Slot fins work great, still use them in both my boards. Good for rough conditions, the board won't spin out till later and comes back in quicker without as much lost speed. A bit slower though due to increased drag.

The Mulitifin clip at the front, little plastic thing just forward of the fin is crap, broke if you hit the bottom then you snapped the fin at the back when it swung down.

divaldo said...

I have an old one that I use as my 'reef' fin, I am not too worried if it gets bashed up too much, becase it already has a hole in it.

haha thing is probs when u do hit u will screw up the fin box as well.

I worked at Multi fin when they were just finishing making that model (which had the slot moulded into it). The next model was a standard fin with the slot cut out and routed on a jig. I was the guy who had to cut the hole, rout it and then sand it nice and clean. Not much fun doing that all day long.
I used to use both models and still cant work out if the slot actually did anything. (besides give me the schits because I had to cut and sand all day long)

I had a Multifins slotted fin and I think it was quick to recover from spinout. What happened to Multifins? I still use a couple of them, neither of them are slotted.

it wouldn't produce anymore lift, and the fin pressure would be less as well, but i can see the benefit in out control situtution, i used to have one on a wayne venn wave board i had was good for the 4.5m days...

The idea was the section in front of the slot acted as a canard. It directs more flow over the section behind the slot, delaying it's stall. So it can be used at greater angles of attack and more turbulent water without spinning out.
I made one that had the front section with a limited pivot, so that it acted much more like a fore sail on a yacht, that really did have more lift, just about lifted me out of the water before the fin snapped.

They were too hard to make, and with the improvement in foils, less necessary, and as already mentioned they had more drag.

Agreed decreptit, they do work as a canard (which is well known in aviation) so thus they should theoretically work.

And Easty yeah they did work! My theory (apart from canard wings working to incease angle of attack before loss of laminar flow occurred) was that when a fin spins out it is due to loss of laminar flow on one side... like a big air bubble (or vacuum) on on one side, so it slides sideways. A slot allows a transference of water from one side to the other thus allowing fast spinout recovery with less rider input.

Any doubters should go out on a 80L waveboard and 40kn with say a 4.0 - 4.5, in mega chop, and a normal 23cm fin. Then change to a old 23cm slotted one. I think it will work!

The pictured one, IMHO, was not the best. I reckon the best ones had a slot about 5mm wide and shorter than in this pic, much smaller, and the slot was beveled evenly all around so the slot has a "round bevel" at each end. When it is not so late I may try to find a pic

On aircraft they would be called Slats, or sometimes slotted leading edge flaps...

en.wikipedia.org/wiki/Leading_edge_slats

Works in the air, don't know if it works on a board :-)

I'm wondering why you'd choose a slotted fin in really high winds, to stay in control, over just a smaller (solid) fin?

Old farts like me will remember these fins well from the late 80's and early 90"s I think(it is really hard thinkin back that far) there were some bloody awful fins back then, and I think then the canard and slotted fins were a big step forward by helping to prevent spinout, but fins have come a long way since then with profiles and foil deisgn, and most modern good quality fins are superb in comparison and do the job very well. Having said that, the concept will probably get recycled at some stage by more manufacturers......

Mark _australia said...

racerX said...

On aircraft they would be called Slats, or sometimes slotted leading edge flaps...

en.wikipedia.org/wiki/Leading_edge_slats

Works in the air, don't know if it works on a board :-)

They are not equivalent to slats ..... slats are at a different angle to the wing (sometimes) and are attached..... no gap between them and the following foil.
IE a slotted fin is a foil in front of another foil...... = canard.

Well it's called a slot on aircraft as well. A retractable slot is a slat. I think its hard to call it a canard, a canard is a lift generating or control device equivalent to a tail-plane. A slot/slat however is a device attached to the leading edge of an airfoil with the specific purpose of improving its stall characteristics. So in function, i'd have to say it's definitely closer to being a slot/slat, than a canard.

Thou the fact that the fin is a symmetrical foil probably confuses matters a bit.

Also, there are slat/slots that leave a very visible gap between itself and the rest of the foil.

swoosh said...

Mark _australia said...

racerX said...

On aircraft they would be called Slats, or sometimes slotted leading edge flaps...

en.wikipedia.org/wiki/Leading_edge_slats

Works in the air, don't know if it works on a board :-)

They are not equivalent to slats ..... slats are at a different angle to the wing (sometimes) and are attached..... no gap between them and the following foil.
IE a slotted fin is a foil in front of another foil...... = canard.

Well it's called a slot on aircraft as well. A retractable slot is a slat. I think its hard to call it a canard, a canard is a lift generating or control device equivalent to a tail-plane. A slot/slat however is a device attached to the leading edge of an airfoil with the specific purpose of improving its stall characteristics. So in function, i'd have to say it's definitely closer to being a slot/slat, than a canard.

Thou the fact that the fin is a symmetrical foil probably confuses matters a bit.

Also, there are slat/slots that leave a very visible gap between itself and the rest of the foil.

Agreed.... but canards also enable higher angles of attack as well.... so work like a slotted fin so I say it is closer to a canard

jimbob SA said...

I too still use the Torquay slot fins in my wave board, would'nt have anything else, just wish they still made them for my powerbox board,
Ruush if you still have them old slots chuck them in the bus when you come down for the Oct weekend.

dam! pipped to the post.

Hey Gestalt, if you want you can score them as I don't really need them, I just know Russh, i still have a 10 and 9 inch in good enough nick, just send Russh a pm and i'm sure he will help you out.

OK swooshie you win