So you'd have to weld the airplane together, then heat treat the
entire thing.

Thanks, was pretty sure the must have been a reason, but not having looked
into it I didn't know.

That said, "friction stir welding" is the newest thing in airframe
construction. It works below the melting temperature of the metal,
and leaves good properties behind.

I take it that this would be beyond the average home builder as yet though.

In terms of construction time and difficulty, how would composite compare to
aluminium riveted construction? Thanks,

David