Which “boat” foil shape would that be?
Nice foiling video. Check out the long sweeping turns.
At 1.42 you can see the two piece foil design he’s riding.
http://www.networka.com/videos/28427/drone-films-laird-hamilton-riding-foil-board-in-hawaii
Hes doing what I know is the best way to ride foils…you get speed when you drop but the ‘lift’ comes when you stick high on the shoulder.
And another video where you can see the extra wing sweep in the front foil. At .46 to 51 seconds.
https://m.youtube.com/watch?v=9g4GhW7kxhc
double post, sorry.
**stoneburner wrote:**
**peacluvmungbean wrote:**Why are these foils shaped as they are. I don’t see why wave foils are different to the established laws of hydrofoil boat design over the past 100 years.
Which “boat” foil shape would that be?
Stoneburner, I can see what Mungbeans is on about, hydrofoils are traditionally long lateral blades, foiled and very technical, but Dave and I are using shapes that are nothing like that, but its all because of lift. Traditional Hydrofoils on boats create lift but on surfcraft you dont need lift because the wave gives out more lift than youll ever need, theres no need to create lift on a wave… but it is all about controlling the lift.
Thats why Dave foils are getting smaller as he rides bigger waves and my foils as well have come down from ~300 sq inches to ~120 sq inches. Technically as speed doubles the lift from a hydrofoil quadrouples so a foil that lifts a 70 kg rider at walking pace can lift a 240 kg rider at jogging pace. And then lift a 960 kg rider at running speed, so you see that lift isnt a problem but regulating lift so that its under control is the key. And finding the right shape and number of foils is tricky, not enough area and youre not going anywhere, too much and its like a wild bronco leaping out of the water. Ive had that once early on and its not fun !
Having control over the foil includes all the components, the strut is the vertical piece between the board and the foil can be too long because it makes the foil slow to react and draws wide lazy arcs out on the face. A long strut also means your vertical lift can be quite dramatic under acceleration, you dont want to be flying up and down 3 feet in the air so a shorter strut make a smooth transition between being in the water to flying above it. Both Dave and I are using struts around 12 inches, long enough to be clear of the surface chop but not too long to be awkward.
The foils themselves are the stars and control how you’ll ride. Much like a surfboard, wide foils are stable from side to side and longer foils are more stable nose to tail. Its not a lot more scientific than that but its about testing what dimensions suit you and the waves you ride and keeping a stable overall area so you have a consistent lift, if you stretch the length of the foil you need to bring the sides in and in my case Ive split the foils into 2 arms or side rails so they sink into steep waves. Ive found that flat 3mm Aluminium or laminated ply with tapered leading and trailing edges works perfectly, the minimalist volume keeps the weight down and creates very little form drag and so simple to build.
The leading edge is a good indicator of the foils performance, a wide foil with a straight leading edge ( Green shape) lifts quickly but also drops quickly and in a surf environment the power and direction of the water isnt always consistent enough to use a straight foil.
The rounded foil (Blue) has a smoother lift, good stability but loses power due to its shorter length.
The Orange shape provides gentle lift but is slow to react to turns.
The Red shape with a width of about 13 inches has predictable lift and lots of drive due to its length.
Getting a great foil is a matter of blending the best parts of each shape.
I think this statement alone identifies a key issue for “Paddle-In” hydrofoil surfboard performance.
Good read Brett. You make some good points. However just reading your comments it seems fairly obvious that foil shape and performance are multivariate. I will go out on a limb and say surfboard performace is a bit different than boat performance.
I have seen a wide range of foil designs for power boats, sail boats, sail boards and human-powered hydrofoils.
With several million years of evolution, it seems that cetacean pectoral fin shape alone should have a leg up on a century of human dabbling with hydrofoils.
Bill, Ive split the foil into two side rails to hold in steep waves but it also reduces the lifting area by half too. The steeper the wave the greater the excess lift that needs to be avoided, a while ago I put fat side rails on an earlier foil and it just leaps out of the water like a porpoise when the waves get steep.
The other idea that’s worked well is to split the lifting area not only into sides but also levels. On this yellow foil there’s a central area that adds to the low speed lift but rises out of the water as speed. That’s gives a foil that lifts very easily at low speed but automatically handles high speed foiling too. So as you drop into every wave, you’re already flying, the foil automatically adjusts to the wave speed to give you the right area to maintain control and at the end of each wave you’ve often got enough speed to connect with the wave behind. This one has a maximum of 277 sq inches and cuts down to 59 on each side foil.
New set of rear foils…
lve been working on a single foil but its clear I need to separate the lifting area into a front and rear setup so the distance between them can be adjusted to make the foils turn like a shortboard or a longboard.
This is exciting innovation at it’s finest. This is exciting innovation at it’s finest. This is exciting innovation at it’s finest!
Not to take anything from any of the people mentioned so far. All are doing exciting stuff.
There’s a historical guy that wasn’t mentioned… Roger Wayland, the down and dirty inventor who could slam something together and have it in the water the very same day. He used to be featured pretty regularly on Nels Norene’s ‘Vagabondsurf.com.’ Nothing very pretty but he could fab out a ‘concept vehicle’ in nothing flat.
http://vagabondsurf.com/WaylandRevisited.htmlhttp://vagabondsurf.com/WaylandRevisited.html Look around once the site opens… there are other Wayland files in there.
Wayland is among the creators for sure John.
I see some interesting evolutionary branching and progression with Dave and Brett here at Sways …
hi brett !
I’m curious as to how you arrived at your foil shapes , ie: why they are the shape they are …
[ big parts being obviously , experimentation , refinement , testing … but … anything else ? ]
cheers
ben
If you can also adjust decalage (shims on front/rear foil to adjust the angle), that will make for a more stable vs ‘squirrelier’ pitch stability. Having multiple locations to affix the front foil to can make the board have an adjustable turning radius. Combine that with the decalage adjustment shims, and you have a board that can ‘ride’ very differently and can be tuned to conditions.
JSS
Thanks for the link John,
I figured there had to be others out there that have tried something like this.
Does anyone know if he still fools around with surfcraft?
That triple tube paipo reminds me of Darth Vader.
I’ve been busy working on the mold for my new foil, I can only post small pics at this point but here are some…
It will be sistered up with my first mold and enable the fabrication of two different width foils with an overall length of 35".
I’d also been kicking around the Idea of a using a low volume tratitional paipo style board with my foil.
I like the idea of the board cutting through the water almost as easily as the foil and staying low in the water for takeoff…
I had started fabricating it using a skimboard mold for the rocker
But the boards shifted during glue up complicating things a bit.
I could still make it work. and probably will at a later time, but its on the backburner for now…
not just because of the shifted board but because we had a community garage sale this weekend.
as I was walking around I found a board that fits what I had in my head better than the skimboard shape…
IT’S A WAKEBOARD!!
It has tons of rocker which runs the entire length of the board …
It has a lot of other design features that are desireable also ( not to mention the cool graphics)…
I’m interested to see what effect the fins on the back of the board have if any.
the removal of the front fins allow me to put handles on the front which I’ve wanted to do for a while…
I put it in the pool yesterday .
It has already passed a critical test,IT FLOATS… but not by much.
It also is fairly easy to paddle…
It remains to be seen whether or not I can catch a wave with it…
but if so I will likely attach some sort of foam onto the deck for padding and a little more bouyancy.
It also might need a little reinforcing down the length…
I could have spent a few weekends building a custom board and never come close to this…
And to top it off I didn’t even spend all of my yard sale profits to get it…
Hi Dave, that update is freakin amazing !! How cool to use a wakeboard !
Keep on with the updates, how did the surfcraft weekend go ?
Dave, I liked your idea so much I went and got a kiteboard.
144 X 44, 1.5 in rocker at each end, as well as two big ass foot pads.
I’ll keep two fins at the tail for paddling stability but strip the rest off.
Certainly it will mimic the low drag foil.
I took it for a quick surf without a foil on and it’s very flexible and I’m thinking it will need some longitudinal support or it will bend down at the nose and tail when the foil lifts it up.
i thought of using a single central beam to add strength, glassing all sorts of things in place but I’m going to bolt two lengths of Aluminium T extrusion to the deck and then add EVA foam over the top. One central beam wouldn’t moderate torsion of the board as well as two sides pieces.
Feet go here and the brown tape is where the Aluminium will go…
and the last pic is where the foil will go, equidistant between both feet.
Did you catch any waves ?
other than being too flexible how, did it go? I haven’t gottent the chance to get mine in the water yet, I’m hoping that the wakeboard is a little stiffer than the kiteboard.
It’s pretty flexy too but it has to be stiffer than a boogieboard I would think…
Hi Dave, it was a great sunny day and there were small waves about 1-2 foot face, not anything to get excited about but perfect for trying a new craft. I took dozens of them but its just too easy to slide in on a small one, pop up onto my feet and trim along. The general feeling us that it’s too flexy for real waves, when I stand up it bends up and down at the front and back of the board, it’s just not going to be strong enough to hold me when the foil lifts. I think its forgotten that when the foil lifts , the complete weight of the rider is balanced over each side of the plate that’s attached under the board, and the board needs to be really rigid to survive.
Here’s a pic of the 2 Aluminium T pieces bolted in place. Need to top it with foam and I’m in the surf.
This is great watching the both of you bouncing ideas off each other. i can’t wait to see what you come up with next. Dave, I was so impressed w/ Josh’s hawaiian paipo that I have ordered one for me. It is an amazingly efficient hydrodynamic design. It has a convex deck and bottom and a tapered nose which allows it to drop in and go on a wave quite easily. It might be a possiblity for your foil since the full length convexes could add to the longitudinal stiffness. Maybe take that and shape in foam w/ carbonfiber would give you a fast planing platform w/ the stiffness you want. I am getting it in 6-8 weeks. You can try it if you want.
what length and width is that , brett ?
how easy [?] to paddle into waves ?
were you standing up ?
I reckon Alex or Marshy [manly local] need to ride it next , with the foil attached , while you film its performance [ P L E A S E ? ? ? ]
cheers !
ben
Surfsensei, I’m just stoked that you rode Daves Wavewing and that you liked it, there must be a surfing museum where Daves foils would be a great exhibit, especially as a example of surfcraft development.
Ben, its a 144 X 44 cm kiteboard, about 2 cms thick at best.
I will get some close up go pro footage to check how the foil flexes and sits in the wave and then I will get some beach footage of it being ridden. Do you remember that Al said he thought the foil wasn’t long wasn’t long enough from front to back ? So Ive extended the length out from 23 to 32 inches.
It’s got very low bouyancy so I shoulder hopped and dropped in at the last second. It’s almost flat rocker until you stand up and then you sink in the middle and the ends bend up. That’s why I put in the Aluminium strengtheners. I tested the board by putting a brick under it and standing on the board and it’s not flexing so that was an easy solution.
I found some EVA so Ive started building up the deck…
