The dart on the Sun Day Tank is a "Dress Maker size B" Dart. It is important to note that Dressmaker bust sizes are different than bra cup sizes. This is due to the fact that garments such as tank tops and dresses usually need to primarily fit your upper chest and bust measurements. You will notice the dart is slightly larger on the size 14-22 to help accomodate larger bust sizes. Since there is about 3 Inches of ease in the bust of this tank, there should be some flexibility on this tank fitting a variety of "dressmaker bust sizes", but keep in mind if you are having fit issues with your tank under the arm/gaping in the upper bust area, an FBA (Full Bust Adjustment) may be a good fit adjustment to consider. Scroll to end of tutorial for more information on FBA.
After marking dart leg notches (indicated on pattern), and marking dart apex, connect dart legs to dart apex with taylor's chalk or heat erase pen.
Fold dart on its side to prepare to pin.
I like to place pin tips through one side of dart to other side to make sure I am pinning accurately.
Check the pins ends are connecting to other line.
Pin dart in place.
Stitch dart at 2.5mm stitch line, at the 2/3 mark (about where awl is indicating) decrease your stitch length to 1.5mm. This helps add strength to dart tip as well as helps you stitch accurately.
When stitching, place dart on side (pins on top).
Once you reach 2/3 mark, reduce stitch length.
Do not back tack once you reach end, simply lift presser foot and pull garment away from machine leaving thread tails.
Tie a square knot at end of dart.
Tim off excess threads/
Press dart on side flat (make sure not to press past tip of dart (it will crease your bodice).
Press dart down.
Give dart a final press with with right side of garment facing up. You now have a bust dart! Dart edge should match up with your side seams so that it can be stitched into your bodice side seam.
QUICK TIPS ON BUST DART FIT ADJUSTMENTS
Getting the right fit can be tricky when working with a pattern as of course everyone is shaped differently. Differences include how high our busts sit on our frame, as well as differences in measurements from bust apex to bust apex, and the difference between our high bust and bust measurements (dress makers cup size).
Your bust dart should end about 1'' from your dart apex. If you find your dart apex is hitting right on your bust apex (creating a pointy look), you can always reduce the length of the your dart (simply draw a new dart tip 1'' inward and reconnect connect dart legs). You of course can also lengthen your dart if it is not long enough.
If you find it is hitting you too high or too low, you can adjust the position of your dart on your pattern while maintaining the dart size/angle.
Darts can also be helpful when making a "Full Bust Adjustment" on your pattern if you are finding your tank/garment is too big on your upper chest/gaping is occurring under your arms, and too small on your bust, it could be a good indicator you need to do a full bust adjustment. Select the size that is a good fit for your high bust measurement, and add desired width to the bust using a full bust adjustment process (many very helpful FBA tutorials are readily available through many YouTube tutorials). This process seems a bit intimidating at first, but once you get down the concept it actually is a pretty quick process!
I find with sewing knowing options exist is half the battle to finding solutions for sewing techniques and fit issues, so would like to point people in the right direction when possible! Small bust adjustments are also a fitting adjustments, if you find this dart is not necessary for you, keep in mind there is a Sun Day Tank without a dart as well!