Getting It Right

This is another in a series of examples of how hard it is for model kit manufacturers to produce one with no errors of shape or detail.

The Mk 4 atomic bomb was the improved production version of the Mk 3 Fat Man that was dropped on Nagasaki. According to Chuck Hansen's book, U.S. Nuclear Weapons: The Secret History, the first one was delivered to the the national stockpile on 19 March 1949. A total of 550 were built between March 1949 and May 1951. All were retired by May 1953, replaced in part by the very similar but lighter Mk 6.

Because of the security imposed on these weapons, documentation is scarce. The 12 Squared Mk 4 kit (see Here) was based on the following drawing, which turns out to be for a 1/2 size ballistic test specimen. What looks like a gun-type mechanism (the Mk 4 actually had a spherical implosion device, accounting for its very low aspect ratio) was actually a pipe on which was mounted two 700-lb lead weights. The afterbody was a straight taper with four simple fins mounted on the back.

Bill Maloney (web page) photographed a full size Mk 4 model with this fin configuration that is in the Diefenbunker Cold War Museum about 20 miles west of Ottawa, Canada. It was built by Russ Gray in 2003 for a documentary film. Note that the afterbody is more bulbous than the drawing above.

I don't know whether the original Mk 4 had fins like the one above. The more familiar configuration has wedge-like fins.

 

 I don't know if there are any other Mk 4 shapes on display. However, there are a few Mk 6 shapes in museums, including the National Museum of the US Air Force at Dayton, Ohio and the Museum of Aviation at Warner Robins AFB, Georgia. The Mk 6 appears to be externally identical to the Mk 4 except for circumferential stiffeners around the mid-body resulting from a change to a lightweight casing that reduced the bomb's weight by 2,000 lbs.

I wasn't happy with the first drawing that I had made of the Mk 4 for an illustration of the AJ Savage in my book Strike from the Sea, so I revisited the available material to see if I could improve it. Once again, I proved to myself that working solely from pictures leads to error. Fortunately, Bruce Radebaugh responded to my request for someone to measure the Mk 6 at Warner Robins, so I'm fairly confident that the size of the fins on my Mk 4 drawing is now about right and the body shape is close:

Bruce also took several pictures.

Although the fin looks flat on one side in the picture above, it's an optical illusion caused by the downward slant of the back half of the top of the fin. It is symmetrical.

The Mk 6 shape in the Warner Robins museum appears to be a mockup. Compare, for example, its boat tail:

With the one on the Mk 6 in the Air Force museum:

I can't say which is correct; the one in the Air Force museum is likely a training aid with details not representative of the real thing.

However, the Smithsonian Air and Space Museum reportedly was given a Mk 3 that was later determined to have not been fully disarmed, so anything's possible...

S2F One More Time

I decided to double check my assertion that the vertical tail did not change between the S2F-1/2 (S-2A/B) and the S2F-3 (S-2D). With respect to the size of the vertical tail, there's no difference shown on the Grumman factory drawings between the S2F-1/2 and the -3 or any mention in Grumman documents of a change. The mean aerodynamic chord is identical and the tip of the tail is at the same fuselage station of 157 inches. There is a difference in height between the top of the tail and the ground, but it can be accounted for by the -3 forward fuselage stretch between the main landing gear and the nose gear, which would result in a more nose down sit since the length of the nose gear did not change. Here is an overlay of the respective SAC side views:

 Note the difference in the "sit" in additional to the exact overlay of the vertical tails..

Since it's not unknown for draftsmen to be a bit lazy (note the inaccurate depiction of the aft end of the S2F-1 engine nacelle) and perhaps not to have bothered to update the S2F-3 SAC drawing for a change in the tail, I compared a couple of pictures taken from about the same distance and angle.

They look identical to me...

AJ Savage Notes

Updated 20 August 2022

This is a placeholder for a more detailed discussion of the North American AJ Savage program.*

North American won a Navy competition for a carrier-based atomic bomber in 1946. It was big enough to carry the projected 10,000-lb Mk 4 atomic bomb.The bomb bay was clearly sized in cross section by its 60-inch diameter. I have wondered why it was so much longer. My best guess is that in was sized in length by 2,000-lb bombs.

Note that the AJ-1 had the short canopy with the third crewman's seat on the left side of the fuselage across from the entry door. The AJ-1s originally had dihedral in the horizontal tail and a very large rudder. After a fatal crash in flight test, the stabilizer dihedral was eliminated, the rudder reduced in size, and the vertical fin increased in height and chord. That left the shorter canopy and the different nose landing gear door arrangement as the only external configuration differences between the AJ-1 and -2.

Both the AJ-1 and the AJ-2 had a small fairing for an antenna ahead of and just to the left of the nose gear door. When equipped with the ASB-1 bombing system, they also had a periscope fairing on the right side of the nose (the fairing was jettisoned before a bombing run):

Note that this illustration above depicts the two-piece AJ-2 nose landing gear door and the periscope dome after the fairing was dropped.

In response to a question about the tip tanks, they originally had a clear tip for left and right position lights. (Note that the wings are folded in this picture so the tanks are almost upside down...)

Subsequently, the inboard half of the tip was either painted (in some cases it looks like Corrogard) or otherwise made opaque.

Tip tank location (these are AJ-1s that have been retrofitted with the AJ-2 empennage):

*The best 1/72 kit by far is now the Roden AJ-1:  http://tailspintopics.blogspot.com/2022/08/roden-172-north-american-aj-1-savage.html

Although my CD produced for Nostalgic Plastic's sales of the Anigrand AJ-2 (now sold out as well as out of production) is no longer commercially available, for the time being this blog entry only contains material not covered in the CD or errors in the material that is included. For example, I didn't know at the time that the AJ-2 vertical fin (retrofitted on the AJ-1 along with the rest of the empennage changes) was 12 inches taller than the AJ-1's. However, the kit's vertical fin is the correct height. Since I provided the material on the CD to Nostalgic, I have also photographed the interior of the AJ-2 at the National Museum of Naval Aviation and therefore have identified some minor corrections to the kit's interior. See http://tailspintopics.blogspot.com/2013/04/aj-2-savage-cockpit.html.

I built an AJ-1 model from the Airmodel "kit," working on it intermittently for more than a decade.

 

The landing gear and propeller blades were provided by bits and pieces sold by Roberts Model once upon a time. A replacement canopy was vacuformed from a master created from the one in the Mach II AJ Savage kit, which is another huge time waster. The Mk 4 and cart shown above was from 12 Squared and is out of production. However, Spectre Resins produces a Mk 6 which is basically the same except that it had reinforcing ridges around its mid section. No cart, though.

The great Gordon Stevens (Rareplanes, among other brands) also produced a vacuform AJ kit which was very good for the type and could be built as either the AJ-2 or -2P. It included decals. However, it is long out of production and the AnigrandRoden kits are more accurate in a few areas like the propeller blades.

More later...

Model Kit Errors

Whenever a new kit is released, or even before if photos of test shots are available, errors and omission in shape or detail are immediately identified by the cognoscenti, often accompanied by expressions of wonderment and/or rude comments as to how the kit manufacturer could have gotten it wrong.

I spent a lot of time reviewing the Kinetic 1/48 S-2E and detailing the differences between the early and later Trackers and derivatives of the S-2. (See Here.) It was an airplane that I was very familiar with. I first sat in one in 1956.

I got to fly one in 1993, courtesy of Conair, who converted surplus S-2s to firebombers, including a version powered by P&W PT-6 turboprop engines, the Turbo Firecat.

So you can imagine my chagrin when Alan Weber recently asked me "I was wondering if you had any idea of when and why the big side front windows were enlarged on the S-2." and I had to say "Huh?" I had not noticed that.

It turns out that the S2F-1 (S-2A) and -2 (S-2C) and the TF-1 (C-1A) were originally delivered with cockpit side windows that did not extend beyond the contour of the fuselage immediately aft of the window:

It's not always easy to tell from photographs taken from the side that the window is bulged out. Based on this picture taken by Grumman, which is probably of a new airplane, the change appears to have occurred late in the production of the S2F-1, after the change to the gray/white color scheme.

Here is a closeup of the bulged window:

The new side window was retrofitted to the earlier airplanes, including the C-1, and was almost certainly standard on the S2F-3 (S-2D) production.

My guess is that its primary purpose was to provide the pilot and copilot with more elbow room as shown here on an S-2E (note the shadow of the bulge).

Other likely reasons for the bulge were better downward visibility and more clearance when using a camera to photograph foreign ships and submarines.

The WF-1 (E-1B) appears to have been produced with a bulged window. (Another E-1B feature common with the S-2D and subsequent production is that the control column was between the pilot and the instrument panel, whereas the C-1A COD version of the early S-2s had the control wheel extending out of the instrument panel.)

With respect to the Kinetic kit, Alan reports: "The more I work with them, the more it seems to me that the Kinetic windows are bulged greater than the early S2F-1 windows but are way less bulged than the later windows on the S2F-3 and other earlier models that operated later on. If a person wanted a more accurate window for a blue painted S2F-1 or -2, I would sand down the existing bulge and then polish the window out. On my tanker I reworked the sides of the fuselage behind the bulged windows and flattened them some (the fuselage sides). Then I took a hard look at the side windows and reshaped them to a somewhat closer curve than what Kinetic tried to do. On the later windows that have the pronounced bulge, the bulge extends the farthest out in the bottom half of the window. Kinetic's is centered and it gives the whole window an angled down appearance from the front which is weird looking. The windows now are still way too flat, but at least they are closer in shape than they were to start with. They did polish out nicely with not a whole lot of work."

One of the reasons that kit manufacturers don't get everything right is that it's not easy, particularly when the airplane configuration changes over time...

Scooter!

It took longer than we hoped, but Scooter! is in the last stages of the publishing process and should be available in the fall. This is the final cover:

It is being published by Crecy Publications in England (Home Page), distributed by Specialty Press (Home Page) in the United States and available for advance order from Amazon, HERE.

See HERE for an example illustration that I posted a year ago.

XF4U: the first to 400 MPH?

I just revised the entry on the XF4U's top speed as a result of a comment from Ron Lewis. Click HERE.

A Brief, F4U Corsair-oriented History of Navy Color Schemes and Markings

1 October 2022: Expanded the gray/white scheme discussion thanks to Tom Chee providing F4U/AU aircraft history card data.

One of the useful aspects of the Vought F4U Corsair's long career is that it can be used to illustrate three decades of U.S. Navy color schemes and markings. With the exception of two schemes, one arguably and the other definitely experimental, it lasted from the "yellow" wings of biplanes of the 1930s through to the change to gull gray and white in the mid 1950s.

n.b. Federal Standard 595 was first issued in March 1956 to provide a reference for "Colors Used in Government Procurement." The colors are identified by five-digit numbers but no names. Before that, there was Federal Specification TT-C-595 issued in January 1950 that identified colors by four-digit numbers. It was preceded by  an Army/Navy Aeronautics Bulletins that identified colors by three digit numbers and names. For some, this will be a gross oversimplification of aircraft color specification history but it's not my specialty.

The XF4U-1 flew for the first time on 29 May 1940. In conformance with the exterior color scheme at the time, metal surfaces were painted with aluminized lacquer and fabric surfaces were finished with alumininized dope except for the upper surface of the wings (including the ailerons), which was painted Orange Yellow so an airplane could be easily spotted if ditched in the ocean. (It would float because like most Navy airplanes of the era, it was equipped with flotation bags in the wing.)

Note that the national insignia is a blue circle with a white star encompassing a red circle and that the propeller tip has bands of blue, yellow, and red.

The first scheme that the F4U missed (the first production airplane did not fly until mid 1942 and the prototype doesn't appear to have been repainted) was an overall Light Gray scheme with white markings that marked the prewar change to low visibility in early 1941 as illustrated by this Grumman F4F Wildcat. It also added the national insignia to the sides of the fuselage and removed it from the upper right and lower left wings.

The single shade of gray approach was short-lived and replaced with a Blue Grey over Light Grey scheme for carrier-based airplanes on 20 August 1941. On 5 January 1942, the national insignia was reinstated on the upper right and lower left wings.

Note that the red centers have been removed from the national insignia as of 15 May 1942 in order to avoid confusion with the Japanese red rising-sun markings. (The original scheme, which did not appear on the first production Corsairs, also had red and white rudder stripes that somewhat detracted from the camouflage effect and were removed by the same directive.)

In January 1943, the U.S. Navy released a specification that replaced the simple Blue Gray over Light Gray camouflage scheme scheme with a complex one that employed counter-shading and counter-shadowing. Four colors were used: Semigloss Sea Blue on upper surfaces, non-specular Sea Blue on the wing leading edges, non-specular Intermediate Blue Sides, and non-specular Insignia White on the lower surfaces. Four-place national insignia were again decreed on 1 February 1943 in order to further minimize the likelihood of confusion with Japanese markings which were six place.

It took some time for the Navy to repaint delivered aircraft and probably a month or more for the contractors to develop and switch over to color schemes in accordance with the specification. For example, VF-17, which was working up for combat, was still flying Corsairs in two-tone gray scheme with six-place national insignia when carrier qualifying aboard Charger in March 1943.

However, by the time that Bunker Hill was available for shakedown of its air group in July 1943, VF-17 had F4U-1s that had been repainted by the Navy rework/repair facility at Norfolk, Virginia in their version of the new multi-color scheme. (Click HERE for background on it.)

(National Archives 80-G-205087 via Jim Sullivan)

The addition of white bars with a red surround of the national insignia was decreed on 28 June 1943. At least one VF-17 F4U-1 received the change in time to participate in the pilot qualifications and proficiency operations on Bunker Hill in July.

 In August, VF-17 reequipped with factory new (and factory painted) F4U-1As for their departure on Bunker Hill to the Pacific. In September 1943 the red surround was ordered to be replaced by blue, again due to reduce the potential for confusion with the Japanese markings. (It had already been deleted in the Pacific by an edict on 31 July 1943.) Note the difference in demarcation between the upper and side colors on the repainted airplanes above and this one.

This VF-17 Corsair, BuNo 17640, is marked with 1 and "Big Hog" for the squadron commander, Tom Blackburn, who is fourth from the left. (The dark patches behind the "1" are reportedly repairs of bullet holes made when one of his pilots mistook his airplane for a Japanese fighter.)

The complex multi-color scheme was eventually replaced by an overall gloss Sea Blue one by a directive issued on 26 June 1944.

(F4U-1D on Essex July 1945 via Jim Sullivan)

It was eventually suggested, probably by Grumman, that the Insignia Blue surround of the national insignia was redundant and should be eliminated on all-blue airplanes. It was reportedly deleted well before the official authorization to do so was issued in June 1946. A red bar was added in January 1947 to reinstate all the colors of the U.S. flag.

Although no Corsairs were involved in the experimental (and again short-lived) unpainted approach of the early 1950s (click HERE for a brief discussion), there was an F4U-1A created from various wrecked Corsairs by Service Squadron 11 of Marine Aircraft Group 11 based at Espiritu Santos (Vanuatu). However, it appears to be not unpainted but instead have been given an aluminum paint finish. "Sally" was marked on the cowling.

Photo provided by Jim Sullivan.

 Some Corsairs lasted long enough in service to be repainted light gull gray (36440) and white in accordance with the change introduced on 23 February 1955 following the failed "unpainted" exterior experiment. It was first introduced, to an extent, with some replacements for F4U-4s assigned to the Navy Reserve squadrons at Olathe, Kansas and Seattle, Washington. The last of these in overhaul retained their blue outboard wing panels and rudders but the fuselage and inboard wings were gray/white and the elevators, flaps, and ailerons were white. My guess is that the antiglare panel was nonspecular dark blue but it could have been black.

 

These were overhauled at San Diego and delivered in September/October 1955 to augment the remaining all-blue Corsairs in those units. My guess is that stripping and repainting the fabric-covered outer wing panels and rudder was deemed to be too much trouble given the likelihood of early retirement of these airplanes. The Olathe Corsairs, for example, went into storage at Litchfield Park in June/July 1956; at least two of the Seattle Corsairs left for Arizona in September 1956.

A handful of AU-1s received the complete paint scheme. At least three—BuNos 129378, 129403, and 129411—were overhauled at San Diego in 1955 and delivered to Aircraft Engineering Squadron-12 at Quantico, Virginia between March and June 1956 to provide training for ground-based close-air-support controllers. Again, this last service tour was over in little more than a year with one being ferried to NAS Norfolk, Virginia in June 1957 and two at the end of August, where all three were stricken in October 1957.

New soft-cover Corsair books well worth your consideration have been published recently: Jim Sullivan has completely rewritten and re-illustrated his F4U Corsair In Action published by  Squadron/Signal Publications. Is is a very good summary of the various versions with many previously unpublished photos.

Rafe Morrissey and Joe Hegedus have authored The Vought F4U Corsair: A Comprehensive Guide, SAM Publications. As you might guess from the title, it provides more detail (and more than twice as many pages) as Jim's monograph, including coverage of the kits and decals that had been produced at the book's publication.