Tailhook Topics Drafts

Thursday, March 1, 2018

FJ-1 Tip Tanks - 1948 Bendix "Race"

Once upon a time, there were big-deal airshows with military participation, including "races". At some point the services were prohibited from competing with each other directly so they took turns year-by-year for the major events. The 1948 Bendix race was to be a Navy year, showcasing the new North American FJ-1 Fury assigned to VF-51. Takeoff was from Long Beach, California with the finish line at Cleveland, Ohio about 2,040 statute miles away.

When I wrote about this event in U.S. Naval Air Superiority, the range and speed numbers originally didn't add up. The FJ-1 cruising at 40,000 feet had a range of about 2,300 miles but almost certainly at a long-range cruise speed of only 350 mph versus the winning speed of 490 mph. However, looking at pictures of the airplanes involved, they clearly had different tip tanks than standard.

They were longer relative to their diameter, didn't have the position light in the tip and also had a rounded aft end and a fore-and-aft horizontal flange. The nose and tail resembled those on a 150-gallon external tank of the time with a longer, bulged center section and the FJ-1 tip tank fins added.

According to a Naval Aviation News article, these bespoke tanks could carry 290 gallons of fuel each versus the standard FJ-1 tip tank capacity of 170 gallons. These enabled the Bendix racers to fly much faster and still get to Cleveland. Just barely. The squadron commander, Bob Elder, flamed out 50 miles away from Cleveland at something over 40,000 feet and glided there for a dead-stick landing. The winner flamed out while taxiing in. One pilot climbed to 50,000 to stretch his fuel (the FJ-1 cockpit was not pressurized), became hypoxic and lost, finally crash landing in a field.

Now misreported most places on the interweb, a California Air National Guard pilot, not officially competing but just going to Cleveland in a P-80C nonstop with nonstandard tip tanks, beat the Navy's best time by a minute or so.

The question has come up as to the size of these non-standard tanks. It can't be directly scaled from the picture above because of the camera lenses distortion of length versus diameter. Knowing the volume proved to be less useful than I hoped. It turns out that the standard 150-gallon tank must have fore and aft voids. Stretching it to add a 140-gallon cylinder results in a tank that looks too long relative to the diameter. I also tried to correct the picture of the tank using the fore and aft sections of the 150-gallon tank, which looks better with respect to length but means the voids had to be eliminated; if retained, the addition only came to about 48 gallons.

The new tank center section did have to accommodate the tip mounting of the FJ-1's as opposed to being slung under a wing on a pylon so it may be that the fore and aft sections were modified to eliminate voids as part of this reconfiguration. This is my best guess at the size and shape:

Tuesday, February 27, 2018

FJ-1 Fury Canopy

Initial open/close mechanism:

Later open/close mechanism:

Wednesday, January 10, 2018

The Grumman XF9F-9, Too Little, Too Soon

After the debacle of the XF10F Jaguar and the hasty conversion of the straight-wing F9F Panther to the swept-wing F9F Cougar, Grumman elected to propose the jet-powered equivalent of their F8F Bearcat to the Navy, encouraged to do so by BuAer's Fighter Class Desk. It was to be light, simple, inexpensive, maneuverable, and capable of near sonic speed in level flight without an afterburner. The engine selected was the Wright J65, a license-built British Armstrong Siddeley Sapphire that had also been selected to power the Navy's FJ-3 Fury and A4D Skyhawk. At the last moment, BuAer decided to add an afterburner in this instance.

Wright experienced difficulty in qualifying the afterburner so the first XF9F-9 made its first flight without one (it was subsequently redesignated F11F Tiger, since it bore no resemblance to its F9F Cougar forebear even in a dim light).

Like the Bearcat, it was relatively small and would have been wrapped snugly around its engine except that it was snugly wrapped with fuel tanks, not enough as it turned out.

Unfortunately, the F11F not only proved to be too small, lacking endurance, it was too soon, since the General Electric J79 then in development subsequently exceeded expectations as the afterburning Wright J65 was falling short of them. When evaluated with the J79, the F11F not only had terrific performance, it had somewhat better endurance. By then however, the Vought F8U Crusader had enough of a head start that the little Tiger became an also-ran.

A model of the first-flight prototype would be a relatively straight-forward conversion of a production F11F since most of the airframe was unchanged.
Note that the nose is even shorter than the original production F11F's but the wings, horizontal tail, and much of the fuselage is the same (the extreme aft fuselage has to be reshaped and shortened). Deletions include the wing fillet on the second production lot airplanes and the splitter plate ahead of the inlet (the inlet was offset from the fuselage, however). The vertical tail is smaller. Some other notable differences are the large pitot on the right side of the forward fuselage (it was subsequently moved to the vertical fin), the nose-landing-gear doors, the size of the wing fence, and the leading edge slat arrangement.

Wednesday, October 25, 2017

FJ-2/3 Nose Landing Gear

Warning: Probably more than you want to know!

First an overview of the nose landing gear from the side.
Note that the shock strut is angled slightly forward and the yoke is mounted in front side of it. The anti-torque scissors on the right side of the strut is angled somewhat aft. The Sword assembly illustration would have you mount the yoke on the bottom of the strut and have the scissors angle forward. Paul Boyer also noted that it would have you put the shimmy damper and the anti-torque scissors on the wrong sides.

This is a closeup of the interface between the strut and the yoke;
Craig Kaston photo

Note that there is a shimmy damper mounted on the left side of cylinder that the yoke is mounted under. It turns out that the yoke is free to rotate within that cylinder since it is basically a sleeve ( there is no nose-gear steering; the pilot steered during taxi and the first part of takeoff and the last part of landing with the brakes).
The shimmy damper does not turn with the nose wheel; it is connected to the yoke where it protrudes at the top of cylinder. What confused me at first looking at pictures of FJs in museums was that lever extending aft on the left side of the yoke. At first I assumed that the museum had left something off but I finally realized that the shiny cylinder at the end of that lever contacted some kind of "ramp" in the nose-wheel well as it was going into the well that turned the wheel 90 degrees so it lay flat under the inlet duct. (On the F-86 that was done with an actuator.) Presumably the shimmy damper provides a centering function when the landing gear is extended.

The line coming down from the wheel well to the bottom of the shock strut pressurizes it to raise the nose for a catapult takeoff. However, the actual routing, at least early on, is along the scissors as shown on this early production (a few were blue) FJ-2:

Here is a comparison of the "normal" strut extension and pressurized for a catapult launch:
However, the strut might be somewhat or fully extended at other times for various reasons.

The Sword nose landing gear strut appears to be too long. I assembled the three big pieces. I drilled an .080 hole in the cylinder in front of the strut and in the yoke to pin them together with a piece of wire since I think simply gluing them won't be sturdy enough.
It looks like I'll need to cut off that thicker section at the top of the strut and "flatten" the tire a bit to get closer to the right "sit". The yoke is also too long but shortening it looks like to much work.

Wednesday, October 18, 2017

Sword FJ-2 Preliminary

The accuracy of the planform of the new Sword 1/72 FJ-2 has come into question. This was my assessment, using a photo of the Sword FJ-2 wing provided by MVW (Martin) compared to my layout of the FJ-2 wing planform using NAA data for root and tip chords, wing span, and wing sweep at 25% chord. I had some difficulty in establishing the exact location of the trailing edge due to shadow.

In summary, the FJ-2 kit's wing appears to have a little too much wing span and about the right wing sweep depending on the exact location of the trailing edge, which needs some cleanup (and maybe thinning) anyway. Both the root and tip chords look a little too big but not as much as the 6-3's wing. All in all, I'd say its well within my tolerance for error.

Unfortunately, a review of the fuselage picture published by Sabrejet on Britmodeller  indicates a more significant problem. It is clearly somewhat long by 6 to 8 mm (1/4 inch). In checking the comment of another modeler who has the FJ-2 kit that the fuselage was actually slightly undersized relative to the published length, I noticed that the FJ-2 overall length including the extension of the stabilators aft of fuselage of 37' 7" is identical to the 1/72nd length of the kit fuselage from the tip of the nose to the tip of the fairing above the tail pipe. That may be the cause of the fuselage length error.

21 October Update: I now have all three kits in hand and they are lovely to behold.

The surfaces and panel lines are engraved and petite. All the detail parts such as the pitot look as close to scale as you can probably do in 1/72. I haven't checked the fit except for fuselage halves and the wings but so far, so good. The canopy is injection molded in two pieces and clear.

The FJ-2 fuselage and wing are not the same, correctly, as the FJ-3's. The FJ-3s have a slightly deeper inlet and forward lower fuselage and a different air scoop on the upper fuselage aft of the break. The FJ-3s have a cambered leading-edge wing that has a representation of the 6-3 planform change that differentiates it from the -2 and blue FJ-3s slatted wing, which were similar to the F-86E's and early F's. (Remarkably, the FJ-3 wings have three of the four barricade snaggers—these are teeny things in 1/72—on the leading edge of each wing, missing only the most outboard one.) They also have alternative rudders and horizontal stabilizers with the external ribbing on the trailing edge whereas the FJ-2 kit does not.

Both the FJ-2 and FJ-3 fuselages are a little less 1/4" too long. Theoretically you could take 1/8" out of the aft fuselage (but you can't do it at the break as I had hoped) and about 1/8" off the inlet. I'm for certain going to forget sectioning the aft fuselage. However, in my opinion, the downward curve in the top of the fuselage forward of the windscreen is incorrect (it needs to curve down more) and the bottom of the intake curves a bit forward and shouldn't.
There appears to be enough plastic in both places to get closer to what I think is correct. See http://tailspintopics.blogspot.com/2017/10/sword-172-north-american-fj-23-furies.html for one approach.

The only difference besides decals between the -3 and the -3M kits is that the latter has two Sidewinders and the requisite pylons. Both have the inflight refueling probe.

Getting enough weight in the nose to keep it from tail sitting might be interesting. A little scraping of the upper fuselage at the forward end of the windscreen appears to be required for a good fit. My guess is that putting the nose gear together (seven pieces!) might need to be altered from the instructions with respect to the location of the nose-wheel yoke, which may be too deep otherwise by a teeny bit. I'm pretty sure that the top of the nose gear door should be inside the forward end of the wheel well when it was extended.
More later...

Tuesday, October 17, 2017

VA-72 A4D-2

In response to a request...