A7K Jinpu-Kai?

sequoiaranger · July 27, 2008, 04:06:07 PM

...I now present a close equivalent to the "Jinpu-kai" I am in the process of whiffing.

**My** "Jinpu-Kai" drawing is below an actual "Jinpu" drawing--notice the enlarged cowl, supercharger exhaust pipes on the bottom, the additional fairing under the fuselage, and the tail moved back with a tailhook. My model Jinpu-kai doesn't look quite so "fat" in the nose as the drawing, but I doctored the photo/drawing with the additions I made to the model. Close enough to get the idea.

EDIT Aug 26: Added "new" drawing based on new "A8K" image provided by Jon C.

sequoiaranger · August 28, 2008, 09:44:34 AM

My conceptualized carrier-borne "Jinpu-Kai" would have the only Japanese fighter wings that folded more than the very tips (e.g., early-model Zeroes). On the real thing, such folding and associated mechanisms would merely be designed in. On a model, difficulties arise. I have made folding wings on one previous model (MC 605 "Vendetta"), so at least I know what I am up against. I have hemmed and hawed over whether to "bother" with folding wings for the Jinpu-Kai, because I KNOW how much work is involved, but one has to "stretch" to be creative, and I am determined to have my Jinpu-Kai's wings fold (if nothing else than for pictures or diorama effects).

Some models, especially Japanese-manufactured ones from the 60's, had wing-folding mechanisms built into them, but they were too crude and obvious—more "toy"-like than "accurate-miniature"--or too delicate (being plastic). Something strong and subtle would be better. Like what?

I have some tiny "doll-house door hinges" (available from dollhouse supply catalogs, or, rarely, craft and hobby shops) in 1/12 scale, that will work. In the illustration, you can see that they are three-part, and REALLY TINY to manipulate, even with a tweezers. They are metal, so are sturdy enough for the task.

There are several "problems" with these hinges (besides being ridiculously tiny—see illustration). One is that there is a "tube" that sticks up from the plane of the hinge (if put one way). It's small, to be sure, but for "realism", that tube has to be sunken in and not sticking up on the wing of the model aircraft wing. With the "sunken" configuration, the hinge will STOP at 90 degrees (it will fold flat onto itself in the other configuration). The dihedral of the wings of the base kit of the Vendetta (Bf-110) was very slight, so the wing angle to the ground, when folded, was VERY close to 90 degrees. I found out the hard way with my "Vendetta" that once the wing is folded up, that at 90 degrees it is precariously balanced, and will flop back down seemingly at random. The flop is very hard on the structure of the model, and...well I just don't want that.

If you look at pictures of real folding-wing aircraft, the folding part invariably goes well past 90 degrees, even nearly flopping onto the canopy (a "Kate" is a good example). Ideally, my Jinpu-Kai's folding wings will fold to about 110-120 degrees (angle "C" in the drawing). Luckily the dihedral of the base kit of the Jinpu-Kai (Shiden-Kai) has marked dihedral to start with, so I MIGHT be able to get away with a simple 90-degree fold (angle "B" in the drawing). Ideally, I will find a way to angle the 90-degree bend so that the wing itself folds about 110 degrees. My plan is to SLANT the hinge inside the wing a bit (see drawing). Depending on the plastic thickness of the model's wing, I may have to "build" a slanted piece of plastic for the hinge to adhere to.

Another is that the hinge is flat, and a wing is curved. To work well, such a hinge should be on the flattest part of the wing, but that is NOT where the wing needs to fold—it needs to fold at the "top" of the airfoil. So "sunken" is the way to go, as you can "sink" the hinge into the wing a bit and fill in with putty to restore the airfoil.

Next comes the dilemma of the folding wing part—do I put the hinge on the outside of the wing or the inside? If I put the hinge of the folding part of the wing on the inside, I may be able to engineer the upper edge of the folding wing to rest against the non-folding part at the correct angle. Aesthetically, too, the inside would be better, but the thickness of the wing might make the hinge inoperable. I may have to SLANT that part of the hinge as well.

JEEZ! I didn't know that such micro-engineering would crop up in modeling, but I believe it will make for an interesting effect once done. Naturally, I will try it on a "dummy" wing first to see if the concept works. The green wing on the model in the photo is a "normal" Shiden-Kai wing, test-fitted to my Jinpu-Kai fuselage, and will be my "dummy"—the Ki-36 "Ida" wingtip that will be used on my finished model is a grey color, and a little longer. Of course I will photograph the results when done. WISH ME LUCK!

sequoiaranger · August 28, 2008, 04:45:11 PM

OK--Next step.

The slanted "shelves" in the wing for making the more-than-90-degree hinged wing-fold are in place in the test wings!

The hinge pin is too long, though, and has nothing to stop it from working its way out unless I make an "L" bend in it and clip it off.

I know that the Super-Gluing the hinge to the wing will be the hardest part--trying to get the glue into the right place without getting into the actual hinge. I may have to add more wiggle room in the wing for the tube of the hinge so there is no gap in the wing (and it will sag downward). Tough to do on such a small scale, but I think the "reward" will justify the effort. Good thing I have an additional kit for the test run!

Next installment might be a while--honeydo's, meetings, and other chores of living (my how they get in the way of "proper" modeling!).

Weaver · August 29, 2008, 01:27:08 AM

Just a thought: could you not make the hinge go over 90 deg in the "flat" position by filing the slots between the hinge tubes deeper?

sequoiaranger · August 29, 2008, 09:54:25 AM

I hope the illustration below will apply to your thought. That is, by "deepening" the slots, it makes the rotation of the hinge take longer before stopping due to the physical restraints of the hinge itself. I get it. It might very well work.

The hang-up might be the minuscule size of the hinge itself. The five tongues and slots of the hinge are only one millimeter wide (the whole hinge is 5 mm), and I don't know if I have anything small enough to get in to work on it. I have a cut-off wheel on a Moto-tool that MIGHT be thin enough to get into the slots.

It shows you're thinking, and I appreciate it. ;-)

frank2056 · August 29, 2008, 12:38:56 PM

Craig,
I had to make use of tiny plastic hinges for a device I made at my old job. I was very careful with the gluing yet I managed to get some superglue on one hinge pin, and capillary action (which never seems to work for me when I need it) sucked it into the tube and froze the hinge. If you can, leave the pin insertion for last, and maybe use a plastic pin instead. Or just be extra super careful and use as little CA as possible. Or do what I ended up doing - using 30 minute epoxy.

Frank

sequoiaranger · August 29, 2008, 03:35:20 PM

Good Idea.

Yeah, I have a tough task ahead of me with the Super Glue. Though gluing the separate halves of the hinge first and then putting the pin in later would be nice, the pin has to have some sort of cap on the other end to keep the pin from slipping out. My original plan was to bend the pin over (which I can't do afterwards) and put the hinge in whole, one side at a time.

I may just glue the separate halves, insert the pin and then put a dab of white glue on the end to stop travel (shouldn't be too much travel anyhoo, since the hinge won't be used much and there is a bit of friction anyway) and not over-engineer it.

Come to think of it, I have some strong RC-56 (?) white glue that MIGHT be the ticket all-around, except for its relatively long drying time. I might chance it, and then if the wing hinges fall off from use, I will switch to Super Glue. I'm not too worried about static display, but transporting it, even in a car, might jar it or vibrate it loose if the glue bond isn't strong enough. I may overlay the hinge with plastic sheet or melted plastic that can bond around the perimeter, and maintain a "slot" that, if the bond breaks, I can replace it in exactly the same spot in a jiffy. Hmmm.

I appreciate the suggestions, guys! Maybe three heads ARE better than one, though they would look funny poking out of the same suit jacket. Remember that three-headed guy in the "Hitchhiker's Guide to the Galaxy"?

frank2056 · August 29, 2008, 06:16:03 PM

Why not put a blob of hot glue to hold the hinges in place? It'll probably be strong enough.

Brian da Basher · August 30, 2008, 07:36:16 AM

I'd use Gator Glue. It takes a few minutes to set and is water-soluable. Once it's set, the bond is very strong. I hear it's the best adhesive for PE so it should be just the ticket on those hinges!

Brian da Basher

sequoiaranger · August 30, 2008, 08:50:07 AM

>Why not put a blob of hot glue to hold the hinges in place? It'll probably be strong enough.<

Well, I think "HOT" wouldn't be good for the thin membrane of plastic I have for the hinge to adhere to--probably would warp it. If the plastic were thicker that might be the ticket.

>I hear it's (Gator Glue) the best adhesive for PE so it should be just the ticket on those hinges!<

What's "PE"?

I think I will get some "gator glue" anyway. Sounds like it has lots of household applications.

Thanks for the tips! I think the best way to go is to get something to tack-hold the hinges in place that won't solidify the hinge motion, then slather some chemically-dissolved plastic over the top of them (actually the inside of the wing) to set the hinges "permanently" in place.

Daryl J. · August 30, 2008, 09:25:30 AM

The proportions are just right too!

Daryl J.

Brian da Basher · August 30, 2008, 11:42:43 AM

Quote from: sequoiaranger on August 30, 2008, 08:50:07 AM

<snip>

What's "PE"?

I think I will get some "gator glue" anyway. Sounds like it has lots of household applications.

<snip>

PE is shorthand for Photo Etch. Gator Glue was made for attaching photo-etched parts. I use it for attaching canopies and smaller parts like gun barrels, antennas and exhausts.

Brian da Basher

sequoiaranger · August 31, 2008, 09:07:49 AM

Hey Brian de Basher!

Thinking I was taking your advice, I drove to the nearest craft store (30 miles away) and asked for and bought some "Gorilla Glue". On the way back home I realized that I needed "Gator" glue.

Besides both being large animals whose names start with "G", how could I get these two confused? I mean, how many gators have you seen swinging hand-over-hand through the trees, or how many gorillas have you seen dragging Wildebeests into water holes??

The "Gorilla Glue" purports to be good for wood, metal, plastic, etc, but "requires" some wetness at the joining, and the glue supposedly expands a bit. Does this sound like your "Gator Glue"? The question is just....are they the same thing??

Any clues for the clueless (yours truly) would be appreciated.

jcf · August 31, 2008, 09:30:53 AM

Quote from: sequoiaranger on August 31, 2008, 09:07:49 AM
Hey Brian de Basher!

Thinking I was taking your advice, I drove to the nearest craft store (30 miles away) and asked for and bought some "Gorilla Glue". On the way back home I realized that I needed "Gator" glue.

Besides both being large animals whose names start with "G", how could I get these two confused? I mean, how many gators have you seen swinging hand-over-hand through the trees, or how many gorillas have you seen dragging Wildebeests into water holes??

The "Gorilla Glue" purports to be good for wood, metal, plastic, etc, but "requires" some wetness at the joining, and the glue supposedly expands a bit. Does this sound like your "Gator Glue"? The question is just....are they the same thing??

Any clues for the clueless (yours truly) would be appreciated.

Hi Craig,
Gator's Grip Hobby Glue is a completely different product that you can order from the source:
http://www.gatorsmask.com/gatorglueorder.html

He has a notice on his home page that ordering is temporarily suspended due to his getting prepared for Gustav.

Gorilla Glue is a water-activated polyurethane adhesive that foams to fill gaps, it works well for carpentry etc.

Jon

sequoiaranger · August 31, 2008, 09:42:45 AM

Jon--Thanks.

I Googled Gorilla Glue and Gator Glue and found out the same thing. Thanks. It appears that this wondrous new glue is a cottage-industry product and NOT available in LHS??

I fear that this new "Katrina" could wipe out the sole source of this glue. Maybe he can secure a lucrative contract with the US Govt to smear some of that glue over the New Orleans levees to keep them from breaking!!