NA OV-10A Bronco (oz15807)

 

NA OV-10A Bronco (oz15807) by Walt Mooney 1967 - plan thumbnail

About this Plan

NA OV-10A Bronco. Simple profile scale model twin, for rubber power.

Direct submission to Outerzone.

Update 27/1/2025: Added article, thanks to RFJ.

Quote: "An exciting twin engine semi-scale rubber powered free flight by the old Professor. North American's STOL or COIN plane is a good subject. NA OV-10A Bronco, by Walt Mooney.

COIN - A counter insurgency aircraft. A high performance, short field aircraft designed to perform multiple missions while operating off unimproved fields or narrow dirt roads. This requires an aircraft with a short span high lift wing, high power, large body and external store pylons. It also has to have long stroke shock absorbers on the landing gear. North American's COIN, Lara, OV-10A, or by any other name, short field multi-purpose airplane has all of these.

At the first glance it would not appear to be a good subject for a rubber powered scale model - but ha!! it really is - at least if you'll allow me to call an all-sheet model scale. True, it's a profile, but it has a scale tail area, its dihedral is scale (none at all) and its side view is correct. It's also twin-motored, and will fly really well and is, of course, easy to build. Well,not quite as easy to build as a single motor job because two propellers have to carved, one right hand and the other left. But that's not too hard and the rest is a snap.

The plans are drawn to be printed full-size, at least all the complicated parts are full-size. The wing and horizontal tail and store pylon are small scale but they are simple and are dimensioned. With the exception of the wire landing gear and motor hooks, the airplane is all balsa. Medium rather than soft balsa should be used for this model because the booms are held together by the wing and horizontal tail near the top of the twin fins.

The original idea was tested with a six-inch span profile glider to see if we could get away with no dihedral (I guess I always suspected it would work) and lo and behold, an exact scale model was stable as could be. So no dihedral and a scale profile twin of modern aircraft that looks right and flies like the real thing.

Our model is so simple that most of the construc-tion is omitted except for the following: Cut all the balsa parts as shown on the plans and sand smooth rounding the edges. Bend the wire parts and assemble the model - hold it, don't assemble it yet. As we should talk about a few items.

Decoration: While the parts are all flat, it's easier to use several felt pens to draw control outlines, insignia, windshield outlines, and other numbers letters and signs as you desire. Photos of the OV-10A have appeared everywhere it seems, get one to be your guide and do it before assembly.

Propeller carving: Select a block long enough to make both propellers as they have to be of similar weight. Then carve them at the same time so that they can be compared as you go along as they should have same pitch and form. Be sure they are opposite hand or else you'll end up making three. It would help to have two heads and the hands to go with them but what I mean is: do each step of the job alternately, first on the left hand prop and then on the right hand prop comparing your progress as you go along. Then they will match. Don't get tempted into finishing one of them first.

A simple free wheeling device will im-prove the models glide but none was fitted on the original model so it makes STOL descents as well as ascents. Propeller Installation: Cut the two shaft bearings from a length of 1/16 OD aluminum tube. Drill a one sixteenths diameter hole in the front of each boom and cement the tube in place. It should ex-tend beyond the balsa wood a little bit fore and aft and the cement should coat this to make a better bond. Also a coat of cement should be applied on the out-side of the boom in the area of the bearing to strengthen it. Next thread the hook through the bearing, thread several wash-ers on the hook and then poke it through the propeller hub and bend it over as shown on the side view.

One precaution should be observed, make sure the propellers are situated so their rotation is as shown in the front view. This makes their slipstream rotate opposite to the wing tip vortices and thus improves performance by increasing the effective wing lift. Flying: Some ballast will be required to get the center of gravity where it belongs. Add some clay to the nose, it's obvious in the photos. Install motors made of a loop of one eighth flat rubber using an 'S' hook at the aft end.

An eggbeater modified for winding does an excellent job. One is visible in one of the photos [pic 005] and the modification is easy to do. Hook the 'S' hooks on the winder, get a helper to hold the model by the props and wind it up. It should jump off the ground after a very short run and climb in a straight line at about a forty-five degree angle. Without a set of free wheeling props it will glide steeply but so does the real ship. The original which flew right of the drawing board, (that clay was added prior to the first flight, not afterward) has done over forty seconds and averages around thirty.

So double your pleasure, double your fun, fly a twin. "

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NA OV-10A Bronco (oz15807) by Walt Mooney 1967 - model pic

Datafile:
  • (oz15807)
    NA OV-10A Bronco
    by Walt Mooney
    from Model Airplane News
    September 1967 
    14in span
    Scale Rubber F/F Multi Military Bomber
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 14/01/2025
    Filesize: 122KB
    Format: • PDFbitmap
    Credit*: TomBinkley
    Downloads: 309

ScaleType:
  • North_American_Rockwell_OV-10_Bronco | help
    see Wikipedia | search Outerzone
    ------------
    Test link:
    search RCLibrary 3views (opens in new window)


    ScaleType: This (oz15807) is a scale plan. Where possible we link scale plans to Wikipedia, using a text string called ScaleType.

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NA OV-10A Bronco (oz15807) by Walt Mooney 1967 - pic 003.jpg
003.jpg
NA OV-10A Bronco (oz15807) by Walt Mooney 1967 - pic 004.jpg
004.jpg
NA OV-10A Bronco (oz15807) by Walt Mooney 1967 - pic 005.jpg
005.jpg

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