I’ve been studying the movie “Winged Migration” that Ambrose suggested a while back. It’s incredible; it’s like you’re flying with flocks of birds. I’ve noticed that a lot of birds have nice deep “double channels” along their backs while in flight. I suppose that without a spine it would be a deep single channel (which supports Loehr’s no stringer/single channel preference). Odd thing is that as their back/tail rocker increases (towards Earth in this case) the channels smooth out to a flat tail. (Remember: all of this is on the top of the bird in flight). My question is how would this effect a surfboard? Most deep channels, Bonzers come to mind, extend to the end of the board. What if the last 6" or so were flat? Thanks, Rob Olliges
It should turn better with the last bit flat. The boards I’ve had with deep channels or single deep concave all the way out the back tended to track noticeably. I’ve had the same boards computer-made with the same exact dimensions without the channels and they turned noticably better (and incidently were faster too) without the channels. I feel water resistance on deep channels. I know this may be controversial, but I believe after many experiments down this road that more surface area (and channels make for this over a flatter bottom)= more friction = less speed not more. This pertains for “out the back” channels. Ones that end at the rear of the side fins might not suffer from this feeling. By the way, I have felt slow-down from far-forward channels too. I think maybe if they are blended they might be better.
Rob… Things moving through the air or beneath and above the water, which have the ability to adapt their shapes in response to changes in the surrounding environment, are able to achieve the greatest control and speed over the widest range of conditions. What you said closely describes the bottom contours of a supple, low-pressure surf mat in flight across a wave. Functional adaptability. The closer a surfcraft gets to nature`s model, the better they work.
Rob, I’m really glad someone else has made this observation. An aeronautical engineer friend of mine helped me re-design my fins using computer generated hydrofoils. He stressed that the small reverse curve in trailing edge of the cross-section foil was essential in the design. It is called ‘reflex’, and virtually all modern aerofoils and hydrofoils use it. Basicly it creates a lot more lift due to the subtle redirection of the flow off the trailing edge. The fins went so well that I decided to incorporate the theory into the bottom design of my boards. I tried the smallest subtle change at first and it was amazing how it felt. I guess you could say it created a better glide characteristic, the board got up to speed quicker and held that speed for longer. Later boards I made became more exagerated and I found that due to the extra speed and cleaner release I could increase tail lift, gaining manouvrability, without losing speed. This was all done on modern shortboards between 6’ and 7’2". All these boards were in-line singles, so I’m not speaking any case for other fin setups. In the larger boards the reflex was very subtle, but the short boards much more exagerated. They gave my surfing another dimension, and control and speed in the tube and on the face was sensational. I recommend giving it a try. I’m now thinking combined with Blakestahs pivot fin idea…!!!..wow.
Can you further explain or diagram what you mean by a “small reverse curve in trailing edge” of a fin and how it would look on the bottom of a board? On a board would it be a lip and would it curve up towards the deck or down towards the bottom- or do I have the wrong mental picture entirely?
Righto guys birds are good but go one step further and you will run into a Penguin…Pauls design is scratched from all the information about the fastest flow forms aquatic and areodynamic. He crunched the numbers came up with the FP. And incidently you are noticing the twin channel effect on top of the bird whereas Pauls design has the energy trapped underneath. Providing lift. An experiment for the kids at home… Take a teaspoon, knife and go to the sink…turn on the tap halfway and play and actually watch whats going on. You might think this is funny but youll be amazed at the different flow characteristics… A knife edge will release the water (sharp rails on the tail - more speed) A teaspoon curve down into the flow will wrap the fluid around itself (rails) A teaspoon facing curve up into the fluid flow will trap energy(turing into lift for FP at speed) and redirect the fluid flow… basicly you get wet. Concaves trap energy and if shaped all the way to the tail, you will end up with too much lift under the tail your board and will lose direction at high speed (concaves) If you hang a teaspoon gently from the end of the handle between you finger tips with the curve facing the flow move the spoon just touch the fluid flow and youll notice it will be drawn into the flow. (rocker) A wave isnt made of flat straight lines so if you have the right rocker to match the wave similar to(syncromesh gears) your rocker is made up of nose lift, mid section, tail lift is what gets you through the bottom of the wave without it youll nose dive for sure too much means you have to stay in the power. The FP concave it may look extreme at one centimetre deep compared with 3mm concaves at present that run rail to rail, rail to rail concaves can at times catch an outside edge, the FP concave stops 6cm from the rail to leave a flat neutral section which eliminates this problem. Also the FP concave is flat not dished, a dished concave turns fast edge to edge but a flat bottom concave is more stable all round(especialy at high speed) The planshape of FP concave is much the same as the tail on a big wave speed board. You cant compress a fluid. Because of this the flow is constantly accelerating to match the reducing area finnaly bursting from the concave tip releasing a water jet that is then tricked into returning beneath the tail of the board providing lift (stern pressure wave) Returning more energy to the board eg “Penguins” and “12 meter” yachts use these principles that showed up though our research. Gentlemen grab your cutlery! http://www.geocities.com/wunderboyi/newsequence.html
You’re talking about a slight “downward” lip on the trailing edge of the board right. So your rocker sweeps upwards, and then in the last inch, a little lip pointing downwards redirects the water to fill the cavity left by the boards depression in the water? I assume doing the same thing over the last foot on each side of the rails in the tail would help this too… Corran
You’re talking about a shape like this? (--------) The concave area is in fact a flat just like the board hull itself, recessed into the bottom say 1cm, and the edges of this concave converge at the same rate that the rails are converging towards the tail? I tried that on a surf kayak. An interesting test was to cover the hull with dust with the board upside down. Then take an air blower, and starting at the nose, dorect air down the board, and watch the pattern of the dust blowing off. Its sucked into the narrow part of the concave area (venturi almost) and then ejects into a arcing spout. However, combined with added rocker, I found this to “suck” down more than lift up the tail. Perhaps this concave needs to end BEFORE the rocker in the tail becomes too extreme? Corran
What is tried to say is: a deep concave on the bottom of the board followed by a flat area (or a much shallower concave) in the last 6" or so of the board. This is comparable to what I saw on the birds: deep concave from mid-point changing to flat area in tail(feathers). This flat area occured in the tail of the birds which has increased rocker. How would this affect the boards handeling? I like Dale’s comparison to surf mats. Birds are light as air, probably weigh as much as a mat, and DO alter their shape in flight. Rob Olliges
Ouch. “S” bottoms. We (my freind and I) experimented with them a bit a while back. They were a bitch to paddle, especially into waves. With the tail rocker “reversed” the board tended to push the nose down and the tail up, creating a ton of lift in the tail. But with that lift was a major reduction in speed, (from the middle of the board to the nose being pushed deeply into the water) and a loss of control. (major drag) The board(s) no longer wanted to turn on rail, they wanted to remain flat on the surface… we actually resorted to really small fins and pivoting off our front feet, sliding the tail around like it was a snowboard. Eventually, the concept was abandoned, in favor of other interesting concepts. In my opinion there is somthing there, if I had more time and *money I’d probably still be screwing around. Check out Dale’s “S” bottomed belly board in the resources! -Carl
Sorry for my descriptions. Not an “S” bottom. I think you’ve mixed up the orientation of the bird and the surfboard. Normal bottom with deep double concaves that fade away in aprox. last 6" of the board. How does it surf? Rob Olliges
Corran… In it`s simplest form, there are two rocker lines in the bottom of a board with concave: the least degree of arc runs through the deepest portion of the scooped area, with increased curve following along either side of it. (photos courtesy Cooperfish Surfboards) http://www.cooperfishsurfboards.com/hornetindex.html 
Looks like its mostly up in the nose, and by the cedntre and back its a pretty flat hull again. One of the reasons I’m interested in this is in making a board for river surfing. We have very steep, narrow waves. Tail rocker makes them turn much faster, and also makes it much easier to stay in the pocket. But they are sloooowwwww. So if I can find a way to make it possible to have the tail rocker, and weight that when i need the board to stall and turn in a snap, but then move my weight forward so that the centre of the board is active, and the tail is being lifted by the concave centre, then I might have something so i can break out of the pocket into the fast (flat) water out to the side and make an arking carve back into the pocket, where I instantly weight the tail again to slow it down and lift the nose… get the idea. Its weird, but its fun! Corran http://www.2imagine.net/blogger2003/surf2.html
“…So if I can find a way to make it possible to have the tail rocker, and weight that when i need the board to stall and turn in a snap, but then move my weight forward so that the centre of the board is active, and the tail is being lifted by the concave centre, then I might have something so i can break out of the pocket into the fast (flat) water out to the side and make an arking carve back into the pocket, where I instantly weight the tail again to slow it down and lift the nose… get the idea.” Corran, You might consider designing a bottom with a faster, concave forward trim surface separated from a slower, convex/vee tail kick. This is an old idea, and it does work: “…The hydroplane surfboard: The deck contour harmonizes requirements of speed and sharp sliding angle. Spoon- shaped bow parts chops and eliminates slapping in windy conditions; semi-dropped rails amidship and fully dropped rails aft combine speed with high-riding capability on steep walls. High speed planing surface (below) terminates in a sharp breakaway edge; a critical degree of transverse bottom curvature provides balance between turning ease and stability; the high-drag scorpion tail enables stalling and sharp turns when in contact with the water…” (John Kelly) http://www.surfresearch.com.au/00000190.html 
It’s a pity I can’t explain myself better. It’s nothing like the fat penguin or any of the theories described about the fp. It doesn’t add obviously visible shape to the bottom, unless you have a keen eye and know what your looking for. Of course if you put an exagerated curve into the bottom it’s going to do wierd things like lift the tail too much, which obviously would push the nose into the water and slow you down. When I said a subtle reflex I meant a SUBTLE reflex. Some of you may need to realise what subtle is. Air is less dense so needs more exageration. Water, as someone reminded us, doesn’t compress, so only the tiniest reflex is nessesary to create a noticable effect. I can only try and describe mine a bit more to give you an idea. Look at the board side on, in other words looking at the foil of the board, you can see the distribution of thickness from nose to tail, including nose and tail lift. The amount I put in is not noticable and only just measurable with a straight edge and definitely has NO exagerations. Yes, I run this shape, diminishing, up to the wide point, but it is incorporated into a very slight rolled vee which maxes out just ahead of my back foot, actually where the larger fin is. The smaller fin generally ends up positioned at the start of the reflex. I’m getting tired, think about that for a while.
Hey Guys this is cutting edge I will have to get Paul over tommorrow to read your very interesting explanations and thoughts… My two bobs worth would be predictable to say the least… Fat Penguin are fluid gliders…They incorporate exactly the same physics as aircraft, penguins, yatchs, ground effects on race cars all use a similar undrerlying priciples. Point being if you go where Paul has you will end up with the same answers…And in my opinion you will probably end up with the same board… Pauls board displaces and recaptures the bow pressure wave by wrapping it on to itself and channeling it away with the convave and splitting it at the wing leading edge creating lift as it runs over the top like the spoon in the tap it will want to go up, while the energy returned back into the concave is then tricked to release under the tail of the board also providing lift thereby overcomming a primary source of drag…FP fin system reduced drag by 8% by removing the large surface area drive fin and replacing it with two small surface area canards, if you measured the surface area of the combined forward fins and compared it with the surface area of the large drive fin the the ratio would be half. Subtle things but they all add up…and theres more than that going on with pauls board I know this much. We claim at least 30% more efficient than a planing surf form that will always be a specialist board for a certain condition eg,… Indonesia to Jbay to Pipeline to Bells beach to 3ft smush… Pauls FP will surf 1 to 3 metre waves anywhere soft warm water or dense cold water the more energy the board has the stabler they become…Fast stable lively platforms that require thought before acting as you will have a high speed stack if you dont… Footage footage I hear you oh but its not that simple when you have commitments outside your passion…Ill just jump on a plane wiht my rider and camera crew and do a shoot at Santa Cruz…oh I wish I wish so much to go to your country and be a showoff !!! Back to reality…please be my guest find someone stupid enough to try and shape a FP…Then ride it but not at your favorite break(to emmbarrasing Ive put a lot of dung on this design what if it works)and send me the feed back personaly…And I promise after all of you show me shots of your boards Im going to say what heaps of shit they are and ugly too !!! but if after all this and my feedback tells me we are out with the design I WILL GO AWAY…
Dr. Obliges you are gettin it… dale’s got it kelly got it first when I saw it at kapiolani park i was infected…I didnt know it at the time but that is a door worth crawling through ,chasing a rabbit and I am still chasing and assembling clues…put on your top hat and have some tea…ok cut those concaves all the way through to the very tail…now foil the tail out and up from the bottom from behind the fin placement …about 7-8 inches … the result wil be the flattening out of this trailing section to dead flat and kicking the bottom curve into a steep vector1/2" to an 1"in 8 inches… relieving water flow resistance increasing flight glide and not impedeing direction change under full power …yes concaves can increase to as much depth as you can with stand G-force in a turn…1/2" tail concaves not excessive ahead of the fin apexing about 8" to a foot ahead of leading edge… oh yea I never met kelly san or ever talked to him yet I believe I grok the essence ok his trajectory…yet I have intentionally edited the hard edge transition release on the bottom in the picture of the Hydro- Board and evolved it into a hot-curl flow bottom ( also kelly inspired?) to maintain surface tension advantages… Jimmy says they ride backwards real good too… ambrose…them birds they are hot watch em the glide towards the beach on set updrafts… take off on the waves under the updrafts they are riding… the go all the way to “Z” …I like to call em bird sets
I’m as guilty as the next guy for looking at the fp and thinking it was wierd. Mainly because it does. I look back and realise I should have taken it for a surf when I had the chance. I now look back and realise I wasn’t as open minded as I thought I was. You could have called it the ‘flying penguin’ and many more people may have taken it more seriously. Long live experimentation. I hate to say it but the reason mainstream modern boards all look the same is because they work. Got back from snowboarding yesterday, read these posts, and must say the same of snow stuff. Apart from minor design differences, a ski is a ski and a snowboard is a snowboard. My quest when I started surfing and making boards was to make the whole experience as pleasurable as possible. I tried just about everything, but the harder I tried the more I realised that simplification was the key. That didn’t mean simple performance, just get rid of all the things that hindered me such as channels, complicated multiple fin set-ups, overly thick or thin boards etc, etc, etc. Then make what I had work to its designed function. I like the wave contact and rail to rail feeling of a vee bottom, but it had its drawbacks. I like the smooth positive feel and control of a single fin, but it also had its drawbacks. So I worked on them, and the in-line fin set-up on an integrated reflex bottom is what I came up with. It’s not a bird, or a plane, it’s a surfboard, and it probably doesn’t suit everyone, but then again, what does? . Catch a wave for will ya, I need it!
inhale fresh rich rightous air…hold it a little exhale slowly and conciously…you are riding a great and kelidoscopic wave…want another?..ambrose…burping pecan raisin toast
Oh IM sorry to have misjudged the imperical minds of this BB, It seems Ive indeed grossly overstated my obviously flawed misconceptions about the FP and how it WORKS. I will now gratiously bow down to the overwelming opinions and be humble to the status quo…NOT… Read my lips FP are 30%more efficient than standard planing hulls. PLease tell me why would I say that we are achiving better results if we are not, why would I put FP designs on the web for anyone to try to build, Why would I state exagerations to then be found out to be incorrect that would be leaving myself wide open. Build the Dam board then let me know if its a dud… http://www.geocities.com/wunderboyi/ninetysixpercent.html