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Distance from Foil to Mast foot

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Created by tbwonder 1 month ago, 29 Apr 2019
tbwonder
NSW, 183 posts
29 Apr 2019 4:18PM
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I got my original setup information from the Slingshot Foil Academy. The suggestion is that the sweet spot is 43" (109cm) from the front Tuttle screw to the centre of the mast foot. Now I see in the Balz Muller video he is suggesting that 85cm is the place to be! This is a huge difference. Just wondering what distance are you finding to be the sweet spot and with what size sail. I am currently at 104cm with a 6.5m sail and about 101cm with 5.5m using the Slingshot Ghost Whisperer 101 foil

PatK
27 posts
29 Apr 2019 2:32PM
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I tried the most back position possible with JP 150 foil board at 100cm and it felt nice with the 8.6 severne overdrive.
Much better than in middle position. Earlier lift and good control.
The 85cm from Balz is for his very small board and sail. But the note to try moving it back is good.

Subsonic
WA, 1607 posts
29 Apr 2019 5:35PM
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I run mine at 111 (just forward of middle) on my JP 150 with the RSX carbon foil. That seems to be a sweet spot for my set up. I've tried running with it further back and it seems to make the setup unstable. Im wondering if Balz comments were more aimed at free ride style set ups.

i think base position is probably going to vary set up to set up, depending on where everything else is, and what kind of breeze you're using it in.

LeeD
466 posts
30 Apr 2019 2:08AM
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Rather than one specific location, perhaps the NEED should be considered.
Track forwards should be more stable and slower to fly.
Track back is more responsive and quicker earlier flight
What does the sailor need?

duzzi
63 posts
30 Apr 2019 8:09AM
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tbwonder said..
I got my original setup information from the Slingshot Foil Academy. The suggestion is that the sweet spot is 43" (109cm) from the front Tuttle screw to the centre of the mast foot. Now I see in the Balz Muller video he is suggesting that 85cm is the place to be! This is a huge difference. Just wondering what distance are you finding to be the sweet spot and with what size sail. I am currently at 104cm with a 6.5m sail and about 101cm with 5.5m using the Slingshot Ghost Whisperer 101 foil








I am a beginner at foiling but I am sure that exactly like in other technical version of the sport the distance fin/foil to mast base depends on the fin/foil, the sail, the weight of the sailor, the boom position, the strap position (and the cycle of the moon). Balz 85cm rule or Slingshot 109 rule are probably correct, on average, for the set up they are talked about, otherwise with a different set up I am afraid one has to find what works by experimentation.

I am such a beginner that on my board I put the mast 1/3 forward and always left it there. Same for the rear wing: put it in the center in neutral position and left it there. Same for the boom 1 cm lower. Same for the harness lines, 3 cm shorter. Too many variables otherwise for a pilot who is happily yoyo-ing around like a cowboy on a crazy horse.

30 Apr 2019 8:59AM
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tbwonder said..
I got my original setup information from the Slingshot Foil Academy. The suggestion is that the sweet spot is 43" (109cm) from the front Tuttle screw to the centre of the mast foot. Now I see in the Balz Muller video he is suggesting that 85cm is the place to be! This is a huge difference. Just wondering what distance are you finding to be the sweet spot and with what size sail. I am currently at 104cm with a 6.5m sail and about 101cm with 5.5m using the Slingshot Ghost Whisperer 101 foil


I think what Balz is trying to point out, is not to go by the exact measurements that he mentioned, but more the balance of the foot pressure on the board and just making a point of thinking about getting a lot of lift out of the foil and in the same time control it. Mostly with your front foot.

So in general it is better to go for more front foot pressure, than back foot pressure.
Maybe even the total opposite ratio of front and back foot pressure, compared to normal windsurfing?

The front foot pressure ensure you are more 'on top of the gear' and control is better.
If you need more lift / or if the wind drops, then you have room to move back a bit to get more lift and if you hit a gust standing more upright and forward, then it is easier to sheet the sail out and have control and push the board down.

If you have a set up where a lot of back foot pressure is required (and also the need to have the sail raked more back), then from this position it can easily get more out of control. - Like Balz pointed out,,

Also I think it is important to point out that this style is aimed more towards the freeride / wave / freestyle / cruising foils

For full race set up with faster foils / narrower wings and much wider boards with straps near the rails + big rigs, it is all a slightly different story,,

Tbwonder: I do have the Slingshot Ghost Whisperer 101 as well on my 125 Wizard board. It'is such a easy and slippery set up,,
Compared to the Hoverglide setup 76cm infinity wing, that I also use a lot (that I normally run in the middle of the track with a 5.9 / 5.3), I do run the Ghost Whisperer another 4-5 cm back. Not sure of the measurement, as I do all this trimming by feeling. If I go smaller sail sizes then approx 1-2cm further back again.

Don't get 'trapped' in the numbers to much as we all have different foils / rigs / boards / weight etc.
But yes, it is indeed a good tip to go back in the track until you get the balance right, whatever that measurement is.

The foil Balz is using on the video is the same as the Slingshot Ghost Whisperer 101 carbon by the way,,

tbwonder
NSW, 183 posts
30 Apr 2019 10:07PM
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There are indeed many many variables. As a beginner you need to guess a starting point for each variable. I used the 109 slingshot measurement at the outset. Overtime I have raised the boom 8cm higher than my Slalom position and shortened my harness lines from 28 back to 24. I have cut the 109 to about 104. Each change has been gradual as it does not always feel better at first.
When I saw Balz on a foil just like mine, suggesting that 85cm was the spot to start at I was really surprised this is not a small change. This is a totally different setup. I am keen to try it, as I like the idea of being able to get in both straps before pumping onto the plane. My fully back position is about 92 cm, hopefully I will get to try this tomorrow.
I know everybody has different foils, boards, body weights etc but it would be interesting if people could actually quote the measured distance in their comments.

segler
95 posts
30 Apr 2019 11:18PM
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It will definitely be variable, but you need a starting point. I have noticed that the combination of (1) front wing at the midpoint between front and rear feet (footstraps), and (2) 44" (inches) from the foil mast leading edge to the sail mast base position, gets you a good starting point. You adjust from there. That is for a 6.4 sail. For a bigger sail, go further back, for smaller, further forward. The point is to balance the mast base pressure, which is crazy critical for windfoiling.

I made this youtube 16 months ago. The settings work as a good starting point.


segler
95 posts
30 Apr 2019 11:22PM
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After 94 sessions on this gear, these settings still work. 43"-44" is the sweet spot recommended by such luminaries as the team riders at Sailworks. See sailworks.com for comments about balancing your gear.

Bender
WA, 2056 posts
1 May 2019 8:10PM
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Well my set up is totally different. I had not measured it I just went off what felt right and gave me 50/50 leg pressure. Reading this thread made me get the tape measure out. So the stats are.
Board is a 7'8" Smik sup I had converted to a sup/windfoil board.
The foil is a cheap Chinese knock off ( I fattened up the front wing considerably.
The board has tracks and for sup surfing I ride it all the way forward. My first sail I put the foil all the way back. This was horrible as to fly I had 90%back leg pressure. After 4 sessions I now windfoil with the foil in the same positson as sup surfing. It measures 80cm from the centre of the mast to dead centre of the mast track. I usually run it all the way back. Got any tips for a newbie to foiling. I am unable to line up the leading edge of the foil with the mid point between the straps but it works ok








Paducah
359 posts
1 May 2019 9:43PM
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What's your stab angle? What size sails are you using?

WhiteofHeart
123 posts
2 May 2019 3:44AM
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I ride my mastfoot at 82.5cm (most backward position for me, my foilboards' 25cm track ends where the one in my slalomboard begins haha) currently with most sails, independent of foil (Lok? LK1 Race, or F-One Levo Freeride), the Lok? is quite front foot powered (more frontfoot than Starboard GT for ex.), the F-One a little backfoot on a normal slalomboard. I recently recieved a proto which has the backmost position a pinch further forward than Im used to, but I asked for the track to be moved back in the next version for it feels stretched and am gonna hopefully try a track starting at 75cm soon. Have to say I ride single backstrap right on top of the tuttle (so also a little further back than Balz), and my strap spacing at 38cm (normal is 42). Very compact, very nice for pumping / flying early / jibing / downwind and upwind 360s etc. Max sailsize 4.9 from about 10kts up, down to 3.0 and recently even 2.5m2.

I rode a Slingshot on Tenerife and felt personally the "adviced" setup is too backfooted, I like more front foot power. (I can fly balanced on both feet with my front foot about 20cm in front of the front strap and the backfoot halfway between the straps)

I spoke with Balz 2 years ago when we were both designing our own foilboards and exchanged settings with him, at that time he had his backfoot further back aswell, makes me wonder whether the current position is due to construction problems (we ran into those) or because he likes it a little further forward / maybe closer to the frontstrap. He said he liked his frontstraps where they were, only 20cm behind the masttrack.

When racing I have the mastfoot further forward, between 105 - 111 cm, depending on wind, using 8.6 freerace or 9.9 foilrace sails on a formula, but I keep the straps in the backmost positions and quite narrow.

i put the bigger sails further forward, otherwise the stance feels funky (harness lines over the backstrap hahaha). This does mean I compensate by using my most powerful foil with a lot of rake on the stab to max out power.

p.s. Got a little heavier with 88kg's all muscle for my 192cm length ;).

Bender
WA, 2056 posts
2 May 2019 6:50AM
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Paducah said..
What's your stab angle? What size sails are you using?


My stab is level. I use 4.7, 5.3 and 5.8m wave sails

Paducah
359 posts
2 May 2019 10:22AM
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Bender said..

Paducah said..
What's your stab angle? What size sails are you using?



My stab is level. I use 4.7, 5.3 and 5.8m wave sails


So... 0 degree angle to the wing? Sorry if my question seems repetitive, I want to make sure I understand correctly before launching unnecessarily into something.

Bender
WA, 2056 posts
2 May 2019 11:03AM
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Paducah said..

Bender said..


Paducah said..
What's your stab angle? What size sails are you using?




My stab is level. I use 4.7, 5.3 and 5.8m wave sails



So... 0 degree angle to the wing? Sorry if my question seems repetitive, I want to make sure I understand correctly before launching unnecessarily into something.


yes

segler
95 posts
2 May 2019 10:17PM
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There is a way to measure the stab angle with respect to the front wing:


Paducah
359 posts
3 May 2019 4:55AM
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Bender said..


Paducah said..



Bender said..




Paducah said..
What's your stab angle? What size sails are you using?






My stab is level. I use 4.7, 5.3 and 5.8m wave sails





So... 0 degree angle to the wing? Sorry if my question seems repetitive, I want to make sure I understand correctly before launching unnecessarily into something.




yes



0 makes it more difficult for level and stable flight - even ignoring the front/back issue. I've measure several prodution foils and they seem to be around 2.5 degrees (up elevator ie front edge pointing down) and my Starboard GT was more (may not have been accurate).

Read this thread why neg stab angle is necessary for stable flight both on airplanes and foils (look for CJW's comment): www.seabreeze.com.au/forums/Windsurfing/Foiling/Does-a-longer-fuselage-make-a-more-stable-ride-?page=1#13

or get google to translate this glissattitude article for you if your French is like mine:
marseille.glissattitude.com/blog/windfoil-calage-des-stabs-en-foil.html

Thanks to segler for posting that video so I don't have to dig it up. Many cell phones can be used as a digital level with free/cheap apps, btw. No need to spend money on one.

Bender
WA, 2056 posts
3 May 2019 8:10AM
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Paducah said..

Bender said..



Paducah said..




Bender said..





Paducah said..
What's your stab angle? What size sails are you using?







My stab is level. I use 4.7, 5.3 and 5.8m wave sails






So... 0 degree angle to the wing? Sorry if my question seems repetitive, I want to make sure I understand correctly before launching unnecessarily into something.





yes




0 makes it more difficult for level and stable flight - even ignoring the front/back issue. I've measure several prodution foils and they seem to be around 2.5 degrees (up elevator ie front edge pointing down) and my Starboard GT was more (may not have been accurate).

Read this thread why neg stab angle is necessary for stable flight both on airplanes and foils (look for CJW's comment): www.seabreeze.com.au/forums/Windsurfing/Foiling/Does-a-longer-fuselage-make-a-more-stable-ride-?page=1#13

or get google to translate this glissattitude article for you if your French is like mine:
marseille.glissattitude.com/blog/windfoil-calage-des-stabs-en-foil.html

Thanks to segler for posting that video so I don't have to dig it up. Many cell phones can be used as a digital level with free/cheap apps, btw. No need to spend money on one.


Thanks a bucket load for that info.It makes a lot of sense. I will have a play with some washers tonight

Paducah
359 posts
3 May 2019 10:28AM
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Bender, glad you found something worthwhile in the post. Good luck.

IndecentExposur
93 posts
3 May 2019 8:05PM
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...I'm not a fan of modifying the stab angle. I creates drag at higher speed. The video did provide some nice insights on measuring stab angles; but wouldn't getting better technique compensate for all that? I guess I'll be swimming like the dolphins.

CJW
NSW, 1538 posts
3 May 2019 11:58PM
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IndecentExposur said..
...I'm not a fan of modifying the stab angle. I creates drag at higher speed. The video did provide some nice insights on measuring stab angles; but wouldn't getting better technique compensate for all that? I guess I'll be swimming like the dolphins.


I wouldn't be so worried about it, we are talking fairly small reductions in top speed here and given how much easier it makes the foil to sail it's an easy trade off to make. If you are racing it's even more of a no brainer as your VMG is so much better with a higher lift setup it's not even funny. I'd bet you'd be easily faster on average on a well balanced setup than one trimmed for 'max speed'.

It's also a bit difficult to compare stab angles between different foil designs as wing design and fuse length has a massive effect. It's why all the race foils have long fuselages, because for the same stab angle as say a short fuse they have a much bigger longitudinal dihedral. So, to achieve the same balance you can run a lower stab = faster...or you can tune to to be way more powerful

RE the mast position it's all been covered well above. The only thing i'd say is it's very setup dependent. You're never going to be able to sail a starboard race foil with that short a mast-foil distance as you simply would not be able to keep it in the water. To get everything optimum and efficient it's all a balance between stab angle, mast foot position and foot strap position. Don't be afraid to experiment.

Bender
WA, 2056 posts
3 May 2019 10:14PM
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Thanks for the help. I used a free level app on my phone. With two washers the stab angle is 2.5deg now. Looking forward to testing it out tomorrow
I will leave all the other settings as is and see what difference it has made. Once again thanks for the advice
I'm still very new to foiling. Cheers Bender

berowne
NSW, 261 posts
31 May 2019 8:10PM
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About 4.4'!!





PatK
27 posts
31 May 2019 7:31PM
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Looks like the foil mast could be longer than the board

WhiteofHeart
123 posts
31 May 2019 9:56PM
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Bender said..
Thanks for the help. I used a free level app on my phone. With two washers the stab angle is 2.5deg now. Looking forward to testing it out tomorrow
I will leave all the other settings as is and see what difference it has made. Once again thanks for the advice
I'm still very new to foiling. Cheers Bender


Wondering how it turned out?

Currently in the process of tuning / creating a stab for F-One to suit non-foilboards (shift the power further forward), quite the hassle to be honest. loads of parameters.

segler
95 posts
31 May 2019 10:46PM
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Bruce Peterson (Sailworks) and I measured stab angles for several production windfoils. 2 to 3 degrees down angle is typical. Some foils (LP and NP and others) actually let you adjust this. When all is said and done, it is still 2 to 3 degrees down angle that works.

The stab, by pushing DOWN, functions to lift the board and rig in front of the front wing, which acts as a big fulcrum.



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"Distance from Foil to Mast foot" started by tbwonder