Math problem (geometry) - Non-Wakeboarding Discussion

(jaegermaster) · (jaegermaster) **Join Date: Sep 2002** 10-02-2010, 6:44 AM

I am trying to find the radius of this piece I need to cut out of a 24" glu lam beam. Can anyone help? Is there even enough info to get the radius? I hope my crappy drawing is decipherable.

Thanks for any help.

(jaegermaster) · (jaegermaster) **Join Date: Sep 2002** 10-02-2010, 7:11 AM

If the drawing doesn't make sense, I have a 24"X109" beam. I need to cut a 10 1/2" wide radius out of it.

Thanks for any kind of response.

(pwrvelocity) · (pwrvelocity) **Join Date: Jan 2007** 10-02-2010, 10:38 AM

D = 2r

D = Diameter
r = radius

2 (10.5") = 21"

(bdavis) · (bdavis) **Join Date: Sep 2002** 10-02-2010, 10:50 AM

I'm pretty sure that's wrong w. I don't have a formula. But I would lay the beam on the ground. Have another person hold the end of a string and move far enough away until you can achieve the arc you want. The length of th string is your radius

(pwrvelocity) · (pwrvelocity) **Join Date: Jan 2007** 10-02-2010, 11:02 AM

Pretty sure I'm wrong????? Look it up in your Geometry book, Einstein!

(sidekicknicholas) · 11:36 AM

From that picture 10.5" is only a piece of the radius..... just the portion of the radius of 109" of the circle.... the radius in fact would be much much larger.

On the drawing - are you cutting out a 10.5" wide piece (e.i. - 2 cuts -top and bottom)? or just one cut 10.5" from the base of the board?

@ W - 1st post he is looking for the radius, so you have a equation - that is no help. good job.

(hunter660) · (hunter660) **Join Date: Aug 2007** 10-02-2010, 12:56 PM

Outside = 157.1905"
Inside = 146.6905"

(diamonddad) · (diamonddad) **Join Date: Mar 2010** 10-02-2010, 1:08 PM

You could calcute it from the 3 point math...

http://local.wasp.uwa.edu.au/~pbourk...y/circlefrom3/

(jaegermaster) · (jaegermaster) **Join Date: Sep 2002** 10-02-2010, 1:31 PM

I need to make both the top and bottom cuts.

(jaegermaster) · (jaegermaster) **Join Date: Sep 2002** 10-02-2010, 1:53 PM

I found this equation which apparently will give me the radius, but I'm not sure how the math works.

http://mathforum.org/library/drmath/view/69144.html

(john211) · (john211) **Join Date: Aug 2008** 10-02-2010, 2:23 PM

inside r = [(109 / 2) **2 + 10.5 **2 ] / 2 * 10.5 = 146.69

outside r = 146.69 + 10.5 = 157.19

(jaegermaster) · (jaegermaster) **Join Date: Sep 2002** 10-02-2010, 3:32 PM

Thanks everybody. I'll let you know how it turns out.

(jaegermaster) · (jaegermaster) **Join Date: Sep 2002** 10-04-2010, 5:24 PM

Here is the final outcome. Thank you all for your help. I really appreciate it.

Before, during and complete.

(bigdad) · (bigdad) **Join Date: Apr 2002** 10-05-2010, 7:18 AM

Did someone call the cops on you?

(mattgettel) · (mattgettel) **Join Date: Jan 2009** 10-05-2010, 8:00 AM

They must have heard you had doughnuts.

(jaegermaster) · (jaegermaster) **Join Date: Sep 2002** 10-05-2010, 8:28 AM

No, I have a Sheriff's Deputy that lives across the street. I do think I piss him off sometimes when I am working in the garage and he is on night shift. Oh well.

bigdtx 10-05-2010, 10:25 AM

So what's it going to be?

bigdtx 10-05-2010, 1:27 PM

And what did you use to make the cut? That's a pretty mondo cut regardless of the tool.

(jaegermaster) · (jaegermaster) **Join Date: Sep 2002** 10-05-2010, 6:37 PM

It's going in between two entry columns on a custom home. I cut it for a local builder.

I made a template out of 1/2" ACX plywood and used a 2hp plunge router with a collar. I took about 1/8" of depth per pass. The sketchy part was I could only rout 2 1/2" deep and then I had to flip it and get the template lined up exactly to rout the other side.