Soft patch

What it is

A soft patch is a local zone of deck or structure that springs or gives under pressure, often from a wet core or from damaged laminate. One soft spot is a point on the survey map, not cosmetics. Several zones change the negotiation and the scope of the haul-out. A repair price is not taken from pressing with a heel.

The Medusa Marine survey sample on Novella says it plainly: the comparative scale of a Tramex Skipper 5, from 0 to 100, is arbitrary and does not mean a percent of moisture in GRP. The figures there are called scale readings. On that deck the laminate is mostly solid, and the plywood pads are at the fittings. The deep scale gave 90 to 100 at the chainplates, the windlass and the genoa track. The survey's explanation: moisture in the plywood pads under the bolts. The shallow scale was lower, and the laminate is not "killed". They walked the deck: it was firm, with no noticeable rise against a straightedge. A high meter at a plate, with no flex, is not the same diagnosis as a spongy sandwich. The escutcheons around the straps are re-bedded so water does not run into the end grain of the web-frame plywood.

Canadian Boating describes the usual survey pair: a moisture meter plus sounding. Softness underfoot often goes with a wet or rotten core and with delamination. One meter without context is a craft; glass thickness, materials and the instrument throw it off. Next comes sounding, and if needed small core samples. The repair is cut back to a dry, clean core, and the core type and thickness are matched again. There is no cookie-cutter price. It is not always a catastrophe: size, place and moisture decide how urgent it is. Paint hides the look; flex underfoot still gives it away. Core is a common case, but sandwich decks are not the only ones at fault: solid laminate and plywood soften too.

The Tramex Skipper 5 datasheet: two depths, about 10 mm and 30 mm, for decks and GRP sandwich. The wood scale is 5 to 30 percent moisture content; for building materials the reference is 0 to 100. This is a search for a wet core, not a universal percent for any laminate. Solent Marine Surveys writes the same rule: their instruments do not show the actual percent of moisture in GRP or FRP; a Protimeter Aquant works on a comparative scale of about 0 to 999. Solent's working bands are that firm's bands, not a law for every boat. ISO 12215-2, for small craft up to 24 m length of hull, requires the core to limit water getting past the zone of a possible skin breach. That is a construction requirement, not a bill from a heel.

Sounding and the meter tell the cases apart. A dull sound is often a wet or rotten core. An empty thunk is more often the top skin coming away; the core under it can still be dry. A small zone at a cleat and a large one on the coachroof are different in urgency. A core sample is taken only with written consent. One repair priced as a percent of the boat, from someone else's case, is not carried here as a table. The English class term soft patch, a temporary repair on a classed ship, is another meaning of the words. Those rules are not put on this card. A euro figure is not printed from a press of the heel. Nearby on the site: deck core, marine plywood, moisture meter and survey checklist are other pages, not this bill.