A wet core repair succeeds or fails on mapping the wet area correctly and sealing the water's entry point. The method is chosen by the size and location of the area and how much the deck surface needs preserving.
Before the repair
- Boundary. Wet and separated areas are marked with moisture readings and sounding; the repair extends a little beyond.
- Source. The fitting or penetration letting water in is found.
- Method. One of the three below.
Three methods
- From above
- The top skin is cut and lifted, wet core removed, the lower skin dried, new core bedded and the top skin relaminated. The most reliable method on large areas; the deck surface and non-skid are redone.
- From below
- The same work done from inside; the deck surface is preserved. Requires removing interior joinery and overhead work.
- Injection
- Resin injection for small, dry separations. Not a solution for wet, rotten core; it traps the water inside.
Materials
At hardware points, fill or solid laminate replaces core, so bolt holes can never carry water into the core again. New core is chosen at a density matching the original.
Checks
Before laminating, dryness of the lower skin is confirmed with moisture readings; after completion, the area is sounded and read.
What we often see
- Wet core in the transom: High moisture readings and a dull sound in the transom around the ladder and exhaust outlet.
- Wet core around deck fittings: Moisture readings rise around winch and track bases; the deck flexes underfoot.
Choosing the method
There are two ways to repair wet or debonded core: open the top skin, or open the bottom skin from inside. Repair from the top is easier but leaves marks on the deck surface, non-slip pattern and paint. Repair from inside keeps the appearance but means overhead work and removing linings. The choice follows the size of the area, access and the expected finish.
Mapping the edges
Before repair, the wet area is mapped by moisture readings and sounding. Once the skin is open, the true edge is sometimes larger than the map; so the quote is given with a rate per unit area. Wet core is removed until sound, dry core is reached; leaving any wet part inside means the problem starts again.
Drying
With the core removed, the area is dried completely before new material goes in. Rushed drying leaves a weak bond. Dryness is confirmed by moisture readings.
New core
New core matches the original or has equivalent properties; where fittings will go, filler or solid laminate replaces core. A bolt hole drilled there later will then not lead water to the core.
Closing the skin
The opened skin is relaminated in the original ply schedule with a proper scarf, then finished to match its surroundings. Checking the repair by moisture reading the next season shows whether it has worked.
Cost
The cost is set mainly by area, access and finish. Catching wet core early, around one fitting, keeps the repair small and cheap.
Left for a few years, the same problem can spread across a large part of the deck.
When complete, the repaired area and its edges are marked on the hull sketch and photographed. The record makes the next survey's check easy and shows at sale that the repair is documented.
A documented repair reassures a buyer rather than worrying them.
Keep the record with the boat's papers.
Early action is always cheaper.