Retractable Fin System

[Surfdad]

Perusing board designs, I came across this article from back in '03. It describes the basic design of the OLD Placebo Sleigh Model and the New Wave Outlaw, but 4 years ago.

What I found interesting was the patent on a retractable fin system:

http://surfermag.com/magazine/design.../magiccarpets/

One of the issues, like on the Walzer, was when the board is revert the fins would grab the wake. Anyone have any idea how this might be achieved?

[G-MONEY]

Back in the day I had a kneeboard that had a retractable fin system.

[NICKYPOO]

Yes. I can see one possible way, but I'll have to think trough it a bit more before I feel it's actually feasable.

[NICKYPOO]

Back in the day I had a kneeboard that had a retractable fin system.

I've still got two of them. The original Hydroslide Magna and the Obrien Magic. The original Magna had separate fin boxes where you would have to drop one, then the other. On later models and then the Magic, they were linked to a pushrod and a lever at the front of the pad. A lever is not going to work in this situation where the retraction and deployment of the fins needs to be almost instantanious and "smart" as to which fins need to deploy and which fins need to retract given which direction the board is heading. I've just about got it worked out but there is still one question I have. Is this really the answer?

[Tequilasun]

I would think you need some sort of trigger, and a spring to pull the fin back up. The trigger would work a lot like the roof flaps on a race car. When going forward, they lay against the bottom of the board, but when it reverts, the water pressure pushes it open, releasing the spring.

But 1, it would create drag, and 2 would the mechanism re-****?
and C, is it worth it?

[Surfdad]

I want it to be as Nick indicated "smart" so that in one direction the fins are deployed, probably by water pressure as suggested above, but in the other direction, when revert the fins are retracted...possibly by a spring or something that brings the fin back up. My original thought was a fin that would revolve around a front pivot, not unlike the blade of a pocket knife but I would think if it laid down flat rather than "retract" it wouldn't require as much board thickness...visualzie the fins folding in towards the centerline of the board.

Is it the answer, Nick? Who knows, but I'm willing to mess with it. You should see my shop with all the failures. Every once in a while, I get something that works. This board design was one that James and I shaped and was the first EVER surfstyle board that was less than 5 feet in length - now everyone makes them.

Don't ask me about my hollow carbon fiber board project

[NICKYPOO]

Hmm, hadn't though of the folding fin. Interesting. That's going to be a lot more complex. You would need a "switch" that was pressure driven, but that would require such little pressure that it wouldn't creat too much drag yet be strong enough to hold the fin in deploy mode while withstanding the pressures of... No... Jesus, this is way more complex. I'll have to think some more on it.

[Tequilasun]

What if the fins could spin on a vertical pivot point? Would having them spin around be beneficial or not?


Or. You switch could be molded into the board, like a tube that is molded in, that way when the revert happens, and the tail drops below the waterline for an instant, the fins retract. A little nose/tail pump could activate it.

Just thinking out loud

[Surfdad]

Now that's interesting - not "smart" perse, but with a rather EASY to deploy switch that wouldn't require that you use your hand or step on the switch, or MAYBE the switch is pressure sensitive and under your rear foot. When there is weight applied the switch somehow activates the fins, but when there is NO weight applied, the fins retract.

Sheesh - how big would the batteries need to be? I have visions of taking the battery out of the tow vehicle before a wakesurf run "Just let me hook up the Diehard and I'm ready"

[Tequilasun]

Actually what I was thinking of is drilling a hole into the rear of the board, and using a pressure switch inside the hole. So there wouldn't be anything dragging. I know they make pressure switches that respond to puffs of air, so a stream of water through the tube would be similar. Kind of how a boat speedometer works.

Catch my drift?

I don't think we're talking more than a flat camera/watch battery to make something like this work.

[NICKYPOO]

That is pretty outside the box. What you need is a remote that atatches to your vest. A quick tap and the back fins retract and the front fins deploy. Seems aweful involved.

Back to the folding fin. Something occured to me. Why not just use water pressure to make the fins deploy. All four fins (two front, two back) would be full time retract, untill you get the board moving forward. In order for this to work, the fins would need to fold outward instead of inward. No batteries, no swithes, no pushrods. Just spring loaded fin boxes.

OK, this is pretty bad, but hopefully this will illustrate my point.

[Surfdad]

Ok, I like that concept, but when you go to do a surface 3, the fins in the nose will deploy once it hits the wake, won't it? If fact in a hard top or bottom turn they will deploy.

I think it has to be something that the rider has control over - that would be cool for surface tricks wouldn't it? Retract the fins spin 720 and then deploy them to stop

Perhaps something on the deck of the board - a switch mechanism that retracts or deploys the fins?

[NICKYPOO]

Sheesh, you just want it all don't you? Well, back to the push rods.

No...wait...how 'bout this? Have you ever heard of electro-magnetics? It is the future you know?

[Surfdad]

Did you look at that WW picture? The fins were connected to the kickpad and retracted when you were standing on the pad - pushed thru when you were...that concept works if the fins aren't too deep.

Electro mag's? I think you've been watching that vid too much - "WTH is an aluminum falcon?!"

[Tequilasun]

how about talking with some R/C guys. A little servo motor on the fins, and a control somewhere on top of the board or placed on the jacket.