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Marine Deck Machinery Sizing Calculator

Free engineering tool for anchor windlass & mooring winch specification

Based on IACS UR A3 & Classification Society Standards

Anchor Windlass Sizing

Calculate continuous duty pull, brake capacity, and motor power per IACS UR A3.

Chain Diameter (mm)

Chain Grade

Hoisting Speed (m/min)

Efficiency η (0–1)

Chain Stopper Fitted

Continuous Duty Pull (Breaking test load per IACS UR A3):

Z = K × d_c²
K = 37.5 (U1) | 42.5 (U2) | 47.5 (U3)
Result Z in N; divide by 1000 for kN

Overload Pull:

Overload = 1.5 × Continuous Duty Pull

Brake Holding Capacity:

T_brake = K_b × d_c² × (44 − 0.08 × d_c) [N]

K_b values:
U1: 4.41 (with stopper) / 7.85 (without)
U2: 6.18 (with stopper) / 11.0 (without)
U3: 8.83 (with stopper) / 15.7 (without)

Motor Power:

P (kW) = F × V / (1020 × 60 × η)
where F = continuous pull (N), V = speed (m/min)

Chain Wheel Dimensions (5-pocket stud link):

PCD ≈ (6 × d_c × 5) / π
OD ≈ PCD + 2.4 × d_c

Winch Drum Sizing

Calculate drum barrel diameter, width, flange diameter, and layer count for mooring winch drums.

Rope Diameter (mm)

Required Rope Length (m)

Rope Type

Number of Layers (override)

Auto-calculate minimum barrel diameter

Drum Barrel Diameter (mm)

Drum Width (mm, optional override)

⚠

Safety Wraps Reminder: Maintain minimum 3 dead wraps for wire rope or 6 dead wraps for synthetic rope on the drum barrel. These wraps are NOT included in the usable rope length. Top rope layer must be 3–5 × d_r below the flange edge.

Minimum Drum Barrel Diameter:

D_b,min = (D/d ratio) × d_r
6×19: ratio = 25 | 6×37: ratio = 18 | HMPE: ratio = 10

Rope Capacity (rope length on drum):

L = W × (D_f² − D_b²) / (15.3 × d_r²)

Required Drum Width (rearranged):

W = L × 15.3 × d_r² / (D_f² − D_b²)

Flange Diameter:

D_f = D_b + 2 × n_layers × d_r
Plus clearance: top layer ≥ 3 × d_r below flange

Wraps per Layer:

n_wraps ≈ W / d_r

Bow vs. Stern Configuration

Typical deck machinery arrangement comparison.

Bow (Forecastle) Arrangement

Motor /
Gearbox

Chain
Wheel

Main
Drum

Aux
Drum

Bow windlass includes chain wheel(s) for anchor chain handling, plus mooring drum(s). Brake band on chain wheel provides holding force.

Stern (Aft) Arrangement

Motor /
Gearbox

Main
Drum

Aux
Drum

Stern mooring winch typically omits chain wheel. Designed for mooring lines only (wire rope or synthetic). May include warping head.

Deck Machinery Layout Arrangements

Three common arrangement options for vessel deck machinery.

Plan A: Independent

Drum

MW Drum

Aux

Separate anchor windlass and mooring winch. Each unit independently powered. Offers maximum flexibility but requires more deck space.

Most Common

Plan B: Combined

Main

Aux

Windlass-mooring winch combination. Single drive unit handles both anchoring and mooring. Most space-efficient and cost-effective solution.

Plan C: Triple-Drum

Drum 1

Drum 2

Drum 3

Integrated triple-drum configuration for larger vessels. Provides anchor handling plus dual mooring capability on a single shaft line.

Legend: CW = Chain Wheel | MW = Mooring Winch | Aux = Auxiliary Drum (warping/storage)

Watch: Winch drum sizing: prepare the inputs before calculating

Prepare rope length, drum geometry, layers and retained wraps before using the drum-sizing section. Calculator results are preliminary and require design confirmation.

Illustrative procurement and selection guide; not product footage or performance test evidence. Confirm the final specification for your application.

Send rope diameter and length, barrel and flange dimensions, working width and required duty. Request a quotation: sales@hiqool.com

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Our engineers can help you specify the right deck machinery for your vessel — from preliminary sizing to classification-approved drawings.

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