Hi Bob, these aren’t my designs, they are the state of the art foils used on sups.
Interesting that they use a twin foil design that’s good at low speed lift that translates to very sensitive to ride at higher speeds.
I think we went through the ‘speed’ discussion here a few times where low speeds at takeoff are very short periods of time and areas of marginal lift way out on the shoulder but if you’re close to the breaking wave there’s tons of lift from within the wave itself.
As for a comparison I think the foil itself tells the story.
There’s are very technical hi lift thick foils with a wide range of AOA thru the rounded leading edge and comber under the foil that perform fully submerged. They’re riding the lift from the foil.
Mine are flat, under 1/4 in. Im riding the lift from inside the wave.
Is anyone getting barrelled on a foil yet?
I can do that any day.
This is a pic from 4 years ago when there was a barrelling shore break and I took 30 tubes one after the other and made it out of all of them.
There’s more videos on Vimeo of just wave after wave pulling in but due to the splash it’s obvious what’s happening but not Hollywood quality.
Brett,
Is that hum/whine I hear in the video of the commercial HF from the foil?
BTW have you had a chance to test the last uni-body HF shape we were discussing?
If so, how did the testing go? PM if you need to…
Yes it’s hum from the mast.
Just about to step out the door with the latest foil…
Great stuff!
But I was thinking about standing-up foil surfing barrels. Is that happening yet?
Oh sure MrMik, with the same foil as on the prone board, same mast system, but I put it on a stubby thick shortboard.
The mast is under a foot so it’s a more intimate feel more like surfing and the rail does come into play on cutbacks.
You can see it’s riding in the same place as a surfboard rather than out on the shoulder.
The foils stays submerged at slow speeds and then pierces the surfaces as the wave hollows out.
Is the flexing in the keel a planned feature?
Too much flex of the mast or foil does return a variable lift.
But it’s not essential for the mast to be completely rigid, so much like a board with flex, a mast/foil with flex is still completely functional.
The foil isn’t hard to design, the board can be any surfboard, But it’s the connection between the two that’s the conundrum.
If you use a single mast then it has to solely support all the forces between Foil and board and it will need to be very strong, most likely a custom build and connecting it into the board will require a sizeable connection that’s most likely customised and complex too like the Tuttle boxes that SUP foils have.
So if you consider using two masts , you’ve split the forces but more than doubled the submerged area.
Try 3 or 4 masts and now the forces are reduced on each mast so you could use but you’ve got up to 8 connections between board and mast and foil as well as a lot of weight and surface area.
Whenever I see the words ‘deep tuttle’ I like to hum the first few bars of ‘Smoke on the Water’ from Deep Purple, just for fun.
Lift quadruples when speed doubles. In trim, velocity is max. Foils, especially the standard commercial HFs, will generate too much lift and breach with too much speed.
Then they lose lift and slow.
This increased speed and lift sequence makes it tough to maintain trim speed across the face of the wave.
Foilers have to control (slow) their speed by riding perpendicular to the wave face, moving out in front of the wave and then cutting back in.
Maybe controllable or automatic flaps to reduce lift or turn the foil down when the ‘surface effect’ starts to influence the foil?
I do have some concepts in mind for responsive foils, you could do some really cool things with that line of thought. Unfortunately I’m pretty sure the surface effect that you mention is caused by getting compressible (but more importantly expandable) air into the flow.
If you have a foil who’s lift is achieved the same way an airplane does through naca type surfaces, that air results in a drastic loss of lift, so changing a surface wont have much effect.
if you have a foil who’s lift is determined by attack angle it minimizes that drama and allows for a foil that operates similarly on the surface and under it.
On most of my foils I never experienced that “dropping out” feeling but my latest design relies on flow of un-compressible fluid over the top for pitch stability.
Ironically it was that feeling of dropping out when I got too close to the surface during my test rides that made me realize that my design actually worked.
so now I just bought a 24 inch slingshot mast and base so I can do a little more boat testing.
Dave,
I assume boat testing means you are being towed by a boat.
Are you using any special type of tow rig or harness?
Top end test speed?
PM if needed.
You’ve mentioned before that the connection of the mast will work on any board (when it comes to your system) so I’m guessing you are not using tuttle boxes?
Hi Bill,
Yes were were being pulled behind a boat. No special rigging, in fact we were using a homemade ski rope to pull a homemade foil behind a (very cool) home made boat, very Swaylockian I think.
We were going about 20 miles an hour or less.
I posted a video on you tube but it’s really for my friend who owns the boat.
I didn’t spend much time trying to edit it so for It’s really long and not very interesting from a analytical standpoint.
I was using a go pro clamped to the windshield so I had to really use the digital zoom to see anything.
it is on my you tube channel (same as the earlier video) if you’re interested but as I said not a great video.
To an uneducated observer the test might look like a failure, and maybe that’s a good thing.
Monkster1, because all this foil experimentation started years ago before you could buy foils, everything was completely hand made and I set a standard that if I didn’t have it already in the shaping shed then I wouldn’t buy it. I’d make it or modify what I already had but I’m not spending a cent. So it should be doable for any Swaylocker to build their own foil and board combo without buying anything new or using any high tech equipment.
Jrandy, for me it’s Deep Water by Richard Clapton. https://m.youtube.com/watch?v=2lQb7rnuqu4
You can see the effects of a breaching foil pretty well in your tow video Dave.
Looks like you are holding the tow rope under the board.
The video does show some things and being able to use slow motion helps, but I could see pretty well from the back of the boat some of the things that can’t be seen on the vid. I could see for instance that it took several seconds after the foil was re-submerged before the air that followed it back down after a breach cleared up. the amount of water being thrown out when the foil was on the surface was also telling and on future models I will probably increase the radius across the leading edge
We tried holding the rope different ways, it seemed the by holding the rope on top of the board it prevented us from getting the nose up.
eventually I was just holding the rope out to the left in one hand and using my other hand to steer the front of the board.
I just came across this website again it is the website of the hydrofoil society looks like hours and hours of reading enjoyment ,thought I’d post or re-post it if it’s already been done here
http://www.foils.org/
I have been making these for mounting points into boards, They are all cnc machined from high density P.E.T foam to take two futures long board boxes with the 90mm offset that most kite and sup foils have. Most people are going over to this type of flate plate mount as it means you can make adjustments a lot easier to the position and angle of the foil relative to the board. If anyone wants one drop me a message I have already posted quite a few to people in the usa.
