Quad Fins - McKee Formula - measurements and pics

General Discussion
1

Good Morning, I’m glassing quad fins for the first time using the McKee Formula. My goal is to ride this shortboard in steep waist/head high waves, so pivot and hold are more important than drive. I followed the math and measurements and still have four days before I glass these on, so I thought it’d be wise to run this by the experts here. Also see, pic below:

BOARD SPECS

6’2" x 19.8" x 2.75" round tail

Width at 12" up from tail: 15"

MCKEE FORMULA DATA - all numbers refer to actual trail edge (not base) unless otherwise noted

Front fin to tail end: 11 1/16"

Rear fin to tail end: 5 3/16"

Front fin to rail edge: 1"

Between rear fins: 6.5"

Between rear fins and rail edge: 3"

Between trail edge front fin and lead edge rear fin: 0.5" 

Between line-edge and front stringer point: 2 3/16" front, 11/16" rear

Front cant: 6.0 degrees

Rear cant: 2.5 degrees

FIN SPECS

Tyler Warren RTM Hexcore

( Front Fins ) HEIGHT: 4.50", BASE: 4.75", AREA: 14.98"²  Foil: flat

( Back Fins ) HEIGHT: 3.50", BASE: 3.875", AREA: 10.18"²  Foil: 80/20 

For other newbies who want to do the same, here are the resources:

http://www.mckeesurf.com/wp/wp-content/uploads/2012/11/Mckee_Quattro_Formula_Shortboards_Guns_June2012.pdf

http://www.mckeesurf.com/?page_id=273 

 

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2

Oh Boy!

3

Maybe I’m a fool. If I am I don’t care.

McKee numbers will be cloae to workable for moat modern boards. If you measure the placement of some of the most admired shapers, the fronts will often be close to Mckee tables, and the rears for quad are largely determined by the placement of the fronts. But, then, yr into placement and cant for the rears relative to what you have for the fronts, & tri/quad cants are likely to be different when ea is at its best.

For those reasons, yr better off installing Probox (whole other topic).

4

Experimented alot with quads over the last 10+ years (100’s of boards). Never make thrusters for my self anymore.  Started off doing the McKee thing.  Boards surfed much more like thrusters than quads. Didn’t have as much pivot as a thruster but was faster.  Kept experimenting looking for a set up that had quad drive, was loose of the top, easy to release fins, extremely tight turning and could surf top to bottom (something I often read that quads dont do).  Your set up looks right for a board of that length.  I would suggest moving the rear fins 1-1.5 inches closer to the rail (1.5-1.75 inches from rail), Toe all the fins to the same point off the nose.  I use an aluminum straightedge and aim for a point about 2’ or so off each side of the stringer at the tip.  Relative to the bottom countours (double concave, double between fins to spiral v to v out the tail) the front fins are at 10 degrees and the rears are at 5 degrees.  This makes for a hsb that surfs very vertically, carves and pivots quickly with fin release if you push it.  For smaller and weaker waves in the chest to overhead range I put a couple soft channels starting in front of fins out the tail.  The same set up works well at hollow powerful waves like G-land.

Hope this is of some help.

 

5

Thanks, I just wanted to be sure I got the formula right, and it sounds like I did. I’ve only been riding single fin up until now so this will be a huge jump. I like the progression you described as you tried the adjustments over time, and would like to experience the same. With that, I think I’ll start with my current numbers, see how it feels, and make changes on the next board. 

6

I’ll be sure to try Probox next time. The glass-on route was decided in another thread. Thanks though

7

For what it’s worth, when the placement  says 11 1/16" from the tail (or 5 3/16" for the rears), that’s referring to where the back side of the fin base should be.  Maybe I am mistaken, but it looks to me like you have the the rear tips of the fins at those points.

 

8

Yes, you are correct, I misplaced them. Boy am I glad I asked for help. I’ll be gluing them down any day now. Thanks a million!

9

Yes, you are correct, I misplaced them. Boy am I glad I asked for help. I’ll be gluing them down any day now. Thanks a million!

10

McKee numbers will work well with most HPSB shapes, and I know of one very high profile shaper whose fronts almost always match McKee fronts’ placement from the charts on McKee’s site (the charts from the past few years, there may be new charts, I dunno). However, McKee’s placement – for better (thruster like feel/drive) and worse (slower than some other combos, esp in small waves) – doesn’t feel like some other layouts with more railward rears, or with the spacing of more railward rears (often shorter than McKee distances).

Quads are tricky, as fin type (template, base, rake, depth, foil especially) will change the layout that works best – especially the placement of the rears – and what distances from the rail and the fronts will work best. A quarter inch can be a huge difference, the difference between slow and lacking drive and “magic.” The foil of the rears and the cant of both front and back are both critical. You will find great variation in quad placement if you measure a bunch of production boards, though you will also find some consistencies (e.g. most CI and Lost had their rears 1.75"-2" off the rail apex, last time I did a survey. Lately, and this is just kind of a random datum, both CI and Lost production boards usually show the trailing edge of the lead fins at 1 1/8" off the apex – this is a change from a few years back when they were almost always at 1 1/4" off the apex. No idea why. Main point is just that if you measure boards actually out in the world, you’ll find both consistencies and inconsistencies between layouts that definitely work. No doubt the same can be said about layouts that don’t work.

11

Rock on, and best wishes with your endeavor.

I’ve only ridden quads for the last 9 or 10 years, yet I’m still undecided on whether I like them or not, LOL.

12

I’d suggest looking into Robin Mair’s layout.

My early McKee layout experiences were like what was stated - faster than a tri, and a little looser, but not that much better turning.

The Mair layout has the rear fins almost as close to the rail as the fronts, and the fore/aft spacing is closer to an inch +/-.   Using boxes that allow adjustment has made a wold of difference for me - I use RedX, again, after losing too may fins out of 4way boxes with grub screws and the weakness in the fins seat.  

Anyway, for me, I also like the ability to discover what setup is best for my toeside and heelside.

13

Nah!  Just giving you a bad time.  Looks fine as McKee setups go.

14

All kidding aside;  This info from Hilo is right on.

15

Great, because I went with it anyway :0  Ended up using two biased 45 degree angle 6 oz strips on either side to fix them down, and 4oz running all the way both sides too. I hadn’t thought about how that would change the foiling that TrueAmes so carefully crafted, but I tried my best to taper everything off. I took it out for the maiden voyage last monday and it was fast as hell, and it didn’t pearl the way my previous board did. Now I just have to learn how to stand up on something this small. Thanks everyone for your help.

 

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