I have moved my footstraps further out on my 140 litre board as i was placing most of my weight on the heels of my feet. This has addressed that problem but now I find I am spinning out sideways (going broadside with nose heading into the wind.) occasionally. I have this spinout problem much more on my 101 litre board so I am reluctant to move the footstraps out from the most centre position but I feel I need to as I am also placing too much weight on my heels at times. What is the best way to stop these spinouts? More weight on the front foot, more weight in harness?

Ive recently discovered that fin size is vital to avoiding spinouts, i was on a 6.2 planing along at 22 knots, spanout and went sideways, catapaulted and damaged my board. I was using a 28cm fin (which i learnt was too small)
Later that day (repaired the board) i went out and used a 34 fin, and no problem :D


Ive also found that downforce is a cure when lost traction.
www.guycribb.com/userfiles/documents/downforce.pdf

also some other stuff,

footstrap position is definately a big player. so is fin area and cord ratio. the wider the rear straps are apart the bigger the fin typically you need to carry.

speed also comes into it. the faster you go the mopre lift created and potentially the smaller the fin you can carry. plus water state will make decisions on the type and length of fin to use.

there is a balance that trial and error will achieve.

so a fin that works when you have 1 rear strap most likely won't work as well with 2 rear straps and vice versa.

the difference in the straps means also a different stance. 1 strap = more upright, 2 straps = more outboard.

on my single rear strap boards i can use a 23-24cm fin with a 6.4 and not spinout, any bigger than 32cm and the fin is too big.
stick that 24cm fin in my slalom boards with double rear straps and it is a stinker. spinout galore...

on my wide tailed double rear strap boards i am more likely using a 36-38cm fin with a 6.4m and 42-48cm with an 8.5m

as you progress from beginner to intermediate, and move your straps further out you may find that you also need to change the way you rig your sails and also the fin sizes you use.

that looks about right.

how about downhaul harness line position like sailhack has suggested.

to fix heel pressure you need to look at stance further, where is your boom, it should be shoulder height plus.

edit* you could use a smaller fin in 18knots on your big board with a 6.7 and eventually will need to. you'll know if it's too big as the board will tail walk.

spin out happens when going flat chat in choppy conditions.

Have to agree with sailhack on the harness line position.
If you have to pull very much with your back hand then you counter that by putting too much pressure onto your back foot. Biggest cause of spin out for me neway which is easily solved by moving the lines back until I'm doing more tweaking of the sail with the front hand. Your fin sizes seem appropriate so I think that the issue is elsewhere.

Thanks guys. Moved the harness lines back today in a 20knt breeze on my 101 litre and had almost no problems at all.Previously I had a lot more spin out. Thanks for your help. Hope to try out a 85 litre board this week. it will be interesting to see how I go there.

Mark _australia said...

Are you talking about spinout where you are going flat out in chop and the fin loses traction?

Or are you perhaps getting in the straps when barely planing, loading the fin up and things are starting to go sideways? Sorry, no insult intended but some people do jump in the straps when not planing ........ just clarifying

This is very relevant.
The sail is simply a wing operating on its side. i.e it's vertical to the ground instead of being horizontal to the ground. But the laws governing it's behaviour are still the same as any wing.
It is easy to slide out under even quite light winds if you pull the sail in too early before the forward speed builds up. In effect you are either stalling the sail or at least, operating it closer to it's stalling angle of attack. Then, all you end up with is the sideways force while losing the forward thrust component of the lift generated by the wing (sail).

The most effective angle of attack for a wing is around 15 degrees.
This is the angle which you should try to keep the sail to the apparent wind to get the most forward thrust for the minimum amount of sideways force. i.e the minimum amount of force trying to make the board spin out.
If you increase this angle by hauling the sail in, you don't immediately lose all forward thrust but the ratio of forward thrust to sideways force rapidly diminishes.
The result of this can be that even though you can feel lots of force on your arms trying to hold the sail in, it is operating more as a parachute and you get little forward thrust, acceleration is slow and the board keeps sliding out.
It is actually quite difficult to sense this optimum angle because the feedback you get is mostly just the force on your arms, so the tendency is to think that by pulling the sail in hard, you must be getting lots more thrust because you can feel more force on your arms. This is NOT the case.
Sideways force does not equate to forward thrust. And it's the forward thrust that you need. The sideways force is an unwanted result of generating the forward thrust. It is just wasted effort and should be minimised.

As the forward speed increases you can progressively pull the sail in because the apparent wind then acts to reduce the angle of attack.
At any speed it is still best to keep the angle of attack to the apparent wind at 15 degrees. You can find this point by continually letting the sail out a few degrees and check if the board slows down. If it doesn't slow down then it means you have got the same forward thrust for a reduced sideways force and consequently, a reduced risk of spin out.
I know everybody always says to pull the sail in & close the gap but while this may help drag the last knot out of a breeze that's exactly right for the rig, it will certainly result in more spin outs under anything but ideal conditions for the board/sail/fin combination which you might be using.

Hmmm,.. this is an awful lot to say on the subject. I should have just said, try letting the sail out a bit. But anyway, now you know why.