after the initial momentum created by paddling,what continues to move the board…gravity pulling the board down the incline of the wave which continues to re-create itself to a final destination,or the steep angle of the wave pushing the board in a forward motion as the wave is reaching a verticle point before collapsing. is it falling or being pushed?
Yes, all of the above, … . .and sometimes the onshore wind as well which pushes you along, . . . and sometimes the offshore wind because if it flows over the nose of the board at just the right angle you can start a hang gliding effect which propels you along, . . . and sometimes as you pump the board up and down you ‘wag’ the horizontal underwater fin surfaces up and down thus propelling the board like a swimming dolphin using your own muscular effort, . . .and sometimes a bit of mental effort which projects you a bit faster via the sheer force of will power.
(see my surfing essay, 'A wing in the water and a wing in the wind" which will be published on my site in the next day or two)
Roy
gravity accelerating you down the face
and the speed of the wave moving in towards
the beach.
The speed of the surfer is not limited in speed
to the speed of the drop-in due to face height and gravity.
Although it could be depending on how good of a surfer
you are.
A wave
the primary driving force is the flow of water underneath the board. this water movement is what propels the board (and the surfer) forward along the face of the wave.
But also sometimes the air wave that rushes up the wave in an offshore breeze
Well, when you think about it, it’s the same thing, no? The more vertical the wave ( or part of the wave) you’re on, the more power is available ( related to the sine of the angle of the wave face) . Falling or being pushed? well, are you falling or being pushed by gravity? Same thing, really.
doc…
Gravity is pulling you down, while the wave is pushing you foward - and holding you up at the same time. There are a bunch of different variables here. so…yeah.
As my professor of shaping used to say, “just gravity propelled water sleds”
Do a search for “surfboard design and construction” (I don’t know the author sorry)
There’s a PDF of it around somewhere, I used to have the link until I cleared my web cache, oops. Good vector analysis of forces involved.
“Surfboard Design and Construction” by James F. Kinstle, Natural High Express Publishing Co., Long Beach, Ca, 1975
“Is it falling or being pushed?”
You can also add, “pulled”.
The mysterious sensation of acceleration exclusive to modern surf mats, as well as certain transitional displacement hull boards.
Push, pull = Pump, Squirt
First a human…then a wave of energy in a liquid medium…peace and waves…
The sun is the source of all power.
To be surrounded by the dynamics of an ocean wave is a magical experience. Body surfing is the purest of all experiences in this realm once you add an element the guides you on the wave face many other things happen but being able to direct you’re line in this ever changing motion and adjusting to it what surfcraft attempt to do. A surfmat can adjust to the surface that it’s on and it’s rounded ribbed surface holds a line without have to go beneath the water for directional stability. It can surf in any and all wave condtions. A surfboard needs a fin or fins to keep it in tune with the waves energy and give the board is serves directional stablilty. When the fins are foiled and placed well they can add to the performance picture by driving the board and thus giving acceleration as the board changes direction.
Good Surfin’, Rich
Hello Dale,
On the subject of push pull pump squirt what propels a board I have to say this:
Have you noticed the parallel profile which my
boards have? This profile allows the boards to have a springloaded
flexibility, much like a longbow. Regular boards with a tapered profile
resist flexibility due to a truss-like structure and design. A lot has been
said over the years about flexibility but it didn’t come to much because no
one seemed to realize that the power of a flexible board has to be
harnessed. If a board flexes with an upright fin setup it achieves not much,
the upright fin just slides up and down and the power is lost. If, on the
other hand, the board drives a horizontal fin surface up and down (e.g. a
tunnel), then the power is directly transmitted into forwards motion, just
like when a dolphin wags its tail.
I built a 14’9" called the x-15 which was only 2 inches thick and used
this principle (pictures on my site). The acceleration was phenomenal, any
subtle pumping motion or chop bouncing would make the board leap forwards
like a live thing.
This is one of the two main advantages of the parallel profile and is another way of propelling the board and using wave energy more efficiently.
Roy
https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/1000819_foilboardpic13#.jpg
Hi Roy,
You have absolutely fascinating ideas… I really enjoy your craftsmanship and design! Please consider putting together some detailed text and photos for the “Resources” section? Great stuff! Welcome to Swaylocks!
You know, for all the technical arguments around here regarding fins (foils, angle of attack, etc etc etc) it’s surprising to me that THIS topic – WHAT PROPELS A BOARD – didn’t attract similar discussion. It should, if not more.
Riddle me this then – assuming that there is a wave of significant power passing underneath it, why does a bird, or a floating object such as a bit of lumber, NOT surf? And a board (or a boat) can/does?
Quote:
Riddle me this then – assuming that there is a wave of significant power passing underneath it, why does a bird, or a floating object such as a bit of lumber, NOT surf? And a board (or a boat) can/does?
How well do you surf if you did nothing (no paddling) but float on a board out in the line up?
Planning…flotation and planning are two completely different things…I could plane on a large piece of steel sheet if I was going fast enough.
Pelicans surf above the waves when the winds are offshore…the birds that don’t are just lame squares missing the boat.