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Stretching WW2 Designs



 
 
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  #1  
Old August 21st 04, 03:12 AM
JDupre5762
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Default Stretching WW2 Designs

I have been wondering why were so few WW2 aircraft designs "stretched" in order
to get more performance or payload? I know of the FW 190D which was stretched
in the aft fuselage section in order to compensate for the installation of Jumo
V 12 engine. Could other designs have benefitted from the technique of
stretching in one way or another? Was it not done because the designs of the
era were not suited to it? In recent years even reworked C-47s have been
stretched. Was there simply no perceived need to stretch a design?

John Dupre'
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  #3  
Old August 22nd 04, 02:25 PM
Lawrence Dillard
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Recall that the inline Allison-powered P-40, developed from a radial-powered
predecessor, benefitted from such an aft-fuselage stretch, improving its
fineness ratio, allowing for drag-reduction at the tailfin-rudder interface,
and even allowing for fitment of a low-pressure variant of the RR Merlin.
Had the stretched P-40 been given the Merlin 20 series engine, it could have
become a serious high-altitude competitor.

Ballasting was not usually a good solution. In the Spitfire, for example,
ballasting was not very efficient when used in conjunction with the wider
and heavier Griffons, rendering tricky handling and at least one
test-establishment evaluation calling for cessation of production of Griffon
variants for that reason.

"IBM" wrote in message
...
(JDupre5762) wrote in
:

I have been wondering why were so few WW2 aircraft designs "stretched"
in order to get more performance or payload?

SNIP




  #4  
Old August 22nd 04, 05:24 PM
Presidente Alcazar
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On Sun, 22 Aug 2004 09:25:27 -0400, "Lawrence Dillard"
wrote:

Recall that the inline Allison-powered P-40, developed from a radial-powered
predecessor, benefitted from such an aft-fuselage stretch, improving its
fineness ratio, allowing for drag-reduction at the tailfin-rudder interface,
and even allowing for fitment of a low-pressure variant of the RR Merlin.
Had the stretched P-40 been given the Merlin 20 series engine, it could have
become a serious high-altitude competitor.


The P-40F and L had the Merlin 20, and the L the stretched fuselage.
I suspect you mean the Merlin 60 series, but as the first Packard
Merlin 60-series scale production didn't begin until the second half
of 1943, I can't see why the better Mustang airframe would have been
passed over in favour of what everybody was calling an obselete
airframe by 1942. The Merlin 20-engined P40's were out-performed by
the Merlin 45-engined Spitfire V as interceptors to start with, so it
made no sense to miss out on Spitfire IX/VIII production to use the
engines concerned to produce Merlin 60-engined P-40s.

Ballasting was not usually a good solution. In the Spitfire, for example,
ballasting was not very efficient when used in conjunction with the wider
and heavier Griffons, rendering tricky handling and at least one
test-establishment evaluation calling for cessation of production of Griffon
variants for that reason.


That was an early variant of the F.21, where the evaluation
establishment went beyond their remit, and where in any case the
problem was fixed. Meanwhile, two Griffon-engined versions had
previously gone into service, the first (the Mk XII) about eighteen
months beforehand, and the second (the Mk XIV) with great success,
being called the best single-engined fighter tested by the AFDU to
that point.

Gavin Bailey

--

Apply three phase AC 415V direct to MB. This work real good. How you know, you
ask? Simple, chip get real HOT. System not work, but no can tell from this.
Exactly same as before. Do it now. - Bart Kwan En
  #5  
Old August 24th 04, 04:07 AM
Peter Stickney
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Default

In article ,
(JDupre5762) writes:
I have been wondering why were so few WW2 aircraft designs "stretched" in order
to get more performance or payload? I know of the FW 190D which was stretched
in the aft fuselage section in order to compensate for the installation of Jumo
V 12 engine. Could other designs have benefitted from the technique of
stretching in one way or another? Was it not done because the designs of the
era were not suited to it? In recent years even reworked C-47s have been
stretched. Was there simply no perceived need to stretch a design?


For "stretch" it's rather hard to beat the Spitfire. I began the war
perfoeming at same level as its main competitors, and through
continual redesign and refinement was still in peak form when the war
ended.
Of course, installed power had more than doubled, the tail was
completely new, the feselage adn wing structure was completely redone,
they reshaped teh fuselage for a bubble canopy, and made a
fighter-bomber (And Carrier-borne Fighter-Bomber to boot) out of it.
Spits stayed in RAF and RN service well after the war. Not too half
bad.

I think that transports didn't get the same treatment for a number of
reasons. Most transport types didn't have options which afforded
greatly increased power, and the load carrying performance of
airplanes at that time was limited by available power more than
anything else - you'd run out of payload weight available before you
ran out of payload volume. Getting more payload required a whole new
airplane. The C-46 was considerable bigger than the C-47 it
supplanted.

That being said, I suppose you could make a case that DOuglas did
start a program of stretching transports with the DC-4-DC-6-DC-7
line.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
  #6  
Old August 24th 04, 01:30 PM
James Hart
external usenet poster
 
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Default

Peter Stickney wrote:
In article ,
(JDupre5762) writes:
I have been wondering why were so few WW2 aircraft designs
"stretched" in order to get more performance or payload? I know of
the FW 190D which was stretched in the aft fuselage section in order
to compensate for the installation of Jumo V 12 engine. Could other
designs have benefitted from the technique of stretching in one way
or another? Was it not done because the designs of the era were not
suited to it? In recent years even reworked C-47s have been
stretched. Was there simply no perceived need to stretch a design?


For "stretch" it's rather hard to beat the Spitfire. I began the war
perfoeming at same level as its main competitors, and through
continual redesign and refinement was still in peak form when the war
ended.
Of course, installed power had more than doubled, the tail was
completely new, the feselage adn wing structure was completely redone,
they reshaped teh fuselage for a bubble canopy, and made a
fighter-bomber (And Carrier-borne Fighter-Bomber to boot) out of it.
Spits stayed in RAF and RN service well after the war. Not too half
bad.

I think that transports didn't get the same treatment for a number of
reasons. Most transport types didn't have options which afforded
greatly increased power, and the load carrying performance of
airplanes at that time was limited by available power more than
anything else - you'd run out of payload weight available before you
ran out of payload volume. Getting more payload required a whole new
airplane. The C-46 was considerable bigger than the C-47 it
supplanted.

That being said, I suppose you could make a case that DOuglas did
start a program of stretching transports with the DC-4-DC-6-DC-7
line.


Speaking of transports, I'm surprised no one's brought up the Herk's recent
50th birthday.

--
James...
www.jameshart.co.uk


  #7  
Old August 24th 04, 01:47 PM
Peter Stickney
external usenet poster
 
Posts: n/a
Default

In article ,
Presidente Alcazar writes:
On Sun, 22 Aug 2004 09:25:27 -0400, "Lawrence Dillard"
wrote:

Recall that the inline Allison-powered P-40, developed from a radial-powered
predecessor, benefitted from such an aft-fuselage stretch, improving its
fineness ratio, allowing for drag-reduction at the tailfin-rudder interface,
and even allowing for fitment of a low-pressure variant of the RR Merlin.
Had the stretched P-40 been given the Merlin 20 series engine, it could have
become a serious high-altitude competitor.


The P-40F and L had the Merlin 20, and the L the stretched fuselage.
I suspect you mean the Merlin 60 series, but as the first Packard
Merlin 60-series scale production didn't begin until the second half
of 1943, I can't see why the better Mustang airframe would have been
passed over in favour of what everybody was calling an obselete
airframe by 1942. The Merlin 20-engined P40's were out-performed by
the Merlin 45-engined Spitfire V as interceptors to start with, so it
made no sense to miss out on Spitfire IX/VIII production to use the
engines concerned to produce Merlin 60-engined P-40s.


The P-40Fs and P-40Ls were also outperformed by various
Allison-powered P-40 models as well. The single stage Merlins, while
very, very good engines, weren't the leap in performance over its
rivals that the 2-stage (60 series and up) engines were.


Ballasting was not usually a good solution. In the Spitfire, for example,
ballasting was not very efficient when used in conjunction with the wider
and heavier Griffons, rendering tricky handling and at least one
test-establishment evaluation calling for cessation of production of Griffon
variants for that reason.


That was an early variant of the F.21, where the evaluation
establishment went beyond their remit, and where in any case the
problem was fixed. Meanwhile, two Griffon-engined versions had
previously gone into service, the first (the Mk XII) about eighteen
months beforehand, and the second (the Mk XIV) with great success,
being called the best single-engined fighter tested by the AFDU to
that point.


A couple of points here - the Griffon's frontal area wasn't that much
more than the Spitfires, and it was notably wider only at the top of
the cylinder blocks and heads. It wasn't that much longer overall,
either, due to clever relocation of the engine accessories.
While the Griffon Spits may have lost some of the Spitfire's perfect
handling, it didn't lose much. and the Royal Navy was flying them
from carrier decks into the 1950s. I couldn't have been that bad.
(They chose to dump the Corsair and keep the Seafires, after all.)

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
  #8  
Old August 24th 04, 01:53 PM
Graham Salt
external usenet poster
 
Posts: n/a
Default


"Peter Stickney" wrote in message
...
In article ,
(JDupre5762) writes:
I have been wondering why were so few WW2 aircraft designs "stretched"

in order
to get more performance or payload? I know of the FW 190D which was

stretched
in the aft fuselage section in order to compensate for the installation

of Jumo
V 12 engine. Could other designs have benefitted from the technique of
stretching in one way or another? Was it not done because the designs

of the
era were not suited to it? In recent years even reworked C-47s have

been
stretched. Was there simply no perceived need to stretch a design?


For "stretch" it's rather hard to beat the Spitfire. I began the war
perfoeming at same level as its main competitors, and through
continual redesign and refinement was still in peak form when the war
ended.
Of course, installed power had more than doubled, the tail was
completely new, the feselage adn wing structure was completely redone,
they reshaped teh fuselage for a bubble canopy, and made a
fighter-bomber (And Carrier-borne Fighter-Bomber to boot) out of it.
Spits stayed in RAF and RN service well after the war. Not too half
bad.

I think that transports didn't get the same treatment for a number of
reasons. Most transport types didn't have options which afforded
greatly increased power, and the load carrying performance of
airplanes at that time was limited by available power more than
anything else - you'd run out of payload weight available before you
ran out of payload volume. Getting more payload required a whole new
airplane. The C-46 was considerable bigger than the C-47 it
supplanted.

That being said, I suppose you could make a case that DOuglas did
start a program of stretching transports with the DC-4-DC-6-DC-7
line.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster


I had originally thought of the Spitfire as a good example of stretching
when this question first came up. However, on reflection, there was very
little airframe stretch during the service life of this type which
contributed to its ability to maintain parity in air combat. Essentially
there were two major airframe changes (Mk.VIII and F.21), and two major
engine ones (2-stage supercharging in Merlin 60's, and introduction of the
Griffon). The basic Mk.I led to the Mk.II, Mk.V, and ultimately the Mk.IX.
The Mk.IX was essentially an interim type allowing use of the series 60
Merlin engine before the definitive Merlin powered Mk.VIII was ready. With
the introduction of the Griffon engine, the definitive Spitfire was to be
the F.21 (and followed by F.22, and F.24). Again, to facilitate early
introduction of the engine upgrade, an interim model was introduced, based
on the Mk.VIII, and called the Mk.XIV.

During the history of the Spitfire, major changes to the airframe were few,
being restricted to accommodating the Griffon engine in the Mk.XII (another
interim model, based on the Mk.V), provision of a cut down rear fuselage to
allow a bubble canopy (Mk.IX and Mk.XVI onwards, although interspersed with
normal canopy), and F.21 onwards (redesigned wing). Other lesser changes
included extended wing tips for high altitude interception (Mk.VII,
Mk.VIII), increased surfaces to horizontal and vertical tail, changes in
armament from 8x 0.303 mgs to 2x 20mm plus 4x 0.303 mgs, 2x 20mm plus 2x
0.50 mgs, and finally 4x 20mm. Invisible changes included additional fuel
cells in the rear fuselage and fuselage strengthening.

But the most significant cause of the Spitfire's extended longevity was the
remarkable work of Ernest Hive's team at Derby in forcing more and more
power from the Merlin engine, and ultimately the successful installation of
the Griffon engine. Without the engineering brilliance of Rolls Royce, the
Spitfire, as a contemporary fighter, would have become obsolescent by
1941-42.

Graham Salt


  #9  
Old August 25th 04, 11:52 PM
Kyle Boatright
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Posts: n/a
Default

One aircraft which was stretched considerably was the B-29. It eventually
morphed into the B-50, the B-54, the C-97, the KC-97, the TU-4, the Guppy,
the Super Guppy, and probably a few more variants I've left off.



  #10  
Old August 26th 04, 01:17 AM
Peter Stickney
external usenet poster
 
Posts: n/a
Default

In article ,
"Graham Salt" writes:

"Peter Stickney" wrote in message
...
In article ,
(JDupre5762) writes:
I have been wondering why were so few WW2 aircraft designs "stretched"

in order
to get more performance or payload? I know of the FW 190D which was

stretched
in the aft fuselage section in order to compensate for the installation

of Jumo
V 12 engine. Could other designs have benefitted from the technique of
stretching in one way or another? Was it not done because the designs

of the
era were not suited to it? In recent years even reworked C-47s have

been
stretched. Was there simply no perceived need to stretch a design?


For "stretch" it's rather hard to beat the Spitfire. I began the war
perfoeming at same level as its main competitors, and through
continual redesign and refinement was still in peak form when the war
ended.
Of course, installed power had more than doubled, the tail was
completely new, the feselage adn wing structure was completely redone,
they reshaped teh fuselage for a bubble canopy, and made a
fighter-bomber (And Carrier-borne Fighter-Bomber to boot) out of it.
Spits stayed in RAF and RN service well after the war. Not too half
bad.

I think that transports didn't get the same treatment for a number of
reasons. Most transport types didn't have options which afforded
greatly increased power, and the load carrying performance of
airplanes at that time was limited by available power more than
anything else - you'd run out of payload weight available before you
ran out of payload volume. Getting more payload required a whole new
airplane. The C-46 was considerable bigger than the C-47 it
supplanted.

That being said, I suppose you could make a case that DOuglas did
start a program of stretching transports with the DC-4-DC-6-DC-7
line.


I had originally thought of the Spitfire as a good example of stretching
when this question first came up. However, on reflection, there was very
little airframe stretch during the service life of this type which
contributed to its ability to maintain parity in air combat. Essentially
there were two major airframe changes (Mk.VIII and F.21), and two major
engine ones (2-stage supercharging in Merlin 60's, and introduction of the
Griffon). The basic Mk.I led to the Mk.II, Mk.V, and ultimately the Mk.IX.
The Mk.IX was essentially an interim type allowing use of the series 60
Merlin engine before the definitive Merlin powered Mk.VIII was ready. With
the introduction of the Griffon engine, the definitive Spitfire was to be
the F.21 (and followed by F.22, and F.24). Again, to facilitate early
introduction of the engine upgrade, an interim model was introduced, based
on the Mk.VIII, and called the Mk.XIV.


I have to disagree, a bit. (While the basic Spitfire Shape was
retained, the Griffon engined Spits were much different,
structurally. You couldn't make a Mk IX into a Mk XII with a
conversion kit. The wing structure also evolved quite a bit, as
well. (Wasn't the Mk VIII actually based on the Mk III, which was
to be a Merlin XX powered flavor that was abandined in favor of the Mk
V when it was decided that the 2-speed Merlins were better off being
put into Hurricanes? It's Rivet Counting, I know.)


But the most significant cause of the Spitfire's extended longevity was the
remarkable work of Ernest Hive's team at Derby in forcing more and more
power from the Merlin engine, and ultimately the successful installation of
the Griffon engine. Without the engineering brilliance of Rolls Royce, the
Spitfire, as a contemporary fighter, would have become obsolescent by
1941-42.


T'warnt so mach Hives as Stanley Hooker, and his almost mystical
ability to squeeze that last bit of efficiency out of a supercharger.
Not only did he develop teh improved blowers for teh XX adn 40 series
engines, but he came up with the 2-stage blower for the 60 Series and
up, which was what transformed the Merlin from a good engine to a
classic. Two stage blowers weren't new, by any means - the U.S. was
very fond of them in the turbosupercharged R1820s and R1830s used in
the B-17 and B-24, and the V1710 installations on the P-38 and the
prototype P-39. (It was deleted from teh P-39 because there wasn't
room for both the turbosupercharger and the requisite intercoolers,
and installed drag on a tiny airframe like an Airacobra went through
the roof.) and the mechanically driven second stages of the Wildcat's
R1830 and the Hellcat & Corsair's R2800s - but they tended to be
complicated and space-intensive, with teh auxiliarry stage blower
driven at its own optimum speed by a separate drive. Hooker figured
that if he sized things just right, he could have both blowers on the
same shaft, turning at the same speed, and have them match throught th
eperformace range of the engine. And he made it work, with nothing
more than slide rules and graph paper.
Before the 2 stage Merlin appeared, The folks planning Brit War
Production were getting ready to close down Merlin production in favor
of its intended followons - the Sabre and the Vulture. (The Griffon
was another Rolls private venture) It's a good thig that didn't
happen.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
 




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