Improved wood for aircraft ?

Was improved wood better than metal for late inter-war and WWII fighters?

  • No

    Votes: 6 24.0%

  • Yes, wood usability peaking around 1932

    Votes: 3 12.0%

  • Yes, wood usability peaking around 1956

    Votes: 2 8.0%

  • Yes, wood usability peaking around 1940

    Votes: 8 32.0%

  • Yes, wood usability peaking around 1944

    Votes: 6 24.0%
  • Total voters
    25

trurle

Banned
I seen the discussion related to improved wood (actually wood-phenolic plastic composites with phenolic contents above plywood) in
https://www.alternatehistory.com/forum/threads/wi-panic-fighter-1938.444821/

Improved wood (densified wood, engineered wood) was advocated for fighter production before and during WWII. Some states (Soviets, British) even mass produced wooden fighters.
The merits were mixed though.
1) Problems of wood at speeds above 650 km/h due insufficient rigidity (and therefore inacceptable increase of wood volume)
2) Problems with stock availability for aluminum vs wood and associated costs
3) Manufacturability consideration (improved wood molding was arguably easier than for metal, but joining wooden parts was a problem due moisture sensitivity etc.)
4) Debatable weight savings or overweight of improved wood products vs aluminium
5) Other factors favoring wood or aluminium?

Was the improved wood technology really practical?
If yes, when the peak of usability happened?
(answer may differ for different countries)
 
marathag

marathag

Wood makes for a composite material, just like fiberglass or later kevlar and carbon fibers. The resin and glue developments are more important than the wood itself
 

Dynasoar

trurle,

In previous threads, the concept of a wooden fighter entered the discussion in the context of a small prewar European nation fielding a home protection fighter without an established, modern (for mid 'thirties) aircraft industry. While not stated, the realities would have been no indigenous supply of aluminum sheet or extrusions, and general lack of precision metal fabrication groups. Alternatively, many close tolerance wood fabricators- furniture and lumber& plywood would be expected to be available.

The example of the early thirties record setting Lockheeds- all wood and fabricated on primitive concrete tooling, as well as other partial wood/partial steel tube aircraft, Duramold impregnated wood and others utilizing wood veneer inner and outer shells separated by end grain balsa (early day honeycomb equivalent) forming a light strong monocoque structure were presented.

I believe that where plentiful aluminum and appropriate fabrication facilities were available for mass production there would be no reason for wood construction, however there is no inherent performance disadvantage for the latter.

Dynasoar
 
ennobee

ennobee

Orcbuster said:
No, wood is a lot harder to maintain. Especially the finish which had a drastic impact on performance.
Click to expand...
Still, it beats the previous technology of doped fabric over a wooden frame, or even doped fabric over a metal frame. I recall there being serious attempts in Germany in the 1960's to build and sell all-wood sailplanes. The reasoning was that the current construction methods of fabric-covered wood-and-metal frame had reached its limits and so several manufactureres and experimental aircraft groups were trying new avenues. There were at the same time all-plywood sailplanes, all-metal sailplanes and all-glassfiber / carbon fiber resin sailplanes. In the end the glassfiber and carbon fiber construction won out, but at least for about five years, the odds were even and full-plywood had its day in the sun. And as for maintenance, in the long run it was not that much harder then for the old wood frame kites.

In retrospect it was somewhat logical because formed plywood was already in use from before WWII for specially shaped parts like nosecones or cockpit backs. On occasion even a complete fuselage was build out of two plywood halves joined together. Nowadays of course, such parts are cast in plastic resin, even for airplanes that otherwise have a classic fabric-covered frame structure.
 
marathag

marathag

Dynasoar said:
The example of the early thirties record setting Lockheeds- all wood and fabricated on primitive concrete tooling
Click to expand...
from a quick google
a wooden form of the exact shape of one half of the fuselage body, divided on a vertical plane passing through the center line, is built. This form, or pattern, is next suspended in a large box in which reinforcing bars previously have been woven, and concrete is poured in. A reinforced-concrete block weighing from 10 to 30 tons and having a central depression exactly the shape of half of the finished fuselage is thus made.
To assemble a half shell, the outer layer is placed in position in the concrete mold and coated with a casein glue, and the second layer is placed inside the first layer. A coat of glue is given the second layer, the inner layer is put into place inside the other two and air pressure is applied to a rubber bag which fills the space between the plywood shell and the cover of the concrete mold.
After remaining under pressure in the mold for about 8 hr., the half-shell is removed and placed on a drying rack. It is without joints, cracks or laps, perfectly glued throughout and formed to the exact streamline desired. Two half-shells constituting the fuselage are clamped into position on a “skeleton” by special clamps, and automatically align themselves on the framework. They are glued and nailed in place, and cutouts are made for windows and other openings. Installation of seats and fittings completes the structure
 

riggerrob

Those concrete molds were invented by deHavilland of Canada ...... because they solved problems with wooden molds that tended to shrink or expand depending upon humidity inside the factory.
E glass/window glass was readily available before both world wars.
Another option with molded plywood is adding glass fibre ribbons in high stress areas like a wing mounts or engine mounts. That would/wood be an early start to glass fibre composites.
 

riggerrob

German sailplane manufacturers abandoned fabric over wood construction - during the 1960s - because fabric does not maintain the precise curvatures needed for laminar airflow.
Even today, competitive sailplane pilots spend their off-seasons applying thin layers of epoxy and micro balloons (glass) then devote thousands of hours to sanding off anything that impedes laminar airflow. No power plane owners have that much patience.

The last major user of fabric covered airframes was control surfaces on piston-powered airliners. Fabric cover weights less and is easier to balance against flutter.
 
Last edited:

Dynasoar

Still earlier (early '20s) the Loughead brothers employed laminated wood layup in concrete forms for fuselage of an advanced sport biplane. If any interest, I'll dig up more early Lockheed info. Knew nothing of Canadian efforts along these lines. Was anything flyable made?

Dynasoar
 

trurle

Banned
riggerrob said:
E glass/window glass was readily available before both world wars.
Another option with molded plywood is adding glass fibre ribbons in high stress areas like a wing mounts or engine mounts. That would/wood be an early start to glass fibre composites.
Click to expand...
Was it really tried? My understanding was what without epoxies interfacing glass fibre to other materials was not efficient.
G-3 composite (glass-phenolic): flexural strength 279 MPa
G-10 composite (glass-epoxy): flexural strength 415 MPa
Epoxy production did not start until 1943 though..
 
Michel Van

Michel Van

The Germans perfected Improved wood during WW2
Do to lack of metal they used plywood with sheets of glue, formed under high pressure in molds

the results:

The Heinkel He 162 jet fighter (wings and most part of fuselage except the Engine part) top speed 790 km/h
He162_color010.jpg


The Junkers Ju 322 Mammut (biggest glider ever build)
Junkers-Ju-322-Mammut.jpg


On American side we got the Hughes H-4 Hercules made from wood
746px-H-4_Hercules_2.jpg
 

hammo1j

Donor
Obviously discussion leads to the Mosquito probably the best multi role aircraft of WW2.

When hit I believe they were less robust than aluminium planes though.

Was it the wood that gave it its advantages or was it just a very good design that could have been rendered in metal just as well, had there been wartime availability?
 
marathag

marathag

hammo1j said:
Obviously discussion leads to the Mosquito probably the best multi role aircraft of WW2.

When hit I believe they were less robust than aluminium planes though.

Was it the wood that gave it its advantages or was it just a very good design that could have been rendered in metal just as well, had there been wartime availability?
Click to expand...

Aluminum can be lighter than fiberglass for construction, and laminated wood is a weaker composite than fiberglass. Another downside is Aluminum is isotropic, giving uniform strength in all directions, wood is anisotropic, so multiple laminations are needed to get strength in the required directions.

They have different fatigue as well.

Once you get to actual spun glass with resins, the strength to weight ratio is better than Aluminum alloys, but we aren't there yet with the layup used with the Mosquito, Duramold was close in strength, and had the advantage of no stress points from riveting, so in effect better than Aluminum

So, an Aluminum Mosquito would have been slightly higher performing
 

hammo1j

Donor
So, an Aluminum Mosquito would have been slightly higher performing.

Wow! Thanks for the reply. Always wondered about this. Was the successor to the Mossie aluminium?

Why no attempt to mass produce the Mosquito concept?
 
marathag

marathag

hammo1j said:
Why no attempt to mass produce the Mosquito concept?
Click to expand...

There was by Howard Hughes for longe range recon, as the Mosquito started as.
Twice the size and horsepower for four times the Range.
Specifications (XF-11)


Data from Jane's all the World's Aircraft 1947[13]

General characteristics

  • Crew: 2, pilot and navigator/photographer
  • Length: 65 ft 3 in (19.9 m)
  • Wingspan: 101 ft 5 in (30.9 m)
  • Wing area: 983 sq ft (91.3 m2)
  • Empty weight: 37,100 lb (16,828 kg)
  • Gross weight: 47,500 lb (21,546 kg)
  • Max takeoff weight: 58,315 lb (26,451 kg)
  • Powerplant: 2 × Pratt & Whitney R-4360-31 Wasp Major 28-cyl. air-cooled radial piston engines, 3,000 hp (2,200 kW) each
  • Propellers: 8-bladed Hamilton Standard Hydromatic contra-rotating propellers
Performance

  • Maximum speed: 450 mph (720 km/h, 390 kn) at 33,000 ft (10,000 m); 295 mph (256 kn; 475 km/h) at sea level
  • Service ceiling: 42,000 ft (13,000 m)
  • Rate of climb: 1,000 ft/min (5.1 m/s)
  • Time to altitude: 33,000 ft (10,000 m) in 17.4 minutes
  • Wing loading: 59.3 lb/sq ft (290 kg/m2)
  • Range 4,971 miles (8,000 km; 4,320 nm)
This was a redo of Hughes D-2 he was trying to sell to the USAAF that was made from Duramold

compare to

Specifications (B Mk.XVI)

Data from Jane's Fighting Aircraft of World War II,[200] World War II Warbirds[201]

General characteristics

  • Crew: 2: pilot, bombardier/navigator
  • Length: 44 ft 6 in (13.56 m)
  • Wingspan: 54 ft 2 in (16.51 m)
  • Height: 17 ft 5 in (5.31 m)
  • Wing area: 454 sq ft (42.2 m2)
  • Airfoil: RAF 34 (modified)[202]
  • Empty weight: 14,300 lb (6,486 kg)
  • Gross weight: 18,100 lb (8,210 kg)
  • Max takeoff weight: 25,000 lb (11,340 kg)
  • Powerplant: 1 × Rolls-Royce Merlin 76 V-12 liquid-cooled piston engine, 1,710 hp (1,280 kW)
  • Powerplant: 1 × Rolls-Royce Merlin 77 V-12 liquid-cooled piston engine, 1,710 hp (1,280 kW) RHS fitted with a blower for cabin pressurisation
  • Propellers: 3-bladed constant-speed propellers
Performance

  • Maximum speed: 415 mph (668 km/h, 361 kn) at 28,000 ft (8,500 m)
  • Range: 1,300 mi (2,100 km, 1,100 nmi)
  • Service ceiling: 37,000 ft (11,000 m)
  • Rate of climb: 2,850 ft/min (14.5 m/s)
  • Wing loading: 39.9 lb/sq ft (195 kg/m2)
  • Power/mass: 0.189 hp/lb (0.311 kW/kg)
 
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