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OV-10BZ Prototyping Parts


daveculp

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I've thought about doing an OV-10BZ for some time, but have been busy with other projects.  Today I thought I'd dive in and 3D print a prototype jet engine pod for the ICM 1/48 OV-10A kit, with an eye towards making all the conversion parts needed for the OV-10BZ.   First print looks promising.  I'll make some adjustments when I get some free time.

 

jet-v1.jpg

 

jet-v1-side.jpg

 

jet-v1-front.jpg

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3 hours ago, Silver Seraph said:

Hello,

 

For a first print, I would say it looks terrific :thumbsup:. If you plan selling, I would be very happy purchasing 4 sets.

 

Cheers, Stefan

 

Version 2 of the jet pod is done, and this will be used in my build.  In this version I printed it in four pieces, The main body, the compressor, the turbine, and the hatch.  Because I use a low-level type of CAD software I get faceting on the cylindrical shapes, and although this faceting can be removed with some primer and light sanding, I wouldn't call it "production ready".  I need to try designing this in parametric CAD, such as FreeCAD, in order to get an arbitrarily high number of facets so that they won't be visible in the final form.  I'd hate to sell something that is below expectations.

 

Here's a photo of current progress.

 

version2.jpg

 

The cockpit has the rear seat, bulkhead and controls removed.  The sponsons will not be installed, and this kit was not built for that, so the depressions have to be filled in and scribed.  That's a tedious process that is slowing down the build.   I'm going to build this with the cargo bay open, so the sponson shape on the inside of the fuselage had to be sanded down as well.

 

It's going to be tricky getting the fuselage assembled because the parts that assisted in keeping everything aligned, namely the bulkhead and cargo door, are removed.  The insides will be lined with ribs, and I'll scratch build a floor.  I put a brass spar in the wing, so the fuselage sides needed to be notched at the top to clear the spar.

 

After cutting off the cargo door, I assembled the halves and am preparing it for use as a mold to vacuform a clear door out of PETG.  This will make the clear door slightly oversize, but with it open 90 degrees I'm hoping nobody will notice.

 

Also in the photo is the 230 gallon drop tank I printed in resin.  As far as I know nobody makes this in 1/48 scale.

 

Another thing nobody makes in 1/48 scale is OV-10B(Z) decals.  I'll have to climb that mountain when I get to it.  The markings contain some white color, so it won't be easy.

 

The landing gear in this ICM kit are trouble.  They look super fragile, very complicated, and the instructions aren't clear enough.  I ordered a brass set from the same company that made the brass gear for my 1/32 OV-10s, but I decided not to use them here for various reasons.  So, plan C is to use a white metal set that appears to contain all the parts I need and should be strong enough to hold up all that resin.

 

-- Dave

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Engine pod is done except for blending the "feet" into the wing.  I wanted to paint the underside before attaching it to the wing, then I decided why not paint the whole thing now and I can touch up the feet later.  The 230 gallon drop tank is painted and only needs a filler cap decal, which I'll have to scrounge for.  The clear vacuformed cargo bay door (is it still a door?) is ready for painting.  Later I'll scratch or print the foot rests and mirrors that go inside the door.

 

This is my first time using MRP lacquer paint with Leveling Thinner, and I'm liking it a LOT.  I still need to source the orange paint.

 

17Sep.jpg

 

 

 

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Most of the paint is on now.  I used MRP-104 Light Grey for the underside, and MRP-208 Gelboliv for the top.  Orange is Tamiya TS-12 Orange from a rattle can.  Still have some orange areas to do.

 

I'm going with Plan D for the main gear legs.  I 3D printed a new set.  This is first time I've 3D printed a part because I couldn't figure out how to assemble the kit part.

 

paint-on.jpg

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I've got the main gear and external tank installed.  The main gear struts are 3D printed, only because I couldn't figure out how to build the kit or aftermarket struts.  They're holding up well.  What I like best about the one piece printed struts is that their geometry is built in, with no chance of error, assuming the initial drawing is correct of course.

 

The fuel tank is also 3D printed and is made of solid resin.  The weight of the fuel tank is enough to keep the nose of the airplane down, otherwise it would be a tail-sitter.  I can print the FRG flag decals, but the rest of the markings, namely the Bundeswehr cross and the aircraft numbers, are on special order from a European printer (Peddinghaus Decals).

 

In this photo I'm setting the airplane's pitch angle so I'll know how much compression I need in the nose gear strut.

 

 

sitting-angle.jpg

Edited by daveculp
Added name of decals printer.
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Waiting on decals, which could take a long time.  In the mean time I'm going to make a new clear cargo door using a 3D printed form.  I know I can make a better one.  I just redesigned the winch operators seat, and I'll print a new one also.  When I'm done with this I'll zip up all the STLs and post a link to them.  They're freeware.

 

Printed parts are:  jet engine (4 parts), 230 gallon tank, main gear struts, ILS antennas, cargo door form, fuselage cooling device.

 

Some things I didn't make because I don't have enough photos:  winch drum and motor, target brackets and cables, targets.

 

 

almost.jpg

 

Some notes on building this model:

 

1)   I used a brass spar - but that might not be needed really.

2)  The props are not in flat pitch, but they're kinda close (if you squint).

3)  I printed the main gear struts but used the kit nose gear strut.

4)  The kit pitot tube will break off, so get an aftermarket one.

5)  The most difficult part of the build is making the fuselage without sponsons.

5)  I used the kit decal for the walkway, which goes under the jet engine

 

 

 

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  • 2 weeks later...
42 minutes ago, MARU5137 said:

Brilliant work.

:clap2:

 

 

Thanks!

 

An update.  While I wait on the decals to arrive from Germany via Poland, I'm working on a new mold for the transparent cargo door.  Here's a photo of the real OV-10B  showing:

 

1.   The "door",  with asymmetric bracing

2.   The cooling device under the right wing

3.   No teardrop shaped fairing above the cargo bay

4.   Small vents on (both) sides of cargo bay

5.   Foot rests and mirrors inside the "door"

6.   The "towel bar" on the bottom of the door, which is part of the gust lock system

 

 

door1.png

 

I normally use AC3D for my CAD work, but this kind of part really requires parametric CAD (or, maybe blender?), so I'm using FreeCAD.  I'm still learning FreeCAD, so the best I could do is get the overall shape, with sharp edges, and I printed that:

 

 

door-mold.jpg

 

I'm sanding it down by hand now to get the right shape.

 

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Here are the STLs and some decal graphics that will be useful if anyone would like to make the OV-10BZ:

 

OV-10BZ-STLs.zip

 

*** EDIT:  newest version here:  OV-10BZ-v2.0.zip

 

You'll need a resin printer to make the parts.  I use the Chitubox slicer.  A different slicer might not work (let me know).

Three of the decals require white decal paper.  The prop logos/stencils require clear decal paper.

 

Ask me any questions you have about the process, either privately or in this thread.

 

-- Dave

Edited by daveculp
typo
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To make the clear door I first printed the mold and then sanded it down to round off the edges, then used primer/filler and more sanding to get a smooth surface.  I sprayed some engine primer (500 degF resistant) to protect the mold from the heat [is this necessary?  I don't know].  Then I added a one mm piece of wood (from a large tongue depressor) in order to make enough room for a radius at the bottom.

 

To make the masks for painting it I'm using a Cameo cutting machine.  It's a slow iterative process - draw on one computer using Gimp (at 300dpi 11.8 pixels equals one millimeter on the mask), then save it to a thumb drive, then load it into a Windows computer (which I have only because the Cameo machine has no linux driver), then cut it into the Tamiya masking paper, then test fit to see where adjustments are needed, then repeat.

 

 

masks-v1.jpg

 

 

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Got the transparent cargo door frame painted, and I have the winch operator's seat mostly done.  Decals arrived from Poland - and hopefully I'll have enough of the correct size to do the job.  I added some lead weight to the nose wheel well.

 

I also decided the main gear struts could be angled a bit more, and it's too late for this build, but I did make a correction in CAD and uploaded it to the archive.  The newest version is 2.0:  OV-10BZ-v2.0.zip   The 3 degree rotation of the new struts brings the main wheels a mm or two forward, which will exacerbate the tail-sitting tendency, and this will make nose weight necessary.

 

 

decals-here.jpg

 

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  • 1 month later...

Finally!  I see that Quickboost has made resin propellers for 1/72, 1/48 and 1/32 scale OV-10A/C.  These have the blades as separate parts, so I'm hoping this means the blades can be set at any angle.  If so then we finally have the solution to all kit makers providing propellers with the wrong blade angle.  (Except Kitty Hawk 1/32 scale).

 

https://www.aires.cz/en/catalog/?search=OV-10&searchButton.x=8&searchButton.y=7&category=18

 

 

-- Dave

 

EDIT:  I just ordered a 1/48 set and two 1/72 sets.

Edited by daveculp
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