Michael Turner
Materials: Choose 25 mm (1″) webbing for daypacks, 38–50 mm (1.5–2″) for heavy loads. Nylon stretches slightly; polyester holds shape better. For outer shell select 500D–1000D Cordura or 420D nylon for lighter builds. Padding: 6–8 mm foam for short-use carry, 10–12 mm for hiking loads; closed-cell PE or EVA recommended. Thread: bonded polyester or nylon upholstery thread (use size #69 or Tex ~70 for main seams).
Hardware and measurements: Use triglide/adjuster and D-ring sized to webbing (25 mm hardware for 25 mm webbing, 38–50 mm hardware for wider webbing). Sternum slider: 16–25 mm depending on strap width. Leave 50–100 mm of tail beyond adjuster for reworking; fold webbing back 20–30 mm when terminating to avoid fray.
Stitching technique: Set stitch length 3.0–4.0 mm for primary seams; use 10–12 stitches per inch (spi) for reinforcement segments and 2.0–2.5 mm (12–14 spi) density for bartacks if your machine can. Recommended sequence: fold and topstitch two parallel rows 4–6 mm from each edge, then secure termination with a 30×30 mm box and an X inside (or a dense bartack). For end points add at least three parallel lines of stitching if bartack tool unavailable.
Machine setup and consumables: Use a walking foot or compound feed for layered assemblies. Increase presser foot pressure slightly and use heavy-duty needles 100/16–110/18. Adjust thread tension upward in small increments to avoid skipped stitches. Use clips, not thin pins, to hold webbing and foam sandwich in place. When topstitching over metal hardware remove it from the stitching line and tack after assembly.
Reinforcement and testing: Reinforce all attachment points with box-X or bar tacks; for soft-shell joins add a backing patch of 2–3 layers of 500D fabric sized 40×60 mm under the stitching area. Final test: load with 20–30 kg for day-use designs and inspect for pullout or seam elongation; any visible thread breakage requires rework with denser stitching and additional backing.
Quick tip: Heat-seal cut webbing ends, then fold and tack before final topstitching to prevent fray and ensure a clean termination.
Constructing a rucksack shoulder harness: materials, measurements, reinforcement
Use 38–50 mm (1.5–2 in) nylon webbing, 8–12 mm closed-cell foam for padding, and bonded polyester thread; cut each shoulder piece 55–70 cm for adults, 35–45 cm for children.
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Materials and hardware
- Webbing: 38 mm for lightweight daypacks, 50 mm for heavy loads; polyester or nylon with breaking strength ≥ 3,000 N.
- Padding: closed-cell foam 8–12 mm thick, density 40–60 kg/m³; use tapered edges (3–5 mm) for comfort at shoulder seams.
- Thread & needle: bonded polyester Tex 60 / size 90–100 (100/16 universal) or upholstery thread; use heavy-duty bobbin.
- Hardware: tri-glide adjusters matching webbing width, 1–1.5 in side-release buckle for sternum, stainless steel or brass D-rings for load-bearing points.
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Cutting and preparation
- Cut webbing 55–70 cm per shoulder (include 3–4 cm extra for fold-under at ends).
- Cut foam 3–5 mm shorter than webbing width to avoid bulky edges; round foam ends with 10 mm radius to reduce stress points.
- Heat-seal webbing ends for synthetic webbing with short blower burst; allow to cool 5–10 s before handling.
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Assembly and stitch patterns
- Layering order: webbing (outer), foam, lining fabric (nylon taffeta or Cordura). Topstitch 5–6 mm from webbing edge to secure pad.
- Primary reinforcement: box with diagonal cross. Use a 25 mm square for typical webbing; stitch at least 6 mm from webbing edge, repeat stitch at 2–3 passes for heavy loads.
- Secondary reinforcement: straight triple stitched line 10–15 mm inside edge for topstitch stability; bartack across load path at 10–12 mm width with 10–15 stitches per tack.
- Stitch settings: lockstitch machine, stitch length 3.0–3.8 mm for webbing-to-webbing, 2.5–3.0 mm for attachment through multiple layers; increase tension slightly when running foam layer.
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Attachment geometry and dimensions
- Attach shoulder pieces to pack body with 25–30 mm overlap, use box-X pattern and an additional row of straight stitches 10 mm from edge.
- Position tri-glide adjuster 12–18 cm from lower attachment to provide smooth range of motion; keep adjuster parallel to shoulder seam.
- Sternum buckle placement: 12–14 cm below shoulder seam for adults (adjust lower for children). Sternum strap length 25–30 cm with 3–4 cm webbing free for adjustment.
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Finishing and testing
- Trim excess thread, backstitch or lock at all start/end points; finish raw fabric edges with binding tape if exposed.
- Perform static pull test: apply 2–3× expected working load (for a 15–20 kg carry target test to 40–60 kg) and inspect stitch integrity and webbing deformation.
- Field check: load pack, simulate dynamic movement for 10–15 minutes to detect chafing, slider migration, or stitch failure; rework any concentrated wear areas.
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Select shoulder webbing: material, width and length for your bag design
Quick recommendation: For an everyday 15–20 L bag choose 1.5″ (38 mm) nylon flat webbing with 12–18 mm closed-cell foam under a polyester cover; make each adjustable side 40–95 cm (16–37 in) from top attachment to end of adjustment tail.
Material choices and characteristics
Nylon flat webbing – high tensile strength, good abrasion resistance, slightly stretchy when wet; suitable widths: 25 mm, 38 mm, 50 mm. Polyester webbing – lower stretch, better UV resistance, slightly stiffer; good for exposed designs. Cotton or canvas webbing – soft hand, vintage look, significant water absorption and stretch; use for light loads only. Leather – premium appearance, rigid initially, choose 3–4 mm vegetable-tanned for shoulder pieces; reinforce attachment points. Tubular webbing – softer under load, better for padded constructions. Consider urethane-coated or water-repellent finishes for outdoor use.
Width, padding and length guidelines
Width selection by intended load (per carrying side): 25 mm (1″) – light daybags, gym pouches, max recommended load ~8–10 kg; 38 mm (1.5″) – general-purpose urban bags, comfortable up to ~15 kg; 50 mm (2″) – heavy-duty packs, travel or gear-carrying, recommended when loads exceed 15–20 kg. Match hardware inner width to webbing width (e.g., 38 mm webbing → 38 mm tri-glide/buckle).
Padding thickness and type: thin profiles 6–10 mm EVA for compact bags; midweight 12–18 mm closed-cell foam for daily comfort; heavy-duty 20–25 mm high-density foam for long treks or heavy loads. Add a 1–2 mm anti-slip rubber or silicone layer on the underside when the bag will ride on clothing during movement.
Length rules of thumb: adult adjustable range per side 40–95 cm (16–37 in); children 30–65 cm (12–26 in); single-shoulder sling designs 90–120 cm (35–47 in) total. When creating non-adjustable fixed-length pieces, cut finished lengths 5–8 cm longer than body-measure recommended to allow for folded/stitched ends and hardware routing.
Attachment and hardware notes: Use metal buckles for repeated heavy loading; choose polymer buckles rated for dynamic use only on light loads. Reinforce webbing terminations with a minimum 25 mm box stitch plus bar tacks or rivets on leather; for high-load points, mirror the webbing width with a backing patch of equal-strength fabric to distribute forces.
Cut and layer webbing, foam and lining to exact shoulder-pad dimensions
Cut every webbing, foam and lining piece 10–15 mm longer than the final length to allow a 5–7.5 mm fold/overlap at each end for anchoring into hardware or boxed ends.
For width, use this rule: finished width = FW. Cut outer webbing or cover to FW (±1 mm); cut foam to FW − 6 mm (leave ~3 mm clearance each side so the foam does not create edge bulk); cut lining to match the foam or add +1–2 mm for ease. Examples: for FW = 25 mm → foam 19 mm, lining 20–21 mm; FW = 38 mm → foam 32 mm, lining 33–34 mm; FW = 50 mm → foam 44 mm, lining 45–46 mm.
Taper foam ends over a 20–30 mm length using a rounded template so the transition under the hardware is smooth; reduce foam thickness gradually to zero at the very tip. Trim webbing ends square or with a slight angle (5–10°) depending on the attachment method.
Layer order for flat, padded assemblies: base webbing (load-bearing), then foam centered, then lining facing contact side. If using a cover that wraps, cut cover to FW + 6 mm so it can be folded under 3 mm at each edge and stitched or top-stitched without exposing foam.
Bond layers with a light, even coat of spray adhesive (3M 77 or equivalent) or thin double-sided tape; press under a flat board and 1–2 kg of weight for 10–15 minutes. For spot-basting before stitching, use a few evenly spaced clips or clamps to prevent shifting.
Mark stitch lines: run a consistent centerline stitch or two parallel topstitches. Typical placement is 4–6 mm from each outer edge for a single topstitch per side; for heavy-duty assemblies, add a central reinforcement stitch 10–12 mm from each edge. Use a backstitch or triple stitch at anchor points and leave 10–15 mm of webbing/foam inside the hardware block for secure attachment.
Cut multiples with a template and rotary cutter or sharp shears; stack no more than three foam layers for clean rotary cuts. Maintain tolerances of ±1 mm on widths and ±2 mm on lengths. Final check: assemble one sample, attach to hardware, and verify there is no edge bulge and that the tapered ends sit flush before committing the full batch.
Finish webbing ends and secure adjusters, D‑rings and swivel clips
Trim tails so the folded end extends 1–1.5× the hardware slot length; melt the cut edge with a hot knife and press flat with pliers before stitching.
Fold, stitch and reinforcement dimensions
For 25 mm (1″) webbing fold back 25–30 mm; for 38 mm (1.5″) fold back 30–40 mm. Use a box‑and‑X pattern sized to the folded area: for 25 mm webbing use a rectangle ≈ 20 × 18 mm with an X; for 38 mm use ≈ 30 × 25 mm. Machine stitch length 2.5–3.5 mm. Thread: bonded polyester or nylon, Tex 70 (approx. 0.4–0.5 mm); needle: household heavy‑duty 100/16–110/18, industrial straight‑stitch machines as specified by manufacturer.
For extra load points add a bar tack: 6–8 mm wide zigzag, repeated 10–15 passes across the fold or a commercial bar‑tack unit set to 12–18 mm length.
Hardware selection and attachment order
Match slot width to webbing width ±2 mm (25 mm webbing → 25 mm hardware slot; 38 mm → 38 mm slot). D‑ring thickness: use 3–4 mm steel for light duty, 4–6 mm for heavy carry. Swivel clips: inner gate opening must equal or exceed webbing thickness; choose plated steel or brass for corrosion resistance.
Typical attachment sequences: adjustable loop with tri‑glide–feed tail through adjuster, through the anchored point, back through adjuster and lock with a box‑X. Removable clip loop–thread tail through clip bar, fold back 25–30 mm, stitch box‑X then add a 6–7 mm (1/4″) double‑cap rivet 6–8 mm from the folded edge. D‑ring on a fixed loop–form loop around D‑ring, stitch box‑X and add a washered rivet if greater shear strength required.
Place metal fasteners centered across the webbing width and at least 6–8 mm from any cut edge. When using rivets, add an internal backing plate or washer for woven webbing to prevent pull‑through; choose rivet length to compress all layers without bottoming out.
After finalizing attachments, test with progressive loads: apply 25%, 50%, then 100% of expected working load for 30 seconds each, inspect stitches and hardware for slippage or deformation, then perform a 2× proof load test before regular use.
Create a padded harness channel and topstitch for shape and durability
Use 6–8 mm closed-cell foam trimmed 4–6 mm narrower than the finished channel; center the foam over the webbing and secure with a spray adhesive or narrow fusible tape so it cannot shift during stitching.
Assemble layers in this order: outer shell (right side up), foam+webbing (centered), lining (right side down). Fold edges with a 6–8 mm seam allowance around the foam so the channel is a neat tube; press with a hot iron (fabric-appropriate temperature) and clip every 30–40 mm. Avoid pinning through webbing to prevent distortion.
Run a locking stitch down the channel center to trap the foam if mobility is a problem: use a straight stitch 3.0–3.5 mm length with a 100/16 needle on heavy fabrics or 90/14 for lighter. Use bonded polyester or nylon thread and a walking foot to maintain even feed when stitching over foam and webbing.
Place topstitch rows according to channel width:
- Channels ≤30 mm: three rows – 3 mm from each folded edge + one centered.
- Channels 31–45 mm: four rows – 3 mm from each edge + two inner rows evenly spaced.
- Channels >45 mm: five rows – 3 mm from edges + three inner rows spaced 10–12 mm apart.
Set topstitch length to 3.5–4.0 mm for visible reinforcement; double-pass the outermost edge row for abrasion resistance.
Finish ends with reinforcement: fold webbing back 35–45 mm and stitch a box-with-X or a dense bartack. For machine bartacks, set width 5–7 mm and length 0.4–0.6 mm at high density; for sewn box reinforcements use five parallel rows spaced 6 mm apart for heavy load points.
| Component | Foam thickness | Needle | Thread | Suggested stitch length |
|---|---|---|---|---|
| Nylon webbing + canvas outer | 6–8 mm | 100/16 | Bonded nylon/polyester | 3.0–3.8 mm |
| Ripstop or lightweight shell | 3–5 mm | 90/14 | Polyester | 3.0–3.5 mm |
| Heavy cordura or leather-faced | 8–10 mm | 100/16 or leather needle | Bonded nylon | 3.5–4.0 mm |
Use a walking or roller foot, increase presser-foot pressure slightly for uneven layers, and test one full channel on scrap to confirm feed, stitch tension and bar-tack density before processing final pieces.
Reinforce attachment points with bartacks and backing
Recommendation: place a rigid backing patch under each fastening point and apply dense bartacks through the backing and webbing–use a 40–45 mm overlap of webbing into the bag body and a backing patch sized ~50×30 mm for 25–38 mm webbing.
Backing choices: 1.8–2.5 mm vegetable-tanned leather for heavy duty builds; 500–1000 denier Cordura laminated to a 1.2–1.6 mm leather or 0.8–1.2 mm polyester stiffener for lightweight designs; stainless-steel or nylon washer plates when hardware concentrates load. Round backing corners with a 3–4 mm radius to avoid stress risers.
Thread and needle: use bonded polyester or nylon thread (Tex 70–100 or 30–40 wt range). Home machines: use a jeans/denim needle 100/16; for leather or very thick stacks use 110/18. Industrial bartack machines: program 12–16 stitches per cm density.
Bartack settings and layout: for a domestic zigzag imitation, set zigzag width 5–7 mm and stitch length 0.4–0.8 mm; make 3–5 overlapping passes to create a dense bar 18–25 mm long for 25 mm webbing, 30–35 mm for 38–50 mm webbing. Preferred geometry: two parallel bartacks spaced 10–12 mm apart at the primary load line plus a box-and-cross reinforcement (outer box 30–40 mm × 12–18 mm with an X). Place the densest stitching 6–8 mm from the hardware edge.
Assembly technique: tack the backing in place with 505 adhesive spray or contact cement and clamp; pre-mark stitch lines and use a leather punch for rivet holes if adding metal fasteners. For synthetic webbing, seal cut ends with a hot knife or lighter and press immediately to avoid fraying. When using D-rings or tri-glides, position the backing behind the hardware plate and bartack through all layers; add a 5–6 mm stainless rivet where repeated dynamic loads are expected.
Quality check and load targets: perform a static pull test aiming for ≥900 N (≈200 lbf) without stitch failure or slippage; inspect thread for abrasion and replace bartacks showing >2 mm stitch opening. Re-bartack with one additional pass if any stitch density appears loose after testing.
Tip: keep a record of stitch settings, thread type and needle size per material combination for consistent results across units. For unrelated workshop tool recommendations consult best cutting electric lawn mower.
Fit carrying supports to body shape and fine-tune length, angle and padding placement
Set shoulder length so the top of the padded section sits 2–3 cm (0.8–1.2 in) below the C7 vertebra with the load on; target an adjustable range of roughly 40–90 cm (16–36 in) total webbing travel for adult sizes and a padded panel length of 30–45 cm (12–18 in).
Place top anchor points laterally according to shoulder width: narrow shoulders 4–6 cm (1.5–2.5 in) from the spine, medium 6–9 cm (2.5–3.5 in), broad 9–12 cm (3.5–4.7 in). Set the carrier angle outward from vertical about 8–15° for narrow builds and 15–25° for broad builds; move anchors in 5–10 mm steps to alter contact pattern without changing length.
Position padding so its centre contacts the trapezius and upper deltoid but not the neck root; front edge should be tapered 10–20 mm to avoid pressure at the clavicle. Padding length should extend down the shoulder 120–170 mm (4.7–6.7 in) to spread load. For urban/day use select foam thickness 8–12 mm; for loaded touring or heavy gear use layered construction (firm 8–10 mm base + softer 6–10 mm top) totalling 15–25 mm where pressure relief is needed.
Place sternum/bridging strap roughly 8–12 cm (3–4.7 in) below the base of the neck; anchor spacing across the chest 12–20 cm (5–8 in) depending on chest width. Allow vertical adjustment of ±30–40 mm so the strap clears breathing and chest movement.
Test fit with incremental loads: add weight in 2–5 kg (5–11 lb) steps, walk for 5–10 minutes, simulate climbs and arm swing. Look for three faults: neck pressure (shorten drop or lower padding), slipping off shoulders (narrower contact profile or increased inward angle), or a gap under the armpit >25 mm (widen angle or lengthen padded contact). Aim for a 10–20 mm clearance at the neck during movement and 1–2 cm gap at the axilla when static.
Before final stitching, mark final positions with chalk and secure components with safety pins or long basting tacks; test again under load and adjust anchors in 5–10 mm increments. When satisfied, finish permanent stitches and trim excess webbing, leaving at least 30–40 mm of adjustment tail beyond the final hardware for future tweaks.
Adjustments by body type: shorten drop by 3–5 cm for petite torsos and reduce padded panel length by 20–30 mm; for tall torsos increase drop and padding length by the same amounts. For narrow shoulders use narrower webbing (20–25 mm) and add lateral contouring to the pad; for broad shoulders widen the pad by 10–20 mm and increase outward angle to maintain shoulder seating.
