Boarding School: Foils

Stu Nettle
Design Outline

In the last two instalments of Boarding School we looked at planshape and then we turned the board onto its side and checked out its rocker. For this entry we’re gonna keep the board in the same position but take note of another element - the board’s foil.

A surfboard’s foil - or its profile - is the distribution of thickness from nose to tail, and its often overlooked by surfers as they eye off the more obvious design aspects. However, a good foil is crucial for performance.

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The standard measurement for a board’s thickness is always taken around the centre of the board. Put simply, the heavier you are the thicker the board should be. If the board is too thin it will sit lower in the water, be difficult to paddle, lack speed, and it’ll bog rail. If the board is too thick it will sit high on the water, feel corky and desensitised from the wave. It will also be difficult to lay the board over and submerge the rail in the water.

There are three distinct surfboard foils, each identifies where the majority of thickness is located: nose, middle, or tail.

Boards described as having a ‘nose’ foil are boards where the majority of thickness is in the forward half of the board. Classic single fins and early twin fins are the best examples of this, though there has been a slight resurgence of forward weighted boards, albeit with more subtlety than their 1970s forebears.

More thickness under the chest will provide more buoyancy and make it easier to paddle. Down the other end of the board, a thinner tail will pierce the wave face easier and provide better hold and control at high speed. Again, think of those classic single fins with their long refined tails.

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Profile of Simon Anderson's 1977 Pipe Master's board showing nose foil

Boards described as having a ‘tail’ foil are those with the majority of thickness in the rear half of the board. Obvious examples of this are early-70s ‘S’ decks and McCoy Lazor Zaps. The extra thickness in the tail can improve your boards paddling if it helps to balance the board - a balanced board creates a more neutral planing surface. The thinner nose can feel more responsive due to the reduced swing weight - more on this later. However, if the nose is too thin then you may find it sinks.

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Early 70s 'S' deck with thickness shifted towards the tail

Note: irrespective of whether a board has a ‘nose’ or ‘tail’ foil, the thickness measurement - the dimension you find written on the board’s stringer along with its length - will rarely change. In a way it’s an incomplete measurement: it describes just one point along the board’s foil. That’s why measuring just one point can be insufficient to describe the board’s foil. It needs to be seen in its entirety.

That said, modern day performance boards place the majority of thickness in the middle of the board. The thickness then tapers out toward the nose and tail. The placement of thickness is very important for paddling and performance as well as a major factor in a surfboards ‘swing weight’.

Swing weight is regularly referred to when discussing golf clubs and tennis rackets but rarely used in surfboards. The swing weight of a tennis racket or golf club is a measurement of the resistance a tennis racquet or golf club has when being rotated through the air and can now be calculated by a machine. The swing weight of a surfboard is easily identified on longer boards but can also be felt when a surfer rides a shorter board and the reduction of surfboard in front of their foot gives a similar feel. Swing weight is not specifically limited to the distribution of thickness, it can also be altered by heavier glassing.

When Kelly Slater unveiled his Wizard Sleeve in 2009, swing weight was one of the considerations for the snub-nose design, however that thought can be traced much further back. Arguably the first attempt to address swing weight occurred during the shortboard revolution in the late-60s early-70s through the creation of ‘S’ decks. Although shapers had played with many variations of step decks on their Malibu’s, ‘S’ deck boards were created to facilitate aggressive surfing with rapid directional change. ‘S’ deck surfboards would best be described as having a tail profile with a significant reduction in the nose thickness and looking similar to a spoon.

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Kelly Slater's Wizard Sleeve reduced swing weight with its snub nose design

One of my earliest memories of radical board design occurred when I saw the boards Mark Rabbidge made for Pam Burridge at Bells Beach in the early-90s. They had step tails. Mark is an icon in the industry and follows his own design theories rather than market trends. I recently spoke to Mark about the design and he told me it evolved from the difference between men’s and women’s surfing.

At the time, he was designing boards specifically for the waves on the competition circuit such as Manly, Newquay, and Biarritz. The boards at the time were thick and less responsive for women due to their obvious physical difference, so he decided to reduce the volume through the tail in the form of a step tail. Mark told me “it was like sticking the tail of a 5’6 grom board in the back of a 6’3” x 19” x 3””.

The boards went amazing and he was shaping a lot of them for the pros as well as many custom orders. It wasn’t long until the surfing industry dropped surfboard volume en masse. The boards would be more responsive, however they earned themselves the nickname of ‘potato chips’ due to their thinness and extreme rocker.

Many years ago, I was working with James Cheal of Chilli Surfboards and he was refining the contemporary ‘W’ style shaped deck for some of Nathan Hedge’s boards. The profile of this deck would be slightly thinner around the 12-18” mark from the nose and tail which creates subtle dips along the stringer. The benefit of this profile is it reduces volume under the back foot making it more responsive while also reducing the swing weight of the board. In addition the varying thickness of the profile would enhance the flex and this will be addressed in an upcoming article.

Next up, surfboard volume.

Cory Russell
Shaper
Cory Surfboards / Stretch Boards Australia

Comments

boxright's picture
boxright's picture
boxright commented Tuesday, 29 Nov 2016 at 4:29pm

Do you have a pic of Rabbidge's step tails? He's always been a left field thinker.

cory's picture
cory's picture
cory commented Tuesday, 29 Nov 2016 at 8:04pm

Hey Boxright,
Unfortunately, I don't have one and I forgot to ask Mark for one. I agree he is a great designer and an awesome person to talk to.

Blowin's picture
Blowin's picture
Blowin commented Tuesday, 29 Nov 2016 at 8:38pm

I haven't always found an increased swingweight to be a negative.

I've enjoyed the feeling that a longer board gives as you throw vertically into the lip and the resistance provided by the boards nose allows you to rotate your torso more before the board follows you back into the wave.

But you might be better off getting Kelly's opinion ....

cory's picture
cory's picture
cory commented Tuesday, 29 Nov 2016 at 11:08pm

Hey Blowin,
I never said swing weight was a negative in fact in the right conditions it's is very much sort after quality. I also find older or heavier guys tend to like more swing weight due to the way they surf. There are negative aspects of swing weight in surfboards and that is why we are not all riding longboards... ;)

spidermonkey's picture
spidermonkey's picture
spidermonkey commented Wednesday, 30 Nov 2016 at 8:32am

Tommo vader style boards are the extreme example of reduced swing weight. And the other thing with them is a combo of relatively flat rocker and very straight rail line the entire length of board. They are a bastard to paddle tho.......

caml's picture
caml's picture
caml commented Wednesday, 30 Nov 2016 at 5:25pm

Do you have to be a better surfer to ride without swing weight ?

cory's picture
cory's picture
cory commented Thursday, 1 Dec 2016 at 10:27pm

You might be onto something there caml... the wave size and conditions would play a part as well. The next article talks about volume and the detail we can access through technology. One of the things available using computer aided design programs is it can pin point where the centre of mass is. This information can be used to do further research about swing weight.

caml's picture
caml's picture
caml commented Friday, 2 Dec 2016 at 10:24am

Yes COry , that is great , im a believer in swing weight being gauged & adjusted ,thats interesting how the Centre of mass can be measured ,You describe the thickness of a board well .
Imo ,all it is just the thickest part of a foil just like a fin has a thickest part,
Wing Foils are adjusted according to the speeds required ,
Theres a law of foil for optimum performance & its relative to the thickest bit, if more foreward for slower speed & for higher speed its more aft

Blowin's picture
Blowin's picture
Blowin commented Wednesday, 30 Nov 2016 at 8:00pm

I like it in more powerful waves.

Weak waves require as little weight as possible for me.

spidermonkey's picture
spidermonkey's picture
spidermonkey commented Wednesday, 30 Nov 2016 at 11:55pm

New craziness, Frisbee with fins!

caml's picture
caml's picture
caml commented Friday, 2 Dec 2016 at 10:16pm

Blowin that sounds reasonable a theory . I know what you mean , if surfboards were made higher technology then adjustable weights would give you more control of the performance & swing weight . A lead weight as big as a coin on the front deck half for example . Wouldn't take much to achieve actually

batfink's picture
batfink's picture
batfink commented Saturday, 4 Mar 2017 at 10:38am

"If the board is too thick it will sit high on the water, feel corky and desensitised from the wave. It will also be difficult to lay the board over and submerge the rail in the water."

Cory, I've been working on getting the right volume in my boards and have a good hold on what works for me. I'm in the older category and buy boards with more foam than guys half my age, for obvious reasons. In relation to this quote, can a board with a bit of extra foam in it be compensated for, in part, by sharper rail profiles to help submerge the rail in turns?

cory's picture
cory's picture
cory commented Sunday, 5 Mar 2017 at 9:39pm

Hey Batfink,
You are spot on... there are a lot of big brands that design boards for 75kg team riders with full or boxy rails. The problem occurs when a bigger surfer orders a bigger board they do not tune the rail. Bigger surfers need more foam under the chest or down the centre of the board and not necessarily in the rails. Cheers

batfink's picture
batfink's picture
batfink commented Wednesday, 8 Mar 2017 at 2:43pm

Thanks Cory, that's great feedback, helps to build the internal narrative of what I imagine is happening under the board.

A friend who works in the industry laments that with various models that have made their name on shorter lengths, don't get scaled up properly when ordered longer. Result is a long, thick boat!