Straight fins for small surf?

General Discussion
1

I am planing on making a fun small wave board for mushy/small days. After google searching for some time, I read this at www.surfersteve.com~

“A fin with straight lines releases water easier than fins with a
conventional curved shape. This has been tested in wave tanks with
strain gauges and photography. When designing for easier turning in
mostly chest high or less surf, make a fin that is more upright, (rake -
20 degrees from perpendicular) with straight lines (a parallelogram).”

Does this theory have any merit? I know nothing about the engineering and physics of foils.

The fin template he suggests is this.

small wave fin

 

THANKS!

2

Here is some information with regards to "straight" fins: http://wavegrinder.com/surfboard-fin-science/

I am making a set at the moment:

 

3

Great info! Thanks for the link. After checking the site out I found this link http://www2.swaylocks.com/forums/wavegrinder-fin-ride-review

If I want to make my small wave board a twin fin, would I use a fin like the one I posted/wavegrinder, or do I need a smaller version?

4

I am making a twin fin small wave board at the moment and that idea did cross my mind at one point,  I don’t think I’ve ever seen it done in practice. Although, it’s probably been done well many times. I just finished one fin yesterday, I copied my futures t1 template but made it slightly larger. I’m enjoying those on my other board right now. I’ll have to read those links eventually.

5

I hope you don't have any kelp in your water.  Upright fins catch any and everything floating in the water.

6

!!!

Smart thinking. Luckily there isn’t alot of kelp at my surfspots.

7

I think I'm going to try Surfer Steve's recommendations and order some 8” molded fins to cut the parallelograms from.

Steve recommends the fins be cut to 6” in height. From your experience, does that sound like a good number? (It sounds a little tall for a twin fin to me)

 

8

have dabbled with similar fins but less drag doesnt mean they are better for surfing performance…but best to try everything that seems to have potential and learn from it, take the positives and use them in future designs…

www.MOREsurfboards.com

728×546 73.7 KB

9

[quote="$1"]

I think I'm going to try Surfer Steve's recommendations and order some 8” molded fins to cut the parallelograms from.

Steve recommends the fins be cut to 6” in height. From your experience, does that sound like a good number? (It sounds a little tall for a twin fin to me)

 

[/quote]

 

In my experience making fins or modifying fins is no easy task. I've done it. I can buy nice fins from several Swaylock's members for a good price. That $65 ProBox fin set is really cheap when you add up your time...$100 longboard fins sell used for about $25....find a deal. Why start with an el cheap o moulded fin? If you feel the need to make your own fins use quality wood or 36-46 layers of fiberglass.......

10

 

Since I don’t know where to find straight fins, I figured they could be cut from a pre-existing fin. Does anybody make straight fins similar to ones I’m looking for?

11

They can, but you would have to modify the foil throughout. It would not be just the case of cutting out the fin plainshape and smoothing out the edges.

Ive done something like this with an FCS G7 fin. I hacked away the curved tip about 1/3, and straightened the trailing edge. I then had to sand the fin at the top and bottom to match the foil of the middle 1/3 of the fin.

I left the leading edge as is.

So in the end, the only curved bit was the leading edge.

Cant say it improved anything...

 

12

 hi 'retro' !

 

  ....do you have a photo that you can post here , of those modified G7 fins , please ?

13

Do an Internet search for ProBoxLarry. Check out his blog stuff. I see Wind surf fins and kiteboard fins that fit the shape you are looking for. Maybe a little bit longer. One Kiteboard fin set up I saw was close to something you could use on a surfboard. Surfer Steve is not breaking down any doors. If you want to go outside of the box stay on Swaylocks for a while......TaylorO is doing some interesting stuff right now. Lot's of Roy Stewart stuff to look at. ChipFish builds em and rides em......

 

14

and wildy .....

 

 

  and ryuzo nagakawa's blog ....he is in japan...

 

  WHERE are YOU situated , 'cwroe' ?

 

  cheers

 

  ben   chipfish   / "chippy61"  [thanks for the mention , Ray !]

 

15

Southern California, North Orange County.

16

its only my thinking and i may be wrong [we ALL are often enough ?!]

 

  but hopefully the combined area of the four fins when i have done quad sets [for myself] doesn't end up 'much' more than say a LARGER  thruster set , or a single fin [say,  5 1/2" - 6 1/2" deep , maximum ] , combined with medium sized size fins [eg: fcs '  M5 ' or similar templates ]

 

  but as I say , this is only a rough guide for ME , others may vary , depending on waves , boards , body size , surfing ability / what you want to FEEL whilst surfing

   

 some "straightISH " templates included here ....

[I guess , apart from the foil, if you reversed these .....you would have [a] 'reverse rake ' ...these are from Ryuzo Nakagawa's blogsite .... ]

487197_139119159545659_1987522612_n.jpg

ditto with the 'webbers' [curved] template ...

BLOG4979.jpg

 

and of course , you could do mini 'spitfire' fins , smaller versions of the ones that probox larry does ...

 

and ...maybe this , [thanks , beerfan , for the "wavegrinder" !! ] .....but at 1/2 to ? 1/4 ? of the size , and minus the 'winged tip' . It "could " be worth experimenting with ??  [as side fins , fcs tabbed , I mean ....]

july19th201116.jpg

 

  ...there is really only one way to find out , though , I reckon !  [and I DO have , oh , around ? 40 ? fin panels , at the moment ...uh oh !!]

17

[quote="$1"]

 hi 'retro' !

 

  ....do you have a photo that you can post here , of those modified G7 fins , please ?

[/quote]

Here ya go Chip!

You can see th scuff marks where I had to sand down the surfaces to even out the foil.

18

cheers retro !

 

  how deep did they end up ?

 

  deep enough , you reckon , or not ?

 

and , if you still have both of them ...

 

  do you reckon , as an experiment based on this thread , that you could now further modify them , so that the back edge's rake is reversed ?   [ ie : sloping towards the FRONT of the fin ] ?

 

  see if you can feel any difference surfing them then ? [ although , you may need to make a deeper version , to really FEEL any difference , is my feeling ...]

 

 cheers retro

 

  ben

 

 

19

Part of what fins does for board performance is 

that of propulsion. Vertical template (high aspect) fins

get through the water creating a relatively small amount

of turbulence and thus they are speedy. They are also

very pivital in the way they turn and don’t give much drive

or spirt. Thus they don’t give great propulsion.

 

No Worries, Rich

20

Cedar Fins J. Lukas

 

Cedar Fins J. Lukas