Spin out: the situation in which the flow of the water along the fin breaks off causing the board to slide sideways or at an angle to the sailing direction.
So there you are, planing along, flying over the water and enjoying the sensation of speed when suddenly the aft end of the board slides away from under you. The result of a spin out will vary depending on the circumstances. While just cruising it will just be a nuisance which is corrected with a little bit of technique. When wave riding it is mostly what we aim for in a cutback to get big spray, hence the reason for small fins and/or multiple fins. On the bottom turn it might cause a more precarious situation ending in a faceplant followed by a nice and thorough wash of the wave. And in slalom sailing, a spin out might result in a coma in the worst case scenario although most likely it will just cause a big splash and a scare if it isn’t avoided or corrected in time.
Why does spin out occur?
The reason for a spin out occurring is that the sideways force transmitted from the sail, through our body and onto the fin is so great that the flow of water breaks off and the back of the board is pushed to the side.
How can I avoid spin out?
There are several things that we can modify. First, in terms of equipment, it’s all about the fin. The length and angle of the fin as well as its relation to the sail size determine both the amount we can go upwind and the likelihood of a spinout.
Another deciding factor is the amount of pressure we put on the back foot and therefore on the fin.
How do I recover from a spin out?
Once the board has given way, leewards, we can correct it by putting pressure on the mastfoot with our bodyweight while pulling the back foot back to put the fin back in line of our movement, ie. in line with the flow of water.
If the fin spins out upwind (like during a gybe or a bottom turn) there isn’t really much you can do besides hope you don’t wreck your kit.
Hope this helps avoid or correct those spin outs you’re having. If you want some more information on spin outs check out this post by Tom von Alten.