Replies

1. 
   SimonJ | Mar 28, 2008 03:26am | #1

   Here's how to do it with paper, a straightedge, and a compass. You could certainly use string and stakes outdoors (or do a scale drawing and then scale it back up)

   Using the dividers, mark an arc centered on either end of the arc you wish to bisect that is on the far side of where the center is. The 2 new arcs should be long enough to intersect on both sides of the original arc. Note - use the same compass setting for both arcs.

   Using the straightedge, connect the 2 intersections.

   The point where the straight intersects the arc you wish to bisect is its center.

   See attached (not quite to scale, and I drew full circles, but should convey the point)

   Of course, you could adjust the compass until the intersection occurs on the arc (at the center) but that requires a little trial and error.

   Hope this helps
   -Bob

   
1. 
   dlb | Mar 28, 2008 03:21pm | #3

   Thanks for the reply. I had an idea that this would be one approach. I can use a string w/ a pencil tied to it to emulate a compass.

   Thanks,

   dlb

   .

    The undisciplined life is not worth examining.

2. 
   QCInspector | Mar 28, 2008 12:43pm | #2

   Pick 2 endpoints of the arc you want to get the midpoint of.
   Measure the distance between them with your tape measure and divide by 2.
   Perpendicular from that line's midpoint to the arc is the midpoint of the curve.

   Does that work for you?

1. 
   dlb | Mar 28, 2008 03:24pm | #4

   Thanks for the reply. I had thought about your approach but my problem would be the perpendicular part. The arc is 6+ feet long. But, ... using a board laid from end to end and then bisect it's length would allow me to strike a perpendicular line across the arc. Good idea!

   Thanks,

   dlb

   .

    The undisciplined life is not worth examining.