DISTANT BLUE - Ohlson 38

Copyright © 2012 Charles McGrory
My comments: Osmosis and Osmosis Blistering
The actual osmotic travel of water into the laminate on a gross scale would not be good for the
laminate. However, it is my understanding that the problem is substantially aggravated when such
water migrates and finds a ‘void’ within the laminate and when such a ‘void’ contains un-reacted
polyester, left over from production, then a reaction kicks in to result in osmosis blistering which can
be severe. This is likely aggravated by salt water and any chemicals picked up in an industrial
harbour. The longer the hull is immersed in water, the greater the potential for osmotic migration of
the outside water into the boat hull.
A winter ashore will help decrease the migration and given ventilation and heat there would be some
release of the water back to atmosphere, restrained by the underbody coatings and shield which
would be preventing release back to atmosphere.
Distant Blue Construction
I accepted the surveyor’s report, cautions and recommendations and bought the boat. I had seen no
indications of blistering and noted that there were indications of good construction e.g. the hull deck
joint flange of some 15-20mm was clean and stable with no indications of any leakage down through
the teak toe-rail bolts from twisting or warping of the hull-deck. The original Lloyds A1 inspection
certificate was present. A previous French potential buyer who was considering the boat for a sailing
school backed off when he heard there was moisture present.
Distant Blue hull was designed in 1960s built to 1960s specifications in 1979/80 in the days of thick
GRP construction. The Tyler reputation came from their use of clear laminates where they could see
any voids and likely in those days, slow careful squeezing of the laminates and resin, reducing
substantially the chances of voids and un-reacted polyester. Leaving the hull to cure carefully in the
mould would assist in the completed reaction of any polyester leaving no reactant left.
I considered that any problems were not imminent and could be prevented and the modern boat did
not provide any more stable expectation and was not the sea boat I wanted.
‘Modern’ Cored Construction and Design vs. Ohlson 38
Many boats from the late 70s and on into 1980s, began to move to thin GRP skins and balsa-cored
hulls; also the increased demand caused pressure on production managers to fast-cure or cut short
the long cure-time in the moulds. CS Yachts in Toronto in the 1980s had severe problems of osmosis
blisters in new yachts under five years old. They then offered new owners an upgrade cost option to
seal the hull with shield; not sure if this changed their speed of process in the moulds.
C & C yachts near Toronto had moved to balsa-cored hulls and decks. I know of one ten-year old boat,
C & C 36 where the deck was rotting around the stanchions. The problem with balsa-cored boats,
while claiming to have epoxy-sealed balsa segments in the core, is that if water migrates through the
hull by osmosis into the balsa, then water may start to ‘liquefy’ the balsa. On this C & C 36, it was
quite possible to take the stanchion, waggle it around and watch the deck deflect. Found this out
halfway from Bermuda to Boston! Also the spade rudder was very tiring to steer in Force 7-8 seas.
In our harbour in Sarnia, Ontario, a C & C 39 came in from the summer cruise in Lake Huron. She had
hit a rock and divers sent down reported no obvious damage other than a dent in the lead fin keel.
She was then sailed all summer. The end of season she was hauled out and later that winter at some
20◦ C below, the hull all around the keel ‘exploded’. Water had migrated into the balsa from cracks in
the hull along the keel base where the keel had torqued on the impact of the collision with the rock;
the expansion of the water turning into ice ruptures the hull along the keel length and for nearly a
metre outboard. So you can see I am not a great admirer of ‘modern’ sandwich construction.
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