Channels on a surfboards

[BWD]

Since it seems like there is some grasping and gasping here, some hints:
All strakes, keels, concaves and channels contribute to lateral and directional stability by creating force in proportion to their angle to the water flow.
For lifting strakes on vee bottom boats, this means they increase lift as well as help the boat go straight.
For channels on boards, this means they help tracking.
The nonsense about "accelerating water" reflects a truth: in case of deep concaves or channels that effectively change the rocker in the center as compare to the rails, the channel or concave fails to decelerate the water as much as would happen if the rocker were the same from rail to rail.
Etc. just think about the flow of the water along the board and how the design features affect it, it's not hard to get a grip on how designs work, beyond the mumbo jumbo.

[TomW]

Hej Plummet,
Everything is anecdotal. no one has any science.
I've noticed the boards I've made with Evo like bottoms cut through chop smoother, less slamming. They seem to float over the water when flattened out going fast on a reach and transitioning into a turn. I've found them to be really quick turning, almost squirrelly until you get used to it. Very little input needed to get them to turn.
The bottom has a 5-8mm concave thru the nose and middle, with additional double concave inside that, that fades somewhat towards tail. Then the tail has V, with channels added to double concave in tail.
They are very thin. The nose is 8mm, the center at tail 15mm, mid of board 15mm. Deck has over 10mm concave. They still have a good amount of flex.

Challenge to glass and Sand.

I set them up as quads, and I think the fin set up and spacing is vital element.
These boards are made for Northern Europe shitty windwaves and chop.

[tegirinenashi]

...in case of deep concaves or channels that effectively change the rocker in the center as compare to the rails...

This one I can buy, especially that OR kiteboards proved to be very popular. One can also argue that concave improves edging. However, you know what? It is single concave. And when board designers started to incorporate more than one, it becomes ridiculous. What are those boards, wanna-be multi-hull boats?

[rynhardt]

Cool topic!
My take on this is that any kind of bottom contours will affect the ride (obviously). Not just in terms of lift and drag, but also the board flex.
With no bottom features the plan shape of the board plays a big role.
Add channels and the plan shape becomes less relevant.
Add fins and the channels become less relevant.
Every wetted feature increases area, introduces drag, and creates lift. Fins are more efficient than channels because they are higher aspect.
But if you ride obstacles fins are not great.

[zerogee_ca]

Seems like marketing to me. What was old is new again. Some of the channels seem ridiculous to me. Do the advantages in ride and performance of a board with channels out weight the added time and complexity of designing and building a board with channels? Why are there not more boards with channels? Too hard and expensive to make??

I have been able to get the ride /perfomance I want by changing fins. Fins can make or break a good board.

My current board, a Tomo inspired board from North, has a simple rail to rail single concave with a double concave in the nose. Still riding the factory fins too. I can't believe how much fun this board is for such a square board. Never wishing it did anything better. How much more fun /better would this board be if it had channels?

Hoping to demo something in Hatteras next spring to see what they are all about. But have not had any luck the last 2 years with this.

[baxterbradford]

I won't if anyone has done some flow modelling on channels to what impact they have.

This is worth a watch where they've done flow modelling on different Firewire designs, though not specifically commenting on the effect of the channels, you can see what they are doing.
https://www.youtube.com/watch?v=ZrYt5t3qalI

[longwhitecloud]

3 things at work

Going slow on sloppy waves or just cruising
Going fast on waves while cruising
And turning

If you want to turn a wider tail (not too wide), a pointy nose(most of board out of way when u pivot - short cut off noses the same), Fin positions, fin size( large= more lift) and tail rocker are important.. more so than channels/concaves.

I don't fully understand channels that are equal depth almost the full length of the board other than for tracking and some concave like lift maybe.

Interesting stuff. I just got a v3 rocket (lost mayhem) it turns sooo well, shame it would fall apart quickly for kiting.

Good turning surfboards can have absolute shit tracking. I guess that is why boards like the Nugget with straight rails sell well, good for cruising comfortably.

[bjw]

I'm not a fan of channels. I feel its a bit of a fad in kiting. It'll probably help you get up wind. But like in surfing, not great in chop. Wakeboards are different, it's in glassy waters. I find they aren't great for top turns on a good wave. They don't slide as well or correct as well.

It's funny a mate got a custom Vanguard type board made up, then liked it and got another made. Same board, but they screwed up and made it without the channels. He finds it far and above better than the first one he made.

[tautologies]

This is worth a watch where they've done flow modelling on different Firewire designs, though not specifically commenting on the effect of the channels, you can see what they are doing.
https://www.youtube.com/watch?v=ZrYt5t3qalI

That video is a bit annoying and a bit interesting. Maybe I just need more coffee, but damn. I generally can listen to a shaper speak intuitively about how they make certain choices, but these guy talk (REALLY SLOWLY) about CFD as if they provide definitive answers. It might be a starting point, but a fairly common joke about CFD is that CFD stands for "colorful fluid dynamics". There is sooo much nonsense in the surfboard industry.

[Johnny Rotten]

I've experimented extensively with side cut out line board shapes and channels.
Vader, Stallion, Evo type boards are absolutely fantastic.
As are heavily channeled twin tip boards like the tona pop.

Also some interesting stuff here about concaves as well as underwater flow video
http://www.cambersurfboards.com/home/ld-technical/