Is there an ideal mast foot position regardless of sail size or should sail size dictate where mast foot goes ? Or is mast foot position more controlled by wind strength when using any given sail size ? The first indicator mark on the stingray is 130 . would I ever need to go to say 128 in very light winds with an 8 m sail . Thanks

Personal preference is one of the determining factors.
Freestylers like mast foot close to front foot.
Racers like a bit of distance, 22" to a bit more, for stability.
Windspeed for sail and foil size contributes, as does foil placement and rider weight.
Start near the middle, and adjust for comfort.

I adjust mastfoot and staps positions to make the transition from planing to flying smooth and gradual. If I you have to push hard on the back foot to get going, move everything back, if you breach easily when flying, move forward.

By testing different positions, I found the balance point for the mast foot where front and rear foot pressure are equal in flight, and leave it there. Sail size (5.8-9.0) and wind speed (8-24 knots) do not change the balance point as far as I can tell, neither does front wing on an AFS W95 with F series wings (770-1080 cm2), have not changed the rear wing but that could affect the balance point.

Mastfoot position is more dependent on foil than on board. For most freeride foils somewhere between 95-105cm from the front tuttle bolt (or front of the foilmast) is a good starting point. For racingfoils think 105-115(as far forward as possible).

The front wing position of the foil (and to a lesser degree backwing position/angle) mostly determines the power in the kit, the mastfoot should be placed accordingly, taking into account sail downforce/weight (a 4cam racingsail has a lot more downforce than a 3 batten wavesail) second and pretty much all other variables after that.

I have the Stingray 140. I use it with LP and AFS-2 foils (both deep tuttle), both of which have the same front wing position. For a 7.0 Flyer, I set the mast foot at 42 inches in front of the front fin screw head. For a 5.0 Revolution, I set it to 45 inches. Footstraps are forward. I weigh 195 pounds.

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Sandman1221 said..
By testing different positions, I found the balance point for the mast foot where front and rear foot pressure are equal in flight, and leave it there. Sail size (5.8-9.0) and wind speed (8-24 knots) do not change the balance point as far as I can tell, neither does front wing on an AFS W95 with F series wings (770-1080 cm2), have not changed the rear wing but that could affect the balance point.

After reading Segler's post thought I should add that my sails are all Aerotech Freespeeds model year 2016, maybe different sail lines need the mast foot at different positions to balance everything.

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segler said..
I have the Stingray 140. I use it with LP and AFS-2 foils (both deep tuttle), both of which have the same front wing position. For a 7.0 Flyer, I set the mast foot at 42 inches in front of the front fin screw head. For a 5.0 Revolution, I set it to 45 inches. Footstraps are forward. I weigh 195 pounds.

So you have the smaller sail set 3 inches forward of the larger sail? Interesting. Why do you think?

I fly the stingray 125. With my fringes I have them all the way back (about 125 cm). With my Ftype 5.8 I'm at the 130 mark. I usually run my foils all the way back at the Tuttle position even though I use the track. 185 kgs.

But I'm not saying I'm right. Always want to get better.

(Hoping to pick up the new SR115 as soon as it's available.)

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BullroarerTook said..

segler said..
I have the Stingray 140. I use it with LP and AFS-2 foils (both deep tuttle), both of which have the same front wing position. For a 7.0 Flyer, I set the mast foot at 42 inches in front of the front fin screw head. For a 5.0 Revolution, I set it to 45 inches. Footstraps are forward. I weigh 195 pounds.

So you have the smaller sail set 3 inches forward of the larger sail? Interesting. Why do you think?

I fly the stingray 125. With my fringes I have them all the way back (about 125 cm). With my Ftype 5.8 I'm at the 130 mark. I usually run my foils all the way back at the Tuttle position even though I use the track. 185 kgs.

But I'm not saying I'm right. Always want to get better.

(Hoping to pick up the new SR115 as soon as it's available.)

Lighter sails put less pressure on the mast foot. As well, many folks use the harness less with small sails which means, for most, less pressure, too. Moving the mast foot back balances this out. See WhiteofHeart's second paragraph from above.

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WhiteofHeart said..
The front wing position of the foil (and to a lesser degree backwing position/angle) mostly determines the power in the kit, the mastfoot should be placed accordingly, taking into account sail downforce/weight (a 4cam racingsail has a lot more downforce than a 3 batten wavesail) second and pretty much all other variables after that.

Yes, it's about mast base pressure. All other things being equal, the smaller the sail, the further forward the mast base. We learned this in the old days with formula.

And yes, there is also the variable of sail type and cut. Foil sails generally are designed with the max draft further forward. This permits the rider to mount them further aft. You have to experiment to find out what feels balanced. The numbers I show above work for me. They worked yesterday on the Snake River with my Flyer 7.0.

Freeride foils being used for maneuver based riding run the mast base all the way back and the straps all the way forward regardless of sail.

Freerace foils will change depending on sail size and rider preference.

I mostly use 6.5 and 5.6 m sails with my Stingray 140, with the mast foot at 131 cm. Boom height matters a bit - if the boom is very high for extra power at light wind, the mast base can go a bit more forward. The mast base further forward can also make all-out pumping easier.
Every now and then, I start foiling with the mast base all the way back (when I put it there to carry the board to the beach, and forget to move it). That never lasts long, since it feels wrong, and I move the mast base further forward when I discover the mistake.

I'd be surprised if an 8 m sail would work well in further back. But surprises happen sometime.

I contend that a 8m sail all the way back is correct. If you move it forward, good luck getting it to lift into flight. You will burn out your back leg trying. This is with a freeride foil. If you use a race foil, no problem since the race wing is further forward to start with.

I presume your 131 is the marking on the board, which is different from the distance to the front fin screw. My favorite distance to the front fin screw with a 6.4 sail is 107 cm with freeride foils. I use this distance for three very different boards.

The marking on the sail mast track is from the tail of the board. On the SR125 there is 25 cm from the tail to the front bolt. The distance between the foil lift position to the front bolt depends on the foil of course but I have the approximate numbers for the Fanatic Flow series. The Stingrays also have a foil track of course and that's what I use.

When I free ride/swell ride I have the foil all the way back (Flow 1500) and sail all the way back. I don't feel any burning of the back leg, but thedoor - who is lighter by about 10 kgs- thinks the foil is too far back.