I recommend using 60-inch fleece or Minky, so batting is unnecessary.
When sewing with fleece or Minky, I recommend using a Jersey needle. Size 90 works great.
If you happen to own a walking foot, it makes sewing thick or slippery fabrics much easier; however, it’s not required.
We’ll be using a zig-zag stitch, which is preferred for stretch fabrics, unless otherwise noted.
A piece of washi tape at the 1 inch seam mark on your machine will make it simpler to achieve consistent seams.
Cutting the Pieces
Start by laying out a piece of wrapping paper or taped newspapers that are the same dimensions as your outer tail fabric would be if folded in half (this should be about 24 by 60 inches.)
Then fold the paper in half lengthwise so it’s about 12 x 60 inches long. (Drawing our pattern on only one half will allow us to cut it out symmetrically.)
I’ve included a printable pattern for the fin (click link above supply list). Print and cut out, taping together as shown. Then trace or tape this piece at the bottom of your wrapping paper, so you know how much fabric you have left to create the tail.
Make the bottom of the tail the same width as the top of the fin. Draw a diagonal line from the bottom of the tail to the outer edge of the paper, then curve inward at top. Unfolded, my tail piece is 20 inches across at top and 45 inches long.
Fold your outer tail fabric in half, right sides together (for my blanket, this is the green fabric). Pin the tail piece through both layers and cut out, creating two tail pieces. Do not cut a fin out of this material.
Remove the pattern, then re-pin the two fabrics, right sides together.
Fold the lining fabric right-sides together and pin both the tail and fin pieces to the fabric. You’ll also need to cut 1 band piece along the fold. This piece needs to measure 4 x 39 inches. (I realize it says 4 x 40 in the photo, but I ended up trimming it down later, so 4 x 39 is a more accurate measurement.)
Sewing the Tail
Sew the outer tail fabrics together on the long sides, leaving both the top and bottom open. Sew with a 1-inch seam. (Minky is notoriously slippery to sew with, and even experienced sewers may find themselves frustrated when the fabric shifts and the edges don’t align perfectly. However, 1-inch seams are generous enough to account for shifting, so don’t stress if your edges don’t stay perfectly matched as you sew.)
Turn the outer tail fabric right side out.
Repeat with the lining tail fabric. Do not turn.
Slide the lining fabric piece inside the outer tail piece. Pinch the two fabrics at top and shake so the pieces align.
Adding the Band
As this was my first attempt at sewing a mermaid tail blanket, I did the next part a bit backwards, sewing it together before hemming. However, I’m going to tell you the simplest way to do it.
Fold under the long edges of the band piece ½ inch and hem with a straight stitch.
Then fold the band piece in half, right sides together, so the short ends meet. (Please ignore the fact that my edges are unhemmed in the video clip, yours should be hemmed.) Sew the short ends together with a zig-zag stitch and a 1 inch seam, creating a loop.
Fold band in half lengthwise, wrong sides together. Sandwich the two tail fabrics in between the folded band fabric and pin all the way around.
Topstitch along your previous row of stitches.
Sewing the Fin
Sew the fin pieces right sides together, with a 1 inch seam. Leave the top open.
Clip and notch your seam allowances, being careful not to cut your stitches. Turn right side out.
Slid the tail inside of the fin piece. Turn down the raw edge of fin piece ½ inch and pin.
Sew straight across the folded portion of the fin piece, securing all layers.
I used chalk to sketch out some lines on the fin. These add a bit of texture and dimension. I’ve found it’s easiest to start sewing at the bottom of the fin and work towards the top. If you’d like, you could also topstitch around the entire edge of the fin piece with a ¼ inch seam.