Just a humble surfer who just shaped my first board and am twice as excited to do board #2. I’ve been doing a lot of research on different shapes/ design concepts and have been really interested in the Simmons Planing Hull concepts as well as TOMOs radical design concepts. Anyone know where I can get more specific info on both of these ie. better pics of the contours etc. I’ve found a lot of info that mentions “planing” and “hydrofoil” concepts but haven’t been able to really find any info that brakes down either concept into applicable specifics. Any advice would be killer. Thanks!
Thanks grumpy. I’ve been looking to get a hold of this but cant seem to find it anywhere. The link of PDF’s you sent were “NOT FOUND”. I’ll keep trying to hunt it down…
A couple of years ago, several used copies of Lindsay-Lord’s book were available at Amazon. Used copies in good condition were running $95 to $110. The copy I have has a price of $6.95 written in pencil on the inside front cover (presumably it’s original cost when published).
Essentially surfing’s equivalent of the cost of oil?
Bummer. It was all there about a month ago. Guess I should have printed it out.
Suffice to say; flat rocker and flat bottoms are fast.
http://hydrodynamica.com/totem/lord-board
My copy of the Lord book is for sale on here on ebay.
I found it an interesting book, but I think its influence on surfboard design is way overstated. All the tests Lord did were on flat water, allowing him to calculate the aspect ratio (width to length) which created the least drag and turbulence. A surfboard of any sort rarely sits flat on the water, so the aspect ratio really is meaningless. The most meaningful info I got from this book is that all surfboards are hulls. Some displace, and some plane. But both do at least a little of each. When it comes down to it, wider and flatter is faster, and a rolled bottom will smooth out the water it passes through. While I’d love to sell my copy of the book, I’d caution anyone who thinks that a book on boat design will hold any silver bullets for the surfboard builder. Having said that, it is a pretty cool old book, with some excellent diagrams and experiments!
The aspect ratio is a measure of the induced drag. It is not a measure of the drag associated with turbulence (e.g. skin friction and form drag).
This drag is associated with the generation of dynamic lift (no lift generated -> no induced drag). Lift is generated by the downward deflection of water passing under the hull of the craft. Water molecules approaching the hull of the craft have two options: (1) they can be deflected downward, or, (2) they can be deflected off to either side of the hull. In accordance with Newton’s Second Law, molecules deflected downward generate lift while molecules deflected off to the side do not. Every thing else (wetted area, angle-of-attack, planform, etc.) remaining the same, the higher the aspect ratio, the bigger the fraction of the approaching molecules that are deflected downward, thus increasing the lift generated. The greater the lift generated the smaller the angle-of-attack necessary to support the weight of the board and rider…and from vector analysis, the smaller the induced drag.
An aspect ratio equal to the (wetted) width (of a hull) divided by the wetted length is for rectangular planforms. The more general relationship for different planforms (e.g. ellipse, triangular, rectangular, etc.) is that the aspect ratio of a hull is the square of the maximum wetted width divided by the wetted area, or, equivalently, it is equal to the average wetted length divided by the maximum wetted width.
The tendency for fluids to move from areas of high pressure (e.g. under the hull) to lower pressure (e.g. out to the sides of the hull) is universal. In general, the use of aspect ratio to estimate the consequences of planform on the induced drag yields decent estimates of the effects of planform on the induced drag. For example, aspect ratio considerations predict that wide tail planforms should be more efficient than narrower tail planforms in weak surf.
I am pretty well convinced that aspect ratio is an important factor (and not meaningless) in the performance of planing surf craft. I am less certain about the validity of the common held conclusion that since flat boards (zero rocker) are fastest on a flat sea surface, they will also be the fastest when riding on the face of a wave. In particular, a first order approximation of the flow field of water across the bottom of the board would suggest that the equivalent of a no rocker board moving across flat water would be a board whose rocker is the same as the curvature of the undisturbed sea surface along the pathline of the board.
mtb
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''..... the equivalent of a no rocker board moving across flat water, would be a board whose rocker is the same as the curvature of the undisturbed sea surface along the pathline of the board. ''
mtb
[/quote]
There, is the gold nugget!
Again, absolutely true until that board breaks out of trim to turn. The modern shortboard is almost always in a state of climbing or falling on the face of the wave. Very rarely is it sitting neatly in the curve of the wave. I wasn’t disputing the science behind Lord’s book. I was merely cautioning any potential buyers. I know that a folklore has sprung up around this book in the surfing community, but most board builders will find that less than a couple of pages will be useful in any way for surfboard design. And even the bits that are really don’t take the shape of the wave or the rail to rail movement of a surfboard. The movement toward shorter wider boards was already happening before most shapers had ever heard of this book, and the ones who have applied some of the info from the book, like Simmons, were making longer boards, not shorter. I might be totally wrong, and I’d be interested to hear that views of anyone else who has read it.
"but most board builders will find that less than a couple of pages will be useful in any way for surfboard design."
Agreed. I have owned and read the book and there was little that applied directly to surfboards. What applies in a test tank does not necessarily apply to real world surfing where as mentioned, rail to rail and fore-aft weight transfers are constantly in effect.
Of course Bob Simmons allegedly read it and supposedly used some of the theory in his own designs. Since Simmons (and particularly Mini-Simmons boards) is popular right now, it figures that the book would be popular as well.
In my opinion one of the coolest designs of a board using the Lord theories(?) would have to be Dale Solomonson's far out bellyboards. A very similar design is shown in the book. I don't know for sure that Dale used the book for inspiration but after comparing the two designs, I would have to think so.
http://www.quivermag.com/node/664
So as a practical example for me to better understand: they sat that surfer/shaper Daniel Thomson uses these (Bernouli and Lords) principles in his board design to create more efficient lift and speed generation. To quote: “Outline has then been straightened and foiled for drive and to maximising planing speed”.
What modifications are (hypothetically) increasing planing speed in his boards? “Foiled/straightened” rails? Or hull shape? And when they say his rails are foiled what are they referring to?
For those of you cringing at my obvious ignorance to the fancy lingo and rhetoric… please be patient. I’ve been surfing for quite some time, but only recently has the physics that goes into it become very intriguing to me and I’m devouring all this information.
BTW you guys are posting some pretty intense stuff (for me anyway) and I’m enjoying all this info so THANKS!
i've seen some of tomo's boards.radical stuff! the round nosed ones have hull up front transitioning into some concaves,chennels with stealth aircraft like tails. i have always wanted to meld the front third of a "hull" eg, liddle, with the back being a bonzer eg, malcom. tomos boards are kind of something like that yet, beyond bonzer in the tail end.
for more info on hulls might want to checl liddlesurfboards.com
Hey guys, this is pretty interesting stuff. Does anybody know where I can get a copy of this book either printed or in digital form?
Thanks