The Basic Tanksuit

So the basic tanksuit might not be your idea of sexy or even exciting. I doubt many designers even grant it the consideration it deserves. I do promise, however, you won't underestimate its complexity by the end of this pattern lesson!

The tanksuit is without question the most successful swimsuit design in history. Almost every woman has had at least one at sometime in her life, be it as a kid at the beach, for the school swimming team, for laps at the gym pool, during pregnancy, too hide figure problems, for simple decency, and this hasn't changed much in forty years. Not everyone in the world can wear a bikini, and as much as you might feel the fashion industry pushing you to believe that barely there is where it's at, commercially speaking it isn't. The world's biggest swimsuit manufacturers all make tanksuits in one form or another.

The sketch below illustrates the pattern we're going to make. This pattern is based on the size 10B/C one piece block we created previously (using 12% horizontal negative ease and 0% vertical ease). Before you start each step, click on the link marked "Illustration for this Step". A pop up window with an illustration for that step will help guide you through the instructions. At the end of each step your draft should match the illustration.

Step One

Illustration for this Step

Draft a guideline from the bust point to form a right angle with the shoulder. Duplicate this angle in exactly the same position on the back block. Draft in guidelines either side of the first which represent the width of the shoulder strap of your design. You can go as narrow or wide as you like, just remember that as you go narrower you need to shorten the strap to maintain an even tension. In principle, the width of the strap should be determined by function. A larger bust might benefit from a wider strap for support of the bust and comfort at the shoulder (think bra). Active lap swimmers benefit from slightly wider straps because they tend to stay in place better and hence rub less. Wider straps balance a larger bust aesthetically, while narrower straps can sometimes make a bust look larger in smaller women.

Step Two

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Notice on the illustration that the neckline and armholes all meet their respective seams at exactly the same distance above the bust line. I make this point to demonstrate the principle of tension lines. Because the pattern is reduced to 88%, if you were to cut any one of these features below the other you would break a tension line running around the body and cause the garment to distort. If you wanted to cut, say, the back line lower you could still do this but you'd need to reinforce the tension line by some other means (see The Science of Tension Lines section).

Draft in gentle neck and armhole curves. I tend to start just a few centimeters from the shoulder seam and gradually curve down to a slightly steeper angle at the center front and back. Whatever neckline you draft, it will appear 12% wider on the body. So you need to draft a neckline slightly steeper angle at the center front and back than the sketch you are working from. Don't simply copy the neckline from your sketch and shrink it 12% as the only part of the garment that is going to stretch horizontally is the part that fully wraps the body.

Step Three

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Reduce the length of the back strap a certain amount based on the width of the strap. In this example I've shortened it 2cm for a 3cm wide strap that has a gradual slope to center front and back. If your straps were narrow for a longer distance (eg; maybe you chose a squarer neckline) then you would need to shorten some more. I can't tell you exactly how much you need to shorten, only indicate where, when and why you need to do it. How much depends on the design choices you make. I do prefer to take it out of the back strap rather than the front for two reasons. Firstly the back strap has a longer narrow portion which means it stretches more. Thus when the tensions even out on the body the shoulder seam will move forward. Secondly, the weight of the bust will cause an increase in tension above the bust line and slightly lower it below the bust line (it's not proportional because the tension around the body is acting to lift the bust). The increase above the bust line will also pull the shoulder seam forward. All this is a long winded and complicated way to says you need to move the seam back so why not do it when you shorten the strap. You do need to understand these principles to know how to tweak patterns and solve fitting problems.

Now you could stop at this point, add your seam allowance and labels and make the garment and it's quite likely that it'll fit just fine. If it doesn't I'm almost certain it's one of the following common fitting problems.

Problem one is ripples in the garment that run horizontally, are longest at the bottom and gradually disappear as the strap gets narrower. They also do not extend all the way to the seams but sit central to the base of the strap. This is indicative of greater tension in the horizontal than the vertical. It can be caused by the strap being too long, or the person being in too small a size. If the rest of the garment fits well then shorten your strap by gradually pinning out the strap until the ripples disappear, but no more.

Problem two is where you have non parallel ripples that point to the center front and back and appear to travel up the neckline. This is caused by excessive tension in the elastic (generally) and the garment is trying to compensate by pushing the straps off the shoulder hence increasing the tension in the neck line. Sound counter intuitive? The shoulder is sloped so it's only natural for the straps to slip off in order to relieve tension, but as they move the length of the neck line increases more than the length of the armhole. This continues until a balance occurs between these forces however it results in ripples. It may feel wrong, but lowering your elastic tension can often keep the strap on your shoulder.

Problem three is where ripples occur parallel to the straps. The ripples are central to the strap and don't tend to extend all the way the bust. Quite simpl, your straps are too short. Look at the shoulder seam. If it's too far back then you took too much out of the strap. If it's central then I'm guessing this garment is also not covering the bust properly, riding up the bottom and your client is telling you it's too short! Check your client's total body length. The shoulder straps are the first place body length errors show up (even if the rest of the garment appears to fit properly).

Problem four is where ripples occur on the front only. They are located at the base of the strap and above the breast. They are not parallel, but seem to point toward the base of the arm hole. This occurs when there is a localised reduction in tension just above the breast. In most women there is a hollow area just above and center of the breast. This hollow often increases in size as bust size increases but not necessarily. The garment cannot follow this hollow contour. Instead there is a tweak to counter act it by taking a dart out of the neckline. Draw a line from the bust point to form a line at right angles with the neckline (see step three's illustration). Proceed to step four.

Step Four

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Trace the entire front shoulder section and rotate it about the bust point as shown. How much you rotate depends on how much error you're trying to correct. I have always automatically rotated the front strap of a tanksuit to the vertical position, closing off a small dart of about 1.6cm.

Step Five

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I also like to move the side dart to a lower position on the side seam (sometimes called a French Seam). This is an important step for retail swimwear as you can never be sure exactly where there bust line will be on your client and you don't want your dart being higher than the bust. So why not lower it by default? Mark a point about 4-5cm below the existing dart and draw a guide line from there to the bust point.

Step Six

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Trace and rotate the section upwards to close out the old dart and create the new one. Just as you do for non-stretch, bring back the dart point back from the bust point, but only slightly (about 1-1.5cm will do). The further back you come the sharper the dart will be when closed. Sharp dart points may work well for non stretch fabrics, but in stretch the tip of the dart will rise as the surrounding tension evens out (called pimpling) which looks awful.

Step Seven

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Remove unnecessary guidelines. If necessary retrace the front and back Panels. Be sure to clearly label your pattern pieces with a title, panel name, size, cutting instructions, author’s name, date and revision number. Finaly, add seam allowance to the pattern based on how you intend to assemble it. I've shown this pattern with 10mm allowance for overlocked seams (8mm to blade, 2mm off cut) and 10mm allowance for folding over 9mm elastic.