Franklin,You still don't get it.
The haylard is connected to the sail's head. The sail's tack is connected to the bar. Pull the haylard tight and it pulls the bar up as far as it can go via the sail. That's why it doesn't move around when the mast is up. Gravity has nothing to do with it. Take the sail out and you loose all that tension that holds things in place. Like I said before, it doesn't matter if the mast is up or not, if the haylard is tight, the sail is not going to move. If it did, then our sails would shafe all the time during storms at the dock.
I actually do get it.
Please look at the manual for a Selden furling spar which I have linked to in the above post.
I have a very good working knowledge of how these spars operate. The halyard tightens the LUFF only. The bottom of the foil rides in bearings that DO NOT move up or down. The top of the foil also rides in a bearing that does not move up or down either. This is called the top swivel.
The foil tension on Selden's, at least the ones I've worked on, is separate and set by a foil tension screw in the mast base. I have adjusted one before.
I will try to find a schematic and instruction manual for you so you can clearly see that the halyard does NOT tension the foil.
EDIT:
Didn't take long but I found one. This mast is very similar to the one I adjusted two years ago.
Selden Furling Mast Manual (LINK)