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Curtiss P-6D (conversion from Monogram 1/72 P-6E)

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The Curtiss P-6D served as the operational test bed for an early General Electric turbocharger. Fitting this in 1932 to a Conqueror 12 cylinder 'V' motor required some surgery on the cowlings of eight machines already in service and designated P-6A (which differed from the P-6 by using glycol coolant rather than water).  No more connection exists between the P-6/6A and the familiar P-6E, which began as the XP-22, than the basic structural components shared among all Curtiss Hawk biplane fighters. From the first P-1 to the last export Hawk III, the wing structure of the Hawk biplane did not change, with the exception of the disastrous 'metallized' wing of the BF2C. The basic girder form of the fuselage remained the same, however it might be fleshed out with stringers and formed panels. A variety of engines were fitted to Hawks, both 'vee' with various cooling arrangements, and air-cooled radials, all with ever increasing power, there were changes rung on the landing gear and other details here and there, but it was all the same design from first to last: Curtiss wrung every last bit of toothpaste out of the tube with the Hawk of the early twenties. So I'll be able to use wings and tail from the kit, and take some measures from it, but the rest will have to be done from scratch.




Here's a couple of pictures of a P-6:






The P-6A with its glycol cooled motor was a bit more closely cowled, and when piped for the turbocharger looked like this:






The port-side oddity is ducting for an oil cooler.


Usually I'll do the hardest bit first, there being little point to the rest if that can't be got right. I haven't done anything of this sort in a while, though, so I figure to start with simpler portions.




I'm using as scratch-sheet a sectioned drawing left from a long ago build, of an Export Hawk sold to the Dutch East Indies. This was a P-6 fitted with a water-cooled Conqueror using the radiator arrangements of a P-1, so back of the engine it's right enough for basic shape.


This initial segment extends from rudder-post to the front of the cockpit, with the 'step' corresponding to where the headrest is.


Sides were cut to measure from 30thou/0.75mm sheet, bent to match the bottom outlined on another piece of same. Excess trimmed down. Turtleback piece is a triangle of 80thou/2mm sheet, trimmed and sanded. Belly built up with layers of 30thou, stepped at each vertical section mark.




Here's the belly sanded to shape.




Here's the turtleback sanded to shape.






The sides of the fuselage have been extended to about where the rear cabane strut would sprout. This has been provided with a floor (which extends back into the cockpit), and braced with shims to keep it straight.


This is the area to which the lower wings will attach. The kit piece serves as a gauge. The gap between its root mating surfaces is 13mm, the width of the fuselage here is 11mm, which allows one millimeter to either side for fillets at the root included on the kit's fuselage halves.


After this fitting, I added belly to the extension. A front piece of proper curve went under the floor. The belly here is hollow, three bits of 30thou (the center one bent to a curve) skin it.




I'll get something up in front of the cockpit next, and then tackle the nose. I've decided I can take for accurate the Squadron/Signal drawings in their Army Hawks number, they resemble the photographs:





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Good to see you back with a very interesting project OM. I agree that making the most difficult parts first is a good policy, and you seem to have got over that hurdle so the project should be a success.


I for one will be following along with interest.



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Now for the tricky bit, gentlemen....


The nose.


I've usually done things like this by shaping thick laminates, but after so long a lapse I thought of trying something new (with much less dust), and have built a sort of framework, based on a profile piece in the center, that gets skinned section by section.




The center line is the thrust line, all others indicate where some 'shelf' or 'bulkhead' of the framework goes.




This is the upper decking skinned on the portside, still open to starboard. Two pieces of 0.75mm/30 thou sheet to each segment.




Here it is in profile, with full upper decking covered, and lower wing very roughly where it ought to go.




This is the upper portion of the nose skinned. At the very front is bits of doubled 2mm/80 thou sheet. That simply has to be sanded to shape. Below this is the radiator tunnel.




Here the front is shaped, and capped with a disc of 6mm. The portside segment left open is where the oil cooler ducting shows.




The sides of the tunnel are cut to match the profile, bent where things narrow and angle sharper up.




This is the two pieces taped together in profile. Width matched, but mating needed adjustment to get things like wing roots and cockpit and ducting in proper relation.




Here the pieces are mated. Radiator tunnel was trimmed at the rear, fuselage sides trimmed back a bit.




Here's the ducting on the port side. The front opening begins near the front of the shaped nose-pieces. The skinning was applied over the opening, not in it, there is a slight bulge in pictures.


With the basic shapes in hand, surface detail  is next, once I've sorted out the cockpit and upper decking behind the firewall.


This far into the project, I finally came on a decent looking drawing of a stock P-6A:




No idea its provenance, though someone may recognize the signature. The bit of slant before the cockpit shows in photographs.




This is an odd drawing long in circulation as a P-6, it has P-6D ducting (somewhat exaggerated) while being otherwise unexceptional. It being Curtiss, the wings and tail are fine....

Edited by Old Man
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  • 1 month later...

I have got back to this after finishing another project, a simultaneous build of a USS Ranger Wildcat and a Vichy Hawk 75 during Operation Torch (they're the last entries in the Revell/Monogram Classic GB Gallery).




The front decking before the cockpit is a layer of 2mm and of 1.5mm sheet, trimmed and shaped. A notch has been cut to accommodate the tail assembly, and stringer indications scraped in..


My intent was to do surface detail on the cowling, and I started by marking where the exhaust stacks and wing roots would be, so things would be in proper relation to these. I decided to scribe a marking line for the exhaust, Near the very front on the starboard side, things had got too thin and crumpled. I had at least got the lines at the same height (marked by tacked in rod).




I started trimming away the crumple to put in a patch, and realized I'd do better to just remove the whole 'section'. I could build up to the slot with squared rod, and the lengths of rod representing the pipes could attach to the 'spine' of the cowling. So I did that on both sides.



 The twelve exhausts go into a length of 13mm. The front two have to do in a notch and hoe arrangement into the front plate. The projections on the starboard side remain from sighting in to see the slots were the same length and at the same height on the cowling. I used 0.9mm round rod.




Here both runs are in, and trimmed level (they will be shorter, though).


I decided I had a technique, and when I marked wing-root position, went ahead and pierced through deliberately.




It opened between the cockpit floor and the structural bottom of the fuselage.




Here's the wing roots into the slots for positioning.


Once I squared the slots, I found to hand a strip of 2mm sheet just the right width...




It passes clear through, and will provide material for the dillets at the wing root.




This is where I'vee stopped for now. The pass-through is fastened and trimmed down: it projects 2mm from the fuselage sides. Rear cockpit decking is permanent, the sides are just roughed in at present, enough to show I can slip in the plot later.



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There's actually a bit less here than meets the eye....


I had intended to do cowling detail, but figured I should nail down cabane locations first. I tacked together the fuselage and lower wing of another kit, using it as a jig to attach the interplane struts to the upper wing (painted and decaled first). I put the lower wings to the fuselage with a couple of easily breakable dots of CA gel.




I did not expect to find at this stage the struts fit squarely in the locating holes. However they did. So I went ahead and made the wing root attachment permanent. I sawed the cabanes off the donor kit's fuselage, and tacked the whole thing together for the moment with white glue.




The cabanes meet the fuselage where they should, by measure from the stern-post, and relative to the exhaust stacks. I'll take it apart to finally do surface detail on the fuselage. That will be a little trickier with the lower wings on, but serendipitous fit is worth it.



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16 hours ago, pheonix said:

That was lucky! I wish some of my scratch builds would fit as easily and as well as that! Looks very good at the moment, and will undoubtedly look even better when the fuselage details are finished.




I claim no credit, sheer good fortune. It's a new wrinkle to incorporate so many major kit parts. Kind of like an old 'Body Shop' conversion fuselage.

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Here's how things stand after the weekend:








Most of what I did was improvised, and in increments, so not conducive to pictures.


Once the mouth of the radiator tunnel was put in, I re-built the rest of it in sturdier plastic. The angle is better, and the rear matched to the 'slots' accommodating the main land-gear struts.


The cockpit opening is properly dressed, the headrest in place.


My 'stub' method for fillets did not pan out, I built some up with 1mm x 0.5mm strip (uppers only).


The tail is only temporarily on, as an aid to alignment. The P-6E had smaller elevators than the earlier Hawks, with straight trailing edges. I have extended the kit piece to the proper trailing edge 'wedge'. The balance area of the rudder on the P-6E was smaller than the earlier Hawks, and the kit piece is re-scribed accordingly.


I don't know what the tear-drop thing on the starboard side is, but it was there....





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Have the manifold on....




I had ideas of bending one way or another the exhaust stubs, but that was not feasible. I shaved them down even, leaving circles that serve for putting in new bits at proper angles.




Here is the port side manifold. Here the stubs go straight up, more or less. The pipe starts small, and increases in diameter going forward. It began as 1.25mm round rod, glued to the leveled stubs and shaped on the model.




The two sides are not symmetrical. On the starboard side, the pipe is larger, and stubs go out as well as up/ The vertical bit will be trimmed: it feeds direct to the supercharger. The starboard and wrap-around portions of the manifold began as 1.5mm round rod.






The raised circles and rectangles represent access panels with reinforced edges, the squared ones laced down as well. They were 0.5mm sheet or strip, sanded down considerably after application.


In service, a sort of windscreen for the exposed supercharger was employed, which will be placed after the supercharger is on.





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  • 4 weeks later...

This will not meet the deadline, Gentlemen.


Great regrets.


Couldn't get in a lick at the bench over the holidays, we've a cluster of birthdays then too. I'm not going to try and press a deadline on this.


I'll put up a condensed WIP thread upstairs in a bit. It's been, and remains, an exceedingly fun project.


Thanks for the interest and support.



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Sorry to learn you'll not be completing this one even with the extended deadline James but I'm much happier to see you'd rather finish it right than rush it.

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