British escort fighter--what might it have been like?

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Do you have any info on the empty weight of those 108 gallon paper drop tanks? They are reputed to be quite light, but I have never found an exact figure. The 75 gallon metal tank weighed 50 to 60 lbs empty, depending on the source, and the 110 gallon metal tank weighed about 85 lbs empty.
 
Two things I take from that.
1.The distance to the target flown by both bombers and fighters is much longer than the straight line distance to the target.

The websites for the 303rd and 451st Bomb Groups contains the planned route map for the mission. Based on the missions I reviewed, the distance flown was sometimes 20% or more than the straight line distance. The 25 June 1943 mission to Hamburg by the 303rd, for example, had a planned route distance of about 1,051 miles, as compared to a straight line out and back distance of about 880 miles.

(The ORBs for 77 Squadron contain the route flown from 1943 onward, so the planned route distance for that Bomber Command squadron can be calculated from that route info.)
 
So the space between ribs 1 & 4 was not used for fuel tankage on any Spitfire variant so far as I can see. One thing that does possible intrude into that space is the undercarriage mounting which would attach to the rear of the wing spar.

This video

View: https://www.youtube.com/watch?v=Op8U7KQLxEQ&t=685s
mentions that near the wing root on the starboard side there is the gun camera, and on some early Mk IX on the port side there is an opening for a fuel cooler.
 
I don't know the weight but a man could hold an empty one over his head.
 
The same applied to the Spitfire, changing the rear tanks around and having the 33G on top and 42G on the bottom gives the Spit another 10G internal to play with and once the 60 series comes into production the power to lift the bigger 100G or 108-110G external extending it's range or loiter time.
 
I do not have the weight for the bare 108 USgal paper tank, but the British version weighed 70 lbs with the fairing/pylon as used on the Hurricane. The 70 lbs includes all the bits except those in the wing that remained when the tank and fairing/pylon were dropped. This weight is from the modifications list for the Hurricane.

The 45 Impgal paper tank weighed 29 lbs bare, or 52 lbs including the fairing/pylon as used on the Hurricane. The 52 lbs includes all the bits except those in the wing that remained when the tank and fairing/pylon were dropped. The 52 lbs weight is from the modifications list for the Hurricane. The 29 lbs weight for the bare tank is from an industry magazine of the period.
 
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29 lbs for 54 US gallons (45 Imperial gallons) implies an empty weight of 58 lbs for the 108 US gallon paper tank, assuming the same ratio of empty weight to fuel weight (29 lbs / 324 lbs [54 gallons * 6 lbs per gallon] = 0.0895). That's 27 lbs lighter than the 110 US gallon metal tank. That doesn't seem to be as big a weight savings as I would have thought.
 
The weight isn't surprising. Glued laminated Kraft paper has a density somewhere between 30lb-40lb/cf. the technology is still in use today for construction, such as concrete formwork.


(No affiliation to the linked company)

These articles were informative


 
I was thinking the increase in tank weight would be proportional to the increased surface area (simplest is surface area of sphere - 4πr^2, so doubling volume increases surface area 2^0.5 or about 40%....call it 50% to allow increase in structure to attach to airframe. (Things like filler cap, etc are all identical) So <45lbs for 108 US gallon tank.. Not a huge difference, but we're gram counting here.
 
I have read that the US 108 USgal design variant weighed a bit more than the original UK type as there was additional hardware (dual filling ports and different hanger hardware for example) incorporated in the US design, but I have never been able to find the weight of the US variant.

The weights I gave above are for the original UK paper tanks.
 

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