On DW boards what is the distance between the board plus foil centre of gravity and the centre of lift of front foil?
I have my centre of lift position about 50 to 75mm forward of centre of gravity position on both my long prone and wing board. In this position I can handle pop up and board stays level when I'm turning.
To my eye, masts on your sup foil boards seem to be maybe 200mm in front of balance point (except for maybe the barracuda). Is this just an illusion because of the narrow tail and the fact they have more volume forward?, or is the seperation between the two getting bigger?
Boards are much more nimble with mast forward but I'm not sure how far I can push it.
Thanks

I think, it depends of the shape. Where you want to paddle...is probably where you want to fly, so you don't have to move your feet after lifting off? Good question. If you have all the weight at the back, a large chunky heavy tail and a super slim nose...further in front would bring you further away from the heavy part...would you feel more nimble?

Not sure this answers your question because I don't go by balance point, but my 8'2" has it's total volume center at 48" from tail, expected static CG about 45.5" from tail (nose out of the water, tail pretty much awash) and the center of the boxes are at 33", so just about 12" behind the expected CG while standing on the board. This setup is good with the mast pretty much right in the middle of the box with back foot right on top of the mast

Maybe I should have asked if boards are balanced tail heavy. I'll pick up a few when I get the chance.

The weight will be around the foil boxes with high density foam/ a few layers of carbon, minimal weight at the nose.
So in theory they are 'tail heavy'

Measuring from the tail of the board should have gone out of style when Kai Lenny's chopped off the tail of his race board 8 years ago. This is more true with the longer downwind boards.

We are flying aircraft. There is a Center of Gravity (Mass). Essentially it is the balance point of the board. Your feet will straddle this natural Balance point like a seesaw. The Center of Gravity has to be slightly AHEAD of the Center of Lift to be aerodynamically stable. The Center of Lift is ~ the 1/3 Chord point on the foil. This is 1/3 the way back from the leading edge of the foil to the AVERAGE Chord.

Fortunately with Axis gear this corresponds well with the front of the Axis Fuselage.
Key assumptions:
1) Your feet should straddle the Center of Balance of the completed Board making the CG of Person and Board the same
2) The Center of Lift is the 1/3 Chord point of the Airfoil (Front Wing)
3) The CG should be 2" in front of the Center of Lift

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'The CG should be 2" in front of the Center of Lift'
Great. That's what I was after. Thanks Beasho and others.

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AUS126 said..

'The CG should be 2" in front of the Center of Lift'
Great. That's what I was after. Thanks Beasho and others.

Sounds like maybe you are shaping a new board? Good idea to follow the guidline above and use 16" tracks. I've had a very difficult time finding the right spot on a 6'9" FFB Dagger that I wanted to use for prone and wing (it's way too small for me to sup paddle.) Using the Gofoil V2 mast and a large front wing, the best I can do is as you said, "about 50 to 75mm forward of centre of gravity" due to track placement. This would be fine for sup paddling and winging, but for prone it's all wrong on this board, perhaps not being designed for my weight or usage, or a Gofoil V2. I suspect Beasho may be correct even though it would appear the mast would be too far back if I could move it there... Given the major differences in body types and foil lift spots, the 16" tracks would be very helpfull.

I had run these numbers a while ago. But I have the advantage of 2 other board builders in town. They have built 30+ boards, and I am on board number 3. We would argue a lot about these placements. However we have come to a consensus on these measurements and are usually within +/- 1".

That said I did use a 16" set of tracks in my latest build. It is shown in these views. The 16" Chinooks allow for the advanced + fuselage and even more shortening if necessary. The box butts right up against the Center of Gravity, shown as Center of Gravity (CG) drawn on the board.

My set up is using the Advanced model e.g. 40 mm shorter and therefore set 10.5" from CG to Center of Mast shown.

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Beasho said..
Measuring from the tail of the board should have gone out of style when Kai Lenny's chopped off the tail of his race board 8 years ago. This is more true with the longer downwind boards.

We are flying aircraft. There is a Center of Gravity (Mass). Essentially it is the balance point of the board. Your feet will straddle this natural Balance point like a seesaw. The Center of Gravity has to be slightly AHEAD of the Center of Lift to be aerodynamically stable. The Center of Lift is ~ the 1/3 Chord point on the foil. This is 1/3 the way back from the leading edge of the foil to the AVERAGE Chord.

Fortunately with Axis gear this corresponds well with the front of the Axis Fuselage.
Key assumptions:
1) Your feet should straddle the Center of Balance of the completed Board making the CG of Person and Board the same
2) The Center of Lift is the 1/3 Chord point of the Airfoil (Front Wing)
3) The CG should be 2" in front of the Center of Lift

A question on balance point. if I shaped a board and rested the mid point on a broom shaft so that it was balanced like a see saw, would this be the balance point. If I then added a HD foam track block where the MM position would be middle of track (under back foot) would this then alter the balance point. In the past I think where my feet would be and put the tracks under back foot position. So far so good. Thanks.

@beasho great explanation and detail. For my next board looking to get a bit more precise on mast placement and your explanation is very helpful. However I'm struggling to predict the centre of gravity of my final board before I place the boxes.

Here are the Steps for mast box placement I'm considering:

(1) We want the centre of gravity of the finished board to be ~50 mm in front of the centre of lift of the foil

(2) So first of all we determine the distance from Centre of Lift to the Middle of Mast. For Code foils that is around 205mm and add 50 mm per (1) (side note interesting that there are only a few mm variation between different code foil sizes ranging from 720s and 1300s)

(3) Find Centre of Gravity on the blank and mark it.
(4) measure ~255mm per (1) and (2) towards tail and add another ~75mm as the CoG will move back with your reinforcements. Mark this point on blank.

(5) Place mast tracks, HD foam and ~200g in weights for resin and additional reinforcements over this mark as they would once installed.

(6) Find the centre of gravity again and mark it again

(7) Now measure back to your MoM. If its more than 255 mm move the tracks slightly forward. If its less than 255 mm move the tracks slightly back.

(8) Repeat this until you find the point where your board with reinforcements are approximately 255 mm behind the CoG with the tracks and reinforcements resting on the board.

(9) Now for most shapes there will be a lot more surface area in front of this estimated CoG than behind so with the lamination we add more weight to the front thus moving the CoG forward again. But that gets tricky to calculate now unless I somehow manage to calculate the point masses from a reference point ( ie tail ) and then take the weighted average from it to come up with a likely adjustment forward which with the complex curves etc will never be precise anyway.
How did you this on your boards especially for (9)? Am I overthinking this and is there a good rule of thumb?