Aframax tanker on time charter

Based on Project Finance-Class 5 Start.xlsm

A 70,000-tonne tanker bought for USD 60m and chartered out by the day. Charter days fall during dry-docks that grow longer with age, charter rates follow the market with a three-month lag, and the owner reports returns in dollars and rupees. Design example: written in the full v0.5 language. The compiler builds the working core today, so this one doesn't compile yet. Source: examples/design/ship/.

Library: A. Featured Models / L. Shipping (6 files)
Timeline: 36 months to delivery, 25-year life; operations monthly, financing quarterly
Ship: 70,000 t; capex USD 60m paid 10% / 10% / 70% / 10% at months 1, 13, 25 and 36
Operations: Charter rate forecast in real USD a day (15,457 in 2023), 3-month lag; daily costs USD 3,289; dry-dock 15, 25 and 35 days at ages 1, 5 and 15
Finance: Up to 90% debt, KIBOR 10% + 1%, 8 years, 1% upfront; WACC 7% (USD) and 14% (PKR)
Rebuild shown: 4 files, 74 lines

Where each sheet goes

Workbook sheets	Rufineer
Input	inputs.rfn and the Charter rates and Dry-dock sheets
Operations - Monthly	operations.rfn on the monthly ruler
Financing - Quarterly	financing.rfn on the quarterly ruler
Rates and Oil, Interpolate	`interpolate` on the charter-rate curve
Debt Sculpting, Taxes and NOL	financing.rfn

Source 4 files shown, 74 lines

model.rfn

model "Aframax Tanker" {
  currency  USD
  currency  PKR
  data      "tanker_inputs.xlsx"
}

timeline {
  start             2023-01-01
  construction      36m                     // build to delivery
  operations        25y
  ruler monthly     month
  ruler quarterly   quarter
}

fx PKR/USD = ppp(178, local: inputs.macro.pkr_cpi, foreign: inputs.macro.usd_cpi)

inputs.rfn

table charter_curve: USD/d          // Year | Time-charter rate, real
table drydock_days: d               // Ship age | Days: 1 → 15, 5 → 25, 15 → 35
table daily_costs: USD/d            // Victualling 242, stores 357, wages 1,664, sundries 218,
                                    // lubes 339, other 256, repairs 212
table macro { rows year; columns usd_cpi: %/y "USD inflation", pkr_cpi: %/y "PKR inflation" }
table drydocks { rows dock; columns start: date "Start", age: y "Ship age" }

inputs "Ship" {
  capacity        = 70_000 t
  capex           = 60_000_000 USD
  spend           = { 1: 10, 13: 10, 25: 70, 36: 10 } %      // by construction month
  life            = 25y
  charter_lag     = 3m
  commission      = 2.5 %
  insurance_bands = { ..10y: 0.2, 10y..15y: 0.3, 15y..: 0.4 } %/y   // of original cost
  tonnage_tax     = 1 USD/t/y
  depreciation    = 4 %/y
}

inputs "Finance" {
  max_gearing   = 90 %
  kibor         = 10 %/y
  spread        = 1 %/y
  tenor         = 8y
  upfront_fee   = 1 %
  wacc_usd      = 7 %/y
  wacc_pkr      = 14 %/y
}

operations.rfn

module ship "Operations" on monthly {
  age: y = operations.year - 1 + operations.period / 12

  /// Dry-docks: longer as the ship ages, and they can run across month ends
  period drydock[k] = inputs.drydocks[k].start for inputs.drydock_days[inputs.drydocks[k].age]
  off_hire: d     = sum(overlap(drydock[*]))
  charter_days: d = (period.days - off_hire)                     | during operations

  rate: USD/d = interpolate(inputs.charter_curve, year)
              | grow inputs.macro.usd_cpi | lag inputs.charter_lag
  revenue: USD = charter_days * rate * (1 - inputs.commission)

  running_costs: USD = sum(inputs.daily_costs) * period.days | grow inputs.macro.usd_cpi
  insurance:     USD = inputs.capex * bands(age, inputs.insurance_bands)
  tonnage_tax:   USD = inputs.capacity * inputs.tonnage_tax  | during operations
  ebitda: USD = revenue - running_costs - insurance - tonnage_tax

  capex: USD = inputs.capex * inputs.spend[construction.period]    | during construction
}

financing.rfn

module finance "Financing" on quarterly {
  capex: USD = ship.capex                          // summed into quarters

  /// The loan is in rupees; the ship earns dollars
  balance loan: PKR {
    + inputs.max_gearing * capex in PKR
    - principal
  }
  period tenor = operations.start for inputs.tenor
  interest:  PKR = loan.opening * (inputs.kibor + inputs.spread)
  principal: PKR = clamp((ship.ebitda in PKR) / 1.30 x - interest, 0, loan.opening) | during tenor
  fees:      PKR = inputs.upfront_fee * inputs.max_gearing * inputs.capex in PKR
                 | at construction.start
  debt_service: USD = (interest + principal + fees) in USD
}

module returns "Returns" {
  project_cash: USD = ship.ebitda - finance.capex
  npv_usd = xnpv(project_cash, rate: inputs.wacc_usd)
  npv_pkr = xnpv(project_cash in PKR, rate: inputs.wacc_pkr)
  project_irr = xirr(project_cash)                    // 11.0% in the workbook
}

What this model needed from the language

Days inside a period. overlap(drydock[*]) counts the dry-dock days that fall in each month, including one that runs across a month end.
A lag. Charter rates reset three months after the market: | lag 3m.
Age bands. Insurance steps up at 10 and 15 years: bands(age, …).
A rupee loan against dollar earnings, with returns in both currencies.