NATARAJACargo work — the numbers of the hold
Learning outcomes & permitted supports
- Turn stowage factor and broken stowage into space and weight both ways — and know which limit (deadweight or cubic) bites for a given cargo
- Check a tank-top load density and cap the stack height (t/m² × m³/t = m)
- Resolve a union purchase and state, with numbers, why the 120° included-angle rule exists
- Estimate effort on a tackle with the working friction allowance
- Compute cargo loaded from drafts and TPC — the simple draft survey
Supports in this lab: Calculator. Stowage factors shown are classroom planning figures; the shipper's declaration governs aboard. Engine golden-validated 698/698.
Stowage factor — the space a tonne demands
Coal (bulk) stows at about 1.3 m³/t (planning figure — the shipper's declared SF governs on the day). 5000 t with 8% broken stowage needs 7065.2 m³; a 9000 m³ hold takes 6369.2 t of it. Notice the two regimes: iron ore fills your DEADWEIGHT long before your cubic; timber fills your CUBIC long before your deadweight.
| Space for the parcel | 7065.2 m³ |
|---|---|
| Weight the hold takes | 6369.2 t |
Load density — how high may the stack go?
Tank-top limit 12 t/m² × SF 1.3 m³/t = max stack 15.60 m(t/m² × m³/t = m — the neat cancellation). Stack higher and the steel under the pile, not the ship's stability, is what fails first.
| Max stack height | 15.60 m |
|---|---|
| Loading if stacked 6 m | 4.62 t/m² |
Union purchase — why the flat span is the killer
Two runners share a 2 t load, 25° and 35° from the vertical. Tensions: 1.32 t and 0.98 t — included angle 60°. Keep the included angle under ~120° and the runners stay honest.
| T₁ / T₂ | 1.32 / 0.98 t |
|---|---|
| Included angle | 60° |
| 3-sheave tackle effort for 2 t (10%/sheave) | 0.87 t |
Draft survey — the cargo the water admits to
Mean draft 6.40 m before, 7.10 m after, TPC 30: sinkage 70 cm × TPC = 2100.0 t loaded. (The full survey corrects for trim, hog/sag, density and deductibles — that machinery arrives with the Phase-2 stability paper II.)
| Cargo by drafts | 2100.0 t |
|---|
The cargo paper — what is built, what is coming
Mapped against the IMU Sem-III cargo handling & stowage topics: SF · broken stowage — builtload density — builtgear statics · SWL — builtdraft survey (simple) — builtventilation & sweat — nextsegregation & securing — nexthatch covers — nextstowage plan — nexttankers & specialised (Sem V) — later