Your famous (in my mind) airial was definately on a keel fin fish, and I am remembering dark green. It was on a right going towards the needles eye, on the inside section. I may have even been on a boogie board.... lol. I don't think I was older than 12. I remember you being pissed, since I was in your way, but I didn't care (never have and never will... lol), I just thought it was AWESOME!
A thousand thanks Mr. Gall !
Some of the best advice this old grey beard has ever had layed on him.
You bet I wrote all that good stuff down.
I would rather be someone's shot of whiskey, than everyone's cup of tea.
impressively articulated engineering/field testing approach to nextgen board design and construction,
as it is, the surfboard industry is in for a major sea change once advanced 3D printing becomes ubiquitous
a time when forward thinking shapers with established technical chops are going to really hit the gas pedal
George, predict many speeding tickets in your future...lol
Yes, Gus is quite prolific, AND creative! I locate fin dots based upon several other factors in addition to the length. I look at width, bottom contour, rocker and in the case of Paipo and other prone craft, I like to see what config has met a lot of success. Lastly, I'd need to know the intent of the rider (down-the-line racing like Laniakea, or turns like Makaha,) oh and also the shape of the fins used!
Hi Harry! Thanks for the props, and you're very welcome, it's the least I could do, that's what it's for! And best wishes to you and the family! Happy Holidays!
OH MAN that is hilarious-!!! I can't even picture you as a kid, ha ha!!! but seriously, that is dangerous to do to little kids, I don't recommend or even condone it (unless either money or good waves are at stake...) I don't remember that fish, most were dark, either black or very dark blue/purple they go faster.
Hi Matty! Very cool, if you get a chance PLEASE follow up with any developments. That is one thing that lacks on this site sometimes, those requested changes and the ACTUAL outcomes are GOLD to somebody out there... ...don't know who yet, but they're out there!
You know what? It's funny, I just realized that shaping has ALWAYS been a "subtractive" process. With the 3D Printer, "shaping" (or projecting ones' will to a goal of a shape,) is an "additive" process. Very cool. It's already happening, fins, hardware, and board/rail sections, so we wait...
"George, predict many speeding tickets in your future...lol"
Oh and fast fun ride it will be...
As posted earlier in the thread by George/PlusOneShaper:
"Don't mean to bust your chops, but because you're an Engineer I have to say something about nomenclature. (I realize you're area is Hydrauics/Fluids/Civil so maybe you can school me on this. "Cavitation" is boiling and subsequent collapse of a fluid.....
.....I think the term "Separation" is what we are talking about (true surfboard fins produce LOW pressure but nowhere near the magnitude of a viscous coupling,) in which flow becomes so low on one side of the fin, that the laminar flow actually "detaches" from the fin and turbulent, not lift-producing flow, results. Once this smooth flowing water gets ripped away from the fin, it is very hard to re-attach, unless some sort of "influencer" is used."
'Taught myself some high-speed hydrodynamics a fair while ago now and it's always bugged me whenever I walk into a surf-shop and ask the sales assistant to tell me about the new fins the shop's just got in, and they start banging on about how the fins will "cavitate" and release/slide out just when you want them to.
I've tried explaining to them that while a tow-in or big-wave surfer might get up to cavitation speeds (~50knots/93km per hour/57mph), the average surfer gets nowhere near that fast on a wave**, and if there was honest-to-god cavitation going on, you'd know about it because the imploding bubbles of steam would be eating the fins alive. The cavitation pitting would be plain for all to see.
I've largely given up on that though as you can see their eyes start to glaze over and the info going straight over their heads, so now I just grit my teeth and put up with their talk about "cavitation". Most of the time they're kids who've at best never experienced anything more advanced than high-school physics, so they can be forgiven for that.
But fair go, this is Swaylocks - a place for the propagation of the truth about surfboard theory (or at least I believe it's supposed to be) and a source of education for those who wish to learn it, so it's important that the concepts talked about here are correct.
I'm not trying to have a go at GregTate here, it's just that I've seen quite a few users in the past posting on Swaylocks about "cavitation" when in fact they mean "separation". 'Time that was put right, so points to George for striking a blow against this "cavitation" at sub-cavitational speeds misunderstanding. Spread the word folks.
And GregTate, please, if you catch me goofing up on a concept in the future, let me know about it and set me straight; I'll meekly accept as I'd much rather know the truth....... (I wonder how long I've got before that happens; probably not too long because as is usually the case, the more I learn, the more I realise I've yet to learn :) ).
**I do vaguely recollect it is actually possible to deliberately induce cavitation at lower speeds (around as low as 36 knots if memory serves), but standard off-the-shelf fins don't have those features.
Lots to ponder over - thanks again.
LIT. No offense taken. You and George are correct. My last hydraulics course work was in 1972. I just lumped it all into cavitation as short-hand for the mild to severe disruption of laminar flow. But you are correct that that is technically very incorrect.
I just didn't want to miss an opportunity for George to talk about how fins disrupt laminar flow and how fin placement can help
Personally I'm always ready to learn, although I do not always like being taught. - Winston Churchill
And another thing. It happens in 3D not just in a plane like the text books show. Lots to explore here
Yes, I posted that only because I am too comfortable with Mr. Tate, he is a sharp engineer and one heck of an athlete swimmer/surfer who has a good habit of making things happen. I too tend to "tune people out" as they invoke "the cavitation thing" in surfboard design, I just wanted to be sure Greg wasn't "one of those guys..." (I was helping, Greg!)
Greg knows more about flow and surfaces than anybody on here, he is being too humble,
some examples of Cavitation:
Okay guys, kind of a quiet evening. I want to throw this out there. One morning about 30 years ago, I was sitting through an Aerodynamics class (we had to take cross-curriculum, so if you studied Electrical Engineering, you'd take some Civil Engineering, Mechanical Engineering and Aerospace Engineering to round out your experience. There were only 4 disciplines of Engineering back then, instead of the 12 plus now.) The professor spent a good 20 minutes going over the concept of lift, like you see in those social studies movies way back then, how low pressure forms over the top surface of the wing because air must travel further than the bottom surface to get to the rear edge of the wing at the same time. He had 2 chalkboards full of bitchin' drawings and stuff, turned to us and asked, " Are there any questions?" My hand went up quickly...
Prof: "Mr. Gall?"
Me: "So, how can a plane fly upside down?"
His nice 'good morning' smile inverted, and he turned red. I could feel the vibe in the class, "ohh shit, George again..." and I admit, I was a dick back then, way worse than now.
Most planes can fly upside down. Most can do this for long periods if pressed. It may not be efficient but the plane flies...
"How does a fin REALLY work on a surfboard?"
(who wants to be in the Hot Seat now?)