Minicraft's Skyrocket

Building the
Grumman XF5F-1
"Skyrocket"

By Tom Cleaver

The first time I ever saw a photograph of this airplane, I thought it was totally strange. There was never, before or since, another twin engine airplane with the layout this one had. I thought it was so strange that it was totally cool, and always wanted to have one. Thanks to Minicraft Models, we can all have one of these now, in state-of-the-art quality.

The Airplane

In February 1937, the U.S. Navy's Bureau of Aeronautics reviewed the state of carrier aviation:

"... the most backward development is that of the VF (naval fighter). It is generally conceded that the new engines of horsepower higher than the 1830 (Pratt & Whitney Twin Wasp) will not give any great increase in speed over the XF4F. This means it will be necessary to go into a two-engine, single-seat fighter design."

This was set in motion a year later, when BuAer put out Specification SD112-14, soliciting bids for the twin engine fighter from thirteen companies, including Brewster, Grumman, Seversky and Lockheed. Grumman responded with is Model G-34, or XF5F-1, in April 1938.

The XF5F's design engineer, Dick Hutton, stated many years later that, "two-engine safety was always a desirable goal, but resulted in a larger aircraft, spanwise, for parking on the carrier. By eliminating the width of the fuselage, the engines could be located close together. By locating the guns on the centerline, the boresight problem could be eliminated. Landing visibility from the cockpit could be improved. Good space coverage of the wing by the slipstream would improve the takeoff. Engines close together, along with the twin vertical tails in the slipstream, made single-engine operation easier. Engines used were about the lowest power-to-weight ratio, and by having two, total power would give good performance."

In their wind tunnel testing, Grumman determined that "the flow over the upper surface on the wing between the fuselage and the nacelles was critical." Thus was born the strange layout in which the nose of the airplane actually stopped almost a foot behind the leading edge of the wing. This arrangement demonstrated good stalling characteristics and low landing speeds, essential for carrier operation. Their wind tunnel tests had previously determined that a longer nose resulted in a premature stall with a much higher landing speed, a discovery thatwas borne out when the airplanewas later modified with a longer nose in the quest for a higher top speed.

During flight tests in 1940, company test pilot Connie Converse reported that, "the flying characteristics of the XF5F-1 are good overall. The counter-rotating propellers virtually eliminate torque on takeoff, and single-engine performance is good. All acrobatics were easily performed."

In the summer of 1941, BuAer brought together six top Navy fleet pilots and conducted a competitive series of test flights between the British Spitfire and Hurricane, the USAAC P-40 and P-39, and the Navy's XFL-1 Airabonita, XF4U-1, F4F-3, F2A-2 and XF5F-1. Following an hours' familiarization in a plane, the pilot would fly a series of maneuvers, then move on to the next aircraft, until all aircraft had been flown by all pilots. LCDR John Crommelin, BuAer operations officer, recalled in 1985 that, "testing the XF5F-1 against the XF4U on climb to 10,000 feet, I pulled away from the Corsair so fast I thought he was having engine trouble." Crommelin recalled that the analysis of all the data favored the XF5F-1 over all the others, with the Spitfire a distant second.

Obviously with the XF5F-1, handsome is as handsome does. Unfortunately, the state of aviation development was such that the structural design of the airplane would have had to be highly modified for wartime production. Also, the R-2800 which produced 2,000 horsepower, had not even been a speck on the horizon when BuAer was looking for a way to increase fighter power in 1938. However, the knowledge gained with the XF5F-1, coupled with two R-2800s, would in two years produce the F7F Tigercat, probably the most powerful piston engine fighter ever flown.

The Kit

Minicraft hired the same mold-maker who did the Tamiya Beaufighter to do their XF5F-1, and then produced it on copper molds. The result is a very well-produced kit. There are two large sprues of parts in standard medium-grey plastic, with a clear sprue for the two-part cockpit canopy and the wingtiop navigation lights. The decal sheet provides the simple markings the XF5F-1 carried in 1940 and early 1941.

Assembly

This is another one of those kits where taking the truly radical step of actually reading the instructions will help the modeler avoid problems during construction. I also urge that you buy and read the Ginter book on the Skyrocket reviewed elsewhere in this issue of Internet Modeler. Doing so will definitely contribute to "making modeling fun again."

To begin with, it should be noted that, as provided in the box, the modeler can really only create the XF5F-1 in its first modified configuration, i.e., without armament, lacking the wing fillets, and using the small rudders. A quick read of the Ginter book reveals that the first modification was to change to wheel well doors to the large forward-opening door with two small side-openingrear doors provided here in the kit. The second modification involved changing the exhaust system from that provided here in the kit to introduce ejector exhausts along the edge of the engine cowling; this is not a difficult conversion for those modelers with a bit of kit-hacking experience, but it would have to be done before adding the third modification, the wing fillets the kit provides, and the new balanced rudders. Thus, while it appears there are several possibilities here for differing configurations, there is really only one. Fortunately for those modelers who want to do Blackhawk airplanes, this is the configuration of those airplanes as drawn in the comic books, with the addition of the four machine guns. However, died-in-the-wool aviation historians are stuck with the original unarmed version.

I painted the interior of the cockpit, and the seat and control stick with SnJ aluminum, as well as the interior of the engine nacelles - both the wheel wells and inside the engine cowling, then set these aside to dry. I also filled the nose cap with CA glue from the inside, hitting it with accelerator, so that I would be able to fill in the holes for the machine guns later.

While all this was drying, I assembled the wing and the tail sub assemblies. One thing to note here is that there is a very small visual difference between the two different kinds of rudders. so be sure you are using the proper narrow-chord rudders by checking the correct parts number in the instructions.

I also at this time painted the instrument panel black, and, when it was dry, added instrument decals from a generic ProModeler sheet.

From my experience, I will suggest that you should build the nacelles up completely before attaching them to the wing. This is shown differently in the instructions, but if you do this you will not use any putty on them. Per the kit instructions, set in the landing gear before gluing the halves of the lower nacelle sections together. Then set in the pre-painted engines, and then attach the upper section of the cowling and nacelle. These are all a bit fiddly in their fit, so if you do this without waiting for everything to set up, you can move things around a bit to insure smooth joins. Taking time and exercising care here will mean all you have to do is smooth the join lines once the sub assembly is set up.

When attaching the nacelles to the wing, be sure to test fit. There are only four very small locating pins on the lower side of the wing to guide proper attachment, and I can assure you it is easy to miss them if you are not careful. Check it, be sure it's properly located, then glue the nacelle to the wing.

While this sub-assembly is drying, glue the fuselage halves together and attach the tail sub-assembly. Then attach the gun bay doors in the closed position. I find that running the glue from the inside will leave a nice panel line on the exterior.

The nose is hard to get sanded smooth, but with care and repeating a light puttying as necessary to get a smooth exterior surface, it comes out looking nice. I suggest you polish this to get a smooth exterior surface, because under a thin coat of aluminum paint any scratches will show up plainly. Attach the nose to the fuselage the same way you attached the gun bay doors, i.e., gluing from the inside, and set the fuselage aside to dry and set up.

The cockpit is simple, so merely place the instrument panel, control stick and seat where indiated on the upper surface of the wing. . I put seat belts but not shoulder harness on the seat. Because this cockpit is not well detailed, I chose to have the canopy closed, after dipping the parts in future. To me, the airplane looks better with the canopy closed than it does with the canopy open. If I do another with a resin cockpit, I will vacuform the canopy so it can remain closed while allowing viewers to see the cockpit. Out of the box, however, the slight distortion of the canopy is a good way of hiding the lack of detail inside

I joined the two major sub assemblies - wing and fuselage - together and set things aside to dry and set up overnight.

Painting

The Skyrocket was painted overall with aluminum lacquer, except for the upper surface of the wing, which was Navy Chrome Yellow. This is actually an orange-yellow; I have found that Gunze Sanyo's H-24 "Orange Yellow" is just about perfect, and have used it on all my Navy "Golden Wings" models. After airbrushing the upper surface and allowing it to dry thoroughly, I masked off the dmarcations and covered the rest of the area with drafting tape (nice and low-tack, guaranteed not to pull off the paint below when removed) and sprayed the rest of the model with SnJ aluminum. Once that was dry, I took some of the SnJ aluminum powder and applied it to the fabric-covered control surfaces. I did not buff these, but blew off the excess powder; this created a different color tone, which set off the fabric effect. I applied the powder to the propellers also, but here I polished the daylights out of them, since in its original configuration the Skyrocket had polished metal props. I also polished the pitot tube before attaching it.

Decals

Since this is a pre-production test-shot, I did not have the decal sheet available. I used national markings from the Aeromaster US Navy Pre-War sheet, and took the serial number and designator from a sheet of small letters and numbers i nthedecal dungeon. This was laborious, and the rest of you will be fortunate to have the decal sheet, which will save you time.

Final Details

I set the canopy in place and used white glue to attach the two parts to the fuselage. I used nylon repair thread for the antennas. When attaching the propellers be certain to put the right propeller on the right engine, since these are contra-rotating props. And the model was complete.

Overall Assessment

The model went together as it looked it would - like a Tamigawa kit. I wish some more effort had been put into making interior cockpit wall panels, which would have provided all the cockpit detail a modeler would need. Mike West at Lone Star Models - whose multi-media kit was previously the only 1/48 Skyrocket available - has created a resin cockpit interior that fits this kit, so the modeler who has to have super detail is well-served already. As I have said before, this was an airplane I never expected to see produced by a mainstream manufacturer as an injection-molded kit. I like it a lot.

The Blackhawk Squadron

Anyone interested in the Blackhawk Squadron should have "The Unofficial Blackhawk Comics Home Page," bookmarked. Everything you ever wanted to know about the band of freedom fighters is there, along with a nice page of color profiles of Blackhawk F5Fs over the years.

As I understand it, DC Comics will not allow Minicraft to obtain a license to do the Blackhawk Squadron markings. However, for anyone with an ALPS printer - or a friend who has one - obtaining these markings should not be difficult, and as long as friends are passing them to friends without money changing hands, the DC Comics people can go take a proverbial leap at the proverbial rolling donut hole, if you know what I mean. For me, I think that September 1945 scheme with the blue fuselage and engine nacelles, with red wing and tail, looks just great. The nice thing here is, the dead-serious warbird historians and the fun-loving fantasy folks can both have a ball with this model.

Get a bunch of them and have fun!!