TPC, TPI & MCTC Tool Draft Change, Waterplane Area & Trim Moment

TPC • TPI • MCTC • Waterplane Area • Parallel Sinkage • Trimming Moment • LCF • LCG • Weight Add / Remove / Shift • Final Drafts

TPC, TPI & MCTC Tool Draft Change, Waterplane Area & Trim Moment

Calculate tonnes per centimetre immersion, tons per inch immersion, moment to change trim one centimetre and the resulting forward/aft draft changes from loading, discharge or longitudinal weight movement. Simple mode solves one weight event from hydrostatic geometry. Advanced cross-checks hydrostatic-table values, builds waterplane area from Cwp when required, tracks multiple add/remove/shift events, updates displacement and LCG, models water-density transition, screens final drafts and solves the weight-shift distance needed to reach a target trim.

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Need hydrostatic-table cross-checks, multiple weights, LCG tracking or density transition? Click Advanced above.Simple treats TPC and MCTC as local hydrostatic coefficients and solves one loading/discharge event about the LCF.

HydrostaticsTPC + TPI + MCTC

LoadingParallel sinkage + trim

Draft resultFinal forward & aft drafts

Single Weight Change

Waterplane aream² at the current waterline.

Water densityt/m³.

Displacementmetric tonnes.

Length between perpendicularsm.

Longitudinal GM (GML)m.

Weight changet; positive = load, negative = discharge.

Weight longitudinal positionm forward from AP. AP = 0, FP = LBP.

LCF positionm forward from AP.

Initial aft draftm at AP.

Initial forward draftm at FP.

Hydrostatic Condition & Cross-Check

Waterplane-area source

Direct waterplane aream².

Current water densityt/m³.

Waterline lengthm, used for Cwp area source.

Waterline breadthm.

Waterplane coefficient CwpAwp/(LWL×BWL).

Displacementt.

LBPm.

GML source

Direct GMLm.

KMLm.

KGm.

TPC planning source

Entered hydrostatic TPCt/cm.

MCTC planning source

Entered hydrostatic MCTCt·m/cm.

Hydrostatic review threshold% difference for derived-vs-entered review flag.

Draft, LCF / LCG & Density Transition

LCF from APm; AP = 0, FP = LBP.

Initial LCG from APm.

Initial aft draftm at AP.

Initial forward draftm at FP.

Final / destination water densityt/m³. Set equal to current density to disable density transition.

Maximum allowed end draftm, screens the larger of final AP/FP drafts.

Weight Add / Remove / Shift Register

All longitudinal positions are metres forward from AP. Add uses the “To / position” field. Remove uses “From / position”. Shift uses both. Positive trim moment in this tool means bow-down, so the forward draft increases relative to the aft draft.

Event	Weight t	From position m	To / position m

Target Trim Shift Planner

Target final Fwd − Aft draft differencem; positive = bow deeper, negative = stern deeper.

Available shift weightt available for longitudinal relocation after the entered events.

Hydrostatic / Loading Checks

Hydrostatics match current draft/trimTPC, MCTC, LCF and displacement are from the applicable condition. Weight quantities verifiedLoaded, discharged and shifted weights use the same mass basis. Longitudinal positions verifiedAP reference and cargo/tank centres are correctly entered. LCF sign / reference verifiedLCF is entered forward from AP, not “aft of midships” notation. Density sample / transition verifiedCurrent and final water densities apply to the intended stages. Large-change hydrostatics reviewedUpdated/interpolated TPC and MCTC are used when draft changes materially. Strength and stability checked separatelyDraft/trim geometry does not replace loading-computer strength/stability checks. Draft limit / marks checkedFinal AP/FP drafts are checked against actual operational restrictions.

Hydrostatic limitation: TPC and MCTC vary with draft and hull form. These calculations use local/constant hydrostatic coefficients and small-angle trim geometry. For large loading/discharge changes, strong trim changes or significant density transitions, use the ship’s approved hydrostatic/stability data or loading computer at the updated condition and iterate as required. This tool does not replace longitudinal-strength, stability, load-line, draft-survey or loading-computer checks.

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