fin placement accuracy ?

General Discussion
1

here we are shaping/building boards from personal custom dimensions, but borrowing fin placement numbers tested & favored by others. what are we really getting ourselves into?

if board length is one of the key factors taken into consideration when setting the center fin, shouldn’t we deduct the nose flip/kick segment of the board length that doesn’t play any role during entry & turning? after all, a number of shapers have long hacked off noses to keep length & weight down.

if tail width & planing area are also crucial to setting multiple fins, what’s the rationale for the spacing of each fin in any given cluster-- twins, thruster, quads, bonzers, etc ? in short, is there really a science to fin placement accuracy? everything else being equal, is going finless by way of channels, concaves and other intentional bottom features no different from boards with one or more fins? 

were your thoughts on particular fin placements the same after you tested them on the boards you made, in different surf conditions? hmm !

2

You're thinking like a scientist.  Doesn't work!

Surfboard building is an ART FORM.  ART, not science.  Art with experience, thru hundreds of setups tried, some failures, some successes, tuned the way the shaper and rider wants it.

A scientist doesn't surf well, because he can never understand how it can possibly work!

3

howdy lee D,

hmm maybe you could tell that to swayfolks who swear by mckee’s quad setup tables & the campbell brothers’ bonzer setup diagram ?

4

Don’t be absurd.

Tell that to Simmons, and Clark.

 

da Vinci?

 

Had mathematics and scientfic method been used routinely, many surfboard innovations and improvements could have been arrived at years (decades) earlier.

3-D constructs of thought?  Art?  Of course.

Inanimate objects with soul … LMAO

5

I might have a concept of fin placemant  you might be interested in. 

http://www2.swaylocks.com/node/1011665?page=22

Maybe best discussing here as it was a while ago I posted it.

6

thanks malaroo, you certainly put a lot of thought into it, allow me some time to review the thread & your inputs

cheers,

7

Its art, its science, its math, and its the feel.  Its the blending of curves, and flats; concave, and convex all coming together under the rider’s specific body type, and age, on a wave generated by a wind fierce and far away, or close and gutless.  In reality, its so much more than that.

Quantify and qualify all you want, and when you think you understand everything changes.  Kind a like women…

8

Fools gold.

You guys don't shape the same shape as the pros, so you will screw up the fin placement by using pro numbers, but YOUR shape, which can have thicker, thinner, more tucked, less, wider, narrower, flow distribution, bottom shape, all that stuff YOU did screws up the equation, so the fin placement equation is WORTHLESS to you.

But ...damn the torpedoes, full speed ahead.  Stick your head in the sand!

9

So stoked your back LeeD! 

10

ghettorat

I fully agree with  you, The stuff I try and do (find a relative design system for boards and fins) is only chasing what people have created. With out it I’d be coming up with bizzare stuff that didn’t surf. Well, not acceptable in the surf industry and probably inferior to what exists.

The human brain is an amazing processor, never under estimate it.

Even a womans brain, I guess!    

wooohps, did I say that?

 

LeeD 

You’ve seen the youtube clips, the boards and fin placements work, they are the same as a hand maker uses, that was the guideline, and there are many more principals than what I have shown so far. Can shape exactly the same as the pros, its not hard. I’m more interested in the classic shapes, classic mal, classic short board. Boards that work for the typical, person that works and surfs for fun. Thats where the market demand is. 

Lets say I make a range of sizes, different widths lengths, but the same model, and a guy comes and places the fins by is perceptons of where they should be, but they are all in different concepts of placement, that would make my models fins placement questinable … I think, worldn’t it?

Would you want a Pros boards where an experienced shaper has put the fins in a different place? I’m not asking to say your stupid, I’m asking what your answer is, I guess they would decide on a system the Pro uses and interpret it to the different sizes I dont know? The Pro will only ride a particlar size, doesn’t that mean another size is an interpretation?

Your right though, all those variations mean having a board that is right for the individual is critical, thats where a good shapers experience guarantees an appropriate board made by the shaper for a customer. 

Buying a pre made board to a formula without an experienced guide (maybe surfers own experience) would be an almost certain mismatch of customer to board.

Good points LeeD

11

 Heres my point.

 Most guys can shape pretty good boards.  But they are NOT nearly the same as what the pro shapers shaped!  Heck, one of the most respected shapers in SantaCruz (and I"ve heard this from Haut, Stretch, and RandyFrench), says he can't duplicate a shape if he shaped another shape between his matched sets.  Those guys have shaped a hundred thousand boards.  Are you saying your ONE shape is a perfect replica?

  Then given rider weights, wave speeds, surfing style, what may or may not work for a pro (professional shaper, not necessarily pro surfer), might not work on the board YOU made.

  I can't remember the number of times that a surfer brings back a board and says it "doesn't worki".  Upon checking, it's totally stock.  Given another surfer, it works GREAT.  That is ART FORM, not science.

12

howdy g-rat,

i certainly get what lee D is pointing out, however sways archives also tell us how scores of home & garage shapers are able to customize their own shapes for their own use while borrowing established fin setups for twinnies, thrusters, quads, bonzers & more. surely there’s art in blending wave knowledge to established designs of planing platforms using volumetric measurements to come up with well-performing custom boards.

fin setup on the other hand, for which a number of us refer to widely-accepted setup tables of varying distances in as close as 1/4" increments, are also measured. i’d be sticking my head in the sand somewhat if i totally disregard the tabular fin setup references in an attempt to re-discover what’s already been found.

i’m only asking how the fin setup tables, intuitively arrived at by others through extensive testing, happen to work on self-made boards by swayfolks worldwide. surely there’s a method to all that madness hmm

cheers,

13

Am I saying one shape is a perfect replica, No!

I’m with you on that one, all a CNC machine can do (with the right operator) is churn out a relationship between deck and bottom, type of bottom (vee, concave etc.) and deck curves and a ruff plan shape, then a craftsman is needed to do the rails, redo the bottom to whatever corrections due to whatever problems and the plan shape and rails and to blend all the curves when viewed from all angles. So much room for variation, every board ends up a unique interpretation of its original intention. With an experienced shaper, should be a good board, with a kid on a low wage and the need to sand lots of boards quickly, a disaster.

I personally am an odd ball CNC person, I’ve been doing it since 1990, and my system of creating a drawing is based on lines arc, splines and surfaces and especially surface intersections. These days surfboard design CAD’s use a pre shape and you alter it … Where is the relationship of everything? and its so easy to create a piece of ****. Creeps me out.

A quick overview of what I do, I noticed that a board (most boards, short boards and mals) cast a round shadow, So that means the round is actually the boards outside edge of some sort. Then knowing the length I created a Cylinder, (on computer) tried slices through the cylinder got ellipical curves and then did elliptical slices through the cylinder to find that creates a variety of mal shapes and classic short board shapes, so much like KS boards its uncanny. From those shapes created the rockers and the deck and the relationship of deck to bottom and even from those lines to create concaves and vees, all from the beginning curves. So its all related. Would you believe by associating the length to width relationship of boards the same principal creates fins. So that gives a fin shape that is related … True, I’ve only just discovered this and will post it soon on the geometry site above. The front curve of a fin is made from an elliptical slice that goes from one side of the cylinder to the other. The base shape of the fins foil is from a cylinder that comes from a circle with a circumference the length of a cylinder and a straight slice (not elliptical) from somewhere on the cylinder to the outside edge. FCS fins fit these dimensions, with a variety of interpretations. (slicing bits off the ellipses) I’m serious, Its all related. I don’t think anyone else in the world is studying this like I am. They’ve very quiet if they exist.
So my stuff is about finding relationships and creating a variety of shapes and lengths and widths and (soon) fins that are all related. I do believe if you try hard enough with the above method you can copy any board. (could take weeks though)

OK back to CNC, another thing that creeps me out is this scanning stuff. The files are totally unadjustable, (a scanned file looks like a book of coordinates) put in the hands of a novice CNC operator the chances of the relationship between deck and bottom being correct are slim. And the scan was a finished glassed board, so now its ruffed out at what should be final thickness … Can you see what a clever operator you need to get an exact copy … I cant do it with that method and I’ve being do this for a living for 22 years, yet thats common practice … FMD … No wonder people hate CNC’s.

I agree with you, I’ve seen the returned boards snatched up and loved by another … Even boards I had no respect for bought and ridden enthusiastically by a good surfer. Would have thought he’d take a good board (my perception), no not he case.

Thanks LeeD, for your input, good stuff!

14

I love the use of math for surfboard design, much easier to control variables, record/document failures vs. successes and replicate results.

I have not read your posts in depth.  But your 90-degree tangent to the curved surface of the foil seems arbitrary.  A 90-degree tangent to a circle has only one placement relative to the curve.  However when the curve is not symmetrical, there are many potential 90-degree tangent lines.

I suppose if you use the same criteria each time, the end result is consistent fin placement, assuming no differences among different fin foil curves or base lengths.

15

Thats right, that system requires accurate measuring the fin set you use to find the angle … great for set fins, or if you only like using one type of fin and great if you have a CAD drawing system , nigtmare otherwise. But Its possible to set up a spread sheet with the annswers because fins foils aren’t spread over such a huge variation. I just kept setting all my fins to that angle, seems to work pretty well. But if was making a board for a pro I would take the time and get it right.

Its also not that hard to do it by eye you when think in the way of the diagrams

You know I have asked people for years how they get their angles and no-one could give the reasons why … even fin manufactureers… I don’t know if what I came up with is right, it just seems to make sense to me and it works.

I think this is what you are asking about, hopefully the pics will appear below.

 

 

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16

Yes, those are the diagrams I was referring to.

There are many possible tangents (and angles).