Bomber main spar question.

The Lancaster's infamous main spar appeared as two giant girders running across the floor of the aircraft which crew had to clamber over.

Now this makes Sense as the Lancaster was a low-wing bomber. But what about high wing planes such as the b-24 liberator? Presumably the girders still appeared, but they were just in the ceiling of the aircraft.

But what about mid-winged bombers? Surely the spar must have come through as a complete obstruction of the center of the fuselage.

I assume all bomber aircraft had the wing effectively as one structure of two wings. Otherwise there just wouldn't be the strength in the wing. You couldn't have a wing that was just not attached in any way to the other Wing.

Excuse my ignorance if I'm talking rubbish but I would like to know other more experienced members knowledge on this.

In most cases the wing was in three sections with the centre section integral with a section of the fuselage.

In the case of the Lanc (which is actually mid wing) the fuselage unbolts in front of the windscreen, in front of the front spar, behind the front spar and then back near the door. The wing unbolts just outboard of the inboard engines and has removable wing tips. Search for Lancaster on this forum and you will find a scan of my Lanc Vol 1

In the case of the B25 the wing is in three pieces and unbolts outboard of the engines. Like the Lanc the wing carries through the fuselage and there is a narrow crawl space above.

The B-17 and Martin B-26, A-20 and A-26 have a four section wing which bolts to the fuselage sides and joins outboard of the engines (outboard engines on B-17). There is a carry through structure in the fuselage that is very bulky though on the Marauder there is a lot of room below it and it is relatively easy to move from front to rear.

EDIT - the more I think on it the more I get the feeling the B-17 wing is like the B-24 and B-29 wings - integral with the fuselage

B-24 and B-29 wings are integral with the fuselage and unbolt outboard of the outboard engines from memory.

Blenheims and Beauforts and Beaufighters all have a three piece wing and the Fuselage fits above it with bomb/gun bays and skirts below.

I have a manual that shows the production breaks of the US bombers which I will find when I return home mid next week and post the pictures from that to show how the B-17, B-24 and B-29 come apart - in the case of both of those some of the production breaks were riveted together, not bolted, so are not easily separated.

From memory the P-61 was not made for repairs with the wing centre section and all the fuselage except the nose being integral. The powerplants tail and booms were the only things that could be replaced "in the field". Everything else was a major repair.

Here's a B-25 wing spar looking forward from the aft fuselage. The wing spar is the upper section, aft bomb bay bulk head is the lower section.
(http://imgur.com/C5ue7Fo)
View: https://imgur.com/C5ue7Fo

Here are the production break drawings for many of the US aircraft of ww2. My apologies for some pages being distorted but I was in a hurry photographing these pages. The P-40, like several other aircraft, was split horizontally but that is not shown. The C-45 is not shown but the AT-11 shared many parts and the same concepts.

Remember production breaks are not repair breaks. Many of the parts were not designed to be separated after assy - the A-20 fuselage cannot be split into the three production sections for repair without jigs, likewise the P-40 fuselage and many others.

Main assemblies for repairs are shown in the various -2 and -3 manuals - many of which are on this site.

From the parts catalogue this is the official service breakdown of the Lancaster. I was sure the wing tips were separate but I guess my memory is not as good as I thought it was.