So the discrepancy is -1/8” total or 1/16” nose and 1/16” tail. Sounds pretty close to me.
Put away the level
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^^^^ I always wondered if that was a reasonable way to look at that curve. Now I know.
Level is only relative to something else that’s either level or plumb. I don’t understand it’s use of a level for this.. The floor method is better but still affected by foam distribution which is unrelated to rocker but effects how the blank sits due to weight distribution. Things always get complicated when really annualized. I call the thickest point the apex, I don’t know if that’s right or not but it gives me a point of reference that’s consistent.
As long as your reference point is the same you’ll get consistent numbers from board to board.
I think most blank companies take their measurements from center of blank (unless told otherwise) That usually coincides with their thickest point as well.
When I shift the thickness I shift my point of rocker references as well
a long way to say I do what Gene stated above
i saw a rocker table once pretty cool -
totally flat - center was 0 and had 6’ tape measures going out on both sides - put your thickest point on 0 and take measurements at any point in either direction
Mounted at eye level -
measure with a flat bottom
"We ain't on our way to Wembley,we ain't gonna win the league. No matter how much they let us down - Westham's still our team"...
Just my 2c... This has been discussed on Sways since forever.. If you have been keeping records, great. If you want to become a good shaper you need a consistent system. I learned my from the HI shapers when they came to the mainland in summer to shape a long time ago. It is so simple and accurate that I’m still surprised that people are still placing blanks on the floor….
Step#1: Find the center of the blank by measuring up from the tail. Mark the center. All of the West Coast blank makers set rocker from center. Just look at the catalogs.
Step#2: Place your level centered on your mark, then slide the blank on the racks until it sits level. I have a dedicated level I use only for shaping.
Step#3: Place your rocker stick (which should have a center mark at 4’) centered on the blank. Take your measurements. If you are measuring a blank greater than 8’, you can slide it up or down and put pressure on the center point of the blank and be pretty accurate. I use a 10’ extruded aluminum channel since I do lots of long boards.
Remember that too much pressure shaping and/or glassing can alter the rocker at tip & tail a bit. A tolerance of +/- 1/16” is really pretty good. All blanks are cut & glued up by hand. In my opinion Nose/Tail tolerances are not as important as 6” up & 6” back. You can change nose/tail measurements by a simple pass of the planer and not affect board performance much if at all. Back in the 04-05 post Clark era, blanks were all over the place, so as a newer shaper, consider yourself lucky! Again, just my 2c……
Blank nor straight edge need to be level. Famous Swaylocks guy Lee Vanderhurst finally convinced me that there is ONLY ONE point at which the straight edge will be tangental to the midpoint. Various blank thicknesses and rocker will make placing the blank "level" the work of the devil himself. Another famous Swaylocks guy (Bill Barnfield) covered this in detail and advised that a blank can be standing in the corner of the room and this process can still be accomplished. I have gotten damn close with a 'too short' straight edge when measuring rocker for a 12'6" paddle/surf hybrid... by 'shimming' the straight edge with a block several feet away from the midpoint and sliding the straight edge to the end of the blank. As long as the end of the stick is still touching the midpoint, you're good to go. None of these methods will hold up to micrometer readings but who cares? Once you glass the thing it's gonna pull the rocker a bit anyway. And yes, we nearly started WWIII over this several years ago... http://web.archive.org/web/20100601095417/http://www2.swaylocks.com/node...
Good to know that someone does it the same way I've always done it.
Also: "In my opinion Nose/Tail tolerances are not as important as 6” up & 6” back." are words of wisdom, too.
John; I understand what you are saying, that's why I put that note in Step #3. When I started to do a lot of hp longboards back in the 90's I needed a system that was quick and accurate time and time again. I spend just minutes checking rocker on a hand shape with my system. That's what I'm trying to pass on to DublAK2... Had a visit from Bill back then and he approved what I was doing. Don't know what else to say, with most of the young guys getting boards cut they don't really care what the rocker is off the machine. Just scrub and done. I don't have many more years of shaping left, but what I do make I want it to be the best it can be. You couldn't do better than starting out with level solid racks and accurate measurements. Just my 2c......
Agreed. Best thing about this thread is that rocker is even being measured. I've heard it said (and agree) that the rocker points at 12" and 24" at either side of midpoint are worth double checking. There is always room for more than your basic end point measurements... figure out a system and use it.
...most of the blanks that I use are custom ordered; most arrive with wrong numbers...
If I order STD ones; normally are good (with the expected tolerances)