Stretching WW2 Designs

"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