Here is the site I forgot to send you.
www.fortboise.org/windsurfing/spinout.faq.html

There are soo many "causes" it's hard to know where to start.

Basically it's because the fin can't handle the side ways force of your back foot fin stalls, laminar flow ceases and ventilation occurs, (air is sucked down fin)

causes are
Bad sail setting, (not enough downhaul/outhaul) can mean sail makes more sideways force than forward lift. increasing downhaul (if there wasn't enough) means more forward lift from sail, more speed, thus more sideways lift from fin.

Sheeting on too hard before up to speed, some fins designed more for speed, don't have a great angle of attack, and will stall when loaded at low speeds, you have to ease them up to speed before fully loading them.

Damaged fin, nicks and other fin damage can cause turbulent flow, decreasing lift.

Harness line position, if your lines are too far forward, your back hand pressure to sheet in is transfered to your back foot. Make sure your lines are neutral, and back hand pressure is minimal.

And as I've found out, a raked fin with too thick a front edge handles a great angle of attack, but doesn't like high speed.
Like wise a fin with too fine a leading edge goes fast OK but won't handle as big an angle of attack, so it will stall earlier if you push it especially upwind.

OK that's enough from me, undoubtedly others will think of the ones I've missed.

most of the time when I'm spinning out my fin is a bit loose in the fin box. If there's any play at all to it, I'm going to spin. Fins work themselves loose over time...grab your fin and push it sideways...if there's any looseness at all you'll feel it immediately. Then tighten.

It is usually bad technique or a poor fin as most have advised,however if your newish to this the smallest bit of seagrass/weed can spin you out, experience tells you the subtle diffrence, even the noise but just remember its not always the kit or sailor.

Corkers said...

When i spin out my mate overtakes me....... this is no good!

Make sure you are up-wind of your mate when you spin out, he won't overtake you again!

Paul