The arc -- without math

[Gramp's shop]

You may recall that I queried the group about an equation to find the radiu s of a circle in order to draw an arc for a bit of molding for the buffet I 'm building with my son. We elected to drive a couple of screws at the end points, clamping to those a thin strip arched to the center point. I held it at the center point and he drew the arc. A few minutes at the bandsaw and a few more minutes at the oscillating sander -- okay 20 minutes at the sander -- and voila.

We're in the home stretch. On to final sanding and finishing. Pix to come .

Larry

[G. Ross]

of a circle in order to draw an arc for a bit of molding for the buffet I'm building with my son. We elected to drive a couple of screws at the end points, clamping to those a thin strip arched to the center point. I held it at the center point and he drew the arc. A few minutes at the bandsaw and a few more minutes at the oscillating sander -- okay 20 minutes at the sander -- and voila.

You did it the intuitive way. Good for you.

When I built my Japanese bridge, I knew the width and height at the center. I made a compass out of a long strip of wood anchored by a nail into a piece of two by. By trial and error I figured out the radius (around 14-16 ft), drilled a hole in the strip to hold a pencil and drew the lines on the pieces of treated 2 x 12 and 2 x8 to make the sections.

Cutting an arc on a long piece of 2 x 12 with a bandsaw is a lot of fun when you have no helper.

[Sonny]

And the more you do, the easier it gets, especially with smaller arcs or cu rves. You develope a knack to freehand them. It pays to have round eyebal ls, though, to make perfect arcs/curves. Better still, when it comes to th ose tricky double "S" curves, it pays to have one eyeball rounded one way, and the other eyeball rounded the other way.

Sonny

[Bob Wilson]

of a circle in order to draw an arc for a bit of molding for the buffet I'm building with my son. We elected to drive a couple of screws at the end points, clamping to those a thin strip arched to the center point. I held it at the center point and he drew the arc. A few minutes at the bandsaw and a few more minutes at the oscillating sander -- okay 20 minutes at the sander -- and voila.

In fact that is the idea behind the mathematics of spline functions. It grows from the way that New England boat builders ages ago used thin strips of wood (called splines) to make a smooth curve through certain required points, where the hull's side boards had to meet bulkheads I will guess. Bob Wilson