WHOA daddy !!! thanks dale I just ordered 6 copies of the book 3 hard cover and 3 soft cover to sell in the store Yabba Dabba Doooooo…in the words of an estute robot INPUT! IINNNNPUUUUUTTT…ambrose…chicken skin…
Just for fun, here`s a distant, water-related comparison… More efficient, higher speed boat hull designs have for many years used strakes, chines, dihedral/conic delta running surfaces. To a lesser degree, all the same basic aspects of design can also apply to certain types of wave craft. 
Dale, The photos definitely make the image clearer-thanks. Still, it seems to me the bodyboard with less vee would be more efficent on smaller waves at producing planing speed. The kneeboard, on the other hand, with a deeper vee would require more power to achieve the same planing speed. Ah! I have answered my own problem: Deeper vee for more powerful waves??? Patrick
yup!
in a similar way with a v-bottomed hull, a given amount of weight will need more area to plane when going slower, less when going faster. That’s the cool thing about strakes; they not only deflect the water away from the hull ( less skin drag ) they also can deflect it downwards to produce more lift. Something else about non-flat-bottomed planing hulls; what I’d call the rule of constant sectional area. The area of the immersed cross-sections of a planing hull will increase from the bow ( nose ) to the point where that area is maximum. Then from there to the stern ( tail) the cross-sectional areas tend to stay the same. If the hull form is designed to do this, good, otherwise the stern or tail tends to squat ( get sucked down) . This has some applications to excessive tail kick and to channels, concaves and such in the tail.
these boat illustrations illustrate well the simalarities to wide tail planing craft yet dont address the narrowed self closing round tail plan shapes common to double ender dorys and double ender small sailing craft…longer yet the plan shape solutions resolve the self closing, slow speed perhaps wake question…were square tails prehistoricly prefered for upright storage…? ambrose…dancing with 12’+conceptual realities…
Ah yes…the difference being that dories, rowing shells, double-ended sailboats and powerboats and the like are displacement craft. That is, they normally operate at a speed which is called ‘hull speed’. In English measurements that’s about 1 1/3 x square root of the waterline length in feet x statute miles per hour. For instance, a 36’ hull can travel around 8 MPH before it starts getting over hull speed and starts climbing up its bow wave. That takes a lot more power applied. Over 2 x square root, etc, that’s what’s generally considered to be planing speed. For instance, let’s take a 9’ hull. at 6 MPH, it’s planing. The speed you can get for a given amount of power varies with the weight and the area of the hull - skin drag in that case. Lots of surfboards are referred to as ‘displacement hulls’, though the term is kinda misapplied once the thing is actually surfing. While paddling a board, there just isn’t enough power to get the thing planing - takes the power available from a wave. At the same time, some of the really long competition paddleboards tend to be kinda round bottomed real displacement hulls… see the link below. hope that’s of use doc… http://www.joebarkpaddleboards.com/community/gear.htm#paddle
Doc, Good explainations. Thanks for posting them. I’m going to find a good book on this topic and do a little reading. Patrick
Hi Patrick, Thanks for the kind words. If you don’t mind a couple suggestions on some good books to read on the subject from an old Naval Architecture/Marine Engineering student: First would be Skene’s Elements of Yacht Design - a kinda lite version of what’s involved in the design of small vessels, both displacement and planing hulls, where such things as structural design are not dealt with to any large extent. I’d look for a used copy of the recent ( late 60s-early '70s) edition written by Francis Kinney rather than the reprint of the 1930-something edition that’s been reprinted in paperback. Then there’s Lindsay Lord’s Naval Architecture of Planing Hulls - probably _the_textbook on the subject. The late Dr. Lord ( one of the first doctorates in Naval Architecture, I think) taught the subject and was pretty much the guy in planing hull analysis and design. If it’s not in there, it’s not worth knowing unless you’re planning on doing a degree in NA/ME. hope that’s of use. Should be able to find either through http://www.addall.com/ or Bibliofind I found one copy of Lord’s book on each, though the one on Bibliofind was a genuine bargain …link below doc… http://www.bibliofind.com
so 9’ hull at 6 knots thats planing?..so surfboard on wave is like plaing x6 if we use the old speedometer on surfboard test 1964 35mph? is surfing in naval architecture a specific term like over x knots?or when we hear surfing does it mean we have stepped out of measurable criterion? in other words are there applicicable principals and terminology for each incremental speed increase?..like a hurricane on the Beaufort scale is 65 knots or over…terminology is facinating is there a place where hydroplaning starts or is that a misnomer and they just mean planing/ please and thank you ambrose…in atendance
Hey, Ambrose. Yeah, all surf craft are planing hulls in use, not displacement hulls, though once you get up to a plane it’s pretty much all ‘planing hull’ from there. What changes with speed is how much hull has to be in the water to hold the weight at that speed. Besides things like air resistance and such, which tend to change with the square of speed; double your speed and you have four times as much drag from air and water. Hydroplaning and planing…well, the terminology is kinda interesting, though in normal use a planing hull is pretty much a planing hull, with hydroplaning a variation that’s used interchangably. There’s no particular steps, say , when you get to 2x planing speed, or 10x planing speed, no abrupt changes. It’s kinda like the speed of sound: obnce you get through it, that’s it, what you have when you go faster are small, incremental things like vibration and shock wave effects, not a new set of problems whenever you double your speed. There’s no ‘surfing’ in naval architecture, give or take a term used for a small boat going uncontrollably down the face of a very big storm wave…then again, there’s little or no naval architecture/marine engineering in surfing. You know quite a lot about the history of flight: surfing is at the stage that flight was at in around 1880, before anybody came along and did any research beyond strapping on a set of wood, canvas and feathers wings and jumping off a handy cliff. No Wright Brothers in surfing as yet, though it wouldn’t be all that tough. You might enjoy some of these- (link below) http://www.lerc.nasa.gov/WWW/Wright/airplane/shortw.html
A theisis by Michael Paine that is accessible via www.surfresearch.com.au - he actually build a tank and attempted measurements. http://www1.tpgi.com.au/users/mpaine/thesis.html#nacadata http://www1.tpgi.com.au/users/mpaine/thesis.html#nacadata
Foiling Doc, it’s good to see the real definition of displacement hull appear. Surfing terminology is often an amalgamation of slang and science. It can be hard to pin things down on the lofting table well using common surf terminology. The foils used in creating high performance surf-craft continue to evolve. They are always in a state of arriving to serve the craft, and in the wave they’re doing the same thing, that is arriving in the forming wave. There are waves rolling across the shaping rooms much like the ones breaking at the beach. The concepts of flight and swimming and planeing join in surf-craft foils. Considering only two and ignoring the third limits the range of a board’s performance. Foiling a board is like accelerated erosion, relaxing you become like water. That fluidity enters what you’re shaping and then that you begin to understand who Dick Brewer is. On thing is for sure. The dictionary continues to get new words all the time, and there are new board shapes entering the water all the time. Bottom line: Stoked means a little something different to everyone.
I foiled a new pair of Dr. deets swim fins today,they came out really good.I used a little 4" makita grinder with 60 grit then block sanded to tune them up.It all went real fast.The fins look like beefed up duckfeet.----almost on subject[smile]The Greenough modification is right-on.
Yep, I’d seen that one…a good beginning, never followed up to any real extent.
Doc: Thanks for the references. I copied and pasted your post and will be checking around for the books. Patrick
Hi Patrick, Again, thanks for the kind words. I’d jump on that copy of the Lord book at Bibliofind, as it’s a real bargain- the seller doesn’t know what he’s got. I’ll also mention that I happily paid ten times as much for the copy I have. Best doc…
Great Thread…This one needs to turned in to an “Article” for the Archives.Thanks Doc and Dale for all that hard work.Not many folks would take the time to do this.I have to vote you two guys as some of the finest contributers around lately.Hats off to ya.