Dual Spiral Hoop paipo fin concept...

I’m curious if anybody has any input on this one.

I was having a hard time trying to draw this so I freehanded the outline on paper for better visual. Bonzer-like concaves run under the hoops. For the record, photos have been sent to Roy Stewart and Dale Solomonson for their input.

The final assembly will probably be quite different from this, my first attempt at a paper prototype…

Looks like a fairly good kelp catcher…but not optimal.

I may be wrong, but that seems to me like some real original thinking…

Way to go John…

looks like a concept that is being done in sailing. realy wiggy hydrofoils for very fast one person sailing skiffs like the “international canoue”(spelling).

goforit!!! it will pick up the tail and haul unholy ass from the looks of it!

“dont bother thinking outside the box…foget the damn box just think!”


just out of curiosity – why on a paipo? A lot of them don’t even HAVE fins, right?

Keith -

Please check this video and then ask me again.


Gorgeous, John, absolutely gorgeous.

Setting it up so the bases of the hoops/spirals are placed like the normal fins of a quad is genius. It just seems intuitively like it would be effective.

Mind if I make some too? :wink:

And any chance you have a link to that hydroplane paipo in action?

I bet ol’Roy would have something to say about that…hate to see that one… what next? a Blacks beach strapless nudie cel phone/latte cup holder for your hydro trubo foiled yuppy GPS speedo 4’-3" pimpsled?. “reminds me of a dream I had”. it can’t bee… so there’s a vid of that dude with a highly advanced surf contraption in a parking lot… so’Ya no video of him speeding in the water then? . I like creative thinking… it just might work.

Think outside of the semi-circle…pull the rail side of the hoop outward so it more closely approximates the outward cant of a bonzer fin.


Keith -

Please check this video and then ask me again.


so wheres video of him riding it?!

Still photos and written explanation only…


Hi John,

I think you will have to be pretty careful when installing the setup. With the amount of horizontal surface of the hoops, if one side is slightly lifting and the other side is pulling down, then you’ll have an interesting ride to say the least.

So I guess the alignment is critical, maybe you should include some way to allow you a fair amount of adjustment into the system.

As said previously, great idea with the quad style box placement.

Kind Regards,


My instant dyslexic reaction is to switch sides i.e. the forward increment of the spirals oriented in the center may be looser and more directional than the pictured set up which appears to be a fine stablizing feature but perhaps less than Axial,[centered],in its center of latteral effort…perhaps necessary to offset the length to width ratio of the body vehicle format …ambrose …third row in the peanut gallery…oooohhhh when they left the second side of the spiral fin un attatched the resulting audial modulation attracted species of fish unseen for thousands of years and the harmony struck the world head on and reversed all the problems plaguing man for the previous ten thousand years and all came right…except when the left was better.

Interesting, John, quite interesting indeed.

Some questions and thoughts:

Are you thinking in terms of molding this over a semi-circular male form? Or making a flexy flat outline and then bending it to shape as you attach it? The first is probably the easy shot, but the second has some interesting possibilities, though you’d have to make 'em thin enough that some sort of soft leading edge would be a nice safety consideration. Thin section would cut down on the parasitic drag of 'em considerably as well.

I might fiddle with it so that the more horizontal parts of 'em are paralell to the bottom curvature at the center of weight - say a little forward of the attachment points on a a paipo. Other option is play with your body position on the thing so that the center of your torso is pretty much over the fins. As seen in Terry’s hydrofoil paipo, the lifting surface is under the center of weight while the guidance surface is as far forward as possible so that the size of the foil ( and thus the drag of it) can be minimised.

Might it be better with the trailing ends to the outside? Like ambrose said, directional stability/instability tradeoffs, plus I might go with a much smaller overall area, as what’s currently there might be so much that it’d affect how well it turns in an adverse manner. Easiest way to tackle that question might be to run the shapes through a drafting program that’ll calculate surface areas of irregular forms.

Here’s a goofy thought for ya - make the fins with fcs-type tabs in 'em, so you can experiment with overall lengths, angles of attack and so on. Or the shallowest fins unlimited/bahne box setups you can make, which might allow a little twist to be intentionally incorporated in the fins for a Kort nozzle kind of effect, redirecting water flow in several different ways. ‘tuning’ the flex and twist/angles of attack might get you some very interesting turning behavior under loads, such that a small increments of change in a particular range might produce very different behaviors.

Anywho, that’s my initial thoughts. Be interested to see what it does.


Looks cool. If you siamese the hoops at the center, you could reduce the wetted surface substantially. Think of an “m” shape instead of two seperated hoops - “n n”.


My crappy mockup.

This would probably be easier to make, as there is no twist in the system. You could use a piece of plastic pipe of the appropriate diameter, cut properly, as a bridge between two bonzer runners, then just flat sections for the fins. I might have to try this one! Seems like it would increase hold at least, and maybe thrust too.


……a Blacks beach strapless nudie cel phone/latte cup holder for your hydro trubo foiled yuppy GPS speedo 4’-3" pimpsled?..…

Will have to contact you to write the promotional brochure!

But just to clarify things, this board is a research and developmental prototype. As such, a certain degree of instrumentation is contemplated to compare theory with practice, and the performance of this board vs other types of surf vehicles.

Presently the instrumentation is limited to a GPS to measure and log speed “over the bottom”, and a Speed Mate knotmeter to show the instantaneous speed “through the water” (which can differ substantially from the speed over the bottom). They both also capture the max speed through the water speed since last reset.

However additional instrumentation is being considered to monitor the state of the hull and foils relative to the sea surface, and simultaneously document the motion and location of the craft on the face of the wave. Obviously a craft intended for recreational surfing would not need, nor have any of this gadgetry.

OK John.

Watched the video.

Read the brochure.

Still wondering…

why on a paipo?

(why a duck? why not a chicken? (Marx Bros…)

Keith -

  1. Because they're really fun and probably more forgiving when experimenting with a totally new fin design.
  2. When you ride on your belly, as any mat or bodyboarder can tell you, your face is close to the water and it seems like you're going that much faster.
  3. You can get tubed like nobody's business on one.
  4. It's a good way to make use of broken boards.
  5. If the fin design doesn't work, you can drag a swim fin in the water and still keep control.
  6. If it does work, you can arch your back, lift your legs and feel what the board and fins are actually doing on their own.
  7. If you fall, you don't fall as far.
  8. Showing up at the beach with something no one has seen before is kind of fun.
  9. Hopefully, it gets people on this site brainstorming away from retro 30-40 year old recycled ideas that have come and gone and are back again.
  10. If anything new is gonna happen in the way of design, somebody has to take a chance.
  11. Why not?

that guy on steve allen…porque?..porque no… and louie Nye said too WHYYY NOT? I still love those guys as much as the thought of that design quest slipping into the water…ambrose…anticipation is intoxicating