What if the P-38 was made of plywood a la Mosquito?

[swampyankee]

Of course it was several years later than the P-38.
It also suffered from being overweight, delayed development and was designed around an engine that never made it to flight status (or even test bench?)
The intended "buy" changed quantity several times and finally resulted in just the two prototypes.

XP-77. Contracting out construction of a wooden airplane to a company which had no experience building in wood was probably not the best choice, even disregarding the fact that the lightweight fighter concept (WW2 edition) was not likely to be a rousing success (on the other hand, Bell got the XP-77 built; neither Douglas [XP-48] nor Tucker [who? XP-57] completed prototypes)

Was any US company building any wooden aircraft except for general aviation use in the 1930s?

 

[Shortround6]

Was any US company building any wooden aircraft except for general aviation use in the 1930s?

Not to my knowledge, Wooden construction being essentially ended for commercial aircraft in the wake of the crash of TWA flight 599 in 1931, the Crash that killed Knute Rockne. Between government regulation and public demand for metal aircraft no new wooden commercial aircraft were built in the US.
even such aircraft as the Stinson Model A used metal spars.

Three 260hp Lycoming engines. Strangely one of these crashed in Australia in 1945 due to metal fatigue in the lower wing spar attachment points. The aircraft was about 8 years old at the time and been converted to a twin engine aircraft with P & W R-1340 engines.

Even such aircraft as the Stinson Reliant had changed to all metal framework by 1936.


The Military was not buying any wooden framed aircraft and hadn't for several years. They did use fabric covered metal structure.

 

[Elmas]

Some wooden planes, apparently of good design, were complete failures when properly tested

and some, good at the time of their appearance in the skies, were outdated when the war progressed

 

[pbehn]

There is a fundamental misunderstanding about the Mosquito which I believe comes from inexact use of English. Most descriptions state something like "de Havilland produced a lightweight wooden bomber design". This is actually two statements, they produced a lightweight design and also it was made from wood. The most important part of the lightweight design is its lack of defensive guns and small fuselage. I dont know how the Mosquito compared to the P51 in cooling drag/meredith effect but I suspect it was close. Other parameters like frontal area, wetted area and maybe others I havnt a clue about are from the design not from being madfrom wood. The Mosquito was made from very advanced materials, laminates and composites in well engineered proportions, they just happened to be from trees, but very special trees sourced around the world. As others have pointed out some planes became heavier using wood, I suppose it depends on what would you can get.



Does anyone know the cooling drag/frontal area/surface drag of the Mosquito and P-38 as a matter of interest?

 

[Shortround6]

The Mosquito didn't really have a great radiator setup. It wasn't bad but it wasn't in the same class as a P-51.

There is a bit of a trade off in that the Mosquito's radiator didn't add much, if any, to the frontal area of the aircraft. However the Mustangs larger expansion ratio of inlet to radiator area means a lower speed of air through the radiator matrix and since drag goes up (or down) with the square of the speed that is an important difference. Getting the exiting air to not only exit but do so with the least turbulence and change in direction is also important to low over all drag (or attempting to get actual thrust).

Mosquito construction also varied quite a bit depending on if you are talking about fuselage or wings.

The Mosquito probably had a better surface finish and quite possibly a better radiator installation than the P-38 but was a much larger aircraft in size. As already mentioned the P-38 was built to withstand a higher load factor.

 

[swampyankee]

Some wooden planes, apparently of good design, were complete failures when properly tested

and some, good at the time of their appearance in the skies, were outdated when the war progressed

..yet those old-fashioned, obsolescent trimotors, Savoia-Marchetti SM.79s were "[r]egarded by many as one of the finest torpedo bombers of the war, it served with distinction and was flown with courage and skill." (Savoia-Marchetti SM.79). I don't think "failure" would properly apply to them. The other aircraft is the SAI.207, a lightweight fighter. In general, around that time "lightweight fighter" was really just a synonym for "failure."

 

[Elmas]

Yes, SM 75 was not a failure: only obsolescent, in times where the development of aircrafts and engines was, if not on a weekly, almost on a monthly basis. But his successor, SM 84, was..

 

[tomo pauk]

The Mosquito didn't really have a great radiator setup. It wasn't bad but it wasn't in the same class as a P-51.

I'm afraid that is selling the Mosquito's radiator short. The system was copied on both sngle- and two-engined A/C (so was late Mustangs), and we can recall that Mustang's radiator was evolving significantly with any major type change. Radiator similar to Mosquitos was proposed by NACA as a drag-reducing feature for P-38.

 

[pbehn]

I'm afraid that is selling the Mosquito's radiator short. The system was copied on both sngle- and two-engined A/C (so was late Mustangs), and we can recall that Mustang's radiator was evolving significantly with any major type change. Radiator similar to Mosquitos was proposed by NACA as a drag-reducing feature for P-38.

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The Mosquito probably had a better surface finish and quite possibly a better radiator installation than the P-38 but was a much larger aircraft in size. As already mentioned the P-38 was built to withstand a higher load factor.

Great information SR and Tomo but I was responding to the thread subject along the lines of the following. If you give an expert modeller a million matchsticks he can produce wonderful models of the Taj Mahal, the White House, Buckingham Palace or The Titanic. If you give me a million matchsticks you will get various versions of a haystack with windows.

I didnt mention the cooling of the Mosquito to start a discussion of which is best but to show that it was up there with those of advanced fighters, this has nothing to do with whether it is mainly wood or metal used . The P51 system would not lend itself easily to a twin engined design and Mosquito's extended engine nacelles were not part of the design.

Similarly the surface drag of the Mosquito may or may not have been better than the P-38, the question is in some ways moot because by being close it shows how much de Havilland put into making it smooth, contours rounded and joints well finished. The Mosquito proved that a lightweight bomber could be made from wood, however other planes show that just building a plane from wood doesnt guarantee anything at all.

The diagram from Shortround showing the use of balsa, ash, birch, spruce, Douglas fir and plywood shows that these were carefully chosen materials. The Mosquito was designed by experts at what they did, they made racers and then they made military aircraft, using wood, was just a part of the story.

I dread to think of how many hundreds if not thousands of tons of trees were felled to produce even one ton of material suitable for an aircraft.

 

[bobbysocks]

the tropics and wooden airframes is probably why they buried all those spitfires in Burma........and SEE what happened...they are no longer there.






lol

 

[parsifal]

Thought this might be at least interesting. its an on line source detailing the progress of a long term restoration of Mosquito A-52-600.

Restoring an RAAF de Havilland DH.98 Mosquito PR Mk.XVI

de Havilland Mosquito A52-600 images and history

Elsewhere ive read accounts about this restoration. The outer skin was in a very bad way, but even after forty years of abuse the inner skin was more or less intact. it has since been decided however that the balsa sandwiching should be replaced, although the hardwood skin surrounding this sandwich is still okay. that has to be amazing in any body's estimation.

The guys at the RAAF museum are finding it slow going because of the specialist skill needed to undertake the restoration. Ive read also that there is still a faint hop this aircraft will be returned to flying condition, which makes the task much more challenging.....

 

[Old Wizard]

 

[FLYBOYJ]

Catching up to this late in the game. I've ranted about wood in the past. As a maintainer wood sucks, I hate inspecting and repairing it. Although there were many great aircraft made of wood, what you basically build is a "throw-away airplane." There are tons of discussions about this through out this forum.

As far as a wood P-38? Not going to happen. The area where the tail plane was connected to the booms were difficult to manufacture with aluminum, I could imagine trying to build the same structure out of wood.

 

[pbehn]

Catching up to this late in the game. I've ranted about wood in the past. As a maintainer wood sucks, I hate inspecting and repairing it. Although there were many great aircraft made of wood, what you basically build is a "throw-away airplane." There are tons of discussions about this through out this forum.

As far as a wood P-38? Not going to happen. The area where the tail plane was connected to the booms were difficult to manufacture with aluminum, I could imagine trying to build the same structure out of wood.

Great post FB. I found this in Wiki about the Dh 88 racer and the lengths taken, in a wooden structure, to produce an advanced design.

Quote
Aerodynamic efficiency was the design priority and it was therefore decided to use a thin wing of RAF34 section. This was not thick enough to contain spars of sufficient depth to carry the flight loads and so the wing skin would have to carry most of the loads. However, the complex curves required for aerodynamic efficiency could not be manufactured using plywood. A construction technique previously used for building lifeboats was adapted. The majority of the wing was covered using two layers of 2 inch (50mm) wide spruce planking laid diagonally across the wing, with the outer layer laid crosswise over the other. These strips were of variable thickness, according to the loads they carried, reducing over the span of the wing from 0.5 in (12.5mm) at the root to 0.14in (3.5mm) towards the tips. It was built as a single assembly around three box-spars located at 21, 40 and 65 percent chord: there was an intermediate spruce stringer between each pair of spars to prevent buckling. The ribs were made of birch ply and spruce. The outboard 6 ft (1.5m) were skinned with various thicknesses of ply because of the difficulty of machining spruce planking to less than 0.07in thickness. The leading edge, forward of the front spar, was also ply covered. The centre section was reinforced with two additional layers of 0.07 spruce.[8] This method of construction had been made possible only by the recent development of high-strength synthetic bonding resins and its success took many in the industry by surprise.[9]
unquote

In the 1930s and 40s and in time of war all aircraft were disposable. If the Merlin used in combat needed a rebuild after 250 hours how many aircraft had their engine rebuilt more than once? I never considered the question in the original post to literally make a P-38 out of wood, wood and metal are completely different and need different designs. I believe a twin engine fighter could have been produced but it would have looked like a Hornet. The point made previously deserves repeating, wood is not a miracle material, de Havilland really knew what they were doing not only in wood but also aerodynamics including cooling technology. Lockheed, by the same token, were not fools. Just building a P38 out of wood would result in a disaster, if it made a first flight I doubt it would make a first landing. The compressibility problems of the P-38 were new but not unique to the P 38 and wooden construction woulnt have helped.

As a guy who worked with steel and stainless steel all my life I have a view on how quality is maintained controlled and assured. This is always based on chemical analysis, heat number, lot number, item number (or similar). In various steel production methods the names change and the meaning changes slightly but the principle remains the same. When it comes to wood, I have no idea how they maintained quality assurance between trees on a material that changes so obviously that by grandmother used to say things were "dry as sticks". The performance difference of a living tree in a high wind, bending with no permanent (plastic) deformation, compared to the same tree when cut and dried splitting and splintering is akin to the difference between normalised steel and cast iron.

For those working in metals they had to develop new metals/treatments/processes but to those using wood they had to look for different woods and combine them in different ways.
,

 

[Ascent]

I would suggest that rather than a wooden plane you could think of the mosquito as a composite construction. It wouldn't have been possible to build without the glues and resins that had been developed.

Think of carbon fibre, that is layers of the fibre in a resin that bonds it together. That's what's different about the mosquito construction, it's not just blocks of wood screwed together.

 

[pbehn]

I agree Ascent but I don't know how the discussions went when a pilot was told to fly over Germany using two engines producing 2,500 HP joined together by plywood.

 

[Shortround6]

The Russian and American planes were also of a sort of composite construction. The Russians using phenol formaldehyde resin not just to stick parts together but to actually impregnate the wood.

The Langley light twin needed 50-60 gallons of resin.

However not all composites are the same. Fiberglass can vary tremendously depending on not only the resin/s but wither woven matting or "chopped" fiberglass is used, not to mention weight and number of layers of the glass matting.

One reason the US stopped using these construction methods was the large amount or resin which was needed for other war production and that the US (and Russian) methods needed large ovens to bake the pieces in making field repairs of small damage difficult. Either a weak spot was created or a large part/panel had to be replaced. In the Open cockpit trainer pictured earlier the entire fuselage was one piece and the wing another. On the wing you could NOT replace a rib and a few feet of skin in the field. You need a whole new wing OR access to an oven capable of holding the entire wing while the new parts and resin baked/bonded to the old parts.

The Mosquito was more conventional than that.

 

[FLYBOYJ]

I would suggest that rather than a wooden plane you could think of the mosquito as a composite construction. It wouldn't have been possible to build without the glues and resins that had been developed.

Think of carbon fibre, that is layers of the fibre in a resin that bonds it together. That's what's different about the mosquito construction, it's not just blocks of wood screwed together.

Totally wrong! The only common factor is you have glues and resins that bond to a base material, out side of that the whole process for lay-up and repair is entirely different. I work with carbon fiber and it doesn't rot in humidity. Although time consuming, carbon fiber is a lot easier to make repairs on, where wood structures are limited in size and the amount of repairs that could be made on a given area.

 

[swampyankee]

Totally wrong! I work with carbon fiber and it doesn't rot in humidity. Although time consuming, carbon fiber is a lot easier to make repairs on, where wood structures are limited in size and the amount of repairs that could be made on a given area.

The only water-related problem with composites (I did some testing of helicopter rotor blades when working in aerospace) is that some will absorb water, which can cause corrosion problems with fasteners, and there may be some local swelling, and even delamination. This was, of course, after spending months in an unnaturally hot and humid environment, something like 130 Fahrenheit and 100% humidity.

 

[swampyankee]

Back to the P-38:

It seems that the US aviation industry of 1940 had little recent experience in building large, high performance aircraft from wood; this would need to be relearned, which takes time. Part of that learning process would be to evaluate adhesives and construction methods for durability and reliability in service conditions, and those testing methods would need to be developed and validated. There may also need to be evaluation of fastening methods, finishes, repair procedures, and damage tolerance (although how much of this was done with aluminum and steel tube structures is uncertain). I suspect, after seeing Flyboyj's drawing in What if the P-38 was made of plywood a la Mosquito? | Page 2 | WW2Aircraft.net Forums that it would be impractical to build a wooden aircraft meeting the same specs as did the P-38 that has any external resemblance to that iconic, twin-boom aircraft.