Hey Peter you might be sheeting in too hard when you bear off or the sail might be too flat (which might overpower the fin). I usually unhook from the harness lines when the board spins out and that seems to sort it out. Would have thought a BP would be hard to spin out, was that the spot where i was bearing off on Saturday over the far side towards adjacent where we launched from?

The board starts to slide with the nose heading upwind and your arse sliding underneath you when it spins out so with all you might, force the board back downwind and at the same time lift the windward rail with your feet / ankles so the leeward rail and fin rolls over - this releases that big pocket of air that the fin has sticking to it. In my experience a carbon fin takes considerably a lot more effort to release from a spin out than a more flexible G10 although a carbon doesn't tend to let go as much (if at all).

The spinning out when bearing off may be just the fin's inability to compensate for the quick change in pressure (as the AoA changes). Try bearing off not so aggressively and play around with the mast track position. Sometimes though it's just that one fin that does it and if so get rid of it if it doesn't suit your sailing style (or lack there of )

sausage said..
play around with the mast track position. )

as a general rule how mast position effect spin out ?
Which one - moving forward or backward could help a bit to prevent spin out in first place ?

Having the mast track further back will mean that the centre of effort of the rig will be further back and puts more 'weight' on the back of the board and puts more pressure on the fin.

This also makes the board tend to round up into the wind, so it could be an imbalance as you bear away that causes the spinout... So I'd try putting the track forward.

Windxtasy said..
The usual technique applies, drag the back of the board toward you and bear away down wind a bit, or if already pointing downwind a lot, straighten up. Unhooking helps. Take pressure off the fin. Just keep changing things until the fin bites again.
Even so I have had some spinouts where I have gone sideways at speed for many hundreds of metres. Once I turned the board over afterwards to make sure the fin hadn't completely gone, because there was no sideways resistance at all. For a while one of my 2 sec PB's was going sideways!

I had that yesterday when overpowered and in small chop.. bit disconcerting!Still yeehaa able..

Potentially, as the board will sit flatter in the water with the nose down, so more water line and more drag and will feel 'bogged down' Thats why there is all the fuss about finding a 'sweet spot'. But too far back can also make the board 'fly' uncontrolably, and 'tail walk'. Lots to consider! Best to try a few things and see what works, everyone is a bit different depending on style and skills.

Pete check the fin sits flush as possible with bottom of board I had a dodgy fin that seated a couple of mm high at front of fin box and spun out 2 or 3 times in a run.
sanded fin down and the bp 40 in question I sanded didnt com close on same day.
When I spin out ,I snap (pull)back of board under my arse as fast as possible , removing all pressure momentarily from fin , if it doesn't work first time I have usually slowed enough for it to work the second.
as for bearing off the action of pulling your board under bum automatically turns board off the wind.

Peter,

For me the most usual causes of spin out are:
- landing a jump with too much back foot pressure
- trying to point to high at low planning speed
- fin too small for size of sail

The best ways to recover are
- take back foot out of strap, place on other side of the board and bear off
- head up into the wind to slow down until fin re-engages
- chop jump and land with no back foot pressure

You may have hit on something there macro, if the water is aerated, it's much easier for the fin to ventilate. Another possibility is a bad seal at the top of the fin bolts. Air can get sucked down onto the fin that way as well. I know what you're talking about I've experienced that as well, I put it down to faulty technique on my part, unsettling the board by being a bit too aggressive.
I find the best way to recover from a spin out, is the soccer player's back heel pass to the player behind. Definitely have to leave your back foot in the strap, curl up your toes so you get a good grip, then pretend you're that soccer player, and kick that ball with your back foot. Sheeting out and leaning sail forward a bit at the same time also helps.

But a word of warning, at speed down wind, if it's choppy and it's a major spin out, there's a big risk of tripping the leeward rail on the chop, this can lead to a damaging catapult. If the spin out is too severe, and beyond recovery, I take the safer route, keeping feet in straps, sink the windward rail, and use my bum as a water brake, depowering the sail by pulling it down so it's just over my head.

JockyC said..
Having the mast track further back will mean that the centre of effort of the rig will be further back and puts more 'weight' on the back of the board and puts more pressure on the fin.

This also makes the board tend to round up into the wind, so it could be an imbalance as you bear away that causes the spinout... So I'd try putting the track forward.

Where you put the mast base in the track will never move the centre of effort forwards or back. All it will do is stand the rig up a bit straighter or rake it back slightly. The centre of effort is always balanced with the centre of resistance. Period. That is unless raking the sail changes the airflow over it enough to change the actual centre of effort in the sail itself which is very unlikely but not impossible.

Position of the mast base will affect all sorts of other things to do with your leverage over the rig. Mast back will slightly raise the boom height and change the angle. Standing the sail up more will likely slightly raise the centre of effort in the vertical plane.These things may or may not affect spin out.

Changing the rake of your fin will usually change the centre of resistance in the fore aft axis. I find a highly raked fin means I have to move the mast base further back to compensate and this also puts more weight on my back foot if I can't move the foot straps to compensate. This can also make the board ride higher in the nose depending on the design of the fin and it's total lift.

Preventing spinouts is more about having a good fin that suits the size and power of the rig, and an efficient rig without big draft movement back in gusts. Also trying not to over pressure the fin, especially with big shock loadings if possible.

Recovering from spinouts is usually done by sheeting out to reduce pressure on the fin and taking pressure off the back foot. Actively trying to pull it in helps a lot as well if that is possible. A really good fin to me is one that will recover flow itself quickly if the pressure is taken off it a bit.

decrepit said..
I find the best way to recover from a spin out, is the soccer player's back heel pass to the player behind. Definitely have to leave your back foot in the strap, curl up your toes so you get a good grip, then pretend you're that soccer player, and kick that ball with your back foot. Sheeting out and leaning sail forward a bit at the same time also helps.

I tried this yesterday and it works. Thanks for the tip