Foil Placement

Forums General Chat Foil Placement

  • Post
    Kane DW
    Moderator

    Saw something about this commented on another post and though I’d share my method. I come from an rc flying background and this method is based off my experience with that.

    The jist of it is that the center of gravity of the setup must be in line vertically with the front wing. The theory behind this is that the foil should only react to your weight shift and not be affected by forces in the rest of the setup. It’s also another way to tune the feel of you foil just like tailwing size and angle.

    Disclaimer: this may not work on all setups, lightweight boards under 4’4”-4’6” probably won’t balance and the effect of the CoG being slightly off won’t make much of a difference. Optimal balance will differ between foil brands and characteristics. Tuning still applies.

    Start by loosely attaching the foil to the board in a position that looks right. Hold the setup upside down by the approximate center of lift of the wing. This spot should be around 25-30% back from the leading edge on high aspect wings and about 40% on more normal, delta shaped wings. Once lifted, eye how level the board is. If it’s tail heavy, more the foil back. If it’s nose heavy, move the foil forwards. I use level as a baseline for new setups to work from. Usually is within 1-2cm if not dead on.

    The real magic of this method is the tuning of it. Any setup that it too nose heavy will have a tendency to tap the rail in turns, the harder the turn the worse the problem. If you find yourself catching rail in hard turns this may be your problem. Any setup that is too tail heavy will tend to breach the wingtip in hard turns. Foil placement has the biggest effect in turns because the extra downward Centripetal force on the setup makes balance more critical. Foil placement is almost like your mid turn ride height adjustment!

    This gets even more complicated once tailwing tuning is taken into account. Foils that need more font foot pressure as speed increases need to be nose heavy and the opposite with foils that need more back foot pressure as speed increases. These counter the change in foot pressure due to acceleration and gives a more neutral feel through the turn.

    Example of the disclaimer is my prone setup. Balances tail heavy but has still been tuned in the way explained. Feels perfect!

    In conclusion, breaching tips in turns = foil back and touching rail in turns = foil forwards.

    Happy tinkering

Viewing 9 replies - 1 through 9 (of 9 total)
  • Replies
    CW
    Participant

    Thanks for sharing this Kane, I’ve been thinking about cog for a while and you’ve promted me to do the checks.
    It all makes sense. No different to an aeroplane, if it’s trimmed right they are nice to fly.
    It would be good if the wing producers would mark the cog on the wings. Pretty sure the design software gives this information.
    Also have you considered transferring this line to the deck of your board to use as a reference.

    Moonwalker
    Participant

    Interesting read. Thanks for taking the time to share your knowledge, appreciated!

    Kane DW
    Moderator

    I can get cg measurements for np and signature wings if anyone wants! Translating the mark on to a bird could be interesting but every wing and foil would need a different mark. The cg check is really just a baseline to use the tuning method from.

    Foil Feed
    Keymaster

    This is a great way to find your perfect foil position. This is the technique I always use and it’s a great starting point. It ends up very close to where I find the final sweet spot.

    ScotY
    Participant

    I checked by board/foil setup today. I’m on a custom Kalama standup board that I bought used so it’s not custom for me. 6’x 28” and maybe 115-120 liters. I weigh 185 lbs and have an Armstrong 1600 wing, 60cm fuselage, old style tail and zero shim. I normally have the mast in the center of the fin boxes…this works okay for me when on the foil and also for standing/paddling around. I would say I’m an advanced beginner, started about 10 months ago.

    This setup balances just a couple of inches behind the very front edge of the wing so very nose heavy. I moved the mast forward, maybe about halfway from the middle to as far forward as it could go. This moved the CG back closer to where I think the wing should balance, not not quite enough. It wasn’t the greatest day today but I want to say the board feels more responsive on foil. The problem is it’s incredibly hard to balance when just standing and even when paddling around. With the mast in my usual position, it’s quite easy for me to stand/paddle. I’ve tried moving the mast forward before but not with the intent of determining if it foils better. But I quickly moved back to the middle because it was hard to manage when paddling. It’s amazing what about 1/4” of change does to the handling of this setup! From really easy to incredibly hard.

    So, I’m wondering what causes this. I’m assuming that moving the mast forward has less of a skeg/keel effect, not sure how to explain. Like if you have a big enough skeg on a board, when you paddle and have a little forward motion, the skeg keeps the board stable. Without the skeg, it would be much harder to paddle and balance. Hope that makes sense? Or, maybe it’s the entire mast/wing that, if more far forward, disrupts your balance because it’s more closely right under your weight?

    The reason for my rambling post is to try and figure out if, perhaps, standup foil board design needs a complete overhaul. I’d imagine that unless your board is 5’ or less, it’s gonna be nose heavy. And if you can stand up on a 5’ board, you probably won’t care how hard it is to balance on. My setup with the mast forward requires me to stand more forward when paddling for the wave, to the point that the deck is more or less level with the water and on the verge of pearling. I find I have to lean back a bit to make it work. Maybe counterintuitive, but maybe I need more foam in the nose. Thicker foam might not add much more weight so the swing weight wouldn’t change too much but buoyancy would naturally increase.

    Anyway, in order to get the CG right for my setup (which I’d assume is fairly typical), I need a board that I can still stand on. I’ve been thinking about getting a new board but not sure which direction this needs to go.

    Thoughts anyone?

    Kane DW
    Moderator

    Sounds like the middle position is pretty close to balanced, you said it balances a couple of inches behind the leading edge? That’s pretty close to perfect! I’d suspect the reason it gets harder to paddle is because you moved the yaw pivot point (the mast) closer to your body. When you paddle and the foil yaws side to side it wants to roll as well. This makes it less stable. One thing that could help is adding a fin near the nose like Dave and Austin use to keep it tracking straighter.

    ScotY
    Participant

    I’m too lazy to put the foil on the board at home so just kinda doing it in the parking lot.😂 No way to measure, just kinda eyeballing it.

    Anyway, I think I didn’t explain well. With the mast where it’s comfortable to paddle, the balance point is way forward on the wing. I haven’t tried yet, but I think I need to move the mast as far forward as it will go in the tracks and I still don’t think the board will balance on the CG…close but maybe not quite.

    That’s a good theory about the yaw/roll. Never thought of the roll translation. Went out today and I seem to be getting used to it. Will try again next time out.

    hdk
    Participant

    Hi does this method work on production (heavy) wing foil boards?
    hdk

    hdk
    Participant

    This method does work very well for wing with a fanatic skywing 5’4″ and go foil gl210 nl160 nl130 and 9.5 pedestal and 14.5 flip tail. Don’t even move the mast between all the wings will fine tune as I go though!
    Thank you Kane!

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