say you had a magic board back in your younger days, and you come to figure scince you had a few other boards in your quiver that were almost exactly the same, that what made it so good was the rocker. Now, you’re older, but want the same board scaled up. How would you do the rocker?
I know it’s hard to recreate a magic board, but say the origional was a 6’, and you want a 7’, would you use the same rocker just streached out more along the curve, or would you use a porportion to solve for a scaled up version of it?
this has been bugging me for a while, because you 're not going to stick 5.5" of nose rocker on a 4’2 grom rocket, but something porportionally 5.5" to the length of the board, right?
What gets longer is the middle of the board, as if you cut it in half, and stuck another foot between the two pieces, right? What if you took a 6’3" and a 7’0" thruster by the same shaper and set them down side by side. I’'m guessing that you’ll find that the longer board just has a longer flatish section in the middle and the location of where it’s nose rocker and tail rocker begin to kick in is fairly similiar to the shorter board, as measured from the tip of the nose and the tail of each board. No?
The general answer to your question is yes. I don't think I'd try it scaleing a 10' board down to 7', except to hang on a wall, not to ride.
I was curious if there was a mathematical formulation for rocker curves, so I tried to fit the ones in Essential Surfing. They shared common properties. All were strongly non-linear, and had highly curved transition points in rear rocker that occurred about 18 inches up from the tail. Rocker is the most problematic element in stretching or shrinking shapes, because you’ll tend to keep the curvature the same at the transition point, it will stay in the same place relative to the tail, but overall rocker will increase, slightly, from the longer region of more gentle curvature in the board.
If you want to elongate the rocker, I would measure it every 6 inches, and pick up a copy of Essential Surfing and see how Merrick and Rusty change rocker when they change board length with these elements in mind.
BTW, I’ve never had a “magic” board that had continuous rocker.
…this is a really good question , thanks for asking !
I look forward to hearing more .
Unfortunately I’ll be kinda doing what you said Bill , so …wish me luck , I guess ?
[a 9’11 windsurfer blank , to make a 7’10 " whatever ?? board ?
… still with the full nose rocker of the 9’11 blank , unfortunately , as I had to remove a LOT of the tail , where the metal inserts had been wedged , for footstrap attachments? I’m guessing?]
Easy to do. Take any of your measurments on you 6 footer and scale them, lets do the nose rocker for instance. Let’s say the 6’er has 5 inches of nose rocker. You take the length of the 6 footer in inches, which is 72. Now you divide 5 inches of nose rocker by 72 and you get .06944444. Now multiply by the new length (7 foot) which is 84 inches and you come out to 5.83333. That’s your correctly scaled 7 foot nose rocker. All the other measurments can be done using the same method.
You’ll find that if you add up the nose and tail rocker of a standard 6-2 it will be somewhere around
7 1\2 inches, roughly 5 1\4 nose, 2 1\4 tail. Scale the board to 6-10 and you’ll find you’ll have roughly the same rocker of roughly 7 1\2 inches maybe 7 3\4 depending on the waves the board was designed for. The nose rocker will come down a bit and the tail will gain the diffrence plus maybe another 1\4,
so roughly 5 inches nose and 2 1\2 to 2 3\4 tail. As the nose gets a little wider the rocker can come down a little for a few reasons.
Tail rocker will start a little more forward to keep some of the looseness in tact and because you’ll be riding up a little farther forward. This is scratching the surface. you also start losing some concave, but that’s a whole nother thread.
No width is different. With width you increase the width 1/8th inch for every inch of length you increase. So if the 6 footer is 18.5 inches wide the 7 footer needs to be 12/8ths or 1.5 inches wider. 20 inches. There’s a reason why. Look in the achives under scaling and I think you’ll find it. Takes a long time to write that one.
MaraboutSlim, just what I wsa trying to explain to a student the other day. Whether it be the 9’0" longboard or the 6’2" modern thruster, ones footing stays nearly the same. The tail rocker determines how the boards will turn and porportioning it up dramatically on longer boards would also change turning characterists. Longer rocker, longer turns
I know it’s hard to recreate a magic board, but say the origional was a 6’, and you want a 7’, would you use the same rocker just streached out more along the curve, or would you use a porportion to solve for a scaled up version of it?
InMyOpinion, you could mathematically scale the rocker to a longer board, but shouldn’t. The longer board will be meant to surf differently and in different size waves, so there will be sublte differences in the rocker flow and their relationship to other changing measurements.
But if you did want to scale the rocker up for argument’s sake, I would not change the rocker height (or depth) measurements themselves at specific points, instead I would use a ratio and proportion equation (like Greg did) to slightly alter the placement of the points. – Because the smaller measurements of the rocker close to center would be much harder to adjust such a tiny increase accurately, and you don’t want to increase your total nose and tail rocker by 1/7th. Or maybe you would, I don’t know. Instead, adjusting the placement of the point along the hull (or rocker stick) would be much easier to get exactly right because of the longer measurement. I wouldn’t want to scale in 1/7 more rocker, rather stretch the same rocker over a longer distance. – If I understood your original post. …or maybe I didn’t and I’m bassackwards. haha
You work from the center of the rocker. This is how it’s been done for a long time. I’ve scaled lots of boards using the method above. It works. As Ozzy pointed out, if the board is going to be surfed differently then that difference needs to be taken into account. If your just scaling for different size guys, it works.
It depends on why you want to go longer. I’ll assume it’s for easier paddling. With that in mind, I would keep everything in the back half of the board the same, and add the length to the front half. And that includes the wide point and the rocker apex. Don’t change the width. Everything happens from the back half of the board when you’re surfing and the front is almost irrelevant except for when paddling. So the front rocker can stay the same. When surfing, the board should feel the same except for a little more swing weight. So I say no, it’s not proportional if you want the board to feel the same as the shorter board.
well I made a 4’1 wakesurfer, and I scaled the rocker from my 6’2 to it, but haven’t surfed it yet…
It’s not going to be paddled at all, unless my little brother wants to try it, it’s like 4’1x18.5x1.5, very small, and I don’t remember the exact rocker measurements but I’ll go get them soon.
Thanks for all the replies, I think I’ve understood what I’ve asked, allthough I’m still not really sure waht ti was…
So I would take it that the main part of the deck would have to be averaged out as level, otherwise depending on the weight in the nose or tail you would get varying measurements.
ie 6"N 3"T could end up being 7"N 2"T or 5"N 4"T depending on the balance point…so level deck is the way to go?
I don’t know if anyone else does it or sees it like this. This is just the way I relate to it, and it might be bassackwards from the way you’re supposed to do it. – If there is a way you’re supposed to do it.
The only time I think or worry about the apex is when I’m considering the rocker flow. i.e. – The farther back the apex is, the more abrupt the the tail rocker will flow, and vise versa.
As many have suggested, from a riding stand point, rockers probably shouldn’t be proportionally expanded. Waves are rarely porportional and even if they were, the surfer isn’t. That is why longer boards (usually used for bigger waves) are generally narrower not wider, like poportionalizing would suggest.
Fact is, not counting nose flip, most all boards are really just somewhere around a 6’8" with some nose added on.
Think about it and try measuring some rockers. You’ll see what I mean.
