Help with some wood working math! FIND THE RADIUS!

[Homerboy]

I have a piece of wood: 37.25" X 2.5"

I want an arch cut into the wood where at the center, the board will be 1.5" and the arch will go to the exact corners of the bottom of the piece (so the ends remain 2.5" tapering to 1.5" in the middle.

What is the radius I need to scribe my arch?

 

[shortylickens]

Ummm, not understanding the question. I think you need a 1.25 inch radius.

 

[Homerboy]

Ummm, not understanding the question. I think you need a 1.25 inch radius.

No

 

[TuxDave]

173.945 inches

 

[DaTT]

173.945 inches

Show your work...

 

[Homerboy]

Please show your work.

 

[TuxDave]

Show your work...

Heh I would but pics.bbzzdd.com uploading is borked (at least for me).

There we go (tinypic). And awww I see I made a mistake in the picture. It should write 37.25. My answer is still the same though

 

[Homerboy]

Nice. Now I need a long piece of twine.

 

[jteef]

Nice. Now I need a long piece of twine.

at that length, i imagine twine would stretch too much to be very accurate or useful.

 

[Homerboy]

at that length, i imagine twine would stretch too much to be very accurate or useful.

True. Wire or something then. Had to be a better method

 

[shortylickens]

Fishing line, dont pull too hard.

 

[jteef]

fishing line is also stretchy /saggy;

if you have a printer, i would just print out a template to trace a line against. if you're smart about it, you could probably fit the whole thing on one page.

 

[Mr. Pedantic]

Just use string, and don't pull so hard. It's not elastic or anything, even that length won't deform appreciably if you don't pull the crap out of it.

 

[SKORPI0]

Last time I checked, 1.5>1. Drawing does not look right. :hmm: j/k.
It's not in scale, drawing is for illustration purposes.

 

[T_Yamamoto]

:awe:

Last time I checked, 1.5>1. Drawing does not look right. :hmm:

 

[Squisher]

This certainly won't be a perfect arc, but a piece of flexible wood made into an arc by a piece of string attached to the ends, like a bow of bow and arrow fame, makes a serviceable template for a large radius. You can even incorporate a turnbuckle to adjust the length of the string.

 

[Homerboy]

3 nails at the points. Flexible wood/ pvc to form the arc. Trace and cut.

 

[drnickriviera]

If you want a perfect arc, use your 3 nails at the points. Now get 2 thin strips of wood over 37" long. Lay them in a V resting on the nails. The point of the V should be at the middle nail. glue/nail/screw the two pieces of wood together. remove center nail. put a pencil at the tip of the V and slide it along the 2 side nails.

Quick and easy, no need for any math

 

[twinrider1]

Just use string, and don't pull so hard. It's not elastic or anything, even that length won't deform appreciably if you don't pull the crap out of it.

Yep. And if it really is a concern, just rip an 8' 2"x4" in half, nail them together to make a stick long enough to measure out the 14.5' length needed to make the arc.