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Effect of foil mast length on planing, leverage, etc.

 
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d0uglass



Joined: 28 May 2004
Posts: 1248
Location: Bonita Springs, Florida

PostPosted: Sat Mar 23, 2019 9:57 pm    Post subject: Effect of foil mast length on planing, leverage, etc. Reply with quote

I got a foil as an early 40th birthday present. It's a 2019 Slingshot Fwind. I intend to use it on my 2004-ish Exocet formula board. (I've reinforced the deck over the finbox to hopefully avoid the finbox ripping out prematurely). The package came with a 61 cm mast, but I also bought a 90 cm mast for it.

What exactly does a longer mast help with? Just with avoiding breaching the foil or touching down inadvertently in choppy water? Or does it also help with early planing and leverage for standing in an outboard position, like a long conventional fin on a formula board does?

I'll probably try the foil for the first time tomorrow with the 61 cm mast.

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kmf



Joined: 02 Apr 2001
Posts: 493

PostPosted: Sun Mar 24, 2019 9:47 am    Post subject: Reply with quote

Jim, was checking out your sailsize calculator and I canít enter my weight in to the excell box. I am using an I-pad. Any reason for this?

Kmf
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boardsurfr



Joined: 23 Aug 2001
Posts: 1209

PostPosted: Sun Mar 24, 2019 10:02 am    Post subject: Reply with quote

Good question, let me know what you find out Smile. I think shorter masts are good for the first steps, since you can start and sail in shallower water, and the crashes when breaching (or suddenly going down) are not as dramatic. Once you get the hang of it, the longer masts give you more room for lateral movement. If you watch videos, you can see even good guys using most of the length of the mast in a run - sometimes just above the water, sometimes close to breaching.

If you start racing on foils, other factors may come into play. Good racers often have everything tilted windwards, and a longer mast works better for that. I remember hearing that some guys even go to narrower boards to allow higher tilt angles without having to worry about the windward rail touching. Not sure how much there is too this, though.
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DanWeiss



Joined: 24 Jun 2008
Posts: 2276
Location: Connecticut, USA

PostPosted: Sun Mar 24, 2019 4:20 pm    Post subject: Reply with quote

A longer mast allows greater leverage over the foil since it increases the distance between the wings and your feet. A longer mast also allows the board to fly clear of larger chop than it could do with a shorter mast.

That's all I know.

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dcharlton



Joined: 24 Apr 2002
Posts: 370

PostPosted: Tue Mar 26, 2019 4:33 pm    Post subject: Reply with quote

Longer masts is actually easier once you get over the fear of heights. I don't feel I lose any control with the long masts and I'm not constantly breaching in steep chop.
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wsatl



Joined: 30 Sep 2014
Posts: 17

PostPosted: Tue Mar 26, 2019 5:22 pm    Post subject: Re: Effect of foil mast length on planing, leverage, etc. Reply with quote

d0uglass wrote:
I got a foil as an early 40th birthday present. It's a 2019 Slingshot Fwind. I intend to use it on my 2004-ish Exocet formula board. (I've reinforced the deck over the finbox to hopefully avoid the finbox ripping out prematurely). The package came with a 61 cm mast, but I also bought a 90 cm mast for it.

What exactly does a longer mast help with? Just with avoiding breaching the foil or touching down inadvertently in choppy water? Or does it also help with early planing and leverage for standing in an outboard position, like a long conventional fin on a formula board does?

I'll probably try the foil for the first time tomorrow with the 61 cm mast.


This is the classic learning progression. Your first few times on a foil and you think, "Who's the sadist that made the mast this high?"
Fast forward a few weeks or months and either get hit by a gust or go across some chop, etc. and really extend the foil out of the water, you're thinking, "Oh... now I get it."

I temporarily went to a 75 cm mast from my 90cm main axe and foiled out several times in the first ten minutes. Was not fun and had to adjust my style to keep the wing in the water. You'll get used the longer mast. Short masts are handy in shallow locations (e.g OBX, FL) but in chop, swell, etc you learn to love having that 80+cm margin between your wing and the surface of the water.

Longer masts do go upwind a bit better, too, of course - especially if your board is wide enough (like yours) to be able to control that much power.
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d0uglass



Joined: 28 May 2004
Posts: 1248
Location: Bonita Springs, Florida

PostPosted: Wed Mar 27, 2019 11:28 am    Post subject: Reply with quote

Maiden voyage went pretty well. Did a lot of flying and crashes were not bad enough to break equipment or cause injury. Plenty of power to fly with a 5.5 sail in 15-17 kts wind. Felt overpowered and had to sail sheeted out a lot, actually, and struggled to keep from overfoiling. Did a lot of inadvertent porpoising up and down from overfoiling to touching down. Choppy, wavy water added to challenge of not overfoiling or touching down. I had to keep my back foot quite far forward and on the centerline of the board to keep the nose down and not round upwind. I put the back foot in the chicken strap sometimes but it seemed like it would be impossible to get the back foot in the outboard footstrap without instantly overfoiling and rounding upwind. I have the wing in the most extreme forward position now and I think I might move it back to the middle position to reduce the amount of front foot pressure I need to keep the nose down. I'm also eager to try it in lighter wind with smoother water.


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coachg



Joined: 10 Sep 2000
Posts: 2767

PostPosted: Wed Mar 27, 2019 12:13 pm    Post subject: Reply with quote

A 5.5 is a way bigger sail then I would use in 15-17 knts with a foil. Try a smaller sail in that wind to see if you can gain more control. At 170 lbs I would use a 4.2 sail in that wind.

Coachg
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NOVAAN



Joined: 28 Sep 1994
Posts: 1211

PostPosted: Wed Mar 27, 2019 1:31 pm    Post subject: Reply with quote

At 165lbs and a mid size wing I would be on a 4.7. That said, when you get more time on the water, Your lite wind range and top end range will increase for a given sail size. I like to rig for the gusts because it takes so little sail power to keep flying once your up.. have fun in your quest to foil...Keep us posted
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grantmac017



Joined: 04 Aug 2016
Posts: 817

PostPosted: Wed Mar 27, 2019 3:25 pm    Post subject: Reply with quote

Possibly shift the mast base a bit forward. I find larger sails need it back, smaller forward.
Your back for is forward and inboard because of how far out a formula board puts the front one. A set of inboard mounts could help. With sails under 5m I can run front straps only 15cm apart if I wanted. When I was using a formula board I just placed my front foot on the deck with the outside against the inboard part of the strap. I'm not convinced foiling really needs straps unless jumping or controlling big sails for max VMG.
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