Ulrike Wegst wrote:
> 
> PS: The Spruce goose showed that also large aircraft can, in principle, fly.
> It also showed, that its design was inefficient --- as a natural
> organism it would have been dead very quickly.

Was it the design that made it inefficient, or the power/weight ratio
(it had the largest engines available to it at the time)?  Keep in mind
that Howard Hughes was one of the best aeronautical engineers of his
day.
> 
> Similarly, a wooden Jumbo could be built, but would it be able to
> compete with aluminium and composites in this application (cargo volume
> and weight, range, ease of manufacture, cost, etc.)?  Wouldn´t we have
> more commercial wooden aircraft, if it could?

Not necessarily.  I expect current practice would make it too labor
intensive and therefore not economically feasible at the moment.  But
that doesn't mean that it would be impractical under all conditions, or
for all times.  Had the Goose come along about 3 years earlier, it would
have been quite feasible and most useful, particularly if the big
Lycomings had gone into production.
> 
> Spruce Goose vs Jumbo:
> 
> Wingspan:
> 747 = 320 feet
> Spruce goose = 212 feet

Don't you have that backwards?
The Goose has a wingspan of about 319 feet 11 inches.  The Goose wing is
11 feet thick from top to bottom at the root and has a root chord of
about 50 feet.  From memory, the wing area is somewhat more than eleven
thousand sq.ft. (11,430 with the "," being a thousands designator rather
than a decimal point).  The wing area of a 747-400 is about 5,600 sq.
ft. and the 747 has two different wingspans, dependent upon the model
number. Span ranges from approximately 195.66 feet to 211.4 feet.  If my
arithmetic is correct, that means the Goose has about 107 feet more
wingspan than the big 747 and about 123 feet more than the small 747,
and the Goose has a little over twice the wing area of a 747.

> Length:
> 747 = 232 feet
> Spruce goose = 219 feet

The Goose is actually only 218 feet 8 inches long.  You got me there.

> Range:
> 747 = 7 670 nautical miles (14 205 km)
> Spruce goose = 70 feet

You're confusing range with height.  On its maiden flight, the Goose
flew at a height of 70 feet for slightly more than one mile.  This is
not maximum range for the aircraft -- just the distance that could be
safely flown while remaining within the harbor.

And speaking of height,
747 tail height   = 63.41 feet
Goose tail height = 79 feet

All the best,
James Robards Cunningham

P.S.  Feel free to consider me prejudiced regarding Howard Robards
Hughes' abilities as an engineer.  :-)