The Basic Tanksuit
Everything Starts Here
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 some time in her life, be it as a kid at the beach, for the school swimming team, for laps at the gym pool, during pregnancy, to hide figure problems, for simple decency, and this hasn't changed much in fifty 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.
There are two types of basic tanksuit; one in which the straps are cut as part of the garment (left photo) and one in which the straps are made from binding (right photo). We’ll start out by drafting the pattern for the garment on the left (steps 1 through 7) and then modify it for the garment on the right (steps 8 and 9). These patterns are based on the Women’s One Piece Block we created previously (using 12% horizontal negative ease and 0% vertical ease). Before you start each step, take a good look at the illustration to help you follow the drafting process. At the end of each step your draft should match the illustration.
Photos found on the Internet (I do not own copyright);
used for the purpose of illustration/education only.
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.
Draft in gentle neck and armhole curves. I tend to start just a few centimetres from the shoulder seam and gradually curve down to a slightly steeper angle at the centre 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 centre front and back than the sketch you are working from. Don't simply copy the neckline from your sketch and reduce it 12% as the only part of the garment that is going to stretch horizontally is the part that fully wraps the body.
Notice in the illustration above 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).
Of course you can change the shape of your neckline to be whatever you like … Perhaps something a little more square like the one in the photo below. Just decide on the shape at this stage as later we will rotate the top of the front panel.
Photo found on the Internet (I do not own copyright); used for the purpose of illustration/education only.
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 centre front and back. If your straps were narrow for a longer distance (e.g.; 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 to mid shoulder. 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 problems. This is also a good point at which to start discussing these signs so you recognize them in future patterns.
Problem A 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 B is where you have non parallel ripples that point to the centre 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 C 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 simply, 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 that 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 D 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 localized reduction in tension just above the breast. In most women there is a hollow area just above and centre 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). Below is a slideshow of swimwear photos I've found on the Internet (not my images/copyright) that display some of these problems and others ... can you work out what the causes are and how to fix it before I tell you?
Pattern Problem-01: Vertical ripples above the bust. The garment is too short for the wearer’s body length so has been pulled up higher by the straps. None of this is helped by having a deep front in which the garment edge is convexed, not straight. Designers seem to forget that if you want to convex the curve around the bust then it has to be help out there by something. Without that, the edge rides inwards, further exaggerating the vertical ripples.
Pattern Problem-02: being updated.
Pattern Problem-03: Horizontal ripples at the base of the strap. This indicates the tension around the body exceeds the tension in the strap. Notice however that the lowest ripples start in a line between centre back and side seam and if you follow the garment up to the bust there are ripples parallel to the garment edge. This tells me the garment is too small for the wearer (too much tension) and the strap is too long.
Pattern Problem-04: Way too much elastic tension in the neck line causing radiating ripples. There are also ripples radiating out from the bust indicating no tension except at the bust. The garment is probably too large a size for the wearer (i.e.; little to no garment tension to balance out the elastic). This garment would look terrible on the shelf!
Pattern Problem-05: Vertical ripples at the centre front of leg line. The garment is too short for the body length. The garment also shows little to no tension around the body so I’d say the designer has too much vertical negative ease and not enough horizontal negative ease for this particular textile.
Pattern Problem-06: Ripples around the armhole. The armhole is too small (not low enough) and there is inadequate tension in the elastic (which also looks too wide for this width strap).
Pattern Problem-07: being updated.
Pattern Problem-08: being updated.
So how did you go? Are you starting to see the implications of textile weight, negative ease and elastic tension?
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.
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.
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.
Remove unnecessary guidelines. If necessary retrace the front and back panels. Be sure to clearly label your pattern pieces with a title, panel name, garment size, cutting instructions, author’s name, date and revision number. Finally, 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 plus 2mm off cut) and 10mm allowance for folding over 9mm elastic. If you were to use a binder attachment to apply the elastic and casing fabric to the edge, then you wouldn’t need any seam allowance on those particular seams.
Here is how we could change the tanksuit for string straps. This is mostly arbitrary and up to your design. Start by placing the front pattern alongside the back, being sure to line them up at the bust line. This is going to be a lower design, but still try to keep the highest point above the bust by at least 8cm to avoid the elastic competing with the fabric for tension around the bust point ... this will give you a wider fit envelope within a particular size ... not seriously important but worth thinking about.
Again remove unnecessary guidelines. If necessary retrace the front and back panels. Be sure to clearly label your pattern pieces with a title, panel name, garment size, cutting instructions, author’s name, date and revision number. Finally, 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 plus 2mm off cut) and 10mm allowance for folding over 9mm elastic. If you were to use a binder attachment to apply the elastic and casing fabric to the edge, then you wouldn’t need any seam allowance on those particular seams.