Guy alcala wrote in message

Vader states that the Mk VIIIs had the 'C' wing, which implies that
the Mk. IXs should have been able to be given LE tanks with little
difficulty. I'm under the impression that the substantive changes to
the Mk. VII/VIII were in the fuselage, and except for the tanks the
wings were identical. Does anyone actually KNOW what the
structural/internal changes were from the Mk.V/IX etc. to the Mk.
VII/VIII? We all know about the tail wheel, but there had to be more
than that.


More information from Morgan and Shacklady,
Spitfire weights, tare / take off / maximum

VA 4,981 / 6,416 / 6,700
VB 5,065 / 6,622 / 6,700
VC (B wing) 5,081 / 6,785 / 7,300
VC (C Wing) 5,081 / 7,106.5 / 7,300

So if this is correct an extra 16 pounds was added, presumably
to the fuselage, between the B and C versions. The book is also
saying the VC version is not defined by the wings fitted, A or B
or C wings, there is something else. The VC was a definite
change, and able to carry 600 pounds more weight, presumably
mainly by strengthening the undercarriage.

The second production VC AA874 (Merlin 45) was weighed with
A, then B then C wings, weights in pounds, CoG in inches

wing / tare / tare CoG / all up weight / all up CoG
A / 5,048 / 2.31 / 6,499 / 10.9
B / 5,048 / 2.31 / 6,737 / 10.9
C / 5,048 / 2.31 / 6,969 / 7.65

The mark VI, the pressure cabin version of the V, weights,

tare 5,227 pounds, take off 6,797, maximum 6,850.

AB450 was the prototype mark VII. It was a standard mark V
with the following modifications, extended wing tips, 4 bladed
propeller, retractable tail wheel, tail parachute fin guard, Merlin
61 with twin underwing radiators.

The certificate of design general description was "This
aeroplane is the prototype of the F Mk VII and F Mk VIII
production Spitfires. Components of existing types with some
modifications as used as indicated. Fuselage Spitfire Mk VI
with the forward bay reinforced for Merlin 61 engine. Spitfire
F Mk 20 tail unit, Spitfire Mk V elevator and rudder. Mainplane
Spitfire F VC with spar flanges reinforced and lead ballast
added in outer portions of the wings. Main chassis Spitfire
F Mk VC leg and support structure. Spitfire F Mk VII production
wheel and tyre equipment. Tail chassis, Spitfire F Mk VII
production. Tare weight 5,201 pounds, maximum all up 8,000."

Production VII tare weight 5,947 pounds or 5,887 pounds,
depending on the hood used, take off 7,928 pounds, maximum
8,000 pounds. This indicates there probably was some fuselage
strengthening between the prototype and production.

Morgan and Shacklady state the mark VIII had the fuselage further
strengthened over the mark VII, with the VIII weights as Tare 5,806
pounds, take off 7,779 pounds maximum 8,000 pounds. This looks
like the VII without the extra wing tips and pressure cabin gear.

Mark VIII 2 cannon and 4 browning, weights in pounds and CG in
inches tare 5,861 and 0.2 landing 6,710 and 4.9, normal load
7,831 and 5.9, 30 gallon overload tank 8,131 and 6.4, 90
gallon overload tank 8,648 and 7.0. The figures are repeated
for a 4 cannon version, interestingly tare weight is the same
but all the other weights are around 200 pounds more, and the
CG figures 0.1 to 0.3 greater. CG measured aft of datum.
Since a pair of 20 mm cannons came in at around 200 pounds
and 4 brownings at around 100 pounds this would seem to
indicate tare weights are with the armament removed.

F Mark IX tare 5,816 pounds, take off 7,295.5 pounds, maximum
7,500 pounds. After notes about overload tanks and bombs comes
the entry "ballast 92.5".

F IXE tare 5,816, take off 7,181.5, max 7,500.

Perhaps a look at the PR IV which was the PR version of the V
and normally had the cameras located behind the cockpit, they
also carried radio, TR 1133 or 1143.

Tankage front fuselage 48 upper 37 lower, same as mark V,
2 x wing leading edge tanks 66.5 gallons each, total 218
gallons. Oil tank 18 gallons in port wing between ribs 9 and 12.

Tare weight 4,935 pounds, take off weight 7,148 pounds (W),
7,155 (X), 7,119.5 (Y). Max permissible 6,500 pounds (yes
six thousand five hundred, a typo I presume). Tail ballast 17.5
pounds.

W version 2 x F8 20 inch split vertical fanned between fuselage
frames 13 and 15 inclined 10 degrees to the vertical and 20
degrees to each other.

X version 2 F24 14 split vertical fanned and 1 F24 8 or 14 inch
oblique mounted as W version with oblique over front F24.
Inclined 8.5 degrees to the vertical and 17 degrees to each other.

Y version, F52 36 inch vertical used only for bomb damage
assessment, mounted between frames 13 and 14.

PR VII, same as IV except,

Tankage front fuselage 48 upper 37 lower, same as mark V,
rear fuselage 29, total 114. Oil 5.8 gallon, in tank under engine.
No radio. Weights tare 4,985 pounds, take off 6,584 pounds,
maximum 6,590. CoG moved forward as fuel was consumed.

Cameras, G installation, F24 5 or 8 inch vertical (front) and F24
8 or 14 inch vertical (rear) between frames 13 and 14 and 1 F24
8 or 14 inch oblique mounted above front camera.

Some PR VIII had A wing armament.

From Spitfire by Peter Moss, the initial hand converted PR
versions from Spitfire I had a 29 gallon fuel tank under the
pilot's seat and a 64 pound camera installation behind
the cockpit, no radio though. It all worked because there
was 32 pounds of removable ballast in the tail to compensate
for the mark I moving to a heavier 3 bladed propeller.

If the ballast figures are correct there is obviously some room
for extra fuselage tanks, the maximum take off weight comes
into play though. It appears 315 British gallons of 100 octane
fuel comes to 2,240 pounds, for 80 Octane fuel 300 gallons
weigh 2,240 pounds.

Geoffrey Sinclair
Remove the nb for email.