Quote:
Biology doesn't make very much sense without physics. Mike
Tell that to the Bumblebee!
Quote:
Quote:Biology doesn't make very much sense without physics. MikeTell that to the Bumblebee!
The bumblebee operates at very low Reynolds numbers…
WRT thick vs thin, several trusted sources have claimed the buoyancy is noticeable. However, the fins just don’t displace enough water to make a difference. If you drank a glass of water before going surfing it would have a bigger effect.
However, it is possible the vertical lift from the rake is noticeable…and that this is the source of the perception that lift is increased with thicker fins. The fins have rake angles (for a thruster) at about 35 degrees to normal, and this should scale up super-linearly for thicker fins (a doubling of fin thickness will more than double vertical lift). I hadn’t really paid much attention to this source of vertical lift before, wondered if anyone had.
Or, alternately, if unraked thick fins provided the same benefits that raked thick fins provide…
“WRT thick vs thin, several trusted sources have claimed the buoyancy is noticeable. However, the fins just don’t displace enough water to make a difference. If you drank a glass of water before going surfing it would have a bigger effect.”
I respectfully diasagree. If you were to tape a quarter (or two or three) to the head of a golfclub, a discerning golfer ( low handicap or pro) is going to feel the difference in swingweight right away. But not if he drank the equivalent weight in a the form of a glass of water. It’s a matter of where the weight is located and the type of motion. Anything we swing around with our body, we can feel, if we’re tuned. Likewise with a surfboard. It’s being moved around under and around us, it goes up and down, we adjust our bodies for it, our legs flex, sometimes the board goes over our heads and we’re upside down. I think I could discern the extra bouyancy (which I do not like) of a surftech even if I ate a sixteen ounce ahi steak. Now that being said, if you ride cold water spots with heavy wetsuits with stiff cold legs, that may affect things. I hate that feeling so I insure I surf in warm water, fast waves on thin light bouncy boards and I can guarantee you I feel the difference in weight and bouyancy of my boards and their components. I’ve always felt the difference in foam core fins.
I want to clarify something that I meant to include in my last post. Although I’m down as liking the added bouyancy supplied from foam fins, I also said I didn’t like the feel of surftechs extra bouyancy. That may seem contradictory, but it’s not. I also should have said ‘of any I’ve tried’. There are already new thinner models out that may make a difference, but the issue could also come down to weight and where it is positioned. I am very accustomed to light poly blanks of a certain density, with their mass evenly distributed. That last point is important, because as materials and methods evolve, it appears we may be heading even more towards lighter cores or hollow cores, with more of the weight in the outer shells. That may not be a perfect solution for everyone, either feel or performance-wise. AOTBE, a certain amount of mass and weight is better in some windy hollow offshore conditions. And I don’t want extra bouyancy at Teahupoo. I’ve witnessed some strange spin-outs on surftechs on big fast famous tropical waves, unexplainable other than for the added bouyancy. Even the new parobolic stringers, which may do good things by increasing stiffness and strength, have a trade-off by shifting more mass away from the midline. Is “perimeter weighting” and it’s added stability always a desirable thing? Actually sometimes I think I’d like to try having more of the mass centered right under my feet, and a minimal amount around the perimeter. Which would turn easier, a board with one large stringer (say ten inches thick), or one with two wide (say five inches thick) perimeter stringers (adjusting to give equivalent mass) with foam in the middle? The physics guys might have a field day with this, might even have formulas to prove it’s identical, but I maintain that the feel is different.
"Biology doesn’t make very much sense without physics. Mike
Tell that to the Bumblebee!
The bumblebee operates at very low Reynolds numbers…"
Physics dictate the biology.
“Biology is the living adaptation to the physics of the planet by the chemistry of the planet.” (Me)
Reynolds numbers aren’t everything. They really don’t apply to bumble bees or jet aircraft.
My reason for including the bumble bee analogy was to illustrate the point that perception is guided by the questions.
If someone were to ask how does a bumble bee fly, they just may find they are asking the wrong question. Because,
in effect the bumble bee doesn’t fly at all, it swims.
Rapidly beating it’s wings, it creates it’s own vortex and “swims” in that. It’s probably more like a propeller action. Air is like a viscous liquid to the bumble bee.
Reynolds numbers, also, have little or no use describing jet wings. Jet wings throw leading edge vortices, which generate high amounts of lift that bely the thin wing or sharp leading edge. Supersonic and hypersonic speeds are usually required to generate these vortices.
The displacement of water by a moving fin, wake displacement, is a more decisive factor than whether the fin floats or not, and these are not related concepts. Even though the term displacement is used in both.
It’s time to explore rake and it’s connection to general overall fin dimensions. This is where it gets interesting.
Hi Mark,
I should have put my response in quotations. It was the response to a question a biology professor(Todd Newberry) gave another student when she asked why we(biology students) should take so much physics. I never forgot it even after 23 years because I like simple, direct answers to complicated questions. He did elaborate discussing the growth of trees. I have always enjoyed physics although I have no talent for it whatsoever. I think all the answers to fin and board design will be found residing in 300 million years of fish evolution and 30-50 million years of cetacean evolution. If it works, its still out there. What’s a Reynolds number? Mike
Hey Mike,
I have to agree with your statement about evolution.
I think they estimated the sharks as being around for in excess of 400 million years. I don’t think the boney fishes haven’t been around quite as long but they sure have a big head start on us and have some very sophiticated fin arrangements. I have to admit that my first fin inspirations were from the cetation family. I just keep looking at those pectoral and they kept saying to me that facilitating directional change was one of the reasons they were outlined the way they were. These days my intuition tells me not to exclude the birds Or even airplane technology from the configuration picture.
Mathematics is a human attempt to measure what happens in the world of physics and is a language to express performance in. Numeric expressions can be misleading because there is so much going in around a surfboard as it slides in along a wave face. I don’t believe written formulas are in my furture. Mine rather will be in sculpture.
For me every session is another experiment. Few surfers look toward a session this way. As a result few trace the trail of the performance edge and understand the disappearing line it leaves. Speaking of which how’s that acid swirl experiment I made for you working out?
Good Waves, Rich
P.S. Trace #3 is a quad and 95% shaped ~
It’s 8’0"x13.5"x21.0"x13.875" and I want to mention
what generous and accomplished shaper Mark Goin is.
His help during the shaping process has been immeasurably. I
recommend his work very highly. He is a true master. He’s in the shaping room every day week day and is a most accessable fellow.
Hey TD, enjoying your postings…
im curious…you seem very sensitive to your equipment…in regards to foam glassons vs plug/box systems, have you considered the effect of the plugs themselves? Meaning, the plugs not only add weight but also structurally tie the deck and bottom skins of the board…thus flex/shear movement between the two sides would be ‘different’. Seems like there would be multiple performance advantages to using glassons…but I never use them so I have no valuable feedback…I know Bert uses glassons a lot too…thoughts?
“Biology doesn’t make very much sense without physics.” (Todd Newberry)
There:-)
Mike,
The thing I like best about this thread is how it has evoked memories that have shaped lives. That in itself is a good way to lay the groundwork for exploration. Heck, I only thought of my “quote” after reading yours.
If you have ever read my packaging you know where I stand on the subject of nature and evolution. I have been sending this message for 8 years. It follows.
“The Multi-Vortex Generator tm or MVG tm was inspired by the small finlets on the Atlantic Blue Fin Tuna. These 1500 lb. fish have been documented swimming at speeds in excess of 50 mph in a medium (water) 800 times denser than air. Research suggests the finlets work as vortex generators creating thrust and contributing transverse flow across the tail fin. Similar vortex generating devices have been employed by NASA on aircraft to increase speed and air flow efficiency. Placed in front of the trailing fin of a surfboard, a MVG tm likewise contributes flow around the wide base of the fin reducing drag and increasing speed. This will loosen up the board for better directional control with increased drive through the turns. We encourage riders to experiment on their own with MVG tm”
So that is where I stand. I condensed that paragraph from its’ original 3 pages with some smart help. I’m not intending this as promotion, but I admit some may see it as that. Others, from the fundamentalist red states, may brand me a heretic. Ironically so has the surf industry.
I prefer maverick.
Reynolds number: a number characteristic of the flow of a fluid in a pipe or past an obstruction.
http://www.efunda.com/formulae/fluids/calc_reynolds.cfm
Scroll down for the equation. I can’t write it here.
But, Reynolds number has it’s limitations. As in there are two types of turbulence, controlled and chaotic. There is power in the efficiency of controlled turbulence, i.e. through vortex generators. Tornado, hurricane, typhoon, surf, sound wave, are all examples of energy moving in a vortex. Mark
Rich,
I’m interrupting, here, sorry. I just wanted to add one of the main things I have been hoping this thread will draw out is peoples intuitive nature. Great science begins with the Eureka not the other way around. Observe. You’re on it. Don’t worry about the math or formulas. If it works it works. If it doesn’t it doesn’t. Testing is valid. Surfing is more fun than formulas. And isn’t fun the basis of the whole equation?
Also, I have a book suggestion for anyone interested in the future of materials and doesn’t mind a little light science: “Hacking Matter” by Wil McCarthy. It’s worth the $16 bucks. Google it first.
Thanks Rich,
Mark
Mark, first of all, let me thank you for sparking me to further articulate my first post.
Without art there would be no science. How many times have you sketched out an idea on paper (or napkin) to help visualize a concept or design? Did cave paintings give rise to language and math? Drawings are a powerful means of universal expression and recognition.
I always had a subscription to wildlife, nature and science magazines and have learned much from rereading from cover to cover and have been interested in science related television programs and films. See “What the Bleep do we Know?” a very good film on current physics theories.
I remember an extreme slow motion film footage of the bees wing in flight. It was a paddling motion similar to a water polo or aqua ballet swimmer sculling. The wing had a forward pivot that allowed the wing to describe a “figure eight” pattern rather than a “flat” up and down paddle beating. I couldn’t find a direct link to the film and it might have been included with hummingbirds or something in that vein, but it graphically sparked a eureka mind spasm especially in the similarities of different mediums as related to scaling.
I think that the concepts and theories regarding flight membranes will become more important to surfboard and fin designs in the future as we go lighter and the water contact surfaces become more sophisticated to deal with increased speed.
http://www.howstuffworks.com/news-item223.htm
Explains the vortexes.
http://www.sciam.com/article.cfm?articleID=000DF125-5545-1C75-9B81809EC588EF21
BEST describes and details “wake capturing” and how a insect flies. (with good images to support the document)
http://www.news.cornell.edu/releases/March00/APS_Wang.hrs.html
Computer simulation.
http://faculty.washington.edu/callis/Flight/Insect_Flight_A-99.htm
Pressure sensitive paint showing pressure differentials on an airplane body.
Questions with Jim Marsden Scientific American frontiers (2001)
What feature do scientists believe was the evolutionary precursor of wings?
Marden’s response:
There are two schools of thought. One hypothesis is that wings evolved from plate-like lateral outgrowths from the thorax. There is very little evidence to support this. The other hypothesis, which I prefer, is that wings evolved from the flapping gills of crustacean-like ancestors. There is a fairly substantial body of evidence linking insects to crustaceans, and insect wings to crustacean gills.
We were watching the April 10th show and were interested in the flies with “nub” type wings. You talk of this as an evolutionary step (wings for skimming along water instead of for flying). Are there any fossils of insects with these non-flight wings (the so-called “missing link” for insect wings from rudders)? Or is this entirely theory? Thank you for your time.
Marden’s response:
I can do better than fossils. When we filmed that segment, we were studying another stonefly species in which the males have short stubby wings that they use to sail across water surfaces. This species can raise and lower its wings, but is incapable of flapping them. There are photos of this species on my web site at www.bio.psu.edu/People/Faculty/Marden/project2.html , a crude animation that runs across the top of my homepage at www.bio.psu.edu/People/Faculty/Marden , and a movie of a long-winged female at www.bio.psu.edu/People/Faculty/Marden/movies/sailing.mov . We thought that both species would be included in the Frontiers segment, but the stubby winged sailors ended up on the cutting room floor. Since then, we have found lots of other types of surface skimming, which you can see at www.bio.psu.edu/People/Faculty/Marden/PBZFig1.html and www.bio.psu.edu/People/Faculty/Marden/PNASFig2.html . One of the species that we have studied uses its wings to row along the water surface ( www.bio.psu.edu/People/Faculty/Marden/movies/rowing.mov ), and this species also has what appear to be functional gills on the ventral abdomen of the adults. There are many types of fossil insects that have short stubby wings that certainly look insufficient for flying, and which also possess what appear to be gills on their abdomen (these are illustrated in fig. 7 of our recent paper: “Surface-skimming stoneflies and mayflies: the taxonomic and mechanical diversity of two-dimensional aerodynamic locomotion.” Physiological and Biochemical Zoology 73, 751-764.) Thus, while we do plenty of speculation, we also have a good basis for doing so.
I just finished watching “Flying Free.” It was quite interesting and fun, I really enjoyed it. The segment on studying bug flight spawned some ideas: first, a question, has anyone yet figured out exactly how a bumblebee flies, defying engineering? That got me thinking, why are they so hairy? Could the black hair actually trap heat, allowing the bumblebee to aid his flight with his own thermals? The reason I got onto the bumble bee question was because I noticed the scientists were studying large wings on relatively light, aerodynamic bugs. It seems to me we would be better off studying how a non-aerodynamic relatively heavy bug flies with little wings (because it seems it would give us some great tips).
Marden’s response:
The thermal biology of bumblebees is very well known (see B. Heinrich, Bumblee Economics). The aerodynamics of insects with wingbeat kinematics similar to bumblebees has been recently described (see Dickinson et al. 1999. Science 284: 1954-1960). There are plenty of people (including the US military) who share your view that we can learn much from the aerodynamics of flying insects (see Ellington CP. 1999. "The novel aerodynamics of insect flight: applications to micro-air vehicles. Journal of Experimental Biology. 202: 3439-3448.)
Some more random quotes:
The real challenge with bees wasn’t figuring out the aerodynamics but the mechanics: specifically, how bees can move their wings so fast–roughly 200 beats per second, which is 10 or 20 times the firing rate of the nervous system. The trick apparently is that the bee’s wing muscles (thorax muscles, actually) don’t expand and contract so much as vibrate, like a rubber band. A nerve impulse comes along and twangs the muscle, much as you might pluck a guitar string, and it vibrates the wing up and down a few times until the next impulse comes along. Cecil is sliding over a few subtleties here, but nobody ever said science for the masses was pretty.
“Insects work completely different from aircraft or birds by formation and shedding of vortices each time they flap their wings,” said Anthony Colozza, an aerospace engineer with the Glenn Research Center, who coordinates entomopter work at the Ohio Aerospace Institute.
Biologists with high-speed video cameras have been able to document the oscillating motions of insect wings as they move up and down and change pitch by tilting the edges, and the complex motions are beginning to be incorporated in the design of robotic “insect” wings. However, the aerodynamics of hovering insects, such as dragonflies, is still not fully understood. Wang chose the dragonfly as “the worst case for quasi-steady state theory” as the first test of her computer simulation.
Quote:
Quote:"WRT thick vs thin, several trusted sources have claimed the buoyancy is noticeable. However, the fins just don't displace enough water to make a difference. If you drank a glass of water before going surfing it would have a bigger effect."I respectfully diasagree. If you were to tape a quarter (or two or three) to the head of a golfclub, a discerning golfer ( low handicap or pro) is going to feel the difference in swingweight right away. But not if he drank the equivalent weight in a the form of a glass of water. It’s a matter of where the weight is located and the type of motion.
I totally agree, and wonder if my point was missed.
The claim was that the buoyancy of the fins was noticeable.
I didn’t question whether the surfer could feel a difference in lift. Obviously, many surfers feel such a difference.
The question was whether the lift was all from buoyancy (on the order of an ounce or two of lift on a surfboard otherwise supporting 2400-3200 ounces of lift), or whether it came from the flow reacting to the fin leading edge. The raked front edge of the fin deflects water down. This effect will grow super-linearly with increases in thickness. When riding, the lift will come from nearly the same position as the lift vector from buoyancy.
That was the question, I never had any doubt you could discern a 1/1000th difference in lift…
It’s the center of balance if the surfboad that is altered by going from a heavy fin to light fin and it is probably this diffence that is noticeable. This is easily measureable. And it is most likely noticeable.
I’m on the “What that Bleep” mailing list. I would have thought it would have got closer to me than NYC by now. Heck Princeton is 20 miles away and Rutgers 15. Oh well.
Thanks for the links. I’ll check them later. After I finish measuring and diagramming my sump pump eject plumbing. Got to know exactly where to drill the hole in the rim joist or I’m screwed.
One glaring question hit me square in the face reading your post? Ever been hit in the head by a flying fish? Neither have I, but I know people who have and I have come close. hmmmm… I’d like to swing that idea by the tail and see if it knocks over any lamps. How small is this fin theory room anyway?
Quote:
It's the center of balance if the surfboad that is altered by going from a heavy fin to light fin and it is probably this diffence that is noticeable. This is easily measureable. And it is most likely noticeable.
The weight equation obviously changes when you talk about feeling a lighter board, instead of talking about feeling more buoyant fins. I was discussing the latter. Buoyancy is a vertical force - when surfing the whole board supports its weight and the rider’s weight in lift - 2400-3200 ounces of lift. To be able to notice more lift, you would need a few percent change - far too much to be accounted for by the decreased weight and increased volume of the fins.
At the same time, I believe the riders that say they notice more lift with these fins.
The mvg or finlets on a tuna’s back in front of the tail,rotate together much
likes Blakestahs pivoting fin.I’ve observed this on tunas from albacores to
giant bluefin tuna.Be neat for someone to try it on a surfboard.
"In Reply To
It’s the center of balance if the surfboard that is altered by going from a heavy fin to light fin and it is probably this difference that is noticeable. This is easily measurable. And it is most likely noticeable.
The weight equation obviously changes when you talk about feeling a lighter board, instead of talking about feeling more buoyant fins. I was discussing the latter. Buoyancy is a vertical force - when surfing the whole board supports its weight and the rider’s weight in lift - 2400-3200 ounces of lift. To be able to notice more lift, you would need a few percent change - far too much to be accounted for by the decreased weight and increased volume of the fins.
At the same time, I believe the riders that say they notice more lift with these fins."
Blakestah,
I believe like the bee equation we may need to look closely at our questions. Light foam filled floating fins are mainly for aerialists. Float, boyancy, lift, are not interchangeable terms. Altering the boards center of gravity and center of balance is completely differnt than when talking about the lift from a fin. WE need to be more specific about our use of the term lift. The boyancy is not what I think causes what everyone is calling “lift”…I think the correct term here is pitch. By making the tail a little heavier maybe the board will tend to nose up altering the pitch of the board. Other things we know about fins can affect the boards pitch as well. Size of fin for example.
Lets confine our use of the term lift to hydrodynamic lift, okay?
Lets ask some other questions first.
A few preliminary questions come to mind that will help support my reasoning. Answering them will help indicate how confusing this can be if we don’t do this.
1.Are you discussing single twin or thruster?
2.By lift do you mean vertical lift? Or horizontal lift as is the case when describing the pull against the inside of a turn from Thruster inner fin? Translated as holding power in a turn.
3.If vertical lift are you controlling for same length fins and just altering the thickness.
-
What about the leading edge? Is is blunt or tapered?
-
Finally rake. Is the fin more or less raked?
One additional question (for extra credit. Are all these tests on a board in motion? If so what is the difference on a boards center of balance caused by a fin between a moving board and a static board?
My hypothesis is that a big fin will suck the tail down more than an smaller fin. For example, a thicker fin will suck down more than a thin fin. So if you are concerned with tail lift at Pipe switch to a bigger fin. But if you don’t want a really longer bigger fin switch to a little thicker fin.
See what I mean? It gets interesting when we know what we are really in need of and understand the possibilities and can include them in our vocabulary and our gear.
"Post: The mvg or finlets on a tuna’s back in front of the tail,rotate together much
likes Blakestahs pivoting fin.I’ve observed this on tunas from albacores to
giant bluefin tuna.Be neat for someone to try it on a surfboard."
Jeff,
There is a link I posted earlier in this thread that leads directly to an article which is the most detailed research conducted to date on the subject of finlets on the Scombrid Mackerel(tuna). If you are interested. Or you can google Jennifer Nauen.
Simply the articulation you mention has been observed in both individual finlets and as an array. The presumption is that as the tail articulates the finlets adjust to continue to direct the flow into the tail vortex.
Surfboards don’t articulate, hence, no need to compensate. That was my reasoning behind not making articulating MVGs. Still for 8 years I have had all kinds of ideas in my head how to do this, but I don’t have the motivation. I need a good reason why this would help. And I haven’t found one yet.
It’s good you observed this and made a mental note of it. I think it looks very cool to see how they move. How about the irridescent light show they put on when you first pull them out of the water. Electric mindblowing. Can you imagine how cool it would be if we had camo like that? Actually nano fibers are already just about there. Mark
What a thread…
It seems to me that surfboards have evolved through thousands of small incremental changes, and a few extremley significant changes, echoing much of what occurs in nature. Sticking that first fin on a board might similar to mankind walking, and the creation of the thruster as talking, arguable analogy but you get my drift. With few exceptions advances in surfboard design seem to have little to do with science, and have more of an intuitive empirical nature.
One of the fundamental rules to testing in engineering is to only change one thing at a time. Tubedog, were you really feeling the difference in bouyancy of the extra lift/drag or the extra stiffness of a thicker fin at low AOA? Is it the extra bouyancy in a ST of the stiffness makeing it spin out? I’m sure Bert has some comments on creating a shape based on one set of structural charechteristics and completly changing materials.
Racing yachts go to extreme lengths to keep weight out of the ends, or the perimeter. There are huge equations (and some simple ones) that describe the effect of weight placement and natural frequencies (uh oh back to that) but basically the effect of moving any weight two feet from the center of gravity is four time that of moving it one foot. In a nutshell concentrated weight is a good thing for performance.
Think I’ll stop before I get too far off topic.
“…basically the effect of moving any weight two feet from the center of gravity is four time that of moving it one foot. In a nutshell concentrated weight is a good thing for performance.”
Simonc,
Excellent point. The effects of leverage. It’s pretty easy now to see how both buoyancy and weight can have a noticeable effect. Question comes to mind, is this effect weakened in any way (4x’s is a lot of x’s) by the fact that a surfboard is supported along the entire length?
I never claimed to have all the answers. Far from it. I, myself, am just trying to make sense out of the collected observations and data accumulated by Swaylockians. Like everyone else I’m putting this together in my mind as we go and starting to make sense of all the sources I’ve ever had.
I think as we do this we will find that there are vastly more areas of agreement than there are differences. And that the perceived differences can possibly be accounted for by looking again at and then re-evaluating the data.
This has become a search for common ground as much as anything. Perhaps more precisely it’s a search for a method.
I think starting as we did with a seemingly simple duality question, this thread has developed in a way that indicates, and perhaps we now realize, the need of and for trying to find a common vocabulary, with universal meaning, so we can completely understand each other. And not have to worry about silly misunderstandings, because of differing uses of terms. (Whew!) Once we establish that, we won’t have to ask thick vs thin? We will all know how to arrive at the answer, just plug the variables into the formula.
I think we are almost ready, Simonc, for some good hard rules and possibly even formulas. Starting with the one which I will repeat from above.
“One of the fundamental rules to testing in engineering is to only change one thing at a time.” (Simonc)
Do you, perhaps, have any other fundamental rules or definitions to offer us that could help clear up and prevent misunderstandings?
Mark