• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Ki-46 “Dinah”

#1
Hello! (Mad) Scratch builder here :)
The goal of this thread is to document my attempts at designing and building probably my favourite aircraft to come out of the (LARGE) WW2 lineup.
9C835016-1A08-42CE-9A3A-54B433F89A47.jpeg
The ki-46-III “Dinah”.

I’m being incredibly ambitious here, haha. My goal is to make the whole airframe out of dtfb (i get mine at the dollar store). It will have a ~60in span with flaps, and i havent decided on retracts yet. Is it worth the hassle? And if so, what brands would y’all recommend? I’m aiming for an AUW of below 3-4lbs (giving myself LOTS of wiggle-room).

More people are familiar with the other twins of ww2. The p-38s, the mosquitos, and the F-7Fs. While all of these are indeed amazing aircraft, they are late-war and armed to the teeth. The ki-46 was the plane that preceded all of that. Up until p-38s were brought to the pacific, orders for the Dinah were to punch it whenever they found themselves in a bind. No other planes were able to match it in terms of speed.

And IMHO no plane BUT the p-38 can match its looks.


68E590A9-CEAE-4D47-8DE9-00DBBA1B5C1D.jpeg 7E12741E-2FD5-497A-BB78-D65982774B82.jpeg

I digress, though. I havent even ordered a power pack for it, so basically i’m making this post so that i can stay motivated to build it, haha. Are retracts worth the headache of setting up, or should i hope for the best while belly-landing?
 

FoamyDM

Building Fool-Flying Noob
#2
Ooh.

I just pulled out my Boy Scout Popcorn bag. 'cause this will be worth it. I'm interested to see if you will do this Master Class style, or a hex/octo-walled setup. I did not know about this sexy bird. (reminds me of the Bugatti m100 lines.)
 
#3
I was thinking masterclass-style. Setup an extra strip under all the panel joins so i can sand even those smooth and then paint over it. I love the bugatti, too! Sweet lines and who can resist y-tails, lols?
And you thought v-tails were the rage.

My big question is should i make a clear canopy? I could cut up a few pepsi bottles, or something else, i dunno. But right now just making everything solid is priority no. 1
 

Zephyr1

Well-known member
#4
I actually really love the Dinah. Ever since I saw it on the Long Odds episode of Dogfights when I was little, I've thought the curves and lines of the airplane are superb. I played around with designing a Dinah last winter but got distracted by other projects lol. I think you should make a solid canopy and retracts are way to heavy and barely ever work. I'm very excited to see this project moving forward. Good luck!
 
#5
I actually really love the Dinah... Good luck!
Hehe, thanks a bunch! When i came across the Dinah i was actually just surfing through wikipedia’s list of japanese WW2 aircraft. I had to stop and go “wow” at the simplicity and beauty of the design. The military was drunk on power from the chinese war when they asked for new designs, but all the aircraft designers sure knew what was up.

It is truly a shame that the military had to stick to the mantra of maneuverability. If they had prioritized the development of engines and faster, durable airframes, the war would have been so very different. I find many allied/german designs very “boxy” and designed for combat. To pull from wikipedia: “The specification (for the type-100 reconnaissance aircraft) demanded an endurance of six hours and sufficient speed to evade interception by any fighter in existence or development, but otherwise did not constrain the design by a team led by Tomio Kubo, whose AESTHETICS are very significantly infused to the aircraft.”

Art is win.

As far as my re-design goes, a solid canopy it is, then! Some rough math puts a 60in-span at a1/10th scale. At the same time i’m building/designing the Dinah, i’ll be constructing nerdnic’s ki-61 to learn the “innards” of the speedwing (separate thread).

My main flying “field” is the off-hours parking lot of my old high-school (soccer field adjacent), so i think i can brave retracts. The only hassle should be getting them aligned. I have to re-read the manual for the lemon RX i have, but i’m pretty sure it said that i cant have SPLIT ailerons AND retracts if i want the included gyro. If so, then i already have a working y-harness so i should be fine. I’ll just have to re-assign the chanel on my DX8e.

I should get on to drawing formers and ordering electronics by next wednesday, so stay tuned!
 
#6
I might be overconfident at the moment, but I REALLY want to shake the hand of whoever designed the Dinah. All these lines are beautiful, and when you break it down the design is soo simple it hurts haha. All the flying surfaces are angular with rounded caps, and the fuselage is just a bunch of ovals joined at the thrust line.
Using the drawings I have, i’ve Found some rough dimensions.
Span will be roughly 1.5m and length is 1.13m. If I can keep the weight down, the two turnigy 1500 kvs should be more than enough to keep it in the air.
Next post will be the fuselage formers being drawn.
 
#7
Hmm, anyone want to chime in? The drawings show the main wing at a positive AOA. For my model, should I omit that, or keep it in true scale-modeler form?
 

Zephyr1

Well-known member
#8
I think omit the positive AoA but that's just me. So I got to fly the new C-47 and see the Mosquito at Edgewater yesterday and it's inspired me to attempt a twin A back WWII plane. What I'm trying to say is that I'm gonna try making a Dinah as well. I've loved the plane forever and I've got this 1/48 model for reference! I still can't wait to see how yours turns out @Robyle3 because it will be larger than mine.
 

Merv

Well-known member
#9
i havent decided on retracts yet. Is it worth the hassle?
I think retract are very cool and add a lot to the flying experience. Are they worth it? It depends on your flying site and skills. For me, NO. My flying site has a crude runway. I don't care how good you are, the retracts will get torn off. Retracts are just not as robust as a fixed landing gear.

If you fly off a smooth runway and have some experience then, YES, retracts are worth it.
 
#10
If you fly off a smooth runway and have some experience then, YES, retracts are worth it.
Thanks, that is what I needed to hear, haha. The parking lot I use for my flying Feild recently was re-paved, so the surface is pristine. But I have zero actual experience with retracts (simulator only), so I should use them on a plane I'm not emotionally attached to first to build some experience.

Edit (Nov 9,'19): re-reading all the posts, I realize I'm trying hard to give myself an excuse to buy retracts XD. I can't resist the "cool" factor, but until I can bring a finished plane to my LHS, it'll have fixed gear to ease the screaming builder in me. And keep weight down.
 
Last edited:
#11
@Zephyr1 that sounds great! I'm going all out and making all the curves, but on a smaller model I don't think that it'd be practical. Using a physical model is such a better way to understand how the curves work (I'm stuck looking at hundreds of pictures, but they can't beat actually feeling it out).
Be sure to make a thread about it! I'd love to follow.
 
#12
Process post #1
Ok, so two days late, but I kinda got sidetracked when my father brought home this adorable little stray:
20191107_151801.jpg
Stuffing itself right into my sweater was probably the cutest little thing it could've done.
*melts*


ANYWAY, back to the Dinah.

All the fuselage cross sections are done! The flying surfaces were easy since they contained lots of straight lines. Lots of ovals later....I realized I forgot to count in the foam thickness. But, since I had the guides, I just hand-drew an inner oval with the right radiuses. I'll use the large radius to make sure I have enough foam to make it around the fuse, then pop the ring off, and use the smaller radius to make sure the outside skin is the right diameter. "Is all that detail really important?" you may wonder.

Yes, yes it is.

Note on drawing ovals:
Ovals are not the nightmares "ruler and compass" people like me at first imagine them to be. The steps are incredibly simple.

Measure out the width and height of your oval, making sure the lines intersect in the center of your oval.
20191108_205452.jpg
Set your compass point in the center, and stretch out to the end of the LONG radius.
20191108_205542.jpg
Now set your compass needle at the end of one of the SHORT radiuses, and turn it along, marking where the arm intersects the long radius.
20191108_205617.jpg
Anchor two pins at these marks.
Tie a loop of string long enough to rest against a pin and reach the opposite end of the long radius (much easier done with a third pin).
20191108_205900.jpg
Now, take a pen/pencil, remove the third pin, and use the string to guide you around the oval!
20191108_210055.jpg 20191108_210113.jpg
Protip: use a razor to cut a VERY small ridge on the pencil lead. This keeps the string from slipping under (don't ask me how many freakin times I needed to cuss at a slippery string to figure this out).

On the same board I squished the fin/rudder. I love @nerdnic 's idea of doubling the empennage to make it aerodynamic, but I, uh, flubbed and accendentally made two of the same side *facepalm*
20191108_211604.jpg
(These are the outside facings, nothing a paintjob won't fix, right?)

The stabilizer is a funny story, too. I am probably going to be having nightmares about the number 6.9. Something just felt "off" about the original drawing, so I decided to go by aspect ratio, and sure enough, turned out I was off by a lot. In case anyone is wondering, the rounded tips are hand-drawn on and cut from draft paper.
20191108_213238.jpg
(Sorry for the faint lines, but hopefully you can see the shape)

Now I am working on the longerons for the fuselage, and only after a day of measuring my reference page, multiplying by 6.9, and marking on the foamcore did I remember that the formers aren't perfectly concentric. So the outline you see on the foamcore here is actually useless, but it does finally give me a visual on how much space this lady will take up. I'll use some cool trickery and fix it up. (Writeup in next process post)
 

Attachments