Michael Turner
Materials: exterior: 10–12 oz cotton duck or 600D polyester; lining (optional): 7–8 oz quilting cotton; fusible woven interfacing 1.5–2 oz applied only to the top casing if fabric is lightweight. Thread: polyester core, size 50. Needles: 90/14 for heavy textiles, 80/12 for lighter. Stitch length for seams: 3.0–3.5 mm; topstitch: 2.8–3.2 mm. Use a walking foot for multi-layer seams.
Cutting and allowances: cut two rectangles 16″ wide × 18″ high. Mark a 1/2″ (12 mm) seam allowance on all edges. For a boxed bottom, fold each lower corner and mark a 2″ square; stitch across the square at 1.5″ from the corner to create a 2″ depth. Add a 1/2″ seam allowance when attaching a front pocket; pocket size example: 8″×7″ cut with 1/2″ allowance per side.
Casing and assembly: create the top channel by folding 3/8″ then 1″ (final channel ~5/8″) and press. Stitch the lower fold 1/4″ from the edge to form the channel, leaving a 1.5″ opening on one side for cord insertion. Sew side seams with a 1/2″ seam allowance; finish raw edges with a serger or a 3.0 mm zigzag. Reinforce the lower corners with a 1″ bar tack or a 2.5″ inside patch if the load will be heavy.
Cord specs and routing: recommended cord diameter 5–6 mm (polyester or cotton). For an adult-size pack use 72″ (183 cm) per cord; for youth use 60″ (150 cm). Thread each cord through the channel from the opening: insert on the right front, exit at the right side bottom (or through a grommet placed 1″ above the bottom seam and 1/2″ in from the side), loop under the bag and re-enter on the opposite side so each cord forms shoulder straps when tightened. Secure ends with a tight knot and hide the knot inside the side seam or inside a small fabric tab.
Grommets and reinforcements: if using metal grommets, choose 1/2″ eyelets; place two per side if preferred, spaced 1″ from the bottom seam. Back each grommet with a 2″ fabric square on the bag interior for load distribution. For high-wear points add a 1/4″ double topstitch around the casing and a 3/8″ bartack at each cord exit.
Finishing checks: press seams open, trim thread tails, and test with a 5–10 lb load after sewing to confirm reinforcement. Machine settings: medium presser-foot pressure, feed dogs engaged, and a test sample stitch at full thickness before final assembly. Typical completion time: 45–60 minutes for an experienced maker; allow extra time for hardware installation.
Choose fabric, cord, and hardware: what to buy per bag
For a standard adult cinch/corded gym sack (approx. 16″ H × 14″ W): buy 0.5 yd (45″ wide) of medium-weight fabric, one 72″ length of 5–6 mm cord, and two 12 mm grommets with washers.
- Fabric options and quantities (single bag):
- Lightweight casual bag: 0.5 yd of quilting cotton or 200–210D ripstop nylon (80–120 g/m²). Use a woven lining scrap 0.5 yd if you want a neat interior.
- Everyday/urban bag: 0.5–0.6 yd of 10–12 oz cotton duck (340–405 g/m²) or 200–300D polyester. No lining required but add 0.25 yd of stiff fusible interfacing for the front pocket.
- Heavy-duty bag: 0.6–0.75 yd of Cordura 600D (or similar 400–600 g/m² synthetic). Add 0.25 yd of medium-weight interfacing for the top casing for extra abrasion resistance.
- Kids size (12″ H × 10″ W): 0.4 yd of light cotton or 70–100D ripstop.
- Cord and rope (per bag):
- Thin decorative cord: 3 mm braided polyester, buy 60″ (150 cm) for kids, 72″ (180 cm) for small adult bags.
- Standard functional cord: 5–6 mm braided nylon/polyester, buy 72″ (180 cm) per strap set (two straps made from one length looped). For taller bags (18″+) increase to 84″ (213 cm).
- High-strength option: paracord 550 (approx. 4 mm diameter) – 72″ for adult size; breaking strength ~550 lb (250 kg) – useful when load and durability matter.
- Cord finish: add two 10–12 mm plastic or metal cord ends/crimps and one or two cord locks (spring toggle) if you prefer adjustable closures.
- Grommets/eyelets and hardware (per bag):
- Grommet diameters: select inner diameter (ID) based on cord thickness – 8–10 mm ID for 3–4 mm cord, 12–14 mm ID for 5–6 mm cord. Buy a pair (2) per bag.
- Material: brass-plated or nickel-plated steel for longevity; stainless steel if bag will get wet frequently.
- Reinforcement washers: included with many grommet kits; if not, buy 2 matching washers per bag.
- Optional: 1 small D‑ring or swivel hook (10–15 mm) if you plan a removable strap conversion – buy 1 per bag plus a short webbing strap (12–18″ / 30–45 cm) if needed.
- For internal pockets: 4–6 small snap fasteners (10–12 mm) or a 6–9″ zipper for a secure compartment.
- Interfacing, thread, and notions:
- Thread: polyester 40–50 wt matching color; one spool per bag (100–200 m).
- Interfacing: fusible medium-weight (PES batting alternative: 80–120 g/m²) – 0.25 yd for casing and pocket reinforcement.
- Topstitching: optional heavier nylon or polyester thread (30 wt) for strap anchors and stress points.
- Small tools: 6–8 mm hole punch or awl for grommet holes, grommet setter or hand press (many kits include anvil and setter).
- Quick buying checklist per box (one bag):
- Fabric 0.5 yd (specify type: quilting cotton / 10–12 oz cotton duck / Cordura 600D).
- Cord: one 72″ length of 5–6 mm braided polyester or paracord 550 (72″).
- Grommet kit: 2 grommets (12 mm ID recommended for 5 mm cord) + washers.
- Cord ends (2) and cord lock (1) if using adjustable closure.
- Thread spool (polyester 40–50 wt) and 0.25 yd fusible interfacing.
Length formula for a single continuous cord option: total cord length ≈ 2 × bag height + 2 × strap drop + 12″ (30 cm) for knotting/clearance. Example: 16″ H bag with 20″ strap drop → 2×16 + 2×20 + 12 = 100″ (buy two 50″ lengths or one 100″ length).
Cut and prepare pattern pieces: size, add seam allowance, and mark notches
Cut main body pieces to finished dimensions plus seam allowance: for a standard adult cinch sack use finished 14″ wide × 16″ high – cut two rectangles 14″×16″ then add seam allowance on all sides as specified below.
Standard sizes and cutting chart
| Finished (W × H) | Main fabric (cut) | Lining (cut) | Pocket (optional) | Casing extra above top edge | Recommended seam allowance |
|---|---|---|---|---|---|
| 12″ × 14″ (30×36 cm) – child | 12″×14″ + SA = cut 2 at 13″×15″ (33×38 cm) for 1/2″ SA | same as main | 8″×6″ + 1/2″ SA | 1¼” (3.0 cm) | 1/2″ (12 mm) / 13 mm |
| 14″ × 16″ (36×41 cm) – standard | 14″×16″ + SA = cut 2 at 15″×17″ for 1/2″ SA | same as main | 9″×7″ + 5/8″ SA | 1¼” (3.0 cm) | 1/2″ (12 mm) or 5/8″ (15 mm) for medium weight |
| 16″ × 18″ (41×46 cm) – large | 16″×18″ + SA = cut 2 at 17.5″×19.5″ for 3/4″ SA | same as main | 10″×8″ + 3/4″ SA | 1½” (3.8 cm) | 5/8″ (15 mm) / 3/4″ (20 mm) for heavy fabric |
Use the table to pick finished size, then add uniform seam allowance to every edge of each pattern piece. For casing allowance above the top edge add the listed casing extra; this gives enough fabric to fold twice and create a tidy cord channel that accommodates common cords and toggles.
Cutting technique, grainline and notch placement
Place pattern on fabric with the grainline arrow parallel to the selvedge. For one-piece construction fold placement: if cutting on fold mark “fold” on paper and cut a single mirrored piece. Use pattern weights and a rotary cutter for straight edges; cut through one or two layers only unless you have a sharp blade and precise alignment.
Recommended pattern pieces to transfer to fabric: main body ×2, lining ×2, pocket ×1 or ×2 (if double), cord casing if drafted separately, and strap pieces (if not using cord only). Mark the following notches and transfer points:
– Center top: mark a single short vertical notch (1–2 mm clip into seam allowance) on both main pieces to align casing and cord exits.
– Side seams: mark quarter points or side seam notches to align pocket or reinforcements.
– Pocket placement: mark the pocket top edge position measured from top edge (standard pocket top sits 5–6″ / 12–15 cm below finished top).
– Cord channel ends: mark both ends of the casing with small triangle marks on the seam allowance so you can fold and stitch accurately.
– Strap/eyelet positions: mark with a dot or tailor’s tack; record distance from top edge in mm for precision (e.g., 1″ / 25 mm from side seam).
Transfer marks using tailor’s chalk for washable fabrics, a tracing wheel with dressmaker’s carbon for precision, or tailor’s tacks for delicate or slippery materials. For notches on bulky fabrics make small clipped V-notches into the seam allowance only; do not clip into the stitching line.
Seam allowance selection quick guide: choose 1/2″ (12 mm) for lightweight cotton and quilting-weight, 5/8″ (15 mm) for mid-weight canvas or duck cloth, 3/4″ (20 mm) for heavy canvas or when finishing with boxed seams. If planning French seams, add 1/4″ extra to the pattern so inside finishes reduce width after the second seam.
When adding hem for a cord channel: add the casing extra listed in the table, then fold as follows – first fold 1/4″ (6 mm) to the wrong side and press, then fold a second 1″ (25 mm) (or the total casing width minus first fold) to encase and stitch. Test with your cord: a 6–8 mm cord needs a finished channel of around 10–12 mm for free movement; increase channel width by 2–3 mm if using toggles.
For accuracy label each paper pattern piece with piece name, cut count, grainline, seam allowance size, and notch symbols before cutting fabric. If adjustments are needed after a mock assembly, tape paper pattern and re-cut instead of altering fabric wastefully.
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Stitch side seams and reinforce bottom corners for long-lasting strength
Use a 1/2″ (12 mm) seam allowance on side seams, machine-stitch twice (primary row at 1/2″, secondary topstitch at 1/8″) with bonded polyester thread and a 90/14 or 100/16 needle for heavyweight fabrics.
Tools & materials
- Thread: bonded polyester, 40–50 wt (stronger than cotton)
- Needles: 90/14 for medium-weight canvas; 100/16 or denim needle for heavy duck/cordura
- Stitch length: 3.0–3.5 mm for straight seams; 2.0–2.5 mm for bartacks
- Edge finish: serger or narrow zigzag
- Reinforcement: 3″–4″ square patch of extra fabric or 6 oz fusible interfacing per corner
- Optional hardware: 6–8 mm solid rivets with washers for corner reinforcement
- Marking: chalk or removable fabric pen; ruler
Step-by-step
- Align pieces with right sides together and match notches. Pin or clip every 3–4″ to keep edges even.
- Stitch the side seams in one continuous pass from top to bottom at 1/2″ (12 mm). Backstitch 6–8 mm at start and stop. Use 3.0–3.5 mm stitch length.
- Finish raw edges with a serger or 3 mm zigzag, trimming excess to 1/4″ to reduce bulk.
- Topstitch the seam 1/8″ (3 mm) from the edge on the exterior to flatten the seam and add abrasion resistance.
- Make boxed corners: either cut a 2″×2″ square from the corner (for a finished 1″ depth) or pinch the corner so seams nest; align seam lines perpendicular and measure 1″ from the point, then stitch across that line.
- Trim the corner tip to 1/4″ beyond the seam and finish the raw edge with a narrow zigzag or serge. Press seams toward the outer panels.
- Reinforce each boxed corner with a 3″ fabric patch sewn to the inside: place patch over the corner on the wrong side and sew a 1/8″ seam around or bartack across the stress point (3–4 mm wide, 2–3 mm stitch length, repeat 2–3 times).
- Optional: set a 6–8 mm rivet through the patch and both layers at the most loaded corner point; use a washer on the inside to distribute load.
- For high-abuse designs, add a 1″ wide strip of 6 oz fusible interfacing along the interior side seams before stitching to spread stress over a larger area.
Quick tips: use a longer stitch length only on the primary seam; reduce to 2.0–2.5 mm for bartacks. Match thread color to hide wear marks. Test on a fabric scrap with your chosen needle and stitch settings before working on the final piece.
Create a tidy cord casing: folded vs. double-layer methods
Quick recommendation: use a folded casing for lightweight cotton and thin cord (≤4 mm) for speed and low bulk; choose a double-layer channel for canvas, heavy-weight fabric or cords >4 mm for a cleaner interior and greater durability.
Use this sizing rule: finished channel width = cord diameter × 2. Examples: 3 mm cord → 6 mm finished; 5 mm cord → 10 mm finished. For stitch planning, use 2.5 mm stitch length and backstitch 3–4 mm at reinforcement points.
Folded casing – measurements and technique: press raw top edge under 3 mm, then fold down a second time equal to the finished channel width + 3–4 mm ease (this hides the raw edge and gives cord clearance). Example: for a 5 mm cord, fold down 10 mm + 4 mm = 14 mm, then topstitch 3 mm from the inner fold to form the channel. Stabilize lightweight fabrics with a 25 mm strip of lightweight fusible interfacing across the top before folding; skip interfacing for heavy canvas.
Openings and reinforcement for folded method: leave a gap in the topstitching of 25–30 mm at each side to feed the cord, or make two horizontal slits of 10–12 mm through the casing layers only. Strengthen each exit with a narrow bartack or 6–8 rows of short backstitches (~3–4 mm long). Place openings 10–15 mm from the side seam for neat corner clearance.
Double-layer channel – measurements and technique: cut a strip whose width = (finished channel × 2) + 12 mm allowance for seams and turnings. Example: desired finished channel 10 mm → strip width 10×2 + 12 = 32 mm. With right sides together, stitch the strip to the bag top edge using a 6 mm seam allowance, press the strip up over the seam, fold the raw top edge under 3 mm, then topstitch close to the fold to create the channel. This method hides raw edges completely and keeps the interior smooth.
Details that improve both methods: trim seam allowance at corners to 6 mm to reduce bulk, press seams flat with a dry iron, and use polyester or bonded thread for added abrasion resistance. If cord is slippery (nylon/polypropylene), increase finished channel width by 10–15% to prevent binding. For visible topstitching, use a thread weight one size heavier than body seams and stitch 3–4 mm from the folded edge for a crisp finish.
Thread and secure cords: techniques to prevent twisting and slippage
Use two equal-length cords routed in opposite directions; calculate each cord length as: bag height × 2.5 + 20–30 cm for knots and allowances. Examples: 30 cm height → 100 cm cord, 40 cm → 125 cm, 50 cm → 150 cm.
Channel sizing and cord selection
Match cord diameter to tunnel width: allow 3–4 mm clearance around the cord. Recommended tunnel widths: 4–6 mm cord → 12–15 mm tunnel, 8 mm cord → 16–20 mm tunnel, flat ribbon → 20–25 mm. Preferred materials: braided nylon/paracord (4 mm) for heavy use, twisted polyester cord (3–5 mm) for light/medium loads, cotton cord for low-friction surface finishes. For synthetic cords, fuse cut ends with a lighter or use heat-shrink tubing (6–10 mm length) to stop fraying.
Threading layouts and anti-twist details
Use a two-loop routing: feed cord A from right lower anchor up through the side, along the top tunnel to the left, down to the lower left anchor; feed cord B mirrored (left up, across top to right, down). This balances torque and prevents a single cord from rotating the load. For a single-cord loop, run the cord through both tunnels twice (right→left→right) so each shoulder receives a counterbalancing strand.
Install an internal center stitch or sewn divider inside the top tunnel to create two separate channels; stitch length 6–8 mm, 5–7 dense passes for a bar-tack style anchor where cords enter the side seam. Use bonded nylon or heavy polyester topstitch thread for reinforcement (label 30–40 wt or Tex 35–70).
Use hardware sized to cord: grommet hole diameter = cord diameter + 2–3 mm (e.g., 4 mm cord → 6–7 mm grommet). Place grommets at lower corners or route cords through boxed corners for external anchoring; reinforce with a 12–15 mm bar tack or a stitched box + X pattern (6–8 mm stitch length, high-density stitching). For removable adjustment, fit a spring cord lock sized to the cord (common hole sizes: 3–4 mm, 4–6 mm). Test the lock: it must slide under load and hold at a 25–35 kg pull for everyday use.
Finish cord ends with metal crimps or heat-shrink: use 2-part cord ends crimped with pliers and a dab of clear fabric glue inside the tube, or melt synthetic ends and press flat. For join knots use a double fisherman’s knot for permanent joins and a double overhand or figure-eight stopper as end stoppers; dress knots tightly and trim excess to 5–8 mm from the knot.
If twisting persists, add one small interior stitch through both cord layers at the base of the tunnel (single pass, heavy thread) to lock strand orientation without restricting movement; replace slick cords with textured braided cords for more friction inside the tunnel.
