How to Make a Tank Top Pattern, Part 1

Whew! What a week! Drawing up all of these little illustrations sure does take a lot of time. It’s pretty fun, but think next time this would be much easier do with a video.

To make the tank top from my last post (perhaps we should name this pattern- any thoughts?), you’ll first need a set of basic patterns. Most home sewists call them slopers, which is okay, but know that the term “sloper” actually refers to any pattern that has no seam allowance, not just apparel patterns. For this tank top exercise, you’ll need either a set of bodice slopers, or a basic pattern set (fitting shell) from one of the Big 4 pattern companies.

A bodice sloper set has two pieces to it, both of which can be cut on a fabric fold to make a whole bodice. The front bodice usually has two darts (one at the side seam or armhole and one at the waistline), but sometimes they are drawn up with one, like mine, or three dart options. The back bodice piece will have a waist dart and usually has a shoulder dart as well. Sometimes the shoulder dart is eliminated, but that depends on the curve of your upper back. Slopers have no seam allowance or wearable ease, but this is added later on so that they can be turned into useable patterns.

A commercial fitting shell pattern usually has two front darts (at the side seam or armhole and one at the waistline), and two back darts (one at the waist and one at the shoulder seam). This pattern is different from a sloper in that it has seam allowance added to it, and sometimes also a slight bit of ease. If you purchase one of these pattern sets, you should follow the information included with the pattern to create a muslin and test and adjust the fit.

If you are working from a purchased fitting shell, don’t forget that it has seam allowance. You will want to draw your seam lines all around the perimeter of each pattern piece if they don’t already have them marked. Take this seam allowance in to consideration when you are adjusting the pattern. With a sloper, you add in the seam allowance later, so my illustrations do not have seam allowance included.

This is not a post on how to make your own slopers or a fitting shell. There are several online tutorials for that (and quite a few books), and I recommend that if you do make your own, you use a combination of flat pattern and draping to find the shaping and dart lengths that are correct for your unique curves. If you use the basic commercial pattern, you may find that the darts, torso length, or side seams need to be adjusted. Your shoulder seams should lay flat, your darts should point to your apex, your side seams should follow the middle of your upper arm and the pattern should end at your true waist.

Many pattern making books will help you with fitting the basic bodice pattern—and the skirt, pants and sleeve. I recommend finding a vintage book, similar to my copy of the Better Homes and Garden Sewing Book from 1961. I often find that vintage and antique sewing books have far better fit solutions and diagrams than modern books.

Once you have adjusted your basic pattern to correctly fit your torso, you are ready to manipulate the basic pattern to make the tank top. Be sure to trace off the pattern so that you can go back to square one if you need to.

The first thing you can adjust is the neckline. The current pattern likely lays right around your neck, touching your top thoracic vertebrae (it doesn’t turn when you twist your neck) and the hollow at the base of the front of your neck. You may choose to create a low scoop neck, like I did, or you may square yours out.

When you alter the neckline, you will not only drop it in the front and back to bring it away from your neck, but you will also move the neckline out along your shoulder seam.  It can help to measure from your high shoulder point (where your neck and shoulder seamline meet)  out along the shoulder seam until you reach a comfortable distance that will let you make a smooth neckline. I dropped mine back 1.5”. When altering neck and strap lines, be sure that the new lines intersect the shoulder seam, center front/back and side seams at a 90º angle for at least 1/4”. If they do not, you will end up with tiny V-shapes or points on your shoulders, center lines and side seams.

Your tank top strap width can also be adjusted. I’d recommend that you keep your strap wide enough to cover your bra strap, but if that doesn’t bother you, make it as narrow or wide as you wish. Remember to compare your shoulder seams as you adjust the neckline and straps, to ensure that they will line up correctly once sewn. Smooth the armhole and neck curve after you decide on a strap width, and cut off the excess width.

Now comes the fun part! I’m not sure how many of you have played with flat pattern before, but it’s quite addictive. If you’re working with a purchased pattern, draw all of your dart legs so that they continue on and meet at the apex (point along the bustline where the darts point to). You may want to trace off another bodice front at this point to play with dart manipulation. If you cut out the original darts, but leave them connected to the rest of the bodice at the apex, you can then create lines anywhere else on the bodice you’d like and have them meet the apex to move the darts around on your bodice pattern. You can close or open your darts in any area you want and retain the same bust shaping. Remember those three original bodice samples I showed you at the top of this post? They all have the exact same amount of shaping for the bust, the single large dart has simply been moved around. Fascinating, right?

For this tank top, we’ll put some of the dart shaping into a side dart, and leave the rest un-sewn, to hang below the bust and give ample room at the waist. The key for this garment is that you don’t want to have a very deep side dart. The larger your side dart is, the more the fabric will pull around your bust, which means it won’t hang smoothly over your stomach. You want the dart to give you some shaping so that the top doesn’t just hang straight off the bustline, but curves around the breast very slightly and pulls the fabric in towards the body.

I have fairly deep front darts on my sloper because the difference in circumference between my bustline and my waistline is quite large. That being said, my side dart for this tank top is only 1.5” deep. I used my hip measurement to help me determine this. Before you officially decide on a side dart depth, you’ll want to extend your pattern side seams.

Measure from your waistline down to where you’ll want the finished hem to be. Extend the center front length by this amount. I added 9.75 inches.

Now, take the measurement of the front of your hips. If you aren’t sure exactly where your side seam line should be, you can take your full hip measurement and divide it by two; 1/2 for your front, 1/2 for your back. Draw a perpendicular line from the bottom of the waist-to-hem mark. On this line, measure from the extended center front over to HALF of your FRONT hip measurement, and make a mark. We only use half of the front hip because we’re only make half of the front pattern. If your body is built so that your abdomen is larger than your front hip, use your front abdomen measurement instead of your front hip measurement.

Choose where you’d like to have your dart located on your side seam. I recommend that it is about 1” below your armhole. Draw a line from your dart location on your side seam over to your apex. Cut along this line, being careful not to clip thru the apex. Your lower waist dart should be completely cut out so that you can more easily see where your dart legs are.

With the side section of your sloper attached at the apex, carefully begin to swing this piece until a line coming down from the side seam would easily touch the front hip line marking. Extend the side seam down to the hem.

 

Right now, this pattern piece has quite a bit of ease thru the waistline. You have your pattern’s unsewn waist dart which is left open so the pattern doesn’t curve in at the waist. We’ll address this a little later on when we adjust the fit of this pattern and give it a bit more shape, but if you’d like to go ahead and smooth out the waist curve of the pattern, you can do that now.

Draw up your pattern fronts, and we’ll work on the pattern back pieces next. Don’t worry about fit adjustments, altering dart points or adding seam allowances and ease quite yet- we’ll get there!