August 6, 2014

Tutorial: How to grade up the Bombshell swimsuit

There’s still time for swimsuit season! Like many of you, I’ve had my eye on Closet Case File’s Bombshell swimsuit, which surely lives up to its name. However, unfortunately it only goes up to a size 18, which just isn’t large enough for some of us. Therefore, I graded the pattern up to make my version, and I thought I’d share a quick tutorial in case you want to as well. It’s well worth it – the pattern looks amazing on curves!

1. Do some maths (don’t worry, it’s easy)

The Bombshell swimsuit has negative ease, which means that the pattern is smaller than your body measurements. That makes it slightly trickier to grade than usual, but it’s still straightforward. The table below shows the largest size in the Bombshell (size 18), and how I graded up to my measurements. You can simply put your measurements in, and do the same calculations to figure out how much you need to add.

What we’re doing is following the same proportions as the original sizing. I’m rather top heavy, so as you can see, my bust is 48″, so my final swimsuit size is 41.5″. The size 18 has a bust measurement of 38″, so I have to add 3.5″. I have to then add 2.5″ to the waist, and nothing to the hips, I’ll just use the size 18.

For the purpose of this tutorial, I’m going to assume you need to grade up all the measurements.

2. Let the grading begin! Start with a Full Bust Adjustment on the Front Bodice
Doing an FBA is better than just adding at the side seam, because it changes the shape of the top, and adds any necessary length. As I am mostly bigger on my front, I’m adding all the extra bust measurement (3.5 inches) on the front bodice. However if you’re bigger all around, you could do a smaller FBA on the front and also add a bit to the back.
a) cut the piece at waist level – this lets you adjust the bust first without changing all the rest of the proportions
b)  Mark your bust point first, then draw a line straight down, one diagonally up to the armpit, and one diagonally down to the side seam (don’t worry too much about this being exact – as long as the shape looks like this you’ll be fine).
c) cut up the vertical line, and across to the top line, stopping just short of the seam allowance. Spread the pieces so that the vertical gap is the amount you need to add. Remember, this is HALF of the required addition as there are two sides. So for me, it was 1.75 inches.
d) cut the other diagonal line, starting at the side seam and ending just short of the bust point so there’s a little hinge. Pull the lower piece down until the vertical gap has parallel sides.
f) if you’ve added a lot, the bottom of the two pieces is now not horizontal. Cut through the shorter side piece horizontally (anywhere below the apex), and move the piece down until it matches the longer side.
3. Grade the rest of the Front Bodice
Trace around the new bodice piece, and reconnect the lower piece.
The FBA has added width to the piece – in my case, it added enough waist space that I don’t need to grade more (in fact, it added a little more than I need, but that’s OK!).
If you do need larger waist and hip pieces, then simply add at the side seams and blend together the side seam of the top and bottom pieces. For these, divide what you need to add by 4, as you’ll be adding extra on both sides of the front and back bodices (so, if you need to add 2 inches to the waist, add 0.5 inches to this piece).
4. Grade the Front Lining to match the Front Bodice
Trace around the top of your adjusted front bodice piece, down to about waist level. Lay the front lining piece over it, and then add in the additional room you need at the side seam (sorry this isn’t easy to explain, but I think the picture is clearer!). Note that if you added *length* to the front bodice, you should add length to the front lining as well.
5. Grade the Crotch (sexy, huh? I’d give you an A)
Trace around the adjusted Front Lining piece. Lay the crotch piece over it, and then add in the additional room you need at the side seam again (sorry apparently I missed a photo on this, but it’s exactly the same as above!)
6. Grade the Back Bodice
This is simpler than the front! Simply add to the side seams. Again, divide what you need by 4, so if you need to add 2 inches, add 0.5 inches to the side seam. Also, remember the side seam (counterintuitively) is the *straight* edge. Note, if you added length to the front bodice, you should add length to the Back Bodice as well.
7. Grade the Back Lining to match the Back Bodice
Trace around the adjusted Back Bodice piece. Lay the Back Lining on top of it, and add in the additional room at the side seam.
And there you have it! A graded up Bombshell.
A couple of other things to bear in mind when making a plus size bombshell:
– Don’t cut the little bust piece that goes over the bust ruching until you have finished the front piece and done the ruching. It’s going to be a different size to the original pattern piece, but you won’t know the exact dimensions until you’ve made your front piece.
– If you are putting some kind of bra in (and I’ll do a follow up tutorial on that!) you may need to change the height of the back piece – I made less of a curve on the back to cover up the bra strap
– You may want to convert from halter straps to regular straps if you have a larger bust like me – the most secure thing is to use bra strap elastic and cover it in swimsuit fabric.
I hope this is helpful – if you have any questions, ask away!

14 thoughts on “Tutorial: How to grade up the Bombshell swimsuit

  1. gMarie says:

    Jenny – I love this. thank you for sharing the maths. I’ve been wanting to make this, but I just don’t quite fit. Can’t wait to see your version. g

    1. Jenny says:

      Hope it’s helpful g! Hoping to finish up mine tonight…

  2. ~GG~ says:

    I love it! Especially since you did it in quarter scale and walked through the transitions.
    It’s also nice to see the numbers all lined up, including the negative ease on pattern vs. what you gave yourself. I’m excited to see how it looks on you after you sew it up with that negative ease. Totally helps me think about how I am transitioning some patterns from woven to knits… more on that later!

    I’m trying out Kitschy Coo’s drafting of a swimsuit. I’m excited to draft a suit. 🙂

    1. Jenny says:

      Ooh self drafting! Can’t wait to see how that turns out

  3. Michelle says:

    Thanks for sharing this, and wow, that’s a lot of negative ease. I can’t wait to see yours made up.

    1. Jenny says:

      It is but it worked! Post to follow….

  4. Honora says:

    I am so glad that you are addressing this issue! You and I have very similar measurements. Whew! I won’t have to be a neurosurgeon to figure this all out.

    1. Jenny says:

      Great! I hope it works well for you

  5. Ann says:

    Thank-you for this tutorial. It I very,very helpful!

  6. Very helpful tutorial. Many things for sharing. 🙂
    Swimsuits Direct

  7. nicole salcido says:

    How do you mod if you have a 27″ chest?

  8. EE says:

    Thanks for the detailed directions! I’ve never made a garment before, never graded anything before, and it came out great!

    Some tips for those who are beginners and grading up – just like if most of your extra bust measurement is in the front you should probably put the entire additional room into the front bodice, if you’ve got most of your extra waist measurement in the front (belly!) you should put that additional room into the front piece as well, and if you are gifted in the rear, extra hip measurement could go mostly to the back. Look at yourself sideways in a mirror for help making a decision. It won’t do you too much damage if you just divide it equally as the suit is pretty forgiving, but it will make your side seams less zig zaggy and probably fit better. Also, don’t forget to make sure the greatest degree of stretch is width-wise to your body for the main body panels – it will still fit but it might be harder to get on over the hips especially if you install a full bra.

    If anyone more knowledgable wants to correct the above please do, but that’s what I learned with my first up-graded Bombshell!

Let me know what you think!