Geoffrey Sinclair wrote:

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.

I suspect they meant it wasn't defined by the 'armament fitted' in the
wing. The something else was probably the slight change in the landing
gear angle, as well as the strengthening.

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

Again, I suspect these refer to armament differences, i.e. 8 x .303, 2 x
20mm + 4 x .303, and 4 x 20mm respectively.

snip Mk. VI and Mk. VII data

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.

snip PR data

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.

snip fuel weights

Price says the Mk. I was designed to take either the two-blade wooden FP
prop or three blade metal two-pitch prop, and ballast had to be provided
accordingly. With the wooden prop (83 lb. vs. ca. 350 lb. for the metal
prop), 135 lb. of lead ballast had to be carried in the nose, on both
sides of the front of the engine at the bottom, roughly under the first
two cylinders and the aft end of the coolant tank. He includes a picture
showing the weights installed. By the time the MK.V came around the CS
prop was standard, which I believe was even heavier (can't find the figure
yet).

As always, thanks for posting the data.

Guy