As a mechanical engineering teacher and long time surfer shaper i was really interesting on surfboard flex concept. First mechanical basics learn you that you need flexural momentum to flex something. When you surf distance between action line of opposit forces are too low to create sufficient flexural momentum wich can flex noticeably flex a fiberglass surfboard. Feet are more or less over water pressure. You can have some flex when water hit nose while you push on back, late drop and some cut-back, projection concept is a myth, this can be demonstrat with some formulas …
But i made similiar boards with different tech and stiffness and they don ´t feel the same.
I found that board with a hard deck feel the stiffer even if they are not the stiffer statically.
I have the only mechanicaly viable explain of surfboard flex here by benjamin Thompson. Surfboard flex is a dynamic problem of vibration. He show a way to measure resonant pulsation of board and key to compare. It work.
This is a pretty neat thread to read and it is something I have been trying to make sense of recently in understanding why some boards feel really good to ride and others do not.
Definitely every board has a certain amount of flex and for each design there is a right amount of flex to make the board ride right. I have a two crows 5’6" miniS that has no flex and is awesome, one of the best boards I have ridden.
I also have a 5’11" firewire unibrow, my only non-local board, and that board flies and feels great when it is overhead and fast. I have tried the same model a little bigger, so it had more volume and much stiffer, and it was horrible. The right flex on that board and it feels like the response you get from a sports car driving through the mountains on tight roads.
Also, I am not a great surfer, I make it out 3-4 times a week, and I do my best. I imagine most of you have boards older then I have been surfing.
I will say this I can feel the difference, I don’t think a fancy board is going to make me a better surfer by any means, but it sure feels better when I am surfing. I used to play guitar, and Jimi Hendrix, would sound like Jimi Hendrix on a Jc Penney $100 guitar made of fake wood, but I am sure he would have a better time playing on a nice Fender.
I am an engineer, and not in the surfboard industry. My motivation is to have a good time.
To summarize I think every board flexes, there is a certain amount that is advantageous depending on the shape and intended ocean conditions, and pro shapers are doing some cool shit in making boards.
Several at Sways have suggested that small changes in rocker can make a big difference. True or False? What if a dynamic change increased rocker by 1-2 inches (or more)?
As surfboards are classicaly build, i don’t think that rocker increase by 1 or 2 inch while you turn.
There are many structure engineering to flex while they work. Many for reduce vibration problem that create destructive pic stress in materials.
Body boards are build to flex to increase turning ability, they are flexible and bodyboarder create flexural momentum with is arm on one end and body on other end. Surftoy made bodyboard in fiberglass, they didn’t work so well, they were considerably stiff.
I think too much flex might be bad. But honestly, I haven’t ever tried a board that flexed too much. Maybe if a guy sold someone a single layer job that bends like a pretzel - then yeah it would suk! But a bit o flex is actually good thing. It’s good for board and it’s good for me.
For the most part, I agree. However, there is little doubt in my mind that the overall rocker of the Morey-Doyle (pictured earlier) increased by a minimum of 1.0 inch, depending on the amount of centripetal acceleration.
This is not a challenge to your credibility. But, have you (anybody) measured the change in rocker of stringerless vs. stringered surfboards, resulting from the force associated with centripetal acceleration (e.g. 2G, 3G, 4G)? I would be very interested in seeing these data.
Obviously there are several variables to control/consider: rider mass; force distribution and location; board length, thickness and shape; foam density and glassing schedule.
But for purposes of relative comparison and research, three rider weights could be used (68 kg, 80 kg and 91 kg). Board shape/length/width/foam density/glassing schedule could be fixed and thickness varied. This could be done for several board lengths (e.g. 1.7, 2.0 and 2.3 m).
I think the hard thing is that we all “feel” differently and what one surfer likes, another might not like at all. It’s hard to nail it down scientifically when human feel, preference and enjoyment come into it. Doesn’t stop some people trying though. Good luck to them
Dunno, but those morey Doyle’s were not very maneuverable at all.the one I rode cruised in a linear fashion ok, but it had no responsiveness at all. It wasn’t something I’d want to own.
I owned a stiff hard over glassed pile -I sold in two days! I think too stiff -too heavy = bunk. Nothin personal, but there ya have it. It’s the truth! Thick / heavy boards are terrible.
It’s one thing to have a nice strong / light glass job, and it’s another thing having a thick f’n heavy pile…that’s just my take. And I really did sell my new custom bcuz it had no life, no responsiveness, no stability- no nothin. This is why I think light/strong board with sum flex are better.infact, that’s what I’m try n to build right now! Back to my pbr! beer is good sometimes! Ltr team PBR PABST BLU RIBBON
Again, a lot of personal preference comes into play. If you lived where the only waves were small, full point style waves a heavy longboard would be much more practical than a light weight shortboard. Its a bit silly to just say thick heavy boards suck.
It’s not silly at all - they suck. Real thick heavy glassed board’s are lousy. atleast, that’s how I feel about it. And no I don’t ride huge waves, but even in small waves a lighter board’s better. That’s just how I feel about it.
FYI - I bought a custom board that was thick / heavy glassed, and I took it out in sum med size waves- it was terrible. The wave would not allow the board to glide-let alone turn…I sold that board in two days and got a light/strong board - then caught tons of waves. If a heavy glass job is better-howcome the lighter board worked better? I also surfed a point break on a pretty light short board-it worked perfectly. I dont need weight. Maybe if ur out at Mavericks you might want a stronger heavier board, buy it should still have sum flex, right?
Beerfan- read between the lines…I think strong/light board’s are better. Ride what you want. I’m saying I dont like thick heavy glassed board’s.
I should let you try my first board I glassed -it’s heavy! It also isn’t very responsive. I thought heavier glass were better. But later-even the gentleman at the supply shop says I put too much resin on… you don’t want tons of resin in ur cloth - you want lighter layers. Atleast that’s what I was told by the man at the supply shop. So don’t say it sounds silly -when I had real experiences with heavier glass jobs. I can say it sounds silly that you believe weight is going to make you surf better-it wont. You should be able surf a board that’s light or heavy, right?
how can anyone think flex does not affect the ride??? ride the same shape in different constructions and the ride is different. VERY NOTICABLE. for riders way less talented than pros. stiffer is better for some conditions, styles of riding and more flex is better for others. not just the amount of flex but the type matters as well. again its about wave conditions and rider preference…
put half your board underwater and hit the half sticking out of the water - you will see how little force is required for a significant amount of deflection.
for a flex fin, push your board sideways in the water emulating a turn you can see how much the fin flexes with a force way less than during a turn riding.
for the ‘twang’ effect of a flex fin or flexy board, its seems to me that it is not as much about rebound from the flex propelling you forward as it is the flex allowing you to get in a more powerful part of the wave. flex stalls your motion some (and allows you to grip to the wave better) then you feel a burst as the curve flattens and you zoom forward out of the stall.
I remember reading somewhere in the last few years that Skip Frye once said that a board was its peak of performance right at the moment before it would delam. I interpret that as the idea that boards get really “worked in” over a period of time and start to flex more as they age. To me it makes sense, as I have had lots of bords that work perfectly for many years, then at some point start to feel “dead”. I think they no longer have any spring left in them.
As someone who surfed a longboard for a few years before switching to light weight composite boards I can say both have characteristics I like. Just because you like one doesn’t mean you can’t enjoy the other. I’m sure there’s a formula that explains it
Softboards make like body boards flex a lot more than regular fiberglass boards. Is it a good thing for ride ? I don ´t know. Some like, some no.
Boards i like more were always stringerless “flexible” boards with “soft” top, à top wich can dent. So flex is important for the feeling of board but i think it´s a vibration problem “dynamic reponse” and the projection from recoil after turn a negligeable effect with actual stiffness range of common surfboards.
**well blow me down---------- there are some on here that actually believe that you can take a backsawn piece of timber and place it on edge in the perpendicular – and then believe it will flex. **
Back to my pbr! beer is good sometimes! Ltr team PBR PABST BLU RIBBON