Why were the George and Jack so slow?

[old hoodoo]

It seems like,with available hp the WWII George and Jack should have been
faster (specs on new a/c). Both are commonly referred to as being in the 360
mph class under optimum conditions. Yet they had high hp engines with four
bladed props. Bad airfoils? Too much frontal cross section? Prop
inefficiency? Weight? (the George supposedly did not have a weight
problem).

[Yann Delcan]

The Jack had a very large frontal section due to its large 14 cyl. 2 row
Kinsei bomber engine. Even if fitted with an extension shaft and close
cowlings, it remains a fat aircraft.
However, the light J2M2 could reach 371mph and the latest J2M5 382mph, which
is faster than your datas. I admit the J2M3 (most produced variant only
reached 365mph).
The N1K2-J could hit 369mph. But its engine cowlings had not been improved
for economical reasons over the N1K1-J.

-One of the problems at this time was petrol availability and quality and
building quality. It is said that a captured Ki-84 (using the same engine
and claiming 'similar' performance : 392mph) running on US hi-octane fuel
went up to 427mph thus exceeding the P47 and P51 top speed.
I presume slightly similar performance could have been recorded with the J2M
and N1K2-J in the same conditions.
-If you thoroughly look at the japanese aircraft appearance in museums, you
would be surprised by the dreadful quality of the surfaces. Those planes
look awful (Cosford Ki-100/Ki-46, NASM A6M5, Pensacola N1K2-J..). Imagine
what could have happened if they had been made with good quality alloy and
qualified workers ? Remember those planes were built in dispersed factories
under the B29 bombs and with MUCH less engineering.
Finally, this was not an bad performance.

> It seems like,with available hp the WWII George and Jack should have been
> faster (specs on new a/c). Both are commonly referred to as being in the
360
> mph class under optimum conditions. Yet they had high hp engines with
four
> bladed props. Bad airfoils? Too much frontal cross section? Prop
> inefficiency? Weight? (the George supposedly did not have a weight
> problem).
>
>

[Yann Delcan]

> Kinsei bomber engine

---> 'Kasei', not 'Kinsei' of course !

[The Enlightenment]

"Yann Delcan" > wrote in message >...
> The Jack had a very large frontal section due to its large 14 cyl. 2 row
> Kinsei bomber engine. Even if fitted with an extension shaft and close
> cowlings, it remains a fat aircraft.
> However, the light J2M2 could reach 371mph and the latest J2M5 382mph, which
> is faster than your datas. I admit the J2M3 (most produced variant only
> reached 365mph).
> The N1K2-J could hit 369mph. But its engine cowlings had not been improved
> for economical reasons over the N1K1-J.
>
> -One of the problems at this time was petrol availability and quality and
> building quality. It is said that a captured Ki-84 (using the same engine
> and claiming 'similar' performance : 392mph) running on US hi-octane fuel
> went up to 427mph thus exceeding the P47 and P51 top speed.
> I presume slightly similar performance could have been recorded with the J2M
> and N1K2-J in the same conditions.
> -If you thoroughly look at the japanese aircraft appearance in museums, you
> would be surprised by the dreadful quality of the surfaces. Those planes
> look awful (Cosford Ki-100/Ki-46, NASM A6M5, Pensacola N1K2-J..). Imagine
> what could have happened if they had been made with good quality alloy and
> qualified workers ? Remember those planes were built in dispersed factories
> under the B29 bombs and with MUCH less engineering.
> Finally, this was not an bad performance.
>


There is an article here on Japans coal to oil and shale to oil
efforts:

http://www.fischer-tropsch.org/primary_documents/presentations/AIChE%202003%20Spring%20National%20Meeting/Paper%2080d%20Stranges%20Japan.pdf

Although the Germans developed succesfull synthetic coal to oil
technologies based on high pressure (700 atmoshpheres) hydrogenation
(higher octane fuels for aero engines and could use brown coal) and
Fischer-Tropshch synsthesis (diesel, chemicals and low grade gasoline
and used mainly the black coal) they were still at an disadvantage in
high oactane fuels and the performance of their engines suffered.

The Japanese relied on LTC (Low Temperature Carbonisation) which
yields at most 100L of tar/oil per ton of coal. (It also has about
250kg of a coke like char that is a usefull fuel)

It would be interesting to compare Japanses fuels to US ones. US/UK
fuel was I believe 115/125 wheras the Germans had to deal with 87 and
latter improved to about 97

I suspect one reason for the Germans keeping the Me109 is production
so long is because it could run on 87 octane fuel even in its latter
versions.