How to cut shape

I generally start by marking some intermediate points that I know will be on the curve. Then I use a spline, a thin strip of wood, to start connecting the dots. The one I use is about 1/8" by 6'. Even if you had an 8' spline you will probably need to do it in 3 segments.

I have found that a thin strip of formica can work well for this. carefully place a few trim nails along the desired line, then with a helper or two, let the formica form the curve and draw the line.

I am currently in the process of cutting my bench work with curved lines for curved fascia installation.  I had the same issues and have been cutting a template in heavy cardboard and using that to mark my cut line on the finished wood.

 

Art

I probably have a visualization deficit; i.e., it's very difficult for me to envision the end result of what I intend to build when it involves more than straight lines.  Consequently, I try to find ways to create a 1:1 representation of what I'm making in a mock-up form.

 

For a 16' bowed curve, I'd lay two pieces of plywood end-to-end; buy sectional track in the approximate diameters of the compound curves I'll be using; and, lay the various diameters of sectional track on the plywood in varying combinations to achieve the desired cosmetic look consistent with operational requirements.  This would be done in segments and ultimately the segments would be joined to yield the "final" or close approximation, to the "final" cut.

 

The sectional curved track pieces may represent some additional cost, but for a major element of a layout it's worth it, IMHO.  Good luck with your project. 

I think I know what you mean.  You want to create a bow in front the arc being equal on both sides from the widest point.  Put your plywood down. Put a nail on the farthest point out, and one on each of the lowest point on both sides.  Take a small piece of wood trim. like a piece of base shoe is best, the length you need to make the bow and connect the dots so to speak.  Fix it in place, then mark the outline with a pencil or marker and cut it.  Perfect bow.

Someone wasn't paying attention in geometry class.  Check out this link.  http://www.thisiscarpentry.com...based-arches-part-1/

I thought he wanted to know a practical way to cut a bow in his layout, not read a useless attachment.  If it's over 16', like you said, get a 16' piece of finger jointed primed base shoe, it should be less than five bucks, arch it, and then fix it with the nails at both ends, then finish the pattern to your ends with a straight edge like a level or square.  Perfect bow or arch.  I've cut my share.  Bow, meaning like a bow window outways from a wall or archtop window top to bottom.  For the geometrically challenged.

WOW!  I was wondering how far into 2015 we had to go before the bottom feeders materialized.

I revised my post.  To make an arch or bow, it needs to be one piece, then extended, again, for the geometrically challenged.  I'm not the one trying to look smart, just helpful.  Cheers.

Not a string.  Honestly, a piece of base shoe is perfect.  You need something with spring in it to it to get the arch shape.  I don't know what good posting here implying we don't know geometry and offering no useful suggestions did, but a little man under a bridge is happy now I guess.

 

Dave, I saw a older post about a controller for the Lionel Steam Clean and Wheel Grind Shop. I need a controller for one. The part # is 610-2767-123. If I sent this in error my apology. Thank you, Nick

Sometimes, if you use a fold out ruler, you can bend it to a basic shape and use that as a starting guide.