Marine Calculations

How to Calculate Hull Layup, Resin Infusion, and Takt Time for Boat Manufacturing

Step-by-step formulas for the four calculations that govern composite boat production: layup labor, resin mass, coating coverage, and takt time.

Composite boat production lives or dies on four calculations: hull layup labor hours, resin infusion mass, coating coverage, and takt time. Start with layup labor. Hand layup on a production hull runs roughly 0.6 to 1.2 labor hours per square meter of laminate, depending on curvature and core detail. For a 12 meter hull with 95 square meters of laminate surface at 0.85 hr/m2, base labor is 95 times 0.85, or 80.75 hours. Add 15 percent for gelcoat prep and demold and you land near 93 hours. The Hull Layup Labor Hours calculator applies these rates per zone so keel, topsides, and deck get separate multipliers.

Resin infusion mass follows from laminate weight and resin-to-glass ratio. Vacuum infusion typically hits a 1.0 to 1.2 resin-to-glass ratio by weight, versus 2.0 to 2.5 for sloppy hand layup. If your reinforcement schedule totals 1,450 grams per square meter of glass across 95 square meters, dry glass mass is 137.75 kg. At a 1.1 infusion ratio, resin mass is 137.75 times 1.1, or 151.5 kg. Add 12 to 18 percent for feed lines, flow media, and the resin trap that never reaches the part. The Resin Infusion Material Estimate calculator turns that into kits so you order 175 kg, not 151.5 kg.

Coating coverage converts theoretical spread rate into real gallons or liters. Theoretical coverage equals 1,604 times volume solids divided by wet film thickness in microns, giving square meters per liter. A two-part polyurethane at 55 percent solids sprayed at 50 microns wet yields 1,604 times 0.55 divided by 50, or 17.6 m2 per liter theoretical. Apply a transfer efficiency of 65 percent for conventional spray and you get 11.4 m2 per liter practical. For 140 m2 of topsides and deck, that is 140 divided by 11.4, or 12.3 liters. The Marine Coating Coverage calculator handles primer, high-build, and topcoat layers separately.

Vessel takt time sets the production heartbeat. Takt equals available production time divided by required output over the same window. A yard running one shift of 7.5 productive hours over 21 working days per month has 157.5 hours available. To deliver 6 boats a month, takt is 157.5 divided by 6, or 26.25 hours per boat. Every station must complete its work inside that window or the line stalls. The Vessel Production Takt Time calculator lets you test how a second shift, from 157.5 to 315 hours, drops takt to 13.1 hours and doubles throughput without new molds.

Cure schedule time is easy to underestimate because it stacks in series, not parallel. A vinylester infusion needs roughly 4 to 6 hours to gel at 24 C, then 8 to 16 hours to reach demold hardness, then an optional post-cure of 4 hours at 60 C to hit full glass transition temperature. Total tool occupancy can be 20 hours even though hands-on labor was 12. If your takt is 26.25 hours and cure eats 20 of it in a single mold, you need a second mold to keep pace. The Composite Cure Schedule Time calculator models ramp, dwell, and cooldown against ambient shop temperature.

Marine wiring harness length drives both material and labor on the outfitting side. Estimate run length as straight-line distance times a routing factor of 1.35 to 1.6 to account for bends, service loops, and clamp spacing at 300 mm intervals. A helm-to-engine run measuring 9 meters straight becomes 9 times 1.45, or 13.05 meters per conductor. Multiply by the conductor count in the bundle, say 14 wires, for 182.7 meters of wire in that harness alone. The Marine Wiring Harness Length calculator sums every run so you buy spools and budget termination time, roughly 2.5 minutes per crimped and labeled end.

Tie the numbers together before you trust them. Cross-check laminate mass against the design displacement: hull and deck laminate usually run 18 to 30 percent of light ship weight on a planing powerboat. If your 6,800 kg boat shows only 900 kg of structure, your glass schedule is probably light or your area estimate missed the stringers. Likewise, confirm resin mass against total infusion kit yield and confirm coating liters against measured wetted area, not the brochure length overall. A single unit slip, grams versus kilograms or microns versus mils, throws every downstream order off by orders of magnitude.

Keep every input traceable to a source document. Laminate area comes from the mold surface takeoff, not the boat's overall dimensions. Glass weight per square meter comes from the ply schedule in the structural drawing. Solids content and wet film thickness come from the coating technical data sheet, never memory. Available hours come from the shift calendar minus planned maintenance and training. When you record where each number originated, a wrong quote becomes a five minute audit instead of a rebuild. Run the Vessel Launch Readiness Score at the end to confirm all these calculated milestones actually closed before splash.

Published 2026-07-01.