Wave fins - how to they differ between singles and multi

manuel · Joined: 08 Oct 2007 Posts: 1158

Can the center fin of a tri fin be used as a single? Can one of the rear two twin fins used as a single?

I tried an MFC tf200 as a single but didn't get the extra softness I was looking for. It still felt hard to break loose at the top turn.

Shouldn't multi fins have more flex than singles?

U2U2U2

spennie · Joined: 13 Oct 1995 Posts: 975 Location: Thousand Oaks, CA

As long as we're talking about fin flex, has anyone ever heard of a flex-fin for windsurfing? I realize that all fins flex a bit, but in my 24 years as a sailor it's always been trying to find the stiffest material - hence, G-10. Did anyone ever make a purposely flexy fin? Did it work, or was spinout too much of a problem? Seems like a single flex-fin would work in waves, if not slalom. We used to make our own surfboard fins in the early 70's, and sometimes we'd make them really thin so they'd flex, seemed to work really well surfing, would kind of "boing" you out of a turn.

Hmmm. Maybe I'll take a power sander to one of my old fins.....

cgoudie1 · Posted: Fri Jun 20, 2014 11:07 am Post subject:

I have a "Wardog Extreme Wave" 8.5 inch fin that is billed as
flexy, and I love it! Not sure what the material is, but the tip does
bend off quite a bit, so probably not G-10. I also have a Curtis
9 inch that is G-10. Also an excellent fin (you can really get on
the thing without spinning it out), but not nearly as "surfy".

-Craig

manuel · Joined: 08 Oct 2007 Posts: 1158

I'm sorry I wasn't very clear.
I'm referring specifically to shapes and flex not size per se.
Can any of the "multi-fin" fins be used on a "single-fin" board?

This is MFC new high flex design: http://www.mauifin.com/windsurf/pro-flex/single-wave/ Looks super sweet. But the thing is 20cm is still too much fin for me (sailing a 77 freewave with a 5.0) OR maybe thanks to the new flex, it feels smaller?

Anyway, the multi-fins are available in much smaller sizes but have a different design. Below blue is single, red is multi.

Multis appear to be more raked back and wider uptop.
They seem to have more surface overall.

I use the stock natural wave 24cm on an 86L wave board, it's quite soft and spins out easily, I have tried three fins on my fw77 the stock rigid fw 23cm, a fw20cm quite rigid too and the center fin 20cm of a tri-fin (the red one above). The multi-fin fin had a little bit smoother flow than the fw 20cm but not much difference overall.

isobars · Joined: 12 Dec 1999 Posts: 20935

U2U2U2 · Posted: Sat Jun 21, 2014 12:52 pm Post subject:

manuel

sure multi fins can be used on a single.

The smallest FIN I have ever had for a single fin board was a 19cm

the largest multi fin that I KNOW, ( without look at all the fin companies sites is a 17cm) the area of a 17 could reach pr equal a 19cm fin, could.

your lastest post has me confused what you what or are trying to do.

There is no reason why you cant use a pair of single fins, like rx in a HiFly Twin, doing the opposite would be limited only by the size. Of course the overall shape, would have to be acceptable.

manuel · Joined: 08 Oct 2007 Posts: 1158

I'm trying to understand shape differences between multi-fin and single-fin designs.

If we can interchange them then why would the shapes differ?
Also, which one has more flex?

My understanding is that a design with more flex allows us to get away with more length (useful to go upwind on side-on conditions) but feature the looseness of a smaller fin (useful down the line.)

U2U2U2 · Posted: Sat Jun 21, 2014 10:01 pm Post subject:

[quote="manuel"]I'm trying to understand shape differences between multi-fin and single-fin designs.

If we can interchange them then why would the shapes differ?
Also, which one has more flex?

My understanding is that a design with more flex allows us to get away with more length (useful to go upwind on side-on conditions) but feature the looseness of a smaller fin (useful down the line.)[/quote

Shape is going to be dictated by the designer. Multi fins have many different shapes including weed.

The shapes on single fins from MFC MUF BPF K4 Choco TFC True Ames Mankani are not going to be the same, similar. Stands to reason without going into Fluid dynamics, which I dont feel qualified to irregardless, that multi fins in the same length will have different shapes, areas.

If the fins are G10, and their exist several stiffness of G10, the fins will be stiff compared to most if not all other compositions.

Flex in itself is only one characteristic of the fin ,I would NOT consider a flexy fin to be used longer, instead look at one that was the same length, but more area, to achive upwind et all.

K4 say on the Flexy version

Our original fin for performance wave riding. Lots of flex for amazing grip and looseness on the wave. Raked template for control. A progressive foil for different flows between tip and base. Test winner. Will loosen up a 'stiff' board and are particularly sweet as twin fins as they eliminate that unwanted top turn spin out.