Monogram/Koster 1/72 P-72 Ultrabolt
KIT #: ?
PRICE: $35.00 total
DECALS: Two kit options
REVIEWER: Dale Rannals
NOTES: Koster Aero Enterprises XP-72 vac conversion, Jaguar resin cockpit set.


December 1945 was not a good time to be in New Guinea.  “Actually, anytime in the last several years was not a good time”, thought Jesse as he shot skyward in his Ultrabolt.  But after the catastrophic raids on Wewak in ’44, which resulted in huge allied losses, things got much worse, with the allies trying desperately to hold Port Moresby.  After a screaming climb to 23000ft, Jesse leveled “601” off and started looking around; first to see if his wingman and the rest of the flight were still with him, second to start searching for the tiny dots that would inevitably grow into the sinister shapes of the attacking Japanese forces.  Radar controllers reported a large force coming from Rabaul, so north it was, and Jesse turned his flight in that direction. Another assault, further back, was coming in from Wewak, but the north force had to be dealt with first. The Chain Lightnings that took off last would try to defend the base from the other group. This was a dance repeated many times in the last few months.  Of course it seemed like forever.

As 601…or “Jenny” or “Stinger” …depending on was flying her, settled down into a vicious purr, Jesse spotted the specks slightly below his level, right where the radar controller said they would be.  Just then a frantic radio message called out aircraft at five o’clock high.  Necks twisted to look and tensions skyrocketed until they were called out as Navy Fireballs. “Enterprise must be back on station…” thought Jesse, “….good, we can use the help.”  Still in the fight after all these years, the old girl just returned to the Coral Sea after the last set of repairs….ready once again to help defend Port Moresby.  The enemy formation grew in size until shapes could be made out.  G5N “Liz” four engined bombers escorted by Franks and the bizarre, backward shape of the Shindens.  Need to keep an eye on those, thought Jesse.  Fast, with heavy cannon in the nose, they were a formidable adversary….one hit, even to an Ultrabolt, could indeed ruin your day.  The ‘Bolts were faster still, one just had to keeps one’s wits about him and one’s speed up.

Fast, faster, fastest.  Just at the merge the Fireballs flew past and into the heart of the bomber formations.  Though they didn’t look fast, the piston and jet engined dark blue fighters gave the Navy Jocks a definite speed advantage in this party.  Since the Fireballs could slice at the bombers without interference from the escorts, Jesse turned his full attention to the enemy fighters.  He fire-walled the throttle and fuel dumped into each of the 28 cylinders of the beast of a motor.  Six huge blades of the contra-rotating propeller clawed at the air in a desperate attempt to transform more than 3200HP into thrust. Jesse was pushed back into his seat as 601 literally shot forward in the sky.  As speed increased, Jesse and his wingman zoom climbed, inverted, and came down on top of four Shindens.  Sights on the leader…. press the trigger.  Six .50 caliber machine guns come to life.  A short burst, but enough to show strikes on the target.  He watched it start to smoke and go down as he plunged thru the enemy group and lost sight of it.  Jesse continued the dive, ripping thru masses of twisting and turning planes, somehow avoiding a collision with any of them.  Leveling, Jesse spotted a pair of enemy fighters and banked towards them.  Midway thru the turn, tracers flashed past his canopy and his right wingtip disappeared as one of the explosive cannon shells found a home.

Instinctively, Jesse snap-rolled the ‘Bolt and dove, weaving as more tracers raced past him.  He looked back just in time to see the Shinden explode as his wingman got him sighted in.  The ground raced up to greet them as they both pulled out of their dives.  Looking around quickly, they realized at once that they were now alone in the sky, not another craft to be seen.  Their part in this dance was already over.  Jesse surveyed the damage.  About two feet of his starboard wingtip was gone, but the bird still handled well.  They banked to the south to head home and saw smoke rising in the far distance. 

“Let’s see how hard we were hit this time………”

The reality:

The Republic XP-72 was an American prototype interceptor fighter developed as a progression of the P-47 Thunderbolt design. Even though the XP-47J was showing loads of potential, Republic had their eyes on a new engine.  The XP-72 was designed around the Pratt & Whitney R-4360 twenty-eight cylinder radial air-cooled engine. A GE turbo-supercharger would be housed in the aft fuselage.  The armament consisted of six 0.5 in wing-mounted machine guns and underwing racks for two 1,000 lb bombs.

The XP-72 development paralleled that of another Republic design, the XP-69 that was to be powered by an experimental forty-two cylinder Wright R-2160 radial engine mounted behind the pilot and driving contra-rotating propellers through an extension shaft. The XP-69 was intended for high altitude operations and featured a pressurized cockpit and armament of two 37 mm cannon and four 0.5 in machine guns. As the XP-72 displayed greater promise than the XP-69, the XP-69 was canceled on 11 May 1943 and an order for two XP-72 prototypes was placed on 18 June 1943.

            Development was amazingly trouble-free, with the first airframe, equipped with a four bladed propeller, flying for the first time on 2 February 1944. The second prototype was completed on 26 June 1944 and was equipped with an AeroProducts 13.5ft. contra-rotating propeller. Both propellers were so large that the aircraft had to take off and land in a three point stance to avoid propeller strikes. Test pilots reported the aircraft as a joy to fly.  As the XP-72 displayed exceptional performance during flight tests, with the prototypes rapidly accelerating to 490mph at 25,000ft, an order for 100 production aircraft was awarded. The order included an alternate armament configuration of four 37 mm cannon. By this time the war had progressed to where the need was for long-range escort fighters and not high-speed interceptors. Also, the advent of the new turbojet-powered interceptors showed greater promise for the interceptor role. Thus, the production order for the P-72 was cancelled and so ended its brief career.


The very nice Koster vacuform XP-72 Ultrabolt conversion is made for Monograms P-47 kit.  The conversion consists of two fuselage halves and two cowl halves, both on a single sheet of white vac plastic, a resin intake and cooling fan, and an 8 piece resin propeller/spinner assembly.  The vac parts are nicely done but my resin bits exhibited several minor flaws and air bubbles.  No biggie and not hard to take care of at all.  The vac parts have raised panel lines to go with the Monogram kit, but would be very easy to sand off and re-scribe if one wanted to.

 The Monogram P-47 Bubbletop kit.  It may be surpassed in parts count and detail by the newer Academy, Tamiya, and Hasegawa offerings, but it still makes a fine replica of Republic’s big fighter.  Once again Monogram managed to capture the character of the beast.  I picked up my kit cheap at an online auction.  It was a bagged kit and came sans instructions or decals, but that was fine, as I needed neither.   This venerable kit is nicely molded in olive colored plastic and this one exhibited no flash on the parts.  Two clear canopy pieces completes the ensemble…..the canopy can be made to open and close.  (As a side note, for this conversion one could just as easily use Monogram’s Razorback version, as the donor parts of the kits…the wings, gear, cockpit, etc…..are the same.)  Be sure to save the propellers for other Thunderbolt kits, as the Razorback comes with a “toothpick” Curtiss Electric, and the Bubbletop has a Hamilton Standard prop.  Never throw parts away. 


The first thing I had to do is cut out and sand down the vac pieces.  This really isn’t as scary as most think it is.  Here are the steps I use:

1.  Get a sharp pencil.  Draw a line around each part on the sheet.  Use a larger X-acto knife with a curved blade (#11 blades seem too flimsy for this) and score on the outside of the pencil mark of each part, trying to keep the knife at about a 45 degree angle, angled in towards the part.  

2.  Snap, don’t cut.  No need for the score to go all the way thru, as the next step is to “snap” the parts from the sheet.  Just work your way around each part and separate it from the sheet.

3. Next, carefully sand down all the parts to eliminate the “waste” plastic that is there.  Cutting the parts at a 45 degree angle back “into” the parts helps reduce the waste which helps reduce the amount of sand time, and anything that reduces the amount of sanding is a good thing.  This is also where the pencil mark comes into play. 

Remember, the pencil line rules!!   Do not forget this.  Pick a suitable flat area and tape some sandpaper to it. (At the local hardware shop I found some “sticky back” sandpaper sheets….these worked well and can be put down and peeled up multiple times.)  The idea is to sand until the pencil line just disappears, but no farther.  Check the part often, check the line often.  Also adjust your grip on the parts often, so you don’t sand too much from the area you’re holding on to…the dreaded “banana effect”.

Once I had the fuselage pieces sanded down, I glued small tabs on all the vac pieces to serve as alignment aids and to give the glue some surface to bite into (as the vac pieces are thinner than normal injection parts).  From this point on the sequence is pretty much the same as any regular kit.  One does has to be a bit gentler with the vac parts, because of the aforementioned thinner gluing surface.  So now that we’re done here…..onto the cockpit.

I bought a Jaguar P-47D resin cockpit set a while back and decided to use it here.  These resin bits looked great, built up nicely, and as a bonus fit perfectly inside the vacuform fuselage. I painted the cockpit and fuselage sidewalls a darkish bronze green (Model Master enamels) I had mixed up. The instrument panel and some of the sidewall details were painted VDG (aka: very dark gray…..I never use straight flat black as it seems too intense) and the ensemble was dry-brushed with a lighter gray to pop out more details.  I glued in an Evergreen square tube “ledge” on the right fuselage half for the cockpit floor to rest on and once this was dry I super-glued the cockpit in place, along with the resin turbocharger intake.

The fuselage halves were then glued, joined, and taped….. then set aside to dry. Turning my attention to the cowl halves, these were joined with the front opening still “plugged” as this gave me a sturdier shape to deal with.  Once it was dry I grabbed a new blade and carefully cut out the cowl opening.  I sanded the opening smooth and glued in the resin cooling fan.  This assembly was then glued to the fuselage.

Next the Monogram wings were glued together and the leading edges sanded smooth.  I cut off the gun barrels, having two reasons to do so.  One: Monogram molded the guns in-line, or level, with the wings.  The guns here should be level with the ground…they “slant” across the leading edge of the wing.  Two:  I knew I’d manage to break most of them off anyway during the build, so now I didn’t have to worry about it.  I attached the wings and the horizontal stabs to the fuselage and used a Lego jig to keep things even until all was dry.  The wing root seam wasn’t too bad…a few applications of putty and surfacer smoothed things out. 

The propeller assembly turned out to be more work than I initially thought.  I removed each of the six blades and cleaned them up.  The hub assembly wasn’t very pretty; it looked rough and out-of-round.  I sanded the base flat and found, marked, and drilled its center point.  I left the drill bit in it and mounted it in my cordless Dremel.  On its lowest speed and under a stream of tap water, I ran a sanding stick over its surface to even and smooth things out.  Much nicer now.  I drilled out the prop mounting holes and began installing the blades.  I had a very hard time figuring out which blade went where; each blade is symmetrical with a strange twist.  I ended up just angling three one way and three the other.  I also broke off three of the six while attempting to get the alignment right.  I sanded the breaks smooth, drilled tiny holes in each, and re-attached using small sections of wire (from small paper clips). 

I believe it’s time for the paint shed………


This obviously is not your normal Thunderbolt build, so I really didn’t want to put it in “normal” markings.  So no ETO with squadron codes.  The Italy-based squadrons had some interesting variations ….in particular I liked the markings of Lt. Knights “Oh Johnnie”.  Then my thoughts drifted upon the Pacific and a desperate defense of Port Moresby in New Guinea circa late 1945.  I decide to keep the details of Lt. Knight’s ship and adapt it to this whiffer campaign.  So....olive drab over gray; no natural metal here as air superiority is hardly the case.  I also was drawn to the many aircraft with “multiple personalities”; with many pilots flying the same aircraft. 

            So step one was neutral gray.  I sprayed the whole aircraft so it would be easier to see and areas that still needed attention.  Once these were cleaned up I masked off the underside and sprayed a greenish olive drab on the topsides.  Both the gray and the OD...... all Model Master paints here, BTW..... were then assaulted with lighter shades in the panel centers and darker shades on the panel lines to break up the monotone of each area.   I let this dry for a day and then hit everything with some Future to prep for decals.  At this point I dipped the canopy in Future, let it dry, masked, and painted it flat black (internal framing) and then Metalizer Non-buff Aluminum.

            The decals came from several decal sheets.  Wing insignia, “Jenny”, the rudder checkerboard, and serial numbers came from Thunderbolt sheets.  Fuselage insignia from a Mustang sheet, “Stinger” came from a Lightning sheet and the kill markings from a Hellcat sheet.  I've always thought Japanese kill markings on Thunderbolts grab peoples attention, as it isn't what they think should be there.  The only problem I had with any of this is the 601 on the port side...a couple of wrinkles would not settle down no matter how many applications of setting solution I applied.  I ended up lightly sanding away the ridges and touching up the areas with white paint.  I kept the weathering very light figuring 1) the would try to keep the hot rod polished up and 2)  in this scenario, any individual plane wouldn't last long enough to get all that beat up anyway.

             I painted the whole propeller assembly yellow, then went back and painted the blades black (again actually VDG), leaving the hub and tips yellow.  Then I applied some Curtiss Electric decals to the blades.  The prop was actually an AeroProducts unit; as I did know what went on their props and had an abundance of CE decals, ....on they went.


            I painted up some resin wheels I had for a P-47N and attached them to some OD painted landing gear.  These and the gear doors were added, along with the tail wheel.  I drilled out six holes in the wings for the guns.  I did not do a very good job at getting them level, but it will do.  I added stainless steel tubing for the gun barrels and painted them black.  The canopy came next; it had a small gap on the port side but nothing I was going to worry about.  Add the prop and a whip antenna and call we'll her done


  I had a bunch of fun doing this conversion.  It helps of course that I love Thunderbolts in all flavors, but being able to do these “one-off” types is icing on the cake.  It also helps that the Koster conversions are very reasonably priced and that the Monogram donor kits won’t break the bank either.  They are a perfect stepping stone to “try out” vacuform modeling before jumping into a full vac kit.  So grab one and let your imagination run. 


 US Experimental & Prototype Aircraft Projects  ISBN: 978-1-58007-109-3

Interior colors of US aircraft:

Squadron/Signal P-47 in Action

Dale Rannals

February 2011

Kit courtesy of my wallet.....the rest courtesy of my imagination.

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