All metal Mosquito ??

[Markus Becker]

WI the Mosquito had been made out of aluminium instead of various types of wood? IIRC duraluminium is lighter/strong than wood, meaning an all-metal Mossi would have been even better, or am I overlooking something?

I do that an aluminium Mosquito wasn´t an option as there was not enough aluminium, so this is a purely theoretical question.

[Graham Boak]

Theoretically, it would have been lighter. Practically, it would have depended upon the design team's experience with aluminium.

I don't think it was an actual shortage of the metal, though one would have been feared, but a willingness to use manufacturing sources outside of the already overstretched aircraft industry. You were better off using trained woodworkers than having to train new metal fitters.

[MarkRS]

Actually the average density of Balsa wood is 170 kg/m3 which is far less than Aluminium at 2700 kg/m3. Even when you take into account that Balsa is far weaker than Aluminium, The strength to weight ratio of Balsa is about 40% better. So an Aluminium Mosquito would have been heavier and slower.

[Kutscha]

Originally Posted by MarkRS

Actually the average density of Balsa wood is 170 kg/m3 which is far less than Aluminium at 2700 kg/m3. Even when you take into account that Balsa is far weaker than Aluminium, The strength to weight ratio of Balsa is about 40% better. So an Aluminium Mosquito would have been heavier and slower.

Weight of a 24" x 60" panel:

Aluminum alloy - 0.91lb (0.063" #26 and #27)

Balsa sandwich - 10.2lb (2 x 1/8" plywood + 1/4" balsa @ 8lb/cf)

Australian propaganda video
http://www.youtube.com/watch?v=c7cVvYdLeek

[MarkRS]

Originally Posted by Kutscha

Weight of a 24" x 60" panel:

Aluminum alloy - 0.91lb (0.063" #26 and #27)

Balsa sandwich - 10.2lb (2 x 1/8" plywood + 1/4" balsa @ 8lb/cf)

Australian propaganda video
http://www.youtube.com/watch?v=c7cVvYdLeek

The weight of the balsa sandwich is about right, but the aluminium calculation is 10x out. Should be 9.1lb. And you are not calculating like with like or calculating what was available in 1940. Aluminium composites were not in use. Wood composites were. An unstiffened sheet of aluminium that size 1/16" thick would weigh 9.5 lb by itself.
The ratio also changes if you make the plywood thinner and the balsa thicker. For example 1/16" ply and 1/2" balsa comes out to about 8lb and is probably stronger.
Today, if you want to go really light, you use epoxy graphite with a protective surface of Kevlar against impact damage.

[Kutscha]

Right, I messed up.

A 0.0641" sheet (2'x5') of aluminum weighs 9.3lbs according to the Machinery's Hand Book.

Sure it is like with like, as that is the skin of the a/c.

More research has turned up, 1/16" and 5/64" plywood and 7/16" balsa.
http://users.skynet.be/BAMRS/dh103/f...nstruction.htm

So as you say 8lb or a little less.

[Graham Boak]

No. Wooden aircraft are heavier than metal aircraft (and the main component of the Mosquito was not balsa but Spruce.) The main reason for this appears to be that the strength of the wood cannot be relied upon, so greater safety factors are required. Directly comparable cases are the wings of Soviet fighters, which changed from wooden spars to metal ones once the supplies of aluminium were sufficient. Attempts to create wooden versions of aircraft designed in metal end up heavier - see the Nakajima Ki.84 for an example.

One other advantage of metal is that it provides more internal space than the thick skins and internal structure of wooden aircraft.

Heavier aircraft are not necessarily slower, as weight has little effect on top speed. The wooden aircraft may be faster, because of a smoother external surface without steps and gaps between the panelling.

[MarkRS]

Sorry to disagree, but Mosquitos were not ordinary aircraft. They were the highest of high tech at the time. They were made from wood on purpose because it made them lighter. And they were pushing the limits on safety factors. Spruce was used where better bending strength was needed, the rest was Balsa and plywood. Spruce is also one of the lighter woods, 450 kg/m3. Its improved strength over Balsa retains the same 40% strength to weight advantage over Aluminium. These aircraft were built using the same principles as modern composite aircraft today. Assuming the same aerodynamics, weight is highly relevant to top speed and acceleration. The Mosquito could fly away from a Spitfire carrying the same payload as a B17.

[MarkRS]

You get a really good description of the construction of the Mosquito in:
De Havilland Mosquito: An Illistrated History By Ian Thirsk.

http://books.google.com/books?id=6nb...page&q&f=false

Page 39 onward.

[Empiricist]

Originally Posted by MarkRS

Sorry to disagree, but Mosquitos were not ordinary aircraft. They were the highest of high tech at the time.

You did good job in this thread. You are absolutely right. The Mosquito was neither better nor worse than all-metal planes of that era. But in the field of wooden airframes it was high-tech aircraft in the 1940s circumstances.