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How would I go about making my own radius dishes?
I stumbled across this method:link
which seems pretty simple.
But how would I go about figuring out how to draw a circle that has a radius of x'?
I was thinking that I could take a string which is pinned down and attach a pencil at the end but....a 25' string to do this?! sureley there must be an easy way!

ps
Hi! cool forum!!

I go out on my wooden deck, tack in a nail, hook on my tape. Go 25 feet, tack down my blank, draw an arc with a pencil, go bandsaw it out. Done with the arc at least.

There will be some guys along to tell you how to do that. Check the links resource page above. David Mitchell, where are you? John O.?

I checked the link, that's how you'd become the proud owner of a radius sanding dish. Or you can buy them here from several folks. Blues Creek or LuthierSupplies.com See links at top of page.Dickey38567.9900462963

You guys make this way too complicated!

Here's the simple way. If you want to make a 2' dish with a 25' radius, then the center of the dish must be 1/4" lower than the outside edges. (Actually, it's .24 inches lower, but 1/4" is close enough.) So you take a 2x4 and draw a straight line along one edge (it's a little more convenient if you make it about 1/2" in from the edge). For sake of reference, let's call the edge of the board closest to the line the "A" side and the edge of the board furthest from the line the "B" side. Drive two nails partially into the 2x4 that are exactly 2' apart, with the edge of each nail on the B side of the line. It is important that the nail just barely touch the line, so there is exactly 1/2" between the A edge and the edge of the nail for both nails. Now, exactly 1/2 way between those two nails, make a mark 3/4" from the "A" edge of the board. Drive another nail on the A side of the line that just barely touches the line at this mid-point between the other two nails. (Sorry this is so hard to explain; it would be nice if I could draw a picture.)

Now, you need something that is fairly stiff but not completely stiff that is at least 2 feet long. A go-bar works, and so does a piece of 1/4 steel rod. Whatever kind of rod you use, you need to weave it between the nails. It should go on the "A" side of the 2 outer nails, and the "B" side of the nail in the middle.

The rod should now form an arc 2 feet long with a 25' radius. Simply scribe a line along the rod to trace the arc.

If you want a 15' radius, you need to move the middle nail another .15" away from the A side of the board.

Hope this makes sense. It is hard to explain, but simple to do. If it doesn't make sense, let me know and I'll scan a drawing and post it.Kelby38568.0287615741

You could buy 2 of my Contour Radius Gauges to make a jig to do the same thing Sylvan was explaining.
Tracy

or alternatively buy two of tracy's radius templates and use them as a routing template to make your router guides.

you will find other uses for the radius templates as you go along. have a look at his luthiersupplies.com website.

or you could just skip all the hassle and mess and buy some :).. ok ok I
know that is not what you were asking..

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John Mayes
http://www.mayesluthier.com

Check out the library of plans. the Forum has my bowl profiling fixture available. It uses your laminate trimer or router and is very similar to the method you linked to. If you buy the plans from the forum I will provide you with Autocad printed drawing of the what ever radius you like. Besides buying plans from the Plan library is a good way to help support the forum.MichaelP38568.4391435185

Here are some calculations for figuring out the dimensions of a 2ft radius dish:

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53% of all statistics are made up on the spot
http://driftwoodguitars.blogspot.com/

well it seems that the really long string method will have to be it....hope noone sees me cause its going to look silly!

PM me your mail address and I will send you printed templats of what ever radius you need. I make my own dishes so I must warn you get ready to sweep the shop. This process put off three times more saw dust than you ever though possible.

Here`s my po` boy method. I cut 8 2" X 2"X 24" strips. Using the long string or tape measure method I very carefully lay out a convex radius on one(21' or 15'). Then saw it out.I use that for a pattern for the others. When all are radiused I lay two out 24" apart and attach the other 6 evenly spaced along their length forming a 24" ladder shape. (Forgot to mention that I saw a 1" X 2" rabbet on the ends of those 6 ). Now I rip 4 thin plywood strips 6" X 24" and glue them to the now convex shape formed by the 2" X 2". You may need to spile(boat term)the edges a bit if you require an air tight joint on the plywood. Another nice use for this dish is to sand your sides and linings by attaching sandpaper to the dish . Easy, cheap and it works great!

Dale, that sounds interesting, got a picture?

Here's the setup I used to make my dishes. I'd recommend buying them, they're a pain to make and it's a huge mess. The concept of how to make them is not hard, it doesn't particularly involve a lot of skill or special tools. The only reason I made my own was because I'm doing a cylindrical top ala Harry Fleishman and noone sells a cylindrical form. They did turn out nice, but I'm really glad I don't need to make any more.

On the plus side, if you have something that you need coated with nasty mdf dust, you can just set it down within a ten foot radius of your jig while you're routing the dish.

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Jonathan Kendall, Siloam Springs AR

This is very much like my jig that is in the Library of plans except that mine jig rotates arond a pre cut 24" dia by means of adjustable guide bearings

I predict you will live a long and satisfying life. The rest of us look like this on a daily basis. (refer to John Greven post about making 43 guitars per year) Heck, here it is again.

Ha ha... We should make a calendar.

One of the specialties of the company I work for is safety engineering. I don't work in that part of the business anymore, but I've investigated enough accidents to scare me straight.

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Jonathan Kendall, Siloam Springs AR

Hi Dickey; No pics of my dish but I`ll make one. However I don`t have a digital camera. It will take a while to get pics developed and scanned in to the ol` puter. This thing is crude so don`t expect a thing of beauty. It started out as an experiment that worked so why change it?

What you were describing sounded interesting at least. I have four dishes made by David Mitchell, two for glue-up and two for sanding the two radiuses used for tops and backs.

Dave offered such a good deal we couldn't pass it up. I haven't seen him on the forum in a while. I'm wondering if the other Mitchell on the forum is kin to him?