Cutting a large radius/curve???

[Brent Romero]

I am embarking on a project and need to cut some curves in some treated lumber of varying lengths of 5/4" x 6" like the curve in the photo. The width will need to be the same while the overall length will be different. Some as long as 8ft or so.

Any ideas?

Thanks

[Bill Ryall]

Router on a trammel, or good layout and cut on a band saw or with a jigsaw and clean up with a spindle sander.

[Brent Romero]

Thanks. I will have to do some brushing up to recall how to calculate the different radii. :)

[Mel Fulks]

If you mean the chords will be of different lengths and yet same heights, I advise against it. It's currently popular even on the facades of large new big city buildings. But what a hodge podge look! Much better to have same size or one large one with flanking smaller lower ones.

[Brent Romero]

Using these as trim for a wooden fence. The sections are a few different lengths and I want the board width (at the ends) to align from one section to the next.

[Earl McLain]

Thanks. I will have to do some brushing up to recall how to calculate the different radii. :)

No need to calculate the radii--just a flexible stick and piece of string to make a fairing stick. Was my first home-made tool, and still the best i've done.
earl

[Peter Quinn]

For the radii I prefer sketchup, if you can use it the calculations are unnecessary, just draw the curves and it will tell you the radii with the dimensioning tool. Otherwise there are some good calculators on line if you know the height and cord length, I have one saved on my phone that I use all the time at work. Or you can just do the bent stick thing with a few finish nails, can get difficult over 8 feet. For a fence I'd likely just band saw or jig saw to the line (probably wouldn't push pressure treat through my bandsaw, better to use somebody else's!) and finish up with a small belt sander or spindle sander. I have a compass plane the works great for cleaning up curves, but again...pressure treat...not my tools!

[Myk Rian]

I used a wire and pencil so I wouldn't get a stretch factor.
I used that method to build an atlas stand.

328104

[Denis Kenzior]

For making templates, I typically use these:
http://www.leevalley.com/US/wood/page.aspx?p=44631&cat=1,42936,50298

Then cut on a bandsaw and clean up with an oscillating spindle sander.

[Kevin Russell]

I typically will draw these up in sketchup. Since your width won't be changing, you can scale your edge point to match your new length and the arc will adjust accordingly.

If you don't want to use string or wire to draw the line, you can mark up a grid in sketchup and measure every few inches over and up to the arc. Transfer these measurements to your wood and draw a line from point to point.

You can do what my framers did when I built my house which is full of arches. Using the formula for obtaining a radius given height and width and they used string and my driveway to draw out the arches. One day, I noticed a 2x4 in the family room had about 3" cut off the bottom and was hanging. I couldn't figure out why until I noticed arcs drawn on the floor. It had been raining so they were marking the arches inside. One radius was too long to fit in the room so they cut the bottom out of the 2x4 and extended the string into the bedroom.

When I cut arches in pressure treated 2x12s for my grillzebo, I measured, marked and connected the dots. The arches were wide enough that I just used a circular saw. Ended up burning the thing up because the wood was so wet. I had to switch to a 30 year old black and decker circular saw with the same amp rating as the one that died and it cut through the wood like butter.

[Jerry Miner]

Here's the formula for calculating the radius (except I don't know how to write exponents in a SketchUp drawing):

(X2 + Y2 ) divided by 2X = Radius

328105

[Brent Romero]

Thanks a bunch

[Brent Romero]

Thanks for the help.
I typically will draw these up in sketchup. Since your width won't be changing, you can scale your edge point to match your new length and the arc will adjust accordingly.

If you don't want to use string or wire to draw the line, you can mark up a grid in sketchup and measure every few inches over and up to the arc. Transfer these measurements to your wood and draw a line from point to point.

You can do what my framers did when I built my house which is full of arches. Using the formula for obtaining a radius given height and width and they used string and my driveway to draw out the arches. One day, I noticed a 2x4 in the family room had about 3" cut off the bottom and was hanging. I couldn't figure out why until I noticed arcs drawn on the floor. It had been raining so they were marking the arches inside. One radius was too long to fit in the room so they cut the bottom out of the 2x4 and extended the string into the bedroom.

When I cut arches in pressure treated 2x12s for my grillzebo, I measured, marked and connected the dots. The arches were wide enough that I just used a circular saw. Ended up burning the thing up because the wood was so wet. I had to switch to a 30 year old black and decker circular saw with the same amp rating as the one that died and it cut through the wood like butter.

[Yonak Hawkins]

If you know the width and the height of the ​curve, use the two-stick method (http://lumberjocks.com/projects/49135).