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?




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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?

For a wood boat, I would agree if the boat was secured along the whole
length of the boat instead of two or four places. Most cradles only
secure at the bow or stern - essentially much the same as jacks.

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.

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.

While I have an opinion on how I store my own boat, I can't honestly
say that my method is any better than the ordinary four jack approach
used in most marinas that store on hard points.

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)

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.




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.



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?



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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)

"Harry Krause" wrote in message news:bv0kf9

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.

At the marina where the Queen lives, every boat stored on land rests on
three (sometimes four) keel baulks, with jack stands for stabilization only.
Most have two fore and two aft, but larger vessels -- maybe 38 ft or
larger? - have three pair.

The only boats I've seen here or elsewhere supported on jack stands alone
(with no keel support) have been smallish runabouts, perhaps 20 ft or less,
and even those appeared to be temporary setups. I've never had a
conversation with anyone who advocated storing a boat, particularly a larger
one, that way.

If your marina is storing large vessels in this way, I'd be leery of
trusting their advice on other matters, and I'd suggest that the bulk of the
owners are probably unaware of the circumstances.

JG

On Sun, 25 Jan 2004 11:28:06 -0500, Gene Kearns
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?

Very much agree. It is not uncommon to see boats held off the hard by
two stacks of loose 4 or 6 bys at the stern and one at the bow. (Pray
that it doesn't blow...) If the same boat was aground in shallow
water supported in like manner, any of the towing services would have
clear recourse to file for salvage (*not* towing) charges. Somehow,
in the boatyard, principles of physics and common sense seem to become
mysteriously inapplicable.

Boats are designed to be supported at many point by water. While
three points may define a plane, it is a poor way to support a boat
and exposes it to stresses never anticipated by the designer.

If that is the case, then why are there three defined "strength" or
lift points on the Contender - all above water? In fact, the Ranger
can be lifted in a similar fashion to the Contender - one bow and two
stern lift points.

Again, I'm not a structural engineer, but it seems intuitive that load
stresses should be distributed evenly from any point on the hull.

Right/Wrong?

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)

On Sun, 25 Jan 2004 11:17:44 -0500, "John Gaquin"
wrote:


"Harry Krause" wrote in message news:bv0kf9

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.

At the marina where the Queen lives, every boat stored on land rests on
three (sometimes four) keel baulks, with jack stands for stabilization only.
Most have two fore and two aft, but larger vessels -- maybe 38 ft or
larger? - have three pair.

The only boats I've seen here or elsewhere supported on jack stands alone
(with no keel support) have been smallish runabouts, perhaps 20 ft or less,
and even those appeared to be temporary setups. I've never had a
conversation with anyone who advocated storing a boat, particularly a larger
one, that way.

If your marina is storing large vessels in this way, I'd be leery of
trusting their advice on other matters, and I'd suggest that the bulk of the
owners are probably unaware of the circumstances.

I've never really paid much attention to it down at my marina - I'll
take a closer look when I head down this coming week.

I might even give a frienid of mine a call - he's a structural/civil
engineer.

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)

Boats are designed to be supported at many point by water. While
three points may define a plane, it is a poor way to support a boat
and exposes it to stresses never anticipated by the designer.


Disagree. I recall discussion in both structures and hull design classes
about accounting for loads associated with construction, launching,
dry-docking, grounding, and other special conditions.

I would not swear that recreational boats are subject to the kind of
analysis performed as part of a ship design, but I would expect that
ABYC structural requirements are intended to account for such loads.
Think of ABYC as analagous to your county building codes. The architect
won't calculate snow loads on the roof because the mandated timber sizes
and spacing allow for those loads.

dave
BS Naval Architecture & Marine Engineering, Webb Institute, 1982

Dave Skolnick wrote:

Boats are designed to be supported at many point by water. While
three points may define a plane, it is a poor way to support a boat
and exposes it to stresses never anticipated by the designer.


Disagree. I recall discussion in both structures and hull design classes
about accounting for loads associated with construction, launching,
dry-docking, grounding, and other special conditions.

I would not swear that recreational boats are subject to the kind of
analysis performed as part of a ship design, but I would expect that
ABYC structural requirements are intended to account for such loads.
Think of ABYC as analagous to your county building codes. The architect
won't calculate snow loads on the roof because the mandated timber sizes
and spacing allow for those loads.

dave
BS Naval Architecture & Marine Engineering, Webb Institute, 1982


Uh, you're not from New Haven, are you, Dave?

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Email sent to is never read.

On Sun, 25 Jan 2004 13:12:06 -0500, Gene Kearns
wrote:

On Sun, 25 Jan 2004 16:51:46 GMT, Short Wave Sportfishing
wrote:


If that is the case, then why are there three defined "strength" or
lift points on the Contender - all above water? In fact, the Ranger
can be lifted in a similar fashion to the Contender - one bow and two
stern lift points.


Guess who decided where those lift points are... and why!

I'm assuming that the engineers who designed the boat did.

Intuitively, you should see that picking *up* on predetermined lift
points should be different from three "sorta flat" points chosen
merely for convenience by dock hands to support the boat's weight by
"pushing up".

Correct - the stresses involved in using three lift points would be
greater than those used when the vessel is in storage.

Again, I'm not a structural engineer, but it seems intuitive that load
stresses should be distributed evenly from any point on the hull.

Right/Wrong?


Wrong. Hulls are not made that way... they aren't the "same strength"
all over. Hull thickness is not the same all over and structural
members don't run "everywhere."

Let's take my Ranger as an example. The bottom is thicker glass and
has a stringer system with a "tub" and foam is poured inbetween - the
entire structure is one solid mass - of differing densities for sure,
but still. I can't quite understand how supporting a fairly solid
mass on three or four points, beyond the stability factors, would be
more or less detrimental than a complete stem-to-stern cradle.

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)