The Triangle Bikini Top

The Simplest And Most Common Swimwear Top Ever!

The world's most popular ever bikini top has changed little in over 50 years. It's so popular it suits young and not so young, large and small busts, and can be worn with any style of bottoms you want. It comes in three general styles: a draw-string style, a flat darted style, and even a plain flat style without a dart

 

The advantage of the strings is you don't really need to care about size or cup. If one size doesn't fit the way you want you just keep going up or down a size until something does fit. The darted style sits much flatter than a draw string but tends to suit a specific cup size or two only ... this is the style preferred by most higher fashion brands as it's more aesthetically pleasing. The flat undarted triangle is the simplest to make but only fits small cups.

 

And if that isn't enough, these days you can mix and match tops and bottoms at most swimwear outlets so not only can you have different size tops and bottoms, but also different colours. Some retailers even sell tops and bottoms separately so you don't even need to buy a bottom at the same time. Heck even I'm excited by such choice.


I'm going to start by demonstrating the darted triangle. The photos below illustrate the pattern we're going to make. After this pattern, I will also show the extra steps to create a draw string triangle top. These patterns are for a size 10B/C and are not based on the one piece block but on measurements. 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.

Step One

Mark a point in the centre of your page. Square up 10cm. Square left 7cm. Square right 7cm. Square down 7cm. Create two lines 15° either side of the bottom guide line. For different standard sizes of this style, increase the horizontal by 5% per size and the vertical by 3.5% per size. This is an arbitrary style however and is not based on any block so you can really start anywhere you like.

Step Two

Square down 7cm from the end of each horizontal guide line and square off between them. This should form two 7cm by 7cm squares.

Step Three

Rotate the squares about the centre point until they line up with the 15° guide lines.

Step Four

Curve off the left and right of your triangle. These curves should be as slight as possible, being sure to keep a right angle at the bottom.

Step Five

Bring the tip of the dart about 1.5cm down from the centre point (bust point). Do not take it further away than this or the tip will pimple when worn.

Step Six

Remove unnecessary guidelines. If necessary retrace the front and back panels. 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. Finally, be sure to clearly label your pattern pieces with a title, panel name, garment size, cutting instructions, author’s name, date and revision number.

Ok So let's take a look at the Draw string triangle top.

Photos found on the Internet (I do not own copyright);
used for the purpose of illustration/education only.

Step Seven

In order to create a gathered triangle with a draw string, we need to add a little volume. We still want the same final shape so we can base our gathered triangle on the darted triangle. Trace the darted triangle and open it up as shown, a total of about 30° ... this should be enough for up to a DD cup.

Step Eight

Curve off the base of your triangle. This curve should also be as slight as possible, being sure to keep a right angle at either side. If the curve convexes too much below where the old dart sat, then there will be even more bagginess to the top than there otherwise might be with a gathered top. If it concaves above the old dart then you will find the triangle rides up on the wearer over time and they'll know it doesn't feel right!

Step Nine

Remove unnecessary guidelines. If necessary retrace the front and back panels. Add seam allowance to the pattern based on how you intend to assemble it. I've shown this pattern with 20mm allowance for a fold over casing with overlocked edge. Most industry would simply straight stitch the casing down from the inside assuming it doesn't need to stretch. I prefer to chain stitch from the outside because I'm not in such a hurry.


I would use a binder attachment to apply the elastic and casing fabric to the upper edges, so I don’t need any seam allowance on those particular seams. If you use a fold over elastic then add 10mm seam allowance to the upper edges.


Finally, be sure to clearly label your pattern pieces with a title, panel name, garment size, cutting instructions, author’s name, date and revision number.

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