Patrón Deportivo de Bahía (Chile) common mistakes
Patrón Deportivo de Bahía (Chile) · Understand the traps and how to avoid them.
Citing a general COLREG rule (e.g. 'power gives way to sail') without first stating the vessel-type/visibility/water-body hierarchy, so the answer is wrong for narrow channels, traffic separation schemes, or when both vessels are power-driven.
Candidates memorise the steering-and-sailing rules as a flat list and skip the applicability order (Part B section I vs II, Rule 9/10 overrides), because the exam statements often present a simple two-boat scenario that tempts a shortcut.
What to do instead
Before selecting an answer, write the hierarchy in the margin: what type is each vessel, are they in sight, in a narrow channel/TSS, is one RAM/NUC/fishing/towing? Only then apply Rule 13 (overtaking), 14 (head-on), 15 (crossing). Practise 20 scenarios where the 'obvious' rule is overridden by Rule 9 or 10.
Treating the required safety equipment list as fixed instead of scaling it to the vessel's zone of navigation, length, and number of persons on board, and omitting items such as the second means of signalling or the appropriate number of lifejackets for children.
Candidates study a single checklist from one course and never internalise that the Chilean reglamento ties equipment to categories of navigation (aguas abrigadas, costera, alta mar) and to SOLAS/IMO small-vessel provisions.
What to do instead
Build a matrix: rows = zones of navigation, columns = equipment items, and fill each cell with the required quantity and standard (e.g. lifejacket per person plus spares, SOLAS-approved lights, liferaft capacity). Rehearse the matrix from memory weekly and check against the current reglamento text.
Calculating GM (metacentric height) or GZ from a formula without first verifying the loading condition, free-surface correction, or whether weights were added high or low, producing a stable-looking but wrong answer.
Candidates plug numbers into GM = KM − KG and forget that adding a weight above the centre of gravity raises KG and that slack tanks reduce effective GM; the arithmetic looks right so the error goes unnoticed.
What to do instead
Adopt a fixed procedure: list all weights and their vertical positions, compute final KG (moment method), apply the free-surface correction (FSM/Δ), then compare to KM. Always state assumptions (tank status, weight placement) in the answer and sanity-check whether the result is plausible for the hull type.
Plotting a coastal fix by measuring distance off a single charted object or by dead reckoning alone, then reporting a position with false precision and no error circle.
Candidates confuse the ability to read the chart with the ability to fix position; they skip the requirement for two or more position lines with a good angle of cut, and they forget compass variation/deviation and tidal stream when advancing a DR plot.
What to do instead
Always construct at least two intersecting position lines (bearing + distance, or two bearings with 60–90° cut), label the fix with time and log, and draw a cocked hat/error circle. For DR, apply variation and deviation explicitly and add set and drift for the elapsed time before plotting.
Reading a synoptic chart or forecast and giving the wind direction/strength at the vessel without correcting for the difference between true and apparent wind, or ignoring the local topographic effect of the bay and headlands.
Candidates answer from the isobar spacing and the 'wind blows around lows' mnemonic but do not account for the fact that a forecast is for open water at a standard height, while the vessel experiences accelerated, bent or funnelled wind near the coast.
What to do instead
State the forecast wind (direction from, speed), then explicitly derive the expected local wind over the water using topography (acceleration off headlands, calms in lee, sea-breeze timing), and distinguish true from apparent wind whenever the boat is moving. Practise interpreting 3–4 real charts with a written reasoning chain.
Transmitting a distress alert on VHF without the correct structure (MAYDAY ×3, this is, name/callsign, position, nature of distress, assistance required, persons on board) or using PAN PAN / SÉCURITÉ for the wrong urgency level.
Candidates memorise fragments of the procedure and, under exam pressure, mix the order of elements or choose the wrong priority signal; they also forget DSC/MMSI and the requirement to wait for acknowledgement before switching to working channel.
What to do instead
Rehearse the full MAYDAY script aloud in the exact order until automatic, then do the same for PAN PAN and SÉCURITÉ with a one-line definition of when each applies. Include the DSC alert step, the MMSI, and the follow-up ('over') in every practice run.
Diagnosing an engine fault by symptom alone (e.g. 'won't start = battery') and skipping the ordered check of fuel, air, compression and ignition/spark, or ignoring the cooling-water and exhaust tell-tales.
Candidates learn maintenance tasks as isolated items and lack a troubleshooting sequence, so they jump to the most familiar cause rather than the most probable one given the evidence.
What to do instead
Memorise and apply the four-element sequence (fuel, air, compression, ignition) in order for a no-start, and for overheating check raw-water intake, impeller, thermostat and coolant in that order. Practise on a real engine or a labelled diagram, stating the next test at each step.
Answering MARPOL/oil-pollution questions by reciting 'no discharge' without distinguishing the annexes, the special areas, and the permitted exceptions (e.g. treated sewage, food waste, oily-water separator limits), or overlooking the garbage record and placard requirements.
Candidates compress all pollution rules into one slogan and do not separate Annex I, IV, V and VI or the meaning of 'special area', so they misclassify a discharge as legal or illegal.
What to do instead
Build a table by annex: substance, general prohibition, permitted exception and limit, special-area status, record/placard requirement. For each practice question, name the annex first, then apply the rule; verify against the current MARPOL text rather than memory.
Manoeuvring answers that ignore the vessel's pivot point, transverse thrust, and the effect of wind/current on a light displacement hull, so the described manoeuvre (e.g. springing off a berth, turning in a narrow basin) would not actually work.
Candidates learn manoeuvres as verbal recipes ('port helm to leave') without connecting them to the forces acting on the hull, and they forget that a single-screw boat kicks its stern to port in astern.
What to do instead
For every manoeuvre, draw the force diagram: propeller thrust direction, rudder angle, pivot point location, wind/current vector. Predict the resulting motion before stating the helm order, and practise springing off and turning short round on paper with a marked pivot point.
Using a chart or publication without checking its edition, correction status (Notice to Mariners), datum, and units, and treating a GPS position as directly plottable on an uncorrected or differently-datumed chart.
Candidates assume any chart is current and that WGS84 positions overlay any chart, forgetting that older charts may use a local datum and that symbols/units (metres vs fathoms, drying heights) change meaning.
What to do instead
Before plotting, read the chart title block: edition date, latest correction, horizontal datum, and units; note any datum shift to apply. Include a one-line 'chart check' in every plotting answer and rehearse extracting the correction status from a sample chart and NtM.