Guy Alcala wrote:

Geoffrey Sinclair wrote:

snip

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

Okay, I've got Price's "The Spitfire Story," which is very helpful. Here's
what Wing Commander Tuttle, former head of the PRU, told Price about the
handling of the hand-modified PR.1Ds (normal 84 gallons forward, 114 gallons
in the wing L.E., 29 gallons behind the pilot, plus two cameras further back
(but no radio):

"You could not fly it straight and level for the first half hour or hour after
takeoff. Until you had emptied the rear tank, the aircraft hunted the whole
time. The center of gravity was so far back you couldn't control it. It was
the sort of thing that would never have got in during peacetime, but war is
another matter."

What may be barely acceptable for a PR bird flying solo in VFR conditions by
experienced pilots not making any radical maneuvers, is definitely
unacceptable for formation or combat flying by less experienced pilots.
Later, the production PR.1Ds had the aft tank removed, the radio reinstalled,
and the L.E. tanks enlarged from 57 to 66.5 gallons each side, to improve the
handling (L.E. tanks were forward of the datum). They also got somewhat
heavier Merlin 45s.

Guy