Tamiya 1/48 F4U-1 WM Conversion

Pratt & Whitney made a proposal to the US Navy Bureau of Aeronautics in early 1943 that an R-4360 engine should be installed in the F4U airframe. The US Navy Bureau of Aeronautics, 'BuAer' instructed Vought on March 24, 1943 to take an airframe destined for delivery to NAS Jacksonville, Florida and to deliver it to Pratt & Whitney in Hartford, Connecticut for their use as a proof of concept aircraft. Pratt and Whitney was loaned an F4U-1 Birdcage Corsair, BuNo 02460  for the installation of a new engine, the twenty-eight cylinder Wasp Major , TSB1-G experimental 3,000 horsepower engine.  The goal was to establish if the airframe and 3325 pound engine were compatible. Table 7-2 in the Graham White R-4360 engine book showed the weight increase from the R-2800 Corsair to the R-4360 Corsair to be 1,248 pounds, the engine itself adding 866 pounds.

On July 17, 1943 BuNo 02460 flying with its R-2800-8 engine was delivered to East Hartford, Connecticut. A simple conversion followed with the external cowl dimensions maintained and a cowl lengthened by 12 inches accommodated the new powerplant. The TSB1-G engine was a semi-production version. The fourth  engine, '#4' was used for installation in the BuNo 02460 Corsair. There were four TSB1-G  'XR-4360' engines produced under specification number 7031. The Hamilton Standard 14 foot propeller was delivered on August 26, 1943.

BuNo 02460 was an early airframe since production F4U-1 Corsairs started with BuNo. 02152. What is notable about these aircraft in the F2G development genealogy is they were Vought manufactured and made for use by Pratt & Whitney and not made by Goodyear aircraft Company (GAC) who was the eventual builder of the final production aircraft designated F2G-1/2.

Ground runs were initiated on September 6, 1943 and the first flight occurred on September 12, 1943. The TSB1-G engine featured a lighter and simpler single-stage, variable speed supercharger. This engine provided high power at low altitude without the complexity of a two-stage intercooled engine like the existing R-2800 Corsairs. This resulted in the change to a smaller wing air inlet.

During its development, a variety of carburetor air intake configurations were tried. Thus, you may find several variations of the 'WM' depending on when the photo was taken. As Graham White noted in his book 'Several styles of induction scoops were tried on the F4U WM including a so-called flush scoop and a raised scoop'.

I found an excellent photograph of one of the 'WM' aircraft on Pratt & Whitney Corporations website. It is for sale and I purchased an 11' X 14' sized copy which helped with establishing many details for this modeling effort. It also added a new paint scheme to my future project list since it appears to be a late war star and bar marked aircraft with a white nose tip and horizontal white stripe on the vertical stabilizer! One reference shows F4U-1 WM BuNo 02460 with a smaller air intake and a prominent horizontal panel join line and BuNo 02460 in Test Phase 2 with five cowl latches on both sides of the cowling similar to some of the final F2G versions.

 No specific kit information provided. Check the previews section. Ed

This model represents a conversion to the Tamiya kit # 61046 F4U-1 Birdcage  Corsair. I  modified it to represent the first prototype of the R-4360 engined Corsair designated F4U-1 WM (for Wasp Major). This aircraft was the first proof of concept aircraft to determine what would happen if a new engine, almost double the size of the largest existing WWII radial fighter engines was installed in an existing airframe - that of the F4U-1 Corsair.

The F4U-1 WM Corsair had major modifications from earlier Vought Corsairs:

P&W XR-4360 Wasp Major engine which also caused changes to the induction, exhaust, supercharger and deleted the intercooler systems. Externally it gave the Corsair a much longer engine cowling.

Larger prop – it used a larger Hamilton Standard “Super Hydromatic” 14’ four blade propeller.

New 'raised ram-air' induction intake and 12 inch extension to the F4U-1 cowling to accommodate the longer engine.

New wing tanks increasing fuel from 234 US gallons to 309 US Gallons.

Smaller square shaped wing root intakes only for the oil cooler since there is no intercooler. It was redesigned for the final F2G versions.

Extended upper exhaust tips cut at 90 degree angle and connected by a metal bracket without the siamese interconnected exhausts of later R-4360's.

The late, test phase 2 version had two pitot tubes to provide extra instrumentation logs, thus there are two pitot tubes - one per wing. This was not found on the aircraft during the first two phases of WM testing. See the photo reference on the P &W website.

A six-inch in diameter Pratt & Whitney Company logo was placed on each side of the front cowl, in the center of the first panel section on what appears to be a circular engine inspection access plate.

Depending on the date of the photo they sometimes carried arrestor landing hooks and sometimes had them removed. Photo references show it attached. 

What made this conversion possible was the use of the War Eagle vac-form fuselage parts and Aves Apoxy for sculpting the carburetor scoop. I purchased Apoxy from the Aves web site. (Your editor thinks that Andy means Apoxie-Sculpt, an excellent two part epoxy filler that most of us have been using for many years. Most well stocked hobby shops, including many of MM's advertisers, carry it or can get it. I recommend the smallest containers, for unless you mold your own figures [and a lot of figure sculptors use this], you'll find it will go a long way and last a long, long time.)

The Tamiya F4U-1 Corsair is a well documented enjoyable build. Most of the construction is a straightforward “Tamiya build” – cut, file, sand and glue. The cockpit is very nice OOB and by adding the Eduard FE216 painted zoom etched metal parts and FE244 F4U-1 Corsair placards the cockpit can be greatly improved. I had an Aires Resin F4U-1 Birdcage cockpit in the stash and decided to use it on this version.  It is outstanding in detail but requires careful cutting and dry fitting to ensure it will fit. I also added many Eduard color zoom parts to the Aires resin. The use of additional bits from Eduard F4U Corsair placards further enhanced the Aires cockpit and engine.

There is no need to fill in the extra machine gun port on the wing leading edge and also the 3^rd wing gun port and spent gun-casing chute underneath the wing since this prototype maintained the F4U-1 six-gun configuration.

Now, the larger part of the conversion gets underway. I cut the nose from the War Eagle F2G vac-form and grafted it onto the Tamiya Corsair fuselage. I added several thick styrene strips for reinforcement to securely attach the long cowl. I cut along a natural panel line that both Tamiya and War Eagle had making the final merge easier.

By careful cutting and measuring the two halves joined well without any mis-fit. I used Aves Apoxy as my putty to fill in the gaps and placed styrene strips under any gaps to allow the putty to work better and fill-in small areas. You can use small amounts of water to wipe away excess putty when it is first applied and avoid a lot of tedious sanding and damage to panel lines. I held off on the Gunze Mr. Surfacer until final pre-painting preparation.

Once the two fuselage halves were completed but not yet joined together, I turned to the challenge of finding an R-4360 replacement engine. I used Engines & Things # 48093, R4360 engine as the replacement for the Tamiya R-2800 engine.  I used some plumbers putty as a mounting ring at the rear of the engine and before the putty hardened positioned the engine nose to both center it and provide the clearance required from the cowl. After it hardened, which took all of ten minutes this step was completed. I then joined the two fuselage halves using Tenax glue. Basically the engine does not fit OOB. You will need to grind down the engine heads to permit a fit. Once inserted and closed up you won't notice the engine re-sizing.

The underside was modified in the exhaust area to provide for the changed exhaust configuration. Thanks to Rodney William's I had his excellent advice and references to modify this area for the proper exhaust and engine flap configuration. There are three exhaust flaps with six exhaust pipes separated by two fairings. The Tamiya kit cowl ring, Part # A-14 was cut and modified to provide the underside and topside exhaust flaps. The 'WM' flap segment size is different than the F4U-1 so you need to fill in and rescribe the flap segment size. I used some brass tubing for the exhaust stacks cut at the 90 degree angle. Later F2G versions used a 45 degree cut for the upper exhaust.

I followed the rest of the standard Tamiya kit instructions to complete the build. If you have built one of Tamiya’s Corsair’s you know it is a very smooth process helped along by parts engineered to fit only one way.  This keeps an overconfident modeler in line and guarantees a fine final result.

The engine air intake was created using Aves Apoxy. I used low tack masking tape to designate the footprint of the air intake. This helped me establish the panel lines and maintain the correct size of the intake during the free-hand shaping, cutting and grinding operation.

I used the amazing Pratt & Whitney photograph found on page 323 of the R-4360 Pratt & Whitney’s Major Miracle by Graham White textbook, to correctly shape the scoop which is very different in appearance than the final scoop used by the F2G. It was the perfect photograph and the only photograph I could find from the correct angle needed to produce the correctly shaped and positioned scoop.

The long setting time, about eight hours for Apoxy, allowed the rough form to be shaped without rushing. I allowed it to harden for 24 hours. A Dremel motor tool set at a slow speed with a very small routing bit was used to shape the intake once it hardened. Aves Apoxy feathers into the plastic very well.  It is easy to sand and polish once dry. By using low tack masking tape to outline the footprint of the scoop the panel lines were easily established.

I used the Tamiya front fuselage antenna mast as per the normal F4U-1 construction step. My main source for details after photo references was the  schematic sheet # 43, page 87, AJ Press text which has two versions of the 'WM' Corsair featured showing the subtle differences.

The canopy came from the Tamiya kit. It looks very nice once installed and clarity was improved after a future floor polish coating.

The War Eagle kit provided a resin four-blade 14” super hydramatic prop. It has a very nice shape and after twelve years in storage was not warped. A connecting shaft between the resin engine and the prop was formed from a metal rod taken from a paper holding clip (the ones that look like large clamps). 

I added the Aires rear view mirror to the Tamiya canopy. The canopy used by the WM was the birdcage with a rear-view mirror 'hump' version.

  Formation and position lights - Testors chrome silver followed by a small dab of white paint on the tail light at the end of the rear fuselage tail cone, along with the fuselage spine light followed by painting the wing tip lights and the three underwing lights. I added small drops of clear epoxy to simulate clear light covers. This is one of the many nice techniques I picked up from Brett Greens Osprey series Corsair Modeling book. By using xylene or lacquer thinner with Testors chrome silver the hardening and drying time are significantly improved.

  I enhanced the Aires gunsight by attaching a bright metal foil disc obtained by punching a disc, using a Waldron punch set, from a Cadbury's chocolate candy wrapper. I initially applied a clear epoxy drop to give it a glass dome look but had to remove the epoxy drop due to the tight clearance of the Aires gunsight and the kit canopy with the Aires armor glass windscreen insert.

 The WM appeared in at least three different color schemes - early rollout, test phase one and late war test phase two.

The early rollout WM Corsair had no prop tip color and featured a bare-metal front prop surface with a flat black rear color on the prop. National markings were the white star in blue circle markings and the blue gray upper, light gray under surface paint scheme. The cowl had a P&W logo identifier on both sides. Thanks to a trade with Dave Wells, I obtained the P&W decal cut from an OOP Liveries Unlimited AGAX-001 decal sheet. The air intake was the initial rollout large raised scoop version.

Test phase one saw the change to a star and bar national marking scheme and the blue gray upper, light gray under surface paint scheme. The propeller blades were now painted matt or flat black with yellow tips. The arrestor hook was retained. A slightly smaller raised scoop was installed.

Test phase two used the star and bar national markings and the blue gray upper, light gray under surface paint scheme. It carried a distinctive white nose tip and horizontal white stripe on the vertical tail surface. This version can be found on the Pratt & Whitney Company web site as a 'for sale' photo. The arrestor hook was removed. Several air intake configurations were used during tests including a flush mount and small raised scoop. 

This model is painted in the test phase one scheme which was the standard paint scheme for all early Corsair's - the F4U-1 used the two-tone camouflage scheme in effect from 10-13-1941 until  2-1-1943.

Non-specular Blue Gray (ANA 603) similar to FS 35189 on upper surfaces and on the under wing surface that folded upward.

Non-specular Light Gray (ANA 602) similar to FS 36440 on lower surfaces - fuselage and that portion of the wing which did not fold.

National markings of white star in blue circle in six positions. Black is used for stencils (US NAVY, F4U-1 and BuNo 2460.

I used a mixture of Gunze H042 Blue Gray with H015 Bright Blue for the upper surface and Gunze H315 Lt. Gull Gray for undersurfaces.  For the engine I used Testors enamels. Testors gloss with some dullcoat was used to create the final finish. I added some weathering around the markings and some surface areas.

Decal national markings came from a Superscale decal sheet and stencils were from a mix of Superscale and Tamiya kit decals. A combination of Tamiya kit (61046) decal # 13 and # 24 gave the correct black BuNo stencil detail.

There was another F4U-1 WM Birdcage Corsair, BuNo. 02312 which was the R&D static test and development airframe used to test fit and evaluate airframe  modifications installed in BuNo 02360 for flight tests.

It was a very enjoyable project that I have been intending to do for many years. I have a few more F2G related builds in final stages representing other versions.

That’s it! All in all it was a fun build and a definite conversation piece at modeling events. The new Accurate Miniatures release of the SH kit has some new U.S.  Navy decals for other military F2G’s so the future is looking better. Perhaps Yellow Wings decals will be coming out with an F2G decal sheet. Let Wayne Tevlin at Yellow Wings Decals know if you are interested in his releasing an F2G decal sheet. He can be contacted at http://yellow-wingsdecals.com/decals/contact_us.php?osCsid=2241168189145c56ffbed7089aa4c80a

R-4360 Pratt & Whitney’s Major Miracle by Graham White  Specialty Press  2006

Pages 314 to 323.

F4U Corsair – AJ Press Aircraft Monograph 19 by Adam Jarski   2005

Pages 29, and schematic drawings Sheet 43, page 87 for both of the WM aircraft.

Modelling the F4U Corsair by Brett Green , Osprey Modelling # 24, 2005

Corsair – Thirty Years of Filibustering 1940 –1970 by Bruno Pautigny – Histoire & Collections Books 2003

F4U Corsair In Action, Squadron Signal Publications # 1145 1994, page 11 in Phase 1 test color scheme.

PWA Report Inst. 146, November 15, 1944 by A.S. Horwath and R.N. Wallace 'Installation and Test of an R-4360 Engine in the F4U-1 (WM) Airplane.

United Technologies Pratt & Whitney Company website

Bureau of Naval Aeronautics F2G-1+2 Bu No Genealogy: Follow this link

Andy Garcia

June 2008