Mitsubishi/Nakajima A6M2-N Rufe - RC Groups
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Oct 06, 2012, 10:56 PM
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Mitsubishi/Nakajima A6M2-N Rufe

I suppose that it's time for me to begin my first real scale project. Something that I been looking at is the floatplane variant of the Japanese Zero the Allies called the "Rufe". Its designation was A6M2-N and built by both Mitsubishi & Nakajima.

First deployed in 1942. It was powered by a 14 cylinder air cooled radial of 950 hp.
Wingspan: 12 m
length: 10.10 m
height: 4.30 m
weights: 2895 kg
maximum speed 434 km/h at 5000 m
range: 1780 km
armament: 2X 20 mm cannon; two machine guns; 120 kg of bombs.

One of my books is "the rand McNally Encyclopedia of military aircraft"
this is what it has to say about the aircraft: "in 1942 another singleseat fighter appeared which had been expressly made to answer the needs of the military bases scattered in the little islands of the Pacific, where it was impossible to construct airstrips: this was the Nakajima A6M2-N. this aircraft was a seaplane model of the carrier-based Mitsubishi A6M Reisen fighter, the renowned zero. Between 1941 in 1943, 327 aircraft of this model were produced which were in use up to the end of the war, carrying out their task effectively. In spite of its large floats, his performance compared with that of the zero was, in fact, only slightly inferior.

My intent is to take the GWS zero and evolve that into the floatplane variant.

I plan to do this in phases:

1. Assemble the airframe, inserting the electronics, and attaching a motor. The aircraft was originally designed for a brushed motor and gearbox. I will need to determine how to mount a brushless motor. I've also read that the aircraft, because of the motor, has wing and horizontal stabilizer incidence that may not work well with a brushless motor. So, I intend to prepare the plane and even fly it in its plain white unpainted foam condition simply to get a good flying aircraft.

2. semi finish the airframe by sanding the exterior and deciding at that point whether to use spackling to provide a smooth finish or even light fiberglass. It is at this time that I need to finalize any changes to the airframe that will make it looks more scale. At this point I will likely be removing or drilling out the cast foam guns and other fixtures that I will replace with a more scale three-dimensional look objects.

3. Start adding scale details. Next, I will probably apply a primer coat of paint to the aircraft and, perhaps, layout panel lines for scale implementation. This may also be the correct time to modify the cast in unused flaps and build the split flaps probably carried by the aircraft.

4. Then I will turn my attention to the floats. I bought a set of GWS floats that are about the right size scale wise, and not too far off shape. I will build the pylons supporting them and attach the floats to the fuselage and wings. They will be smoothed and painted with primer and panel lines located if possible. I know that the GWS float bottom is made from a hard plastic and maybe impractical to put panel lines upon it but we shall see.

At this point I should have a reasonable looking prime bird aircraft conceivably ready to test fly. I will work to that end.

5. Once I have a reasonably flying floatplane fighter, I will begin painting and detailing to bring the aircraft into conformance with higher standards of scale. I will also build and attach the guns, antennas, pitot tube and other such details. Don't forget trim tabs.

6. At this point, I should have an aircraft that looks reasonably like the original subject. If all is going well, I will at this time begin to consider a cockpit modification, in which I will cut away the foam cockpit and fashion a cockpit tub and canopy that will insert into the aircraft and increase the scale fidelity.

7. I may be done with it by this point but the only other thing I could think of, if it has turned out well, would be to replace the GWS float with a custom-made float for scale purposes.
Last edited by davidterrell80; Oct 07, 2012 at 12:16 PM. Reason: Added more documentation photos
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Oct 07, 2012, 11:46 AM
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Oct 07, 2012, 10:40 PM
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Comparing the GWS Zero kit to the Rufe 3-View

Welcome aboard! I hope you find this fun and instructive. I also encourage you to inquire and advise, if you think fit.

Evaluation of the GWS Zero Kit.

I looked through the kit, again, today. But, this time, I had scaled the 3-view to the wingspan of the kit so I could examine the scale characteristics... or the lack, thereof.

Here's what I found.

Fuselage: From the forward edge of the cowl to the trailing edge of the wing, all of the proportions are very scale. The tail moment is increased about 8 cm, although the scale of the vertical stab and rudder, themselves, are very close to the drawing, including the rudder balance but, no trim tab. So, I'd expect grater stability in Yaw and Pitch. There is also a couple of degrees of positive incidence in the model, relative to the main fuselage axis. The Horizontal stab appears to have a zero incidence. So, no down thrust may be required. Also, the fuselage has no panel lines, but is covered with spues, probably from pulling air from the mold. They will need light sanding and filling. The plastic cowl shows the provisions for the two 50-cal guns incorrectly. There is also no ventral keel, under the vertical stab.

Wing: The span is the standard for my comparison. The Leading edge and trailing edge sweep angles are scale. However, the root chord of the model wing is about 2 cm greater than scale. This causes the radius of the planform tips to be correspondingly greater. The chord of the ailerons are about scale but their span is greater in the model, and extend to the end of the wing. There are no provisions for wing-mounted guns. The wheel wells will need to be filled and refinished, as will the slot for the wing spar. One of my design decisions will be reducing the span of the ailerons about 2 cm on the inboard end and making a provision for the split flaps. The current aileron setup calls for a centrally mounted servo and torque rods. I may use flexible rods for the ailerons and torque tubes for the flaps.

Horizontal Stab and Elevator. About 3 cm greater span and about 1 cm greater chord. Reasonable for model aircraft, especially given the increase in tail moment.

As I mentioned for the Fuselage, so the entire airframe is covered by the evacuation spues. A light sanding and filling will help a great deal.

As I sit here, pondering the difference in fuselage length, I realize the need to check the proportions of the Zero, itself. I wonder if the fuselage of the Rufe was shortened to keep the aircraft nimble in yaw, given the addition of the float. If so, I may actually cut the fuselage down.

Edit: I put 3-views of the Zero and Rufe in overlay and verified that both were the same... and that both had the proportionally shorter tail in the 3-view, indicating that the GWS kit has an lengthened non-scale, tail moment. I'll probably keep it and call it good. Extra dynamic stability in yaw and pitch is good for me.
Last edited by davidterrell80; Oct 07, 2012 at 11:38 PM.
Oct 11, 2012, 08:51 PM
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I've been pondering the effect of the kit's extra length, when compared to scale. I looked at photos of a similar bash made by someone else.

That model seems to sit a bit "tail down" in the water.

The CG location will decide the balance point and I will be orienting the float so the step is just aft of the CG. In the scale 3-view, the float extends aft to a point about 61% of the CG to Rudder -hinge distance. If I keep a scale length float, it will only extend 53% of the distance on the model. The effect of elevator will be more pronounced on the float.

I'm really thinking about taking about 1.5 inches out of the fuselage.
Oct 11, 2012, 11:26 PM
I even seen a house fly!
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Hi David! I'm subscribed!

Watching with much anticipation and popcorn!


Oct 12, 2012, 05:45 AM
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Hi, Kitty,
You are most welcome, here. I appreciate the work you've done. Looking at yours, and others have forced me to think closely about the scale-related issues of warterplanes. I want our Rufes to succeed...

I was thinking about the "tip float dig" issue last night, after seeing the pinwheeling issue.

The scale floats have a "vee" cross section on the bottom to reduce slapping. But I dont have a pilot to worry about. So, I'm thinking of flattening the bottom of the tip floats, either adding transparent chines or physically flattening the bottom, leaving a scale side view and perhaps using painting techniques to imply the scale shape from a distance... slightly shortening the strut length to allow more roll allowance... Perhaps even adding some transparent chines to the main float so it doesn't dig in so much on touchdown.
Oct 13, 2012, 07:43 PM
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I had the Polaris seaplane flying today in 15 kt winds. It is very neutrally stable in roll and flying was a challenge. I'm thinking it will benefit from a gyro... and as I was trying to make my landings as flat as possible, I realized that having flat-bottomed center and tip floats was a great benefit.

I'm thinking I will make the float bottoms' vee much shallower than scale.
Oct 14, 2012, 09:19 PM
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I've evaluated the GWS float. It is the correct scale length and width for the 850 mm wingspan Zero. I'm still concerned that the aft fuselage is a bit longer than scale. I did more accurate calculations against another 5-view and the length was increased by almost exactly 2 cm... which is accounted for by the increase in root wing chord.

I will just build it and make provision for any needed modifications of float position and angle relative to the fuselage. I am going to leave about one half of the wing incidence in the airframe and provide for adding down thrust.

Work is being particularly demanding during this month... progress will be slow.
Oct 16, 2012, 05:25 AM
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I had some time last night and started the airframe. It's about 50% complete. I'll rig the flying surfaces this evening, with a blessing, and she'll be ready for some filling, sanding and basic painting. I'll post the accumulated photos then.
Oct 20, 2012, 03:40 PM
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I've been working on the build; but, I lost my cable that allows me to transfer pictures from my Blackberry. I just obtained a replacement.

So, here's a photographic update.

As you can see, I decided to abandon the slow, methodological approach and am behaving in a more "Complex Adaptive" manner of building I cal "Just do it Construction."
Last edited by davidterrell80; Oct 20, 2012 at 03:47 PM.
Oct 23, 2012, 10:08 PM
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Had to miss working on the Rufe for two nights... but I did get some work on the floats done Monday night.
Oct 24, 2012, 09:50 PM
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I love this project!
I did a serious bash from a parkzone T-28 to a N1K1 Shiden, the prodigy of another cool Japanese floatplane, the Rex. There's a build thread for it.

You can imagine that I'm all over this one! I'll be watching with keen eyes.

Great work.


Latest blog entry: Raiders Wing from Scratch
Oct 26, 2012, 06:26 AM
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Hi, Sperling.

I actually considered using the PZ T-28 as the seed for my rufe... but the overlay was a bit too different for my taste.

I may yet try my hand at turning a Trojan into something else.

I've made progress on the Rufe in hand. The current design decision is how (or if) I can attach the tip floats to be detachable and yet handle the loads without too much weight gain.

Photos later.
Oct 26, 2012, 09:37 AM
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Great job David!

It's wonderful to see someone building the Rufe from the GWS kit. I thought about doing this many years ago when GWS came out with the Zero. It was one of my first electrics that I really enjoyed flying.

I had also thought about enlarging the Guillow's Rufe plans from the kit I have, but since getting married this past May my R/C activities have been put on the back burner.

I'll be eagerly watching your progress!


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