Hey Bill
I’m still a little confused about where to measure rocker from, some say apex some say centre point, some say level deck, upside down, floating on the water, I don’t know…confused, confused, confused…
Can you help clear this fog for me…
I made it clear as mud, didn’t I. I say measure from the center like always. I only meant to refer to the apex as a way of visualizing the rocker flow.
{Edit} Here you go Hicksy and DeathFrog. -Rockers- {/ediT}
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Along the same lines, where do you measure the nose and tail rockers ie 6" nose, 3" tail, at the balance or the centre point of the board?I’ve got a really thick blank so there is no real rocker preset into it, I’ll have to mow it into it…
Aloha Hicksy
Measuring rocker is way more simple that everyone makes it. There is only one place on the board that is always in the same place regardless of length, thickness, weight, balance, etc. and that is the center.
The center is half the measured distance along the bottom of the board. It has nothing to do with balance, Apex or anything other than that it is the Center. To locate your rocker stick at the center is also simple but must be done carefully. Whatever you do, don’t balance the stick.
Carefully place the stick on the center point of the rocker. Gently press the rocker stick down exactly at the center point. Eventually you will press hard enough to level the stick and give an accurate nose and tail rocker read. But if you push too hard you can flatten out the rocker and skew the nose and tail rocker measurements.
The only way to get accurate rocker measurements is by using this “press” method. Even if you are in outerspace, where there is no gravity and no atmosphere, you will get an accurate mesurement.
But be attentive. Tiny chunks of foam under the stick will throw things way off. A knot or bump in the stringer near center can throw it off. A heavy ended stick can cause you to press too hard to level it and throw it off. A bent stick can throw it off.
Once the stick is leveled to the center point, it will create the boards “horizon”. This straight line is perpendicular to the Zenith at the center of the board, all rocker measurements can be taken from it. This is the only method that can be used across all boards, nations, languages or cultures, to insure a consistent standard of measurement.
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Measuring rocker is way more simple that everyone makes it. There is only one place on the board that is always in the same place regardless of length, thickness, weight, balance, etc. and that is the center.
how about a laser level from the hardware store and a clamp to hold it tangential to the center point.
It is WAY easier to carry around and harder to screw up, and you never have to worry about how straight it is. It is only as curved as the gravitational field allows.
Thanks for that Bill, maybe that explaination should go in the Swaylopaedia.
again thanks, now I have a better grip on things…
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how about a laser level from the hardware store and a clamp to hold it tangential to the center point.It is WAY easier to carry around and harder to screw up, and you never have to worry about how straight it is. It is only as curved as the gravitational field allows.
A laser would be great if there was a way we could get it
flush to the surface of the foam at center
tangential at the center
small enough that you could pull a measurement 3" from the center.
Bill, using your method of rocker measurement, will you get the same measurements regardless of the position of the blank? This is what has always puzzled me. Seems that one would get different measurements because the balance of the straight edge is controlled by gravity (i.e. it’s parallel to the floor) but the nose and tail of the board can be at different distances from level (i.e. the ground), depending on how we place the blank/board on the stands. So if the straight edge (or laser beam or whatever people are using) is always parallel to the ground, the distances measured to the blank are going to change if the blank moves.
It seems Roger Brucker(cleanlines), Jim Phillips and Rich Harbour feel it’s simply impossible to measure rocker accurately. See the thread below and your comments would be appreciated.
http://www.swaylocks.com/forum/gforum.cgi?post=181410;search_string=rocker;#181410
Aloha MaraboutSlim
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Bill, using your method of rocker measurement, will you get the same measurements regardless of the position of the blank?
Yes. Even like I said in outer space. Try this. Hold the blank vertically with one hand on the deck and your other hand on the rocker stick. Squeeze them together right on the center point. Now rotate around in any direction you like. The measurement won’t change unless you press off of center.
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Seems that one would get different measurements because the balance of the straight edge is controlled by gravity
Read again, I specifically warned that you DON’T balance the stick. You press the stick. Gravity is not your friend here. You are creating your own “gravity” relative to the board, not the earth
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It seems Roger Brucker(cleanlines), Jim Phillips and Rich Harbour feel it's simply impossible to measure rocker accurately. See the thread below and your comments would be appreciated.
They are all fine shapers. I don’t know why they would feel that way. I have no trouble measuring rocker and neither will you if you follow my instructions. Try it, 5 minutes from now you can post an opinion. You can use my system on any board, or blank. If you can’t press the stick accurately and also take measurements every 6", just try taping the stick at the center. This will also reduce the chance of flattening the blank if you press it while it is on the shaping racks. The center area, rocker curve, is usually a shallow enough arch that the stick isn’t going to teeter totter around and produce all kinds of false readings. Like I said before. It is easier than you think.
Measuring the tip and tail is easy. Measuring every 6 inches poses a small problem. Do you measure 6" along the stick or 6" along the board? Doesn’t matter a whole lot as long as you use the same system each time. I measure along the stick.
This could be a problem when transfering data over to a shaping machine. It depends on how the software views the board.
How precise is “exact”. Well I can measure rockers to a 1/16" and shape them to a 1/16". Is it necessary for most boards. Probably not.
Can the glass effect the outcome. Yes.
I find there is a random drift of around 1/8" at the tips.
Will cure and aging also effect the measured, original rocker. Yes.
Can rocker be accurately measured. Absolutely!
Can boards be regularily reproduced with exactly duplicated rockers. Yes!
Not always consistently. But definitely often enough to recreate magic boards or ones that are as good or better then the previous one being copied.
Blanks are living breathing things. Especially big ones. I often rough them and let them sit to breath, sag, spring, twist or what ever they feel like doing, before finishing. You have to continually check rocker measurements during shaping and glassing etc and adjust it accordingly.
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Read again, I specifically warned that you DON'T balance the stick. You press the stick. Gravity is not your friend here. You are creating your own "gravity" relative to the board, not the earth
Thanks! That’s the key point I was missing.
I’ve been using a laser level for years. Just balance the board on your stands & mark center with a pencil. Slide the board back & forth until the center is the highest point above the floor. Set up your laser & tripod (or a stack of books on a shelf) so its looking down the board & just barely shining on your pencil mark. Its hard to see in the photo, but I think the red horizontal line is visible on the back wall & maybe on the tape measure. Here, I’m measuring rocker at +12" from center…
Laser levels are less than $30.
Yes, Billy is correct in measuring rocker. The only thing I would add is to mark your rocker stick at it’s centerpoint and match that mark with the centerpoint of the board. This makes it very easy . You have to only press very lightly and sometimes not at all. The best rocker stick (for me) is a piece of aluminum L metal. use an 8 footer for small boards and a 10 footer for long boards.
Also remember that bottom rocker can only be duplicated with a rocker template if the shaper knows the original tip of nose and tip of tail measurements from the original board. This is where the
rocker stick- at -the -center -of- the-board measurement method is so handy as far as having a common starting point.
aloha, C
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I've been using a laser level for years. Just balance the board on your stands & mark center with a pencil. Slide the board back & forth until the center is the highest point above the floor. Set up your laser & tripod (or a stack of books on a shelf) so its looking down the board & just barely shining on your pencil mark. Its hard to see in the photo, but I think the red horizontal line is visible on the back wall & maybe on the tape measure. Here, I'm measuring rocker at +12" from center...Laser levels are less than $30.
Benny, you one-upped my idea.
Nice work.
Thanks, Blakestah. Last time I posted that I got a nice comment from Paul Jensen.
Nothing like encouragement from the deep thinkers on here to keep us garage guys inspired 
I agree cantellya. I thought everybody did it the way Bill was talking about.
My only preference is using a pencil laying on the board 2 or 4 inches away from center to act as a sliding wedge, perpendicular to the stringer with the rocker stick (for me 1/2" alum. chan. - straight, doesn’t bend or flex) laying on center and the pencil. I slide the pencil backwards and forwards until the rocker stick is perfectly on center. Then I just measure with the tape or square and be careful not to bump the stick off of over the stringer while measuring the rocker. The board doesn’t need to be level. Just the way it is laying on the shaping stands will work. But for this to work, the rocker stick can not be balanced.
(I am just very careful to use an aluminum channel that won’t flex or droop down at the ends from gravity, throwing the accuracy of the rocker measurement off.)
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Yes, Billy is correct in measuring rocker. The only thing I would add is to mark your rocker stick at it's centerpoint and match that mark with the centerpoint of the board.
snip
Aloha C
True, you can balance the stick but I intentionally didn’t mention it because too many people seemed confused about the “balancing” method of measuring rocker. And I didn’t want my method to be confused with that other one that wasn’t functional.
I mostly use a 6’ stick. Too short to balance anyway. I have inches marked along the stick. If I am measuring a 7’ for example I simply grab the stick at the 3’6" back from nose point. Press it to the board with my left hand and with ruler in right hand square the end of the stick to the boards tip, sliding the stick back or forward till the 3’6" point becomes the center. I don’t need to pre-mark, measure or find the center. The way I use my stick the measuring of the rocker also finds the center, it is all in one process.
I use the 6’ channel aluminum strip because it is so light it rarely effects thin boards. It is short and easier to swing around the shape room. I do have an 8’ strip but I rarely use it.
I need to measure the rockers quickly and easily. I don’t want to create a big set up of lasers, shims, wedges or hassle with finding balancing points. I just grab my stick at half the boards length, press and slide it on the board and measure the rocker at any point I can reach out to. So simple, so fast.
I always develop tools, systems, procedures and techniques that can be easily brought into a production environment where time is precious. I don’t create ways of doing things that are complicated, nerdy, idiosyncratic or “mine” just because I have the time or them make me feel important or cool. There are too many other important things to spend the time on. If you can get the same result faster, redeem that time and use it someplace where it will produce greater gains.
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Also remember that bottom rocker can only be duplicated with a rocker template if the shaper knows the original tip of nose and tip of tail measurements from the original board. This is where therocker stick- at -the -center -of- the-board measurement method is so handy as far as having a common starting point.
aloha, C
Unless I misunderstand you, I don’t agree at all with your comment here. If you have a tangent line (rocker stick on center) you can measure down from it in 1" increments and make or follow any curve you like. Rocker templates aren’t necessary. And they certainly aren’t the only way to duplicate rockers. Of course if the shaper is not skillful enough then templates might be a big asset. If one can’t sculpt accurately, then one may need to press the clay into a mold to get the results they want.
This is one of those interesting new dilemmas. The original sculptors (shapers) had to do it by hand the hard way. Some still do. This filtered up only the best sculptors. As molding and automated processes come into existence sculptors with much less skill can enter the game and the filtering process no longer exists. Are they sculptors? shapers? Maybe only designers? How do we define the craft and preserve the right words such that those words properly describe the skills and talents that one would expect. There are many “shapers” whom the machines have improved their crude skills at sculpting. It that bad? Maybe it is great!
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Quote:Read again, I specifically warned that you DON'T balance the stick. You press the stick. Gravity is not your friend here. You are creating your own "gravity" relative to the board, not the earthThanks! That’s the key point I was missing.
So MaraboutSlim
Did you go measure a board? Can you attest to whether or not a boards rocker can be measured accurately? It would be nice to dispel the myth that they can’t be measured.
Of course shaping or duplicating is a much greater challenge. But I am pretty sure anyone can measure them accurately. What do you think?
Thanks Bill. I don’t have anything as light as a blank here to attempt holding it in the air to prove that even that will work, but I put a yardstick on a board and I can see it working fine if I hold it in place. Thanks for telling us about using a shorter stick - that seems easier to hold and measure at the same time. Did you read the other thread? There were some interesting ideas about simply using thickness to arrive at the correct bottom rocker (when top of board is correct already: something it should be since we aren’t to take much off the top of close-tolerance blanks and can order them with any rocker we choose). This method would also not matter how we position the board on the racks or how many times we move it around. With this method, foil begets bottom rocker instead of shaping rocker in and getting the foil that results.
Hmmmmmmm…
I am not sure it is generally practical to design a boards bottom rocker around the strength of the foam on the deck.
Certainly we should preserve that stronger foam on the deck of the blank where possible and make sure we are using blanks that are proportioned properly so that we can do so.
If one is shaping a ton of boards that are near duplicates of each other then choosing a blank that has a perfect thickness proportion will allow a shaper to glue up the blanks according to the deck curve and have the blanks thickness perfectly map out the ideal rocker. This is the way Clark glues blanks. They do it by the deck curve. If you send them a bottom rocker for a blank, they transfer it into a deck curve and glue the blank deck up. Forcing the foam to match the stringers deck side. This will often create odd looking decks, but cleaner bottoms.
If you are shaping all kinds of different boards every time you shape and aren’t popping out a bunch of near duplicates, then you need to think in terms of bottom rockers and let the decks land as they may. Not that you shouldn’t take concern for the deck strength and therefore take as many cuts as possible off the bottom, rather than the deck, but you can’t let that issue dictate the bottom rocker. And you may not be able to order enough blanks to cover all options and have customer deck rockers put in them all and then struggle through all the whacky bottoms that might create. Whew! That is scary just thinking about it.
Bottom rocker is the core of any good board. It is the backbone around which all other parts of the design must relate. I don’t have time now but someday I will try to explain how I wrap the bottom curve around the board into the deck curve in a simple step by step process that guarantees a high degree of harmony between all parts of the board.
Many blanks don’t have the thickness flow and proportioning that will allow the bottom to not get all whacky once the deck is glued up to the proper curve of the finished board. While the deck may now be stronger, the bottom may look like as sea of waves and bumps. Many shapers wouldn’t be able to handle this and arrive at a clean fair bottom with the proper arch. A well made and proportioned blank won’t create this problem. But not all blanks are that well proportioned. (see the 12’8" thread)
Additionally, production shapers and ghost shapers may get lazy and simply not get the bottoms right if one were to hand over blanks with lumpy bottoms that also needed more or less curve cut into them here and there. Therefore, it is often safer to give them clean bottoms and let the decks land esthetically. where they may. If the deck is a bit off esthetically, the board might not look as nice but it may still ride decent if the bottom curve is correct. The reverse may not be true.
Assuming there is enough thickness in the blank to shape a Short Board it probably shouldn’t be placed in the blank by matching the deck of the board to the deck glue up of the blank anyway. The board should be tilted in the blank slightly. The tail deck, should be as close to the blank deck, as possible. While the boards nose bottom, should be as close to the blanks bottom as possible. This is one of the reasons why the blanks I did for Clark didn’t have a ton of tail rocker in them. They were designed for the shaper to thin the tail as needed by cutting in the tail rocker rather then cutting down the deck on an overly rockered blank bottom.
Attached is a photo of me measuring rocker with my 6’ stick.
Mr. Barnfield,
Yes, your method of the shorter stick is great, that’s how I had done it for years. I actually just lined the end of the stick up with either nose or tail tip depending on which one I was measuring. I found this was the most important “short stick” factor. I believe you came to the same conclusion with putting marks in increments on the stick. In the end I found if I used a stick that at minimum would go nose to tail that I wouldn’t have to move the stick for nose and tail. If you do read my post a little closer I mentioned that you must still press, just not quite as hard. I found both methods gave the same exact results.
As far as rocker templates I think you’ll find I said that IF you use them that you must pre determine overall nose and tail rocker at the tips with the centering method first so you’ll know where you’re going.
I believe all good shapers have the ability to carve out a nice rocker without even a measuring device, but it’s nice to know we have ways to go back to ground zero when we get a good one with measurements or templates or preferably both. Or just get a machine! Ouch!
I rember those days when Boscoe used to deliver blanks to all of us at our individual shaping
rooms. In those days we REALLY had to work on rocker as those were some thick ones with not a lot of diffrent plugs like now. ( Swiss Army Knife blanks ). A few blanks had to fit a wide variety of boards.
I do enjoy your posts and I always enjoy a good rocker thread as this is probably the most mystical element in surfboard design.
aloha, C
there are many teqniques and approaches to measuring rockers, most of the ways that have been touched upon in this thread is not very accurate and precise. it get’s you in the ball park but isn’t exacting.
one missing element in this whole thread is the most important rocker, which is the deck rocker and how it’s relation to the bottom rocker. it’s the most crtical and fundamental foundation to replacating the “magic board” measuring just the bottom rocker with out an exacting deck rocker and it’s relationship to each other will result in guess work, which defeats the purpose of taking and measuring rockers to begin with.
maintaining rocker in relation to porpotion is key, once you start to scale rocker by the same factor as the width and length it will not maintain the same values. so in this regard, rocker isn’t porportional to the same scaling factor.