Bob Crantz wrote:-
"
Lookie he

http://www.dwyermast.com/families.as...cat1Name=Masts

Note the various amounts of space within the rope luff grooves.

None of those sections has sufficient room for the luff rope to flake down
on itself, which was your original suggestion. Moreover all of them have a
solid wall backing up the groove. This is essential for strength reasons and
to stop the groove gaping open when the mast bends

The strength of the mast is determined by its moment of inertia. If the
luff
rope groove space can weaken a mast, just think of what the hollow main
section of the mast should do. But it doesn't.

No, of course it does not. The hollow space is on the neutral axis of the
section and the strength of the section derives from the fact that the load
carrying material is as far as possible from the neutral axis. That is why
hollow masts are much stronger weight for weight than solid ones.



The volume behind the slot has no effect on the slot width as a function
of
bending.

That is not true. Move the solid wall at the back of the slot further
towards the neutral axis and then see what happens...

The slot must hold the rope luff no matter what. You could design a
mast extrusion that performs as you say, but who would use it?

I know. That is why you cannot have both a luff rope groove _and_
sufficient space behind it to gather up the luff rope.

Edgar