MyPaipoBoards Forums

Now run that horizontal to give lift!!

That would be interesting , having standard surfcraft fins that rotate into horizontal hydrofoils.

Surffoils,

There will be no stopping you with your own backyard flume. Are you trying the fins standing or prone?

There seem to be a lot of potential directions that you are heading. What feels most promising?

Bob

The Flume will be good to visualise how the water flows around each design over a range of angles. They all look smooth at 0 deg, but it's at what angle the flow starts to become turbulent and how it then flows that will bring a lot of insight. And all the specialty fof no like the Starfin, the Superchargers, fins with tubercles, close set twin fins,floating fins, tunnel fins...all those other fins that are interesting.

Personally I like both the Twin blade fins and the Floating fins I make, they're both a different experience to ride and after 50 years of surfing , it's great to have Something really different .

I'm really caught between spending ( wasting ) my time building either the twin blade or the Floating fin designs.
The Floating concept is the most interesting so I'm sticking with that until I see something shiny that distracts me.
Here's the latest...
My idea is that if I can get the 'fin' away from the hull it can then be its own design, no longer a dorsal shape it can be any shape t all but probabaly more of a 'stand alone unit ' irrespective of convention.
Hers the basic shape, without the base area for drive I've made it more of a longer shape to offset the loss of base. And with the perimeter free I've folded over the top and bottom edges with a 'wingtip' folded towards the stringer. Convention would have the tips folded towards the rail but similar to a Webber CRV fin, the idea is to hold the flow on the inside of the fin for longer, increasing the drive effect.
Here's the paper plan and the foam block that I will vacbag layers of glass, carbon and veneer over.

It's all open for variation but without the first step it's all conjecture.

So I've vacbagged layers of glass and veneer over the foam mold and when it's set, pop it off the mold and it's ready to shape. If you put the same number of layers of glass together it wouldn't be as strong as when you separate them with the veneer.

Only 4 mm thick but because of the bends it's not going to break.

Brett,

Is this last photo the floating fin? No doubt you've already explained it, but what the idea behind this fin and what difference is there in how a board rides?

Bob

Thanks for the question Bob, yes it's a 'Floating' fin, the idea is that the base of any fin constantly interrupts the flow along the hull and it adds massive drag, more drag than is needed because you can turn a surfcraft without a fin but we all have these big base fins. However if you lift the fin away from the hull it allows the flow to slide along the hull contours. The Floating fin area still creates drive but with less drag. It's not a pro/ hardcore fin but more of an " Experience" fin. Because the fin is sitting away from the board it's way more stable.
You ride it and say Oh I get it !
If you wanted to do nothing but race along waves as fast and stable as possible this is the fin. It's not slower, just more stable.
I'll work on making it turn and pivot more in the next version.

Brett,

Thanks. Ok, I think I get it now. I suspect if you surfed rocky places there would be a high risk of snapping the bases (I managed to knock out all three of Malaroo's fins at his home break, which is a rock shelf).

Is there much noticeable sideways movement in the fin or is it pretty subtle? Does fi performance change much as the surf gets bigger/hollower?

Bob

Bob, I've had them out in beachbreaks from dribbler to head high on a glass paipo and a surfboard and it's the same experience of lots of drive for little effort. Standard surfboard fins try to be good at everything but this one is just for getting down the line with the least effort.
The posts on this set are 12 x 3 mm but I'm doing 6 mm round posts for the next ones. You'd think the posts would create a lot of drag. but they don't.

I'm enjoying how these fins ride. You don't have to design them like a Wing added onto a plane but more like an individual entity, it is its own craft. The central area is like a foiled fin but the angled sides are thinner and designed to provide a Newtonian hydrodynamic effect.
They're very stable but I think I can improve them with a few small changes.

More testing today on my DIY paipo. Lots of good things about the new fin design but there's always more to discover.
New fins to come...