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Osmosis (or Boat Pox as it is known in the USA) is a subject which has probably caused more panic and debate amongst owners of small boats than almost any other in maritime history!
But if we are to keep things in perspective, all boatbuilding materials have their weaknesses: for example, wood rots, suffers nail sickness, and is prone to attack by worm. Likewise, virtually all metals - including stainless steel and aluminium - corrode in a marine environment. And then there's Ferro-cement!
In practice, Osmosis in GRP is a natural ageing process, which is driven by the soluble solutes present in many polyester lay-up resins. These in turn result in unsightly blistering of the protective gel-coat layer. However, Osmosis is usually a superficial problem, and is most unlikely to cause sinking or loss of buoyancy.
If you would like to learn more about this fascinating subject, please download the free Short Guide to Osmosis and its Treatment.
You may also like to download the Short Guide to the use of Moisture meters, which shows how you can quickly and easily check your own boat.
Surveyors may also like to know that I am currently writing a revised Code of Practice for the use of Marine Moisture Meters, which will include guidelines for diagnosing and reporting osmotic conditions. A draft will appear here when the doccument is available.
Cored laminates provide a high strength to weight ratio, but are very susceptible to damage caused by moisture ingress.
This draft document discusses the main advantages and disadvantages of cored structures, and provides general advice to boat owners and surveyors on the subject.
This document does not yet have any photographs or diagrams, but these will be added when time permits.