Equipment: KFA carbon foil and Liquid Force fish 5'3"
Before drilling four holes in a completely undamaged board, what is the optimum position for the foil?
Reading, beginners place the foils far back as possible and gradually move the foil forward until an even balance is experienced. Ideally one would place the foil in the correct position and gradually move their stance back.

I can give you measurements for the LF foil but it may not be suitable for the KFA foil...

On my board (Sroka) back foot over the mast is optimum position. The back strap which I don't use is about 200-250mm behind this. I recently tried some boosting on my foil board and of course have to use the back strap. This makes every thing totally out of whack and I will need to rig up some way of positioning the back strap over the mast

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snalberski said...
On my board (Sroka) back foot over the mast is optimum position. The back strap which I don't use is about 200-250mm behind this. I recently tried some boosting on my foil board and of course have to use the back strap. This makes every thing totally out of whack and I will need to rig up some way of positioning the back strap over the mast

No you don't. Just adapt your technique. If the board and board are a matched set, foot over the mast is the wrong position

You don't want to move the back strap forward. You want to move your heqd and shoulders forward a touch. It's all about body mass and centre of gravity and very little to do with foot position. Once you work it out you'll wonder what the problem was. It just takes practice.

Looking at images of people foiling, the general consensus by observation shows the centre line of the mast lining up with the front fixing of the back strap.
To be clearer, the back foot is placed slightly behind the mast in most observable situations. This seems to make sense from a physics point of view.

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dorothyinste said..
Looking at images of people foiling, the general consensus by observation shows the centre line of the mast lining up with the front fixing of the back strap.
To be clearer, the back foot is placed slightly behind the mast in most observable situations. This seems to make sense from a physics point of view.

There is no general consensus. Different design, different placement. See Airush foil mounted all the way to the back...

You need to get in touch with KFA (or a KFA owner), make sure you know exactly which model you have (MK1, MK2. MK3 or Mako...) and ask them for the distance between the back insert of the front foot strap and the front screw of the foil mast. Having tracks fitted instead of 4 holes will give you more flexibility to adjust your set up. On my board, I have 10" tracks that give me 6 cm adjustment option.

Any shaper can fit those tracks for about $150-$200. If you do it yourself, you are up for $60 worth of materials. Best to make a box with PVC foam to make is stronger as you don't want your beloved foil to get away from the board....

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Livit said...

dorothyinste said..
Looking at images of people foiling, the general consensus by observation shows the centre line of the mast lining up with the front fixing of the back strap.
To be clearer, the back foot is placed slightly behind the mast in most observable situations. This seems to make sense from a physics point of view.

There is no general consensus. Different design, different placement. See Airush foil mounted all the way to the back...

You need to get in touch with KFA (or a KFA owner), make sure you know exactly which model you have (MK1, MK2. MK3 or Mako...) and ask them for the distance between the back insert of the front foot strap and the front screw of the foil mast. Having tracks fitted instead of 4 holes will give you more flexibility to adjust your set up. On my board, I have 10" tracks that give me 6 cm adjustment option.

Any shaper can fit those tracks for about $150-$200. If you do it yourself, you are up for $60 worth of materials. Best to make a box with PVC foam to make is stronger as you don't want your beloved foil to get away from the board....

The Hover Glide is mounted all the way to the back and they recommend the straps all the way forward on the AA, but that still puts the rear foot behind the mast...

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dorothyinste said..
Equipment: KFA carbon foil and Liquid Force fish 5'3"
Before drilling four holes in a completely undamaged board, what is the optimum position for the foil?
Reading, beginners place the foils far back as possible and gradually move the foil forward until an even balance is experienced. Ideally one would place the foil in the correct position and gradually move their stance back.

Hey buddy, in my experience it's very hard to nail the hole position the first time. What I have done in the past is make an adjustable adaptor plate that lives between board and foil, it's bolted in original board holes (bit tricky if your not mechanical type). Then give it to someone who can ride a foil pretty well and they'll say to move forward or back. Pretty sure approximate center of lift front wing on Foil fish is about 50mm further forward relative to mast than KFA. So as a starting point design plate such that KFA bolts on 50mm further forward on board.

It depends on how the foil is setup - I have learnt.

I think in general - as speed increases, the rear foil generates downforce from the rear wing, that counters the underwater drag induced from the entire foil, that is a nose down rotating force.

Not all rear foils give downforce, and you would need the mast position further forward to shift your weight back in this case, the faster you go, the more your weight needs to be shifted back to stop nose dive.

If the rear foil makes too much downforce with speed, or say - not enough at low speed but enough at high speed, your going to have to shift your weight from rear to front as speed increases.

My max speed on my bunky#1 foil, was due to that - no rear downforce, more drag, and when I got to about 15 kts, I was doing a 1 legged rear foot crunch on the transom of the board to stop nose diving, i shifted my mast forward by about 8 - 10 inches, to get a normal twintip feel.

Ah yes! I forgot about rear wing adjustment. If you can't be sure it's not already set in a serviceable position then this adds another layer of tricky. As a rough guide, if when up and foiling at low speed you have to stomp on rear or front foot the mast needs to move. If as speed increases, you have to start stomping on rear or front foot (even more the faster you go) the rear wing needs adjustment. If rear wing or mast position way out it can be hard to know which to adjust. You don't want to try and learn on a foil that's set up bad, get someone to test if you can.

Good advice !

Got the bolt position spot on first time! Either it was luck or one's basic assumption and observations were correct. Either way, one is stoked!