modifications to the Beta plans. Very easy everything went together with no difficulty. Mods are very simple and won't be an issue with later build plans. I'm using the total board length so my OV10 will have a 60" wingspan. I'm going to be using a square wood dowel spar from pod to pod. At the wing join I'll cut the access port to pull power and control wires through and maintenance.

Pods (L&R)
Jason used the word "Tricky" when describing the pod folds. I'll leave it at that. Side note spending time making perfect cuts and then B folding an A fold makes you cuss in front of your 6 month old son. Luckily when I looked over at him he was chewing his toy contentedly drooling. Mom will never know.


Take your time with this. I used a skewer to help the tabs through. Suggest using a pencil and marking your glue run and fold target. I didn't got distracted and had to trash a pod for my lack of attention to detail.




The new plans (when edited by Jason) will have a reworked Vertical Stabilizer. I made the cut after measuring and testing the fit. You can see the shortened tail assembly and the right pod fitted.


I wanted to add some strength to the Vertical Stabilizers so I took bamboo skewers and cut to size. Cut a shallow slit the length of the skewer. Then glued them to the leading edges pushing them into the slit and making a nice round leading edge. I'll wrap with tape to seal later. Really made a noticeable difference.
I want to have access to my servos for repair and modification. So I will mount the servo on a-bit-o velcro and lock it in place with a tie wrap. In the photo below you can see the pop stick cut to size and drilled on the outer surface of the right pod. On the left pod you can see I notched the foam to fit the servo and placed a temporary tie wrap.

TIP: If you draw a line from the bottom angle of the rudder up to the join of the first angle in the Vertical Stabilizer you will have your rudder travel vector. Make aligning the servo and horn simple. Just visible on the left pod rudder (just above the servo) you can see the line I drew.

60" wing tip to wing tip (with out the end caps). I was working out how to place and location of the wood spar and also Aileron Servo placement. I'm thinking I'll mount the servo the same way I did for the rudders with an access hatch on the upper wing. Pop stick on the lower surface for the tie wrap.


More later.

 

[Implicit]

http://en.wikipedia.org/wiki/North_American_Rockwell_OV-10_Bronco#Variants

Providing source is always a good idea.

 

[Craftydan]

Gunhog,

Really looking nice -- Keep it up!

 

[JasonEricAnderson]

Gunhog, that looks brilliant. Re: Wing attachment. I'm planning to use the slot passthrough style connection as seen in the spitfire and others. I wanted to see what kind of profile the physical folded airfoil made and trace that back on the virtual/plans.

 

[GunHog]

Elevator Mod

Greetings from the mad mind of me on yet another mad scramble to build during my son's nap.

Note to Jason: On the next set of plans may I suggest you reposition the main wing spar to fall between two of the camber bends and not right on a bend. This will give you a better foil. I built another wing just to test it out and it works. It will also provide a nice flat surface to hold the glew.

OK so for the Elevator I made some changes and used a Clark foil design and inset the servo.

I used the JasonA plans for the bottom surface of the Elevator and then cut the upper surface to match minus the mounting tabs. I also cut a spar out. I had to cut another spar as the one in the photo is half too small. Thats what I get designing on the cutting board and not the CAD.

I reduced the Elevator profile to that of the main wing Ailerons. Measured my center line and then placed the servo just aft of the spar.


I used the same technique as I did for the rudder servos to mount the elevator servo. (Look back to previous post for refrence)


Turned out really well I think. Very low profile in the air flow of the foil. I will tape over the port to seal it off in the last stage of the build.



I'll drop the servo wires out a hole on the bottom surface of the elevator. I need to order some extensions that will run from the cockpit > wing > pod to the vertical tail assembly. Any exposed wire will get tapped in place.

Hope this stuff helps some one.

Cheers!

 

[GunHog]

Hey thanks Jason. I appreciate the kind words sir.

I would not use the word "Brilliant" as it would make me seem full of myself. BUT since YOU used it I will knowingly take your complement in the hopes that my great brain can assist you in some humble way during my free time between solving the questions of the universe and changing diapers......

 

[GunHog]

Hey guys I found this file for the OV-10 clear canopy.

View attachment paper-OV10-Bronco.pdf

I want to set the pilot FPV cam in the cockpit so this would be a cool addition to the build. Might also help in refining the foam version.

Hey Jason have you updated the fuselage to take the wings? If not I'm getting ready to do some cutting board CAD work...lol.

I think the H.F.T.E.T.O.F.B.G. (Humans For The Ethical Treatment Of Foam Board Group) are gearing up to protest me, I can feel it! SAVE ME FLITE TEST!!!

 

[FeWolf]

http://www.rcgroups.com/forums/showthread.php?t=1465021built this one

 

[Craftydan]

GH,

Keep abusing the foam. Get that OV-10FPV up and you can spot 'em coming!

The canopy you've designed, is that three of the same in that file? Is it flat or bubbled out like the full scale?

 

[GunHog]

Dan,
I did not make that file. I found it on another forum that was building an OV10. It is bubbled out like the full scale. Thats why I grabbed it. Might help Mr Jason with fine tuning the schematics. Now from what I read it's for clear plastic to be cut out for a canopy.

As for flying, well.....working on it.

 

[Craftydan]

Well hurry up, they're getting closer

I see that now. the blocky bubble in the foamboard plans is pretty good for what it is but if it could be replaced by a hatch cut from acetate sheeting . . .