Layout out a Radius

[Prashun Patel]

What am I missing? Cut your template longer than the finished piece. Cut a whole Semi circle if you wish. Cut your blanks over sized, Bend them in the form and then trim them to size after they come out.

[Patrick F Graham]

Just that I can't figure out how to layout the semi circle.

Cord 21-3/4"
Radius 23"

That's all I got.


I know how to cut long.

I know how to cut oversizeed.

Drawing the template is what I'm not getting. I'm sure it simple but when I try to match what's described, it get something very different then what the full size drawing shows.

Patrick

[Prashun Patel]

Forget the chord. The template will work regardless of whether it's just as long as the chord or longer.

Measure 22" on a string and tie it to a nail in your bench. Tie a pencil to the other side. Or make a trammel out of a piece of wood. Screw one end into the bench not too tight, and make a hole for the pencil 22" away.

Put your template blank under the pencil and scribe out an arc.

Use a ruler to measure the cord after the arc is scribed if you wish. But as long as you're longer it doesn't matter. The picture with the A and B marks you posted a couple times is definitely not a circle with a 23" radius. The pencil in the picture makes me think that radius is only about 6-7"

[Ralph Okonieski]

You have an actual (half) size drawing. Draw a chord on it, measure the rise and and chord length, use the mensuration formulae for circle to calculate the radius. It should be close enough that it provide a clue as to the radius you want.

[Patrick F Graham]

Ben, Kevin and Prashum,

It was where to start the mark for the radius. Following ya'll's similar solution, I made this and it comes pretty close to almost exactly what the full size drawing represents.
20210703_163008 (Large).jpg

Prashum, forget that 'scaled' drawing, dimensions were a guess, I used it as an example of A and B.

The line just inside the outer arch is the 22" radius (right side only). The outer is the 23" radius.

Pretty damn close.

Thanks all - so simple once you hear, see, read about it.

Time to fire up the steam bender!

Patrick

[Patrick F Graham]

For sure, that's one way but I was trying to have the most clean start rather then a copy of a copy of a copy.

To your second point, yes, 'close enough' is a problem I have - I'm working on it.....

Thanks Ralph.

Patrick

[Kevin Jenness]

Be sure to make the form and the blanks longer than the finished part dimension.

I have a hard time reconciling the photographed chair with the plans you are building from. The height of a 23" radius arc 21.75" long is 2.73", and the slats in the photo don't match that to my eye- must be the camera angle. I would do a mockup to be sure. I must say that doesn't look like a particularly comfortable chair, but what do I know. Have fun.

[Patrick F Graham]

You know it - I'm adding 2" to each end.

It's a crazy comfortable chair, trust me, I wouldn't make it otherwise.

And yes, I'm a mockup maven!

Gimmie some of the Doug-Fir, I can build anything!!!!

Thanks - Patrick