Wayne, again you simply just don't understand how stuff is built.
Macca you come straight back with the above statment, you know full well that I know more than most about this sort of thing and yet you still put it in writing. This is typical, time you put a bit of thought into things before putting it out on the net.
A curved spar is no more costly nor time consuming to make in mould than a straight spar. May I also remind you that a curved structure is always stronger in one direction than a straight structure which is inherantly weak in both directions, I think the Romans proved that a good few years ago.
