Jetfire (VF-1S) & F-14D indoor glider conversions

[ReynoldsSlumber]

A flying Jetfire, and the type of plane that inspired it: I've been looking forward to this project for a while. I picked 1/96 scale to be in common with some other models that I'm making, as well as to keep the F-14 model from getting too big and the Jetfire model from getting too small. I thought it would be a good idea to keep the Jetfire model fairly small, with a 6" (15cm) wingspan, so that it would be resilient to crashes. The 1:1 scale comparison is fun, given the size difference between the two.


The main event, the Jetfire paper model, makes use of the Macross/Robotech VF-1 Valkyrie plan, which was designed by Shunichi Makino, recolored and added to by Getter1, and redrawn by Janx. I pulled together parts from several of their color schemes, chose the VF-1S-specific robot head, downscaled the parts to 1/96 (going by the fictional "real life" size of the vehicle), and further recolored them to match as closely as practicable the markings on the Transformers "Generation 1" Autobot Jetfire toy.* Then I made modifications for flight.

As you might imagine, it was tricky to get this tailless design to actually fly. It was unstable in pitch no matter how much nose weight I added. I was considering throwing in the towel and adding clear plastic horizontal stabilizers, but then I contacted one Mr. Kurosawa in Japan, on whose YouTube channel there is a video of friends of his making and flying radio-controlled VF-1 Valkyries. That video is very cool, and inspiring. They generously recommended the CG location that they had used plus a low-pitching moment airfoil for the wing, which was absolutely critical for making such a tailless plane work. Once I put an "S"-shaped airfoil into the outer portions of the Jetfire model's wings and re-trimmed it, it was off to the races. Mr. Kurosawa and his friends have my deep gratitude!

The companion F-14 paper model started with cafe's 1/200 upscale and Macross markings recolor of the Scissors & Planes 1/300 F-14 Tomcat plan. I further upscaled the plan to 1/96. At first I was going to build it in Macross colors as-is, but then, having looked at a bunch of F-14 pictures, and having noticed the strikingly similar white, red, and black color scheme of Grumman's prototype F-14D, I decided it would be more satisfying to build that. That way there could be a direct visual comparison between an airplane that actually existed and the fictional craft.

Since cafe's Macross F-14 plan is largely white, it was straightforward (if time-consuming) to recolor it again with the Grumman prototype scheme. If I were to do it again (which I might in the future), I would start with an S&P 1/100 plan or maybe the Eastern 1/100 plan and put in the work to recolor it, to get a better payoff out of the time investment of construction. Although the 1/300 S&P/cafe F-14 plan fared better with upscaling than most plans would, inaccuracies will start to show in any upscale this drastic. Also I found assembly of the center section to be squirrely.

I'll go into the construction of both models and their flying qualities in subsequent posts in this thread.

Shown here are the 1/96 paper models alongside the 1980s Transformers Jetfire toy, which is 1/60, and the recent Transformers Maverick F-14A toy, which is 1/82.


* The revolutionary toy design that would become the Macross VF-1 Valkyrie was the brainchild of Shoji Kawamori at Studio Nue. It was imported from Japan into the USA under Hasbro's Transformers brand. Much intellectual property controversy ensued.

[Vermin_King]

Very nice work. Care to let us in on the 'S-shaped airfoil'? I'm not seeing it (but I have old eyes and may not be looking at the correct place)

[ReynoldsSlumber]

Thanks VK! Sure thing, it isn't evident from the above overall pictures, but it can be seen edge-on. Note the upturned trailing edge, most prominent toward the wingtips because those are the furthest aft portions of the wings.


The fully contoured airfoil that the R/C VF-1 folks used can be seen in their video.


Basically, by directing the air coming off the trailing edge upward a little bit, it applies a nose-up torque, which counteracts the overall nose-down torque that any lifting wing generates.

You may know this already, but if you think about how airplanes fly, all an airplane wing is doing is turning air downward as it goes by. In other words, shoving air downward for lift is necessarily accompanied by a torque on the air. That torque on the air is reacted out as a nose-down torque on the plane. Then in turn the plane must use a smaller downward-pushing force on a longer moment arm behind the CG to keep its nose up.*


The "reflexed" airfoil does mean some reduction in lifting effectiveness compared to a regular airfoil. That's the price of not having a horizontal tail to balance out the torque instead.

At first I had tried to use a regular airfoil on the Jetfire model and apply nose-up torque just with the body flap. It didn't work. Whereas the low-pitching moment airfoil works beautifully. The plane is still very touchy in pitch attitude, as one might expect: if the nose is tilted too far up or down compared to its forward motion when thrown, it'll pitch out of control, because it doesn't have the strong stabilizing authority that a tail provides.

* Or an upward-pushing force ahead of the CG—a canard.

[ReynoldsSlumber]

Oops, pardon the fuzzy image, here's a better one.
Note that the latter two diagrams do not show the force of weight, which of course is balanced by the force of lift.

[ReynoldsSlumber]

For the 1/96 indoor glider conversion of the Shunichi Makino plan, to keep things lightweight I used 32 lb bond/118 gsm Domtar Lynx Digital paper for the nose, center body, and wing top surfaces, with 24 lb bond/89 gsm Domtar Cougar Digital paper used for the rest. As I've been finding, these printer papers just aren't sturdy enough for my tastes in terms of holding up to gluing and crashes. See the F-14 post below for a much better paper.

Modifications for aesthetics:

• Jetfire recolor: I had some fun with this. It's not quite exact to the Jetfire toy, but then this paper plan isn't shaped exactly the same either, I guess more Macross cartoon-accurate. Those calves be thicc. I left the Macross emblem on the wing because some early Transformers Jetfire toys left it on there too.
• Vellum canopy
• Added detail: Added strake features on the topside.

Modifications for flight:

• Foam nose: This saw heavy use during the arduous flight test phase, when I was figuring out balance and trim.
• Nose weight: The model was short on nose weight when I closed it up. How could more be added after the fact? I pried up one of the nose pods, poked a small hole, formed a piece of wire of the correct weight into a loose spiral, twisted it in, and used a syringe to squirt some Aleene's Tacky Glue in after it. Then I left it to dry with the nose pointed down. Worked great!
  
• "Flat" airfoiled wings: I did away with the wing thickness and instead glued the top and bottom layers together, for better resilience against crashes and so that the wings could be shaped at will. As mentioned above, this tailless plane requires an "S"-shaped airfoil, with more pronounced trailing edge "reflex" toward the wingtips.
• Omitted engine bulkheads: Air flows freely through the "legs."
• Clear plastic finger grip
• Body flap bend: This acts as the elevator control surface.

One assembly note is that it was tricky to figure out where to position the "thighs" and "calves" fore-aft.


Also indeterminate was the angle of the calves. I let them droop just a little bit, though they still pressed up against the aft edge of the center body.

* What in Transformers-speak is known as "alternate mode," "vehicle mode," or just "jet mode" is the same as the Macross/Robotech VF-1S Valkyrie's "fighter mode."

[ReynoldsSlumber]

The all-up weight is just over 5 g. Due the small wing size, the wing loading is the highest of any of my models so far at 14 Pa. So, the plane flies like a cruise missile! That said, it's not quite the dart that the A-4 Skyhawk that I built earlier is, I think because of the more slender wings on the Jetfire model, which are set at the 32° sweep forward position. As mentioned above, you have to throw it straight ahead both in terms of direction of motion and nose attitude, something that I'm only able to accomplish about half the time. When you do, though, it glides laser-straight.


The robot head is a fun part of the design. I left the visor Macross VF-1S green rather than convert it to Jetfire red. The protruding finger grip (hidden here by the stand) protects the head's antennae/lasers from damage when the plane lands on the floor.


Here's the 1/96 paper model with the 1/60 toy:


Please pardon the fuzziness of some of the pictures. While some of it is due to short depth of field, the software on my computer is doing something screwy with exporting from raw camera file format.

[ReynoldsSlumber]

For this 1/96 upscale from the 1/200 cafe recolor of the 1/300 original S&P plan, I used 80 lb text/118 gsm Canson XL Pen and Ink paper. This stuff is my new favorite: reasonably white, smooth enough that it prints pretty much without feathering, and much more durable than the equivalent Domtar Lynx printer paper, with about the same stiffness.

Modifications for aesthetics:

• Recolor: The tricky part was unskewing the "Super TOMCAT" lettering on the tails from photos found online.
• Vellum canopy
• Engine air intake boundary layer gap: I tried to add the ramp feature and re-shape it to better match the odd shape on the prototype, only partially successfully. Even most 1/100 plans don't get this detail right though.
• Added details: Added the chin infrared pods, tailhook, and topside antennas, vents, and strakes.

Modifications for flight:

• Foam nose
• Nose weight
• Omitted engine bulkheads
• Undercambered wing airfoil

The wings are mid-sweep at 32°, same angle as on the Jetfire model for visual comparison.

Again the fore-aft position of the jet engine tube portions of the body was tricky. They ended up a little aft of where they should be, but even if they moved forward a couple millimeters, the markings and especially the air intakes still wouldn't line up. Admittedly I'm asking a lot of this much of an upscale.

[ReynoldsSlumber]

The paper model with 0.7 g of nose weight totals 7.4 g. It flies like a Cadillac: ultra-stable, smooth, and forgiving of throwing variances.

Gotta have a crash barrier photo for this Navy jet:


As you can see, the engine intake leading edges often get roughed up. Also, when it lands on the floor rather than in the net, it literally takes it on the chin: I've had to re-attach the infrared pods twice so far.

Here the Transformers Maverick F-14A toy is standing in for the Grumman prototype F-14D.


I guess one could squint and call the Maverick toy's arms under the belly a TARPS reconnaissance pod? Funny enough, that's less than the usual amount of non-scale junk ("robot kibble") for the underside of an aircraft Transformer.

[ReynoldsSlumber]

Here are some bonus images, first comparing the bellies of all of the planes:


Next an obligatory "GERWALK mode" picture, thanks to Jetfire's Macross origins:


If you'll indulge me, here's an improved version of the forces and moments diagrams that I think makes the idea clearer:


Finally, give it up for the runway models: