Check my math

[john in la]

I want to build a hoop cage and need to know how long to cut the pipe that will make the half circle.
Is it pie times diameter???

In other words if I want the cage 5 feet wide.
I would multiply 3.142 X half of 5 feet or 30 inches and get 94.26 inches.
So if I cut a piece of pvc 94.26 inches and bend it to where the ends are 5 feet apart I would have half a circle.

Am I correct in my thinking??

 

[Patsdeere]

Seems right to me.

 

[SVcummins]

One way to find out

 

[Steve in VA]

John,
Yes, your example is correct. Circumference is pi x d or [ pi x 2r]. So one half would be pi x r. It sounds like a hoop house. The only disconnect is the lead in question stating that the half circle is pi x d and I think you either mentioned "r" or were referring to a complete circle ( or I misread it).

 

[MarkB_MI]

Yes, but I don't think the PVC will form a circular arc when you bend it. It should be close enough, though.

 

[john in la]

Yes Steve. My bad. I said diameter and was thinking radius. Thanks for the help.

 

[john in la]

I did not think about that Mark as the side will be vertical for a short distance till it starts the bend. This will flatten the top out.

This doesn?t have to be a perfect half circle as it will only cover small plants or provide a cage for a few chickens. But it does give me a place to start in figuring pipe length as it relates to center height.

 

[Ron Muhlenkamp]

The diameter of the pipe itself may distort things a bit and keep the ends from being square.
You might want to add an inch or two, make the bend and then do the final cut.

 

[Dennis(IA)]

C = 2 pi r or C = D pi. Just ask any internet. Don't do like I did and forget to divide by 2 to get half the circumference.

 

[DoubleO7]

There are online calculators that you can confirm.

PVC will kink if the radii is too small, it will also want to spring back a lot. You will have to anchor the ends.

I use to make and sell elevated dog beds out of a pvc pipe frame.
Then I drilled a few holes in the top side of frame pipes and used 1/2" pvc pipe bent into a half circle with the ends stuck in the holes. Then some cloth over the hoops making it all look like a covered wagon.

you might need to do similar with a pipe frame on the ground and hoops coming up and over into the frame.