Barge Draft, Displacement, and Deck Load
Displacement at the light and loaded drafts, cargo carried, tons per inch of immersion, freeboard.
Example
You enter
- Barge length (ft) 195
- Beam (ft) 35
- Depth of hull (ft) 12
- Block coefficient Cb 0.95
- Light draft (ft) 1.5
- Loaded draft (ft) 8
- Water density in service (lb/cu ft) 64
- Fresh water density (lb/cu ft) 62.4
You get
- Light displacement 311 tons
- Loaded displacement 1,660 tons
- Cargo carried 1,349 tons
- Tons per inch of immersion 17.29
- Sinkage the cargo produces 78
- Sinkage (ft) 6.5
- Freeboard at the loaded draft 4
- Same load in fresh water 8.21 ft -- 2.5 in deeper with nothing loaded
- Fresh water allowance (in) 2.46154
Checked against published worked examples from: United States Naval Academy, Naval Architecture and Ocean Engineering Department.
Details, formula, and sources
ScopeDisplacement at the light and loaded drafts, cargo carried, tons per inch of immersion, freeboard, and the draft the same load produces in fresh water. The worked deck barge carries 1,349 tons at 17.3 tons/in and floats 2.5 in deeper up a river. Freeboard is reserve buoyancy, not spare capacity.
Formula or tabledisplacement = L x B x draft x Cb x water density / 2,000; TPI = L x B x Cb x density / (12 x 2,000); fresh-water draft = displacement x 2,000 / (L x B x Cb x fresh density).
Source and editionArchimedes, with 64.0 lb/cu ft sea water and 62.4 lb/cu ft fresh. The barge's capacity plan, its load line, and its stability booklet govern.
Free accessPublic hydrostatics; the vessel's own capacity plan is the controlling document.
What governsVessel master governs. Verify against the stability letter and USCG-approved loading manual.
API field namesbarge_length_ft, beam_ft, depth_ft, block_coefficient, light_draft_ft, loaded_draft_ft, water_density_pcf, fresh_water_density_pcf, light_displacement_tons, loaded_displacement_tons, cargo_tons, tons_per_inch, sinkage_in, sinkage_ft, freeboard_ft, fresh_water_draft_ft, fresh_water_allowance_in
- Wall-sided hull the waterplane is taken as L x B x Cb, so tons per inch uses the block coefficient; a raked barge's waterplane coefficient exceeds Cb and its true TPI (A_WP / 420 in long tons) is a little higher. Tons are short tons (long tons x 1.12)USNA EN400, Section 2.10.4
- Tons per inch treated as constant, which holds for a box-shaped hull across its working range and not for a shaped onespec-v1830 idealisation
- Block coefficient entered; a rake-ended deck barge runs about 0.90 to 0.97barge capacity plan