Swimwear Sewalong ~ Pattern Adjustments

Helen Cloke ava briefs boylston bra pattern adjustments swimwear sewalong

If you are sewing along using a swimwear specific pattern then happy days, you can just jump right in to cutting out!

If, like me, you are converting bra and underwear patterns then there will be a few changes you may need to make in order to convert them to swimwear.

I'm using the Boylston bra by Orange Lingerie as a bikini top.  I know this fits me well and has the retro vibes I'm after.  For the bottoms, I'll use the Ava high waisted panties by Ohhh Lulu.  I think these will be the perfect pairing and also show off the printed fabric nicely.

Even though I'm using these patterns, the adjustments I'll cover below could be applied to quite a few different patterns.  If there is a pattern you are using and you would like some feedback on what adjustments to make then feel free to ask!  Facebook and Instagram @nelliejoans are the best places to do this as you'll not only have access to my input but to all the knowledgable followers as well.

Boylston Bra adjustments:


No adjustments are necessary for the three cup pieces if you are planning on finishing the top of the upper cup/neckline with elastic and turning it under.

I've decided that I'm going to do a bound finish to the neckline of my bikini so I'll need to remove the seam allowance from the top of the upper cup piece (shown drawn out in pink)

Emerald Erin has a great tutorial here on different neckline finishes where she explains a bound finish.

Foam Cups:

If you are going to add foam to your bikini bra and your pattern doesn't come with foam pattern pieces you'll need to create some.

I printed a duplicate copy of the three cup pieces.  You'll need to remove all the cross cup seams.  This is because the foam pieces get sewn with the edges butted up together eliminating the need for seam allowances.  You can see I've removed the SA from where the inside lower cup and outside lower cup meet and then again where the tops of these pieces meet the bottom of the upper cup piece.  

You'll also need to remove the seam allowance from the top of the upper cup piece and the underarm, anywhere there will be a finished edge (not attached to another piece.)  Otherwise, you'll end up with a bit of foam folded back on itself, just like a seam allowance, and that would get bulky.

Keep the seam allowances on the edges where the cup will meet the frame, so basically, where the underwire goes.

Amy from Cloth Habit has a detailed explanation of creating foam cups here.

Bridge and Frame:

Measure your seam allowances for where the underarm and band elastic is to go and check these against the width of your swimwear elastic.

We will be replacing the traditional plush/picot lingerie elastic with swimwear suitable elastic.

I'm using a 9mm wide rubber elastic.  The allowance for the underarm elastic is 9mm so I don't have to change anything here.

The allowance for the band elastic is 12mm.  I could cut off the extra 3mm, (shown with the pink line) but in the past I have left this small amount on just to give me a bit more depth in the band and room for turning under the underwire casing and it has been fine.


Here is where I have made the most changes.  I wanted a more clean back band rather than a typical 'bra' looking one.  

The original piece is shown in pink: I traced this on to paper.  The side of the band where it joins onto the frame (shown on the left in the photo) needs to stay the same.

The hook and eye connector will be changed for either a clicker clasp or a g-hook (or you could do fabric ties) in my case I decided to use a g-hook.  Because these are attached a little differently than the hook and eye you need to allow room for the band fabric to loop through the connector and then back on itself.  To do this I extended this piece of the band by 5cm.  This number is not exact, I just wanted to allow wiggle room knowing I could remove it later.

I extended a line across the bottom of the band at 90 degrees to the side seam.  If your pattern piece has a more exaggerated downward hike than this one you may want to keep more to the original angle.

The width of the new extension for the connector needs to be the gap of the connector, where the fabric will feed through, plus an elastic allowance for both the top and bottom.  For example mine is 22mm (g-hook) plus 9mm elastic for the bottom band plus 9mm elastic for the top of the band.

Create a new line to the top of the band by connecting the top point where the band meets the frame down to the new extension.

You could also extend a mark/notch down from where the back of the straps meet the band so give you an idea on where these should attach but I generally do this by trying it on to get the best feel for where the straps should go.


There is a pattern piece for a front fabric strap for the Boylston bra but I think I'm going to make skinny straps from swimwear elastic and the swimwear fabric.  So I can discard this pattern piece.

Ava Panties Adjustments:

Leg holes:

The Ava panties are drafted to be finished with fold-over-elastic at the leg and waistlines.  So the edges of the pattern pieces are the finished edges of the garment.

We will be finishing our swim bottoms with swimwear elastic so we need to add allowances for attaching elastic and turning it under.

Add a seam allowance the width of your elastic to the leg holes.

DISCLAIMER: I don't do this with the Ava pattern as I know they fit me well with slightly less width through the leg holes and crotch so I leave the pattern pieces as is. 


If you are finishing the waist with elastic you'll need to do the above to the waistband too.

At this point I haven't decided whether I'll finish the waistband with elastic or use a fabric band.  With the fabric band a seam allowance will have to be added to allow for attachment.

With that done I can now get cutting out!  Are you having to make any pattern adjustments? 

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