How to make a fair curve?

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Saw a picture of a quilt rack with curved sides that are not arcs of a circle. HOw can I create a fair curve about 36" long that isn't merely an arc of a circle. I'll post the picture on ABPW in a minute - subject line: Quilt rack.
dave
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"Bay Area Dave" wrote in message

A large plastic French Curve works well,. Also, at a drafting supply store you can buy a various lengths of plastic strip that is flexible, but can be bent in many different positions and will hold its shape. I use one for non-radius, flowing curves like you mention.
That said, most folks can do a fair job of free handing a non-radiused curve on a piece of mdf, then using a bandsaw, a pattern maker's rasp, and finally, a flexible strip with sandpaper attached to fine tune and smooth out the curve ... the mdf pattern then becomes a template for a pattern bit and your router so that two or more pieces will have the same curve.
Most of the time it is well worth the effort to make a template with either of these methods.
For radiused curves, I use a thin strip of wood with a string attached at either end like an archer's bow, with a piece of wood on the string fastened in a manner to hold the tension at the desired curve.
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thanks! [thinking out loud]I wonder if Office Depot carries any drafting supplies like the flexible strip you mentioned? (I'm about 5 blocks from OD) I remember using a French Curve in grammar school, but of course it wasn't near the size that I'd need. I'll definitely take your advice on making a template. I don't have a pattern maker's rasp, so I'll look that up to see if I've got anything similar. I DO have a Surform rasp which is about an inch and a half wide and maybe (going by memory) about 10 inches long.
For something this long I take it that it wouldn't be a good idea to use my new handy dandy OSS to smooth out such a gentle curve?
dave
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Bay Area Dave wrote:

A thin strip of wood would work well. If you go the Office Depot route, an inexpensive flexible ruler would probably work as well.
The spindle sander should make the job of smoothing the part easier. Just remember to take your time (or you'll be re-making the part.) Plan to do the final shaping by hand with a sanding block.
Woodcraft, Lee Valley, et al carry bendable curves that make this kind of layout fairly easy. I have one but am usually more comfortable with the wooden strip approach.
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Morris Dovey
West Des Moines, Iowa USA
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I guess my "thin" strips of wood aren't thin enough! I just ran out to the shop and tried to bend a piece of oak that is about 1/4" thick. No go.
I ran it through the planer (stuck to a thicker piece with carpet tape) and promptly "blew" it up on the second pass. Took another strip and got myself a 1/16+" piece to play with.
I ran screws into a sacrificial assembly table top and played around with the strip. Seems like that will work. I suppose I can adopt the same method with the MDF template? Just run some screws in at strategic locations and bend the wood around them and trace? Am I on the right track?
dave
Morris Dovey wrote:

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Why use the planer? That's what a table saw is for!
RIP some 1/8th" strips of oak about 36 - 48" long ... guaranteed to bend and be flexible enough for a curve, to a point.
I usually have a bucket full of such strips of various lengths left over after a batch ripping fest. They make great flexible sanding strips for the final part of the finishing of the curve.
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duh, sorry, I DID have an 1/8" piece of oak, but it didn't bend too well! I see I wrote "1/4". I meant 1/8. my bad.
dave
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probably it didn't bend well because it was too wide. I cut it down to a couple of inches before bringing it down to 1/16. that seems to work fine. but you are right; if I had realized a narrower piece would suffice, I could have shaved off a 1/16 piece from a board on the TS.
dave
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Bay Area Dave wrote:

Sounds like it. I don't think I'd run (any more) thin strips through the planer, though. I tend to favor the bandsaw for ripping thin strips like this because I feel a little more in control of what's going on. Usually I can rip a nice uniform strip. If you want one part of the strip to be more "bendy" than the rest, just plane or sand that part a tad thinner than the rest.
Your screw approach sounds workable. If you're going to do much of this kind of work, you might want to glue a block to each end of a strip so you can "freeze" the curve just by clamping the ends down.
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Morris Dovey
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yeah, it was a bit of heart lurcher when I heard a chunk tear out. first time that's ever happened to me, so I was a bit nervous running the next piece through, but it came out clean and more importantly, uneventfully! :)
dave
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"Morris Dovey" wrote in message

Jeeez, you guys sound like you'd walk around the block to go next door. Any dyed-in-the-wool wooddorker's table saw, with a decent blade, will easily rip a 1/16th" strip off +/- 4" wide, 3/4" - 1" thick stock safely, accurately, quickly, and with no need for further fuss or muss ... can't ask for simpler/better than that. :)

That works very well for compound curves.

Excellent advice ...unless you have the three hands necessary to hold the curve AND wield the pencil.
However, providing an extra pair of hands is one of the few things that SWMBO's are really good for in the shop ... makes them feel like part of the team and facilitates that warm, fuzzy, harmonious feeling which contributes directly to loosening of the purse strings.
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didn't you notice my post an hour an a half ago where I agreed with you about using the TS? Or am I not part of "you guys"?
dave
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"Bay Area Dave" wrote in message

At ease, Dave ... you were excluded in this one instance, but don't let it go to your head! :)
However, I did think it was notable that a table saw would be an afterthought for the task to more than one woodworker ...
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but look at if from my perspective: I had an 1/8" piece that almost fit the bill. I didn't think of anything more immediate than to plane it down to to make it more pliable. Had I been staring at a piece of lumber, then I would have gone over to the TS... see? :)
dave
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wrote:

Bent strips are OK for symmetrical curves (I use fibreglass skite spar), but they don't work so well for an asymmetric curve.
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They might if you taper the strip.
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Larry Wasserman Baltimore, Maryland
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On Sun, 15 Feb 2004 20:36:01 GMT, snipped-for-privacy@fellspt.charm.net (Lawrence Wasserman) wrote:

Hmmm... That's an interesting idea. Anyone tried it ? How well did it work out ?
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I used this approach to apply a curve to some table base aprons. I bent a thin (1/8") strip of wood and clamped the ends. I cut it out with a jigsaw and used the first piece as a pattern for the second. I'm guessing that doing it the way I did, I ended up with a parabolic curve.
todd
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todd wrote:

If the strip is of uniform width and thickness, I think the curve is called a catenary. It's the same curve a chain makes when you suspend it from its ends. It's like a parabola, except that the apex is flatter.
I don't think you'd really like aprons with a true parabolic curve.
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"Bay Area Dave" wrote in message

Very difficult to find tool these days ... and be prepared for sticker shock:
http://www.leevalley.com/wood/page.asp?page0288&category=1,42524&ccurrency=2&SID Despite the price, it is a much used tool in my shop for curved/rounded parts.

I find that I need to use a rasp for roughing out, then the OSS, then sandpaper on a thin strip of wood that can flex enough to really smooth the curve without the 'bumps' you tend to get with the OSS.
Just my experience ...
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