Bottom Curves Part 1

Stu Nettle
Design Outline

In the latest instalment of Boarding School, Cory Russell flips your board upside down to check the engine room. Bottom curves effect how the board interacts with the water surface making them one of the most important aspects of design. So, what are they and how do they work?

The bottom contours of a surfboard are designed to control the way a surfboard influences the water flowing underneath it. It’s a simple concept made complicated because surfboards constantly change speed and direction in a multitude of wave conditions. Also, while the water will generally travel from nose to tail it can also move at varying degrees of diagonal as a board turns.

Back in the day, a lot of surfboard shapers had experience building boats or at least a basic understanding of boat design. These days, however, surfboards stand alone for design principles specific to how we use them and the materials they are constructed with.

Over the years various designs have been experimented with but I've tried to identify the most significant and/or those commonly found on surfboards.  The bottom contours of a surfboard are a complicated design element so I've had to break this topic up into two instalments. This week we'll decipher flat bottoms and vee bottoms.

The second instalment, coming next week, will cover concaves and channels.

bottom_curves_pt_1_image.jpg

Flat

Flat bottom surfboards are, as the name suggests, flat from rail to rail. Viewed side on there’s no difference between the centre rocker and rail rocker. Flat bottoms are completely neutral with no increase or decrease in lift and they rely on only the one rocker curve. This means there’s equal water pressure across the bottom of the board and of all the various bottom contours flat bottoms make rail to rail transitions the most difficult.

Flat bottom boards can bog at low speed and they lack control in choppy conditions or at high speed as they skim across the water surface.

Vee

A vee bottom is a convex shape which means the centre rocker is higher than the rail rocker. When the bottom of the board is facing up it looks similar to a single peak roof top. Vee bottoms allow the board to sit deeper in the water. Any weight that is applied to the top of the surfboard will first push the centre of the board deeper into the water and the resulting water pressure will make its way to the rail along the incline. A vee bottom won't create lift as the water pressure, or up thrust, is not captured by the surfboard.

Depending upon who you ask, and what mood they're in, the first vee bottom surfboard was shaped by either Bob McTavish or Midget Farelly. McTavish's board featured a deep panel vee along the rear section that, according to the Encyclopedia of Surfing, "more or less forced the board to tip over into a turning position".

McTavish was a key player in the Shortboard Revolution and vee bottoms were integral to the changes that followed. Surfers wanted to turn harder so vee bottoms became the bottom curve of choice because they transition from rail to rail easily.

Vee bottoms remained a popular choice for shapers for many years, particularly pre-1990 when boards were wider, thicker and flatter. Vee bottoms come in a variety of styles including panel, rolled, reverse, spiral, and inverse.  
Panel Vee

Panel vee is the name given to the most simplistic and common form of vee. The incline on the bottom of the board is a flat surface from the centre of the board to the rail. This type of vee is usually found in the back third of a surfboard and provides some directional stability. Also, the increased rail rocker provides more manoeuvrability.

Panel vee is a common choice for big wave boards as the vee allows the board to sit lower in the water at high speeds and it adds control.

Midget Farrelly in 1967 with a first generation vee bottom (Photo Dick Graham)

Rolled Vee

Rolled vee is when the incline on the bottom of the board is curved from the centre of the board to the rail.  The roll softens the peak of the vee and provides more forgiveness. This type of vee is common in classic malibu designs and is often combined with a soft bottom rail which adds drag as well as lateral drift.

Directional change using a rolled vee bottom is slower but somewhat smoother than panel vee.

Rob Walters with a rolled vee Wilderness almost certainly shaped by Chris Brock (Photo Jeremy Walters)

Spiral Vee

The name spiral vee is a little misleading as it is not just vee but a mix of concave as well. A spiral vee bottom begins as a subtle vee under the front foot which increases in depth as it moves toward the tail.  A double concave is placed within the vee and also increases in depth as it moves toward the tail.

The double concave provides the board with lift as the increased curve in the rail rocker provides release. Like many subtle design breakthroughs it's unclear who first came up with spiral vee, though Dick Brewer and Terry Fitzgerald both used it with dramatic results on their pintail pocket rockets from the early-70s. Either could lay claim to being the inventor.

Reverse Vee

Back in 1991 Maurice Cole received a container of pre-shapes that had been incorrectly packed and had ¾” more rocker in the nose and tail than expected. Trying to rectify the problem, Maurice inadvertently placed vee under the front foot and flat between the fins - the opposite of what was then considered normal.

The success of Reverse Vee or EEV (VEE spelt backwards) is due to the increased centre rocker balanced with a straighter rail rocker. This combination creates a highly manoeuvrable and responsive board down the line whilst the straighter rail rocker provides speed and drive through turns. The vee under the front foot allows the surfer to go from rail to rail with ease and the flat bottom between the fins provided a stable surface to push against as the water released off the increased tail rocker of the board.

Maurice Cole and Tom Curren with an original reverse vee from 1991

*****

Vee bottoms on surfboards were a great addition to early surfboard designs due to the considerable width of surfboards then used. A vee bottom can make a board feel slightly narrower due to its effortless transition from rail to rail and would allow a surfer to fly down the line.

As surfers demanded more of their equipment the vee bottom became a limiting factor.  Vee bottoms lose speed through and they also tend to drift in turns rather than bite like a concave does.

By the end of the 80’s surfboard designers would begin to push the limits of design as surfers demanded to turn sharper and generate more speed on smaller, thinner equipment. There have been many shapers explore various forms of concave in surfboards going back to Bob Simmons in the late 40’s, however they did not become standard until the early nineties.

In the next instalment we will discuss concaves and channels.

Cory Russell
Shaper
Cory Surfboards / Stretch Boards Australia

Wanna read past articles of the Boarding School?
Outline
Rocker
Foil

Comments

batfink's picture
batfink's picture
batfink commented Saturday, 4 Mar 2017 at 10:33am

Thanks for these articles Cory. Had a pretty busy end to last year and missed these but have gone back through the series. I've been on quite a learning curve about design and effects over the last few years, after 25 years of surfing and thinking I had an idea. Soooo complex. To many facets, chaos theory.

But I haven't got rid of a board for years without first working out what it was about it that didn't feel right. And the boards that I really loved I took note of the various attributes for future reference.

Most of all though, I have learned to buy boards for the conditions I am mostly riding.

linez's picture
linez's picture
linez commented Saturday, 4 Mar 2017 at 10:58am

Love these articles

Spuddups's picture
Spuddups's picture
Spuddups commented Saturday, 4 Mar 2017 at 1:01pm

Flat bottoms. Possibly the most overlooked design in surfboards. Worth a try if you're looking for something a bit different. There's a lot of people out there who will tell you how they're supposed to go, but I very much doubt any of these people have actually ridden a modern shape with a flat bottom.

udo's picture
udo's picture
udo commented Saturday, 4 Mar 2017 at 1:23pm

Who actually makes a modern shape with a flat bottom ?

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Saturday, 4 Mar 2017 at 1:38pm

First board was a flat bottom single, what Cory says about them is largely true. It was fast though. Wayne Lynch used flat bottoms a bit in the 70's?

Also with regard to vee, did not Wally Froiseth & his Hawaiian crew shape some form of panel vee into the tails of their finless boards pre 1940s? He mentioned having a 'calculated drag' which I interpret as smoothing the centre 'spine' of the vee to reduce instability generating turbulence.

stunet's picture
stunet's picture
stunet commented Monday, 6 Mar 2017 at 10:22am

He did indeed! His Hot Curls from the 30s featured the classic narrow tails - which I thought was the defining feature of the design - however they also have panel vees carved into the last couple of feet.

FWIW I'm adding the historical 'colour' to these articles and Cory the technical advice.

Guess what I'm saying is it's my fuck up not Cory's...

Though in my (quickly thought up) defence, the concept of Froseith's vee was to provide control before the advent of fins. Vee, as used by Farrelly and McTavish, was primarily for manoureability.

cory's picture
cory's picture
cory commented Sunday, 5 Mar 2017 at 9:29pm

Thanks for the kind words and support guys! Surfboard design is a complicated area and I do not profess to be an expert but I do try and keep it simple. Flat bottoms are definitely a viable option but the rocker has to be perfect. I did not specifically identify who were the first to use vee bottoms on surfboards but I wanted to stress their importance during the shortboard revolution for Bob McTavish. Cheers

dewhurst's picture
dewhurst's picture
dewhurst commented Monday, 6 Mar 2017 at 10:32am

I've had a lot of fish over the years and all the best ones were flat bottom. I dont know if that's coincidence or not (though they all came from the same shaper) but whenever I get one now I order a flat bottom.

udo's picture
udo's picture
udo commented Monday, 6 Mar 2017 at 11:11am

Cory can you give us a bit more on the flat bottoms and rocker they need.

cory's picture
cory's picture
cory commented Wednesday, 8 Mar 2017 at 11:45am

Hey Udo,
Sorry for the delay... As previously stated flat bottoms maintain the same resistance from rail to rail on the bottom of the board. This creates a feeling of more resistance as there is no path for the water to take that would provide less resistance as with vee or convcave. This means that the only curved surface in which the water can release is in the boards rocker from nose to tail. The best rocker for a flat bottom performance board would be to focus the curviest part of the rocker between the surfer's feet with a good amount of lift out of the tail. The rocker is less critical in fish type boards as the flat bottom provides more resistance from a smaller board but also these boards are often ridden flatter on a wave and therefore using the plan shape. In my opinion flat bottoms are like only having one or two gears in a car. Cheers

Spuddups's picture
Spuddups's picture
Spuddups commented Monday, 6 Mar 2017 at 3:33pm

To my mind the importance of concaves, vee bottoms and the like is somewhat overstated. In the past I've made identical boards, one with a concave and one with a flat bottom, and basically I haven't been able to tell the difference. Kelly Slater probably would, but I reckon the average surfer wouldn't.
Now I just make all my boards with flat bottom, including my guns, fishes, shortboards, longboards, whatever. They all go fine, and the people that ride them seem to think so.
Also from my experience the rocker (in relation to a flat bottom) doesn't really matter. So long as the rocker in the blank is half decent the board will go okay. I just tweak the nose and tail a little bit.
I'm not saying I've found some magical answer to surfboard design, only that a lot of the received wisdom we rely on is just followed because that's what we've always done.

There is no real mystery to making a board that goes well for the average surfer. So long as it has enough foam to be able to be paddled, is short enough so you can turn it, and has a decent rocker so you're not pushing water then it'll go well. Making boards for pro surfers is another thing as they really can tell the difference and require very specific tweaks to the design. But just remember, the pro surfers are on a completely different level to the rest of us and just because they ride a shape that goes well, it does't mean you're gonna rip on it, or for that matter notice the subtitles of it's design. May as well keep it simple.

cory's picture
cory's picture
cory commented Wednesday, 8 Mar 2017 at 11:56am

Hey Spuddups,
Stoked to hear of your experiences. The fact is what you say about about average surfers not recognising the differences in boards is simply not true. Surfboard design is all about the bouyancy and fluid dynamics which dictates the performance of a board in relation to the person using it. I prefer to use the words 'resistance' and 'release' when talking to my customers. If the board is responding to quickly we need to add resistance, if the board is not responding quickly enough then we need to add more release. It is how we do that which makes talking to your shaper so important. Cheers

Spuddups's picture
Spuddups's picture
Spuddups commented Wednesday, 8 Mar 2017 at 6:01pm

Hi Cory,
First of all let me say that I really enjoyed your article. I hope I didn't come across as a bit of a troll. That was not my intention. I must declare that I'm a bit of a flat bottom fan boy; every shaper has to have some aspect of design that they're passionate about!
It's funny, the more surfboards I make, the more I realise how little I know about how they work. My theory is to strip things back to the basics, get a better understanding of these and move forward from there.

A big problem with trying to understand surfboard design is that so much of it is based on raw opinion rather than science. Consider this experiment:
A subject is presented with two surfboards. They look identical, but they either have a single difference in design or they don't. The subject may be told that the boards are identical (when they're not), told they're different (when they're not), told they're identical (when they are), or told they're different (when they are). The subject rides the boards and is questioned on their performance. Neither the subject nor the person handing them the boards know the differences. (A double blind experiment) Ideally we would carry this out at Kelly Slater's surf ranch to control for variations in wave quality. Perform this experiment with 50 to 100 subjects of varying ages, abilities and size. We're still asking an opinion but we have controlled for the most unreliable aspects. We can mostly control for confirmation bias and such like. This way we can accurately figure out what (if any) differences various design features make.

Obviously an experiment like this would be very expensive to run, which is probably why nobody (as far as I know) has done it yet. So we just have to rely on the most unreliable and lowest form of scientific evidence; eyewitness testimony. Fortunately, by sheer weight of public opinion we have come up with surfboards that go a lot better than surfboards did fifty years ago, but what really makes a difference? Do we really know? It is my opinion, that if an experiment as I outlined was carried out, that the results would be surprising, groundbreaking and embarrassing in equal measures.

cory's picture
cory's picture
cory commented Wednesday, 8 Mar 2017 at 6:45pm

Hey Spuddups,
No I didn't think you were an internet troll. I understand what you are saying and if we were talking about tails shapes I may agree with you. i have been shaping boards for 25+ years and shaped around 10,000 boards and the majority of my work is custom orders. It is that feedback that I rely on and I deal with everybody from beginner level through to CT surfers. The fact is some people like the way a particular design aspect may work for them such as you and 'flat bottoms' but I am confident that the experiment you speak of would only confirm what I already know. I know many of us shapers suffer from OCD and like myself refine their designs in millimetres. Whilst this is important the overall flow of a curve is equally important and the fact that the glasser and sander affect the design during their work on the board. Personally I love the challenge and I only encourage you to keep shaping and enjoy the stoke! Cheers

Spuddups's picture
Spuddups's picture
Spuddups commented Wednesday, 8 Mar 2017 at 6:54pm

Thanks Cory, something for me to think about for sure. I think I might need to reconsider my position!
I'm looking forward to your next article. Keep up the good work!

Cheers.

cory's picture
cory's picture
cory commented Wednesday, 8 Mar 2017 at 7:25pm

Hey Spuddups,
That's the thing about surfboard design it all about how a single design element is used in conjunction with other design elements. Make no mistake I am always learning and happy to be proven wrong. Thanks for the feedback on the articles and I hope I didn't come off as a dickhead! ;p

Spuddups's picture
Spuddups's picture
Spuddups commented Friday, 10 Mar 2017 at 5:18pm

Not at all Cory. That was a very civil and productive discussion. I'm going to put a concave into my next board to see how it goes!

cory's picture
cory's picture
cory commented Friday, 10 Mar 2017 at 8:30pm

Nice! Are you going to keep your current rocker line as the rocker with the curvier rail line (due to concave) or keep your current rail rocker line and flatten your rocker (due to concave)?

Spuddups's picture
Spuddups's picture
Spuddups commented Saturday, 11 Mar 2017 at 9:17am

I want to make a board for solid surf on my forehand. Probably a 6'2" quad with a fairly rounded tail. I really like the feel of quads on my forehand. It's still thrusters for me on my backhand mostly.
I reckon I'll keep the rail line the same as usual and flatten the rocker with the concave. I might lift the tail slightly to compensate though. There's a guy round here who almost exclusively makes quads so I might check out one of his boards and see how he approaches things re concaves. Hopefully I can make something half decent!

Island Bay's picture
Island Bay's picture
Island Bay commented Saturday, 11 Mar 2017 at 9:55am

I have a few you can have a close look at, too.

Spuddups's picture
Spuddups's picture
Spuddups commented Sunday, 12 Mar 2017 at 2:23pm

Hey Island Bay, that bonzer you were riding the other day just about made my brain explode. I really have to get out more!
I started shaping my 6'2" today. I took it out of an old 7'0" I had lying round. Unfortunately I didn't have enough thickness to squeeze in a concave, so I guess I dropped my nuts on that one. I'll have another crack at it next week when I shape basically the same board for Chris. I'll have no excuses RE concave on that one as it'll be from a nice new blank. It'll be interesting to compare the two boards when I'm finished.

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:13pm

as

x

cory's picture
cory's picture
cory commented Saturday, 11 Mar 2017 at 7:00am

Hey MC,
So are you saying buoyancy is not a factor in surfboard design? I would suggest you try to reduce the buoyancy of a tow board by reducing the thickness and glassing it heavier. Having worked with you I know that paddling and catching waves is a factor you are conscious of. If you can't catch waves there is not much surfing that is going to happen. ;)

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:14pm

great stuff

x

cory's picture
cory's picture
cory commented Saturday, 11 Mar 2017 at 11:22am

Hey Maurice,
I contacted you to contribute to this article but you refused. Therefore I had to rely on the information you have on your website and the interview you did with Swellnet sometime ago. It seems that you would rather be critical of others rather than contribute positively. Happy to read your explanation. Cheers :)

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:14pm

I am sharkman

x

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:15pm

I am

x

cory's picture
cory's picture
cory commented Saturday, 11 Mar 2017 at 2:30pm

Why is it that you don't want people to know who you are?

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:16pm

carry on!

x

cory's picture
cory's picture
cory commented Saturday, 11 Mar 2017 at 5:19pm

Maurice,
You make these comments claiming everybody is wrong, there design theories are not true, etc but you never state why or share your expertise? I apply my design theory to my customers boards and receive excellent feedback. I do not claim to know everything about shaping and always want to learn more from those smarter than myself.

cory's picture
cory's picture
cory commented Saturday, 11 Mar 2017 at 11:14am

Hey Maurice,
If you don't think that buoyancy and volume are a factor in tow boards then go and make one out of concrete or make one 3" thick. Love to see that... :o

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:17pm

fluid design is volume?

x

cory's picture
cory's picture
cory commented Saturday, 11 Mar 2017 at 2:29pm

It must be a slow day in the world of Maurice? I have written an upcoming article on Volune, you should read it. You still haven't shared the truth about reverse vee or pointed out which parts were factually incorrect. I am sure the public would like to hear it from you.

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:18pm

I get tired of reading design

x

cory's picture
cory's picture
cory commented Saturday, 11 Mar 2017 at 5:23pm

Maurice,
You are the one trying to stir the pot and put rubbish my deign theories yet you never provide yours for scrutiny. What are these alternative facts you speak of? I think you have been in America too long and starting to sound like Donald?

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:19pm

good luck!

x

cory's picture
cory's picture
cory commented Sunday, 12 Mar 2017 at 6:23am

This is your eighth post claiming I am wrong yet you have provided no evidence, information, alternative facts or how you apply design principles to you boards. I have written an article explaining my view and put my name to it. I am happy to talk about design but this bickering is childish. Again, I encourage you to provide the facts...

sharkman's picture
sharkman's picture
sharkman commented Sunday, 12 Mar 2017 at 5:20pm

OK Cory sorry just been stirring , you are right

x

cory's picture
cory's picture
cory commented Thursday, 16 Mar 2017 at 3:31pm

Hey MC,
No need for apologies, I am not that precious. I know how passionate you are about design and I fully respect you for all your years of devotion. I do question your integrity after seeing you have deleted your previous posts. It is for those reasons and the fact that I have known you for many years that make me aware of your antics. I enjoy the exchange of ideas as well as challenging them. As you know nobody is 100% right or wrong when it comes to surfboard design. If there was we would not see the evolution of surfboard design over the last several decades. I would love it if you shared your experiences and knowledge on here rather than trying to hijack yet another forum.

Waterboy's picture
Waterboy's picture
Waterboy commented Sunday, 12 Mar 2017 at 10:10am

Hey Sharkman,
I suggest you work on your own theories, Dane didn't think much of your board for Stab in the dark.

Dane Reynolds Felt "Out Of Control" On Maurice Cole's Speed-Focused Board. “It felt pretty weird," said our test rider. "It really gripped to the face of the wave and was kind of clumsy. Like, there was a delayed reaction when I set it on rail. I imagine it’s made for clean, down the line pointbreaks – like Bells or something. It’s definitely fast. I just didn’t feel very comfortable on it. I felt out of control… but I did land an air.”

batfink's picture
batfink's picture
batfink commented Wednesday, 8 Mar 2017 at 2:32pm

My most recent purchase has a wide-ish but not deep swallowtail, and the last 6 inches or so has an increased rocker and the most pronounced vee that I have felt on a modern board.

Early experiences are very good, very fast and goes where I point it, very responsive. Loving what it has done so far.

Tarzan71's picture
Tarzan71's picture
Tarzan71 commented Sunday, 12 Mar 2017 at 3:58pm

bahaa, Sharkman " Maurice" man of mystery indeed

Clam's picture
Clam's picture
Clam commented Thursday, 16 Mar 2017 at 10:23pm

missed that edit .

Cory thats an excellent article i learnt something . Great descriptions !