The smooth thru-mast bolt I'm talking has nothing to do with the trapeze. It's to prevent the spinnaker halyard from getting jammed in the mainsail track. This tends to happen when you are in the "oh shit" conditions Henry fondly refers to and the mast bends to a point where you think it will snap, but pray that it doesn't.
As an exercise, draw a bent mast and then draw a straight line between the spinnaker exit sheave and the exit slot at the base. You'll realize that the halyard would be outside of the mast. In reality, the halyard will not wear through the mast, but the odds are very good that it will eventually get jammed between the mainsail track and the rivets holding the spreader bracket (or attachments) to the back of the mast. And believe me, when it gets jammed between the rivets and the track, there is nothing you can do on the water, short of hoping for a miracle, that will loosen it. As Tof and myself found out in Ireland, this is not a good thing to have happen when trying to take down a chute in 20+ knots of wind.
The solution to the problem is to drill a hole through the mast about two feet below the spreaders and install a smooth bolt. When installing the bolt, make sure that the main halyard is behind the bolt since it doesn't matter if it jams during a race, and that the spinnaker halyard is in front of it. The bolt will provide a turning point for the halyard and keep it away from those nasty rivets. Its a very clean solution and, if properly done, will eliminate any chance of the haliards fouling themselves during transport, and will ensure that the chute drops cleanly in all conditions.
All of this talk about fouling lines in a mast is another argument for using deck-level rig tension, as there is one less piece of wire in the mast.
Then Henry says:
Different solution - NEVER EVER BEND YOUR F***ING MAST THAT MUCH YOU SILLY MAN
In 20+ we solve the problem this way.
Our max bend point for the North main was 6" before vang (4" prebend with the strut just shy of snug.) Before getting to the windward mark we make sure the strut down is CLEATED and then haul on the strut up HARD to lock the mast in place. We then release the vang, controlling the leech with the mainsheet only at the mark rounding. We set the kite and pole, and then use vang sparingly.
On tight reaches we haul on max cunningham, and pull on a little vang. The mast does not bend any more or less with our vang play- we are only opening and closing the leech. It is the bending of the mast AFTER the spinnaker halyard is cleated and topped out that forces the halyard into the track- the distance between the cleat and shive increases with bend. If it is topped and cleated the effect Tom describes definitely occurs. Adding a twing ball in between a stopper knot and the head of the sail will help- the knot should pop through and provide relief (the head of your sail should be 1-2" down from maxed anyway). You know you went too far when you take the kite down and the twing all is on the wrong side of the stopper knot.