3D Corners, Turns and Tight Curves

How to Sew Boxed Corners, Gusset Turns, and Tight Curves

3D Boxed Corners

I'll let you in on the secret to clean crisp 3D boxed corners. It comes down to one simple trick!

3d corner graphic Boxed corners are used when assembling the last panel to a backpack, often the bottom panel. Last thing anyone wants is to end up with slouchy, wrinkly corners in the final step. By planning ahead, that last panel sews in perfectly without fuss or seam ripping.

The trick is to always respect your seam allowances.

Here's how it's done.

  1. Sew panels 1 and 2 right sides together (RST) but stop short of the bottom edge, reserving seam allowance for the bottom panel.
  2. Align panels 1 and 3 seam line and sew RST and again stop short of side seam allowance.
  3. Align panels 2 and 3 seam line and sew RST. Backtack to lock your seam.
  4. Go back and reinforce your corners with short backtacks to close any small gaps.
  5. To reduce seam bulk, trim the corner seam allowance. Be sure to leave ~1/8" (3mm) of seam allowance!
  6. The boxed corner should have three distinct seam lines and now ready for seam binding

Turns & Tight Curves

Beginners frequently ask how to sew clean turns and tight curves. Unfortunately there' no magic involved!

Sewing a gusset around a 90 degree turn or small radius curve easily ends in puckers and wrinkles. My Everyday Fanny Pack calls for several tight curve corners and trips up a lot of new sewists. With a little patience, practice, and the right technique, your pack will stand out.

Here's my method.

  1. Align your panels at their seam lines, paying close attention to pattern notches and alignment marks.
  2. Make small relief cuts along the edge of fabric panel which will curve or bend around a corner.
  3. Don't cut too closely to your seam line or the fabric may fray, or worse, the stitches may pull out.
  4. For a corner turn, one relief cut at the turn location is adequate.
  5. For a tight curve, spread relief cuts every 1/2 inch or so. For very stiff fabric, add a few more relief cuts.
  6. Mind your seam allowances when sewing and finger press the fabric flat as you go.
  7. Sew with a small stitch length, about 2mm or 10-12 stitches per inch
  8. Go slow! Stitch in short increments. With needle down, rotate your panels. Be precise!