Flex seems like one of those mysterious, psuedo-surf terms that isn't really measurable. I've experienced it in a couple different boards but someone said best on here that you feel it the most when it's not there. With that said, where do you feel the most flex on the board and where/how does it affect you on the wave?
I have been surfing for 40 years, and this still has me stumped. LICrew wrote an earlier post about how the board will harmonize with the wave on a vibrational level if surfed properly. For me, I can feel the flex in different fins and how this affects the board a lot more than the flex of the board itself. I have been riding old boards the last few years, except for the fish I made, and it was glassed with epoxy, so it doesn't have much flex but it still rides great for the waves I designed it for. It could be faster if it flexed more when I pump it down the line for more speed, but it is pretty darn fast as it is. I am going old school fiberglass on the hplb that was just shaped, so I can feel and play with the flex on some juicy waves on the big board. Good question bro!
Flex is a very important part of surfboard performance but as you say, ClemsonSurf, it is not measurable. I've been playing with flex for years building a surfing boards with laminated bamboo stingers, carbon fiber stringers, stringerless, parabolics, flex tails, variable glassing layups and laps, strategically laminated areas with different flex modulus epoxy resins, even built and embedded a stinger with adjustable compression spring in the board... There are 2 main things I learned through all the experiments. 1. You don't want a board that is stiff with no flex (most pop-out contructions) 2. You don't want a board with too much flex and loose like a noodle. It plows water when flexed and bogs the board down. Flex should be gradual and evenly distributed along the length of the board to fit the curve of the wave at various angles. It should also serve as a "rebounding mechanism" and load up with potential energy when flexed and transferred into kinetic energy when released - providing a little "pop" out of our turns. Wood is a great material for natural flex patterns but most wood centerline stringers have knots in them which mess with the continuous flex, also providing a weak point in the board. Wood stringers are best as parabolic where they can twist and bend, providing a nice torsional flex, bending to the wave... I could go on an on but I have to go. ~Brian www.greenlightsurfsupply.com Shape Your Surfing Experience
definitely something that's probably unquantifiable. the quote above really sums up how i got on to the concept of flex in boards. i had a pair of hand shaped eps/epoxy boards a few years back that just felt "dead" under my feet, one was a copy of a pu/pe board that was magic for me; there was no "pop" out of turns in either of those boards, while the pu/pe seemed to almost go where i wanted it to w/out conscious thought. when discussing this sensation w/ some more knowledgeable friends, i concluded that what i was missing was the flex of the board. i've been gun-shy of boards w/ eps cores since. flex is something that's undeniably important in a good board, but it's hard to really explain how or why (at least for me).
This is a super complex and difficult topic to discuss… and one that everyone is not necessarily in agreement on. Like bottom contours, most of the “evidence” is anecdotal, and not empirical, so in that absence of data we can only try to apply theories to fill in the blanks. Here are a few theories I put a lot of confidence in: A board’s flex is determined by a combination of design elements and materials. To dial in flex, you have to have both variables in mind. For example, things like concaves, channels, and domed decks stiffen a board. Flat bottoms and flat decks increase flex. Thickness and foil effect flex. Thicker boards, and boxier rails, stiffen a board. Thinner boards and thinner rails allow more flex. The nose-to-tail foil of a board… the tapering at the ends (or lack of it)… determines to a large degree a board’s flex pattern. Flex is less important than “flex return”… the ability of a board to spring back to it’s original form when the load is released. Paper is very flexible, but has no flex return. All boards have a frequency… a vibrational flex/return pattern… that the rider needs to use in order to get the most performance out of a board. Materials, design, and the construction methods used to build the board alter a board’s frequency. None of this is my own theory. All of it comes from somewhere else, applied to surfboards. There’s TONS more to it, but these are some of the basic principles I use to achieve a desired result. Where do I feel flex the most? When pumping, in the pocket or tube, and on bottom turns (actually any hard turn). Shorter, thicker boards, like fish, don't create much leverage, so I don't feel much flex on them. Same thing with big, heavy, three stick logs... very little flex on my boards, and I don't need it there. But on a hplb or hpsb, I do like a degree of flex, and design my boards as such.
you want to learn about flex, ride a soft top in some sizeable surf. Cranking off the tail you can actually see and feel the front half whipping all around. Insane.
I will summon him. Roy Stuart or Roy Stewart (I spun around 3 times in front of the mirror in the dark while typing this.) I notice it more on a LB when I'm doing something wrong and have noticed it on a SB like you said at the bottom of a turn when you get that burst of speed you were talking about. So are we talking flex like a diving board, a twisted spring or a combination of the two? I can see it two ways, sort of a torsional flex along the stringer like a twisted spring being flexed at the fins. I assume that small rebound could give the je ne sais quoi that we're talking about on a steep wave. On a fatter board I think you experience the diving board flex. Both examples seem to be at the tail 3rd of the board rather than the whole length of the board.
Imagine a full rail turn... depending upon where your feet are and how your weight is distributed, the foiled ends of the board will cause it to flex like a bow, with the ends flexing most. With one foot over the fins, and the other about 2/3 up the board, both on the stringer, means the noseward 1/3 will be flexing the most, because your feet are the fulcrum, with the area between your feet flattening. It's the flex and rocker outside of your stance that determines the radius of your turn.
i think i'm gonna try dis...just so we on same page do you mean a 'softop' board by surftech or a softboard type softtop...and thanks in advance for this fresh idea....
I am designing a 9'3" hplb. The blank (it is pu foam, not eps) has a single stringer 1/4". It has lots of rocker and foil front and back. Mostly flat and 50/50 rails in the middle. I want it to flex, but not go crazy on good waves in the chest to head high range. How do you modulate the flex so it doesn't try to bounce you off on a good size wave on the bottom turn. I have concave up on the front 1/3, and vee on the last foot. Flat in the middle. So I think it should have decent flex, but now that I am reading this thread, I wonder if I should tweak it before I lay on the glass. I know....bend your knees! But, it is nice to have a clue as to how it will handle when it really gets up to speed.
I feel flex when I bottom turn an old clapped out, mushy deck PU board. Feels like I tapped the brakes. No squirt or not as much squirt. It's because more bend is being put into the rocker under my feet from my weight and slows me down a little. Straight is fast and curve is slow with overall rocker. Especially under my back foot on a shorty where it wears out the fastest and where I set a rail from, toe side mostly for me. I want my boards to be stiff and not flexy end to end. And not too bouncy like those PVC sheet foam 1lb. core stringerless tufflite boards which I have heard to be described as "too stiff" which I don't feel when I'm on one. They actually go pretty good far as I can tell but the hollow feel is not my fave.
+1. First time I rode my first coil, which is designed for better waves and much more foiled out in the tail and the rails then my daily driver, the flex through me off. I felt it most coming off a bottom turn. Had more spring out of the turn then the board I had been used to at the time. It took me a session or two to dial into it. My daily driver coil is a short disc shape with lots of volume taken to the rails since I'm heavy. Has much less noticeable flex characteristics. I just stripped the glass off a board that had more than 1/2 the deck de-laminated. Talk about flex. When I would paddle out, if I snuck over a wave that was close to breaking, it torqued the foam just right and you could literally feel it bending under you. It's a wonder it never actually broke. I had a Chinese pop-out for a while. Very stiff. No perceivable flex at all. The glass on it was bizarre. Kind of brittle. Despite being constructed poorly, and having no flex, I have to admit it actually surfed well. Guessing the shape was a copy, but I got used to it having very little flex. Only really noticed it when I would switch back to another regular Poly board. They felt more "alive" to me. I wonder how much my weight attributes to me being able to really feel a boards flex. I'm 215-220 lbs, and I can really load up on a turn. I feel like the flex helps slingshot me out of a hard turn. If I were 70lbs lighter, I might not feel it so much.
One important property of a modern surfboard we often overlook is flex. This is now a hot topic in surfboard design. Surfers are starting to understand how surfboard flex affects our surfing and which design characteristics increase flex memory. Shapers everywhere are responding to this increased interest. Flex allows your surfboard to build energy through turns when the surfboard's materials change shape. Picture this sequence: You drop into a fast, steep bottom turn. As you do so your surfboard's foam will bend into the turn. This results in more rocker and stored energy. As you come out of this turn and aim for the lip the foam snaps back to its original shape, releasing the stored energy and shooting the surfer out of the turn. A seasoned surfer will turn this burst of energy into acceleration, propelling himself into the next maneuver. While the flex characteristics can help your surfing, creating a surfboard design with flex in mind presents challenges. First, the surfboard must walk the line between flex and strength. Secondly, after repeated compression and expansion, a surfboard's traditional wood stringer will weaken, giving it a "dead" feeling. The recent emphasis on flex resulted in questions regarding stringer placement. A board with a center stringer will be stronger and less flexible along the center. However, its rails will flex and wobble which can cause the board to slow. This is called torsion flex. The closer the stringer is to the rail, the more strength or spring it will have along its perimeter which is where the board primarily makes contact with water in turns. It also supports the rail to maintain more of its original rocker shape while the flex comes from the center of the board. So now that you know shapers are experimenting with increased flex memory on their new surfboards, perhaps it is time for you to do some experimenting yourself. The idea of springier surfboards accelerating better out of turns sounds great, but can you use it to your advantage? I've been working on a few different flex patterns. One is the Incide Blanks with a carbon "Brain" within the board. Feels a lot like a wood stringer, but will probably keep its pop longer than a wooden stringer which slowly loses its recoil. Also been doing some more of my Dissect series with no stringer but many glue lines to more evenly distribute the flex. Some have a concave deck, some have a high density foam glued within the blank. http://barrysnyderdesigns.com
An area that I've thought of for designing a board with flex that is wooden and has a tapered profile is a concept I refer to myself as a foiled torsion box. Yes laminated layers which represent the rail design and the internal framing... Almost identical to Roy's construction method, but instead of laminating the board to the bottom rocker dimensions rather laminated it to the desired deck curvature, then using a foiling jig which drives a straight cut router but, one would be able to thin out the nose, and tail as desired. Once foiled, finish the bottom with anther lamination. Then I think it would flex, but some problems may arise during the router foiling process..
