Not only is George a mad surfboard scientist, he is a great surfer. About 25 years ago he busted an air over me on a twin fin, on a shalow reef!
hands down the most positive, informative thread that has been on Sway’s in years.
George’s stoke is palable through his words alone.
And stoke is what we come here for…
with that said, a question for George.
With still a few development generations to go before fully capable, I would posit that once the required level of of technology in 3D printing has been reached, and as importantly the required prinable materials as well, it will open up extreme tolerence design/building with the ability to build/install multiple tuned flex patterns into the shape.
Consider this an over reach, or do you foresee 3D printing as the next logical step in computer controlled design/build progression?
First Mahalo nui for doing this.
As you are no doubt aware the “step ups” surfers are riding today are way shorter than this oldphart can fathom. Recently thought I would build one.
Made several mistakes. Bear with me here, just an out of touch old grey beard.
Ordered a US blanks 7-0 A w/ +½” tail rocker.
Laid out a nice 6-8, my son comes by and it’s “oh Popz”
Came out 6-2 but I lost some nose rocker.
Board is a winner, my concern is mostly nose rocker, I am thinking of jumping down to the 6-5 A which has a stock nose rocker @ 5 1/16” Ya know I’ll lose a little so I’m plotting but what is the norm?
Question is, on a 6-2 “step up” what kind of nose rocker (and tail if you will) are the pro’s ( and or better riders) using?
Any advice will be greatly appreciated.
Aloha
That is very impressive Greg, I love the attention to detail. It’s probably one of the many reasons why people love your boards so much. Is there a particular foil you are trying to create? And, is the foil the same at the root of the fin as it is going out to the tip? (Surfboards being not self-powered, are VERY sensitive to the littlest detail and I find anomalies in the fins are usually much more profound than anomalies in the shape, both being important to get that last 5% or so…) I’d love to see a set of those fins, better yet I’d love to try a set!! ha. Thanks Greg!
Man recently I replaced/upgraded my Vee-wheels in the gantry of our shaping machine, and I got to say I cannot believe how perfect the rails have gotten. The hard part about CNC is to make what you see on your Design Monitor to be exactly what the machine cuts. Our accuracy is better than 30-thousands of an inch across 11 feet. I was cutting some boards for Carl Ekstrom and just as we finished cutting one of his boards he pulls out this Contour Gauge of the rail. As the cutter is spooling down, he puts his gauge up against the cut shape, and he says, “Yup,” turns to me and starts laughing, “How 'bout that…” he said. (He also put his Gauges (Rail Profiles) up against the computer screen to check and it was spot on. It’s been almost 10 years and none of this was easy, it took and is still taking a lot of effort to get those great cuts. Once dialed-in though, it can cut all day, every day, EXACTLY as instructed.
“do you use science/math/engineering to design your (specific) rail profile shapes?” I really just learned what “felt” “right” while surfing. Rails definitely affect the “feel” of a board, The ways in which the rails work and along different parts of a board AND in different wave positions, make the rail the least understood. It has been best to follow what others who have met success have done and try it, that way you would meet with some degree of success. So rather than use analytical tools (with the exception of FEA, which would be GREAT for super complex stuff like this,) I try to take the other approach- “field testing.” In engineering, testing costs in a LOT of ways, money, time, support, meetings, etc. But NOT with surfboards. Look at it this way, if Boeing designed the 747, no theoretical testing or component testing, just put it together and hired some “test pilots” from the local prison, it would take quite a few “cycles” before they got one off the ground. In contrast, a surfboard is simple, easy to build, fun to test. Surfboards are “quick to prototype” and that’s why I say go out there and try stuff. To contradict what I said about paradigm in design, the rail is so complex that it is beneficial to do “empirical testing.” One of the best people on the planet at this is Tom Morey, who understands how rails work to the highest degree. Other shapers/designers who can make a rail work are Dick Brewer and Mike Diffenderfer. Many others as well, but that should supply someone with enough info to start some good test boards. Brewer says to make the critical part of the rail to look like a “ping pong ball” and Diff said, like a “ball bearing.” So for the classic rail as we know it, that is a good guide. Morey’s stuff is along another branch, he can make a rail hold, just look at guys stand up surfing Pipe on Body Boards without flippers. Speaking of hold, Skip Frye and Greg Liddle come to mind for that kind of rail. And the down rail, which Hynson got inspiration for from T-Boy, who studied under Quigg. Don’t forget MacTavish, (I can see this list is going to get big, I’ll stop.)
As you divert from the classic ping pong ball, you either pinch it, or fatten it. Pinching it tends to make the rail penetrate the water, but also can provide hold along the sharpened radius. Fattening, or leaving a “vertical side wall” to the rail will allow the board to travel through rough spots like whitewater.
Unfortunately, there is NO RIGHT ANSWER to the best rail, so all rails in some way are valid. I use many different rails. This is a weak answer, but is what comes to mind as the guiding force behind how I would find a killer rail for a series of boards as they develop.
Hi Andrew, I am all for stringerless or composite stringers! But I must qualify that statement, “I like stringerless boards with alternative glass jobs.” I am willing to give up one thing to gain another, because I think the gain is large and worthwhile. Stringers are the centerline. Gordon Clark put a lot of effort into finding the right combinations of wood(s) and foam to produce a quality product at the time, many others contributed to this effort. The concept of a stringer should not be completely dismissed. If you are building a board from that era, or building a board of conventional materials, the stringer is actually a very refined thing.
That said, although I use boards with stirngers all the time, I know the stringer does very little to prevent twist in a board, and does quite a bit to decrease straight bending. This is almost the opposite of what we should have in a high performance (or future performance) surfboard. We want a lesser amount of twist and we want more straight bending. And we want the straight bending to be very responsive (with good timing to rider inputs.) I suppose we could build a “torque box” inside the board, but what a waste when the board itself is a torque box. Plus being of monocoque construction, (exoskeleton,) a stringerless surfboard is freed up to allow more articulation, THEN we pare down the degrees of freedom by choosing various skins (I tend to like fabrics,) and orient them in potentially ideal directions. In addition to this, we can use various foam cores (or NO core,) in different parts of a board. We can have the same foam thoughout, with different shear/elastic properties. Eventually someone is going to figure out which parts of a board needs to be springy and which part needs to be stiff. (AND I MEAN FOR REAL, NOT FROM A MARKETING POV.) So far no one has figured it out, the surfing will not appear as it does now. I am surprised more builders are not hauling ass on this, it’s not like we are all building Mars rockets, you can build the “golden bb” in just a few days and change humanity (er, “surfing humanity”…) Pressure. Most builders are under pressure so they cannot pursue this quest, either time, money, production obligations, market confidence, coolness, or style act as preventative forces. It’s wide open, and I think stringerless, flexy base materials are the start, then add the physical constraints and enhancements.
Hi Bob, I think all 3 directions with the finless sound good. Like I mentioned, I’ve seen guys at Pipe stand up surf a finless bodyboard (without flippers on,) totally locked in and going about as fast as any surf vehicle I’ve seen. How? I thought for a long time “Oh he’s dragging a foot, or his butt” or something but it would slow the board down, so I don’t know how or why yet.
So there’s the hope. Most bodyboards are flat or subtlely concaved, others might have channels but I’ve seen the simple ones produce.
There is one guy in my area I’ve worked with on finless boards and we got it to work well. He can do a bottom turn standing tall (NOT in a squat) and the acceleration is amazing. That said, the absolute traction/hold is not adequate enough to be compared to a finned surfboard. There was a time when I thought fins did almost no “foil lifting,” that their main real function was to act like a weather vane, keeping the board pointing the right way… …so the rail could do its’ thing and produce decent hold and forward drive.
Thus, one thing needs to be tested: a finless board that has some sort of “dragger” on it, probably on the aft corners. Not sure what, but the goal should be “not a fin” just based upon principle. That dragger would allow the rail to be applied to the rail face- (for a “grippy” rail look at Skip Frye’s boards, I’ve ridden them without fins and they totally hold in light trim, until the back corner pops out.) The shape of the rail probably should hold-in best around the back foot area, less so up front.
“I have three ideas - a 1” thick or so version of an alaia (for speed with control coming from the rails) with a virtually flat bottom, a board with a single deep concave or thirdly a board which utilises bottom ridges and contours. What direction would you go?"
I’d keep it simple Bob, and build a series of boards starting with the flat one first. I would work very hard on the rail shape, especially at the “business end” of the board (tail, below waterline,) and make it hold in. Probably study good bodyboards. Look at Morey’s latest finless boards. I would keep the board fairly narrow. The radius of curvature of that part of the rail will be crucial and speed-dependent, so I would watch what speeds the board holds in the best (eg. a finless that holds well in the low-speed dynamic will probably not hold well in the high speed regime.) I would build my rails out of material that I could shape post-glass. I’ve done that, packed a fish rail with microspheres, surfed it, then shaped it down, surfed it, went into the beach, got my sanding block out of my backpack and whittled- learned a LOT, in fact, more than I could have imagined, I didn’t know the shape and volume of a rail would matter so much, I thought most of it stayed dry, ha. Plumber’s putty works well for this also. That’s my advice.
I hope I didn’t do that air-over-human maliciously, I was kind of a dick back then. Way too aggro in the water. The only thing that bums me out about the old days was being a localizer dick. After traveling and being at the other end of it, I got my mind right and enjoy doing airs over people a lot more now… …That said, it was a LOT less crowded where we live back then, ha. Seriously though, I’d like to know more about that, I only did that maybe a few times, it was probably on a fish or quad fish. Too funny you’d remember that. Was the board black or blackish-blue?
@Icc-
3D Printing. In one of the first posts I mentioned SMA’s, my thought was to do the material network using multi-material 3D printers (they said unlimited budget…) and build a board from the inside, out. But Shape Memory Alloys have not been put through a printer yet, and a lot of R&D must be put into how to induce pre-stress into the printed material even though it would be printed “unstressed”. My guess is to induce an electric current though the SMA as it is printed and hardens, then pull the voltage. The printer will allow us to built board without wastage. The board would probably not get any glass, maybe microwave it to get a slick skin on it? ha. Not sure what the power consumption would be for SMA’s in a “Shape Shifting Surfboard” but either a battery or maybe the metallic network itself could also purpose as a battery/capacitor?
Anyways, backing off the super metal alloy trip. Foams of various physical behaviors will be shot through printers very soon, trust me I know, I cannot disclose. Stitching a board together from the inside, out, will allow for total control of all aspects. It is NOT too far fetched. We will not be the target market, we will get the trickle-down from aerospace. We will get the subsequent breakthroughs from a someone working in a garage.
"Came out 6-2 but I lost some nose rocker.
Board is a winner, my concern is mostly nose rocker, I am thinking of jumping down to the 6-5 A which has a stock nose rocker @ 5 1/16” Ya know I’ll lose a little so I’m plotting but what is the norm?"
Hmmm, a little confused, if the board is a “winner” then the nose rocker is perfect. Don’t "fix"it. Do you think maybe the board might be working so well to earn Winner status because of the lost nose rocker? That was the main reason I squared the nose off certain types of boards, (and dropped the nose rocker,) it REALLY made a difference!
I need more information on this. Get a straight edge (I bought an 8 foot one) and lay it along the board, bottom, up, to get a rocker measurement. A common way to find rocker is to lay the straight edge along the bottom, touching the board at the center, 37" from each end in your case. I “hold” the straight edge with tent clamps, teeter tottering on the EXACT center contact tangent point. Get me the rocker numbers at the nose and tail and 1 foot in from each end, and maybe I can tell you that there’s something wrong, but it’s a winner now(?)
BTW, NEVER trust the rockers to be repeatable every time you shape. I shaped by hand for 30 years and chased the lotus, then for the last nearly 10 years I’ve used the CNC machine. The machine showed how much blanks VARY- I built rocker templates of my “magic” boards: build a rocker template! better yet, build a rocker gauge so you can adjust it. Next time you shape, do the same number of passes with your planer then finish up by using the rocker template to get you close to that same Winner Board.
Best regards,
George
Hello George,
Is the Morey board you were thinking of, “the one” - http://catchsurf.com/the-one-surfboard.html Looks like there is a step in the bottom or some sort of break in the rail line.
Regarding your idea of a “dragger” - could this board be akin to what you were thinking:http://chris-garrett.myshopify.com/pages/finless-friction-free-surfboard
Is it possible to say more about your style of finless board? If not, that is ok. Thanks again.
Bob
Sorry for any confusion, by “winner” is a great ride report, however reviewing videos when boy got low in the barrel the nose is sketchy. Been on a minimal nose rocker crusade for a while now and you are right, relaxed nose rocker (for me) works well in smaller surf. Just wanting to gadge where I’m at with a bigger wave board.
Don’t have board here data from build sheet is as close as I can do for now.
4 5/16 @nose 1 ¾ @12” ½ @ 24” 1/32 @36”
2” @ tail 1 7/16 @ 12” 15/16” @ 24” 1/8@ 36”
George you taught me something as I have always had to have a little help with my rocker stick, “tent clamps” Thanks!!!
The winner is more the shape and harder edges cure the nose rocker or not I stoked!
Best to you.
how does the inverted v differ in performance from a standard rounded concave? similar dynamics with less drag?
have you tried varial foam for stringerless boards?
interesting theories on the bending direction that is best. i have found that getting ‘straight’ bending instead of ‘torsional’ bending can be amazing in critical sections on high performance waves with power but not so good for waves were you have to generate your own speed. i have come to really love the consistent performance of a very thin center stringer in an eps core across most small-medium sized wave conditions.
Okay I got you now,
"Don’t have board here data from build sheet is as close as I can do for now.
4 5/16 @nose 1 ¾ @12” ½ @ 24” 1/32 @36”
2” @ tail 1 7/16 @ 12” 15/16” @ 24” 1/8@ 36”"
I heard Rusty say that 1/4" of tail rocker can do the job of 2" of nose rocker. I visualize the board doing a bit of a “wheelie” when rocking back onto the tail, and MORE tail rocker will do that for you. That said, I think your back half numbers look fine. You can do with a little more nose rocker, but also lengthen the board slightly. Are you using U.S. Blanks exclusively? Try their 65R, it will have the right rocker for the board and allow for good thickness throughout. Let us know if you do this and meet some success with it, because your effort may help someone else on here some day!
Yes, that’s Morey’s creation! I think you can smoothly transition the two types of rails, I’ve actually been involved with a couple variants of this. I really think it will be a viable board in the near future, right now I think the finless is wrongly influenced by wider designs like Bauguess’ Mini Simmons boards, probably better to go narrow and pretty parallel like the ancient alaia design. This will increase the amount of pressure on the critical contours and produce more lateral resistance which would allow the rail to do its’ thing.
Here is the “dragger” concept I meant (the link provided did not work, so I could not see what it was.(see at bottom of thread, forgive my ghetto sketch) The one caveat I would have is the dragger I show could be very dangerous. It needs to be “flexible” but not so flexy that it would “flutter” at speed. This would be too much drag. You want it to be a gentle flexing but yielding enough to get some lateral drag, but going forward the board would be slippery still. In turns, I’d want the draggers to bend a lot, like the tail fin of a Thresher shark, it would hold in well but the “spring back” of the dragger would not be too forceful, that would be bad.
Notice the arrow I drew in the Rear View/Cross Section, I am pointing to the spot where you need to pay attention to the radius of the rail transition. I’d keep sanding this until it held in the speed range I was interested in, then keep sanding until it got worse (bracketing) so I know where I was in the design.
“Somebody want to make this?” or anyone already have? Dare to fail!
[edit] Bob, I forgot! here is a little video of a series of finless and semi-finless boards we did a couple years ago. Notice he can do a bottom turn standing up straight, not in a crouch over the center of the board. Note also the bursts of speed with the finless, one trip up to Malibu, he was able to surf all the way through to the inside on a day no one else came close to doing, I credit the lower friction of the finless board in part at least! *Semi-finless means the bottom was not totally flat, but had runners or bumps of foam to do the work similar to to Tom Morey’s rail but under the board a bit. I ended up calling these lumps “lifting bodies” since they are not fins, but protruding rounded/lump ridge-like channels.
Best regards,
George
Invee feels lively and is very fast. My guy up north tested the 10’6" big wave gun in medium size and it worked better than planned (the concern was a board that heavy would not roll over onto the rail.) He said that he showed the board to Jeff Clark up there and had an interesting conversation about re-distributing the weight of the board to have more aft and less forward just so the board would turn better. I am a proponent of the inverted vee, have yet to see a flaw in performance. It is a bitch to hand shape, and the glass and sander can wreck it. There are Sway members on here who have been riding the Invees for decades and will back up the claims here. I have one of Jeff Alexander’s olllld Gemini that Bernie and Harry brought to my shop, and the vee is real deep, like 1/2"!!!
Board flex. Yeah, I will concur with you, in the low energy, low speed dynamic, the fins need to be better "matched’ to a Straight Bending board. Most likely more flex in the fins, or more rake will sync better to allow the surfers inputs (pumping the board, to generate speed,) I noticed this decades ago with the fish keels we had, the curved back keels and a “gushy” feel compared to the straight backs, which were right there immediately for you. I gravitated toward straight backs because once up to speed, they worked unreal with just enough give, or gush, to allow for more free tail movments (which change the trajectory of the board coming out of a turn.) Oh yeah, for small weak surf, I think you can have too much flex, it would be like trying to pump on a softboard, probably generating a push back “bow wave.” Would be nice to “crank it in” a little, ala Bob Tinkler.
Varial Foam- MAN I want to try some, heard only a little about it, doesn’t drink water, has good compressive modulus, and (I hear) good flex with the right skin. And, yes, we’ve done a lot of board with 1/16" cedar stringers to minimize the stringer. Years ago we ordered blanks with “glue line only” so you had a (colored) glue line for a center line, no wood, it was used to aid in shaping. With CNC I just peg the ends and run with a pure stringerless.
Hello George,
The dragger reminds me of the tail of Gus Acosta’s WaveArrow. I also recently saw a board Doug Haut from Santa Cruz shaped himself. This board has a tail which is a dragger -swallow combination.
Thanks again.
Bob
And the down rail, which Hynson got inspiration for from T-Boy,
Who is T-Boy ?
George,
We were robbed of 2 days interactive dialogue with you when the forum went down**…**
Can you explain what hydrodynamic benefit toe-in gives fins on quads and thrusters? How?
Thanks,
Bill
I can see the major side panel Invee, and maybe faintly some micros in the tail and I guees theres another forward broader more shallow one?, all running parallel to the stringer.
We’ve all seen the photos of a board in a hard bottom turn, hard on rail and the water traversing across the bottom at maybe a 25 to 35 degree angle or so. Does InVee confuse/ aerate this water flow or attempt to straight channel control it? Is there control in this “lively” feel? Is it looseness and the ability to change and quickly reconnect drive and stability?
Your rail cross section shows a domed deck into a very radial airplane wing foiled rail…how blady and tappered does this get toward the tail?
Alot of the traditionalist say keep these guns flat to panel V front (for chop and out the tail (for Control). I know the control of radial convcaves ability allow rail to hook, hold and drive when on edge… water follows the funnel, where as a panel vee would tend to cork and slideout except for reliance on fins hanging in 2 feet back,… especially in cross chop.
With Invee you are doing both the opposite and the same thing as tradionalist since two invees side by side give a center Vee…AND the rail has its own Half Vee which is like a water hook on the railine.
Things get a lilttle confusing when theres still another set of invees in the tail becoming almost like a “multi channel” bottom one would not typically associate with a big wave gun.
When I think of dramatic Vee and Invee… the older 13’ Boston Whaler hull comes too mind and one can turn those at high speed on the gunwall.
here’s the board that gave the inspiration for his invee
i’ve been riding one since the early 2000’s after having detailed discussions with Rand Hogan
looks like a quad surfs like a thruster
http://mkdesignmarketing.com/gemini/
http://www.theinertia.com/surf/riding-the-gemini/
http://www.surfermag.com/features/gemini/
http://www.lalasurfboards.com/gemini.html
First time I heard the words " Inverted Vee " was at T&C around 1986
When our boards are working their best the front 1/2 to 2/3 are not touching the water .
Maximize the efficency of each part of your total design , board and the fins designed as part of that design .
Was there a question in there for George?
Cuz otherwise best save it for your own week in the hot seat 
a pic like this is worth a thousand words!
I dont know it …know of it… not many crossections available… this looks like a single InVee (Tunnel) inside broader InVee across rail to rail and looks to blend almost radial concave out the tail…hard to tell without a straight edge
Huck
that was my response to bernie’s post above .
This posted rail shape makes me happy :-)
Hi Greg, “T-Boy” is Tom Gaglia, originally from Newport, moved to Maui and during that creative period, shaped a board called “The Rubber Band” for his friend Garth Murphy, (the board that Mike Hynson saw when he went over visit the group during the 60’s.) Shoots! I missed the 60’s, (first rode a wave in 1969,) but those Masters have since shared their stories (and design developments during those times) they are an incredible bunch of surfer/shapers. Tom is a very good friend of mine who comes up to shape at my place several times a year and he still rides a shortboard (Garth too, somtimes…ha, just turned 70.)
Hi Bob, I just saw the Acosta Paipo photos. Let me say that guy is NOT afraid to try stuff, AWESOME!!! The “Dragger” I had in mind is similar, but sould not have any foam on it, or any thick structure at all (this is why I said it would be dangerous to try.) I envisioned a few layers of glass, or maybe stiff silicone rubber or urethane. The dragger would bend VERY easily, BUT NOT flutter, that would be bad. Heck, you could even tie a rag on the corner of the board to get some benefit! BTW, check out some of Acosta’s bottom contours-!!! Being that low to the surface of the water at speed, just AUGMENTS the effect, I wished he would post on here…
…Who is next in the Hot Seat???
Hi Bill,
“Can you explain what hydrodynamic benefit toe-in gives fins on quads and thrusters? How?”
Oh man, I’ll try to be brief, I’ve thought about this a LOT over the years and I think I’m starting to wrap my head around it. Obviously someone a way long time ago figured it out, probably started soon after more than one fin was put on a board. The earliest instance I’ve seen personally was a Bob Simmons two finned board, that to this day has a feeling of being from the future/alien abduction kind of thing, creepy, the board is late 1940’s-early 1950’s yet has features we use now.
Multi-finned arrangments tend to be compromises, that is, at any given instant, one fin is doing more work than others and the other fins are momentarily “just along for the ride.” A good example of this is when doing a hard bottom turn, have a look at a photo and you will see the shoreward fin will be completely OUT of the water, leaving the share of the load on the remaining fins (in the case of a thruster, the remaining two fins.) Of the two remaining fins one is doing more work than the other. Again, in the case of the hard bottom turn, the fin furthest from shore is doing the most work, with the center fin adding a portion of the help.
“So WHY are they angled all differently?” As the focus of turning effort is put upon one fin, the slight angle (or “toe-in”,) acts as a TURNING rudder, kicking the tail over to set up trajectory of the rest of the turn. Years ago we validated this using the South African designed “4 Way Fin System” which let us change the Toe-in angle. We even tested “Toe-OUT” in the set up, surprsingly it worked well for generating down-the-line speed. As predicted the “looseness” was horrible. With the 3 fins all pointed straight ahead the board was likewise too stiff. We even tested extreme Toe-in and it was very loose but also the inherent drag was too high (picture the “Snow Plow” move that skiers use to slow down.)
All this said, I am guessing there is a second thing going on. I think the flow off the tail is NOT all straight, but flares out kind of in the radiating pattern like the fins. As the surfboard skims atop the water, the “supporting” water seeks the low pressure, which is to escape to the nearest edge of the board. As the supporting flow travels tailward, the water that “escaped” out the sides (seen as rail spray, even in straight trim, not just turning,) must be replaced by water coming into that zone, thus the radiating pattern. Of course this is just a snapshot in time, because as the board turns, the flow does NOT run parallel with the stringer but diagonal (supported by numerous pics and video of underwater surfboard shots.) This diagonal flow is called the “spray route” and it changes continuously as the board is turning and re-adjusting to the moving wave.
Articulating fins are a good concept to address the variable flow patterns. I recall a member here “Blakstah” had a system which did this but I never had the opportunity to try it. I use “rake” in a fin to allow for variable geometry. The Wright Flyer was an aircraft which used twisting wings to control its’ flight. The main function of rake is to induce bend beyond what is normally there into the fin. Any bend of course will create drag (picture the Wright Flyer bending a wing to turn,) so it is a safe bet to say “if your fins have rake, they will drag more than running flat at some point.” I should say that drag is a very necessary component to having a fin. If the fin generates lift, it will do so at the cost of drag, hence the “lift to drag ratio” of all foils.
So one last part to the puzzle. Back to that bottom turn, the shore side fin is out of the water and the fin furthest from the shore is doing the "lion’s share"of the work. Well, that working fin is ALSO BENDING, so it is dragging, MORE than running straight, and MUCH MORE than the fin that popped out of the water (water being 400 times more dense than air…ha) Picture a rider on a Head First Luge sled, dragging their foot to change direction, that is ALSO happening with our fins. Skiers do this with ski poles as well, heck WE do this too! We will drag a hand to turn, and our surfing forefathers dragged a foot to turn! This is normal.
You are right on track (no pun!) The inverted vee is lively and under control, almost like it’s riding on a soft flexy rail, I found that directionality is there, so I can run SMALLER fins, thus have less drag, thus MORE SPEED! yay.
“We’ve all seen the photos of a board in a hard bottom turn, hard on rail and the water traversing across the bottom at maybe a 25 to 35 degree angle or so. Does InVee confuse/ aerate this water flow or attempt to straight channel control it?”
That traversing water flow is called** “Spray Root,”** I learned that in discussions with a great board builder, Doug Vickery, and later I turned Maurice Cole onto the concept when he shaped at my place. Maurice and I had many a discussion about the concave (he, is “Mr. Concave” ha ha,) and the “lift” many think the concave produces. Well, really, it doesn’t. In fact we found that bottom contours forced the rails to ride deeper in the water. MC was far ahead, he even sharpened the rail’s tucked edge from NOSE to TAIL. This allowed the deep penetrating rails to “cut” through the water and stay deep. Basically the net waterline of the concaved bottom is DEEPER than a flat bottomed board*, HOWEVER as speeds increase the concave DOES lift a bit due to flow containment. Enter the InVee. As speed increases, that lift vector is not as exponentially high as we go faster. I do not yet know fully how it works to get the “feel” that we are feeling, but so far the indications are positive regarding surf-ability. One thing the deep concave boards do not do well is airs. I am thinking a deep InVee will not provide a good platform to leave the water either, so use it in moderation.
Now. The LATERAL component of the Spray Root. In a concaved bottom, the water particles moving laterally change direction continuously on their translation to the rail, because they are travelling along a curved surface. Rusty said it best, “Think about every shaping feature you put in a board, because it costs to move water.” This is so very true. With the inverted vee, the direction change (obviously,) is once, IF that, which is the part I am not sure on. My question to myself has been, “Does the lateral component of the water hit the inverted vee and get disturbed, or does it become more laminar?” Now I am suspecting the latter. Which is why I put (as you’ve graphically pointed out,) multiple inverted vees into the bottom. First, to progressively keep the waterline down in that part of the board (for holding power) and second to slightly redirect spanwise flow for a little bit less drag. The contours act to “comb” the flow. The feedback has been good paddling (low speed dynamic) and great speed (hsd.) The board also rolls over on rail well, which was the major concern some true expert big wave riders had (and probably the reason many shapers stick to regular belly/vee configs on their guns. (Note: We are seeing more concaves in big wave boards due to their success being used in the Tow Boards, mostly single cons with double concave combos of some sort.)
“Your rail cross section shows a domed deck into a very radial airplane wing foiled rail…how bladey and tapered does this get toward the tail?”
That was the challenge of that board- it took me a year to design and I wasted another 10’8"BG in the process (long story,) but I managed to get the 10’6" x 22-1/8" x 4" package to have a decent rail volume for given width. The tail-rail is not that bladey, but I should note there is NO vertical sidewall in the rail. I spent a lot of time scrubbing the correct rail shape into the pre-cut, and I also glassed it myself on the re-glass (board was glassed twice (for strength and increasing the weight,) in order to get the shape of the rail right after all those glassing laps killed it. The surfer is 145-150 lbs w/o suit, so imagine trying to keep a 10’6" x 22+ from flapping once up to speed. If I bladed the rails too much I would risk a bad oscillation mode, which I learned from making speed sailboards, where too much water will momentarily “grab” the rail/deck, causing the rider to check himself, which then changes the trim, causing another “grab” etc. This is pretty subtle stuff, but VERY distracting to a surfer in 30+ who is focusing on just trying to make the shoulder via a single good turn.
Agreed, the vee bottomed boards put a lot of unnecessary load on the fins (so the designer puts bigger fins on the board = more drag.) Minimize the fin and the board will go faster in high energy situations. (Almost the opposite is true in the converse.)
“Things get a lilttle confusing when theres still another set of invees in the tail becoming almost like a “multi channel” bottom one would not typically associate with a big wave gun.”
Yes, the attempt is to have the contours “trip” the flow to keep it attached and smooth for the rider’s sake. I can’t stand “flappy guns” (pitch oscillation.) And yes, this is my attempt at trying something that’s never been done in giant waves. I feel very fortunate to be working with guys crazy enough to give it a go. So far it trialed well, even with off-the-shelf fins, which is an accomplishment already. Stoked.
re. Boston Whaler. LOTS of those growing up here! You could turn those so hard that you could hurt yourself, ha! Smooth runners too. Didn’t make that association, but it is a good one, marine architects have been through a lot of designs, like Jeff Alexander following the Unlimited Hydros… …there’s money at stake!
Anyways, keep the rail set, and remember that concave AND invee both have MORE ROCKER at the rail than down the stringer- another plus!
Hope this helps.
Best regards,
George
*conversely a vee bottomed board has a net waterline deeper than a flat bottomed board, but it is not deepest at the rail, so SET YOUR RAIL before going into a turn!
Hello George,
Lots of Gus’ designs here - http://mypaipoboards.org/interviews/GusAcosta/GusAcosta_2012-07-21.shtml
I’m not sure he’s a forum sort of guy, but happy to communicate.
My last question - where would your fin dot concept place twin fins on a 53" board?
Bob