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Choose 600D polyester or 10 oz cotton duck; cut two rectangles at 45 × 40 cm. Set seam allowance to 1 cm. Form a top casing by folding the upper edge to 3 cm and stitch 4 mm from the fold. Prepare two cords at 1.2 m each; cord diameter 6–8 mm. Use #80 polyester thread, needle 90/14, and stitch length 3.0 mm. Reinforce lower corners with four bar-tacks placed 2.5 cm from the base.
Place rectangles right sides together and sew side seams at the 1 cm allowance; backstitch at seam starts and ends. Trim allowances to 5 mm and clip corners. Turn the shell right side out and press flat. Fold the top edge twice to create the 3 cm casing and stitch it, leaving two openings of approximately 2.5 cm at the side seams for cord entry.
Install metal grommets (recommended diameter 12 mm) at the lower corners, positioned 2 cm from the base and centered 1 cm from the side seam. Feed each cord through one casing opening, route along the bottom channel and out the opposite opening so each cord forms a shoulder loop when tensioned. For adjustability, add cord locks or sliding toggles; for extra durability, topstitch a 6 × 6 cm reinforcement patch of 600D at each corner, stitched 4 mm from the patch edge.
Optional pocket: cut a front panel 20 × 18 cm, finish edges with 1 cm seams and topstitch 2 mm from the edge; fit an 18 cm zipper. Finish internal seams with a serger or a zigzag stitch to prevent fraying. Care instructions: machine wash cold (30°C) for cotton duck and line dry; avoid high dryer heat for polyester-coated trims and glued interfacing.
Select fabric and set dimensions
Choose 10–12 oz (340–400 g/m²) cotton canvas for heavy use; choose 8–10 oz (270–340 g/m²) cotton duck for a slightly softer feel; choose 210D nylon ripstop for a lightweight, water-resistant option (use a seam-sealer for taped seams).
- Fabric weight and use:
- Canvas 10–12 oz (340–400 g/m²): durable, holds shape, minimal interfacing required.
- Cotton duck 8–10 oz (270–340 g/m²): good balance of stiffness and flexibility; add medium fusible interfacing for structure.
- Ripstop nylon 210D: water-shedding, light; use nylon thread and a small zigzag or French seam to reduce fraying.
- Quilting cotton (120–160 g/m²): decorative lining only or paired with heavy interfacing for shell strength.
- Interfacing:
- Light shell fabrics → medium-weight fusible interfacing (~80–150 g/m²).
- Heavy shell fabrics → optional sew-in stabilizer or no interfacing; use leather or canvas patches for reinforcement points.
- Grain and nap:
- Align panels on lengthwise grain (warp) running vertically for maximum tensile strength along straps.
- For directional prints or nap fabrics (corduroy, velvet), cut mirrored panels; press carefully to preserve pile.
- Pre-wash and shrinkage:
- Pre-wash cottons in the finish wash cycle intended for use; expect ~3–5% shrinkage–add this percentage to cut dimensions if fabric will be washed later.
- Synthetic nylons typically not pre-washed; if washed, use cool water to avoid finish loss.
Standard allowances and hardware sizing:
- Seam allowance: 1/2″ (13 mm) typical; use 3/8″ (10 mm) for a neater edge on thin fabrics.
- Top casing (for cord passage): finished 1″ (25 mm); allow a 1″ fold in cutting calculations.
- Cord channel finished width: 1″–1.25″ (25–32 mm) for cords 4–6 mm diameter.
- Cord diameter: 4–6 mm recommended; polyester cord or 6 mm cotton rope for a softer shoulder feel.
- Cord length (single continuous loop style): adult 180–220 cm (70–86 in); child 140–160 cm (55–63 in).
- Grommet inner diameter: 6–8 mm for 4–6 mm cord; place grommet center ~25 mm (1″) above bottom edge and ~25 mm from side seam; use a reinforcement patch 50 × 50 mm (2″ × 2″) behind the hole.
Panel cutting formulas and examples (two-panel construction):
- Definitions: Wf = finished flat width; Hf = finished height (excluding casing); SA = seam allowance (use 1/2″ / 13 mm); C = casing height (1″ / 25 mm).
- Cut panel width = Wf + (2 × SA).
- Cut panel height = Hf + C + (2 × SA).
- Small example – finished 12″ × 14″: cut panels 13″ × 16″ (33 × 41 cm).
- Medium example – finished 14″ × 16″: cut panels 15″ × 18″ (38 × 46 cm).
- Large example – finished 16″ × 18″: cut panels 17″ × 20″ (43 × 51 cm).
Gusset option (optional boxed bottom or side strip):
- Flat side gusset width: 3″–4″ (finished 1.5″–2″) for extra depth; cut gusset strip length = panel height minus casing allowance.
- Boxed bottom: square off corners 1″–2″ depending on desired base depth; stitch through all layers and topstitch for durability.
Reinforcement and finishing notes:
- Use 50 × 50 mm (2″ × 2″) leather or canvas reinforcement patches at cord exit points; stitch a box + X or bartack across the patch.
- Topstitch 2–3 mm from casing edge to stabilize; follow with a 3 mm edge stitch around perimeter for a professional finish.
- For nylon shells, seal seams with seam sealer or apply waterproof tape if water resistance is required.
Cut pieces and mark seam allowances
Cut two exterior panels to a finished size of 15″ × 17″ (38 × 43 cm); include a 3/8″ (1 cm) seam allowance on all sides and cut the fabric at 15 3/4″ × 17 3/4″ (40 × 45 cm).
Cut two lining panels the same as the exterior panels; cut fusible interfacing 1/4″ (6 mm) smaller on every edge than the exterior panels to avoid stiffness in the seams.
Cut one pocket at 6 1/2″ × 7 1/2″ (16.5 × 19 cm) to yield a finished pocket of 6″ × 7″; allocate 1/4″ (6 mm) seam allowance for the sides and bottom and add an extra 1/2″ (1.3 cm) to the top edge for a folded hem.
Cut a top band for the cord channel at 4″ (10 cm) tall by the bag width plus 3/4″ (for seam allowances). A 4″ tall band folded and stitched produces roughly a 1″ (2.5 cm) channel; allow 3/8″ (1 cm) at the top and bottom seams.
Cut two side tubes (strap channels) at 3″ × (bag height + 1″) to produce a finished tube near 1″ wide; include 3/8″ (1 cm) seam allowances and an extra 1/2″ (1.3 cm) if planning to turn them inside out.
Cut corner reinforcement patches at 2″ × 2″ (5 × 5 cm) with 3/8″ (1 cm) seam allowances; increase to 3″ × 3″ when adding metal eyelets or heavy hardware.
Label every piece on the wrong side with a removable fabric pen or tailor’s chalk: indicate grainline arrows, panel orientation (left/right), centerlines and pocket placement. Mark seam-allowance lines at 3/8″ (1 cm), 1/4″ (6 mm) and 1″ (2.5 cm) where they apply.
Mark with tailor’s chalk or a water-soluble fabric pen for single layers; for multiple layers or heavy fabric, employ tailor’s tacks or a tracing wheel with dressmaker’s carbon. Cut small clip notches into seam allowances (≈1/4″ deep) at center and 3″ from the top edges to aid alignment during assembly.
Transfer all markings to interfacing before fusing and to lining before sewing. For boxed or clipped corners, draw the corner square equal to the seam depth (for a 3/8″ seam, mark a 3/8″ square) and notch slightly into the allowance so matched pieces sit flat when stitched.
Sew main body and reinforce corners
Stitch front and back panels together using a 12 mm (1/2 in) seam allowance and a 2.5–3.0 mm stitch length; select a 90/14 needle for canvas or 100/16 for heavy duck, and polyester or heavy nylon thread (40–30 wt).
After sewing side and bottom seams with panels inside-out, press seams open flat. Trim seam allowances at interior corners to 6–8 mm to reduce bulk before forming boxed corners.
Boxed corners: measurements and steps
Flatten each bottom corner so the side seam aligns with the bottom seam. From the corner point, measure and mark the depth according to desired base width (table below). Stitch a straight line across the corner at that mark; stitch length 2.5–3.0 mm. Trim the triangle tip 5–6 mm from the stitching to leave a small allowance, then turn right-side-out and press the boxed corner flat.
Corner reinforcement options
For high-stress points where cords pass, apply either an internal patch, a webbing tab, or bartacks:
– Internal patch: cut a 50 x 50 mm (2 x 2 in) reinforcement square from heavyweight fabric or nylon; place it inside, aligned with the boxed corner seam, and sew a 6 mm distance from the patch edge with a 2.2–2.5 mm stitch length; finish with a box-and-X stitch pattern.
– Webbing tab: fold a 25–30 mm wide piece of 20–25 mm webbing into a 30–40 mm tab; sew across the tab with two parallel lines 6 mm apart, then secure with a box stitch on the interior corner. Use a 100/16 needle for thick webbing.
– Bartack: set machine to a dense zigzag/bartack function; bartack length 10–12 mm, density to produce ~6–8 stitches per cm; place bartacks 6–8 mm from the corner tip along the stress line.
| Bag base width (flat) | Corner depth to mark | Recommended reinforcement |
|---|---|---|
| 8–12 cm (3–5 in) | 2.5 cm (1 in) | 50×50 mm patch or bartack |
| 13–18 cm (5–7 in) | 3.5–4.5 cm (1.5–1.75 in) | Webbing tab + internal patch |
| 19–25 cm (7.5–10 in) | 5–6 cm (2–2.25 in) | Reinforced patch + double bartack |
Final topstitching: stitch 6–8 mm from side seams and along bottom edges to flatten seams; use a longer stitch length (3.0–3.5 mm) for visible topstitching. Test a scrap seam for tension and stitch quality before completing all corners.
Create and topstitch the cord channel
Use a 2″ (5 cm) wide strip for 8–12 mm cord; increase to 2.5″ (6.5 cm) for thicker cord or when adding a stopper. Strip length = opening width + 1″ (2.5 cm) for seam allowances (example: 14″ opening → 15″ strip).
Apply 1/4″ (6 mm) lightweight fusible interfacing to the wrong side for thin fabrics. Fold the strip lengthwise, wrong sides together, align raw edges and sew a 1/4″ (6 mm) long seam to form a tube. Trim seam allowance, turn right side out, press the tube flat with the seam centered on the underside; a 2″ strip yields about a 1/2″ (12 mm) internal tunnel.
Attach and secure
Position the tube so its center sits 1/4″ (6 mm) below the bag’s raw top edge and baste with a 1/8″ (3 mm) seam through tube and top. Fold the tube up to cover the raw edge and press. Topstitch 1/8″ (3 mm) from the folded top edge to close the tunnel; add a second topstitch line 3–4 mm below the first on the body to stabilize and reduce twist. Leave 1″ (25 mm) openings at each side seam if crossing cords through opposite sides.
Machine settings, reinforcement and threading
Use a 90/14 topstitch or universal needle, polyester thread and stitch length 3.0–3.5 mm for visible, strong topstitching. Reinforce tunnel ends with a 6–8 pass bar-tack or heavy backstitch. Finish raw edges with a narrow zigzag or serger. Thread cord with a safety pin or bodkin; feed one cord end clockwise and the other counterclockwise to create a cinch loop. For donation or community-project planning consult best adoption centers for dogs near me.
Thread cords and adjust length
Use 5–7 mm polyester or nylon cord for durability; for an adult 40×45 cm (16×18 in) sack cut two lengths of 150 cm (60 in); for a child-sized 30×35 cm (12×14 in) sack cut two lengths of 120 cm (47 in). If using a single continuous cord, allow roughly 300–350 cm (120–140 in) for an adult-sized item.
Threading method
Attach a closed safety pin or bodkin to one cord end, insert into one channel opening and feed all the way around until it exits the opposite channel opening. Repeat with the second cord from the other side so each cord creates two shoulder loops when pulled. For a single continuous cord, feed from one corner, around the top channel, down through the opposite corner casing, then back up and around the other side to the starting corner.
When anchoring at lower corners use a box stitch or multiple back-and-forth stitches through the cord loop; stitch length 3–4 mm, reinforce with a bar tack 6–8 mm wide. Trim excess cord leaving 15–20 mm beyond the knot for whipping or crimping.
Length calculation and adjustment
Quick formula: cord length per strap = (desired shoulder drop × 2) + (half top width) + 20–30 cm for threading and knots. Example: 60 cm shoulder drop → 2×60 + 20 (half top width for a 40 cm bag) + 30 = 170 cm recommended per cord. For a continuous cord, double the total of both straps and add 30–50 cm for knotting.
Adjust length on finished item using either sliding knots (adjustable overhand or taut-line hitch) or plastic cord locks. To shorten permanently, untie stopper knot, withdraw cord through channel to new length, then replace knot or use a metal clamp crimp. To lengthen, replace stopper knot further along or swap for a longer cord.
Finish synthetic cord ends by briefly melting with a lighter and pressing flat to prevent fray; for natural fiber, apply a small amount of fabric glue or Fray Check and fold/whip the end. For a clean commercial look, use cord end crimps or metal caps crimped with pliers and cover with a dab of adhesive.
Attach strap ends and finish raw edges
Fold strap ends 12–13 mm (1/2 in) and stitch a 25 x 25 mm box with an X inside using bonded polyester thread; stitch length 2.5 mm, needle size 90/14 for woven nylon or 100/16 for heavy poly webbing.
- Prepare reinforcement: cut a 60 x 60 mm patch from 2–3 mm veg-tanned leather or double-layer 600D oxford; fuse a 30 x 30 mm piece of medium-weight sew-in interfacing (H180) to the fabric side that receives straps.
- Position strap: insert folded strap end under the reinforcement patch or through the channel, leaving 20–25 mm of overlap beyond the stitch line to avoid slippage.
- Secure with stitches: sew a 25 x 25 mm box + X at 5 mm from the strap edge; repeat adjacent parallel rows (2–3 rows spaced 3–4 mm) for heavy load conditions. For machine bar-tack machines, apply three 7 mm bar-tacks across the stress zone.
- Optional metal hardware: use 6–7 mm diameter rivets or stainless steel D-rings for strap anchors; pre-punch holes, add a 3–4 mm leather backing, and set rivets with a hand setter rated for upholstery.
Finish raw edges with one of the following, selected by material:
- Light woven cotton/quilting cotton: press 6 mm double-fold hem, topstitch 3 mm from folded edge.
- Medium-weight canvas/duck: serge with 3-thread overlock (stitch length 2.5–3 mm), then topstitch 5 mm from serged edge for durability.
- Heavy synthetics (nylon, oxford): apply heat-sealed tape on the cut edge using a hot-bond iron setting appropriate for fabric; trim with pinking shears before sealing to reduce bulk.
- Leather accents: burnish edges with edge beveler, apply gum tragacanth or edge paint, and topstitch through folded edge for a clean finish.
Prevent fraying and increase longevity:
- Apply Fray Check or clear seam sealant to exposed synthetic cuts; allow 12–24 hours cure before stressing.
- Stitch seam allowances down where possible: press allowances toward the exterior and topstitch 3–4 mm from the fold to lock edges.
- Reinforce corners with triangular bartacks: base 15–20 mm, height 10–12 mm, 3–4 passes per tack.
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