Author Topic: "There's bubbles under my board?!" (video)  (Read 3414 times)

Wetstuff

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"There's bubbles under my board?!" (video)
« on: December 17, 2014, 02:03:55 PM »
I was expecting ..just not so many.  Protected channel, brackish flatwater ..and it's not like I was Danny Ching'ing it?



I got the idea from a neat video Piros made a year or so ago ('hope he links it).  His is a lot more informative and fun.   

Jim
Atlantis Mistress .. Blue Planet MultiTasker ..   Atlantis Venom

Glowmaster

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Re: "There's bubbles under my board?!" (video)
« Reply #1 on: December 17, 2014, 03:09:29 PM »
very, very cool.  Thanks for sharing.

Dwight (DW)

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Re: "There's bubbles under my board?!" (video)
« Reply #2 on: December 17, 2014, 04:22:33 PM »
Wet sand the bottom and try again. Might be interesting.

gorgebob

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Re: "There's bubbles under my board?!" (video)
« Reply #3 on: December 17, 2014, 04:28:51 PM »
I got to try that to see how the water exits on a race board. Interesting side wash on the start of each paddle group.
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Beasho

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Re: "There's bubbles under my board?!" (video)
« Reply #4 on: December 17, 2014, 04:51:35 PM »
Interesting stuff.  I am wrestling with ProBoxes and Cant on the fins.

Moving towards ZERO cant.  No-one can really describe whats going on hydro dynamically.  Those videos give more clues. 

Using terms like "lift" and "drive" is like saying that a car has torque and turns.  Super vague.

Cant with toe actually creates a downforce (e.g lift pulling board towards the ocean).  Keep the videos coming.

PonoBill

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Re: "There's bubbles under my board?!" (video)
« Reply #5 on: December 17, 2014, 07:06:25 PM »
The biggest problem with hydrodynamic calculations is that no one is making them for anything low speed anymore. Well, maybe a few naval architects designing container ships, but that's bout it. Now that we have computers powerful enough to model dynamic flows no one cares about it anymore. The old stuff was approximations and barely holds up to the real world.

I gathered a few gigabytes of data on fluid flow, vibration and force (flex) for paddles and then stared at it wondering what to do with the mess. Best I could do was use it empirically: This looks bad, and when I do this, there's less of it. Then again there's a reason why I never fulfilled my dream of being a physicist--my math skills are pathetic. I can barely handle integral calculus.

Hulls are a lot more complex.
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pdxmike

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Re: "There's bubbles under my board?!" (video)
« Reply #6 on: December 17, 2014, 07:19:17 PM »
I can barely handle integral calculus.
I know what you mean about calculus.  No matter how close I'd get to mastering it, I'd always find myself falling just a tiny bit short.

Beasho

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Re: "There's bubbles under my board?!" (video)
« Reply #7 on: December 17, 2014, 08:23:09 PM »
I just found this quote from ProBox Larry and it is starting to make sense why all my boxes are just ripping out:

"This is the beauty of the Standup World where fins are one of the main point of power and drive that you cannot cheat with because they are under continuous load due to the fact that your standup board rides higher on the water. Not like surfing where the board foil line and simi sinker design of the surfboard in the water makes up for the lack of relying on the fins." Larry's Facebook page

A snowboard, or a ski do not need fins because they generate enough "lift" using rocker against a harder surface with the help of an edge.  An Alaia board also turns without a fin largely relying on holding its edge and its rocker.  What we are experiencing with SUP's is the LACK of penetration because we have so much float.  Therefore the fins are being more heavily taxed to provide lateral resistance. 

Its like the early days of windsurfing when (my) finboxes were continuously ripping out until (I went with) Tuttle fin boxes fixed it all by connecting to the top and bottom of the board.

Mmmmmmm more to come!
« Last Edit: December 17, 2014, 08:24:51 PM by Beasho »

Piros

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Re: "There's bubbles under my board?!" (video)
« Reply #8 on: December 19, 2014, 06:02:18 PM »
That's a pretty cool video and really high lights the surface tension of water v friction and drag from the fin box. Nice job Jim.
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Wetstuff

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Re: "There's bubbles under my board?!" (video)
« Reply #9 on: December 20, 2014, 08:51:48 AM »
I am going to have to do it for him... here is Piros' really good video from the underside. I got some local footage, he explains what is actually happening under there and entertains better.

https://www.youtube.com/watch?v=FOThERd36-U

Jim
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