>>>If it were not so then the Romans built all those columns at the Parthenon incorrectly.

Isn't the parthenon build by Greeks ?

Besides I don now of the Parthenon that the construction is crooked on purpose. This is actually the brlliance of the piece. If they used straight lines than the building would not appear straight visually. There is actually no staright line in the contructtion. By incorporations curves and crookedness the architect compensated for the imperfections of the human eye and brain when the object it looks at isn't relatively small and in one plane.

Netherless you are very much right that a prebend pole theoretically has a lowered buckling load. However the by forcing the buckling direction to be upward (by weakening it a little in this direction) one can use lines or wires to stabilize the setup. Of course lines and wires can only provide a pulling force and not a pushing force. Hence the buckling mode of downwar needs to be prevented as that can't be stabilized with support wires to the side.

Of course when a line between the pole and bridle strop is used (Three support wires to the middle of the pole) than the whole system is closed and not prebent is necessary. Even though it is handy to lower the tip of the spi pole.

Anyways the Prebend lowers the buckling load but adding the support lines increases the buckling loads again. So much so that the new setup how as much higher buckling load. You loose a little but that is corrected out over by winning alot. End result is a big net gain.

>>Some spin poles are set up with what appears to be prebend but under load they are straight.

Yes this could be the case. I haven't looked at it like this. On the boats I sailed this wasn't noticeable.

Wouter