Hi
I need some advise.
The gear: 105l tabou rocket, 7m code red, mfc rc-2 36 fin. outboard straps and seat harness.
When i reach 25.5knots I sometimes spin out. It is always at this exact speed +- 0.5 knots
If i don't spin-out the leeward rail starts to bite into the water at +28knots.
Do you have any suggestions to what could be wrong?
Thanks
Yeah, our crown prince really shot the parrot on that one! (good translated danish expression)
I don't think i am doing anything to cause the problems. I don't look at my gps while sailing, but topspeed after a spinout always say's 25-26. and i feel the rail bite a bit before i reach top speed on 30knot runs
I just lock in, and hang on. So i'm thinking it's the fin, but the size should be right. Could it be a weird situation where 25knot doesn't produce enough grip and 28knots produces too much lift?
Should i rake the fin back a couple of degrees? i'm guessing that the grip will not change but the lift will decrease.
Spin out could be caused by to much back hand pressure, try shifting your harness lines a touch further back.
Rail grab possibly shift your boom up a bit or shift your mast foot back a bit to free up the front of the board.
also try pointing the front foot and taking a bit of weight of the back foot which should help the board trim flatter.
If you have a friend with a go pro see if you can borrow it to get some video of you and the board to see what is going on
Something that's stuck with me from a Peter Hart video:
He asks the two other experts if they think they can spin out on demand. They say "Sure, no problem". So off they go.
Peter says to the camera "I bet they can't"...
And so it goes. They come screaming back towards the camera, and at the appointed place push really hard against the fin, and all that happens is they rocket off upwind instead of spinning out.
Perhaps what's happening is that at that speed your fin and board are starting to fly and 'rail up'. This is normal, and part of the fun. Lean out more, keep the board trimmed flat, and accelerate to warp 9!!
Just a thought based partly on Nebb's reply
as we know the fin may generate a lot of lift at higher speeds and cause the railing up, so to compensate it requires heel pressure/toes up.
However at other times this may cause spinout due to loading it up too much - so are you perhaps going too much heel pressure / fin loading too early, causing spinout...... and then when you get up to speed you have the spinout experience in your mind so are not giving it enough which causes the railing up?
My starboard kode 112l used to do this, nearly everytime at 28knots, 100-110 deg off the wind....basically just as I was starting to follow the gust and bear off.
I tried a different fin from the stock Drake 36cm freeslalom swift and it has never since span out.......
Sometimes it could be a bad fin/board combo coupled with something in your/our technique. That was my conclusion. I even tried sanding all the paint off the fin. smoothing it. polishing it......then traded it in for a real fin.
Mine does it too...normally when I hit 40kts. Then I wake up (smiling) & get out of bed.
Put the fin across your knee and try to bend it. How flexi is it?
I have a 34cm fin that is very flexi and it produces much the same symptoms you describe. I think the flex gives the fin vertical lift, this pushes up behind you forcing the leeward rail down. This can also lift the windward rail allowing air to get to the fin causing spin out.
The other possibility is a foil thick at the front, this gives good low wind performance but can make to much lift at speed, and a very strong low pressure area near the leading edge, this can cause cavitation at speed.
I had four MFC fins - 44 and 40 RC and 36 and 32 SL. The 36SL never worked for me, often spinning out. The others were all good. Sometimes I think you can get a lemon just like with cars.
whoever red thumbed my last post, if you don't believe how much a fin can bend, have a look at darrylg's post on the 2nd page of "flying the fin", in the GPS & speed sailing forum.
Some sailors like this effect, others don't. It may depend on skill level, rider weight, board set up etc, I just know I don't like it.
thank you very much... good insights, now i've got something to be aware of next time i go out! Maybe i need to get a "real" fin
think I've figured out how to copy the picture over.
YES!!!!
There's hope for this old bugger yet.
Look at all that weight on the windward rail, and see all the spray from the leeward rail.
That fin is working!
I think i need to get a breathalizer to access my computer 
