radius Question

[JeepThing]

OK this might be a dumb question but here goes.... How do you measure a 20` radius? is there a simple method or do I just use a framing square. How to? What is the formula? (me not so good in school )

[GuitarPhotog]

Do you mean 20 inches, or 20 ft?

20 inches can be done with a yardstick, a nail and a pencil. 20 feet usually requires a tape measure, a string, and a pencil.

Is that what you're asking?

<Chas>

[Miriam C.]

Measure in 20" and 20" down or up, depending on where the curve is. Make a mark and use any 20" stick to draw the curve.

Oh and yes a framing square to find it will work too.

[planovet]

A nail, a string (or stick) and a pencil

[chorizon]

I measure radii at work with a Coordinate Measuring Machine.
If I wanted to draw a certain size radius I'd use one of the aforementioned techniques.

[planovet]

I measure radii at work with a Coordinate Measuring Machine.

Show off

[JeepThing]

Thanks, what i'm trying to figure out is degree of radius, like a 20 degree 30, 15 and so on. Is there a formula i missed in school or forgot? is 20" down and 20" in and draw a line with pencil and string from that point make a 20 degree radius? what would it be if i went 20" down and say 15" in what would that make it? Questions that make me go Hmmmm?
PS i only have a carpenter's square, pencil and small lenght of string, will try an borrow a calculator. So the CNC won't be of much help LOL

[Miriam C.]

Can you give us a picture of what you are trying to draw! If it is the Generic Benroy, Mike did a better description that is now a sticky. If you are looking for an ellipse then try this:
http://www.angib.pwp.blueyonder.co.uk/t ... tear80.htm

[JeepThing]

It will be a basic benroy design , like the plan calls for; the short compass will have a 19" radius and the long a 48' radius, I'm just not sure how to get that?

[Miriam C.]

http://tnttt.com/viewtopic.php?t=43208

This makes it so much clearer!

[JeepThing]

Thanks, I think I got it, So a 19 degree radius would be measured 19" down & 19" in; the circle made from that point would have a 19 degree radius? Correct?

[Miriam C.]

That is correct and on the Benroy you need to start the 19" point in and 18 5/32" up then have it meet the 48" curve (actually started from the bottom corner in 41.5625" and up 48")

[doug hodder]

I'm not so high tech....I got a long piece of 1/8" ply 3/4" wide....I shape it the way I want till it looks good. Stick in a couple of nails to clamp the thin ply to. Drag a pencil and voila...a profile. No flat spots or tangents to contend with. Doug

[bobhenry]

OH SLOW !


You were using the wrong compass again !

[Dean in Eureka, CA]

JT,
This link will show you how to layout an ellipse, courtesy of Andrew...
One of best pieces of information regarding profile layout IMO.
http://www.angib.pwp.blueyonder.co.uk/teardrop/tear80.htm