Now that you know what our block will look like, let me show you how we will be constructing it.
Here I've broken down the block into four parts, outlined in yellow. Those are the four parts that we make and then put together to make the whole. Every "block" type design will consist of smaller parts sewn together to make one block. Then, when you make a quilt, you make lots of blocks and put them together to make one whole quilt.
The math for figuring out how much fabric you will need is a pain if you are not using a pattern that gives the directions for yardage. However, if you are using the app I mentioned above, it will tell you. There is another thing I like to use called the Fabric Calculator. This also only works for blocks and if you know the percentage of each color (up to 3) that you want. I do my math on scrap paper always and it's probably done the long and round about way. I always have one-yard cuts of fabric and I lay them out and measure to see how many strips and squares that I can cut out of them so I know how much to buy for particular projects. So, here is the unit that we will make, and we will make four for starters.
See how each cut each cut edge is folded back onto itself, while the selvage edges are opposite the fold? Now we need to know what size we are going to cut our pieces. I want to make a 4 1/2 inch block. My app tells me that I need to cut my squares 3 1/8 inches by 3 1/8 inches. One thing to remember when you are doing quilt math, is that you will always sew 1/4 inch into the fabric, also known as your seam allowance. That means, when you are doing your math, you need to remember that every edge that will be sewn (now or later) will subtract 1/4 inch from your final shape. So, if I started with a 3 inch square, but I sewed other fabric to all four sides of it, it would end up being 1/2 inch thinner, and 1/2 inch shorter. Here is a visual:
Okay, now place it on your mat, smooth it out, and we are ready to cut! This is where we get to use that sweet, sharp rotary cutter! so I am going to cut one strip that measures 3 1/8 inches wide, so I can then cut smaller blocks from that.
Cut the ragged edge off the end, and line your ruler up at 3 1/8 inches. Note that I'm not using the numbers on the mat here, I'm just counting three and one eighth over. Now, put pressure on your ruler so it doesn't slide around, grab that rotary cutter and cut (away from yourself). Now you have a lovely 3 1/8 inch strip.
Here is the part where we get our squares ready for marking. Printed fabrics have a "right" side, which is the pretty printed side, and a "wrong" side, which is the duller, unprinted side. So, grab one square of each color and put the "right" sides together and line them up.
I'm using my lovely Frixion per that disappears when you apply heat (iron). I love these! I've used all kinds of stuff to mark with though, it's not going to show up on the finished project, it will be on the back! On the diagonal, draw a straight line right through the center.
Now our fabric is marked on the "wrong" side, time to sew. I'm going to sew 1/4 inch away from my mark. Here, I'm showing you where I line my mark up. There is a 1/4 inch mark on my presser foot that I'm point to with a pencil to show. Using that as a guide, sew along one side of the line, then the other.
Here I'm sewing along the other side. Use a Chain Piecing technique to save time and thread.
Now they are all stitched together, time to trim.
Do this with all squares you made, then iron the open. I always press my seams to the darker side, so they are harder to see from the front.
Now we need to trim off those little tips! We want perfect squares here :)
Now we have out four squares. We will lay those out like this to see how our pinwheel will look.
We will do this for both halves, then iron the seams.
Now we are going to sew right up along the middle. If you have trouble keeping everything in place, use pins to keep things lined up. Crooked pieces aren't pretty! After sewing, iron that seam and voila! You have a lovely pinwheel block!