Good panel and gusset layout is critical for getting the most bags from the least amount of yardage.
You start by choosing your size panels as they determine how much fabric you will end up using. I always use 13-by-15-inch panels. With their corresponding gusset, they made a nice size bag that isn’t too large or too heavy when filled.
More importantly, if you include the selvedges, a 13-by-15 inch panel fits neatly into both a 45-inch width fabric and 60-inch width fabric with zero waste. I always use the selvedges unless they distort the fabric. I paid for that cloth and using the selvedges is the only way to approach zero waste. The selvedge doesn’t show very much on the finished bag panels (as a very narrow border of color on one side of a panel) and it doesn’t show at all on the gusset.
Using 13-by-15-inch panels means a gusset length of 43 inches. A forty three inch gusset fits nicely within a 45-inch width of cloth.
If you choose to use 14-by-16-inch panels, you will need correspondingly more cloth for your layout and those panels don’t fit neatly into any of the standard cloth widths. Moreover, 14-by-16-inch panels require a gusset length of 46 inches. You cannot skimp (I’ve tried!) and try to squeak out a gusset using 45-inch-wide fabric. You come up short every time.
Besides using the selvedges, I use the fabric both on the straight and the cross grain. The most important part of laying out the panels is that they are on grain, but the direction (straight or cross) doesn’t matter unless the pattern motif has a strong direction of its own. I’ve not seen a difference in sewing or handling as long as the edges are true. I’m very careful to not cut my fabric at an angle to the grain as the bag can develop a twist when sewn. This issue won’t normally come up unless you are trying to use smaller pieces of irregular fabric left over from some other project.
Using the cross grain also means that I can be more flexible in how I lay out the gussets. A gusset for a 13-by-15-inch panel will be 43 inches long. That fits very nicely into a 45-inch width of fabric. A group of gussets cut this way will result in a long strip of waste fabric 2 inches wide that can be repurposed as a trim line. I can be flexible in my gusset widths so if I have slightly less fabric, I can cut 7-inch gussets as opposed to 8- or even 9-inch ones. For example, if I have a 63-inch-long piece of fabric, I could cut seven 9-inch wide gussets or I could cut nine 7-inch wide gussets. That could mean the difference between two more complete bags (matching my gussets to my panels) or more spare parts in the Frankenstein pile.
If I must cut my gussets on the straight grain, a 45-inch width of fabric can be divided several ways. It can be cut into five 9-inch-wide gussets or six 7-1/2-inch gussets with zero waste. If I insist on 8-inch-wide gussets, I will still get five gussets along with a 5-inch-wide strip of waste fabric.
Unless orientation of patterned fabric matters, always go for the most efficient layout and don’t worry about the grain.
If you are using stash or repurposed fabric, you will need to know exactly how much fabric you have and its width. True up the raw edges so they are straight and then measure the length.
I’ve provided a wide variety of charts and layouts to help you figure out on paper how your panels and gussets show lay. Some of them give exact yardages if you are buying fabric. Other charts give you measurements so if you are repurposing a tablecloth or a curtain you can calculate on paper how the panels and gussets should lay before you start cutting.
You always want to use the full width of the fabric along with the full length. You also have to allow a few extra inches in length (but not width) for cutting error. In woodworking, this is called kerf and it means the thickness of the saw blade. When you cut wood, you have to measure and mark your line, cut the part off, and then measure and mark the next cut. You can never make all your measurements followed by all your cuts because the act of cutting with a saw blade will, all by itself, eat up wood, throwing off the final size.
Scissors and rotary cutters have a much smaller kerf than a saw blade does, but there is some and it does accumulate over many parallel cuts in the length of a long piece of fabric. I always allot a few inches over what my measurements indicate I need to allow for this. Pulling threads also uses up fabric. The width of two pulled threads doesn’t seem like much, but again, when you pull threads, in parallel sets across the length of a piece of yardage, it adds up and you find yourself with that last set of panels being a little smaller than you had planned on.
I haven’t noticed that kerf matters in the width of fabric. This is because you aren’t making as many cuts. A 45-inch-wide piece cuts into three 15-inch wide panels. Those two cuts don’t add up to anything. A 60-inch-wide piece of fabric cuts into four 15-inch-wide panels. That one additional panel might use up another millimeter of cloth in the cutting; not enough to worry about. Gussets have a built in fudge factor. They can vary in width slightly without it mattering at all. Thus, if I am cutting my gussets and it looks like the last one will be too narrow, as I near the end of the fabric, I can readjust my width for the remaining ones to compensate. Three slightly narrower gussets are much better than one much too narrow gusset.
When I lay out my panels and gussets on repurposed cloth, I start with my measurements, paper, and pencil. The first step is deciding if I have to cut the panels a certain way to make them look right. The motif on the fabric determines this and only you can make the decision.
Then, after I’ve decided, I draw my first rectangle. On it I sketch out a set of panels on the left side, marking how much fabric they will use. On the right-hand side of the rectangle, I sketch out my gussets, enough of them to match up with the panels. I subtract those measurements from the total width of the fabric. How much fabric do I have left?
I draw a new rectangle and I use that shorter measurement to sketch out another set of panels on the left side and another set of gussets on the right side of my new rectangle. Eventually, even on the longest piece of yardage, I meet in the middle. I usually have some waste fabric, too narrow for panels. It may be wide enough for another gusset for the Frankenstein pile but I won’t know for sure until I cut my way towards it. I cut from both sides: sets of panels and sets of gussets working towards the center. That excess fabric in the middle may gradually get absorbed and when I’m done cutting, my waste scrap isn’t as wide as I thought it would be. When this happens, you are seeing kerf in action.
The moral is to always allow a few extra inches of cloth to ensure you don’t come up short in measuring panels. If you have to, fudge the width of the gussets (but never the length).
If my cloth is unusually shaped or I’m working with a lot of scraps, I will draw several pictures to end up with the most efficient layout. Once you’ve set scissors to cloth, you cannot go back. Spend the time drawing layouts and save yourself the headache of coming up short.
(This post is a draft from the upcoming book “Sewing Cloth Grocery Bags.” A complete list of the posts can be found here.)