1/72 AP-2H TRIM Neptune

[Beekster]

Thanks, Gents! So much to do yet but the major elements are coming together. Finally. There's probably stuff I could do to the landing gear bays; lots of wiring & piping in there. I might troll the internet for reference; all I have are a couple of ancient 35mm photos I took of the survivor at Pima in the late 1980s. I should look anyway...this is what the front of the main gear bay looks like:


I'm pretty sure that open area is a vent of some sort on the underside of the engine cowling, but I'd like to know for sure. I think I ought to do something to make that look better, to say nothing of filing the seam on the gear bay bulkhead below it. More sleuthing to do...

[JCON]

Yeah that's a pretty big empty spot! Filler or plastic sheeting will cover it if its not supposed to be there. Good luck finding it Sherlock.

[Beekster]

Well, Joe, I have found some useful images floating around the ether. That open spot on the underside of the cowling holds a pair of big cylindrical oil coolers. Didn't take much time with Evergreen tubing, strip, and punched discs to dress up that area...especially since it will be painted black in there anyway.


The images I've found will allow me to add a few things to take up some space in the gear wells, so more on that as work progresses.

[JCON]

That's excellent news! Glad you got it figured out quickly and sorted so well! Joe

[Beekster]

Let's talk about the mufflers/flame arresters for the big reciprocating engines. There were six of these things, one for each of the three exhaust outlets on each engine. Each of these was made of three nested half-cylinders with air gaps between them, fitted to a base plate which was attached to the cowling. This is what the In-Country Hobbies parts look like. They're not too bad, except for one thing: Like anything resin, they are solid through and through.


That's clearly suboptimal. In the old FSM article, the modeler cut up an aluminum pie plate and bent the parts around the shanks of drill bits, superglueing them to the base plate. That seemed both messy and imprecise to me, so I've started work on these using Evergreen tubing and strip stock:


Here are most of the necessary bits laid out. At the top are the largest half-cylinders, made from .250" tubing. They have been trued up, the edges beveled, and been ground down to size. Below them, the .188" parts are attached to spare strips and are ready for the trueing and shaping process. The smallest .125" parts are seen loose, as are the base plates. I haven't cut the extended rods yet; those will be done when the rest of the assemblies are together. These are possibly overscale, but pretty close to the resin bits in size. The dimensions given in the FSM article seem too small; certainly the spacing of the nested portion is. He would have you showing only about .040" of each piece from the edge of the next larger one. In-Country got that closer to right, based on images taken in-country during the war. Should be more like .080"-.100". I will play with that and compare to images once I can assemble the first muffler and test-fit it to the engine.

[JEFF]

Very nice bunch of white stuff,Beeks. What you're doing will make a big difference in this build.

[JCON]

Now that is what separates the men from the boys right there! Excellent scratch building taking place! Well done Beekster!!!

[Beekster]

The exhaust mufflers/flame dampers for the reciprocating engines are now done:






There's a clear gap between each of the half-cylinders running most of the way through the assemblies, and once they are painted black in there everything will be in deep shadow anyway. and here's what they look like on the engine cowlings:





The Neptune had two identical engines, not left and right versions like some other aircraft. Thus, both propellers turned in the same direction. This was done to minimize cost and maintenance complexity.

Next up are the ordnance pylons for under the wing, which all have to be made from strip stock. There's ten of them. Also in the assembly stage is a fixture to help with aligning the propeller blades to the hubs. That operation will be a fraught endeavor because the attachment pins are quite small and very fragile. The long OOP metal props from Aeroclub are nowhere to be found. Should have bought those thirty years ago while I still had the chance.

[Beekster]

And some progress on the propellers. This morning I built a fixture, and so far so good on building the props:




The structure is Evergreen strip stock, built up to allow the spinner to lay flat on top and the shaft to remain clear of the ground plane. With that dried and a hole for the shaft drilled, I dry-fitted a blade and used strip and angle stock to make the support that holds the blade at an angle. This was done using the highly accurate TLAR method (That Looks About Right) to select the pitch of the blade. Once the support was dry, I glued the first blade to the hub and left it to dry. Once it had set up a while, I pushed the spinner up from underneath, rotated it 180 degrees, and dry fit another blade. At this point, the first blade hasn't fully set so I could still work with it. I made another support structure on the outside to support the blade to prevent accidental breakage. So far, so good. I then glued the second blade in place. After a while, I pushed the spinner up again to rotate 90 degrees and add the third blade and later still the fourth. One prop done, one to go...

This fixture is specific to these props, at least for now. By slicing off the blade alignment stuff on top and drilling new holes for different diameter shafts, I can rebuild it as needed for other four-blade props that use this same assembly process.  Of course, if you left- and right-handed prop rotation, it makes sense to build two similar fixtures (it's hard to see, but the angle that established the pitch is installed at a slight angle to the blade axis, not quite parallel).  And making this for a three-bladed prop is harder, requiring math & geometry that I haven't used in decades.  Your mileage may vary, as they say.

[JEFF]

Sweet Mother of Pearl.

[JCON]

Dec 15, 2023 9:08:08 GMT -6 JEFF said:

Sweet Mother of Pearl.

Yeah, what Jeff said sums it up well!!! Wow!!!

[JED]

Unfortunately I can't see the pics but I'm sure I'm missing out!!

[Beekster]

The holidays have slowed everything down, but things have been happening. I am working on the underwing weapons pylons:

This is the first iteration, getting sanded to match the curvature of the wing. These have been discarded. I used the magazine reference for size, and these are too tall. That becomes apparent when you try to fit the minigun pods. So another, smaller batch is in process.

I have also been continuing to work on the nose and tail. Both need some sanding, and a little filling yet on the nose, but both are getting dialed in:










Note the change in shape at the nose. I had been trying to make the shape fit the kit locations for the pitot tubes and getting more unhappy with the contours. Things just didn't look like the pictures; the chin was more slab-sided than I was making it out to be. It finally dawned on me that the pitot tube locations were moved when this conversion was done; they sit a little higher on the fuselage side.

[JCON]

Coming together nicely now! Definitely taking shape!

[JEFF]

That looks really nice,Sir. Better and better every post.

[gator]

Just catching up. Excellent work sir.

[JED]

Great work Beekster

[Beekster]

Finally got the weapons pylons on the wing, now that I made them all shorter in height:




I got them evenly spaced, and at 90 degrees to the wing surface which looks to be how they were fitted. Is the spacing correct? No idea. Once again, TLAR covers the situation. They are too close together for all of them to be loaded with certain types of ordnance though 500lb Mk. 82s should fit everywhere. The few images I have don't show them all loaded at once anyway. Now to work on the ordnance stuff to hang off of some of these.

And now that I'm happy with the tail area, the horizontal stabilizers are on for good:





In addition to ordnance, I now have to dry-fit the wings and landing gear with tires on to do the final fitting of the belly radar pod. I hope that I don't need to sand it down much more for clearance.

[JCON]

That looks really good Beekster! Nice work sir!!!

[JED]

Great work