A standard survey is non-destructive: nothing is drilled, cut or dismantled. Sometimes the true extent of a finding can only be seen by taking a laminate sample or opening an area. That is planned separately and done with the owner's written consent.
When is it needed?
- Moisture and sounding show wet core or separation in an area, and its extent needs to be known.
- With suspected osmosis, how deep into the laminate it has gone.
- On steel boats, closed areas the ultrasonic gauge cannot reach.
- Seeing how an earlier repair was carried out.
Methods
- Core sample
- A small-diameter plug is taken from the laminate; ply structure, core condition and wetness are seen.
- Controlled opening
- A small window is opened in a lining or laminate to see behind it.
- Paint removal
- Paint is taken off a suspect area to expose gelcoat or steel.
Working rules
- Written consent. The owner's written approval, stating location and scope.
- Yard or tradesman. Opening and repair are done by the owner's yard or tradesman.
- Repair plan. Sample locations are set beforehand; every opening is closed the same day or as planned.
- Record. The opened area is photographed; the finding goes into the report as a separate section.
How a sample is taken
In destructive testing, a small piece is cut from the hull. The spot is chosen to do least harm to the structure while best representing the finding; often around an existing through-hull or in an area due for repair anyway. The piece is labelled, its location photographed, and the hole closed at once by the chosen repair method.
What the piece shows
- Laminate thickness and ply count, compared with the schedule.
- Separation or voids between plies.
- In sandwich construction, the core's condition and its bond to the skins.
- In the laboratory, fibre content and the state of the resin.
Consent and responsibility
Destructive testing is done with the owner's written consent. Before purchase, the seller may not give it; the test is then done after purchase or on terms agreed with the seller. A competent tradesman cuts and repairs; the surveyor chooses the spot, examines the piece and reports the result.
Using the result
The result also tests the non-destructive readings. If a piece from an area reading high on the moisture meter really is wet, the same readings elsewhere on the boat can be interpreted with more confidence. A small cut supports a decision about a large area.
Cost
Cutting, laboratory examination and repair are separate items, priced in writing from the start.
Alternatives first
Before cutting, the non-destructive options are exhausted: moisture mapping, sounding, thermal imaging and, where useful, ultrasonic thickness. Destructive testing answers the question they cannot.
Where a purchase decision or a major repair depends on that answer, a small cut is often the most economical route to certainty.
The cut is repaired to the surrounding laminate's thickness and ply schedule and checked by moisture reading afterwards. A well-made repair does not affect the boat's value and is documented in the report with location and method.
Photos of the piece and the laboratory result are attached to the report, so the owner and any later surveyor can see exactly what was found and where.
That leaves no room for doubt about the finding.