The Zero's Maneuverability (4 Viewers)

[ThomasP]

Very nice, Aeroweanie.

 

[Ivan1GFP]

I would not disparage a plane just because it was built in wood: Even in WW2, it would be more appropriate to call it composite which of course has much more positive connotations to our modern ears. An advantage with wooden "composites" is that you can easily do compound curved panels and improve the aerodynamics that way. The Mosquito was a "composite" plane and so was the J22 in some parts, and I think few would say the Mosquito was crap just because it was built of "wood"?

When it comes to drag the biggest dominating factor is size: The frontal area and wetted area. The Bf-109 was actually not a very clean design, but it was still fast simply due to its small size. Then when it comes to eyeballing, this can actually tell you a lot if you look at the right things: For example, are there bulges for guns etc? Is there a razorback fuselage or a bubble type canopy? If the latter, how well faired is it? Is the radiator/air cooling entry well done? Is the forward windscreen upright and plane or angled backwards, rounded and faired? How are the wing and fuselage "lines" and are there ill-fitting openings, hatches and gaps? Is the main landing gear totally retractable and fully hatched in? Is there a fixed or retractable tailwheel?

And comparing this list between the J22 and Zero I don't find the J22 wanting, so as a first order approximation scaling on wing area alone will give you a good idea about their relative performance. However, that being said, I have not seen good data on how much power they (the Japanese pilots) extracted from the Sakae 12 at WEP. But in the US test they ran at 2600 rpm (no boost data), and to the best of my knowledge Japanese data says max 2550 rpm WEP. I have a Japanese power chart that goes up to 2550 and in that I have extrapolated what 2600 RPM would do, and apart from increasing the FTH, the power in that chart goes up from 960 hp to about 980 hp. However, that chart is from May 1939 and the boost pressure is not given. And it's of course possible that they increased boost pressure later on. So if anyone has data on this, this would be interesting to hear about.

About the J22: It only had a single stage blower (TWC-3 R-1830-SC3-G) and the speed point at altitude is not point shaped but like on the Zero more rounded in shape with the top speed achieved at about 15,000 ft. However, digging a bit deeper, I found some simulations done by the Swedish aeroengineer Håkan Langebro, and it seems it only did the 360 mph with 100 octane fuel and the engine producing circa 1200 hp, and with 87 octane it only did slightly under 350 mph with 1050 hp which is still quite good for that amount of hp.

So if the small and clean J22 did 350 mph with 1050 hp, then the 345 mph Sakai claims for the much bigger Zero sounds optimistic to me. Especially if the absolute top power they got out of the Sake 12 was only 980 hp. But it would of course help to be able to pin down the exact power output of the Sakae 12 when it was at the peak of development, and if this was higher than the 980 hp at 2600 rpm which is the highest I know about. In addition, are we sure that the 345 mph with the Zero Sakai claims was with a Sakae 12, and not the Sakae 21 engine?

The Wooden Eyeball part was a rather poor joke about your name as it translates from German.
Regarding the Testing of Koga's A6M2, there is actually some documentation in this thread if you missed it.
Look for Post #156 by R Leonard.
The tests did not seem to exceed the 2550 RPM limit, list the Manifold Pressures used and don't even seem to have hit the limit of what the engine was capable of.
There are comments in at least one of the reports as to the poor finish and ill fitted panels and carburetor problems.
As for an indication of what the actual Manifold Pressure limitations were, it is worth looking at the drawing of the Manifold Pressure Gauge in one of the other reports.
From earlier research, I believe that the limits as shown on the gauge were correct for A6M2 (Type 0 Mk. I) but the Japanese used the SAME gauge for the Type 0 Mk.II fighter which used the Sakae 21 engine. This was strange.

As for a comparison with the J22, keep in mind that the Nakajima Sakae was a smaller diameter engine than the R-1830. The speed advantage of J22 was probably BECAUSE it had a much smaller wing. It is definitely a fatter aircraft.
As for the Sakae 12, it was not a highly boosted engine and did not get that much development in the A6M series.
The Sakae 21 as I mentioned before got some additional low altitude power and a higher critical altitude. It wasn't a great improvement over Sakae 12 but any more powerful engine would have entirely lost the long range capability of Type 0 as in the eventual A6M8.

As for eyeball determination of drag, sometimes this works and sometimes it does not. A good example of this was the experiments conducted on Spitfire to simulate flush versus round rivets. This proved that on the fuselage, the round rivet heads had no great effect. This is probably because these little imperfections are in the boundary layer of stagnant air. This is also why the radiator intake of a P-51D has about a 3 inch gap from the fuselage. This is also why a model airplane is not necessarily a good aerodynamic test for the full scale beast. You can leave off the windscreen off a model and probably not notice any impact on speed