Yet another thought provoking topic brought up by our own Mr. Bill Thrailkill.
Oh, ye of little faith. The game has changed before, and it will change again.
It certainly is inconsistent with the laws of physics.
That would be a game changer for sure…
…
I watched the video.
Where is the exact point of maximum velocity?
What is the velocity of the water moving upward in the face of the wave? Does this affect the velocity of surfer/board?
Is the board moving in the same direction as the upward water flow?
Is resistance to the sufer/board forward motion minimized?
…
My limited understanding is that the GPS is in the rash vest and it is measuring kilometers per hour as speed, just like an iphone or other GPS device.
Maximum speed in those 2 examples appears to be half way through turns where the fins, one would assume, are achieving a high degree of lift
IMO max. velocity appeared to be at the top of the wave. Maximum resistance to sideways motion must be mid-turn to keep the board from side-slipping over the top of the wave. The force vectors would be pushing the board back down the face of the wave.
I wonder how accurate the gps reading is in regards to board speed. Is it a measurement of board speed, or is it a measurement of board/body movement? Not sure how you could use a gps to measure speed without the movements effecting it.
What effect does a headwind have on the velocity of an airplane?
What effect does a tailwind have on the velocity of an airplane?
Groundspeed or airspeed? Relativity?
What effect does current (water flow) have on kayak velocity when paddling up-tsream?
What effect does current (water flow) have on kayak velocity when paddling down-stream?
I believe you phrase the question(s) incorrectly.
When I walk to the toilet at the front of an aeroplane, I’m covering the ground at 500km/h + my 3 km/h (or 5 when busting, LOL)
When I ride a wave I cover the ground at ~20km/h plus/minus my meanderings on the diagonal.
If the GPS is mounted in the vest somewhere and the max velocities are (as it appears) during the tightest arc of the cutbacks, it may just be that the measuring device is momentarily being whipped thru an arc at a high velocity. If the GPS was on the nose of the board, you would probably have an even higher velocity measurement during the cutback, but what of it? The fact that Kelly jams a cutback harder than the other guys is interesting, but is that what we are thinking about when we talk about speed on a surfboard?
@ red boards, perhaps you do not understand.
Pretty sure groundspeed is higher than airspeed for an aircraft with a tailwind – speed relative to the ground vs. speed relative to the moving air, respectively.
Is water moving upward in the face of an unbroken section of a wave? Does that moving water (flow) have velocity? Is the surfboard moving with the water flow when traveling toward the crest? Is the resistance to the surfboard’s forward motion lower when moving in the direction of the water flow/movement? Is the velocity of the surfboard relative to the ground/bottom greater than its velocity relative to the moving water when traveling in the direction of the water flow – assuming a horizontal velocity vector when the surfboard reaches the top of the wave (same as the velocity vector while traveling up the face}?
Centripetal acceleration does not increase “speed.” Does the GPS device measure velocity or speed?
Wake up guys, Clueless in Kentucky is trying to get you to count the number of angels on the head of a pin. What matters is how fast you (and your board) are moving over the water, on the wave. Well over 50 years ago, Bob Shepard was measureing board speed in Hawaiian waves, using a speedometer from a speedboat. How do I know this? I was there, in the lineup, as Bob reported his speed after each wave. Speed on the drop @ Sunset, in 15 foot waves, was 24/25 MPH. Speed on the drop, @ Waimea, in 20 foot waves, was 27/28 MPH. Converted to Km/per hour, Sunset is around 39 KPH, and Waimea is around 44 KPH. So Kelly, at under 20 MPH, while interesting, is not earth shattering. As a licensed pilot since 1966, I can assure you that you are flying your fin a good part of the time, and generating speed from it. The behavior of the fin, generating additional speed on a wave, is the topic at hand. The AoA of the fin to the relative flow of water, as well as the foil of the fin, play a major part in how fast your board is. Conversion factor: 1 Km equals .62137 Miles.
Rather than trade insults Mr. T, I will clarify. Premise in the first post:
“Increasing the drag on you fin, to make the board go faster… at the molecular level…”
The principal comments and discussion have been about drag relative to the laws of physics and whether it is physcially possible to generate speed by “increasing the drag.”
Regarding the video post under discussion, speed was reported to be highest at the top of the wave, at the time of a cutback, for two of the surfers. Mick Fanning’s top speed was **39.1 kph **(24.3 mph) at the top of the wave.
I am interested in seeing your written scientic explanation – using physics – about how drag increases speed “at the molecular level.”
I’m sure you are. You’ve now edited your post, what, three times now? I AM INTERESTED IN SEEING YOU POST PHOTO’S OF THE MANY BOARDS YOU’VE BUILT, OR SHAPED. I AM INTERESTED IN SEEING PHOTO’S OF THE MANY LARGE WAVES YOU’VE RIDDEN, WHERE YOU GAINED YOUR INSIGHT AND KNOWLEDGE, OF SURFBOARD PERFORMANCE. Sadly, you’ll only be able to post photo’s of the armchair, from which you posture, and contemplate your imagined achievements in surfing. Your lack of real world surfing experience, fairly screams from your every post. Why not consult with BG Surfer, and get ‘‘his’’ take on the subject, eh?
Yes, I do make** minor grammatical revisions to** my posts (spelling, adjectives, verbs, typos). Please indicate any significant changes I have made to content/meaning of my posts in this thread. I certainly did not make the comments you have posted in bold all caps lettering.
Because I have become landlocked, does that mean I did not surf for 20 years. If you can substantiate I did not, post the documentation.
My graduate education in science is meaningless with regard to surfboard design and performance?
If you can credibly demonstrate/document that drag can increase speed, you may well be a contender for the Nobel Prize.
EDIT: If you use the quote feature you could prove my edits. Of course, there is nothing to prevent you from editing my text in the quote box. I guess on this forum it is all he/she said she/he said.
…how about yours ?
https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/robbie%20f%20w%20fish%20n%20bro.jpg
https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/ridin%20robbie.jpg
No digital cameras back when I was surfing and/or built several boards for friends and me. And 99.999% of the time there was nobody around taking pictures while I was surfing (often solo).
The only pictures I have are of a 2-ft day at St. Augustine (1990) and a 3-ft day at Malibu (1976-1979). I did not hit my surfing prime until I was 28-29 (1980-1981).
I have posted pictures of me holding my first surfboard as a teenager (1968-1969). I have a picture of me racking up 3 of my boards in the mid to late 70s. I have another picture of me with the 3 remnants of my 6-board quiver (that burned in a house fire). All but St. Augustine and the quiver remnants are Kodak Instamatic quality.
I will never likely post pictures of what I have built or am building here at Sways.
But what does that prove? There are no pictures of me when I surfed hurricane swells.
So much hostility to science at Sways.
If somebody can “prove” my science is wrong, I want to know it and will own it…
While I have the time these days, I don’t have the inclination to educate you, about how a surfboard (and fin) interact with a wave. Two of your ‘‘edits’’ were to expand the content and points you were trying to make. So cut the bullshit, eh. Twenty years surfing? It’s not enough, at the level you are at, or ever were at. And please don’t bother with your tactic of throwing out a barrage of questions, to mask your ignorance when cornered. Even if you have a legitiment question, (rarely) no one has an obligation to respond to your petulant demands. Take a look at my avatar, that’s me on a wave at Sunset Beach on a board I made, taken in 1968. You remember, the year you got your first surfboard. By that year I had probably shaped over 3,000 surfboards. Lifetime total, 8,500 plus. Which is my best conservative estimate. I suspect it may well be higher. I have years of experience, during which I paid close attention to what worked, and improved surfboard performance. That’s what I bring to the table, not a textbook, and theories.
Yes, one post on this page started to lock up repeatedly before I was finished. So I posted mid composition and finished on another computer. No BS. I do not believe I expanded after somebody commented on what I have written.
I have over 40 years of experience in the world of science, 33 years in aquatic sciences. In spite of some Sways members, I still try to pass on some insights even though it has become repetitive for me.
I am not challenging your experience as a builder, craftsman or surfer – just your background, credentials and experience with science. I would be happy to have you prove me wrong about the science of drag, waveforms, acceleration, velocity etc…
But when it comes to science, I will not accept somebody’s work for it. I have enought experience in science to know better.
I will leave any typos in this post uncorrected.