EPS foam prices

[magentawave]

That is really cool!

How do you duplicate the rocker of a board you like? For example, I've read good things about how well the Jimmy Lewis (Super Tech, Stun Gun, World Wide) ride verses other boards in that you don't have to be on the tail to turn them, etc. If you wanted to duplicate the rocker of one of those boards, how would you do it? I know you could take the fins out and lay the board bottom down on a flat surface and then measure the distance from the flat surface up to the nose and tail but that assumes the curve is continuous and wouldn't take into account subtleties like maybe a point where the rocker is flat. I guess what I'm asking is, short of having a board laser scanned, how would you duplicate the rocker from a board you're holding in your hands?

Actually it's super easy to change the rocker. I have the rocker line penciled in on the box wall. All I have to do is just back the screws out, redraw my new rocker line, and screw the flexible MDF guides to the new line. The rocker on the and deck of the board turns out just about CNC perfect. I'm comfortable doing the rails freehand, but I've thought about building a rail jig for my router to be more precise. I just haven't thought it through completely. It would have to have a guide that sat against the rail outline. The jig might have to sit on the board itself? Next board.....

[Dwight (DW)]

....... you don't have to be on the tail to turn them, etc. If you wanted to duplicate the rocker of one of those boards, how would you do it?

Jimmy used to openly talk about his constant curve rockers (years ago). Assuming his philosophy is similar today, and knowing from personally shaping some constant curve and progressive curve rockers, constant curve does what you want.

[magentawave]

If I wanted to duplicate a constant curve rocker, would it work to lay the board on a flat surface with the fins off and measure the distance from the flat surface to the tip of the nose and tail, or is there more to it? Also, do you know anything about the rocker used on the 8-4 Naish Hokua verses a Jimmy Lewis Stun Gun or Super Tech? I'm asking because I read a thread talking about how the Hokua had to be turned from the tail but a Jimmy Lewis Stun Gun could be turned from all over the board. Do you know what the difference in rocker would be between two boards with similar outlines that would make them ride so differently?

....... you don't have to be on the tail to turn them, etc. If you wanted to duplicate the rocker of one of those boards, how would you do it?

Jimmy used to openly talk about his constant curve rockers (years ago). Assuming his philosophy is similar today, and knowing from personally shaping some constant curve and progressive curve rockers, constant curve does what you want.

[TallDude]

Rocker questions, beget rocker questions. Like DW said, constant rocker boards are going to turn almost no matter where you stand. They tend to work well on steeper waves, but can be slow on big mushers. A progressive rocker will help develop more speed, but you'll have to move back to turn harder. If you have an 8' board with 5" rocker in the nose and 3" in the tail. A 9' board with the same spec's, will have less rocker. If you ride hollow steep waves, you're going to want a little flip in the nose. More tail rocker will slow you down. I know that when I think about the rocker, I picture the break I want it to work for. On race boards, I picture the swell frequency and depth of the trough, or lack of.
As far as measuring a board, if i have it in my shop, I usually use a laser pointed length wise about 1/2" about the board as it lays upside down. Then just use my tape measure, and check points about every 4 to 6 inches. Sometimes when I demo someones board, I'll lay it down on a picnic table and use my tape measure to measure the rocker from the table surface to the board. I can then make a mental note as to what that rocker surfed like. Now add a bunch of V to the tail and you have more questions. 

Channels leave me baffled.

[magentawave]

That all makes sense. Thanks. It's amazing how two seemingly identical boards that share the same outline, thickness, rails, fins and bottom, but have different rockers will behave entirely different. A whole book (or thread) could be devoted to rocker.

Channels and concaves running out the tail are interesting to me and especially the kind of channels and concaves that get progressively deeper in the last foot or so that have flat spots on each side of them. I wonder if having the flat spots on each side coupled with the channel or concave enables the board to have the looseness and forgivingness in late takeoffs of a board with kick in the tail but the speed of a board with flatter rocker in the tail?

Rocker questions, beget rocker questions. Like DW said, constant rocker boards are going to turn almost no matter where you stand. They tend to work well on steeper waves, but can be slow on big mushers. A progressive rocker will help develop more speed, but you'll have to move back to turn harder. If you have an 8' board with 5" rocker in the nose and 3" in the tail. A 9' board with the same spec's, will have less rocker. If you ride hollow steep waves, you're going to want a little flip in the nose. More tail rocker will slow you down. I know that when I think about the rocker, I picture the break I want it to work for. On race boards, I picture the swell frequency and depth of the trough, or lack of.
As far as measuring a board, if i have it in my shop, I usually use a laser pointed length wise about 1/2" about the board as it lays upside down. Then just use my tape measure, and check points about every 4 to 6 inches. Sometimes when I demo someones board, I'll lay it down on a picnic table and use my tape measure to measure the rocker from the table surface to the board. I can then make a mental note as to what that rocker surfed like. Now add a bunch of V to the tail and you have more questions. 

Channels leave me baffled.

[TallDude]

Channels usually increase speed but tighten the board up. You're supposed to add more rocker if you have deeper channels. I've never surfer a board with deep channels so I don't have a feel for it. The complexity of channeled and deep grooved board designs seem like they trend towards the gimmicky side. I got to imagine all but the most experienced shapers are just shooting in the dark. They work well on high speed boat hulls, but surfboards?

[magentawave]

I dunno. I've never had a board with channels either. I too wonder if they are gimmicky, but water following the path of least resistance makes sense, so perhaps channels do. Contract shapers and glassers are paid per board so their incentive is to mow and glass a quickly as possible so I wouldn't be surprised if they have a large part in keeping the channel down. A shaper told me last year that his boards with lots of channels and weird stuff were taking forever to get glassed. He finally asked why and they told him they didn't like working on his boards because they were too much work. When he started offering more money per board he started to get them back on time. The CNC shops around here charge more for weird stuff like channels because they said it takes more time. I tell ya, it's a conspiracy to keep the channel down, man!

Channels usually increase speed but tighten the board up. You're supposed to add more rocker if you have deeper channels. I've never surfer a board with deep channels so I don't have a feel for it. The complexity of channeled and deep grooved board designs seem like they trend towards the gimmicky side. I got to imagine all but the most experienced shapers are just shooting in the dark. They work well on high speed boat hulls, but surfboards?

[supuk]

Take a look on shapers.au they have a manual shaping machine all so you can swap out foils on.

[TallDude]

That's pretty pricey for a fancy welded jig. It looks to small for a SUP anyway.  I like my cheap box. The art is in creating custom router guides and jigs for each of the cuts on the board.