Scratch Building a 1/72 scale 
Convair Model 48 Charger II

Convair Model 48 Charger COIN Prototype (Google)

The Model 48 Charger was the Convair Aircraft Corporation's contestant in the Tri-Service COIN (COunter INsurgency) aircraft Request For Proposals issued in October of 1963. Convair had actually built the Model 48 prototype with corporate funds in response to an earlier US Navy RFP for a LARA (Light Armed Reconaissance Aircraft) for the US Marines, and although North American had won the Tri-Service (USN, USAF, and USMC) contract with their OV-10A Bronco design, Convair was given the opportunity to compete the already-flying Charger against the still-on-paper Bronco. The unfortunate crash of the single assembled prototype of the Model 48, plus the departure of Convair from the aircraft business, put an end to the Charger's future.

Modified Convair Model 48 Charger I with potential weapons and fuel tanks (Google)

Forty years ago, in high school, I built a Hasegawa OV-10A kit. I loved the retro, throwback layout of this very sharp-edged, angular, non-sleek, prop-driven aircraft. However, I was so timid about attempting to (successfully) install, mask and paint the four-piece canopy, that I actually painted and decaled the model without any canopy at all. Lame.

Many years later, I built the Hasegawa kit again, this time with much better success. If you wish to, you can see the results by clicking HERE  

While researching that second Hasegawa Bronco kit, in the library of the National Air and Space Museum, I came across information about the other contestants in the Tri-Service COIN competition, including pictures of the Model 48 Charger. I was immediately very taken by the even more outlandish-looking Charger, and wanted to build a model of it, but at that time I had never attempted any sort of completely scratch-built model, even a relatively simple, slab-sided AFV, let alone an aircraft with the usual compound curves and such a unique transparent canopy.
 

Artist's rendering of the Convair Model 48 Charger (Google)

A few years ago, I spotted and promptly purchased a copy of the Ginter Naval Fighters series booklet Number Thirty-Nine, on the Charger. Now I finally had three-view drawings, details and photos from which to scratch build the aircraft, but the exaggerated, banana-like canopy was still beyond my abilities to create. No existing plastic model kit that I knew of could supply me with the Charger's very distinctive canopy. Years ago, I struggled with trying to make my own heat-and-smash clear plastic canopies, with a singular, unrelenting lack of success. I saw no reason to pummel that particular deceased equine any further.

On the internet, I discovered that a kit of the Charger prototype had been in very limited production in 2008, by a Czech Republic company called MIKU Models, but I could not find one available for purchase, at least for now. 

 

The Charger II

Convair model of the proposed Charger II design (Ginter Books)
Promotional model of Convair's proposed Gharger II (Google)

Recently, as I studied the Ginter booklet, I realized that Convair had developed (on paper) an improved Model 48, called the Charger II. Changes in the shape and size of the fuselage led to changes in the corresponding shape and size of the canopy. I realized this different canopy might be something I could find in an existing kit, or several canopies from different kits could be cobbled together to simulate that of the Charger II.

I searched through my collection of kits for suitable sacrificial canopies (kits I wouldn't build anyway), culled out a few likely candidates, and compared these clear pieces to the 1/72 drawing of the Charger II in the Ginter book. I became reasonably convinced that I could assemble a good enough approximation of the canopy, and began to think about how I would solve the other construction problems to scratch build a Charger II. Scratch building a few AFVs and missiles had taught me the skills needed to attempt a scratch built aircraft. True, it wouldn't be the extra-quirky Charger prototype, but close enough.

This page of the website will record my efforts with this project, successful or not. Welcome to the Big Gamble...

Three view drawing as basis for scratch built Charger II. (Ginter Books)

The Charger II begins: the fuselage

Cockpit sides and floor, with front landing gear bay, ejection seats, nose and tail cones, landing gear components

Here are many of the first parts assembled from existing kits or scratchbuilt for the Charger II. The front nose cone is from the nose of an Italeri B-57 (RAF Canberra). Fishing weights were stuffed inside the nose cone, before I blanked it off with Evergreen sheet styrene.The tail cone is the nose from a Monogram F7F Tigercat

The landing gear struts are from a Fujimi OA-4M Skyhawk two-seat trainer, which will also provide most of the canopy, as well as a lot of the front portions of the engines, I hope. The control stick and wheels are from my forty-year collection of spare parts.

The ejection seats are Squadron Shop resin True Details seats for the A-4 Skyhawk, which is what Convair selected when they built the Charger prototype. The instrument panels are from my AutoCAD supply of generic instrument panels.

The cockpit floor, which is the ceiling of the front landing gear bay, and the front and rear bulkheads are made from Evergreen 30-thou (30 thousands of one inch) thick sheet plastic. The half tube for the nose wheel is a section of Evergreen plasic tubing. The cockpit sides are 10-thou plastic sheet. 

Evergreen strips on sides of cockpit will receive instrument panels

When I have idle moments at work, waiting for an architectural drawing to finish plotting, for example, I'll pass a few minutes thinking about how to accomplish some step of a model project. To preserve my thoughts, sometimes I'll make a sketch of my ideas, because at 60 years of age, if I don't make some record of my ideas, they'll slip away into the aether, never to return. Below is one of several sketches I made to puzzle out how to build the Charger II.

Scan of sketch of fuselage floor ideas

Here is how I visualized using quarter round Evergreen strips to create a consistent radiused edge along the fuselage.

After I airbrushed Humbrol No. 147 at the cockpit and wheel well, I glued the left side of the cockpit to the rest. I'll install the instrument panels later, and after that the ejection seats. I glued the cockpit/wheel well assembly to a 40-thou Evergreen plastic sheet floor for the fuselage. At the edges of the floor are Evergreen 80-thou quarter round strips, to form the rounded corners of the rectangular fuselage.

While I waited for parts of the fuselage to dry, I started work on other parts of the Charger II. To create a starting point for the large, "flying tail" horizontal stabilizer, I cut straight and plumb ends through the airfoils of two Academy OV-10A stabilizers and glued them together. Later, I'll cut down this piece to the correct length and depth to match the drawing for the Charger II.

I also started to modify the landing gear parts from the Fujimi OA-4M Skyhawk to fit the Charger II.

Assembled cockpit painted Humbrol 147, front landing gear yoke assembled, two Academy OV-10A horizontal stabilizers butt-joined to form a blank for Charger II flying tail.

Sidebar: the flying tail
 

Front landing gear bay detailed and painted Humbrol 147; cockpit/wheel well glued to floor of fuselage, with quarter round strip at edges; front landing gear yoke fabricated.

While some fuselage work was drying (see below), I worked on the unusually large, pitchable horizontal stabilizer, called a "flying tail". Working with the scale drawing, I cut, trimmed, shaped and polished the Academy OV-10A horizontal stabilizers blank to become the Charger flying tail. 

Stabilizer blank trimmed down to size and shaped according to drawing
Stabilizer compared to drawing
Scan of sketch of fuselage sides with quarter round Evergreen strip at top of fuselage

To avoid doing some assembly of parts that will make it difficult or impossible to do some future installation later, often I'll write out a sequence of steps, thinking through on paper before I start gluing and painting. When I don't remember to do this, it can cause me a lot of trouble. For example, recently I attached and filleted-in with epoxy the canopy of a Revell World War II A-26B Invader, BEFORE I installed the pilot's gunsight. After much profanity and remonstration at my senility, I gingerly pried the canopy off and installed the gunsight, then re-installed and re-filleted the canopy back on to the fuselage. Success in the end, but who needs the grief?

The fuselage continues...

Evergreen 80-thou quarter round plastic strips glued to top edge of 80-thou sheet fuselage sides. Nose cone glued to cockpit, with more metal nose ballast added.

I used sticky-back copier film applied to 80-thou Evergreen sheet to cut out the fuselage sides. I taped the sides down to a piece of heavy cardboard, and then taped down the 40-thou Evergreen quarter round strips in place against the top edges of the fuselage sides. Then, I applied Testor's liquid glue with a fine brush to the join between the sheet and quarter round. Once the glue was applied, I added more tape to force the parts together tightly, while the glue dried.

Fuselage sides installed, tail cone installed, turtlebacks installed at front and rear of cockpit

I read once that Otto von Bismarck said something approximating "Doing politics is like making sausage; you don't want to watch it happening." I don't know how others scratchbuild models, but for me, scratchbuilding is often how I imagine it looks to make sausage: not a pretty picture. Delicate detail scratchbuilding is pretty precise, of course, but scratchbuilding major components, like this fuselage, is going to be rough and crude, at least up to a certain point. You can see how I had to add shims of Evergreen sheet plastic to undo where I sanded too much of the Italeri B-57 nose, before I glued the nose halves together. I'm sure there will be plenty more shim-work, before I'm done.

Top view of fuselage assembly

The next step will be to add material to make the transition from the rectangular fuselage shape to the oval cross sections of the nose and tail cones. I will experiment with MilliPut, the UK-produced epoxy putty originally invented to repair porcelain china and terra cotta pots. Long ago modelers discovered how useful MilliPut is for shaping anything for a model. I have used it a few times to sculpt a simulation of the canvas dust shroud between the mantlet and the gun tube of an AFV.

Time for MilliPut

MilliPut canvas shroud at turret and gun tube of a scratch built M-55 8" Self-Propelled Howitzer
Scan of sketch predicting where MilliPut will be needed on fuselage at nose

We'll see if my sketch has any bearing on reality, after I apply and sand the MilliPut epoxy.

Fuselage with MilliPut epoxy putty applied
MilliPut at tail
MilliPut at nose wheel bay

Of the two unopened boxes of MilliPut epoxy putty I had on hand, one had cured unmixed in the box. The other box was just pliable enough to mix by kneading into a useable lump. MillPut has the amazing property of being soluable in water, while it is still soft. Once it cures, it is completely waterproof. 

This step isn't quite as sausage-making-ugly as I had predicted, mostly because I could smooth out and feather the Milliput with lots on water. Once it has cured, overnight, I'll start to sand the MillPut, blending the contours of the fuselage from rectangular to oval and on to round at the nose and tail cones. I think it's going to be interesting.

Scan of sketch visualizing cross sections through the nose of the Charger II
Front cockpit instrument coaming replaced to better fit canopy. MilliPut at nose and tail sanded to blend in with fuselage
Too much plastic at turtle deck whittled down at top rear of fuselage
MilliPut blended in with front wheel well and nose

Cobbling together a canopy:

Once I had started the fuselage, I began to puzzle through how to create the most challenging part of the project: the transparent canopy for the crew compartment. I needed enough of the fuselage to be finished to have something against which to compare the possible canopy pieces I had collected. At this point I had enough.

I knew I had to carefully cut and trim the different canopy pieces from different kits to make up one continuous canopy for the Charger II. I also knew I had to use the locations of the opaque, painted framing members of the Charger II canopy to conceal the unavoidable joints between the clear pieces I was cobbling together. The assembly, which upon reflection I dubbed "FrankenCanopy", looks like this:

FrankenCanopy assembled from ACADEMY F-89 Scorpian windscreen, FUJIMI OA-4M Skyhawk main canopy, and ACADEMY Hawker Typhoon rear canopy
Rear view of FrankenCanopy. Note scribed canopy framing for OA-4M Skyhawk to be sanded away.

Comparison of FrankenCanopy on the fuselage with the drawing of the Charger II showed that I was headed in the right direction. After sanding away the bottom edges of FrankenCanopy as required to come close to fitting the fuselage, I also cut away my first attempts at the front instrument coaming and the turtledeck at the top of the rear fuselage.

Trim a little on the canopy, test fit, trim a little on the fuselage, test fit. Repeat. Repeat. Repeat.

Test fit of FrankenCanopy to fuselage
Rear view of test fit of FrankenCanopy on fuselage
Front view of test fit of FrankenCanopy on fuselage. Care will be needed to install the canopy straight, plumb and true.

Shaping, smoothing and polishing the canopy

Once the fit between FrankenCanopy and the fuselage was close enough that the remaining gaps could be filled with tiny strips of Evergreen plastic plus two-part epoxy, I began the really risky phase of gently sanding away the seams and scribed detail on FrankenCanopy. The trick is to work so slowly and gently with the Squadron Shop Premium Tri-Grit three grade sanding/polishing stick that I don't cause tiny stress fractures to appear in the brittle clear plastic. Fortunately, it appears I was successful: after polishing FrankenCanopy with Work Site brand liquid Plastic Cleaner and Polisher, examining FrankenCanopy in strong light revealed no tiny cracks. Even so, during the polishing phase, I managed to separate the windscreen from the rest of FrankenCanopy. Some very, very careful regluing ensued. 

Joints and scribed framing on FrankenCanopy sanded smooth.
Rear view of sanded FrankenCanopy
Polished FrankenCanopy
Rear view of polished FrankenCanopy
Fresh MilliPut applied to fit around the windscreen
Fresh MilliPut applied to fit around the windscreen.

Cutting away the unsuccessful first attempt at the front cockpit instrument coaming required adding more Milliput to fill the resulting gaps. Once in place, I gently pressed the canopy windscreen into the soft Milliput to create an appropriate fit. Once the MilliPut cures, I'll sand away the excess to blend with the windscreen.

MilliPut sanded smooth at windscreen
Note addition of gizmology inside cockpit

Starting the engines/tail booms
 

Photo of intake under construction for prototype Convair Charger aircraft

The Charger II has intakes above the propeller shaft housings to bring combustion air into the engines (see image above). To scratchbuild these intakes, I assembled Evergreen and Plastruct styrene shapes into an 'extrusion" that I could then sand, file, trim and cut into two intakes. These will be glued on and blended into the engine/boom assemblies. To make the extrusion, I selected two different diameter Evergreen tubes. I cut the smaller tube into a long section like a trough. To create an inside radius where the two tube sections meet, I glued lengths of triangular Plastruct styrene to form a fillet.

Scan of a sketch illustrating ideas for shaping the intake and engine/boom assembly
(Left to right) Evergreen plastic tube, tube sectioned, triangular strip, larger tube with triangular strips attached
Assembly of Evergreen pieces to create an "extrusion" to make air intakes

To make the engine/boom assemblies, I selected an Evergreen square tube of the correct dimension for the width of the engine/boom, and I glued together the front half of the Fujimi OA-4M long range fuel tanks to become the propeller shaft housings.

Fuel tanks to become propeller shaft housings, Evergreen square tube to become tail boom/wheel well
(Left to right) Fuel tank reshaped as propeller shaft housing with aluminum tube as propeller bearing. Hasegawa OV-10A propeller. Evergreen square tube with wheel well cut out.

After cutting out the opening for the main landing gear bay, I added Evergreen quarter round strips to the edges of the square tube, and filled in between the quarter round strips with matching thickness Evergreen flat strip, to make the bottom of the engine/boom assembly have the appropriate radiused corner edges. In the image below, you can also see the intake extrusion shaped to form the rounded crescent air intake.

Evergreen extrusion shaped as air intake. Evergreen quarter round and flat strip on bottom of tail boom around wheel well.

Two steps forward, one step back

When I compared the first attempt at an engine housing/tail boom to the three view drawings, I decided I had settled for a width of stock Evergreen square tube which was actually just a little too small. Regrettable, but I could fix this by gluing 10 thou Evergreen sheet on both sides of more of the same square tube, achieving a much better width. I made two new landing gear well units (the extra width was good here, too) and attached the engine housings made from the Fujimi  OA-4M fuel tanks to the fronts. So far, so good.

From left to right: first attempt at engine housing/boom. Middle and right engine housing/booms made slightly wider.
Two new engine/boom assemblies to replace too-thin engine/boom assembly

Something is not right...

Note the shape of the underside of the engine boom and the size of the oil cooler intake on the underside of the engine housing
Assembly sanded and smoothed, with oil cooler intake added.
Slightly different view of assembly

Unfortunately, after I sanded and smoothed one of the two assemblies, and added the oil cooler intake, it just didn't look right. The circular cross section of the engine housing extended too far back, and the oil cooler looked too small. Although the picture (above) of the Convair Charger II model obviously differed from the three-view drawing that is my only source of information for this never-built, "paper" airplane, the picture told me that the underside of the engine/boom assembly needed to be more rectangular farther toward the front of the unit. Cue the MilliPut: sausage-making time. 

MilliPut added to engine boom assemblies to correct shape of units

I sliced the oil cooler intake off of the one boom assembly (oh, the pain, the pain...) and added Milliput to both assemblies, particularly on the assembly from which I had removed plastic. The job here is to be sure there is sufficient MilliPut on the assemblies so that when I sand off the excess to the correct contours, there are no bald spots needing more MilliPut. We'll see if I succeeded, in several hours, after the MilliPut has cured.

Bottom view of reworked engine housings.
MilliPut sanded smooth to correct shape of engine housings.

That looks better. Next come new oil cooler intakes.

Evergreen square plastic tube as handles to hold while shaping sheet and strip assemblies for oil cooler intakes

Similar to the "extrusion" I made for the air intakes, and referencing the three view drawings of the Charger III assembled a group of Evergreen plastic shapes to form the basis for the oil cooler intakes. I included a length of square plastic tube as part of the assembly, to establish the correct width of the assemblies, and to act as a convenient handle while I whittled, filed, sanded and polished the bottoms of the oil cooler intakes. Once the intakes are formed, I will carefully cut the intakes off of the handles, and then shape the tops of the intakes to fit against the undersides of the engine housings. That's the plan, anyway. We'll see.

Evergreen plastic assemblies sanded to resemble oil cooler intakes.

Once the oil cooler intakes were shaped on the square tube handles, I cut them off with a fine tooth razor saw, and began the tedious process of shaping the concave surface on the top of the cooler as required to fit as accurately as possible to the underside of the engine housing. Much test fitting and trimming was necessary. When the gap at the joint between each cooler and each engine was within about ten thou (.010"), I could rely on cyanoacrylate (super glue) to fill the gap. I barely attached the coolers to the engines with tiny dabs of slow-curing cyanoacrylate, so that for two or three seconds, I could adjust the position of the coolers. When each cooler was tacked on to each engine in matching locations, I applied instant cyanoacrylate to the joints, in several sparing layers, to close the gap and fillet the joint. After careful sanding with 400 and 600 grit wet-or-dry sandpaper, the gaps were filled, and the coolers were blended with the engines.

Oil cooler intakes installed on engine housings.

The Engine/Tail Booms continue...

Stickyback film to shape pieces for the tail booms

After the front half of the engine/tail boom assemblies finally seemed to be satisfactory, I started building the rear half of the tail boom. Using a Xerox copy of the three-view drawing, made with transparent Sticky-Back film, I applied the piece of the Sticky-Back with the side view of the tail boom to 20 thou Evergreen sheet styrene. This gave me a scale pattern from which to cut out the side piece of the tail boom. Once I had the first side piece cut out, I used it as a template to cut out the remaining three identical pieces. I attached two pieces to the rear of one of the wheel well boxes, added a spacer at the extreme rear to get the correct width, added quarter round pieces to the bottom edges, and then added a triangular "floor" to the bottom. Once the cyanoacrylate had set up, I sanded all of the joints flush. 
 

Tailboom sides and bottom installed on one engine assembly. Ribbed panel scratched from sheet and strip to dress up interiors of wheel wells.

At some point I realized I had been building only one engine/tail boom assembly at a time, instead of both assemblies simultaneously. I guess that since I was making this up as I went along, I was subconsciously anticipating I might need to make corrections; an accurate assumption, as you have seen. I had to redo the first attempt at the engine housing/wheel wells, then I had to redo the first attempt at the engine housing/oil cooler intakes. I finished installing one tail boom to the rear of one of the wheel wells, before I began installing the other, to avoid having to redo both of them, if something didn't look right. I had not consciously or intentionally planned to follow this cautious one-two-step process, but my subliminal instincts obviously kicked in and guided my decisions on how to proceed.

As I was making the first tail boom, I also made up a scratch-built ribbed panel by gluing 10 thou by 15 thou Evergreen strips equally spaced on a piece of 10 thou sheet styrene. This gave me a supply of ribbed material from which to cut pieces for the inner sides and the ceilings of the wheel wells, to simulate the formers under the exterior skin, as seen when you looked into the wells. I delayed adding this detail until I was reasonably sure the wheel wells were done. More subliminal efficiency, perhaps.

Starting the wings

While waiting for the MilliPut on the engine assemblies to cure, I started the wings for the Charger II. The Academy OV-10A kit that so far has supplied the propellers and the flying tail for this project has cheerfully offered to sacrifice its wings, too. Most agreeable. 

Knowing that at some point I will be trying to butt join the left and right wings to the fuselage, I've been thinking about how to try to ensure that these three assemblies end up plumb, true and level with each other. I recalled how, thirty years ago, my father's radio-controlled, six-foot wing-span glider had detachable wings that were mounted to the fuselage by sturdy metal tubes, passing through the fuselage, providing perfect alignment. I thought I would adapt that design concept to the Charger II.

The image below shows how I used Evergreen plastic strips to align K&S aluminum tubes to be perfectly parallel with the Academy wing parts. I will bob the wing tips of the Academy wing to match the three-view drawing, and then I will cut the wing into two pieces, one for each side of the fuselage. Eventually, I will drill holes through the fuselage to correspond to the aluminum tubes inside the wings. That will be a tricky step; I may need to build a jig to hold the fuselage to get the holes plumb, true and level. Then, I should be able to skewer the wings on two brass tubes that project through both sides of the fuselage. If the fit of the brass tubes inside the aluminum tubes is tight enough, I should achieve plumb, true and level. We'll see.

 

Academy OV-10A wing top and bottom halves with aluminum tubes installed in top half
Top side of Academy OV-10A wing with tubes inside as blank from which to shape Charger wings
Underside of Academy OV-10A wing
Academy wing dry fit to scratchbuilt engine/tailboom assemblies.

I'm leaving the Academy wing intact while I fit the engine/tailbooms to the underside of the wing. Leaving the wing intact provides a constant datum line for me to align the two booms properly with each other. 

I'll need to install the curved turtle backs to the tail booms, before I permanently attach the booms to the wing. I haven't finished puzzling out exactly how to make the turtle backs. Some combination of Evergreen plastic and MilliPut, probably, but I need to keep the weight down, behind the center of gravity of the finished model, so the model will rest on all three wheels. That's why I wedged fishing weights everywhere I could inside the nose, as far forward as possible.

Underside view of the dry fit of the engine/tail booms to the Academy wing

Fitting the booms to the wing involved some sausage making. I cut too far into the underside of the wing, which required some gluing and filling, and getting the booms at right angles to the wing involved some shims, but it seems to be working out.

Once I think I've made all of the adjustments to this installation, I'll cut off the excess wing at each wingtip and plug up the exposed openings. Once that step is complete, I'll cut the single wing into two pieces. Then I'll permanently attach each boom to each wing, attach the air intakes to the tops of each engine housing, and fill in all of the gaps, probably with MilliPut. That's the plan, anyway. Stay tuned.

Sketch after the fact of assembling the turtleback on the engine/tail boom assemblies.

This is an instance where I drew a sketch of how I built part of the model, AFTER I built that part of the model. I started shaping plastic pieces for the turtlebacks of the tail booms, based on ideas I had thought of while doing other tasks. By the time I finished shaping and gluing plastic pieces, the turtlebacks were done. I didn't stop to photograph the process along the way, either, so to have a record of what I did, I made the sketch above. Sort of like shooting arrows at a wall, and then drawing bullseyes around the arrows.

Note that in the pictures below, the wing tips have been bobbed and the resulting cavities plugged with Evergreen styrene and superglue.

Evergreen plastic and superglue at turtlebacks installed on tailbooms, shaped to fit top of wing.
Front view of engine/tailboom assemblies with turtlebacks installed, blending into top of wing (somewhat).

Cutting and fitting the wings

Academy wing cut into halves. Note aluminum tubes inside. Center section will be discarded.
Brass tubes installed through sides of fuselage to fit inside aluminum tubes in wings.
Wings fitted to fuselage.
Dry fit version 1.0 of wings, fuselage, canopy, engine/tail booms and props.

It's starting to look like an airplane...

Closing up the cockpit

Before I can start assembling together the wings, engine/tail booms and fuselage, I need to finish out the cockpit and install the canopy. Installed and faired in with two-part epoxy, the canopy will seal off the cockpit from dust, moisture and damage while I attach and blend in other components (like the wings to the fuselage). 

I painted the Squadron "Tru-Details" A-4 Skyhawk ejection seats according to the color picture of a real Escapac ejection seat in a Squadron "Walk-Around" book on the Skyhawk. I masked off the instrument coamings and rear deck and airbrushed these areas Humbrol No.67 Panzer Grey, to provide a scale black. I installed the film instrument panels and side consoles, then installed the completed ejection seats. I added pre-finished Eduard photo-etched ejection pull handles to the tops of the ejection seats. I then masked the exterior of the fuselage, leaving all of the cockpit area exposed, so I could airbrush first Johnson's "Future Premium Floor Care" clear acrylic (to deepen the shades of paint and drybrushing), and then Testor's ModelMaster Clear Flat Lacquer. Here are the results. 

All details installed in cockpit, painted and finished with clear flat lacquer
Finished cockpit, ready for canopy to be installed
Finished cockpit (note to self: don't forget the reflector gun sight, this time).

Below is the fuselage with the canopy installed. Before installing the canopy, I applied a coat of Johnson's "Future Premium Floor Care Finish" to the interior of the canopy, to maximize the sheen on the inside, as well as smooth out and obscure any small scratches. The "Future" also protected the surface of the clear plastic from any fumes from the plastic glue that came next, fumes that could fog up the clear styrene.

The canopy was tacked to the fuselage with very sparing applications of Testor's Liquid Plastic Cement, using a small but old paint brush. Once the glue had dried, the first application of 30 minute, two-part epoxy was added, also very sparingly, to close the gaps between the canopy and the fuselage. Using 91% denatured alcohol (which perfectly removes the uncured epoxy), this gap filler was smoothed away very carefully, with minimal pressure, to avoid causing the epoxy to ooze into the cockpit, where it can be seen through the canopy. 

Once this first fillet of epoxy cured (four to six hours), I applied a second dose of epoxy, again swabbing the excess away with another alcohol-soaked piece of lint-free polishing fabric (disposable diaper absorbent filler), to leave a radius between the edges of the canopy and the top of the fuselage. Since the gap between canopy and fuselage had been completely sealed by the first layer of epoxy, I could apply more pressure with the alcohol swab, to get a smooth fillet.

Once the canopy was solidly glued and filleted to the fuselage, I lightly sanded the epoxy fillet and fuselage, and then polished the entire canopy with Novus Plastic Polish. I could now apply a little more pressure to the fragile clear styrene at this point, because the canopy was securely anchored to the fuselage, and no longer as easily susceptable to flexing and tiny stress fractures.

Fuselage (including reflector gun sight installed inside cockpit) with canopy attached, filleted with epoxy, and polished.
Canopy installed and filleted in with epoxy. Canopy, fillet and fuselage sanded and polished. Brass tubes at wing roots installed.

Starting the vertical stabilizers

After installing the canopy, while the first application of the two-part epoxy fillet was curing, I started the vertical stabilizer: the fin and rudder. I used the vertical tail from the ever-obliging Academy OV-10A as the source, since it already had an airfoil shape. The first step was to sand off all surface detail from both sides of the Academy part, and plug the slot for the horizontal stabilizer with Evergreen strip styrene.

Using a Sticky-Back film copy of the fin/rudder from the three-view drawing, I scored all of the edges (and the joint between the fin and rudder) through the translucent, self-adhesive film. Removing the film, I followed the score lines to cut out the corresponding shape. Using the score line for the joint between fin and rudder, I deeply scribed this hinge line with a dental tool adapted to score plastic. Using a lighter touch, I scribed the trim tab at the trailing edge of the rudder, and using an even lighter touch, I scribed a couple of panel lines, all of this on both sides of the vertical tail. 

 

Sticky-Back film with Xerox of Charger II rudder drawing applied to Academy OV-10A rudder
Academy OV-10A vertical tail trimmed to match Charger II drawing

A lot of careful trimming and test fitting was needed to fit the fin/rudder to the top of the tail boom. Once that was done, I fashioned a ventral fin/runway skid from Evergreen plastic that matched the thickness of the bottom of the rudder. I will leave these first pieces loose as patterns for the matching second pieces. Once all vertical stabilizer parts are finished, I will glue them to the tail boom pieces.

Scratchbuilt engine/tail boom assembly (upper) with fin and rudder shaped from Academy OV-10A fin and rudder (lower)

Below are the two engine/tail booms with the vertical stabilizers installed. Test fitting the wings to the fuselage and the engine/ tail booms to the wings confirmed that there is more play (loose fit) than I would like between the brass tubes through the fuselage and the aluminum tubes in the wings; too much wobble to get the wings properly aligned. I will have to puzzle out how to get a good, tight fit that aligns both wings accurately: plumb, level and true.

Vertical stabilizers, fashioned from Academy OV-10A tails, installed on tail booms.
Dry fit version 2.0: vertical stabilizers attached and horizontal stabilizer resting on top of fins/rudders.

After careful thought about the pros and cons, I decided to glue the wings to the fuselage, first, and THEN attach the booms to the wings. I reasoned that getting the wings glued on straight would be easier without the booms blocking my view. Then, getting the booms glued to the wings parallel to each other should be pretty straight forward.

To deal with the wing wobble, I very carefully deformed the brass tubes through the fuselage by pinching them with a very small pair of needle nosed pliers. Deforming the brass tube made it slightly larger in one dimension, causing a tight friction fit inside the aluminum tubes inside the wings. Wobble eliminated!

Dry Fit version 3.0: wings attached, engine/tail booms (with fillets at vertical stabilizer) dry fit, plus horizontal stabilizer by gravity.

Where is this all headed?

It seems like the build is going reasonably well. Hopefully, in a month or two, I'll be ready to start masking, painting, and decaling this model of the Charger II. The question is, as what shall I decal and paint the model to be? Where is this all headed?

Let me revisit the facts: this is a model of an airplane that never existed. Convair built one Model 48 Charger, and had the parts to build a second Charger, but the Charger II existed only on paper. My only references are one set of three-view drawings and photos of two or three of the manufacturer's models, built for promotion and public relations purposes. And there is a fair amount of variation between the drawings and the models. I'm trying to build this model as close to the drawing as possible, but I've had to make many small accommodations, along the way.

The truth is, I'm free to paint and decal this model any way I wish, since it never saw the light of day. However, I will enjoy the finished model more, I think, if I make it resemble the real airplane it might have been. I've thought about that a lot, and I haven't decided anything, yet, but I am leaning in a couple of directions.


At this point, I'm pretty sure I will paint and decal the model as a machine belonging to the United States Marine Corps. That gives me the option of a USMC airplane from the 1960s (Viet Nam war) to perhaps the 1990s (Operation Desert Storm), which is when the North American/Rockwell OV-10A Bronco (the airplane the Marines deployed instead of the Charger) was evidently last used in combat. Appropriate paint schemes include USMC Green, USMC Green with White undersides, United States Navy Low-Viz Grey schemes from the 1980s, and potentially a Desert Storm Brown and Sand camouflage. I will need to do some research.

 

Viet Nam war OV-10A in USMC camouflage (Squadron/Signal Books "OV-10 In Action")

Decals are available for 1/72 USMC OV-10A Broncos, and I could reasonably assume similar markings might have been applied to the Charger II, if it had been deployed. I have a few sets of SuperScale decals for such USMC aircraft. I'll have to research that, as well.

Lastly, I can consider some options for arming the Charger II with guns, missiles and bombs. The Ginter book on the Charger illustrates concepts for arming the airplane, concepts that I could adapt and even extrapolate upon on my imaginary Charger II. However, I'm inclined not to hang any ordinance on this model, to maintain the uncluttered, quirky lines of the design. We'll see about that, too. Food for thought.

Desert Storm OV-10D in USMC brown-tan camouflage (Squadron/Signal Books "OV-10 In Action")

Landing gear struts, wheels and doors

Landing gear struts, wheels and doors: front wheel, strut and door at bottom, main wheel struts and doors above.

I decided to start to fabricate the main landing gear struts and main wheel well doors while the engine/tail booms are loose from the wings. This made it easier to make, trim and fit parts in and around the wheel wells.

I studied the photos and drawings for the Prototype Charger, and extrapolated what the Charger II main wheel struts and wheel well doors might have looked like, if the aircraft had been built. For the two main gear struts, instead of using the Fujimi OA-4M parts, I modified the main wheel struts from a Heller SAAB J-37 Viggen, added axles with brakes attached from a Heller T-28 Trojan, and scratch built the anti-caster oleos from Evergreen sheet and rod styrene plastic. The Evergreen white styrene trapazoids locate the main gear struts inside the wheel wells at a proper relationship with the aircraft and the ground it will be sitting upon. I hope. 

The landing gear doors were also scratch built from Evergreen styrene. Note the suggestion of hinge arms on the doors, which will give me something definite with which to glue the doors to the insides of the wheel wells. Long experience has taught me that trying to glue the edge of a wheel well door to the edge of a wheel well without some sort of positive, mechanical connector is a doomed proposition: the door might not align properly with the opening, might not be at the correct angle in any of all three axis, and is usually a very fragile join, easily dislodged by clumsy fingers. By adding hinges with flanges, you have a better chance of achieving a glue join that is plumb, true and level, plus strong. Stronger, anyway.

Attaching the tail booms to the wings 

I believed I had done all of the work that should be done while the tail boom/engines assemblies were unattached, so it was time to install the tail booms to the wings. This had to be done carefully, to ensure that the tail booms are perpendicular to the wings, in plan and in front elevation, as well as parallel to each other. I tacked the booms into position with small amounts of Testor's liquid plastic cement, adjusting the alignment of the tail booms as needed while the plastic cement was still soft and workable. Once the alignment was as good as I could make it, I filled the wing-to-boom joints with cyanoacrylate glue, to make the bonds permanent.

Once the cyanoacrylate joins were set, I added MilliPut to the the gaps between the tail booms and the wings. Before the MilliPut cured, I used small wads of paper towel wet with water to smooth away the excess MilliPut, because I knew once the MilliPut finished curing, it would become very hard, and it would be difficult to file and sand away any excess without nicking the surrounding soft styrene plastic too much, particularly in the hard-to-reach areas between the booms and the fuselage.

After the MilliPut had cured, I began the process of gently sanding away what little excess MilliPut remained. To fill any low spots where I had swabbed away too much MilliPut, I began to apply a product that was new to me: Gunze's Mr. Hobby: Mr. Dissolved Putty. This material is exactly what it sounds like: a model putty that has been thinned with some fast-evaporating solvent that makes the putty about the consistency of honey, molassas syrup, or thick latex paint. It can be applied with a paint brush and coaxed to flow into gaps and fissures. As it dries, it looses about half of its original volume, so I needed to apply two or three layers to completely fill the remaining gaps, wet sanding in between applications, to fully blend the air intakes, engine housings and wings together.

 

Tail booms glued to bottoms of wings, air intakes glued to tops of wings, Milliput and Mr. Dissolved Putty (buff color) applied to blend all parts together.
Mr. Dissolved Putty (buff color) filling in the gaps remaining from the application of MilliPut (cream color).

I heard a client once say, "When your health is on the line, don't ask your doctor to try something new and unfamiliar," which is good advice. Fortunately, the stakes with this model were nowhere near that high, and my learning curve with Mr. Dissolved Putty wasn't too alarmingly steep. It is pretty forgiving, easy to sand away anywhere I applied too much, and it does a terrific job of smoothly filling gaps and rough spots.

Right side engine/tail boom with air intake blended into wing with MilliPut (cream color) and Mr. Dissolved Putty (buff/pink color) applied.

The last major details to add to the model were the engine exhausts. I used aluminum tubing as the exhaust pipes, with a streamlining shroud made of Evergreen styrene half round and bar stock. The first installation of both exhausts on the left engine showed me that I didn't have the shape correct, yet: too proud of the engine. I easily pried off the loosely tacked-on parts from the engines, and reshaped the four exhaust units. Much better, I think. Cyanoacrylate formed the permanent bond and filleted the exhausts to the engines; 600 grit wet-or-dry sandpaper cleaned up the excess cyanoacrylate.

Aluminum tube at engine exhaust with Evergreen streamliner
Exhaust pipe with streamliner
Evergreen streamliners at exhausts.

Time to think about paint colors

Charger I prototype from magazine cover (Google)

The model is not too far away from masking and painting, so I've been thinking about which paint colors to consider. At this point, I'm pretty committed to the idea of an overall green scheme for a USMC Charger II, hypothetically not long after the aircraft had been first delivered to the Marines (late 1960s, say). I like how the Charger looks in the magazine photo above; I'd like for the model to evoke that feeling.

Below are three paint experiments. Each has been airbrushed with a Humbrol paint, then airbrushed with Johnson's "Future" Premium Floor Finish clear acrylic (to enable decals to be applied without silvering), then airbrushed with Testor's Clear Flat Lacquer (to restore the appropriate military matt finish). These three steps are how I paint all my models.

Please keep in mind that these paint experiments have been photographed under fluorescent studio photo lights, with a digital camera, on a (hopefully) neutral background, then PhotoShopped to correct the color, on a Dell computer, as seen on a Dell flatscreen monitor, and finally uploaded to the website, to be processed by your computer and displayed on your computer screen. Some change may occur... 

Humbrol No. 30 "Matt Dark Green"

Above is the right half of an engine/tail boom from the Academy OV-10A model that has so selflessly given its all to the project, airbrushed with Humbrol No. 30 "Matt Dark Green". This Humbrol paint is typically used for WWII RAF "Dark Green", can be used for WWII Luftwaffe "Dunkelgrun", and is a pretty close match for FS 34092, a USAF camouflage color used on the European I "Lizard" scheme such as was applied to the Fairchild A-10A deployed to West Germany in the 1980s.

Although I thought this paint was a good match for the WWII Imperial Japanese Navy Air Force "Dark Green" that I wanted for the Hasegawa Mitsubishi Jack fighter project, I think it is too dark and too blue-green in color to work for the Charger II.

Humbrol No. 159 "Matt Khaki Drab"

Above is the LEFT half of the same engine/tail boom from the Academy OV-10A model, airbrushed with Humbrol No. 159 "Matt Khaki Drab". I believe this Humbrol paint is typically used for soldier's uniforms and kits.

I was interested to see how this paint looked airbrushed on to part of a plastic model, since I have never used it before. However, I think it is too pale and too olive-yellow in color to work for the Charger II.

Humbrol No. 86 "Matt Light Olive"

Finally, above is the left half of the fuselage from the Academy OV-10A airbrushed with Humbrol No. 86 "Matt Light Olive". This Humbrol paint is typically used for WWII Wehrmacht three-color camouflage on AFVs and softskins.

I think this paint color may work very well to achieve the feel I want for the Charger II. It looks like a good approximation of the US Government Federal Standard color FS 34097, adjusted for scale color, that was specified for USMC aircraft in the 1960s (like the OV-10A). This should do it.  

Prototype Convair Model 48 Charger (Google)

I wanted to photo the Charger II on its landing gear, so I attached the struts with tiny pieces of double-sided tape; very unreliable. Despite all of the fishing weights I stuffed into every available cavity in front of the axles of the main landing gear struts, the model is just on the edge of tail heavy, prone to tipping back on to the tail skids. I'm not sure how to add more weight up front, or shave some weight from the back half. What I need (that doesn't exist) is a cast white metal nose wheel exactly the right size and shape.  

Scratch built Charger II with landing gear tacked on temporarily for photography.

After the tape failed repeatedly and the model collapsed during the photography, I tacked the main landing gear on with minute amounts of liquid plastic cement. While that dried, I shoe-horned two more bits of fishing weights into the front landing gear bay, which seemed to help solve the tail-sitting problem.

Scratch built Charger II with landing gear tacked on temporarily for photography.
Scratch built Charger II with landing gear tacked on temporarily for photography.

Masking the canopy

Once I believed all of the construction was complete (except for a pitot tube, if I can decide where to locate it), it was time to start painting, but before I painted, I had to mask the areas of the canopy that were to remain transparent. The first step in this process was to apply Tamiya masking tape in thin strips to delineate the canopy framing.

Tamiya masking tape to represent the canopy framing.
Tamiya masking tape to represent the canopy framing.
Tamiya masking tape to represent the canopy framing.

Note how the tape representing the canopy framing covers all of the joints between the pieces of FrankenCanopy, and the fillets between FrankenCanopy and the fuselage. Nothing but clear plastic is visible (I hope). 
 

With the canopy framing delineated, the next step was to outline the areas to be masked on the canopy. Very thin, flexible strips of Tamiya masking tape were used, to follow the compound curves of the transparent areas. This masking was applied right up to the edges of the tape representing the canopy framing. Note the little diagonal chamfers at the corners of the transparent areas, based on the drawing of the Charger II.

Tamiya masking tape to outline the areas of the canopy to remain transparent.
Tamiya masking tape to outline the areas of the canopy to remain transparent.
Tamiya masking tape to outline the areas of the canopy to remain transparent.

Once all of the areas to be masked were outlined, the next step was to fill in the remaining clear areas. After that, I removed the Tamiya tape that delineated the canopy framing, exposing the parts of the canopy that were to receive paint. Now you can see the joints in the canopy and the fillets between the canopy and the fuselage. All that sausage making will be covered up.

Masking completed, with tape at canopy framing removed to expose canopy framing to paint.
Masking completed, with tape at canopy framing removed to expose canopy framing to paint.
Masking completed, with tape at canopy framing removed to expose canopy framing to paint.

Studying these pictures, I have to acknowledge that the canopy framing appears a little beefy, to cover a multitude of sins in construction, but so be it.

Note also the custom holder I fabricated from Evergreen styrene plastic and K&S brass and aluminum tubing, inserted into the tube bushings for the propeller shafts, so that I can airbrush, decal, install the last parts and apply the flat finish on to the model without having to handle it. I usually make one of these for every model aircraft I build. On jets the holder is inserted into the engine exhaust tube(s).

The painting begins

Charger II with Humbrol No.86 Matt Light Olive overall.

Once the canopy masking was in place, I plugged up the wheel wells with small blocks of foam rubber to mask the wheel wells from overspray of the Humbrol No.86 Matt Light Olive. I thinned the Humbrol a little more than typical, because I knew I wanted it to airbrush on to the model a little wetter than usual. I also sprayed at a little lower pressure than normal, perhaps 10 to 12 psi (who knows how accurate the indicator on the pressure gauge of my compressor may be?). 
  

Charger II with Humbrol No. 86 Matt Light Olive overall. Wheel wells awaiting masking and paint.

All of this was necessary because one outcome of airbrushing a complex shape (involving wings, engine booms and a fuselage all forming right angles with each other) can be a grainy finish. The air flow from the airbrush swirls against the surface at which you are aiming, and carries partially-dry paint to any adjacent, right angle surface. This partially-dry paint doesn't flow as wetly, and a rough, grainy texture can form. By using less pressure, you get less swirling, and by using wetter paint, the flow is better.
 

Charger II with Humbrol No. 86 Matt Light Olive overall.

The drawbacks to these adjustments to viscosity and pressure are that it takes more time to cover the model with the smaller spread of more weakly-driven paint, and yet you have to watch for too much runny paint suddenly building up on some part of the model while you aren't paying attention. It takes a lot of practice and mistakes, with the attendant darkly-muttered vocabulary.

Charger II with Humbrol No. 86 Matt Light Olive overall.
Charger II with Humbrol No. 86 Matt Light Olive overall.

After I finished airbrushing the aircraft, flying tail and landing gear doors, I airbrushed the landing gear struts and wheel hubs with Humbrol No. 27 Dark Grey, and the propellers with Humbrol No. 67 Panzer Grey (approximating scale flat black). Later I will hand paint the tires with some appropriately tire-colored paint.

 

Flying Tail, wheels, landing gear struts, wheel well doors and propellers painted.

After the paint was thoroughly dry (a couple of day's wait, until I had the free time and energy to do so), I carefully inspected the painted parts for stray dust, fibers and cat hairs that had drifted into the wet paint as I was applying it. As much as I could, I very delicately plucked out the intruders with a pair of tweezers that I had long ago filed, sanded and polished into a needle-sharp point, for just this purpose. It is very easy to inadvertantly scratch the paint while doing this, so I was very, very careful.

Applying the clear gloss finish

All Charger II components with a coat of FUTURE clear acrylic.

The next step was to airbrush all of the painted parts of the entire model with Johnson's FUTURE Premium Floor Finish, a clear acrylic. This step prepares the paint to better receive decals, helping to avoid "silvering" (air trapped under the decals that reflects light, appearing white or silver). The FUTURE also protects the paint from damage during subsequent handling, such as the application of masking tape prior to painting other colors.

Charger II with a coat of FUTURE clear acrylic.

I have found that something about applying the FUTURE to the paint somehow affects the finish in a positive way, making the engraved lines stand out a little more, modulating the curves of the model's surfaces a little better, and smoothing out any roughness in the paint finish. The FUTURE does have the effect of making the paint look darker (like wetting any matt surface makes it look darker), but I allow for this in the paint selections and any lightening with white paint that I do for scale effect. To see an example of this phenomenon, click HERE. From the top of the BUILD JACK Page 2, scroll down to the heading called  Airbrushing "Future" clear acrylic to paint samples and JACK underside.
 

Masking and painting the wheel wells

Entire model masked with Tamiya tape and Saran Wrap, leaving only the wheel wells exposed.

Thin strips of Tamiya masking tape were applied around the edges of the wheel well. More tape was applied to expand the masked area. Then, Saran Wrap was carefully laid over the masked areas, the locations of the wheel wells were marked, rectangular holes were cut through the Saran Wrap on a sheet of glass, and then Tamiya tape was applied to stick the edges of the Saran Wrap openings to the edges of the masked wheel wells. All this to control where the Humbrol No.147 Matt Light Grey ended up.

Masking removed after airbrushing wheel wells with Humbrol No.147 Matt Light Grey.

Applying the decals

I had planned to use some of the USMC decals from the Academy OV-10A kit on the Charger II, but a test of one Academy decal revealed really persistent silvering, even on FUTURE clear acrylic, even with Micro-Set and Microl-Sol decal setting solutions. So, on with some tried and true SuperScale decals, instead.

Charger II with various SuperScale decals applied and top coat of FUTURE clear acrylic.

I harvested USMC unit markings, US national insignia and various warning/emergency signage from several SuperScale and MicroScale decal sheets, part of a 40 year collection of several hundred decal sets. I applied the markings to the Charger II based on studying similar markings on USMC OV-10A Broncos.

Charger II with various SuperScale decals applied and top coat of FUTURE clear acrylic.

The final assembly of parts

The next step is to install the landing gear struts and wheel well doors. The trick here is to try to get the struts and wheels to be straight, plumb, aligned with each other and symmetrical, and for the model to sit appropriately level with the ground plane. To do this, I attached the main wheels to the landing gear axles with 30 minute epoxy, and I rested the model of a sheet of plate glass, adjusting the alignment of the wheels while the epoxy sets. On the Charger II, the front wheel is free to spin on its axle, so it is self-adjusting. Prior to installing the three wheels, I carefully ground flat surfaces on each tire, to simulate the weight of the Charger II deforming the tires. The sheet of plate glass gives me a perfectly level surface upon which to align the three flats on the tires.

Charger II with landing gear struts, wheels and wheel well doors installed
Charger II with landing gear struts, wheels and wheel well doors installed.
Charger II with landing gear struts, wheels and wheel well doors installed.

Once I was content that there was little or no silvering under the decals, I airbrushed a final coat of Johnson's FUTURE clear acrylic over the entire model. This seals the decals and provides a uniform surface for the clear flat lacquer to come. Experience has taught me that the flat lacquer finish provides a noticeably different sheen on the raw decals than it does on the acrylic FUTURE.

During the time the Charger II was on the airbrushing handle, I got used to how sleek it looked. Adding the landing gear and wheel well doors really cluttered up its smooth lines. I'm especially glad now that I didn't add any weapons hanging off of the wings and fuselage.

Applying the flat finish

Charger II with Testor's Clear Flat Lacquer overall.

With the decals sealed under a final coat of Johnson's FUTURE clear acrylic, it was time to restore the matt finish to the model, to more closely replicate the usual non-glossy appearance of a military aircraft. Testor's Clear Flat Lacquer was applied with the airbrush to all of the remaining parts of the Charger II.

Charger II with Testor's Clear Flat Lacquer overall.
Charger II with Testor's Clear Flat Lacquer overall.
Charger II with Testor's Clear Flat Lacquer overall.

The Charger II is finished

The last steps were to remove the canopy masks and install the flying tail and the navigation lights. Today is June 27, 2015, and I think the Charger II is finished. This project was started eight months ago, on October 25, 2014. 

Click on the thumbnails below to see larger images of the completed model.

Thanks for looking. Hope you enjoyed the ride. I know I did. Now to select the next project. Probably some simple kit, built right out of the box...

Scale 1/72

Email: AtomicCannon(at)embarqmail(dot)com