fast

[Flexman]

.

[john -]

Lowrider

consider me the "Torquay connection"

Im there again sat am and will pop in for another squizz and/or the phone number

dorje

ps id be interested but ive got my heart set on a newie - the dream board!

[Bryan Jackson]

Roy Stewart wrote:

“In order to discuss the speed potential of a surfboard one must take into account the weight of the rider. Surfboards are propelled…by gravitational potential energy, which is directly proportional to the mass of board and rider combined. Thus any given board and rider combination will have a thrust dependent upon its mass.”

Roy, are you suggesting that heavier board and/or rider will go faster than a lighter board/rider merely because they are heavier? If so, then please forgive my ignorance, but I thought this rather mistaken notion was dispensed with by Galilei Galileo several centuries ago!

A heavier board rider will not go any faster than a lighter board/rider. True, they have a greater amount of gravitational energy available to them, but this is entirely counterbalanced by their greater I-N-E-R-T-I-A! (The heavier board/rider will, however, have greater momentum, and this will help them maintain their speed through turns, chop, bumps, etc.)

In addition, pumping will NOT ALWAYS increase the speed of a board and rider. For some board designs this may be true (e.g., thrusters, single fin pintails) in certain situations. For other boards it is not (e.g., fishes, flex spoons).

True, pumping “drives the board via muscular effort” but in what direction? Answer: Side to side!

Let’s take a look at pumping action on a skateboard. A skateboard transfers the rider’s side to side pumping action into forward movement, but remember a skateboard is operating upon a static medium. The skateboard has to be able to flex and change shape (e.g., the deck and the trucks) in order to translate the rider’s side to side pumping into forward momentum. (Try pumping a skateboard with a very stiff deck and tight trucks. Now try it with a skateboard with a “loose” set up. The difference will be readily apparent.)

Surfboards do not exhibit anywhere near the same degree of flexure/shape changing ability as does a skateboard. As we all know, a surfboard is operating in a fluid medium. The board flexes only to a very minor degree, but the wave can flex to a maximum degree (i.e., the water is displaced). A looser board will be easier to pump, but will not hold as well on critical, steep faces (in other words, the fastest part of the wave).

A surfboard is constantly being lifted up by and then traveling down the face of the wave. That where it’s main source of propulsion - gravity - comes from, not pumping. Thus, on a steep wave face, no pumping action is needed to attain maximum speed down the face of the wave (in fact, in this situation pumping will be counterproductive!).

Pumping is mainly utilized by surfers to generate speed on slower waves. (When comparing the speed of standup and kneeboards, I am discussing them in the context of quality, steep, fast waves, not slower, mush burger, type waves.)

Does a “surfboard designed for kneeling…have a better thrust/drag ratio than a surfboard designed for standing“? To demonstrate that it would be necessary to subject them to water tank tests.

Although it is true that, as Mr. Hart says, “kneeboard designs do not provide greater thrust, because gravitational potential energy (the main source of thrust) is dependent upon mass, not the posture of the rider“, his claim that “(it) is also doubtful that kneeboard design necessarily entails less drag per unit of mass than other board designs” may or may not be correct.

It is entirely possible that kneeboard designs may have either a greater Terminal Velocity or be able to approach their Terminal Velocity sooner/to a greater extent than surfboards. They might, for example, produce less drag because of less rail in the water and a reduced wetted surface area. (Once again, water tank tests would be necessary to prove/disprove this thesis.)

As Hart states, a “compact posture means less wind resistance“ and this definitely gives kneelos a slight advantage. Although true that “standup surfers also adopt compact postures”, kneelos have the advantage of ALWAYS being in a compact posture, not just “when necessary”. (Interesting enough, lowered wind resistance is one of the advantages touted by inflatable mat surfers.)

Kneelos have other advantages over standups which make them a bit faster: Lower center of gravity (more power in turn which helps generate speed). Quicker take-offs/getting tucked into a riding posture. Easier to follow/stay in the power spot of the wave (how many times have you seen a standup forced out of a tucked in position in the sweet spot of the wave that a kneelo could easily hold?).

Finally, in the subjective category, kneeboarding seems faster because we are closer to the surface of the wave.

[john -]

I might be totally off track here - but im just looking at things from different angles - does a maxi yacht move faster than a smaller craft due to amount of sail or hull size or both - im thinking in terms of board sizes and weight - and in terms of yachts... relative sail to hull size

maybe this has co correlation to this discussion but ...you never know!


dorje

[willli]

phew.. I have a headache
concerning weight: consider the pinewood derby run by the Boy Scouts. Inclined plane just like a wave.. but one thing closely regulated is weight, heavier being an advantage. This is mostly a friction thing but you have to consider that on a wave that is moving forward the massive surfer and the lighter surfer are not equal. The heavier guy packs more "force" (F=MA). "A" is constant, ie. the wave and gravity are constant and =A, so simplified (they have identical equipment and ability) the only variable is M, mass. Easy to see when the heavy guy throws his first turn he's gonna rock the house, and the friction from his turn (surfboards are almost always turning; if you have a rail set you're turning) is gonna have far less impact on his speed. The guy is gonna be throwing buckets, which isn't a good thing for simple speed runs but gets enough attention to clear his path of dropins on his next wave.
Kneeboards are so totally "front footed" its like driving a car with the gas pedal stuck. We are by design almost always in trim for speed (thanks Bud, Hart, Romo, Eric, Dave ect).

[DrStrange]

re:pumping to generate speed--

may be true (e.g., thrusters, single fin pintails)

For other boards it is not (e.g., fishes, flex spoons).

The skateboard has to be able to flex and change shape (e.g., the deck and the trucks) in order to translate the rider’s side to side pumping into forward momentum.

Velo flexed like a skateboard i.e. deck and truck (fin) and was single fin though not a pintail. Could GG generate speed by pumping turns? You betcha. More complexity and ambiguity[/quote]

[john -]

Lowrider

bast@#$d wont sell - the're very nice spoons in great condition - i changed my mind about possibly buying one after checking them out proper like

interesting to this thread and the thoughts of BJ - The chap said his mate rode one at 6 ft bells and had to body board it as he was going too FAST to get to his knees - bloody stand up surfers....what a waste for them to have spoons....no late drop technique and experience....another place in torquay might have a spoon he thought...i will check it out at some time soon

dorje

[lowrider]

dorje,
thanks for trying.

I missed out on a Hayden spoon here about 2 weeks ago...
they're like the holy grail of spoons; Greenough built a few in the Hayden factory on the Sunshine Coast in the late 60's; it was like $220.
I was a bit slow off the mark & been lining up to kick myself up the bum ever since.

Grab one if you can, they are a great piece of surfing history; look good hanging on the wall if nothing else... and a great conversation piece.

I haven't ever ridden one. A mate had one in the 70's but I was never tempted to try it; this was South Australia, mainly the mid-south coast
and not enough grunt to get one really moving. I could ride rings around him on my scoop-deck single fin fish ( & catch more waves) .
Sitting out the back between waves, he looked pretty funny; you could only see him from the neck up...

What are you thinking for your next board?
Perhaps consider a 'fish' if speed is what you are after.
Dain Thomas, referred to above, has Steve Lis templates & builds a lovely board.

cheers,
andy

[Roy Stewart]

Roy, are you suggesting that heavier board and/or rider will go faster than a lighter board/rider merely because they are heavier? If so, then please forgive my ignorance, but I thought this rather mistaken notion was dispensed with by Galilei Galileo several centuries ago!

A heavier board rider will not go any faster than a lighter board/rider. True, they have a greater amount of gravitational energy available to them, but this is entirely counterbalanced by their greater I-N-E-R-T-I-A! (The heavier board/rider will, however, have greater momentum, and this will help them maintain their speed through turns, chop, bumps, etc.)

In addition, pumping will NOT ALWAYS increase the speed of a board and rider. For some board designs this may be true (e.g., thrusters, single fin pintails) in certain situations. For other boards it is not (e.g., fishes, flex spoons).

True, pumping “drives the board via muscular effort” but in what direction? Answer: Side to side!

Let’s take a look at pumping action on a skateboard. A skateboard transfers the rider’s side to side pumping action into forward movement, but remember a skateboard is operating upon a static medium. The skateboard has to be able to flex and change shape (e.g., the deck and the trucks) in order to translate the rider’s side to side pumping into forward momentum. (Try pumping a skateboard with a very stiff deck and tight trucks. Now try it with a skateboard with a “loose” set up. The difference will be readily apparent.)

Surfboards do not exhibit anywhere near the same degree of flexure/shape changing ability as does a skateboard. As we all know, a surfboard is operating in a fluid medium. The board flexes only to a very minor degree, but the wave can flex to a maximum degree (i.e., the water is displaced). A looser board will be easier to pump, but will not hold as well on critical, steep faces (in other words, the fastest part of the wave).

A surfboard is constantly being lifted up by and then traveling down the face of the wave. That where it’s main source of propulsion - gravity - comes from, not pumping. Thus, on a steep wave face, no pumping action is needed to attain maximum speed down the face of the wave (in fact, in this situation pumping will be counterproductive!).

Pumping is mainly utilized by surfers to generate speed on slower waves. (When comparing the speed of standup and kneeboards, I am discussing them in the context of quality, steep, fast waves, not slower, mush burger, type waves.)

Does a “surfboard designed for kneeling…have a better thrust/drag ratio than a surfboard designed for standing“? To demonstrate that it would be necessary to subject them to water tank tests.

Although it is true that, as Mr. Hart says, “kneeboard designs do not provide greater thrust, because gravitational potential energy (the main source of thrust) is dependent upon mass, not the posture of the rider“, his claim that “(it) is also doubtful that kneeboard design necessarily entails less drag per unit of mass than other board designs” may or may not be correct.

It is entirely possible that kneeboard designs may have either a greater Terminal Velocity or be able to approach their Terminal Velocity sooner/to a greater extent than surfboards. They might, for example, produce less drag because of less rail in the water and a reduced wetted surface area. (Once again, water tank tests would be necessary to prove/disprove this thesis.)

As Hart states, a “compact posture means less wind resistance“ and this definitely gives kneelos a slight advantage. Although true that “standup surfers also adopt compact postures”, kneelos have the advantage of ALWAYS being in a compact posture, not just “when necessary”. (Interesting enough, lowered wind resistance is one of the advantages touted by inflatable mat surfers.)

Kneelos have other advantages over standups which make them a bit faster: Lower center of gravity (more power in turn which helps generate speed). Quicker take-offs/getting tucked into a riding posture. Easier to follow/stay in the power spot of the wave (how many times have you seen a standup forced out of a tucked in position in the sweet spot of the wave that a kneelo could easily hold?).

Finally, in the subjective category, kneeboarding seems faster because we are closer to the surface of the wave.

Hello Brian, I am, wondering why you are calling me 'Mr Hart'. You quote me as Mr Hart. Why?

In answer to points raised in your post (above):

1) I did not say that a heavier board and rider necessarily go faster than a lighter one. The speed potential for a heavy or a light setup is theoretically the same.

2) Of course pumping will not necessarily always increase the speed of a board, because it must be done correctly on a suitably designed board. However, you say that:
"on a steep wave face, no pumping action is needed to attain maximum speed down the face of the wave (in fact, in this situation pumping will be counterproductive!)".
This is not correct. A steep wave face does not prevent a muscular pumping action from being transferred into forward motion, and pumping in this situation is not necessarily counterproductive.

3) You state that:
"True, pumping “drives the board via muscular effort” but in what direction? Answer: Side to side!"
This is not necessarily true. One of the most classic pumping motions is the weighting and unweighting motion used in a down the line situation. This pumping motion is primarily an up and down movement, not a side to side movement.

4) Your next statement that:
"Surfboards do not exhibit anywhere near the same degree of flexure/shape changing ability as does a skateboard".
Is also incorrect. Although foam and glass boards do not flex much, I must point out that I have been building flexible timber boards since 1995, and that some of my boards are able to flex at least four or five inches. I have designed this flex to be used to transfer an up and down (in relation to the deck) pumping motion into acceleration.

5) Regarding your 'Terminal velocity' theory, it is not the case that a surfboard has a theoretical terminal wave velocity (other than the limitation which occurs near the speed of light) because it has not yet been shown that there is a limit to how much friction can be reduced, and until that is done, the possibility of increasing speed by reducing friction will exist.
Furthermore, the maximum speed of any particular surfboard in a given situation will be affected by the weight of the rider, so it does not make sense to discuss the 'terminal velocity' of the board alone.

6) Regarding wind resistance, you state that:
"kneelos have the advantage of ALWAYS being in a compact posture"
A kneelo surfing erect has a less compact posture than a standup surfer in a tube crouch. So kneelos are not 'always' in a more compact posture than standup surfers.


Regards, Roy

[hart]

Hello Brian, I am, wondering why you are calling me 'Mr Hart'. You quote me as Mr Hart. Why?

I was wondering the same thing myself..not that I haven't been misquoted before

hart

[Roy Stewart]

" Just want to be misunderstood . . want to be feared in my neighbourhood . . .just want to be a moody man . . .say things that nobody can understand . . . "

Lyrics by ....?

[scoop]

Dorje

I went to a surf auction today and a "Sky" spoon by greenoughs mate Chris Brock was passed in at $1200 with no bid and a "Gordon Woods" spoon (reglossed) watertight but old water stained condition foam went for $700

[john -]

geez

despite the history major...im just not that into the past against money well spent on the future!...Lowrider might be kicking himself now about the lost oppotunity for what was it..... $250....but was it Sydney prices?...not sure the torquay guy was that "knowing"...he didnt look at me with that incredulous you couldnt afford it anyway buddy look

but Scoop, if i ever see one at a garage sale........

cheers

dorje