The botttom rocker in a shape is just a curve. As BB, GL, and DS have said (in so many words, and diagrams, thx to BB), the location of the ''high point'' of that curve depends on its pitch. It's that simple and doesn't need to be complicated further.
Absent any regard for pitch, there is still only one set of points that will define that unique line. Changing the location of the endpoints with regard to any given reference line doesn't change the curve.
Well stated … and Bill suggested we all measure this from the center … like 20 something years ago. Today this is standard.
So you would need to know all points at which you might place your CG while paddling or standing before you can start to make use of any particular break in a rocker and also consider how the foil might change the "pitch" of a board.?
Yes. Rider/paddler determines the pitch. Foil is another matter, its going to affect the balance and bouyancy distribution, etc.
''Breaks'' in rocker don't generally occur anywhere near the ''apex''. Open boardcad and check the rates of curvature along a bottom rocker; you'll see that the center of the curve is normally a very high-radius area. Any break will show as a low-radius area.
To get my terminology strait. Foil in this case is to refer to cross section?
Thanks. I enjoy the little pointers about boardcad. Being aware of those radii numbers will be useful I'm sure.
Foil in this case would be the cross section of center thickness (or thickest portion if not on center) from nose to tail. IOW the ''side-view'' of the board.
Same here. I also reference the middle rocker numbers from the US Blanks catalog- probably erroneous but that’s what I have…
thanx wouter, much apreciated !
really thanx everyone ! No more smoke out of my head (until my next thought) :)
Nicely said Bruce (deadshaper)
I know you know this Bruce. I am just adding a bit more because others asked questions.
Rocker is so important but alone it is meaningless as you have communicated. A particular rockers trim (or pitch as Greg would say) depends on the bottom contours, template, thickness foil and fins also. If for example, the tail is thick and the tail template is wide also, the tail will lift or trim higher and change the ideal trim angle of the rocker such that adjustments have to be made in the rocker.
llilibel03, that is why it is difficult to answer your question with concrete numbers. There are simply too many variables that are unknown unless you provide a lot more data. And even then we would be guessing to a great degree. That’s why it is an still an “art” in the end. No matter how good the science gets, the art and artist still rules in the end.
"Well, I would deliver to you a contemporary shortboard, let's say 2-1/4" think with 1-1/2" tail thickness 1ft. up and a nose @ 12" of 1-1/4".............. then I would also give you your bottom rocker/apex with a thinkness flow aka foil that looked like a surf ski.
They would begin to ride the same even though they had identically apex/bottom rocker. Foil is all encompassing."
Hi Bruce - You lost me. Did you mean to say that the shortboard with thickness flow (foil) that looked like a surf ski would ride the same as the original? I'm thinking it would not.
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Right on............. from someone who has religiously used a rocker stick for decades. The 10" back shaping 101 thing is bullshit. Or at least misunderstood by the interpreters? Accelerated and flattened curves are determined by measurements taken off my rocker stick relative to center and to the nose and tail measurements relative to each end. On shorter boards I know what numbers I need at 12", 18" 24" for paddling ease and early entry into waves. I also know how the tail rocker curve contributes to the previous consideration, and those numbers change depending on whether it is a HPSB or a noserider or something else.
To quote Bill Barnifeld....... but not exactly...... I, too look at surfboards as lines that have relationships to one another to deliver a desired effect.
To think that knowing where the apex of the rocker is could be more relative to what I would call Pitch. It starts to become more complicated from there.
Why? Because the high point or crown of a curve and ow it performs is working in conjunction with many (other) compounding curves on the given design.
Here is a simple example bringing foil into the fray. Let's say you give me a bottom rocker curve and tell me if the apex is at a given point, any board with that EXACT bottom apex/curve will ride the same.
Well, I would deliver to you a contemporary shortboard, let's say 2-1/4" think with 1-1/2" tail thickness 1ft. up and a nose @ 12" of 1-1/4".............. then I would also give you your bottom rocker/apex with a thinkness flow aka foil that looked like a surf ski.
They would begin to ride the same even though they had identically apex/bottom rocker. Foil is all encompassing.
My point is even far more subtle changes in all the COMPOUNDING CURVES deliver a different experience to an overall completed design..
If you prescribe to what Barnfield and I, and many experienced shapers do....... which is to realize that the rocker curve is as personalized as any give planshape aka outline on a surfboard, then you are on your way to a heightened awareness of what surfboard design is really about.
Have fun.
P.S. I didn't read the whole thread before posting, then came back and saw that Bill had chimed in. I should have known he would make time for a subject like this....... a lot of the stuff on Sway's is rhetorical and not worth the time answering (sorry). I'm sure a LOT of what BB states is my same mind set and I will come back and read it later after shaping............. sorry about that.
[/quote] Crap, what happened to the EDIT feature on this post? I meant to say they WOULDN'T BEGIN TO RESEMBLE THE SAME RIDE......... talking about the HPSB distribution foil and the surfski comparison. Typos can make you lok like an idiot if people ca't read between the lines.......... I guess it falls into the same category as "measure twice, cut once"! LOL..
It's obvious that Bill, Mike, and some of the others read thru my typo and KNEW WHAT I REALY MEANT. Thank lord.
Maybe this is how it all starts, the fingers mess up on the key board posting on Sway's, then the eyes aren't so good in the shaping bay, then the planer feels heavier than it used to....... oh man, I better get off this thing and get out there and shape while I can! ......better pu extra protein in the blender too!
Ayyyyyyyyyyyyyyyyyyyeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeahhhhhhhhhhhhhhhhhhh !? :0
Yes. Actually I state foil is 'all encompassing" meaning that it includes the entire thickness flow from nose to tail and where the distribution is at any given point along the length of a given design. I used the surfski example compared to a HPSB because the ski has the MOST extreme contrast in distribution from ANY surfboard I have ever seen. Those little skis are like 6" to 8" thick right on their tails! Even if the two examples had exactly the same bottom curve/apex, what I was stating to everyone by saying "pitch" was really addressing PLANING PROFILE.
I think the original question about APEX placement was in regards to planing profiles and to that degree the comment cited from shaping 101 is fairly correct albiet greatly simplified.
Of course you know this, Mike, as well as BB , Wouter, and some of the other experienced guys that post, but the hobby guys seem to miss to a huge degree the effect all the COMPOUNDING CURVES have on what a given design will do.
Even changing ONE feature will impact the total riding characteritic(s) of a board. Just think of taking two identical designs then comparing one that has round rails the last foot of the board opposed to hard boxy rails the last foot........... it changes the whole ride, and so on.
Loving all this rocker talk and appreciate the big boys chiming in and explaining it so well.
Now if we could see some pictures of your rocker sticks and your some tips on how to build one that would be awesome. (Now I know I could just continue using my aluminum square stock and a ruler, but I'd really like to build something a bit more professional to make it easier for shaping, to compare rockers and to make stringers and blanks.)
"Even changing ONE feature will impact the total riding characteritic(s) of a board. Just think of taking two identical designs then comparing one that has round rails the last foot of the board opposed to hard boxy rails the last foot........... it changes the whole ride, and so on."
Agreed... I've been quoted as saying that for every single design change that results in a different ride characteristic, I can change another different design feature that will cause the ride to change back to ground zero. I'm not sure if that's exactly true but I could come pretty close.
Aloha Paulboardman
If you have an aluminum stick, you have THE MOST PROFFESSIONAL product that exists.
Don’t equate complicated gizmos as being more professional. Read carefully my post above about Gizmo Guys.
I have one of those complicated rocker thingamajigs made by my Gizmo Friend in Japan. I have had it for about 35 years and I have used it maybe a couple of times!
Learn to use your aluminum stick and a ruler. Measure every 3" or 6" or 12" and keep good records of the numbers you find. Measure to a 1/16" if you can. Measure boards you make. Measure boards other people make and measure everything else you can find that goes in the water. Make charts on columnar pads and refer to them often.
The way you compare rockers is… you compare the numbers. Put them on columnar form so you can write in numbers and see them next to each other. Note the measured differences at the same stations. You will begin to “see” the curve in your mind, based on the numbers, that represent it. This IS the PROFESSIONAL way to do it. Since the number, is what you have to hit when shaping, it doesn’t really matter that much… what you think it looks like. Just hit the numbers and you will be as PROFESSIONAL as is possible.
If you want to make rocker templates or stringers. Draw a base line then measure the rocker points along it at each station and depth. Then connect the dots and you will have your template.
Bill is absolutely right, IMO; but that doesn't mean that the rocker jigs'gizmos are bad. Just a different way of accomplishing the same task. BB,DS, and I think our way is simpler and I'm always about simplifyimg. Sometimes here on sways there's a tendency to over-complicate things and seemingly look for the most time-consuming method.
Don't ever let the #s rule your design, though. That's one of the reasons I prefer working with rocker templates when possible. And even now when I design new rockers in CAD, I'll frequently draw it out on masonite so I can really ''see'' it, and make adjustments back to CAD if needed. If the value of a good eye-balling by a trained eye ever goes out of style, God help us......
I’m very late to this discussion but have to say if there was any rating system for the different threads here a swaylocks like Chrome, Copper, Silver or Gold this one would be Gold.
It’s been a number of years now that I turned in my rocker stick for a small laser. Works the same as a stick but much more portable. As well, you can use it anywhere and still get the same measurements as long as you don’t distort your blank.
You can’t really see the laser line in the picture but I’m measuring tail rocker.
Since foil was mentioned, I’ve got a blog post on foil if you’d like to read a little thing on that.
http://drsurfboards.blogspot.com/2010/02/essence-of-foil.html
Aloha Dennis
Just a couple of quick questions.
How do you insure that your laser line is tangent to the rocker curve at center? Do you have pads at each end on the bottom of the laser unit and then locate the laser’s center over the boards center?
If the laser beam projects out of only one end of the unit, do you just spin it around to do the other end of the board. If so, does it always stay accurate to the tangent when doing so?
Assuming the laser unit sits on the blank, then the light source is above the blank and the beam/line it projects is also above the blank. So, do you just deduct that amount above the blank, from all your measurements along the rocker?
Lastly, is the lasers light beam small enough to put a fine enough line on the ruler so you can easily measure down to 1/16" on the ruler?
Nice blog on Foils
Bill I agree with you regarding the word APEX.
While I don't disagree with your baseline approach, regarding a reference or baseline, IMO the best must functional reference line is a tangent line that is parallel to the ideal trimline relative to the design of the board. The tangent point of this line is located at the theoretical ideal centerpoint between entry and exit rocker curves, or the midpoint of the transition rocker. I would post a drawing but I gotta go work. The biggest obstacle to using this theory is its impracticality in comparing and measuring boards. But if the midpoint of the transition rocker can be located accurately, I think this point, along with the rocker measurements would give the most usefull information. I think the location of the transition midpoint is one of the most overlooked design elements of a surfboard. Although its not easy to measure because as you say you need a reference, so full circle.
In practice I use the traditional method along with the parallel to trimline method. Much of the time I just like to use my eyeballs instead of a stick.
Which reminds me, I find that standing 15-20ft away from the profile lets me see things really well. But most shaping rooms are not designed well or large enough to do this. I guess thats why its easier to use traditional measuring tools, not to mention their accuracy. Cheers!
PS - this is a board curve I made from scratch using flat pieces of foam, bent and shaped into proper form
Crafty
I am confused. The thing your describing seems as ambiguous to me as the Apex. Some think the Apex Location has a particular importance in the function of the board. Some think the tail rockers radius. Some, as you have noted, think that the entry rocker contains the magic.
Everyone is always looking for a repeatable design formula or tool that they can get their hands on and apply to their board making. If it has a cool name like Apex Location, Rocker Radius or any other such branding, all the better!
I am not sure such a thing exists. Please convince me otherwise. :-) Cause I don’t want to be left behind!