Advice on wooden aircraft

[cherry blossom]

Arboria was a neutral during WW2 and its airforce was able to buy or copy designs from almost everyone. In particular it was able to obtain the latest aero-engines from both sides. However, it suffered the great disadvantage that it had limited access to light alloys and therefore tried to equip its airforce with mostly wooden designs. What advice can our experts give?

I would like advice based on two possible scenarios. Firstly, by suggesting designs at the time that historically they entered or might have production. For example, the Arsenal VG-33 first flew in 1939 and entered production in 1940 with, according to Wikipedia, only 19 aircraft out of 40 completed being received by the Armée de l'Air by the time of Armistice. However, its engine was the same as that of the MS 406 which had slowly entered production in 1938. Thus we could imagine that the VG-33 might have entered service earlier unless some of you want to point out that France couldn't design a good radiator in 1938.

This divergence between dates occurred with other interesting wooden fighters. The Swedish FFVS J 22 first flew in 1942 and only entered service in 1943 but used a R-1830 that had entered production long before. The Finish VL Pyörremyrsky similarly only flew after WW2 in November 1945 but its DB-605 was in production from early in 1942 and a prototype could have flown with a DB-601 any time after 1938.

The most obvious source of wooden fighters may be the Soviet airforce with examples such as the LaGG-3 with its wooden construction celebrated by the name "guaranteed varnished coffin". Pilots might prefer a Yak-1 or 7 or perhaps something more exotic such as Polikarpov's I-185. The last raises the issue that it had a wooden fuselage but light alloy wings (whilst other aircraft such as the He-162 had wooden wings and metal fuselages). The Soviet designs slowly transitioned from mostly wood to mostly light alloy over 1941-5. It also raises the issue that the I-185 had a M-71 18-cylinder radial which may never have become very reliable. Could Arboria have simply bought a licence to fit a P&W R-2800, which would seem possible based on dimensions and weight?

Before leaving single engined fighters, we can note that few wooden designs had long ranges. The Tachikawa Ki-106 Tachikawa Ki-106 - fighter might have had a better range than most of the above but was probably rather over weight as well as late.

When we turn to two engined fighters, nothing approaches the performance of the de Havilland Hornet but we will have to wait a long time to get it into service.

If we are willing to use some aluminium, we might consider the mostly wooden Fokker G.1. This represents the other end of the spectrum to the Hornet in terms of performance but did fly in 1937. Perhaps, we could imagine rather better performance if it were fitted with more powerful engines. The G.1 was also tested as a dive bomber and will probably be most useful in that role.

The level bomber squadrons of Arboria will probably be equipped with CANT Z.1007 Alciones in the early war period (oddly Italian bombers were often built with wood and Italian fighters with aluminium whilst the USSR reversed those trends).

Naturally from late 1941, most bomber squadrons will use the Mosquito as will night fighter units.

Transport squadrons will probably use the Savoia-Marchetti SM.75 from the 1930s and introduce the Savoia-Marchetti SM.82 from 1940.

 

[z42]

• A more powerful engine can cover some deficiencies in the airframe design in terms of heavier weight for a wood construction compared to stressed skin aluminum. With Arboria able to acquire the latest aero engines from anyone (credibility stretching a bit thin here, but anyways), Arboria can pick the R-2800 as their standard engine and use it everywhere.
• While not wood, as the goal is to as much as possible avoid light metal construction, steel tube + fabric construction should not be discounted either, particularly for things like transports.
• A lot of R&D should be spent on glues, that's really key for wood laminate construction.
• Or for an out of the box alternative, extract magnesium from sea water (as used on an industrial scale during WWII by Dow in the USA). Unlimited light metal supply!

 

[Shortround6]

A lot of R&D should be spent on glues, that's really key for wood laminate construction.

To 2nd this, there were a number of methods of wooden construction and most depended on the different "glues" or resins.
Depending on the supply situation the glues or resins could be a bigger stumbling block than the different metals.
The Mosquito was at a different end of the spectrum, the "glues" may have been more common, no phenol-formaldehyde resins or large autoclaves (fancy ovens) needed.
Problem is that Balsa was not really commercial grown at at the time. It also didn't grow in groves or groups, some times one tree per acre of jungle? If you want to mass produce large airplanes you need to really beef up the Balsa logging industry.
Really good aircraft grade wood was not as common as some people believe. Which is one reason for the some of exotic blends of resins, Some of these "wooden" aircraft were sort of cousins to Bakalite which was formed from coal tar and wood alcohol products.

What worked for trainers (or glorified WW I aircraft) didn't work so well on 350-400mph aircraft that needed to sustain 7 Gs or more (10-11Gs safety load).
And sometimes using big engines makes things a lot more complicated. You to design and fuselage, wing structure that will hold a 2300lb engine doing 6+ G turn (14,000lbs (23,000lb safety)) repeatedly without failing?
Now design it so you can get inside to look for cracks in service.

 

[Howard Gibson]

If Arboria cannot get at metals, they cannot get at other exotic materials, like balsa wood. The British had problems with adhesives in tropical climates like in India. Assume Arboria is not tropical.

The problem technology is aluminium monocoque structure. Don't rule out tubular steel structure, particularly the fuselages.

The French and the Russians made extensive use of steel tube and wooden structures. We are probably agreeing that the German use of aluminium monocoque was better, but the French and Russians had weaker engines, and problems with tactics and training. The French were knocked out of the war before they would bring out the 1600HP Hispano-Suiza 12Z engines.

The de Havilland Mosquito was built from the ground up to be made of wood. The Nakajima Ki84 was all metal. When they converted this too the all-wood Ki106, it gained 300lb, but the airframe was designed around aluminium.

The Russian Lavochkin La-5 was all wood. The Yakovlev Yak-3 had wooden wings and a steel tube fuselage, much of which was covered in fabric. Both aircraft had good performance. Both aircraft eventually were converted to metal structure. Metal was better, but perhaps not a lot better.