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General => The Shape Shack => Topic started by: StarboardSUPMan on January 21, 2021, 12:16:53 PM

Title: Board Thickness Effect
Post by: StarboardSUPMan on January 21, 2021, 12:16:53 PM
I am thinking about shaping another paddle board and wanted to get a better understanding of the impact that board thickness has on surfing.

My current understanding is it will impact the rails as the thicker the board the thicker the rail.  You can somewhat combat this by thinning the rails out or doing a domed deck.  But I feel like I'm missing something.

My question that I'm struggling with is 2 part.
1.  What would the difference in surfing be if you took the exact same dimension for a board (length 8', width 28", same rocker, etc) and built one 3.5" thick and another 4.5" thick?
2.  What would the difference be if you took a board 8' x 28" x 3.5" at 95 liters and you built another at 8' x 26" x 4.5 at 95 liters?  Now the board is 2" narrower but thicker to make up for it.  26" would be less stable, would it turn better, or would it be too thick?

Just looking for a better understanding on this.
Title: Re: Board Thickness Effect
Post by: StarboardSUPMan on January 22, 2021, 06:36:21 AM
I ended up buying a board that is a 8'0 x 28.25 - 95 Liter that is 3.5" thick by SurfTech.  I currently own a 8'0 x 27 - 95 liter that is 4.25" thick by Brusurf.  It will be interesting to compare them once we have swell.

I guess another example of what I'm trying to understand is a wave ski is very very thick.  Granted you are sitting down guys can pull off some pretty amazing maneuvers and these things are 8"+ thick.  Whats the limit for a SUP.  What if you went 6+" thick would it just be incredibly corky?

WaveSki Pictures;topic=18257.0;attach=26934
Title: Re: Board Thickness Effect
Post by: sflinux on January 22, 2021, 08:22:13 AM
Congrats on the new board.  With the ride report, perhaps mention any shape differences you notice with the board (i.e. tail shape, tail width, rocker, etc).
1)  The boards would have a different guild factor.  One board will sit "higher" in the water.  That board will require more force to get the rail to engage. 
2) I would think the 26" board will glide better through the water at speed.  The 28" board might have faster acceleration due to lower aspect ratio.  I agree that 26" would be less stable.  I don't consider 4.5" to be too thick.
Thinner and domed rails make the board feel more tippy.  But they also make the board feel more reactive (race car versus sedan).
Sit down/knee boarders with their low center of gravity can really leverage their weight to get a rail to sink.  SUPs have that advantage over conventional surfers because we can use the force of the paddle.
Board design is super complicated: 
Tail shape: I find pintails more stable than squash, but squash turn more aggressive.  I like pintails for big surf, squash is fun in smaller surf.
Bottom contours: The bottom contours can have a huge effect on the ride and will determine on what type of ride it is best suited for (mushy versus steep).  A convex nose with slight v would be better for small/softer surf.  Whereas single concave to double concave with strong V might be better for hollow/steep fast surf.
Rocker line: Affect how a board fits in the wave.  Flatter rocker paddles faster and accelerates faster on a wave.  Bigger rocker will make a board match the line of a steeper wave.
Fins: huge effect
Board length: longer has more swing weight
nose shape: wider is more stable, narrower easier to punch through waves, and less likely to catch on steep drops.
volume: how does the board support your weight
With all the board attributes, rail thickness is lowest on my radar.  If I had a board in mind that I wanted a certain length and width, I would tweak the rail thickness to get the desired volume.   
I would think for high-performance rail turns, the thinner the rail the better.  But similarly, the narrower the better as your foot is closer to the rail to weigh the turn, where on a wider board you would have to move your foot and probably not be able to leverage the turn as well.  And similarly with volume, the lower the volume, the easier to get rail in the water.
Title: Re: Board Thickness Effect
Post by: PonoBill on January 22, 2021, 12:27:34 PM
I think some shapers take advantage of thicker boards to fiddle with a different rocker on the rails than on the bottom. If you picture a stepped rail board where the top of the step moves from about the midpoint of thickness of the board to the top of the rail at the nose and perhaps the tail, you can see how it could have a tighter rocker on the rails than on the bottom. That takes some complex shaping, but it's what Bill Foote did (I think) on the Triton 10'4" board. It's hard to see it because the curves are a little eye-boggling, and it would take far more photographic skills than I have to get a representative picture, but that's what it looks like to me and could explain why the board turns like a 9 footer in hard turns but paddles and floats like a huge dock.
Title: Re: Board Thickness Effect
Post by: NorthJerzSurfer on January 22, 2021, 03:58:50 PM
check out the Genration boards- specifically the Wedge.   I'm riding a 8'2 x 28 x at least 4.5 (Genration doesnt list thickness) at almost 230lbs in winter gear floating above the water and 'semi' stable at 118l. which is crazy volume for an 8'2 x28

its a full on performace shape but they figured out how to make you able to stand on a surfboard.  most dramatic stepped rails i have ever seen and by far (in the middle) the thickest and it works....well!

Title: Re: Board Thickness Effect
Post by: exiled on January 22, 2021, 05:02:07 PM
check out the Genration boards- specifically the Wedge.   I'm riding a 8'2 x 28 x at least 4.5 (Genration doesnt list thickness) at almost 230lbs in winter gear floating above the water and 'semi' stable at 118l. which is crazy volume for an 8'2 x28

its a full on performace shape but they figured out how to make you able to stand on a surfboard.  most dramatic stepped rails i have ever seen and by far (in the middle) the thickest and it works....well!

They've got the 8'2 Wedge listed at a whopping 5 inches at (
Title: Re: Board Thickness Effect
Post by: Biggreen on January 22, 2021, 08:43:46 PM
Oh, I love it when I get the opportunity to add something useless to the equation 😁.

1. You’ll definitely prefer the 4.5” board.....unless you’re the same size as Kai Lenny. Float is your friend to a point. More so on a sup. As long as you had thinned out rials (dome would be better all around) that thicker board would be easier in every way. I’ll explain later.

2. I think you’re missing the point. When you reduce width you reduce outline curve. A key component to performance. That’s why you always see the really narrow boards by manufacturers being the shortest boards. They couple length with width. Not being the brightest bulb in the pack, it took me a while to realize this. I now ride wider boards, mainly to get the outline curve and 12” widths (most important IMO) I prefer.

I started building my boards early on because where I live you couldn’t even find, let alone demo anything. For a couple of years I never went out on anything over 7’8”x27”x 3.75”. Low apex rails, flat deck. Not by design but because I sucked as a board builder and that was the easiest for me.   Me, (at that time) mid late 50’s 6’1” 180 lbs, no surf background. Had a blast with no fucking clue  to what the shape, design was doing for me. I was just proud to be out there.

A few years, no little amount of bourbon, and more experience across the board and I’ve landed on what works for me and my waves. And there’s the operative thing....your waves.
Don’t forget outline curve with the way you want to ride.
And I think mid width is fairly inconsequential to your widths at 12” from each end. The mid width just completes your outline curve. Taking into account the waves you ride and the way you want to surf determines the end widths.
If you’re a stud, pointy nose, narrow tail, thin rails.
Partial stud, pointy nose, a little wider tail to offset what you’re losing up front.
Aspiring stud, more width up front, tail what fits outline curve and your mid width.

That thickness thing is kind of like the mid width thing to me. It’s so subjective to the way the board is shaped and the way the volume is distributed as to be kind of hard to pin down. These days my boards are 4.25” thick with a domed deck coming from a thin low apex rail. I know many hate a domed deck, but I think it’s a definite performance feature if you can stand it. I can see how that step deck shape could appeal to some for volume distribution and ease on knees. I often do a low apex thin rail to a flat deck for others.   Being more of a front foot surfer (sigh) and surfing mainly mushy waves, I like a little wider nose and a narrow tail. But I definitely want some outline curve, so I have to add width even though I’ve never had an issue on 25-27” wide boards.
For me, thinned out nose and tail, and thickness centered in the middle to just a little forward so as not to bog when stepping forward too catch a wave.

 Thanks Starboard for letting me beat my gums and add little to nothing of use. But I think you should home in on your 12” widths, determine the outline curve you like to suit the way you ride and the waves you surf to determine your mid width, and keep volume to a point, but keep it in the middle (or close to where you stand) both fore and aft, and starboard to port.

All the best!

Title: Re: Board Thickness Effect
Post by: surfcowboy on January 23, 2021, 08:34:18 AM
BG called out a big deal. Those Simmons shapes were stable because of the lack of template curve. Want to see it? Look at a Naish Hokua at 8’ and then a SimSUP.

Kai Lenny rode one, I rode the other, at likely similar widths at times. lol

How quickly you get to and leave 26” width is a big part of this. And yes, you can compromise with only one wide end. (Takyama Scorpion prone boards)

I don’t need that pointed nose for my waves so I can have a big stable nose and take my performance from the tail. Your mileage may vary.

But a few years ago we all established that for SUP surfing thickness should keep your rails in the water for stability, regardless of shape and size. It’s all connected.

I can ride a 24” wide SUP in surf. But it has to be longer and well under 4” thick or else I’m rolling a log like a lumberjack.
Title: Re: Board Thickness Effect
Post by: StarboardSUPMan on January 26, 2021, 06:43:26 AM
Thanks for all the info.  It makes sense it's all connected I was just stuck on one aspect of the board which really needs to be considered as a whole against the rest of the board.

This leads to new questions hope you guys don't mind.  When you talk about board curve like a L41 with not much curve vs a Naish Hokua with lots of curve.  What does that curve really do? The Naish will do better in a hollow barrelling wave where you need to match that curve, vs a L41 will do better in a flatter wave?  Is that how it works.

@Biggreen - I've heard a ton about 12" measurements.  More so from the tail but I guess the nose also makes sense.  What are the rules of thumb.  I've always heard 12" up from the tail 18"+ won't perform in turns and 18" - will perform.  I've never heard any rules of thumb about 12" back from the nose though.

@sflinux - I will post a report of the board comparison.  It makes sense that you need to consider all aspects of the board rather than focus on one.  I have a board that has very thick rails and others that have thinned out rails and I don't really notice much, but I guess I need to consider all other factors (rocker, outline, etc).
Title: Re: Board Thickness Effect
Post by: Biggreen on January 26, 2021, 05:38:35 PM
Yeah, you’ve hit it SSman. The Hokua is a more performance oriented shape and the straighter rail line L41 would help with smaller, more gutless waves. As you well know, they both have their respective strengths and weaknesses. And being a marginally mediocre surfer, I bring out the best in neither shape. For me personally, I like a shorter (sub 8’) board with a straighter rail line and my longer boards (8’5”-9’) with more outline curve. Just works better for the mostly mushy waves I get to ride.

The 12” from each end is just my personal crusade. I think too many get stuck on only the width at the middle, which to me means jack if the overall shape doesn’t fit your waves, your surfing style or goals, and the outline curve for the above. And I was guilty of that. There was a good while that I kept focusing on width at the middle not realizing I was missing the boat.

That 18” measurement is relative. I guess if you want to surf more vertically (which I only do coming down the face of the wave about to go ass over teakettle 😁) or more hollow waves, wider is more to your detriment. Starts breaking loose. But my favorite board ever under 8’ (for my waves) is 21.5” nose @12”, 27” middle, 19”@ 12” tail and 12” wide at the very tail. Pretty straight, as you can see. Fast as hell, nimble and fun. The other board I ride most is 8’10”. It’s 20”@12” nose, 28.5” middle, 17”@12” tail. Works great for me. And like Pono mentioned, it also incorporates rocker at the rail line to make the shape work, too.

The more boards I build, the more I realize I really am a long way from having a clue. Was it sflinix who suggested really looking carefully at all the shapes you come across? He’s right. Take measurements on everything you ride and zero in on what works for you.
Title: Re: Board Thickness Effect
Post by: surfcowboy on January 26, 2021, 07:19:52 PM
Yeah, sorry the “curve” I was talking about is rail line.

Hokua has a constant curve from tip to tail. L41 has a lot of curve at nose (and tail) and is straighter in the middle for a long way. More square than pointy so 12” back from the nose there’s a lot more foam to stabilize you. Same for tail. Pointy ends are less stable but better at high speed.
Title: Re: Board Thickness Effect
Post by: sflinux on January 27, 2021, 07:28:37 AM
You may enjoy listening to The SurfSimply podcast Episode 51: Profile, Outline, and Foil: (
13:30-54 min mark
They touch on bow plane and angle of the board on rail, both of which can be affected by board thickness.
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