And Why Do You Need One?
A spinnaker strut is a relatively short (usually aluminum) pole with one end fitting designed for mast attachment, and the other for running a line across a small internal pulley. Standard sizes range up to about seven feet in length and three or four inches in diameter. They look like this:
As its name implies, the strut is for use with a traditional symmetrical spinnaker. It will keep the afterguy (or the spin sheet you’re using as an afterguy) attached to the spinnaker pole away from lifelines, stanchions and other undesirable points on its way back to the stern.
The strut is usually attached to the mast via a padeye on the mast, and often held in position with a sail tie to a shroud
Sailors want a reaching strut because:
And, more important – when sailing fairly close to the wind with the spinnaker, the pole is well forward. In a good breeze the afterguy or sheet is very heavily loaded. If that lifeline or stanchion (or both) bends enough, or breaks, the pole will slam forward into the forestay. Bad things can happen. Very bad things.
A reaching strut is easy to rig, and easy to use. Because it’s fairly short, it’s also easy to stow. And not expensive , especially when you consider the cost of a forestay or mast.