Anatomy and physiology of Channels.

In a typical Sways way, Id like to ask what people know about a very well known but largely unknown component of surfcraft.


Ive seen rounded ones on Greg Noll  "Da Cat" boards from the 60's, 4 and six channel versions in the 80's, from razor sharp to sublte 'Fluid Foils' ripples. They were all the go for Pipe, Mundaka and the like and were on lots of boards even in the 6 foot range, but are strangley absent from an industry thats hooked on 'reinvention of ideas past'.

 Maybe its because machines cant shape channels.

 Channels are a concentrated version of the concave bottom contour thats highly popular nowadays, and the dominance of concaves would suggest it will only be a matter of time before the distillation of concave theory results in the return of channels.

 BUT when I ask,  "what do they do" and more importantly, "HOW do they work", the best answer Ive heard is,

well, yeah, they ahh, focus and concentrate the energy ....... (awkward silence)

 Can anyone share their knowledge of How channels work ?

 And How does the shape of the channel alter the performance ?

 Channels , I guess, are only effective on steeper faces but how much water goes across the board or up the face ? What is the direction of the flow, taking into account the speed of the craft ?


 And so which shape of channel would be the most effective ?

Heres a few different  cross-sections...


Most channels have been of the rounded or angular types but what would the result be for the other shapes?


I have been shaping different shaped channels into maching shaped blanks with identical thickness, planshape etc,... and starting with an original board (the "CONTROL" board ) with a flat bottom.

   Ive found that the moment you start adding contours/channels, you are taking away from an uninterupted planing area and the board loses planing efficiency.




Nose entry.


Tail exit.


 That sounds pretty logical but you'd think that if you install a 'slot' or 'block' channel it wouldnt make much of a diff, but it does. Maybe its because the planing surfaces arent on the same plane (or synch) or because of the small loss of foam and resultant bouyancy, but the change is quite obvious.

 And because its obvious, the need to find the most efficient shape is interesting... How many people have tried other shapes ?

 In the variations Ive tried the position of the channels do provide lateral grip on steep waves that is in line with their location on the board. Forward channels require the rider to move forward to balance the lateral grip.

 And Ive been doing some channels as Continuous Depth Channels so theres no alteration of rocker curve, the channels depth is the same for its complete length.

 Anyway thats what Ive been testing, can anyone suggest their own theories, tests and results or speculation.




 A simple 'fuck off' will suffice.

A quick (and very uninformed, uneducated etc.) guess would be that channels do indeed add drag. That Drag is translated to the rider (when properly isntalled and understood), as control.


Again as an uneducated, subjective opinion - I’ve had two channeled boards - one deep 6 thruster, and a Bonzer 5. Both were my go to boards in clean, powerful waves. Outside of that - any little bit of chop seemed to ruin them (cavitation?); though the Bonzer seemed to hold up to slop better than the thruster.


Blast away, I’m really interested as to why / when they work, and why / when they don’t work.

do away with drag its a drag.

control from tail rocker. rail and edge shape, outline curves and better fins

From what I have learnt.

Shaping 6 deep channels correctly is tricky

  • The foam you take out (by adding the channels) you must put back in, (by way of shaping a strong vee through where you intend on shaping your channels) I’m No expert like “Al Byrne” (master channel shaper). It just seams logic to me.

  • Don’t  run the channels out off the tail (As this will fight turns, especially at lower speed)

*Always run a slight single concave into your channels-into vee in the channels.

…I have had some really good channel bottom boards, I find when the wave gets critical (like coming down off a tight reo in the wash on a heavy style wave-Lennox Point) the board just gives you so much stability, Which is a great feeling.

They Hold great through power turns

Yeah they hold speed great, but I feel they don’t excellerate as quick as the common shortboard (single-double concave)

They carve great and if the board is ballanced they flow out of the carve good too.

I see a lot of 6 deep channels put into standard machine cut single into double concave designs, Not allowing for the foam to be removed.
I think those boards tends to sit back on the arse end when ridden. fast? yes in steep sections but stop-start surfing over all.

As I said, I’m No expert Its just what I see and feel.

Give and take.

Its Not as simple as throwing in a groove here and one there…???
Maybe it is if you have the blank canvas to suit.

Bring back channels… with glass ons… and a polish, got to have the epic spray too.


I have posted this photo before and feel more vee is needed through the channels. But, it shows how the channels don’t go through the tail.

I didn’t really answer any of your questions… sorry


One of my best small wave boards ever has 4 channels.They aren't the hard, vertical sided channels, but rounded sides, using the edge of a rounded sanding block to shape them in. I'm guessing the board worked so well in small waves because of its width and low rocker. One think I noticed was that the channels give a little more rocker, maybe the combination was the ticket? Loose, skatey, drivey, all the things you look for in a small wave groveler...

This is a newer one, made for a friend:


It’s a little bit like asking how curves affect the bottom of a board - where and how many and what shape is going to make a lot of difference.

Channels add vertical surface to the bottom of the board - so like fins, it depends where they point, and how much cant they have.  I think this effect is the reason you see a lot of finless boards with lots of channels.  Forward drive, directional control.  Channels affect water flow across the bottom of the board.  But they don’t reach very deep, which is why they are better on glassy days than choppy ones.

They also “corrugate” the board bottom, and like a corrugated piece of cardboard as compared to a simple flat one, boards with channels (even on top of the board) will be more rigid in comparison.

Channels modify rocker - so (like concaves) their location, how wide they are, and how deep matters in terms of fore/aft curves.

Channels reduce volume - so how wide they are, how deep, and how many will affect floatation.

How do they “work” - I think its a combination of all those things, and probably others too…

I did figure ( as you guys have said)  that they would add drag by increasing the 'average'  tail rocker.

 So if you had a familiar rocker , say curve A, that you were happy with


and you added channels (red) then the overall rocker would increase (2nd image) and so slow the board.

 But what if you used a flatter rocker (3rd image) and when the channels were added they increased the curve up to curve A, so then the average rocker was less than A ? Would that make the board more appropriate for hollower waves.

 Im looking to find what size and shape of channel actually adds to a basic flat finned board design by increasing speed, hold or sex appeal and why it does what it does.

 Sure theyre throwing channels all over the finless boards but they look to be more inspirational attempts, than scientific methodology.

Im slowly coming to the conclusion that any form of channel/ reduction is less effective than any fin /addition to a board shape. And possibly thats the forte of channels.

 But maybe Ive been following whats accepted channel form and not trying enough creative design...

 Any new ideas of how to assemble a channel and what its components perform ??

I’m going to go against the grain here and say unlike concaves, one of the things channels don’t do is alter rocker to any significant degree, particularly if the channels fade to flat at the tail. I’ve always held the theory that the purpose of putting channels in is that they can give some of the benefits of concaves without changing rocker. (And they can be shaped into any bottom shape… flat, concave, convex.) Shaped into the existing rocker of a board, channels direct water flow out the tail of the board rather than over the rail, and in doing so, generate more drive and speed. They may also facilitate some ventilation and introduce some boundary layer turbulence, depending on their shape and length. I think channels work best on boards designed for small to medium surf, as they help create more hold and drive, but at speed can become tracky. To compensate for that trackiness, you can add more tail rocker, use smaller fins, narrow the tail… but all of those things effectively undo what small wave boards are designed to do - plane higher, flatter, and faster in weak or small surf. Still I think channels do provide excellent hold in steep sections, conserve speed through turns, and add drive. So I think the only real adjustment that might need to be made is to add a touch more tail rocker to keep the turning radius tight and to compensate for the lack of flex in the tail that they take away.

I think that channels alter the rocker quite a deal, but thats based on the amount of foam removed ( which might be the same or greater that a concave) and also due to the area that channels cover.


 Sure the start and end point of channels are the same but the rocker seems to be increased as the channel deepens into the tail of the board.


 But apart the current channels designs, Id like to see what else can be done to make a form of concavity more effective, something beyond the angles and rolls, that takes channels another step up.

 Id love to go fully techno and incorporate a Ferrari type air scoop or vent into a board, and have it actually work in some fantastic function,









 and maybe thats for later on...

 But for now to consider a concavity that is as effective or as functional as a fin, without attempting to replicate the fin.

 Due to its intention, a new design of channel or concave would need to be disruptive to flow, angular, anti -streamline, oblique.. even ugly.

  I can only guess how each surface and dimension of a concavity affects flow but my guess is that of the 3 dimensions to work with..... Depth is limited by the thickness of the board, but seems to increase the potential volume of affected flow.

 Width is limited because two X 9 inch wide 'clinker' channels becomes a Vee bottom, and a wide channel takes away from the original planing area and curve but wider would allow greater flow to be diverted into the concave as the water rises up the wave, a wider 'mouth', as it were.

And length is almost unlimited and seems to influence any 'drive' characteristic of a channel. But I offer that drive is not necessarily THE goal.

 But an effective function, even something new, is also possible and an equally worthy goal.

all very interesting, i like the idea of the scoop . my only offering to this thread is some mucking around i did with reverse channels

putting the v back towards the stringer instead of towards the rails. i really like the boards…seem add a lot squirt down the line. i was/still am a great fan belly channels too