I’m making my first board with a single concave bottom contour. Let’s say I want the board to be 2 1/2 inches thick. Do I need to to make the board thicker to compensate for the volume the concave will take away?
For instance, if I want an 1/8" inch concave, should I shape the board (prior to shaping in the concave) to be 2 1/2" plus 1/8"? That way when I put in the concave, the center of the board will be 2 1/2".
Or is concave typically not factored in when talking about a board’s thickness? So a concave board that’s said to be 2 1/2" is actually less thick than that at the midpoint.
Uhmmmm - I have to ask, to what end are you doing these calculations?
You have a choice, calculating the total volume of the board as to how it will float you sitting absolutely still (Neat, Malcolm, but why?) or the planing area which frankly has d#ck to do with the total volume, it’s all about the surface that sees water when the thing is working.
The latter is a completely different thang, as it were.
For floatation/volume I’d just average it out, concave/2 times the width subtracted from total volume of an un-concaved thing. Which, considering everything and the fact that you’re unlikely to be doing laser rangefinder-type measurements on all of it, is irrelevant. Decimal point stuff. Don’t sweat it.
Instead, play with the concave, see how it works for you.
Just my way, and I know most do it different, but here I go…
I shape in the stringer rocker first, then I lower the rails to final contour. Way more accurate than shaping a flat bottom, then adding concave.
Either way, in your mind you should “preshape” the board. Go ahead and draw your concept on the blank, Shade in your contours. It will help to visualize what you are after. Nothing worse than hacking into the blank without a destination.
Thanks doc. It was in fact volume considerations that got me thinking about this. I’m designing the board with Shaper3D, and I’m shooting for a specific volume. What got me confused is that when I set the width, I wasn’t adustable, so I couldn’t pull in the center of the bottom to make the contour. So, I had to drop the edges to make the contour. That made wonder about the whole thickness/contour issue.
I know this post is quite old, but I’m starting into shaping (going for my 4th board now) and I was thinking about this yesterday.
What I find more logic is to measure it as in the attached image.
So its not the same the board total thickness to the thickness measured in the mid point/stringer of the board.
I would first define the thickness I want and later add the concave. Maybe before that shaping the lower rails? It may be even more accurate hahah. I’m not sure.
Measure thickness before contouring bottom was the way to go when all shape were made by hand, with computer designing it change and move to final measurement. Simon Anderson explain it well some years ago to explain his new thickness chart.
The “foil” of any board consists of plan shape , and profile . How it is shaped may vary with each board using the same foil…for instance , you may shape double concave tail , panel vee or flat tail , all using the same foil templates . …if you wanna bump the volume for a heavier surfer , just increase the thickness of the profile before you start shaping …forget talking litres or beers etc - it’s just shaping machine nonsense…pick the board up and feel it …it won’t bite…(lol)
Hi kayu…i agree with you on your last point…h i have made boards for myself that i do not even know the exact finshed thickness …if it feels and looks nice usually will work. I do have couple rail band angular templates i use to get my rail height similar board to board…keep it fun…
