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PostPosted: Thu Nov 17, 2011 1:52 pm 
This has worked for some folks, makes sense to me but I'd like some input before I try it.

http://www.ukuleleunderground.com/forum ... adius-Dish


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PostPosted: Thu Nov 17, 2011 2:24 pm 
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Location: Seattle
I always thought the thing to do is to hang a rope from a tree at the correct radius and tie it to a router and just route away.

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PostPosted: Thu Nov 17, 2011 2:29 pm 
The rope idea is just too complicated for me, John. Plus it is snowing a bit outside, which is where my trees are! :-)


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PostPosted: Thu Nov 17, 2011 2:42 pm 
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deadedith wrote:
The rope idea is just too complicated for me, John. Plus it is snowing a bit outside, which is where my trees are! :-)


Maybe a stairwell?

I did carve out my classical guitar solera sort of in the way described in the above link.

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PostPosted: Thu Nov 17, 2011 5:27 pm 
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Location: Seattle, WA
I trust the math (which I've used, too) more than the rope!

Using the formula, you can calculate the offset from the arc's chord (the "perpendicular bisector" according to Wikipedia) for any radius or dish width. Take something that flexes predictably, like a steel rule or a rectangle of lexan, pin the ends and flex it to the offset. Trace the resulting curve and you ought to be very close to the theoretical arc. Saw, sand, or rout to the line.

To make a spherical dish, I carved the curve into a couple of 2 x 6's and mounted them above a plate which held the MDF. I'd rout sliding the router across the forms, turn the MDF a bit, rout, turn, etc. After a while, I had a nicely hollowed out form. To make a cylindrical form (I sand my rims in this rather than a dome), I just made up eight strips of good plywood (3/8"? Don't remember but that sounds about right.) with one straight edge and one curved. They were attached to a base plate and two layers of 1/16" solid hardwood plywood screwed and glued to them. I can sand a test piece in either one and it fits well in the other so at least I'm consistent.


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PostPosted: Thu Nov 17, 2011 9:13 pm 
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Sorry, I did not mean to imply that I used the rope. I used the math as described in http://www.ukuleleunderground.com/forum ... adius-Dish. I drilled the right depth holed on concentric circles and used a plane and sand paper.

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PostPosted: Fri Nov 18, 2011 12:16 am 
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Location: Visalia, CA
Ken, can you share with us who that company is? Can we get a two for $90 deal! :>)

Kevin


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PostPosted: Tue Nov 22, 2011 8:38 am 
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Not really a dish, but your index card trick for glueing braces is almost the same idea. The one on Ken's site, it's the way I still do it.....Thanks Ken....Dave


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PostPosted: Sun Jun 30, 2013 9:29 am 
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Excellent idea IMHO.
Tom

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PostPosted: Sun Jun 30, 2013 1:41 pm 
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It occurs to me that if one is concerned about go-bars distorting the form, the space between the base board and the radiused board could be filled with the sort of expanding foam that you can buy at hardware stores for insulation. That stuff makes for a very rigid form.


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