Just a not too serious belly rider project
1 Like
Nice! Keen to see how it goes.
1 Like
What are the dimensions?
EPS? Density?
1 Like
24 x 42 x 4 1/2â, eps, not sure density, from a big block I got years ago from a swaylock brah. I think was from a freeway construction site, not sure what they use it for.
Kinda getting it roughed in. Its cheap beer cooler foam, and that combined with my possibly too casual approach to shaping this has resulted in some crudeness I hope to clean up as I finish the shape. Its a prototype / concept board anyway, so next iteration, if one ever develops, will be a bit cleaner. Maybe even someday shape one from some better quality foam, but this is what I had laying about the yard, and I think it will be good for the nature of this project.
2 Likes
For cooler foam, it looks pretty good to me.
What are thoughts behind the contours/shape?
This was Ronin Bodyboards surf mat emulation:
(I like yours better.)
https://www.instagram.com/p/CrdnX-drtoj/?utm_source=ig_web_copy_link&igsh=MzRlODBiNWFlZA==
Good suggestion. Its just rough shaped so I would be bring it down, but I will pay attention to blending it a little more for the water flow. Its really just a wrap around grab bar.
I figured the semi-circle was for holding on â add a little brushed EVA to it for further improved grip.
One of my main objectives for my finless designs is minimizing drag. So, the first thing I usually see with most Surfcraft designs is any feature that would increase drag.
Design for prone boards is wide open.
I look forward to seeing your finished board.
Uhmmmmm- interesting. Though you might want to bear in mind that a very rigid emulation of a surf mat kinda misses the way a mat is used.
First off, you donât want to pump them up to where it wonât bend, a lot of the speed stems from the way they conform to the waterâs surface which in turn lowers drag.*
Likewise, in turns you wind up with a curved edge that helps get you round.**
This is gonna be interesting, like I mentioned above-
docâŚ
*This, by the way, is what Tom Morey got right with the original boogie boards. They were built to flex and thus in spite of what were hydrodynamically cobby skins they were pretty quick.
** On the other hand, those who followed Morey didnât understand this and they made them ever more rigid with hard bottoms and so forth. And instead of a rather fun thing, they became hyped items that had to be brute-forced around.
As we used to say in the software biz, âthatâs not a bug, itâs a featureâ - and they sold them on the hype of how hard bottomed and rigid they were, how that lack of flex permitted drop knee riding and other stupid pet tricks, missing the whole point of the boogies and of surf mats before them.
Me, I still miss my Newport Paipo-
Hello Doc! Yes I am well aware & was just waiting for someone to come along & state the obvious.
The design borrows from surf mats and should capitalize on the strengths of the design in trim, which is where it should be most of the time, its not designed to be a carving tool.
I started my surfing journey on a canvas mat, very little flex, and this is an offshoot of my memories of those days., combined with my input from designing & shaping my own boards for the past 15 years.
Based on my memories, and on studying video clips, the flex of a mat comes into play most during turns. I have incorporated some other design features to compensate for the lack of flex.
Whether it will work as planned or not I wonât know until I try it. I do have some other design ideas to incorporate flex, but those will be on hold until I try this and have some experience with a rigid shape first.
My main goal here is to create a fun vehicle and to use some creativity & sculpting skills to rekindle some of my childhood memories in a belly slider for my senior years.
1 Like
and yet miraculously there are people riding waves & having fun on them, go figure
Hi Huck,
Yâknow, in my old age (and quite possibly senility) I miss the canvas mats, the paipos and indeed the crudely shaped and finished chunks of plywood of my youth. With those and the low-end diverâs fins every kid had, it was all good. Not sophisticated, nothing you could brag about, perhaps, but good.
They were fun, after all, and isnât that what itâs all about?
docâŚ
George Gall offered this perspective on flex.
âGreat question. I think a LOT about Flex in Surfboards⌠âŚIâve had arguments with reputable shapers, saying âboards donât flexâ but my training tells me otherwise, in fact EVERYTHING is a spring, even a rock, even water, especially MOVING water (or You, moving across water (a relative intertial frame shift for discussionâs sake.)) First, and I donât mean to be a smart ass, but nomenclature is Longitudinal for lengthwise flex, also called Straight Bending. Bending from rail-to-rail is Lateral, or Iâve heard some call it âcurlingâ on surfboards is less understood (until the introduction of âparabolic,â or âperimetricâ stringers.) The twist, as mentioned is Torsion. All 3 bending modes are important, and I have tested and validated what I thought was desireable (THANK GOD FOR 1" WIDE CARBON GRAPHITE TAPE.) Iâve placed tape in various directions on boards, to completely/partially lock out discrete bending modes. eg. glass on 1" carbon tape at 45 deg Xâs on a board to lock out Torsion. (90 for Lateral, etc.) âThis is where I got in a LOT of HOT water with some kneeboard builders, firmly convinced the twist is what made their boards go, but in general Iâve found Torsion to be the enemyâ. Surfboards (thin ones especially,) will bog down with they twist too much. Surfboards are glass in such a way to leave them wide open for too much torsion, the cloth comes off the rolls at 0/90 since the beginning. The 0 deg, or âwarp directionâ is good for Longitudinal control (of bending.) (90 or âfill directionâ is good for Lateral control.) Most boards do not have cloth at 45 degrees, thus are wide open to twist and non-immediate rebound. You will benefit with âoff axisâ glassing, thatâs been done for decades, Iâve met success with it, but be careful, if you do -20 deg with one pull, it is suggested to do a compliment of some sort (I donât mean, âhey bro, good job,â) to counter the single offset behavior. That said, Iâve done a lot of building on Asymmetrics with asymetric layups to promote certain behaviors and to block out others.
Iâve kind of hinted at the downstroke/return stroke thing. Basically, you can break down the action of a board flexing into two operations. First, your body English is transferred into the board (board bends.) Then you unweight, and the board comes back to original shape, OS. The first transfer has a surfer in control, loading up a turn, then kind of âleapingâ off the board. At this point the surfer is VULNERABLE, being unweighted, and REALLY depending upon the board to come along with them to the next position/mode of the ride. If the spot you are leaping toward MATCHES what the board does- stoked! But if the board leaps not enough or too soon, then youâll find the mismatch to throw the timing off the remainder of a ride. (Believe me, weâve seen this here, a couple of the board builders in our area are really into flex and you can spot a killer set-up versus a not-so-killer-set-up!) Thus, the rebound energy, how it returns to OS, is VERY important.â
âHi stoneburner,
I relate. To create flex (in a surfboard) a load must be applied to it. In most cases we create flex from the rider inputs. Changes in direction create acceleration (sometimes referred to as âG-Forcesâ) in order to go in the new direction. Our bodies want to keep going the old direction, so we feel the force of change through our legs. The applied load is through our feet to the board (at 2 points.) Of course, these 2 point loads VARY fore/aft (longitudinally) and left/right (laterally.)
To promote flex in the board there are a ton of ways to do it. One of the less obvious but most common is to make a thinner board (thinking HP shortboards that Pros ride.) Board flex with respect to itsâ thickness is a cubic factor (assuming Simple Beam Theory.) For example if you double the thickness of a board, itâs NOT twice as stiff, itâs actually 2-cubed, or EIGHT times stiffer. There are other things to consider like Slenderness Ratio and scaling factors, so as you go 1/4" thinner the board is even more flexible in the next 1/4" thinner, but in general you get the idea, âIf you want it to bend, thin it out.â
To promote flex you can also use different materials, under this category Iâll also put âmaterial placement.â I alluded to what Iâve been doing (using off-axis glassing) and locking up flex in other degrees of freedom, like torsion. You can also use lower modulus fabrics, like Innegra, or higher performance bi-directional fabrics, like Carbon Graphite depending upon the goal one is seeking. By the way Carbon is an Engineerâs favorite composite because it is bi-directional, itsâ tensile strength is just about equal to itsâ compressive strength (in a viable matrix,) UNLIKE fiberglass which has tensile strength close to Carbon, but almost no compressive strength. Kevlar is like this too, but has MUCH higher tensile strength than either Glass or Carbon. In general, you can stack fabric patches where you want stiffness, and minimal, off-axis fabric where you want more flex. Likewise you can use different foam (or other cores) to promote flex. I mentioned using iFoam has been very interesting. There are other foams which exhibit good elastic properties as well.
Here is a very interesting thing that happened a few years ago, I built a board with variable flex. I was doing a bit of SUP with a couple of guys when it was small. One of the guys was Jim Weir who owns a company called ULI boards (inflatable SUPs.) He calls me over to his little Jeep and as heâs inflating it and he says âWatch thisâ and he stands on it between two milk crates and the 14 ft air-filled race board is holding his weight. Got me thinking. Roll ahead a few months and I meet Rouven Brauer (Bufo) who owns HydroFlex. So we end up building the first SUP from iFoam with NO stringer (the shape was like a wet noodle on the shaping racks, ha) and a hard external (minimal 4s glass job. Long story short, Bufoâs boards gain strength by applying internal air pressure. He has a Schrader Valve (tire valve) potted into the board and a small bike pump is used to pressurize the board. His focus at the time was to prevent dents and buckles. What I was after was to make a âfloppyâ large board and find out the behavior as I added pressure to the board. (NOTE: EPS breathes air (and water,) and iFoam breathes air but NOT water (like Gortex) and PU sorta breathes air, and water, slowly.) I was very surprised to find how much influence internal pressure has on surfing characteristics (and for SUP, paddling characteristics too.) I found that no pressure SUCKED, the board plowed in all phases. On the other end of the scale, too much pressure SUCKED as well, the board would lock in a turn and Iâd end up face down splatting in a bottom turn. But the best part was I found there was an ideal pressure for that one floppy board, it really became lively, and sprang out of turns. Higher pressure paddled better. (This is good to know for Racer boards.)
Finally, I came up with a stringer set up which mimiced the optimal flex of the inflatable board. Enter Robb Green (but thatâs another story Iâll save,) and the boards work great without having to do the pressure-proof skin and valve stuff. I liken it to the Hotrodders who bag their cars, then leave it at one setting, eventually going over to coil springs and removing all the other supporting gear.â
Exactly my thinking here. Iâm just an old guy who got sidelined by a bad hip and I am anxious to get back in the water and have a little fun doing it
2 Likes
I took a lot of inspiration from this video. Eventually I may get myself a blow up mat, but for now I just want to try this little experiment and see how it goes. Need to order some resin tho, mine went bad 
1 Like
Did you test mix a small cup of the resin? Sometimes an ambered-colored epoxy hardener does not spell doom for the batch of resin. If the resin side is crystalized, it can be heated in a hot water bath until is become liquid again.
If you remember Dwight, he preferened opaque-tinted resins for EPS boards, lots of light blues and greens.