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Advice Please: Best Way to Cut Archs & Curves?

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NinjaEpisode:

So I'm pouring over the Pac Cab Plans on Jakobud's site and I have a question.

The Cab shows an R55" on the front inward curve and on the top arch.  What exactly does that mean? I'm guessing the "R" stands for Radius, and the arch/curve represents the outside edge of a 55" radius circle?

If so, ok, so I can create the arch using a make shift protractor of string and a pencil secured to a center point.  Where do I place the center point?

Best way to cut it?  Just use a jigsaw?

p.s. Tried searching didn't find anything.

bdsjake:

that's would I did for my pac cab.  the center point may be off the the cab or at least down near the bottom.  its trial and error to find it, but you have two known points in your curve, where you start and end at the front and back of the side piece (the upper left and upper right corners).  so move your center point around until it fits -- you will want a helper for this.

jig saw is about the only thing to use.  after I cut the side pieces I clamped them together and used a power sander to smooth out the curve.

whammoed:

May be more trouble than its worth but you could make a circle cutting jig for a router:
http://www.woodworkingtips.com/etips/etip102000sn.html
No need for sanding afterwards.

Darkstalker:

"The Cab shows an R55" on the front inward curve and on the top arch.  What exactly does that mean? I'm guessing the "R" stands for Radius, and the arch/curve represents the outside edge of a 55" radius circle?"

Yup, you got it.

"If so, ok, so I can create the arch using a make shift protractor of string and a pencil secured to a center point.  Where do I place the center point?"

Actually, you'd be making a drawing compass.  Protractors are the things you use to measure and mark angles ;)

Here's what you do once you have a compass set to 55 inches:

Set the anchor at the top of the side panel where the edge of the R55" arc is, and mark an arch at the bottom of the cabinet.  Do the same thing with the other "corner" of the arc.  Place the anchor where the two marks you made cross, and draw the arc between the two original anchor points.  Not quite sure how you would make the R40" or the other R55" since your center would be floating in space.  Best bet would be to make a template or something with the arc top arch and copy it to the front side.

"Best way to cut it?  Just use a jigsaw?"

A jig or bandsaw would be the best way to go.  If you don't trust your saw skills, get it close and sand it the rest of the way...You need a jig to use a router like this, so you'd have to make a jig with a band or jigsaw anyways.  (Fish...cut bait...fish...cut bait)  Once you finished a side, you could probably use a router to cut the other side using the first side as your jig, so to speak.  You'd have to have a pretty long bit though, depending on how thick the side panels are.

Nannuu:


--- Quote from: Darkstalker on August 04, 2004, 05:28:57 pm ---Set the anchor at the top of the side panel where the edge of the R55" arc is, and mark an arch at the bottom of the cabinet.  Do the same thing with the other "corner" of the arc.  Place the anchor where the two marks you made cross, and draw the arc between the two original anchor points.  Not quite sure how you would make the R40" or the other R55" since your center would be floating in space.  Best bet would be to make a template or something with the arc top arch and copy it to the front side.

--- End quote ---
To make the others just place the panel on the floor of the garage and mark the centerpoints on the floor or piece of wood set out there.  Have someone hold the string or stick a nail in the piece of wood.

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