...looks like it's 14' 7 11/16"...
Thanks Nick! Would you care to share how you got that? I’ll need the info to find my other two radiuses.
Thanks much guys! That’s what I wanted to learn! So when I come up with decimals, if feet is my whole number, I multiply the decimal by 12 to get it to inches. Then I can multiply the remaining decimal by 8, 16 or 32 depending how far I want to break it down (8ths and 16ths is typically good enough). This will be my first (2nd and 3rd) large radius to rout. I’m looking forward to it but want it to be perfect.
This would be an arc because it’s just the top part of a circle. If I had the diameter then the radius is half the diameter. I’m not sure the formula used to get the arc but the arc calculator does the work.
I don’t recall much high school math either. I tried to forget as much as I could and then later realized I need some it.
Yup, you got it! It's kind of annoying that the imperial system uses multiples of 10, 12 and then powers of 2. I guess when you have yards you gotta toss in multiples of 3. yuck. Metric IS easier but you still have to deal with feet/inches/yards in the good ole USA.Thanks much guys! That’s what I wanted to learn! So when I come up with decimals, if feet is my whole number, I multiply the decimal by 12 to get it to inches. Then I can multiply the remaining decimal by 8, 16 or 32 depending how far I want to break it down (8ths and 16ths is typically good enough). This will be my first (2nd and 3rd) large radius to rout. I’m looking forward to it but want it to be perfect.
First of all, I don’t post much but I have gleaned much from reading here. But I haven’t been able to find my answer to this question.
I have three different radiuses that I am trying to find without using the “guess” method. I don’t have a true diameter for any of these radiuses. I found a radius calculator that allows me to put in the width and a height and it’ll give me a decimal radius but I’m having a hard time converting it to a usable measured fraction.
Typically, I’d get my width (19’), find center and then measure up to my height (3’-6”), snap a right angled cross on the floor and then start measuring down until I got my arch to cross both points - guessing.
So with my example, my arch is 19’ across and it’s 3’-6” high. The radius calculator says my radius is 14.642857142857142. How can I convert this into something I can use? I don’t have measurements for the other two. I am routing top trim pieces for all these.
Thanks in advance.
I used my Dewalt plunge router to cut all my radiuses. My largest radius was 19’-11”. I shot a 2x6 to the floor and screwed 3 1x4x8s together to get the distance I needed. I secured my radius point to the 2x6 and the 1x4s to my modified router base. I made 4 passes on each cut to get all the way through. No issues!Just had a read of this post and looked for a simple possible solutions.
With what tool are you going to cut the arch?
Could you just use a flexible stick between 3 nails?
Very interesting! I’ll have to write that one down and use it. I love learning new things and this is definitely new. I’m using an online radius calculator that allows you put in the length and height and it gives you the radius. Your formula is more than likely the formula in that calculator.Hi Mark,
Several other forum members have described how to convert a decimal measurement into a linear one already. The formula that I've used during my carpentry career is: Left x Right = Top x Bottom. (L x R=T x B) Or to find the variable (the bottom half of the circle that your arc is a part of) L x R ÷ T = B
Then add B + T for the diameter. Then divide by 2 for the radius. Think of a 16" pizza for example. If L x R = T x B then 8" x 8" = 8" x 8". That equation remains a constant within a circle as long as the two intersecting lines remain perpendicular.
In your case L= 9'-6". R=9'-6". T= 3"-6" I'm also assuming that your are using a standard calculator rather than a linear. So then L=9.5. R=9.5. T=3.5
Calculation: 9.5 x 9.5=90.25
End result: 14'-7 11/16"