cradle damage

[chrisb]

regarding the question below-extended season i attribute patchy osmosis in my previous yacht to the positioning and stresses placed upon the hull by the cradle supports used to support her whilst ashore in the winter. certainly the water meter seemed to suggest these 4 areas as the only ares of problem. i wonder if any one else has had the same problem. [fin keel supported by 4 pads and conventional cradle]

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[Mudplugger]

Guy in Brightlingsea had the same problem when fitting out a new Hull & Deck, after 3-4 years ended up with Osmosis where the hull supports fitted. Local surveyor, suggested it was down to the heavy duty foam/rubber pads, which absorbed/retained moisture for long periods, once they were wet. Regards Tony W

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[machurley22]

Surely not caused by stresses placed on the hull since the cradle pads should only be stopping the boat toppling over, not supporting any significant weight. Stresses ARE caused by the boat's weight all being supported on the keel rather than on the entire area of the hull (when afloat) but these wouldn't be localized at the cradle pads, I wouldn't have thought.

Perhaps the effect on your previous yacht was caused by the areas touched by the pads not drying out as well as the rest of the hull when out of the water.

Just a thought, IMHO

Dave

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[alahol2]

It's almost certainly because the pads had something absorbent on them. They absorb fresh water (rain, dew) and don't dry out. Fresh water is a killer for osmosis.
Left a racing dinghy over winter resting on grass (many many years ago) in spring there were more osmotic blisters than hull.
Used foam backed carpet on a GRP cabin sole. Condensation kept it damp. Lifted after 6 months and, you guessed it, covered in acne.
Nowadays my chocks are plain wood or 'UPVC wood', wouldn't let carpet near my hull!


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