Guest Author - Iris ten Holder
Math tools for a braided rug
A burning question for anyone wanting to braid a rug is how to calculate the fabric needed. We all see the tricky problems: how do you calculate a round surface, or an oval one and then how is this spiral of braided fabric going to measure out. We also realize that braiding takes up extra slack; then we wonder how many strips go into a yard of fabric.
Sure enough, there are no easy answers.
Would it not be great, though, to be able to calculate your own yardage requirements? Once the calculations are done, they can be adapted to other sizes and fabrics by changing the variables.
A. The width of the fabric and the width of the strips. This will determine the number of one-yard strips that can be cut from a yard of fabric. One yard seems to be the optimum manageable strip length.
B. The size of the rug, and the thickness of the braid.
A. To calculate the number of strips that can be cut from one yard, take the width of the fabric and divide it by the width of the strips. For example, if the strips are to be one inch wide and the fabric is 54 inches wide, there will be 54 one-yard strips.
For joining we need to deduct 2 per strip, so the real outcome would be 54 yards minus (54x2=108) 3 yards; thus a total of 51 yards.
Therefore we know that one yard of 54 wide will yield 51 yards of fabric strips
B. To calculate the length of braid needed may seem to be tricky.
You can do this by a rough estimate, but a mathematical way to do this was published in Bittersweet as a school project.
I quote it here:
1. Draw the size rug, potholder, or cushion you want to make on a piece of paper. You will draw a circle and then a spiral in the circle OR a circle with smaller circles inside the larger circle (called concentric circles). Make sure that the space in between the circles or in between each line making up the spiral is about _ inch to 1 inch.
2. Measure the diameter of each individual circle made by the spiral.
3. To find the length of the fabric you will need to do the following mathematical problems:
- Divide each of the diameters that you measured in half. Now you have the radius of each individual circle.
- Multiply each radius by Pi (3.14). (The circumference of a circle is
2 multiplied by Pi multiplied by the radius-or the diameter multiplied by Pi.)
Add the sums together and you will have an approximation of the length of fabric needed for the rug.
End of quotation
You will now have the length, but realize that at least three strands are needed for a braid and that braiding will also need extra material. Therefore the result needs to be multiplied by 3 and then by 1.3 (an estimate)
Putting the two together you can now calculate the fabric needed for your rug.