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Ok, I am starting on my first build and I would like to make my own radius dish. I want to make a jig for my router to route the radius but my problem is coming up with the correct radius. The way I am doing it is to take three pieces of conduit, I screwed the first stick down to a piece of plywood so it would still swivel. Another piece I drilled a hole in it at five feet so a pencil goes through it. Now if I want a 15' radius I attach it to the first 10' section and if I want a 25' radius I put the third piece in between the two. My question is, is that the correct radius or have I got it figured wrong. It appears to be a little too rounded but I am not sure. Any ideas would be appreciated.

Thanks
Mike

Mike, you don't need to go to such extremes. Search the archives for a spreadsheet that will give you deflections over a two foot span. then you can plot these deflection on paper and cut a couple of guides for your router to route out the dishes. Email me if you like and I'll send you the spreadsheet.

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A higher purpose for wood.
Rich Smith
Issaquah, WA

trust me dude, this is the way you want to do it. it is perfectly accurate and easy to do. you can use it to draw an arc or do like i did and mount your router in the simple jig and it will carve out a perfect rail of the correct radius for you. here are two links that you will need. the first explains the long compass. the second is a spreadsheet that will help you get the numbers you will need. if you have questions feel free to ask. i might be able to take some pictures if it is necessary.

http://gicl.cs.drexel.edu/people/sevy/l ... mpass.html

http://www.ukuleles.com/spreadsheets/ArcCalcs.XLS

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sweat the small stuff.

ok, i lied. i threw away the long compass jigs that hold a router because they got wet. my bad.

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sweat the small stuff.

Search the threads for my post on the long compass (to include equations)

Mike

I must be thick cause I can't get my head round this long compass thing when I get round to in I'll make mine different

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Formerly JJH

I learn more from my mistakes than my successes

Hi Mike,
I tried to attach a PDF file with both a 15 and a 25 ft radius that were computer generated and are very accurate, but for some reason it won't attach. Ever since the new software was enabled I have trouble attaching files. You can PM me and I will email you the file. I can generate any radius you like, if need be. Just let me know.

And if someone could explain to me why the "Img" button doesn't do anything or tell me what I'm doing wrong I'd appreciate it.
Craig S.

Well, I'm a neophyte here but at some time I'll need to do this so you've given me a good excuse to 'test post'.

Don't use the img button. Scroll a little further down you screen and you'll see a block labelled "Upload attachment". Use this to pick a file from your machine, hit "Add the file" and it uploads, then it'll appear in the drop-down list of attachments just below your editting window. Then you can place it wherever - like here - in your message you want.

The [Img] code is used for images stored on another site, like PhotoBucket, for example, or a picture posted to your own website. You can paste the link to the image between the image codes. It's good for an image that is not important to the archives, but not particularly good for posts that you would like to be a part of the long time future search capabilities of the site.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Here is a table.
http://www.liutaiomottola.com/formulae/sag.htm
Check the tutorials here also.

Wow, Thank you to everyone that have helped me with this. I didn't understand the spreadsheets that I had seen in the past until I started reading all the articles that were referred to here. In the end I tried the long compass and compared it to the radius I had already made with my conduit and it was identical. Now I just have to look at how I am going to make the jig for my router to ride in while cutting the radius.

Mike

I wish I were at home so I could send you a pic of a simple jig I made. I'll try to explain it. I made 2 rails out of 3/4" mdf with the radius cut into them. On one side of each rail, I glued and stapled a piece of louan (sp I know) in order to stiffen them and act to capture the router baseplate. These 2 pieces were the long sides of a rectangle, slightly longer than the diameter of the the dish (24" radius of the soon to be dish, 26" length of the rails. On the end of the rails, I attatched a piece of wood that set my rails the proper distance apart in order to properly capture the router base. That's got the guide done now. Next, I took a piece of mdf, about 4" wide and as long as the long side of the guide and drilled a 3/16 hole in the center of it for a pivot point for the radius dish. MDF pieces were attached on each end of this piece, pointing up in order to hold (via screws) the radius rails assy. The rail assembly was attatched at such a height as to allow the dish to rotate on the pin without interference.

I bet that muddied the water. Sorry if it did. It was a simple jig that took less than 1 hour to make.

Here is the link to the discussion, with some pics:

viewtopic.php?f=10101&t=18587

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Brad Tucker

I am attaching a spreadsheet that I think was posted on the MIMF when Chris Paulick did his discussion on using the long compass method for creating a dish and posted his YouTube video. It looks like that discussion has been archived (or is in the process of being archived). I don’t know who did the spreadsheet, but for me it cleared up the math quite a bit. I am going to attempt to make a dish in the next couple of weeks.

Chris, I had a couple of questions for you from one of your posts on this. I know I asked this before, but didn’t save the thread.

• What bit did you user in your router? I remember you had trouble with your first bit.
• You had given some minimums for how large you would make your rails. Could you restate those here? I’m about to start laying mine out.
• I think you also had a minimum you would use for the box. I was going to try a 30” box.
• How deep was the height of your fixed rails on the box?

I am posting these questions here instead of on the MIMF because there was an active thread here.

Thanks,

John Killin

Well I can’t attach an excel spreadsheet and I can’t find the link for it. But if someone else has the link it is a great worksheet. I just wish I could remember who created it.

John

since youve got the rail making figured out, here are a couple pics of my dish routing jig.

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sweat the small stuff.

Here is what I came up with. I added dust collection which worked pretty well. As I rotated the dish and the cut area was lower than the side the router kicked some of the dust out but the fine airborne dust seemed to get pulled in by my shop vac. I thought my ceiling mounted dust collectors would be clogged up but they didn't have much to catch.
Mike

good job mike. how did they turn out? i was surprised at how accurate mine actually were. good on you to add the dust collection. that stuff can pile up fast if you dont stop and vaccuum it up pretty often.

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sweat the small stuff.

They turned out very accurate and smooth. I just lightly ran a sander over them when I was done with the router.

Mike

I finally shaped my first 15' dish today. About halfway through, the router was able to generate enough torque to spin the dish, really surprised me! But that is not useful, just amusing. Just finished applying shelac to that one. Cut the templates for the 25' dish and will shape that one tomorrow night.

Glad yours worked out,

Mike

The way I solved that one was clamp it to the bench each time after I rotated it. Took a little longer though.

Mike