Kai Lenny Downwind SUP Foil

[surfcowboy]

Area 10, the main thing for me would be making a horrible windy day of surfing into a much smoother experience. Not going to do this 100% of the time but it's an option and the feeling of flight must be amazing.

[Dwight (DW)]

The foil that I ordered back in April has finally arrived and I'm ready to get it flying...in and out fog today making the wind go up and down...instead of our normnal steady thermal seabreeze...

Awesome!

Looks like you got the XLW wing, is that correct?

Happy you didn't get the CR wing. I got that one for the wife. Takes too much wind. Getting the LW wing to replace it.

Our experience with the CR wing taught us one thing, kite sized foils don't work for windsurfers. The CR wing is rated to lift at 8 knots for kite use, and 18 knots for windsurf use. I thought it might be about right for a 120 lb windsurfer. I was wrong, it takes about 14 knots for my wife.

I'm excited to see how your SUP foiling goes. I'm not going to invest in any testing. I'll wait on you 

[SUP Sports ®]

Aloha DW...
Yes, XLW wing...I think Phil has proven that his foil works for what I want to accomplish with it...but, I'm certain the foil designs will evolve...
I'd like to solve the weed collection issue...having to stop and clear the foil is a PITA...

I'm approaching the foil as a light wind tool to use a local thermal breeze resource...so, 14 knots (16mph) to fly for a 120# sailor wouldn't work for me...16 mph average usually means gusts over 20 mph, and I'm planing on my regular windsurf gear in that kind of wind...more than enough for windSUP...or, light air wavesailing if there are waves...

I have a couple of friends making kite foils...and, I've seen them on the water...and, came to the same conclusion as you...

I have some ideas...a foil with fore and aft adjustment would be cool...so, would retractability...
I am working on a windSUP foil...expensive R&D for sure...
I also got an impact vest for the crashes...I seriously bruised my rib cage learning to loop...thanks for the tip......;-)

[PonoBill]

Will it downwind?    Sure whips a tight turn.

http://www.homedepot.com/p/Parrot-Hydrofoil-Newz-Drone-PF723401/206783336?cm_mmc=ola|criteo|27E-27-8-7|22037|https://us.yahoo.com/?p=us

Similar to the design I'm working on. I'm doing the math before I get serious on shaping. I plan on L-shaped front foils, retractable and adjustable. T tip on the tail, and probably that will pivot as a rudder. I've got an old Starboard Coast Runner that will be the test mule.

[PonoBill]

Your ass would be better served on a different project. The existing foils are fine. The French make the best foils. Years of design and R&D. Buy one of those and slap it on a board and go. Learning to foil will be a project in itself.

I'm sure it is, given the short fuselage and the lack of pitch stability. Why that would be the proper solution for a craft that already has a long fuselage escapes me. What works well for kites or towing behind boats is almost guaranteed to be less than optimal for SUP downwind boards. I've run some numbers from measuring existing kite foils. The design doesn't make sense. The pitch stability is terrible and increasing wing area to reduce liftoff speed makes it worse unless the fuselage gets longer.  I can't see wasting my time with a limited design that I doubt I'd gain performance from.

There's also a reason why foilers using current foils are locked into a vertical stance. With the high roll center of a hydrofoil, the stability added from dihedral or anhedral wings  reaches a sudden tipping point where stability goes negative, The narrower the foil, the sooner that point is reached. Trying to mitigate that by making the wings longer and higher aspect drastically increases pitch sensitivity. These are fundamental limnits of the kite foil design that don't get eliminated by experience and R&D.

[cnski]

I agree that kitefoils, especially high performane ones, will not be great for SUP foiling. A windsurfing foil like DW and SUPsports have will work much better. Increasing fuselage length definately helps with pitch stability but at the expense of increased drag and speed. And not all short fuselage foils have terrible pitch stability. I'm sure Spotz, Horue, Taaroa etc will eventually come out with a downwind SUP foil. It will be intersting see what they come up with. The best foil is the foil you can get today so you can start learning tomorrow.

[Beasho]

I'll chime in on Speed, which is highly relevant.

Unlike KITE foiling there is a maximum speed to Down-winding and SUP Surfing.  My kiter friends suggest regular speeds in excess of 30 mph necessitate a high speed foil.   

From all my Trace GPS measurements the fastest speed ever recorded SUP Surfing was 33 mph.  And I could tell it was fast.

A slow speed on a caught wave is 18 mph, maybe even as low as 12 mph for a really short period crappy little wave.  Waves in the 10 - 15 ft range will get you going between 22 and 28 mph. 

The only way to hit 30 mph is on an 18+ foot wave.  Think monster, fast long period swell.  Even at Mavericks I recorded just 30 and 31 mph. 

This is a big insight when it comes to foil designs because We SUP'ers are operating in a relatively LOW SPEED ENVIRONMENT.    aka fatter, higher lift foils vs. high aspect , small twitchy high speed foils.

[blueplanetsurf]

Will it downwind?    Sure whips a tight turn.

http://www.homedepot.com/p/Parrot-Hydrofoil-Newz-Drone-PF723401/206783336?cm_mmc=ola|criteo|27E-27-8-7|22037|https://us.yahoo.com/?p=us

Similar to the design I'm working on. I'm doing the math before I get serious on shaping. I plan on L-shaped front foils, retractable and adjustable. T tip on the tail, and probably that will pivot as a rudder. I've got an old Starboard Coast Runner that will be the test mule.

It's been done, I found this photo of Karen Baxter (Connor's mom) in around 1982
 

[blueplanetsurf]

We have been using a modified kite foil to learn how to foil behind a jet ski, once you stop crashing and start flying, it is an amazing feeling, addictive for sure, here is our report and video:
http://blueplanetsurf.com/blogs/news/118470981-learning-to-fly-on-a-foilboard-while-we-are-waiting-for-the-stand-up-paddle-foils

[PonoBill]

A little history here. Kite foils look the way they do today not because it's the best design, but because design is rarely creative. The foils used now are direct decendents of sit-down foils invented in 1984. The foils look like they do because the rider;s butt was supposed to be right above the attachment point, keeping the center of gravity low. When guys like Laird wanted to play with tow-in foiling, they bought an "Air-chair" and unbolted the wing from it.

When you start from an inappropriate, but but operable design the first thing you do is to tune the stuff that's easy to adjust to make it work better. Most people won't toss the whole thing away and start from first principles, they'll tweak what they have. And over time it gets pretty good, and becomes hard to compete with because A. It sort of works, and B. We already have it.  That's why our cars are powered by pistons, moving up and down in cylinders, with lots of friction and waste heat, sucking gas in through poppet valves with ineffcient mixing and design tradeoffs in cam timing, transferring power to a crankshaft through connecting rods, to make a flywheel and transmission rotate. If you started with a blank sheet of paper and the engineering sense of a twelve year old, you'd never design something like that.

The foil for tow-in foils, and therefore windsurfer foils, and therefore kite foils, and therefore SUP foils are designed from what we got, which was designed to sit on and be dreagged around by a ski boat.

So of COURSE it doesn't really work for shit.

[cnski]

Small twitchy high speed foils get alot more stable at speed. And with practice. Speed will always be a factor even in SUPfoiling. Big waves will be faster than downwinding I would imagine and you also want a foil that will be stable and turn well. I don't design foils and don't really give it too much thought. I just ride them. Pono- It sounds like you have a new idea for for a totally different foil design? I say go for it. But what are you gonna ride until then? You can't see wasting time on a limited design that you doubt you'd see performance from? I say don't waste any time at all and get a foil and start foiling soon. Or build your idea quick. Summer will be over before you know it. Not foiling at all is worse than a low performance foil.

[PonoBill]

The engine will be done next week, car back together a week after. I think what I have in mind is pretty simple to do as a test. It's nothing new, in fact it's how foils are always done when you have a hull instead of a chair. Nobody in the rest of the boat world builds a foil like a chair/tow/windsurf/kite foil. I have six or seven books on hydrofoil design, none of them show a design with a single strut connecting to an underwater fuselage. The only reason the fuselage is attached to a single strut is because it was designed to be attached to a seat. Works fine for a kite with a tiny board, makes less sense for a windsurfer and even less sense for a SUP board.

I'm not in that much of a hurry.

[blueplanetsurf]

The engine will be done next week, car back together a week after. I think what I have in mind is pretty simple to do as a test. It's nothing new, in fact it's how foils are always done when you have a hull instead of a chair. Nobody in the rest of the boat world builds a foil like a chair/tow/windsurf/kite foil. I have six or seven books on hydrofoil design, none of them show a design with a single strut connecting to an underwater fuselage. The only reason the fuselage is attached to a single strut is because it was designed to be attached to a seat. Works fine for a kite with a tiny board, makes less sense for a windsurfer and even less sense for a SUP board.

I'm not in that much of a hurry.

Bill, I'm all for innovation and creative new ways of doing things but I think there are some things to be said for the commonly used single strut foils.
It sounds like your design will be more stable and easier to use but an advantage of a single strut foil is that once you learn to control it you can steer, control lift and pump the foil by shifting body weight.  It sounds like your design will depend on a rudder for steering and possibly for controlling lift.
It's a little like comparing a hang glider that is controlled by shifting body weight to an airplane that is controlled through instruments. 

[PonoBill]

I understand that. I'm after something different. I want to build a downwind board that is consistently faster, catches bumps longer, and that has enough pitch and roll stability to be ridden for distance. I also want to manage the problem of striking things underwater and kelp farming. I'm not looking to just get up on a foil when conditions are perfect. This isn't a moon shot, it's a simple thing to do.

[alap]

Hi DW, long time no see....
couple questions to you, Ill put them in separate posts.

First you mentioned that you changed your sails for the ease of uphaul.
Why didn't you bought a bigger windsurfing board?
The ease of uphaul increases exponentially. I have 3 light air boards, Fanatic Ray 130, Ray 145 and *board Formula

It is so much easier to uphaul 145 than 130... especially in chop... np up to 8.5 sail, very stable
and of course on formula you can uphaul anything anywhere

I understand you dont like big sails and big boards...
but you will be using big board for uphaul only... the moment you foiling and up in the air it doesn't matter what is the size of your board.
Or I am wrong?
 (which is very likely because I never foiled, only reading this thread that will beat the car thread very soon, and may be even hot chicks)?

There are two vid in this thread, one by blueplanet, another by Piros... both guys foiling on kiteboard foil behind the boat.
blueplanet vid shows a lot of trouble and wipeouts, the Piros' solution is fantastic.
He is foiling the same kiteboard essentially, but he uses big paddleboard to get moving.

Like the main advantage of paddleboard behind the boat is that you can start standing up at zero speed, 1, 2, 5, 8 mph... (the second advantage that you need no more than 10... 12 mph, so you can use a smaller boat, and the wipeouts are gentle for old body)
With foil attached underneath one can still use the same advantage (compare with wake like or waterski like start  from the water on blueplanet clip - it yanks you, you are jerked to too much speed in an instant)

Wouldn't it be the same if you use big wide (say ~80 cm  wide) windsurfing board - uphaul, start moving with extreme ease, then pop on the foil, and then forget about the size of your board. Essentially the big board is like a booster to bring you into the air, afterthat who cares how big it was....

I probably missing something...