RE: How to avoid "spin outs"?
Thanks to both of you Roger and o2bnme,
I have actually 3 boards, all JP's :@ from 85 to 130 l Crossover type (Freestyle Wave) the smallest and Freeide the other two. I have for each board 2 fins, i.e. from Curtis and Selectm which I selected for the specific board and sail sizes. So, the size and quality of the fins should not be a problem. If still helpful I can provide the details later. Sails types vary. 9.0 and 7.0 Freeride, 5.8 Crossover and 4.7 and 4.0 Wave. Water conditions vary but it happens on flat water / choppy conditions (lake) as well as wavy conditions on the ocean (North Sea or similar).
The spinouts typically occur when I am at higher speeds and have some load in the sail and I guess more frequently when I go slightly upwinds.
I don't know the answers to the other questions (below) - I don't do any of consciously, so will pay attention to this when I get onto the waer next time.
When you put "pressure" on your fin, what is the rail to rail attitude (the roll angle) of your board? Are you sailing with the upwind rail lower than the downwind rail?
Are you trying to sail "on the fin" with the lee rail slightly (very slightly) lower than the upwind rail?
Are you trying to push the tail of the board down, toward the water, or trying to push the tail away from your body?
Thanks again and I will get back when I can answer the outstanding questions, which may take a bit of time.