Ramona said..
On my SS34 I have a whisker pole made from the tops of two windsurfer masts. easy to carry one handed and light when it comes to setting. I'm fairly confident it would snap if it had to.
Ok so now it seems that we are talking whisker poles alone to pole out the headsail rather than the spinnaker pole.
I'm thinking people must have very long whisker poles because my understanding is that a whisker pole is only intended to be long enough to protrude a bit beyond the shrouds to increase the angle (mechanical advantage) when it is necessary to pull the spinnaker pole away from a position very close to the forestay. Certainly the whisker poll on my NorthShore is not much longer than that (although there is some adjustment which facilitates easy storage) and nowhere near the J measurement. It is however a hell of a lot less beefy than the spinnaker pole which would assist it to work as a fuse protecting the mast if it were long enough.
If the pole is to be useful for keeping the headsail out I would have thought that it needs to be a lot longer than half beam at the mast. What lengths are we talking about as a percentage of the foot of the relevant headsail or the yachts J measurement?