DS Marine Surveys

991 Ridgemount Blvd. Oshawa Ontario L1K2K7 Ph: 905-449-2176
Condition and Valuation Surveys for Pre-Purchase and Insurance - Consultations - Appraisals - Underwater Accident Investigations and Salvage Supervision

Surveyor - C. David Sandford SAMS® / AMS®

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Osmosis The Dreaded "O"

This one word has probably scared the pants off of more fiberglass boat owners and potential buyers than any other but with careful examination with the proper equipment (see "Moisture Detection") by an experienced operator it can be identified , assessed and in many cases successfully repaired.

Fiberglass has proven to be an excellent material for boat construction and for many years it was thought to be moisture resistant substance. However time has shown this not to be the case as fiberglass can and will absorb moisture through the gel coat and into the laminate. This can cause chemical changes in the physical make up of the hull in the form of osmotic blistering of the gel coat and delamination of the resin / glass matrix.

How does this actually occur? First off moisture has to penetrate the gel coat. The most obvious way for this to occur is through cracks and imperfections in the gel coat surface. Moisture can also pass through the gel coat at the molecular level. Basis chemistry teaches us that water molecules are made up of 2 hydrogen and 1 oxygen atom. This being the simplest and most basic molecule, is also the smallest and over time, it is able to pas through the larger and more complex cross linked polymer molecules found in the fiberglass gel coat.

Moisture in the Fiberglass Laminate, Blisters and Delamination

When fiberglass hulls are manufactured voids and air pockets occur in the laminate. (Note: in recent years modern manufacturing processes such as vacuum bagging have reduced this tendency to a large degree). Through capillary action moisture passes through the gel coat it travels along the glass strands in the laminate finding it's way to any voids or air pockets in the laminate. It then builds up forming visible bubbles in the gel coat surface and in severe cases the pressure exerted causes delamination of the resin / fiberglass matrix and can actually separate the laminate layers from the core itself. See: Fiberglass Hull Construction. When this occurs extensive and sometimes costly repairs are required.