Originally Posted by
JDNSW
A couple of errors of fact - no Hurricanes used a wooden structure, although early Hurricane 1s were fabric covered and the fabric covered fuselage was retained for all Hurricanes, but with stressed skin metal wings. This contrasts with the all metal stressed skin airframe of the Spitfire.
There were around 16,000 Hurricanes built, compared to around 20,000 Spitfires, so the discrepancy was not all that great. But the Hurricane is much more easily maintained than the Spitfire, mainly due to the elliptical plan wing on the latter which means every bit of metal in the wing has a three dimensional curve and is different from every other bit.
Getting back to the subject of firewalls. Another possibility is that the pressed firewalls were the production limiting factor (once the press is going flat out you can't increase production without making another die, which is both slow and expensive), and perhaps a few alloy firewalls were made from time to time just to speed up a batch for a particular order which was otherwise going to be late. The supplemental production would have been a lot slower than the pressed production, so they would not go into sequential chassis numbers, but would get slotted in as each one was finished.
John