great video! Kinda scientifically reinforces a lot of things we have discussed here. Round rails “engage” the wave more (convex side of the spoon in the faucet flow), thinner rails with a concave bottom and a hard edge release for a looser feel (concave side of spoon in the faucet flow). A half inch difference of tail rocker makes a big difference in the overall performance of the board, changing the entire dynamic from the nose back. Lots more and I’ll have to rewatch it several times.
I like how it was stated surfboard design is an art, refinement of design is where technology and science really have the strongest application right now.
Be fun to see those same kinda flow pressure graphics with different fins, fins alone and board with differing fins.
Really interesting.
Thanks for posting.
Isn’t altering the rocker by half an inch quite a lot? They made it sound like half an inch is nothing.
Very, very interesting. I was wondering if they did the tests with fins in the simulations or not. Also interesting was there didn’t seem to be any pressure difference in the channels other than just at the end of the channels at the tail. I would like to see the simulation with the board turning as well. And what about vee? That would be cool too.
Very nice video Brett.
What stands out most to me is that he isolated just 3 general variables – rails, rocker and planshape. I am sure there are many more variables to consider.
The number of combinations possible by changes in only one of those variables is large. By making changes to the other two variables, the number of possible combinations is huge.
Add variables beyond these 3 and the number of possible combinations increases very quickly. (My high school combinations and permutations math is a faded memory.)
And this does not include fin shape, number and placement.
Design and performance are elusive beasts to pin down.
I believe that this is a cutback or off the top turn and we’re looking back towards the curl.
That’s the way I saw it too, if that’s the case then the greatest pressure is on the inside rail and not the front outside contact line.
I see it that the greatest pressure is along the inside rail as it would be for any turn and also greater pressure towards the tail where you’re putting the pressure to pivot. You naturally unweight the side you’re turning away from.
Does it make sense that the highest pressure is at the front as they depict ? Not to me…
Actually, I can see the leading section of the inside bottom and rail generating the most pressure in a cutback – more of a keel effect.
Based on this gentleman’s automobile experience, it looks like his results are based on the outside rail moving at a (slightly) higher speed than the inside rail thus generating greater pressure where it engages the water. Or not. From a proud high school graduate, class 0f '67.
Bravo
They didnt factor in fins either, Im assuming they simplified things to make it easier for the general public to digest.
Still interesting and thought provoking though.
Just a quick one.
You can do a flow analysis with onshape and a free flow plug in forget the name of.
Its static only but it’s free.
Solidworks has a better plugin. Solidworks is free for students and… Does the rounds… But that flow plugin is expensive unfortunately.
Hopefully one kind soul who has access to it will one day he’ll out swaylockians with this one day 
Basically, my boards are good enough. I agree with just about every comment here. No consideration of the affect of fins and all of this modeling is done assuming a perfect medium (smooth, ripple free water). However, a spectacular presentation that does reinforce prior theories that have been generated through generations of surfers riding all kinds of boards making empirical observations.
The soft low rail, as depicted on the ‘‘Slater Omni’’ was the standard rail form circa mid/late 1950’s. Nothing ‘‘new’’, and well understood by some, but not all, shapers of that era. Information, at that time, was not as freely exchanged, as is commonly done now. There were no ‘‘surprises’’ (at least to me) by the results displayed in the video. Surffoils deserves a Thank You, for ferreting out that little gem of info.
Great video.
This guy knows the pitfalls of CFD, sometimes referred to as “Colors For Directors”. It can provide great insights into the flow, but the amount of data can be easily misinterpreted by not fully understanding the limitations and assumptions made while setting up the solver.
So I have respect for the scientist is this video, he correctly highlights the real value and doesn’t claim the holy grail. The visualization of the effect of soft vs hard edge is very educational, nothing that wasn’t known, but very educational to new people.
I’ve been doing CFD for a few years, including my master’s thesis. It’s very easy to generate appealing colors like the images below, but it is very hard to get valid results and apply them to improve design.
I’m doing similar things with finFoil and I’m working on making these kind of tools more accessible to fin designers, but this stuff is extremely tricky to get right.
Many multi million dollar projects have failed due to misinterpretation and lack of understanding of these kind of simulations (Colors For Directors).
But again, great video without the pseudo-scientific bullshit like is common in this industry.
This guy knows what he’s talking about, thanks for sharing!
Hans said… Many multi million dollar projects have failed due to misinterpretation and lack of understanding of these kind of simulations (Colors For Directors).
That’s what I’ve learnt,
There’s so many variables whats true for one situation is wildly inaccurate for the next.
Well said Hans.
As Brett said, lots of variables. Many potentially affecting each other.
Just my $0.02. But two of the flow video images appear to be for a board traveling perpendicular to the face of the wave (paddling and higher speed?).
Pressure lines for Trim vs. paddling and drop angles?
Seems like trim speed would be at an angle to the wave face.
I keep telling myself not to do this but, one more time: You all have to look at this from the Lord’s perspective (Lindsay, not the other guy). The diagonal line across the board is the stagnation line (high pressure where it is first displaced). At right angles to the stagnation line in the opposite direction of displacement is the wake. That would be the inside rail. What happens at the wake/hull interface? Low pressure as the water is released. Voila! QED