How do you measure rocker?

[KneeBumps]

Well, frankfqr, I actually started this to learn, not enlighten... And I have! More than I asked for, which was simplicity in measurement (or communication) of rocker. It's obvious to me simplicity is too much to expect of what is essentially a complex set of mathematical equations (I agree with Beeline, we need mathematical precision ).
Keep the thread going, folks, I'm learning a lot.
BTW, red, the rocker jig is cool, my wife says she has seen one very similar for measuring the curves in a horse's back to fit saddles.

[frankfqr]

Kneebumps, in the grand scheme of things haven't you enlightened those that are curious by your inquiry? Digging this thread back up in itself is enlightening, they die so quickly. Are we at the point where we can draw a consensus from the "simplicity" descriptions, or as you state, do we need to quantify a mathematical approach? Red's device, or the application of 2x4 structure's, or horseback countour gauges (I like it!)will get us down to a starting point of the overall curve, but then by simple calipers or eyeing the progressing shape from the side you can attain the balance from nose to tail for distribution. Simplicity!! We all know it's more than that when you combine all aspects of the board, but as to rocker specific, I feel I'm comfortable with what I've attained. As for mathematical endeavors you can take it off the charts if you want to pinpoint V or concave or chine etc. contributions, but you will have to keep digging up this post and prodding....THANKS...frank...

[Beeline2.0]

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[frankfqr]

Quite right Bee on 2 strong points. I was looking at things from the standpoint of building my own. I see a method of defining the overall curve and taking it from there. But in the back of my mind I still percieve a problem with conveying to a shaper how you might want to change kick either way, or duplicate existing, and left without a defined mid point than how am I sure we're on the same page? Thats were I was at the start of this post, pulling off the tail pad will increase tail, reduce nose, midpoint changed. Perhaps given a few increments a gifted shaper can connect the dots and provide a clean curve transition. Still vaque cloudy issues left dangling.

[Beeline2.0]

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[red]

I came across this bit by Rusty. It helps take the math out of it.

"How to Inspect: Grab the nose end of your board and lift it to your eye. Look straight down the middle as you slowly drop the nose down. Notice the acceleration of the curve, and take note of where the apex (highpoint) of the rocker is. Lift the nose back up to your eye, shift it to the side a bit, and look down the bottom edge of the rail to as you drop the nose again, this time checking the rocker along the rail. Look for breaks in the rocker through the fin area, and notice how they differ from the center rocker. Now grab the tail end of your board and repeat the process to get another view of the business end."

This is a good way to approximate rocker low point, simply put your finger at the point where the curve changes as you sight down the board. Do it from both ends and you get a pretty accurate low spot.

By the way - the mathematics exists - Bezier curves are most often used
http://www.moshplant.com/direct-or/bezier/math.html
this one has a playground:
http://www.math.ubc.ca/~cass/gfx/bezier.html

But the curves from the nose to centre and tail to centre are different - one of the tricks is to get the different curves to blend at the centre meeting point - the difference between a 'go-er' and a 'dog'

[red]

By the way, on uniformity - I've shared my rocker with a standup shapers that he developed over 20 years - it's amazing how close they are for our 6' boards - if curves are right they'll work for all craft. If your shaper has a rocker that works and has ~5.5" nose and 1.5-2" tail lift, then don't muck with it (just be aware that you may need to shift the low point a bit to get it under your weight balance point

[Beeline2.0]

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[Headwax.]

ahh Beeline

I see you agree with Sun-tzu on MANEUVERING

Disciplined and calm, to await the appearance of disorder and hubbub amongst the enemy:--this is the art of retaining self-possession.

To be near the goal while the enemy is still far from it, to wait at ease while the enemy is toiling and struggling, to be well-fed while the enemy is famished:--this is the art of husbanding one's strength.

To refrain from intercepting an enemy whose banners are in perfect order, to refrain from attacking an army drawn up in calm and confident array:--this is the art of studying circumstances.

It is a military axiom not to advance uphill against the enemy, nor to oppose him when he comes downhill.

Do not pursue an enemy who simulates flight; do not attack soldiers whose temper is keen.

Do not swallow bait offered by the enemy. Do not interfere with an army that is returning home.

When you surround an army, leave an outlet free. Do not press a desperate foe too hard. (or they will lose interest)

Such is the art of warfare.

but alas Red does not heed the last and most important point and consequently stalemates himself

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cheers

It appears you know your Corinthians as well
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I praise you, dear brothers that you think of me in all pieces and hold the way, as I gave her to you. I let you however know that Christ is any man head; the man however is the woman head; God however is Christi head

[Beeline2.0]

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[Headwax.]

sorry Beeline

had a three hour session yesterday and I always write manure when I'm tired

cheers

[Headwax.]

yes... I know ... I must be tired alot....

[Beeline2.0]

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[Beeline2.0]

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[skansand]

bowling out eh?....... you could keep the reference point on the stringer when your removing the foam, then when your ready to plane the stringer down move the reference point to the foam beside it... ....but i DONT use an elecric planer so i dont know what they do...