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Yet Another OV-10A


daveculp
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I've started work on an OV-10A representing those based at Sembach Air Base, Germany in the 1980's (and at Patrick AFB, and maybe Osan (?)).  These airplanes had previously been based in Thailand during the war in SEA, so the airplane will have a lot in common with my previous Pave Nail OV-10A project.  I'll skip some things that were already covered in that build topic.  As with the Pave Nail project I decided to build it with the cargo door open.  External load will be one 230 gallon centerline fuel tank, two LAU-68 rocket pods w/ rockets, two B37K bomb racks with BDU-33 practice bombs and two guns in the right sponson only.  This airplane will also be equipped with the ALR-46 RHAW gear.

 

 

First some of the 3D printed parts:

 

3DP-parts.jpg

 

 

Column one shows the radio rack, O2 bottles, and hydraulic pump.

Column two shows the inlet covers, B37K racks, (?) antennas for the right boom (I think ILS?).

Column three shows the ALR-46 gear, gear handles, and emergency jettison button.

 

The bomb racks have been a real bear to print, in fact after I took the above photo I gave up on printing the racks with sway braces attached, and instead have printed bombs with the sway braces built in.  These then fit into simple notches in the racks.

practice-bombs.jpg

 

 

This gives the braces enough support to print properly.  I also made the airplane sway braces part of the rack, mainly because the carpet monster ate one of them, but also so they would sit properly on the flat top of the rack.  The BDU-33 should be slightly bluer, oh well.

 

As mentioned in the Pave Nail build the USAF OV-10A did not have a bulkhead behind the aft seat, and the aft cockpit itself is modified to remove the side consoles.  The Eduard photoetch set has the instructions and replacement parts for this modification.  In addition I added a rear wall to the cockpit floor where it meets the cargo bay floor, leaving small opening for wiring.  I'm using the AMS Resin seats, so the alignment bit on the floor needs to be cut off.

 

aft-cockpit.jpg

 

 

 

The seats will look sharp.  I'm also using the AMS Resin 230 gallon tank, here shown with one of the Euro One colors applied.

 

AMS-resin-parts.jpg

 

 

The cargo bay is shown here partly assembled.  I'm using yellow zinc chromate color.  I used green zinc chromate on the Pave Nail build.  The hydraulic pump is painted and installed.  5 mm is cut off the rear end of the ceiling to make room for the pump.  The floor is plywood color with two painted on aluminum slide strips running lengthwise and yellow zinc color on the edges.  The ceiling has the O2 bottles painted and installed.  I used chrome tape to make the bottle straps.  Radio rack is shown in position - the radios will be added soon.  The cargo bay side walls are made from thin styrene sheet.

 

cargo-bay.jpg

 

 

Closing up the fuselage halves is a bit tricky without the bulkhead since this means the ceiling doesn't have a solid connection at the front - just a butt joint on the sides.

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Cargo bay ceiling is finished and tacked in at the rear corner.  It's left a little loose to help with later adjustments.  Wire bundles and some oxygen lines added.  I'll add the radio rack and radios, then close it up.

 

cargo-bay-left-ceiling.jpg

cargo-bay-left.jpg

 

Note that the three ribs just aft of the hydraulic pump don't reach all the way to the center line, which will leave a gap once the fuselage is closed up.  The HF ground plate will hide some of it, but there will also be some putty needed to fill in some gaps.  Some photoetch sleeves would be a cool solution, but I don't have that technology :)

 

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So, this is second time I've had trouble closing up the nose of the fuselage, and I suspect that part F22 is causing the problem:

 

part-f22.jpg

 

The part doesn't fit well, there are no alignment marks, and the drawing is not clear enough.  I recommend a lot of test fitting here.  Maybe I'll have this part figured out when I make my third OV-10A.

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After installing the forward ALR-46 RHAW antennas I realized their position is not quite right.  They should be lower, lined up with the formation light, and they should be moved forward about 3mm.  I'm not going to move these, but for future reference - the kit position for this antenna is 1.5mm too high and 3mm too far aft.  These are 3D printed versions of the antennas.  The kit versions have a flat antenna - maybe that's a newer type antenna?

 

fwd-alr46.jpg 

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On 7/9/2020 at 6:29 PM, daveculp said:

So, this is second time I've had trouble closing up the nose of the fuselage, and I suspect that part F22 is causing the problem

 

 

I think you are correct.  I took several thousands off that part on my D and A both. 

 

 

 

Looking great btw!   Love watching another Bronco come together. Cant wait to get back to my A model at some point. 

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  • 1 year later...

After working with Thierry on the OV-10A/C tweak list I'm inspired to get back to work on my Sembach based OV-10A.  I started the finishing work on the ceiling of the cargo bay.  For some reason the kit designer left sizable gaps in the center of the ceiling beams.  Maybe he was afraid that close tolerances could prevent the closing of the fuselage halves?  In any case I've started the process of closing up these gaps.  Some of the gaps will be hidden behind (what I think is) the HF radio ground plate.  Also shown in this photo is the first steps in filling in the roof part over the cargo bay door.

 

 

cargo-bay-roof.jpg

 

 

 

I've modified the brass main gear struts by cutting off the fork from the right strut.  The main struts on the OV-10 don't need forks, as there is no way for the main strut to twist.  The left side has a squat switch which looks like a fork, but it's much more delicate than a fork.  The right strut has nothing there.

 

 

brass-mains.jpg

 

 

I'm now installing the 3D printed aft RHAW antennas.  The kit is missing these.

 

 

aft-rhaw-ant.jpg

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After going through the trouble of making the bomb racks and practice bombs I decided not to use them.  The load out will be four LAU-68 launchers with inert rockets.  This was a standard load for rocket practice and qualification at the range in Zaragoza, Spain.  I don't have four launchers, so I printed them as scaled-down versions of the 1/9 scale launchers I made for the giant scale project.

 

 

32scale-lau68.jpg

 

In this photo the 1/9 scale warheads are WP, so they're a bit larger than inerts.

 

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Well, it turns out that scaling down the rocket launchers doesn't quite work.  I was hoping to paint the 3 parts separately and then assemble them, but the tolerances just aren't close enough to make it work.  I checked around the aftermarket and see that Flying Leathernecks makes the "long" LAU-68 launchers in 1/32 scale, and I'd prefer short ones.  My plan now is to redesign my launchers as a single part.  One thing I like about the Flying Leathernecks launchers is they're empty, something that I hadn't thought of doing.  Empty launchers will print better, and I can always add rockets scratch built from styrene rods later.  For my build the new back-story is that the airplane just returned from a visit to the Bardenas Reales range and the pilot has already dashed to the O-Club for massive quantities of sangria.

 

LAU68-fail.jpg

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  • 2 weeks later...

After spending a couple weeks doing the filling and sanding required around the boom/wing/fuselage joints I decided the wings aren't straight enough.  Ooops!  I thought I had set that right when I glued it all together, and I thought the styrene spar would be enough to keep it straight.  Well, now I'll take several steps back.

 

bent-wing.jpg

 

I may have to remove the spar entirely and replace it with a brass one.

 

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  • 2 weeks later...
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