Author Topic: Ki-84 U.S. testing  (Read 5698 times)

Offline SgtPappy

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Ki-84 U.S. testing
« Reply #45 on: January 23, 2008, 10:57:41 PM »
And there's no test data on it?
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Offline Karnak

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Ki-84 U.S. testing
« Reply #46 on: January 24, 2008, 12:50:34 AM »
Not sure.  Data may have been lost.
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Offline Stoney74

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Ki-84 U.S. testing
« Reply #47 on: January 24, 2008, 01:52:54 AM »
Quote
Originally posted by Karnak
...so I don't understand what you're asking to be proven.


I was talking about Pappy's post that the "Ki-84 should [emphasis added] be faster than the F4U..."

My point overall here is that there are aerodynamic factors in play that (1) should be used to make these types of determinations or (2) if the data to do #1 are not available, then its really a weak opinion.

I'm not trying to denegrate anyone here.  Pappy, you seem to express a true desire to understand what makes these planes behave the way they do.  My point is merely to help you make informed opinions.  I probably should have worded things a little less bluntly in order to remove any perception that I was being condescending or rude.  I do not know all of the answers--I stalk this board to try and find them just as you guys do.

I enjoy these discussions probably more than anything else on these forums, so I don't want to indirectly shut them down by being a jack-a**.

Cheers,

Offline Charge

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« Reply #48 on: January 24, 2008, 06:19:31 AM »
Sry bout that Karnak.

"What I object to is the idea that sites like Luft46 give uninformed people that Germany or Japan had things that were about to see service that were far in advance of anything the Allies had and that just isn't true.

I certainly agree with you on that.  While some of the new types were certainly interesting and would have probably seen limited use their effect would have been, at best, negligible. Pretty much like ME262. Interesting but in practice very vulnerable piece of machinery in that strategic and tactical situation they were used in.

***

"I was talking about Pappy's post that the "Ki-84 should [emphasis added] be faster than the F4U..."

"My point overall here is that there are aerodynamic factors in play that (1) should be used to make these types of determinations or (2) if the data to do #1 are not available, then its really a weak opinion."


I'm interested of what you people think why Ki84 could not be as fast as Corsair?

Less power yes, but Frank was also smaller and lighter. So does it come down to what was the 84's engine's critical height of operation? If you consider that it could be tuned to operate a bit higher the Ki84 would be in the same ballpark with D model?

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Offline Kweassa

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Ki-84 U.S. testing
« Reply #49 on: January 24, 2008, 10:30:14 AM »
Quote
I'm interested of what you people think why Ki84 could not be as fast as Corsair?


 As am I.

Offline SgtPappy

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« Reply #50 on: January 24, 2008, 02:30:46 PM »
Quote
Originally posted by Stoney74
I was talking about Pappy's post that the "Ki-84 should [emphasis added] be faster than the F4U..."

My point overall here is that there are aerodynamic factors in play that (1) should be used to make these types of determinations or (2) if the data to do #1 are not available, then its really a weak opinion.

I'm not trying to denegrate anyone here.  Pappy, you seem to express a true desire to understand what makes these planes behave the way they do.  My point is merely to help you make informed opinions.  I probably should have worded things a little less bluntly in order to remove any perception that I was being condescending or rude.  I do not know all of the answers--I stalk this board to try and find them just as you guys do.

I enjoy these discussions probably more than anything else on these forums, so I don't want to indirectly shut them down by being a jack-a**.

Cheers,


It's not that it seemed harsh, it only seemed like you were suggesting my Ki-84 performance assumption was a whine, but no worries, I'm just clearing up what I'm really here for.
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Offline Stoney74

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« Reply #51 on: January 24, 2008, 08:46:26 PM »
Quote
Originally posted by Charge
I'm interested of what you people think why Ki84 could not be as fast as Corsair?


Do we have some data?  I'll believe if we have the data.

But again [kicks dead horse], just because its smaller and lighter does not mean an inference should be made that it could be just as fast.  Turn better?  Climb better?  Perhaps.  Faster?  not necessarily.

If you say the Ki-84 should turn better than the Corsair, I'd say that's a reasonable observation, as the wing loading would be lower (even though there may be other factors).

If you say the Ki-84 should climb better than the Corsair, I'd say that's a reasonable observation, as the power loading would be lower.

If you say the Ki-84 should be as fast or faster than the Corsair, and your justification was that "it looks more aerodynamic", I'll take issue with that.  What airfoil was used on the Ki-84 and what was the design lift coefficient of that airfoil?  How much washout was built into the wing?  How efficient was the stabilizers' sizing with respect to trim drag creation?  How efficient was the engine baffling?  What was its flat plate drag area?  How efficient was the propellor?

All questions that would need to be known to form a defendable theory on how fast the aircraft should have been.  I'm not saying the KI-84 shouldn't be faster, I'm merely critiquing the evidence used to justify the theory.

Offline Saxman

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« Reply #52 on: January 24, 2008, 11:44:00 PM »
Actually, between 5000-10,000 no WEP, and ~2500-7500 with WEP the Ki-84 IS faster than the 1D and 1C by a slim (may as well be nonexistent) margin.

However the Birdcage, 1A, and -4 are no contest.

Though even if the Frank operated at peak possible performance based on the design on paper, she would have still been pwnt by the 4Hog. :D
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Offline Charge

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« Reply #53 on: January 25, 2008, 07:43:17 AM »
"If you say the Ki-84 should be as fast or faster than the Corsair, and your justification was that "it looks more aerodynamic", I'll take issue with that. What airfoil was used on the Ki-84 and what was the design lift coefficient of that airfoil? How much washout was built into the wing? How efficient was the stabilizers' sizing with respect to trim drag creation? How efficient was the engine baffling? What was its flat plate drag area? How efficient was the propellor?"

Interesting points. My thoughts about those:

Airfoil is a significant factor in determining drag but even with completely same airfoil but smaller you will have less drag. The airfoil lift coefficient can be a two bladed sword in high speed. The more asymmetric the airfoil is the more it may need negative AoA to get  l e s s  lift from it in high speed and then the airfoil starts to cause more drag, that is why a symmetric airfoil is better for high speed since you can control the amount of lift with very little changes in AoA. The best result would probably be nearly 0deg airfoil angle (if the weigth permits) at the same height where the engine has its second FTH (highest) combining lowest drag with best power.

Washout can probably have negative effects too. Consider an FW190 going full speed and its wing root profile is in 0 deg angle to airflow. It will have its wing tips -2 deg against the airflow. I don't think that is necessarily good drag-wise. It can be but I have a feeling it mostly doesn't. So the point is what amount of lift can a specific part of wing area produce at certain speed with the airfoil shape in question? If the 0 deg angle lift overcomes the weight of the a/c it will begin ascending and it will need negative AoA to stay level. I do not know if this happens in any WW2 a/c, even Spitfire with its huge wing area (it has washout too). A smaller wing may need more positive AoA at engines too high alt FTH pretty much negating to effects of increased power.

Flat plate drag area also needs to take into account the angle in which the opposing surfaces are to airflow. With this I mean that a coin can have smaller flatplate area but more drag than a slightly bigger ball giving different drag figures.

Considering the speed i don't think the trim has any significance unless it  clearly tries to force the plane into attitude it does not want to be in and that usually happens in very slow speed, although possible also in high speed if you need to force the a/c into other attitude than it naturally tries to remain.

I'm not sure what you mean with engine baffling other than the air bleed from inside the cowling to outside and that depends on how much cooling the engine needs at given speed. I'd bet that in most cases the more flow through the engine the more drag. If the cooling louvers are closed the cooling air pretty much churns inside the cowling but causes less drag. So in a way yes the cooling efficiency of the baffling dictates the need to open the louvers which would increase drag.

Propellor, of course has a huge effect. If the propeller is inefficient there is no use in increasing the power as the performance may even decrease if the force does not transfer to surrounding air.

I have often wondered how much drag radials actually have from drag calculation point of view and come into initial conclusion that as long as the propeller rotates and disturbs the air flow in the center of the engine the drag is rather low (not as low as in inline engines of course), but if the propeller stops the drag rises dramatically and thus they are quite hard to calculate for static models.

But as it was said there is not enough data to make further conclusions. It is just that the speed figures seem to support the conclusion that with slightly higher FTH the Ki84 could keep up with Corsair for what ever the reason.

-C+
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Offline SgtPappy

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Ki-84 U.S. testing
« Reply #54 on: January 26, 2008, 07:56:02 PM »
Though that's good reasoning, I guess we'll never know if the Ki-84 could perform like a Hog until there's some hard data, similar to the ones on aircraft conditions, weights, fuel used etc.
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Offline John Curnutte

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« Reply #55 on: January 30, 2008, 02:16:47 PM »
Wow Widewing you sure know your stuff about these planes , I learned alot about the KI 84 just reading some of these things and seeing the stats , Thank you sir :aok
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Offline MiloMorai

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« Reply #56 on: January 30, 2008, 02:45:01 PM »



Offline 2bighorn

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« Reply #57 on: January 30, 2008, 03:32:20 PM »
Quote
Originally posted by Widewing
I haven't seen anything to support 437 mph... maybe 425 mph, sans ammo, paint and highly polished, with a perfectly tuned motor running fuel that the Japanese didn't have.
How does higher grade fuel increases performance of an engine, running at mil (or WEP) power which was designed to run on fuel Japanese did have?

Offline BigPlay

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« Reply #58 on: January 31, 2008, 11:28:29 AM »
Quote
Originally posted by Charge
"Japan had no miracle wonder fighters about to come out at the end and turn the thing. Neither did Germany."

I didn't say that the Japanese had wonder weapons I said they had some advanced designs in the works. Nor did I say it would have mattered. My statement was just  on how advanced the Axis designs were. Germany did  have a number of aircraft that could have flown much earlier , there are tons of books on that subject. There was even more advanced aircraft on the drawing board and with a little R&R they would have even out classed their current designs.The Bell X-5 was a US test plane based on geometry wings that was totally a German design and in fact is identical to the US X-5 in almost every way. The Flying wing was another design started by the Horton brothers and was flying at wars end, not in operational  service but flying .The US F-86 wings were of German design as were the Mig 15's. So saying that German didn't have advanced aircraft that would have gone into production is unwarranted. They may not have changed anything by that stage of the war has nothing to do with the fact that those planes were way out in front of US designs that were on the drawing board. The German's also had intercontinental missiles that would have saw service if the war had gone on for another year. The F8, P-51 H and all the other late designs and modifications that the US had at wars end would have been totally out classed if these German planes had seen combat. Again  they may not have had the pilots to fly them to make much difference. My statement was originally in defense of bringing out other Axis aircraft that
would have added a little flavor to the game rather that another Spit or other variant of an existing plane.

Offline SgtPappy

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« Reply #59 on: January 31, 2008, 01:31:37 PM »
Thanks Milo!
Are those the Japanese texts from which the Americans made their copy? I have the same doc, but I can't read Japanese :D
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