How can I do the measurements to make a full circle from a wedge shape?

Question

If I have a wedge shape and want to use multiples of that shape to make a full circle with a hole in the center, is there a relatively easy formula for me to use to make or adjust the measurements. This will be done in fabric for a quilt. Please keep in mind that I am somewhat "mathematically challenged" so "K-I-S-S." My brain is already in overload--help!

Answer 1

If you want a hole in the center, then I'm assuming that your pattern shape is not a triangle, but more like a triangle with a corner cut off. Right?

The first thing you need to do is make a drawing of your pattern. Then use the drawing to measure the "central angle", which is the angle that points towards the center of the circle. To do that, extend the lines of the drawing until they meet at an angle, as if it were a true triangle. Then use a protractor to measure that central angle in degrees.

Now the tricky part, which requires some math. You need to figure out how many of these pieces you need to make a circle. A complete circle has 360 degrees, and if your central angle is a nice happy number like 45 degrees, that's great, because 360 divided by 45 is 8 exactly, which is the number of pieces you'll need. Another happy number is 30 degrees, which would require exactly 12 pieces for a circle (because 360 divided by 30 is 12).

But if your central angle is some unhappy number, like 48 degrees, you find that you'll need --- seven and a half pieces! which is a real bummer, because you don't want that extra half piece all over the place.

So if that's the case, you have a choice: either make your wedge at some other angle, OR bite the bullet and cut a fractional piece for each circle.

Answer 2

Yeah, there are ways to do it, and some ways are easier than others. I presume, that since you want to end up with a circle, that the outer edge of the "wedge" will actually be rounded somewhat, like part of a circle. (If not, you wouldn't end up with a circle, but what's called a "regular polygon" with a bunch of straight edges around the outside.)

To start out, you need to decide how many wedges ought to be in your circular quilt. There are 360 degrees in a circle, and life will be a lot easier for you if you choose a number of wedges that will divide into 360 evenly. These numbers are: 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 30, 36, 40, 45, 60, 72, 90, 120, or 180.

More wedges means longer, slimmer ones. And the longer and slimmer they become, the more the finished product will look circular, even if the outer edges are straight lines (triangular wedges), not arcs of circles (like pieces of pie).

My suggestion: Decide how many wedges you want, then email me privately (Yahoo Answers can do that), and I'll give you everything else you need to know.

BTW, I understand "quilting" is a booming activity. My sister-in-law is up to her ears in it.

Answer 3

Granny,

Im going to assume that its a symmetric wedge... that it has two long sides that are the same length, and one short side. Is that okay?

The circle isnt going to be exact.. its going to have some peaks and valleys.

The peak to peak diameter of circle is going to be twice the length of the long side.

The circumference of the circle is going to be 3.14 times the diameter.

The number of the smaller triangles you use should be this circumference divided by the length of the small side. Make it a nice round number.

I dont know if that helps.

If you know the size you want the circle (circumference) and the size of the long side of the triangle and want to find the length of the short side... just send me a message.

Answer 4

The wedge has two straight sides of equal length with an arch on the third side. The length of either straight side is the radius of the circle. Distance around the circle is = 2*3.14*radius. Divide this distance by the length of the arched side.

Answer 5

Easy way is to cut a bunch of wedges from paper first to see how many you need to make a circle.