rocker, curve, knee position and the NOSE DIVE
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If you are of more carpenterial bent and want to get an accurate measure of board profile:
1.Make a rectangular frame long enough to fit the board in. Mine is 7' long x 12" internal height.
Make it straight and square (it took me close to an hour to find suitably straight 2x4 timber in Bunnings - I used a piece of 3m angle steel to check for straightness in both directions). Add bits so the frame will stand on one long edge.
2. Put board in it as though framing a 3D picture, Stringer parallel to long edge of box box.
Fix board in place (does not matter if it's flat or not). I have threaded rods through the wood that screw down and up to hold the board in place.
3. Measure up from the frame to the stringer at 100mm intervals to get bottom line. I go from the bottom of the wood and subtract the thickness of the wood because i find it more accurate that way. I also use a digital caliper, but a sliding square works just as well - just slower.
4. Measure down from top at 100-200mm (not much change in top, usually) intervals to get deckline. I measure from the top of the frame then subtract from the height of the frame to get the board thickness (i.e. both bottom and top measures now relate to height above the stringer low point. This is why it doesn't really matter whether the board is truly level or not)
What you end up with is a pretty exact measure of board shape at stringer line and a very large rectangle of wood that you have to store somewhere.
If I succeeded in confusing you - and I'm sure I did - I'll try to post a pic soon.
1.Make a rectangular frame long enough to fit the board in. Mine is 7' long x 12" internal height.
Make it straight and square (it took me close to an hour to find suitably straight 2x4 timber in Bunnings - I used a piece of 3m angle steel to check for straightness in both directions). Add bits so the frame will stand on one long edge.
2. Put board in it as though framing a 3D picture, Stringer parallel to long edge of box box.
Fix board in place (does not matter if it's flat or not). I have threaded rods through the wood that screw down and up to hold the board in place.
3. Measure up from the frame to the stringer at 100mm intervals to get bottom line. I go from the bottom of the wood and subtract the thickness of the wood because i find it more accurate that way. I also use a digital caliper, but a sliding square works just as well - just slower.
4. Measure down from top at 100-200mm (not much change in top, usually) intervals to get deckline. I measure from the top of the frame then subtract from the height of the frame to get the board thickness (i.e. both bottom and top measures now relate to height above the stringer low point. This is why it doesn't really matter whether the board is truly level or not)
What you end up with is a pretty exact measure of board shape at stringer line and a very large rectangle of wood that you have to store somewhere.
If I succeeded in confusing you - and I'm sure I did - I'll try to post a pic soon.