La-7 vs ??? (attn Franek)

[Jukka Juutinen]

Originally Posted by Franek Grabowski

I am not sure if I should post a separate reply but I think it would be clearer.
Great there is a separate board but woul it be possible to have some storage area for photos and drawings?

Finally something technical. The main difference between Soviet and Western aircraft was that they largely consisted of wood. Wood allows to make very aerodynamic shapes but it takes volume and weight to achieve same endurance. That was the main reason the world moved to metal designs and still continues the way.

Not so simple. First, we have to determine whther we use wood as such or as laminated structures. In general it is true that wooden structure of same strength takes up more space but necessarily weight. With wings this could be problem (e.g. dH Hornet) but usually less so with fuselages. Wood does have one excellent characteristics: very good fatigue strength (Finnish aircraft desgner Arvo Ylinen wrote several articles on this for Finnish trade journal "Aero").

Another Soviet difference was that they often had steel wing spars (spar booms) if the spars were of metal. This mayn sound awkward, but it is not so. If we assume alloy steel treated to provide an ultimate strength of 1400 N/sq.mm, we get approx the same weight for the same strength if we use high quality Al-alloy (600 N/sq.mm max) with steel having better fatigue characteristics.

So, if I were to design an aircraft employing maximum amount of wood, I´d probably do an all wood monocogue fuselage with a segment of the fuselage built integrally with an all wood wing centre section and outer wings with two steel truss spars with plywood covering.