De Havilland Mosquito (Wood vs. Metal)

[Admiral Beez]

Wouldn't that be the Hornet?

Or the I.Ae.24 Calquín.

 

[Shortround6]

1935 Walrus, also metal. Saunders-Roe built some wooden hulled versions during the war to save on light alloy.

 

[Zipper730]

Wouldn't that be the Hornet?

Not exactly: The Hornet had metal skins with wooden construction (I'm not sure if the whole skin was metal or not, but it had some). I was describing a plane that was of metallic construction.

Something from a boat building site . . . . Now as indicated in the chart, the weight of aluminum will depend on what alloy type of aluminum we're talking about. 2024 will generally be lighter than 7075 but heavier than 6061.

Now this looks pretty useful though I'm not sure how to determine the surface area for a complex shape like an airplane and the various frames and stringers. Off memory, I only remember the surface area for triangles (1/2bh), rectangles (lw), circles (πr^2), cubes (6a^2), spheres (4πr^2), probably cylinders (2πrh), and I forgot how to do trapezoids, though I can probably find that one.

As for the alloy-types: I thought 7075 was used only by the Japanese during the course of WWII.

What was used on most American & British combat aircraft?

Yeah, but most aircraft skins are anywhere from .032" to .040" thick, not 1/8 (.125).

I assume if the thickness was brought down by 1/2 then the mass would go down accordingly right?

There WAS a post WWII aircraft that was VERY Mosquito-like, build of Aluminum. It was the FMA I.Ae.30 Nancu. . . . It had a pair of Merlins, was faster than any Mosquito, and empty, was 13,686 lbs. Loaded was 16,755 lbs. Max speed 460 mph. Cruise 310 mph.

That's quite impressive, from the standpoint of weight (the Mosquito seemed to be around 14000 lbs. empty) and performance. I assume it lacked the volume because it was skinnier (and it lacked the bomb-bay). Do you have any idea of what load-factor it was stressed for?

This is always a tremendously difficult question to solve on any topic, I heartily recommend to you a book by J. E. Gordon called "The New Science of Strong Materials."

I'll order it when I get the chance...

Gordon reflects that it was "one of Gods little jokes" that the SPECIFIC stiffness of virtually all usable structural materials is nearly identical.

That is pretty ironic...

Wing flexure or fuselage twist would be two key metrics which essentially would produce an aircraft of exactly the same weight regardless of if they were made of iron or balsa wood!

I assume the need to build in resistance to this variable would drive up weight a bit.[/QUOTE]

 

[nuuumannn]

But did de Havilland have the production facilities to produce aluminium Mosquitoes?

And the inexperience of Supermarine slowed the transition from prototype to production.

Wuzak makes good points here. The essential point behind the Mosquito was that it was manufactured out of non-strategic materials and utilised skills in use by de Havilland and an external workforce to the aviation industry, such as cabinet makers and coach builders. Wuzak also raises a good point about de Havilland's work force and its skill base. Sheet metal work is a vastly different discipline to building wooden aircraft the way DH built the Comet, Albatross and Mosquito and training the workforce would have taken time. In saying that however, the Mosquito has a lot of aluminium in it, although very little of that is structural.

 

[FLYBOYJ]

Now this looks pretty useful though I'm not sure how to determine the surface area for a complex shape like an airplane and the various frames and stringers. Off memory, I only remember the surface area for triangles (1/2bh), rectangles (lw), circles (πr^2), cubes (6a^2), spheres (4πr^2), probably cylinders (2πrh), and I forgot how to do trapezoids, though I can probably find that one.

As for the alloy-types: I thought 7075 was used only by the Japanese during the course of WWII.

What was used on most American & British combat aircraft?

I think 2024 (Back then it was 24T) and 6061was found on most British and US aircraft. 7075 was adopted by the US towards the end of WW2 IIRC. The Japanese id use a lot of 7075 but the alloy was known by other countries

 

[wuzak]

In saying that however, the Mosquito has a lot of aluminium in it, although very little of that is structural.

The engine cowlings were aluminium, IIRC.

 

[wuzak]

Man, I get chewed out for anti British bias?
View attachment 670885
"Much of the airframe was composed of alclad, while detailed fittings were fabricated from stainless steel; metallic objects were anodised as an anti-corrosion measure. While the hull a sheet metal covering, the wings were covered with fabric"

This dates back the Southhampton series
View attachment 670886
"The Southampton's structure was revised substantially over successive batches. The Southampton Mk I had both its hull and its wings manufactured from wood, while the Southampton Mk II had a hull with a single thickness of metal (duralumin) (the Mk I had a double wooden bottom); this change gave an effective weight saving of 900 lb (410 kg) (of this 900 lb, 500 lb (230 kg) represented the lighter hull, while the remaining 400 lb (180 kg) represented the weight of water that could be soaked up by the wooden hull) allowing for an increase in range of approximately 200 mi (320 km).[7]​ All metallic elements were anodised to deter corrosion. During 1929, 24 of the Southampton Mk Is were converted by having newly-built metal hulls replacing the wooden ones.[7]​ Later on, the type was also furnished with metal propellers produced by Leitner-Watts.[9]​ Some of the later aircraft were built with metal wings and were probably designated as Southampton Mk III, although this designation's usage has been disputed."

There was an intermediate stop The Supermarine Scapa
View attachment 670887
The Scapa hull was an all-metal structure, while the wing and tail surfaces had metal structure with fabric covering.

Making water tight flying boat hulls is a lot different than making land planes but the Spitfire was a long long way from being Supermarine's introduction to metal construction.

Were these stressed skin designs?

 

[Shortround6]

Were these stressed skin designs?

wings were fabric covered but metal spars and ribs.
Hull was metal framework with metal skin, it may not be stressed skin but having to put sealant in every joint of skin plating and building a water tight hull does require some metal working experience.

Point is that the workmen are going to be used to using rivet guns and other metal working tools, not wood working tools.

Flying boat constructions was never the mass production that landplanes were

 

[nuuumannn]

The engine cowlings were aluminium, IIRC.

Not just the cowls, the entire nacelles were metal, as were the undercarriage doors, radiator housings, tail cone aft of the hori stab, elevators and ailerons (just the rudder was fabric), trim tabs, various removable panels on the fuselage and wings, and on the FB variants the nose cone and under fuselage gun panel, not to forget the undercarriage, engine mounts, structural braces within the fuselage, hundreds of miscellaneous fittings and things beneath the skin...

 

[nuuumannn]

Man, I get chewed out for anti British bias?

Heh heh... So you should...

 

[Howard Gibson]

This is always a tremendously difficult question to solve on any topic, I heartily recommend to you a book by J. E. Gordon called "The New Science of Strong Materials." It is very light reading and is a "popular science" book which requires no special training at all to appreciate, but will give you a dramatically better understanding of materials and structures. Its on the required reading list for almost all good 1st year engineering courses.

I strongly agree with your recommendation of J.E. Gordon's book "The New Science of Strong Materials". He also wrote a book called "Structures, or why things don't fall down". Basically, it's more of the same. He had an interesting fascination with bias cut material in ladies dresses.

We need to distinguish between non-strategic materials, and non-exotic materials. The Germans, and to a lesser extent the Japanese, wanted to build wood aircraft. They had no access to balsa.

The Mosquito's fuselage and wing surfaces were something like 5/8" thick. It was a thick balsa core sandwiched between layers of spruce. This is a modern composite structure. Balsa still is used today as the matrix layer in composite structures. A lot of cross country skis are carbon or glass fibre enclosing a balsa core.

Google composite balsa panel

If you are building a tubular truss structure, steel, titanium, aluminium and magnesium are in a line, with the same ratios of elastic modulus versus mass. You should build using the cheapest, most easily fabricated material.

If you are building a cantilever structure loaded in bending, for a given weight, aluminium beams will be thicker and stiffer than steel ones. The stresses that will make this structure break, are several orders of magnitude more complicated to manage. On the de Havilland Hornets, the upper wing skin was spruce/balsa/spruce composite, and the bottom face was aluminium. The much thicker composite structure was more resistant to buckling, which is how most structures fail in compression.,

I have specified beryllium for some scanner mirrors. Beryllium is about half again the stiffness of steel, and the density of magnesium. It is also poisonous as all hell, and very few people are willing to machine it. The mirrors were about $10K each. If you were to try to eat one, the immediate threat to your health would be blunt trauma.

 

[WARSPITER]

A balsa P-39 should easily reach 40 to 45 thousand feet. The tumbling and spin problems would be less violent, more like a falling leaf. My balsa flying model proves this.

It could also be a lifesaver in winter at a forward airfield where fuel for a fire is needed quickly (jumps behind coffee table to hide as he has no coat or balsa P-39
today and it's cold outside).

 

[Milosh]

Mosquito construction > photos and drawings

Mosquito References

The picture you see above was forwarded to me by a hobby friend. It has been taken on a model show in Spain. The decals you see are Uschi´s "Ronny Bar Edition". We have quite some contrast between the bright and the dark panels and it does look very pleasing indeed. Maybe one could discuss the...

www.uschivdr.com

There was also one on the Hornet but can't find now.

 

[Reluctant Poster]

Man, I get chewed out for anti British bias?
View attachment 670885
"Much of the airframe was composed of alclad, while detailed fittings were fabricated from stainless steel; metallic objects were anodised as an anti-corrosion measure. While the hull a sheet metal covering, the wings were covered with fabric"

This dates back the Southhampton series
View attachment 670886
"The Southampton's structure was revised substantially over successive batches. The Southampton Mk I had both its hull and its wings manufactured from wood, while the Southampton Mk II had a hull with a single thickness of metal (duralumin) (the Mk I had a double wooden bottom); this change gave an effective weight saving of 900 lb (410 kg) (of this 900 lb, 500 lb (230 kg) represented the lighter hull, while the remaining 400 lb (180 kg) represented the weight of water that could be soaked up by the wooden hull) allowing for an increase in range of approximately 200 mi (320 km).[7]​ All metallic elements were anodised to deter corrosion. During 1929, 24 of the Southampton Mk Is were converted by having newly-built metal hulls replacing the wooden ones.[7]​ Later on, the type was also furnished with metal propellers produced by Leitner-Watts.[9]​ Some of the later aircraft were built with metal wings and were probably designated as Southampton Mk III, although this designation's usage has been disputed."

There was an intermediate stop The Supermarine Scapa
View attachment 670887
The Scapa hull was an all-metal structure, while the wing and tail surfaces had metal structure with fabric covering.

Making water tight flying boat hulls is a lot different than making land planes but the Spitfire was a long long way from being Supermarine's introduction to metal construction.

If anyone wants to learn about Supermarine's construction methods (in quite a bit of detail) I suggest reading Spitfire odyssey by C.R. Russell
Amazon product ASIN 0946184186The author started with Supermarine as a 'tinbasher' in 1936 building Seagull (aka Walrus) components then Stranraer hulls before moving on to Spitfires. It is obvious from the book that Supermarine was well versed in metal construction before the Spitfire entered production. According to Russell the Spitfire fuselage was straight forward to construct but there were problems with the wings which caused delays.

Supermarine (and the British aircraft industry in general) was operating under extreme time constraints and the rapid expansion entailed produced production problems. America had over 2 years to observe and prepare and even then the Arsenal of Democracy took a while to get going.

 

[Reluctant Poster]

That book was recommended to me by a university prof 40 years ago and I think I still have it somewhere - an excellent read.

As to the plywood thicknesses on the Mosquito, it ranged from 1.5 to 3mm on the fuselage and up to I think 5mm on the mainplane. Of course, the fuselage had an inner skin, typically 1.5mm thick, and an outer skin of varying thicknesses and grain patterns separated by 7/16 inches of balsa filler.

There was a thread on this topic a few years back. Metal Mosquito built massively in the US
And, somewhat related: What if the P-38 was made of plywood a la Mosquito?

The construction of the Mosquito was quite sophisticated using the different qualities of different types of woods to full advantage. Really the precursor to composites now used.

 

[Reluctant Poster]

The construction of the Mosquito was quite sophisticated using the different qualities of different types of woods to full advantage. Really the precursor to composites now used.

Hers another video showing construction of the Mosquito. Very clever indeed.

 

[Crimea_River]

The last video was produced by the society on whose board I serve.

 

[GregP]

Fuselage is around 1/4" from memory. But, that's a sandwich of ply and balsa. From a subjective point of the panels I lifted, I didn't find them much different to what I would have expected from an aluminium one. But, that's only panels, and my highly uncalibrated arm...

From flying radio controlled aircraft for 20+ years, I can tell you a structure of balsa and ply can be made VERY strong and stiff. Much more so than one would think.

 

[Reluctant Poster]

Were these stressed skin designs?

The bottom of a flying boat hull has to take the impact of landing so it must by nature be stressed skin.

 

[Shortround6]

The bottom of a flying boat hull has to take the impact of landing so it must by nature be stressed skin.

We throw around words/terms with a little appreciation for how different two different structures can be and yet fall into the same general catagory.

All stressed skin means is that some/any of the loads (flying, landing, whatever) are borne by the skin. One plane may have the skin bearing 5% of the load and another plane may have the "skin" supporting over 50% of the load.
I don't know what you call some jets where the "skin" is milled on the inside to vary the thickness on the same "plate" in various areas before the plate is bent/formed on hydraulic presses. I would guess it is still stressed skin.
If a fabric covered plane gets any strength from the fabric/material being stretched over the frame and putting a compression load on the framework it might be considered stressed skin. (a lot if flying models are actually stressed skin)
Some (most?) of the old wooden flying boats used double diagonal planking with the planks at angles to each other and covering multiple frames. the "skin" was part of the structure.

Pretty sure this plane used stress skin construction.

After the publicity photos it and/or it's two sisters were covered in fabric. Plane also used 40-50 gallons of resin before the fabric went on.