WOW
What is the role of bouyancy in a NO-paddle takeoff? (sometimes it’s good to look at the extreme cases when problem-solving)
Without paddling, buoyant forces and your (and board’s) center of gravity in relation to those forces I would think are key, at least at first…especially the horizontal buoyant component generated by the (no longer orthogonal w/ respect to gravity water surface from the) ‘rising’ wave…
JSS
My apologies Matt, I got nothing to add to WOW, but I did want to add the following to the thread.
As a matter of completeness I thought I’d just add the following two figures. They were generated using the reference I gave in the original post.
In figure 1a the water surface is roughly horizontal. I write ‘roughly’ because I used a capture program to grab the frame in the animation and my timing wasn’t exact.
As you can see the bob is floating, partially submerged, sort of the way a surfer/surfboard might be paddling around or paddling for a wave.
In figure 1b the water surface is changing, tilting in fact, the face of the on-coming wave for instance.
As you can see more of the bob is submerged. Again the same kind of thing a surfer/surfboard might experience. The amount of the bob [surfer/surfboard] submerged, to a large degree (as in not completely, there’s also drag, and motion of bob and liquid to consider) is a function of the difference in the densities between the bob [surfer/surfboard] and liquid [sea-water].
This apparent sinking, apparent vertical dropping or ‘cutting through the face’, is what I was originally referring to. Less dense surfer/surfboard systems (surfer on a surfboard), will have more of tendency to slide down the face, rather ‘cut’, denser surfer/surfboard systems, all else the same, cut more than slide.
Another Mea Culpa Moment.
Like many, I have a horrible habit of associating length with density, as in greater the length the less dense the board, which is not always the case. My apologies.
If your personal technique takes greater advantage of ‘slide’ during take-offs great, but if you prefer the ‘cut’, that’s great too. Both would appear, from the posts so far, to have their advantages, at least they have their proponents.
Surfboards that tend to ‘cut’, are of particular interest to me because the transition from displacement effects [hydrostatic] to planing effects [hydrodynamic] is much more apparent – it’s that release event that I referred to in a prior post, that characterizes the transition. But release happens to some degree with all modes of paddle-in take-offs, its just more striking for the predominately ‘cutting’ type of board.
The neat thing about the cutting event is that its very stable part of the whole event, as least for a few moments, enough for the surfer to stand up. Sometimes it’s so pronounced, that as the surfer/surfboard drop together, the surfer can take advantage of the moment and stand up almost without effort –i.e. it’s as if the board fell out from under him. The motion of the center of gravity of the surfer/surfboard doesn’t change as he stands. It really is a neat experience – I suspect most have experienced it, if not all.
Also, all this dropping, or cutting is with reference to the relative motion between surfer/surfboard and wave crest. Both crest and surfer/surfboard could both be rising, but relative to the crest the surfer/surfboard may not be rising as fast, so the surfer/surfboard’s preception is one of ‘falling’ away from the crest. A whole lot of other scenarios are possible too.
What happens after the take-off phase is another matter.
kc
That sounds pretty good coming from someone who said they were a “dunce” regarding planing dynamics.
By isolating bouyancy as a variable (remove the paddling) we might be better able to model the transition to dynamic lift,
and bouyancy’s role.
Is there still a bow wave to ride up on? What force initiates the forward progress of the board?
Let the free body diagrams begin!
This is fun.
Mike
In general, sure. But putting aside what happens after you’ve caught the wave, is that the only difference you see, or believe to be important - it’s about getting up to the right speed, and a little extra float makes that easier?
kc
That is an interesting case: the no-paddle take-off and one you rarely see nowadays on low-volume shortboards.
As Pandanus (great name , love the pandanus palm) pointed out these used to be commonplace during the era of high-volume shorties (twins and early thrusters). The technique was simple : sink the board down at the appropriate time and use the force of the boards buoyancy to propel you forward and down on to the wave face.
Try this on a low volume shorty and you will quickly see the role of buoyancy during take-offs.
Also wrt to Kevin’s theory about cutting or lifting (sorry if i have paraphrased you wrongly) it would seem reasonable to me that a board that cuts or sinks or hangs lower in the water column as the wave lifts will have more drag acting on it, will be slower to take advantage of gravity and hence slide down the face and start planing.
A more buoyant board will conversely be more able to change from the high drag situation of paddling and be able to utilise gravity to start planing.
Of course from there, once the board starts planing down the face a whole different set of forces comes into play.
Empirically speaking and working backwards from the observed facts…lower volume boards have made take-offs later.
The skill level of surfers at an elite level has risen to accomodate that demand. Lower volume boards than ever before are being ridden in hollower waves because of the performance and control advantages of this equipment.
Look no further than Pipeline for a meaningful comparison. Tom Carroll’s performance to win the Pipe Masters in '92 which at that stage blew minds with late drops and turns was probably on a 7’1 Rawson.
Nowadays the Irons Brothers and Slater are routinely taking off under the lip on 6’6"s ,6’10"s . The take-off has become harder, later, more critical on lower volume equipment but that has become the accepted norm for pro’s because of the performance advantages.
It’s interesting to note that Shane Dorian went back to riding 7’6"s at Pipe to catch the waves easier. Kalani Chapman rode the wave of the winter there a couple of years back on a 9’6" shaped by Owl.
Of course there is more to surfing than just catching a wave but it would seem a fairly clear case that higher volume boards catch waves easier than lower volume ones.
Steve
Wheres Spock to do a mind meld!!!If riding waves was a simple as a float tank then we would all be riding the same boards think of world cup syndicated boat races all the money spent on theories and applications in the final analysis it is the connection of the manchine meld with allot of luck that make it or breaks it.one day when a board reacts to the mind in a synergistic way as a complete unit than your premises may be realized.I guess that virtual reality surfing exists already ,as for me i will take a wipe out or the thrill any day and that rocker, concaves, fins templates even color could make a difference,hell it might even be the stickers.In the end the more time you spend in the water the less this idea of flotation becomes a concern.I am sure many of us have seen a surfer in the lineup that rip on the worst board you’ve seen and you shake your head in amazement!! Badges we don’t need no stink en badges!!! Lets go Surfing!! But it is an interesting subject. Aloha…
Hey Mike,
I’m a dunce in the way that I have no idea what a bow wave and riding up on it will do, or details on how it happens…
But the sliding v cutting I do get. The non-paddling ‘sliders’ on top of the water use the following to get on plane: 1. gravity pulling you down the curved wave face (the ‘slide’) 2. the fact that the wave face is accelerating upwards, so it’s like having a conveyor belt speeding up underneath you, and 3. the speed of propagation of the wave, which pulls you up the wave face to begin with, so you can begin ‘sliding’ down…
The non-paddling cutters are using not only the things the sliders do, but the horizontal component of the buoyant force plays a greater part in getting things moving than for the sliders, who are already on top (or nearer to the top) of the water. The horizontal component plays the part of the delayed ‘squirt’ out of the wave face to get you going.
The best analogy I can come up with is getting pulled up on a slalom ski with a very powerful boat (cutters) and with an underpowered boat (sliders). The boat plays the part of the wave and it’s hollowness/power. With a 400 cid V8 and low pitch prop, you almost plane out a slalom ski in what seems to be one ski length (very much the same way it appears the cutters do on really powerful waves, they just pop up and are planing, there is no real transition from displacement to plane). You almost get hauled out of the water forcefully…With the underpowered boat, you must figure out a way to get the ski to the surface by angling it gently and holding on, slowly coming to plane (sometimes for what seems like forever). The sliders on less powerful waves don’t have the time to plane up slowly on a small board, so they get their planing by using more buoyancy and paddling speed. If they want to use less volume, they have to position themselves better to be more cutter than slider, as they lose paddle power…
Basically, if the wave/boat is powerful enough, you can ‘cut’ right to plane.
I may be totally off here, having never surfed anything but mushy TX waves…I hope you can understand what I’m saying, and it makes a little sense…
JSS
Good post, lennox. And you said early on that you didn’t think you could contribute to this, you’ve proven yourself wrong…
Pipe is a great place to study takeoffs, and your examples are well-taken.
I remember well the pull-the-board down no-paddle takeoff, I even still do it because my fish has almost enough volume
to be effective at it. But in trying to isolate bouyancy as a variable, I’m referring to the other kind of no-paddle where you
just stand as the wave pitches on or over you. No forward momentum whatsoever. My question to the smart people on
this thread concerns that situation.
Mike
Really interesting post… Has design driven performance, or has performance driven design?
My theories on this matter come from my experience with a short, thick, higher volume retro fish, a modified “modern fish” with a pulled in, thinned out, notched swallow tail, with some rocker added, and the (ho-hum) rounded pin-tailed thruster. These three designs are where I draw my comparisons from. From there, I’m just trying to connect the dots. And I’ve surfed these three designs in the same conditions: weak, mushy, slow, sloping, waves… and steep, dumpy, pitching, ledgy beachbreaks where the bottom drops out as the lip jacks up. (If you surf in North Jerz, in the winter, after a Nor’easter, you know what I’m talking about.)
The retro fish, without a doubt, has more volume in the tail and less rocker than the others. It rides great in the slow stuff, paddles fastest, but simply can’t catch the bigger, more powerful and faster pitching waves. You get lip-launched more often than not. I think it’s because there’s too much volume in the tail. Too corky back there.
The modified fish, also a thruster, with some added rocker and pulled tail, has less volume in the back and less volume along the rails. It’s a bit harder to paddle, but much, much easier to catch those faster, more critical waves. It takes off well under the lip, but gets a C+ in tuberiding - not enough rocker.
The rounded pin actually has more volume in the tail than the notched out modern fish, but less than the retro fish, and also more rocker. It’s harder to get into those pitchy waves than the modern fish, but out performs the other two after the bottom turn. It get’s an A+ in tube riding.
maxmercy, the boats you use to illustrate your example ride up on their bow waves as they achieve plane.
Virtually all planing craft do this. Surfboards are no different in this respect, except for one important thing.
The surface we achieve plane on is both moving and inclined (or vertical). It also has energy.It's enough to
give you headaches.
Too many variables, as you said in a previous post. And another reason why talkng about the physics of surfing
is so much fun. (but not as much fun as doing the research, this makes me wanna go surf. I'll probably blow 10
takeoffs next time I go out thinking about all this... and yeah, I know that's one less than usual)
Mike
attempted to edit 11/17/09 to correct spacing - won't work.... sorry it's annoying to read.
Quote:
In general, sure. But putting aside what happens after you’ve caught the wave, is that the only difference you see, or believe to be important - it’s about getting up to the right speed, and a little extra float makes that easier?
kc
For me floatier boards catch waves easier since you don’t have to go as fast to get them on plane. Because they’re already on top of the water there’s less drag.
I can catch waves on potato chip boards if I take off really late and use the power of the wave, versus using paddling power. On my longboard I can use my arms to get up to speed and catch waves way before I could on the potato chip. The range of where I can catch waves from, and the types of waves I can catch goes way up.
That’s why I’ve been riding my longboard 70% of the time. I can catch waves on it in any conditions. Even though I love riding shortboards they usually stay in my car unless the waves have enough juice to make catching them pleasurable. On most days in most conditions I can catch 20 times more waves on a board with more float.
Quote:
… Has design driven performance, or has performance driven design? I think the Florida guys would know the answer to this…but for me the answer lies with the ultra low volume boards ridden by Slater and then transposed to the rest of the momentum generation and Hawaii. In that case the desire for performance came first then the design and then the skill level was raised accordingly to fit the parameters of the designs…chiefly low volume and the acceleration around the critical areas of the wave afforded by concaves. Something was lost though…the pure carve of Curren era V-bottoms and the potato chips never worked at Sunset.(still don’t) Steve
After looking at one of Webber’s “Mini fish” today it was time to come back to this thread to try to make sense of what he’s doing with the design of this board.
You really need to check one out in person to see how extreme it is.
Pulled in nose compared to a fish.
Look at the amount of nose and tail rocker. Lying it down next to an Al Merrick biscuit shows it has a lot more.
Deep double concaves.
Long raked twin fins.
Volume- thick all the way through.
Very light.
Webber knows how to make boards for top rated pros (Taj for eg) and he’s created this little Frankenstein.
It all ties in with Solosurfer’s shoulder problems as I’ve been suffering a lot of shoulder pain the last couple of years and so have been on a quest for paddleability which has led me through experimentaion in width and also length of boards.
The desire for manouvreability occassionally pushes to the fore and so the desire for paddleability combined with shorter board lengths has me searching for the right combination of all the other key elements.
The last few posts in this thread are also really interesting in view of what Kelly Slater rode at Pipe this last year.
That is an interesting board.
http://www.surfindustries.com/surfboards/webber_miniFish.php
What’s interesting here is that as extreme as it is it’s not a one off custom shape.
Buoyancy is secondary to paddle speed IMHO. The faster you can get a board going the easier it is to get the wave to pick you up.
No Worries, Rich
But isnt it because of your bouyancy that you are able to paddle fast in the first place, cos good knows i cannot keep up with a surf ski at full pace on my mal let alone a 6.0
{EDIT} opps, had to add i do agree if you can get more speed it does allow for better tranisition/setup earlier on in the peace.
I’m with what someone wrote before… Sorry forgot who.
My extreme example is my “Heavy gun” 4" thick in belly, heavy kick @ 27" from tail where it is 2" think to 1" @6" from tip. 21.5" wide to 11.75 tail.
got a clean back door head high wave on it, and did some decent turns.
I like flotation, in the belly, to a thin narrowing tail,
Like the man said… paddle speed… If I could figure out how to sit in the perfect spot I guess I coulda stuck w/low volume, but, wind, currents, shifting peaks… I’ll take all the help I can get.