OV-10 Bronco Replica- Redux

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Sockmonkey

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Why not electric? Have two powerful electric motors (geared) turning big props and a generator behind the pilot? This would solve both the CG challenge and the small nacelles. Add a small (5 min power) battery and you have twin-engine reliability for EFATO.
Would also let you have blown flaps.
 

Staggermania

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So it's been a year and a half, and I have decided to really get serious about designing the Bronco Replica, so I thought I'd revive the thread.
I was able to purchase and download a 3D model in Solidworks, and it's interesting that the sketch I did a couple of years ago was very close to the 3D model in size, after I reduced the scale. My wetted area was about 20 sqft more than the model.
The model was pretty close to actual specs, but the wing span was a little longer than stock.

Anyway, a scale of about .815ish seems to work pretty well, although I might cheat some towards the tall side with the height of the fuselage. This gives the following dimensions(approximately)-

L - 34' Cockpit Height 4.5 ft
Wingspan - 33' Cockpit Width - 30"(outside)
Chord - 6' Boom Width at Wing 22"
Wing Area - 198 sqft Empty Weight - 2200 lbs
Wetted Area - 981 sqft Fuel - 60-80 gal
Engine - IO-540 - 300HP Cruise - 150kt
maybe LS w/PSRU later on. Stall - 60kt
Seats - 2 GTOW - 3200lbs

This will be a single engine pusher. Would like to stress for basic aerobatics. Also will have cargo area/extra passenger under wing.

I would like to design it in solidworks, but I don't know if I have the energy or patience to really learn the software. I like drawing by hand, and so will probably go that route. Would probably be faster, anyway.

I am thinking wood construction, as I am a carpenter, and enjoy working with the stuff. There aren't many compound curves, and those would be done in FG. I am not ruling out other materials, however.

I don't think that composites would be high on the list. This is a large aircraft, and would require way too much time in plug and mold construction. I would actually like to finish and fly this thing one day:)

Steel tube covered in plyood, aluminum or composite skin could work as well, with aluminum wing.

Would appreciate opinions on airfoil. Original was 642A315. Keep it? Replace it?

Anyway, I would welcome any input on all aspects of design.

Thanks in advance:)

Bronco.jpg
Bronco 3D.JPG
 

cluttonfred

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That's an ambitious project both technically and financially, I hope you get there!

Personally, I also like the Bronco look but I would go with something smaller. The Royal Thai Air Force built two RTAF-5 single-engine turboprops much like a smaller, pusher prop Bronco. I could see a still smaller, simpler design making a nice piston-engine sport plane. You'd probably need to lower the wing somewhat to move it forward so the passenger is sitting on the neutral point and maybe aluminum spring fixed gear on the fuselage instead of the spindly legs retracting into the booms. The view would be great!

0028678.jpg RTAF-5 3-view.jpg
 

Victor Bravo

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This may have been discussed already, but I would suspect that a significant amount of lift and/or control power on the original Bronco came from propeller blast over the wings. So lengthening the wingspan by 10-15% may be required for the darn thing to fly acceptably.
 

Staggermania

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That's an ambitious project both technically and financially, I hope you get there!

Personally, I also like the Bronco look but I would go with something smaller. The Royal Thai Air Force built two RTAF-5 single-engine turboprops much like a smaller, pusher prop Bronco. I could see a still smaller, simpler design making a nice piston-engine sport plane. You'd probably need to lower the wing somewhat to move it forward so the passenger is sitting on the neutral point and maybe aluminum spring fixed gear on the fuselage instead of the spindly legs retracting into the booms. The view would be great!

View attachment 92329 View attachment 92330
Well I'll be ding dong danged! If that ain't a lowered wing Bronco replica, then I don't know what is!

Definitely not going to lower the wing, or change the landing gear, but I get your point. My goal is to get the look as close to the original as I can. Otherwise, it's just another design exercise. :)

IIRC, when last I ran the numbers, the passenger location worked out okay.
 
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Staggermania

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This may have been discussed already, but I would suspect that a significant amount of lift and/or control power on the original Bronco came from propeller blast over the wings. So lengthening the wingspan by 10-15% may be required for the darn thing to fly acceptably.
Dont know much about that. If anyone else does, please chime in. It looks like the Thai aircraft's proportions are similar in scale to the Bronco, though I don't know that means anything.
 

vhhjr

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I have looked at several tandem aircraft as reduced scale replicas and the CG is tricky, especially with and without a rear seat passenger. You may have to carry a small movable ballast to accommodate various passenger weights.

One big advantage of designing in CAD is that you can cut out parts on a CNC router, water jet or laser cutter and end up with what looks like a giant scale radio control model kit. There is a Facetmobile being built in EAA chapter 292's hangar that all the tubing for the frame and all the joint gussets were cut out on a chapter members 4 x 8 foot CNC router. The resulting frame tubes all fit together with "no daylight" joints and all the rivet holes were pre-drilled.

Vince Homer
 

Toobuilder

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Although I'm also drawn to the Bronco look (and have even sketched a single engine version), one has to look at your preliminarily specs. Keeping in mind it's nothing more than a 2 place sportplane with a 540, it's hard not to notice it is 2 TIMES the empty weight of another 540 powered, 2 place, aerobatic sportplane - the Harmon/F1 Rocket. Your airplane is also 50 KNOTS SLOWER in cruise, and lands faster. Your ROC is also going to suffer substantialially.

Designing a new airplane is a lot of work - are you willing to give up substantial practical performance just for a "look"?
 

Staggermania

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Although I'm also drawn to the Bronco look (and have even sketched a single engine version), one has to look at your preliminarily specs. Keeping in mind it's nothing more than a 2 place sportplane with a 540, it's hard not to notice it is 2 TIMES the empty weight of another 540 powered, 2 place, aerobatic sportplane - the Harmon/F1 Rocket. Your airplane is also 50 KNOTS SLOWER in cruise, and lands faster. Your ROC is also going to suffer substantialially.

Designing a new airplane is a lot of work - are you willing to give up substantial practical performance just for a "look"?
Yes.
 

Toobuilder

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Well, let's hope that enthusiasm sticks around after you've flown it a few hours. You will be a rare one if it does. Note the Baily Bomber isn't exactly tearing up the airshow circuit.
 

wktaylor

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The OV-10 Bronco Association/museum [Ft Worth TX] has lots of examples of the Acft and great/unique tech data... and is open to support projects by individuals of all 'interests'. I was the lead structures/mechanical engineer for USAF OV's [at SA-ALC] in the mid 1980s... and donated some unusual maintenance tech data to the Org.
https://www.ov10bronco.fortworthaviationmuseum.com/

RC Model...
 

rhbelter

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Ahoy, you Replica OV-10 Builders,

More than FIFTY years ago, I was the Attack Branch Head at the Naval Air Test Center, Patuxent River MD.

The original OV-10 showed up for NPE -- Navy Preliminary Evaluation --.

My first observation was: You ain’t going to sneak-up on a Viet-Cong with those howling turbo props.

Second, the critter had a 30 foot wing span.

I remarked to Roger, my project test pilot:

When you lay that thing over and pull on the pole, it is going to stop dead in the sky.

Next time we saw it, it had a 40 foot wing.

Nice flying airplane.

Enjoy /s/ Bob -- EAA 8444
 

Staggermania

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Well, let's hope that enthusiasm sticks around after you've flown it a few hours. You will be a rare one if it does. Note the Baily Bomber isn't exactly tearing up the airshow circuit.
I guess I should say that I’m not thinking fully aerobatic. I think gentleman’s aerobatics might be the correct term?
Of course, I would like to squeeze as much performance as is practical from the design.

Look, I have bounced around all kinds of different build ideas over the years, but there are simply too many very cool aircraft ideas too choose from, and I keep coming back around to the Bronco.This is the one that really get the juices flowing, so to speak.

I figure I’ve got time for one project like this(design-build), as it will take several years to complete, and I am almost 53.
So to your point, no, it is not going to be a barn burner, nor a show circuit favorite, or a very practical airplane, but it is going to something that will, god willing, challenge me in many different ways, put a smile on my face, and keep this brain of mine humming along.

And so any help and knowledge that I can gain from you all to see that my vision can become a reality will be greatly appreciated.
 
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Staggermania

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The OV-10 Bronco Association/museum [Ft Worth TX] has lots of examples of the Acft and great/unique tech data... and is open to support projects by individuals of all 'interests'. I was the lead structures/mechanical engineer for USAF OV's [at SA-ALC] in the mid 1980s... and donated some unusual maintenance tech data to the Org.
https://www.ov10bronco.fortworthaviationmuseum.com/

RC Model...
Thanks for the link. Lots of good info. Seems some of the links on the site are no longer active. I would like to find that movie, “One tough ride”
 

Toobuilder

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As long as you are going into this with eyes wide open thats great. I have seen many an experienced design engineer fall in love with a concept and as a result are blinded to even obvious performance trade deficits. I get that your "mission" is the journey and not the destination.

With that said, my first version of the Bronco concept was as a cheap, easy airframe (lots of wood, too), but also was going to use a V-8, direct drive. The "mission" of my bird was primarily to explore the direct drive V-8. With this airframe configuration the engine can be mounted upright, and with a very simple prop drive. It would not be the lightest or the fastest, but I hoped it would be acceptable and affordable. Proving that concept one way or another WAS my mission. So I get it.

So... Ever thought about a V-8 instead of the Lycoming?
 

wktaylor

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Humble 'salute' to EAA 8444... tough work and ultimately great choice!

NOTE.
In the 1980s I was USAF [SA-ALC] lead structures/mechanical engineer for the O-2A, OV-10A and then A/T-37s... for~6-years. I encountered the OV in significant technical depth... and had a couple of test flights to evaluate mechanical issues.
xxxxxxxxxx

BTW... my true favorite combat aircraft of all-time is the A-37[A/B] dragonfly... a simple-efficient-compact killing machine... same genera/era as OV.

A-37B~Vietnam1.jpg

A-37A~VietNam3.jpg

A-37B Cutaway~LargeY~opp.jpg
NOTE.
A-37s flew in-conjunction with FAC O-2s and OV's on many thousands of missions. In-total, a couple-of hundred [~250?] USAF A-37s racked-up ~70,000 USAF combat sorties over ~6-years in VN... with the airborne combat loss [shoot-down] of about 12 Acft [many more lost to accidents and on-the-ramp rocket/artillery/sapper attacks].

More than once, A-37s followed OVs or O-2s thru dangerous low ceiling/visibility 'sucker-holes' in relief of ground units under high-threat of being over-run by the VC/NVA [danger-close employment of BLU/BDUs, 2.75-rockets and 7.62 strafing]. To this day there is a tight/brotherhood bond between A-37 and OV and O-2 associations.
 

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Staggermania

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Ever thought about a V-8 instead of the Lycoming?
Yes, but my plan is to get the airplane flying and work out any issues with the airframe with a certified engine, then possibly try an LS with PSRU. Or, assuming I have the winning lotto number in my wallet, a turbo-prop.
 
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simflyer

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So it's been a year and a half, and I have decided to really get serious about designing the Bronco Replica, so I thought I'd revive the thread.
.....
L - 34' Cockpit Height 4.5 ft
Wingspan - 33' Cockpit Width - 30"(outside)
Chord - 6' Boom Width at Wing 22"
Wing Area - 198 sqft Empty Weight - 2200 lbs
Wetted Area - 981 sqft Fuel - 60-80 gal
Engine - IO-540 - 300HP Cruise - 150kt
maybe LS w/PSRU later on. Stall - 60kt
Seats - 2 GTOW - 3200lbs
.....
Would appreciate opinions on airfoil. Original was 642A315. Keep it? Replace it?
What about Harry Ribblet GA37-A315 airfoil, or about new airfoil used on KR2S ?
 

cluttonfred

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Now you guys have me thinking about a Bronco-like LSA ("Honey, I shrunk the RTAF-5!") with an upright 100 hp Suzuki G13 conversion and the rear seat raised enough (12"/30 cm?) to give the passenger a better view. The view from the front seat would be outstanding.
 
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