On Sun, 25 Jan 2004 10:19:53 -0500, Harry Krause
wrote:

Short Wave Sportfishing wrote:

On Sun, 25 Jan 2004 09:38:58 -0500, Harry Krause
wrote:

Very few of the large boats winterized where we keep ours are properly
supported, in my opinion.

Most of the large boats are being held off the hard by jacks or by wood
blocks jacked into place and only at four places on the boat, two at the
stern and two forward of amidships.

My feeling is that if you are storing a boat on land, it ought to be on
a cradle, a device that supports most of the bottom and spreads the
loads out fairly equally. Supporting the weight of a large boat of many,
many tons displacement on four tiny points means that most of the boat's
weight is unsupported and will put undue stress on unsupported areas.

Agree? Disagree?

What kind of cradle?

A full cradle that form follows much of the hull bottom along its usual
wetted surface area.

Ok, we can agree there.

It's my opinion that for large vessels (say over 25 feet), the jacks
should be used as stabilizers and the boat should be supported along
the keel by blocks. My Contender 31 is supported at three places
along the keel and four jacks front and rear. The weight is
essentially distributed along the keel and the jacks are there only to
keep it upright and level.

Well, a lot of these larger boats have no keels. You're doing the right
job with your boat, but the add'l keel blocks are not what I am seeing
in the yard I visited.

Neither am I, but I don't think it's a problem If it were, you would
think that yards would change their practices if only for liability
purposes.

However over the years I have looked at a ton of boats that have only
been on jacks, incuding wooden boats, and there does not seem to be
any problems arising from that method of storage. There was one Egg
Harbor that I looked at that had been on the "hard" for ten years and
the hull looked fine - not even any crazing of the fiberglass.

Wouldn't all that unsupported weight...diesel engines, for example, even
on stringers, tend to deflect the bottom with nothing - like water or
some supports -pushing up?

Over time, perhaps, but a properly designed boat would have the load
distributed equally. There are always going to be point stresses on a
hull even when it's in the water - you own mention of more weight/mass
in the stern is a good example of that. Fiberglass also has a load
distribution factor which is dependant on the quality of the glass,
the type of glass, type of epoxy and what type of design - deep-vee,
semi-vee, no-vee - whatever. I have the prints for the Contender and
while I am not a structural or naval engineer, I'm satisfied that I'm
being overly cautious with the keel blocks.

Intersting though - next time I'm down at the marina (this coming week
sometime) I'll look around a little.

Later,

Tom
S. Woodstock, CT
----------
The years will bring their Anodyne,
But I shall never quite forget,
The fish that I had counted mine
And lost before they reached the net.

Colin Ellis, "The Devot Angler" quoted
in A. R. Macdougall, Jr's "The Trout
Fisherman's Bedside Book" (1963)