fin placement question for midlength

General Discussion
1

I’ve got a midlength board completed to the point I need to add my fin plugs.  I want to go quad with thruster option, so 5 boxes.  I’m mainly a single fin guy, so not up to speed on either, especially on a board of this size.  But this board was made with the intent to break away from single fin addiction, and try something different.

  • Board is 8' long by 22" wide 
  • squash tail is 10"
  • 16 3/4" at 12" up
  • nose 16" at 12" back
  • slight concave in nose blended to flat in middle to V in the tail (slight double concaves through the fin area)
  • rails 50-50 in nose, fat down rails (with a tuck) in the middle, hard down in the tail

Any specifics on fin placement would be appreciated!

Also, any fin recommendations appreciated also.  Right now I just have the probox quad fins that I ordered with the probox plugs, inexpensive but maybe not best performers?  Open to suggestions.

btw, a friend sent me some info, but I didn’t grasp it, really.  He said

Does this mean the trailing edge of the front fins are at 16" up from the very tail?

I don’t get the two measurements off the rail for the box, I need a measurement off the rail for the fin, not the box.  Also, I don’t want two measurements, I prefer an angle for toe-in, or tell me where in relation to the tip of the board the convergence point is.  Which I found in another diagram, saying (I think) fronts converge at 3" in front of nose, rears converge 1.5" in front of nose - I’m pretty sure that’s what it said, does that sound right?

Also, where do I put the trailing edge of the rear fin for a thruster setup?

I hope this makes sense, and isn’t too repetitive of stuff already posted.  I read through all the threads I could find on longboard quads, and even ‘tho this isn’t a longboard per se, at 8’ it is closer to a longboard than a shortboard.  

Thanks in advance for any help!

2

I would go to a surf shop, or ask a shaper who does board’s in that size for best results. Bring a rular with ya and you’ll have your answer.maybe - a inhouse guru will chime in…

3

hi Huck, what about Hanaleis set out? they have it on the site - actually they have layouts for all fin set ups.

4

Thanks Karuhi - I looked but was unable to find the page you referred to.  

Trying to piece together what I can from the archives (and there is a ton of good info there, its just trying to sift through it for someone inexperienced with the multi-fin setups), this is what I have come up with so far… (the front fins would be 1" off the rail at the trailing edge, and the rear quad fins would be 1.75" off the rail at the trailing edge)

Cant is another issue, but since I’m using probox plugs I can change the cant by means of the inserts.

Again - still looking for fin recommendations as well.  Probably read through the stoker-v thread again, and see what Bruce is recommmending, since the boards are similar in concept.

Thanks Jim, what I’m really looking for is some imput from those who have built, owned, or ridden a board like this, and have some firsthand knowledge of fin setups that work  =)

5

16" from the tail to the back of the front fins seems too far? I’m no expert but I think that 16" would be to the front of the front fins. 

6

thanks ekim I will research that further - there doesn’t seem to be any standardization for measuring or reference points, so often when I read a dimension its unclear to me exactly which part of the fin or box is being referred to!  

I find a lot of statements like Fronts at 16" which is vague, but at least one swaylocks poster specifically said front fins 16" from tail to the rear of the fin.

I agree with a comment Bill Thrailkill made sometime back that the leading edge is the best reference point, but I find that rarely to be the reference point in use.  Back to my homework!

7

 

Rusty, along with a few other prominent shapers discussed quads:

http://www.surfline.com/blogs/talking-design-the-board-blog-with-rusty-preisendorfer/rusty-breaks-down-the-ingredients-for-a-perfect-four-fin_38677/

 http://www.surfline.com/blogs/talking-design-the-board-blog-with-rusty-preisendorfer/rusty-looks-back-at-the-history-and-evolution-of-quads_38953/

personally, like my 8’0 thrusters and 5 fins set up with fronts at 13", rear fin at 4.5", trailing quad fins splitting the difference between fronts and rear, and distance between stringer and rail, pretty much the Rusty influence, not surprising since these days I have my boards shaped by a former Rusty shaper…lol.  Have found that combo to work whether 8’0 x 21 fun gun or 8’0 x 22 mushbuster.  In the end, always seem to go back to thruster for average surf with lots of turns, stick in the quads only for barrels and haul okole walls.

 

8

If you’ve never surfed a quad yet then I think you should try that first without the rear box.  They’re sensitive to fin sizing so you may have to do some trial and error with fin combos.  

I think Robin Mair likes to set his boxes close together, like 1/2" apart between fronts and rears.  But his fin designs are different than most in that he likes really narrow bases with more of the fin area at the tips. He also runs fairly narrow tails, often a rounded pin.   For an 8ft board his page calls out a 12.1/8" from the tail for the trailing edges of the fronts and 7" to the trailing edges for the rears.  

With the more conventional quad fin designs I think whether you stagger your fin sizes or keep them the same or similar in size makes a difference where you put the boxes.  Personally, I usually stagger my sizes by 3/4" or 1" or sometimes even more, so the narrower fin base at the rear increases the spread.  

 

For the last quad midlength I did the rider was 170# with a 7ft board, and I set them at the rail - same toe in - at 6" and 12"; and he used the 3.9" longboard sidebites for the rears and the 5.2" twin for the fronts.  He liked that combo quite a bit.  He used the same on the 6-6 MyCoy-style double ender I did for him, only set back a little further at 5" and 11".  I was prompting him to surf off his tail on that board.    

 

You’ve got a fairly straight rail line in the tail and a wide tail block so I think it will require a comparatively larger amount of fin area.  

9

16" in front of box = about 12" - just minus the widths of fins from front of box…or measure from front of fin back the width of fins according to the settings your friend gave you…

The rears = 4.5" and the fifth fin 1 3/4" . This sounds about right?

10

OK, reading through the comments and studying all the photos I can find, I adjusted the measurements, as below, then marked it on the board.  Hard to tell by comparing to other photos, since I’m using probox and the pictures I find are using a different brand, which I don’t know the dimensions of.  The probox plugs are pretty small, something like 3.5" long, I’m guessing the Futures are longer, anybody know?

 

11

Huck, my compliments on another fine board.

I started out looking for 2+1 advice for FCS sides on an 8-footer and I ended up with a McKee M5 longboard layout with Probox quads.

http://www.swaylocks.com/forums/fin-setup-80-funboard-please-advise

http://www.mckeesurf.com/?page_id=270

12

Well… the first thing is to just go for it. You are a smart man.

The Swaylocks good intenions / bad information plays hell with me. I’ve been led down the wrong path many times…many times.

I did a “simi gun /cal gun” with fin placements from some of the best…board sucked…why?  because I don’t ride simi gun waves…my bad.

Huck,It’s not my project…but if it was my project  I would start with a 10 inch long board box and build the quad / tri set up around that. You can buy small fins for long boxes in Oceanside…

All my Speed Eggs are based off of that one awesome 7’6" board that I bought off of the rack years ago…funny how that works…I’m making a copy of a copy…

Ray

edit…oh yeah…one more thing…all this McKee stuff…not for me…me and Mckee don’t surf the same waves…I’m sure he’s not surfing sloppy fishy stuff that I ride…

13

Hey Ray and Randy (and everyone who has commented) thanks for weighing in on my project, and for the kind words.  I feel the same about McKee as you do Ray - he’s the four fin guru, without a doubt, but rides waves very different in size and power from what I ride.  I notice the California quads tend to keep the back fins closer to the rails, and toed-in, whereas his are pulled in closer to the stringer, little or no toe-in.  Robin Mair is another quad expert, but again, based in Hawaii.

As far as good intentions / bad advice: I think this is one reason it can be difficult to get a specific response when asking a design question.  What’s good for the goose isn’t always good for the gander, and no one wants to get hit with the follow-up post “thanks for the bad advice”, LOL!  

For that reason I just ask for suggestions, try to get as much information as I can, then factor in my own limited knowledge and opinion, and come up with a workable result.  I’ve had some outstanding successes this way, and some outstanding failures, but my worst failures always seem to be when I go out on a limb with my own half-baked ideas.

I’ve reviewed my notes and drawings, re-read all the pertinent info I could find, and finally came up with a final layout I’m happy with.  I consider this my best guess, in other words, haha.  The measurements on the diagram below refer to the back of the fin slot.

14

Huck, That board looks really nice. Clean lines. It should bea winner. You seem to have already settled on your fin sets. But for future reference take a Look at Blair Custom surfboards web page. He talks about moving his fin set up by about two inches from the normal thruster set up for his mid length boards
he was useing a thruster set up but I can see it working for quad. or a 4 / 1 set.

15

Sounds like you got an education eh?

The Rusty link was good stuff, yeah? And of course the Sway’s archives, overwhelmed with all the data, one can only digest said info and make up your mind as to the best approach (for yourself) and DO IT!

Eh maybe we can compare notes, later…

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16

It seems to me that if you’re doing a SVM-type design that you might consider fin placements similar to what Mr Fowler does with those.   

17

Artz, thank you, and thanks for the tip - I checked out his website, and he is definitely on the same page as I am with this board.  To my surprise, he goes even wider / thicker than I did - I thought I was pushing the limits, but he is way ahead of me.  At 22" wide, 3 5/8" thick, I couldn’t carry this board if it were much thicker or wider, but he has the answer for that - he puts a carry handle SUP style in his!

My rails / bottom configuration are modeled on comments made about the Mahady Lineup Killer, but are surprisingly similar to the rails and bottom he describes / shows (in the video) on his old-guy performance board.  I’ve saved the website in favorites, gonna spend more time studying his boards and comments.

I’m really in the dark on the quad setup, so have to start somewhere, but paid close attention to his fin layout - much further forward than standard.  For this board I guess I’m gonna go with something closer to the SVM and Lineup Killer models, but if the shape works for me, I’ll very likely try the farther forward layout that Blair advocates.

Very entertaining guy, my wife said he should be a motivational speaker hahaha!

18

wow, I just wrote a lengthy reply Matty, and inadvertently hit SOME key, dunno which, and it all disappeared!  Anyway, yeah, I read it all and then some, lots of varying / conflicting often confusing info, just have to pick a starting point and go, then eventually I’ll have some kind of experience as a reference point.  Right now just completely going on blind faith in the work of others, but ready to break away from my usual single with sidebites.  I do have a 7-4 thruster I built and really like, but seldom use cuz I need more paddle power for the crowded / competitive venues I frequent.  I guess I could hedge my bets and add a long single box in the middle… I’m waffling haha!

19

gdaddy we are on the same page here.  I studied hard the fin layout pics on Bruce’s thread in the surfshop forum, as well as any pics of Mahady’s Lineup Killer that I could find.  This, ultimately, was the strongest influencing factor in where I put my fins on this, my first real quad.  And again, its just a semi-educated guess, so no one to blame but myself if it doesn’t work out.

I know some involved in the SVM have been opposed to introducing new fin layouts to an established design, but Bruce has adamantly stuck to his propensity for diversity, LOL, and is producing quads on a pretty regular basis now I think, as well as a variety of other design tweaks.

20

This otta cover it “do what you know and don’t be slow”.

Your set up looks fine to me, taking the tail width into consideration.

??? why same toe in ??? For me 1/4" front and 3/16" back.

Let us know when your gotta rock the “Banana Boat”! LOL