Charles,

You'll get more knowledgeable replies than this, but some preliminary
observations:

1/ Insulation makes no difference unless an object is heated. You're not
heating the boat, so it will all become ambient temperature. Insulation
would slow it, but when it's going to be below freezing for months - well,
it won't stop it from getting cold in there, only slow it, perhaps by a few
hours.

2/ You will largely escape the greenhouse effect by having it covered, to
whatever extent a tarp would cause that.

3/ Humidity tends not to condense inside a covered object - this is just
observational from my car! The ground can be covered with dew or frost, the
car dripping or icy outside, and although the overnight interior temperature
of the car must have been about ambient, nothing condensed in there.
Actually the same happens in my boat over the summer - it will be dripping
with dew, some mornings, but not inside even the cockpit, which I cover but
often leave the back open. So, if you've got some kind of cover up - whether
its summer canvas or a winter tarp - I think you'll be protected from
condensation.

4/ The only concerns I have are for the canvas itself, and more
specifically for the plastic window portions. I have been told by marina
operators and canvas repairers that it tolerates cold very poorly,
especially if it moves at all as in a wind, but even if it doesn't, and so
to take it home and keep it inside. They said this would keep it clear for
years longer than leaving it out in freezing temperatures. The cloth part of
the canvas isn't so fragile, I wouldn't imagine, but will still be subject
to wear from wind movement, depending how sheltered is your shelter.

5/ Boats stored indoors get dusty. I'm not sure about those stored
outdoors but covered. But I think many boaters cover even an indoor boat
with a loose canvas to keep it cleaner.

6/ I have quite an elaborate frame for my winter tarp, so that it will
shed snow, which apparently under the the wrong, occasional conditions can
be wet and sticky enough that it will stick to any but quite steep surfaces,
and then be heavy enough to bend windshields; but the frame is also strong
enough to take winds coming right off the water. Last winter we had some 80
km/h winds, and my tarp suffered, but the frame held. But if you're out of
the wind and snow, a simpler wrapping might suffice, and not be such a big
deal to assemble and later disassemble.

7/ A simple thing to do would be to contact a few people who have
overwintered there for many years in similar boats and ask their advice.

8/ But I'm thinking cover.

Charles

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Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

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"Charles Brown" wrote in message
.cable.rogers.com...
I bought a used 28' cabin cruiser this summer and it is layed up in a
marina north of Toronto for the winter in a covered slip. The boat is
completely covered by its camper cover but the slip is open on all sides
except for the roof above. The marina operator says it doesn't need to
be wrapped in plastic if it is in the covered slip and they only do this
for boats which were hauled out of the water and stored in the open on
land.
I am concerned about the effect of the cold air causing appliances
and wood to warp and crack as well causing mildew and figured that the
plastic wrap insulates as well as protects from rain and snow. Have I
got anything to worry about or is the marina operator correct?
Thank you.
Charles.