Short board fin position formula. Or am I Tripping!

General Discussion
21

I guess the things what is Magic for one surfer may not be for another?

The 8' x 20.5" x 11.5" tail, has vee starting @ 2' from tail, (3 degree rocker kick here - and I "discovered" a secondary slight kick @ 17" just in front of the side fins... Stoked on that bit-o-knowledge!) going from 1/16" to 3/16" @ 1'/tail end of side fins - with 1/16" concaves between fin(s) and stringer.. Then fading to 1/16" as concaves resolve, and near flat behind rear fin.

Makes me wonder about getting rid of most of the vee to follow thoughts on other more flat/concaved bottom types... I love the way my boards ride... What can I say.

The earlier magic board I wrote about 8' x 18.5" has an 11.5" tail and the fins are at 4" & 12".

There are a lot of factors: Where is the board going top be surfed? Like I said the table I use is only a reference and will vary depending apond the situation and the surfer the board is intented for!

22

SD - I’m stoked on the table… Makes me wonder about the fin placement on my longer boards: 9’-10+'.  Speaks to the scaling thing, rules of thumb, and the variations which may/may not equate to “magic…” 

Hope you didn’t think I was putting down the table… Like I’ve tried to point out, other than Sways, I’m working alone up here in the wilds of the central Oregon coast…  and my scaling method my not have served me as well as could have been.

23

It's all good. My formula works for the boards I build and the surfers who surf them. I was only sharing what I do. I never claim to have the answers. Just what has worked for me. You may have a whole different approch. My theories are tried in Indo, Chile, Hawaii, OZ, MEX, California. Maybe what I do doesn't work in Oregon?

24

…yes, you re tripping…

like others said there s more variables than the distance from tail

also, in big thrusters and in semi guns and guns, having the side fins too far forward generates trouble in late huge drops due to not accomodate fine with a hollow wave face

25

Hi SD - Feel like I’m still coming off as kook, and I don’t mean too.

I’m trying to point out that I started from a place and when I scaled from there it came out differently than what’s on the table, and, in fact, the starting place was different from the table, and, while the board(s) work well for me, they may very well have worked better had I started from a different place, or adjusted my placement - esp. for my longer guns - base on the information in the tables you’ve provided.

Hope that makes sense.   I fully appreciate all the stuff you share.  Like I’ve said many times… In many respects I’m just a self styled kook asking questions.

26

I think what you are doing is great Yorky for the reasons Surfding mentioned above and makes more sense to me than just adding a fixed amount to positions as board length goes up.

I’ve measured my footprints across 3 boards - 6’ 3" chip to 6’ 10" stepup and the distance between my feet is the same, however what happens as board length goes up is the same experience as Everysurfer’s - both feet move up the board. I’ve been looking at pics of the elite surfers and this seems to be the case with them too. So if you could come up with a formula which uses actual foot span rather than estimated you could get your customers to bring their boards in, measure their footprints and then plug it into the formula.

[img_assist|nid=1045803|title=comparison of stance/board length|desc=|link=none|align=left|width=480|height=640]

27

Reverb,

Thats just the thing with the formula I did “It’s NOT a formula based around a distance from the tail”

Its like a floating formula based on the smaller board then “%” (everysurfer quoted %) ratio moving up according to something other the  surfboard.

Its like if you were to scale a boards shape dimensions by ratio by alone (mind you I know I know not every surfer wants exactly the same board because their not the same people weight /height/talent/waves required for the board). But I’m 67 kg and ride a 5’ 10 x 18 1/4" and I’m in the water every other day surfing. I get a lot of people coming to me saying just give me what your riding but in a 6’4". If I were to use a fixed ratio and scale this board up to 6’4 it would end up being 19 7/8" wide. Little bit wide dont you think.

The width : length in a true ratio would have my board increase its with by approx 1/4" (0.2607) per every inch up I feel this would be a bit excessive.

Thraikill (I think) said “increase a boards width by 1/8” for every added 1" in length" as a GUIDE only.

If I were to increase the 6’4" order up by 1/8" per every inch up then the board would come to a respectable (appropriate) 19" wide.

Thraikill method is what I tried to do with the above fin formula.

What prompted me to debate you is when you said, **“like others said there s more variables than the distance from tail” **I’m Not asking you to re read it, but it really has No direct referance to board size.

thats exactly what my method tries to get away from, it’s like a “floating fin position formula based on another variable”

I’m just a shaper with out a good education so I’m Not saying its the be all and end all, but i’m going to put it to the test and compare the results alongside my existing fin positions and see if it has merit.

If you like your Back fin 1" from the tail and side 18" up (something stupid like that)  you can use this formula to find relative positions for scaled boards, in conjunction with the common theory that as you go longer with a board generally you go narrower and also stance.

FOR SCALING SHORT BOARDS ONLY, NOT GUNS MADE FOR A PERSON OF THE SAME WEIGHT WHO JUST WANTS A BIGGER BOARD. I personally think that SD’s true ratio formula is great for scaling up boards for one individual from short boards right up to big guns.

…However you are right, “I was tripping” it was a long-winded writing.

Peace

28

MrJ,

SD 's formula is true ratio.

divide the orignal fin positions by the lengths of that partictular board, then multiply the given number by any of the length of any size board on his scale and you will come up with the positions given on his scale.

eg 3.5 divided by 72"(6’) then multifly buy 78"(6’6") and you will find the position matches his given position… same with the side fins.

Perfect for scaling up boards of the same width, Like shortboard to semi gun to gun to big gun for the same person.

I’m thinking of positions relitave to:-

1 a different person (of roughly the same build as the person you want to scale from)

2 a narrowing board as the board gets longer (Thrailkill formula)

peace

 

29

Yorky I think you get it!

I just took Brewers Formula and formalized it.

I seen a lot of guy's out with 10'0's at Sunset with the fins set just like the formula I posted.

All the guns I made for Puerto Escondio worked great with this formula.

That's what I do and it works for me and the surfers that ride them like it.

For the LAST 7 years this is the fromula I have been using before that I just guessed?

Reverb may have a completly different formula for guns that what I or many others use?

I would love to see his formula spreadsheet to compare with.

In the meantime I will just keep building boards my way right, wrong or indifferent?

 

Surfding

 

30

I’ll be using your formula for scaling my guns for my customers. Its makes perfect sence.

Cheers mate, keep up the good work… hope you get better soon, you got the flu, right?

31

Derek Hynd has a solution to the fin formula…not so sure how well his system works at Sunset though…

32

…hello Yorky,

reading your first comment cannot conclude that your talking about a “floating formula”

you start with distance from tail and then change it regarding only length.

why and in which way your formula is a floating one? (applied)

 

1 variable is the fin size; so seems that your formula only regards to back edge of a fin

what happend if the fins have more base or more tip area and less rake and vertical cord?

to name only one variable…

 

also, like I say before and J Mellor say, if for same reason a given surfer has the fins too far forward in his shortboards or mid length boards and wants a lboard or semiguns, etc seems that with your approach the side fins will be too much far forward, and that is not good.

this is one of the reasons that I said in previous thread about single fins in guns, etc that the thruster is a concept not only 3 fins and works fine until you put too much far forward the cluster as in guns or longboards

so in my opinion, there s better fin systems when the design or the surfer demands situations that a thruster (bonzers, singles, quads and in some cases, twinzers) cannot excel.

 

 

33

What is your formula?

Photo's?

Charts?

34

…hey Surfding, I never said that I have something like a formula as may be the 99% of shapers…

 

35

reverb,

With out going over things again and again my formula actually is designed to pull the fins back in relation to the board getting longer. Because it is common practice that boards get narrower as boards get longer. I believe the fins should go back towards the tail as they do. Thats is the basis of this formula.

**seems that with your approach the side fins will be too much far forward, and that is not good. **Your statement here, with all due respect, tells me you dont understand the initial post from me (1st post on this thread).

How do I say this with out sounding like I want to insult you, I dont.

**“floating formula” **Bad choice of words from me, sorry to all for this, you are right. You have to have a point of reference to mark your fins.

I just mean as the board goes up in length it gets narrower (lets forget about stance) there for, the fins comeback as per a determined amount per every inch that the board increases. 

I do confuse myself on occasions, ha ha. But its just a formula. Theres a formula for everything, its just how deep you go mathematically to how long and confusing the formula becomes and what it explains. there’s a formula for making eggs. Its lunch time!

see ya

peace

 

**
**

36

Here’s my latest formula

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37

surfding,

I’m making myself a new board this weekend with the magic fin settings you PMed me, I reckon i might just like em, ha ha. Also I got some Inegra 2 oz from Huie to use. Really looking forward to doing it too.

Think I’ll start a thread of the build and follow the life of the board.

Cheers… Back to my box now.

later

38

Yorky:

VACUUM =

The first board I just glassed in Innegra looks so good and is feather light. 5'9" x 19" x 2 3/8" Quad back fins at 5" with 1/8" Toe 2" from rail 5 degree cant. Front fronts at 10 1/4" 1 1/4" from rail 1/4" Toe and 7 degree cant. Tomorrow I will weight it after it's sanded.

Second one is kind of complicated and I will finish it after board three.

Board 3 is sitting on my shaping rack with just the rails to turn and mark the fins: 6'1" x 18 3/8" x 2 3/16" Thruster 3 1/2 center and 11 1/8" fronts with 1/4" toe set at 5 degrees. This board has a single concave running down from the middle of the board out the tail. Innegra is in the mix as well as some secrete sauce.

Board 4 I start on the blank tomorrow and will pull out the arsenal from my storage. The core on this one is going to make thing interesting. Innegra is in the mix as well as S Cloth and a few other things.

Huie has been my guide through some of this. The man is a Legend! It's Pretty cool you live by him. Talk him in to giving one of his CDD blanks! I've tried for a couple of year to get Peter Hoskins to send me one! I'm making boards for some Aussies from Byron Bay. Are you close to that part of OZ?

 

Kind regards,

Surfding

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Wow!I’m looking up fin placement so that I can put high density foam inserts into my blank tomorrow around the fin positions, and I just thought I’d (quickly) find a rule of thumb that’s fairly straight forwards that I can follow so as to know where to stick my fins; being a first timer as I am. These threads have kinda daunted me a little- I didn’t realize how deep the world of fin positioning went. Can anyone recommend a particular formula for me to use that’s a safe bet to begin with that’ll give me all round performance; I hear of several being mentioned? 

Of this subject I only understand rudimentary principles of why you put fins back, toe in, cant etc and have absolutely no idea as to how to come up with some functional numbers out of it all. Any recommendations or website links would be lapped up. Nice one.