Hurricane Storage Ashore: A Surveyors View

Hurricane Storage Ashore: A Surveyors View

Post by Geoff Schult » Wed, 06 Jul 2005 06:39:21

The following is an article which appeared in April, 2005's issue of The
Compass.  I OCRed it and sent it to a friend who's planning on leaving
his boat on the hard in Honduras for hurricane season.  It has lots of
good points, so I'm reproducing it here without permission.

-- Geoff

Hurricane Storage Ashore: A SURVEYOR'S VIEW
by Hugo du Plessis

Like everyone else, I have been saddened by the Images of yet more
yachts destroyed by a hurricane, most recently In Grenada where I have
spent many happy years and many hurricane seasons in safety. I am
particularly appalled by the destruction of yachts laid up ashore in
what should have been safety. I do not believe such mass destruction is
Inevitable, although I admit that during 20 years in the Caribbean I
have been spared the experience of actually being in a hurricane.
(Hurricane Rule Number One: Don't be there.) However, as an experienced
surveyor with 50 years experience of fiberglass boats, I do have the
following observations.

Years ago, when I had a boatyard, no yachts were ever laid up ashore
with masts stepped.

As also was the custom of the time, we used wooden pit props as
supports, with wedges driven in firmly with a sledge hammer. However,
that was back in the days when most of the cruisers were sturdy wooden
boats. You can do that with a wooden boat, but not with fiberglass. It
is too flexible. As the wedge is driven home, thefiberglass hull is just
pushed inwards more and more, so the support is never firm.  Screw
struts, on the other hand, can be adjusted and readjusted without
exerting pressure on the hull.

With fiberglass it is absolutely essential that all supports are placed
at strong points in the hull such as bulkheads. These are easily located
by tapping. This is where some boatyard staff are careless or ignorant,
and it is the management's duty to make sure their staff know this and
check that it is done.

Also, all the weight of the boat must be taken on the keel blocks, never
on the supports, which are purely for steadying. If a support is not
placed at a strong point, a fiberglass hull Is sufficiently flexible
that it will Indent and be damaged. This is often revealed by cracks
surrounding an area where a tight support has. made an indentation
perhaps in previous years. Due to creep, the indentation often becomes
permanent. Because of the nature of fiberglass, creep can only occur
through local failure generally under a stress maintained for a
considerable time. Fibreglass is particularly susceptible to hidden
damage, i.e. weakening through low-level damage without any outwardly
visible signs. (For more detailed explanation of the way fiberglass
fails, see my book Fibreglass Boats, third edition.)

It is easy to check if a support is too tight by sighting along the hull
and seeing it there is any indentation or distortion at supports. This
should be done regularly, because keel blocks can sink or be undermined
by worms or ants, throwing weight onto the supports.

If supports are wrongly placed and the mast is up, the boat will rock in
a strong wind because of the flexibility of the hull. Then supports can
fall away or loosen, and over she goes. There have been occasions when,
surveying a yacht ashore with its mast up in gale conditions, I have
really been quite alarmed and feared it would capsize at any moment. The
forces on a mast in a gale are substantial. We all know how a gust can
make a boat heel even under bare poles, and knockdowns at anchor during
a hurricane have been reported.

The motorized sledges used in some boatyards can damage a boat because
the side arms have no fore-and-aft adjustment to align with bulkheads. I
have seen boats rock alarmingly due to flexing of the hull as the sledge
bumps across the boatyard. Also the side arms have powerful hydraulics
and are often used to lift or position the boat, which should never be
done.

Balanced on its keel ashore, a boat has no righting moment as It does
when afloat and It Is hard to imagine anything so unstable as a boat
balanced on its keel. This raises another danger: rows of boats in close
proximity. One goes over and the rest go down like ninepins, with
shattered masts in a lovely tangle. This domino effect does not even
need storm conditions. It has happened twice in one of the largest
Trinidad yards and caused thousands of dollars of damage to hulls and
masts. In hurricane conditions it is a very real danger.

I like the almost universal use in the Caribbean of***struts along
with the firm tripod base. More expensive of course, but worth the
security and far, far superior to the old pit props and wedges. (I also
like my own boat's well splayed twin keels.

She Just sits there and needs no supports at all. It would take a lot to
capsize her on dry land.) I do not know what these cost, but obviously
an adequate stock requires a substantial capital investment, so often
there are not enough to go round all the boats in a yard, or too few are
used for proper security. Three each side is not sufficient. The minimum
should be four at least, to allow for one falling. I see no reason why,
used In adequate numbers and with suitable precautions, they should not
give good support even in hurricanes. Their easy adjustability means
they can be tight without exerting undue pressure on the hull. They
should certainly be firmly lashed together so that they cannot splay
apart.

Some boats frankly frighten me by their instability ashore, balancing on
a minuscule short keel, the tip reduced perhaps to a mere point in
contact with the blocks and expected to take the full weight of the
boat. No doubt they are a designer's hydrodynamic delight, but a
nightmare for a boatyard. Wooden blocks are unsuitable: the very high
pressure from the narrow tip will dig into them like a chisel or split
them like an axe. Concrete blocks, too, will shatter. On grounds of
safety alone, a boatyard would be wise to ban boats with difficult-
shaped or exceptionally deep keels, especially in a hurricane zone. Or
quarantine them well away from other boats where they can do no harm
except to themselves when they fall over.

The principal risk in a hurricane is supports sinking Into the earth.
Many boatyards are on newly made-up ground, which In the Islands Is
often insufficiently consolidated: levelled but not rolled. Also, in
some places, the soft turns into soft gooey clay in wet weather. The
very heavy rain in a hurricane can be more devastating than the wind. It
softens the badly consolidated ground, supports sink and even tripod-
based stands can fall away. Supports are seldom placed on boards to
spread the ground contact. Rain can also undermine keel blocks so that
all the weight comes on the struts which, if at weak points, then burst
through the hull. (From the description of a case referred to me, I
believe that is what happened to one yacht in Grenada.) By their very
nature, boatyards are on low-lying coastal foreshore. The tidal surge
from a hurricane, several meters above normal, would flood most yards,
and may be backed by dangerously high waves sweeping over protective
reefs and banks. No made-up ground can withstand that. The scour will
undermine supports and keel blocks. Over goes one boat and takes
neighbors with it. In my view, noboatyard is safe for yacht storage
ashore in a hurricane area unless it is concreted so that there is no
risk of supports sinking.

It is probably inevitable that a boatyard will be inundated in a
hurricane, but I have often seen that happen in a heavy shower. On a wet
Christmas Day one year, a yacht went over because one support had been
placed on the badly Infilled trench dug in previous wet weather by a
heavy travel hoist. Most of the damage was done by the misplaced strut
the boat fell against.

It might be thought that a cradle would give better support than struts.
That is true. But unless the cradle has a wide base, or is itself
fastened down, the boat, complete with its cradle, can go over. In 1973
during The Night of the Great Wind" in Cork Harbour, Ireland (and that
was only Force 10, gusting 11) a 35-foot yacht, still attached to its
cradle, slid on its side right across the yard.

Another danger shown up by that storm was the way a cover can lift a
light boat like a parachute so that supports fall away or loosen. Four
Trappers, a popular lightweight class, were lifted and went over that
night. Only one did not fall, even though another had fallen against it.
Why? I discovered later there had been a leak In a***pit drain and the
boat was full of water. So there is a useful tip if laying up ashore!

Also in Ireland, which is exposed to the full force of the Atlantic
gales, yachts ashore are picketed down to stakes or concreted eyes. It
reminds me of wartime days in the Fleet Air Arm when a frequent order on
the airfield Tannoy was "Gale warning. Aircraft to be turned Into the
wind and picketed down." This seems particularly relevant in the case of
catamarans and trimarans which can literally fly in hurricane winds.
When boats are transported by road, they are secured to the trailer or
lorry by strong, ratchet tensioned straps, as are other heavy loads.
This would not be expensive to do in a boatyard, provided there were
stakes or ground anchors. The lesson seems to be that if yachts are to
be laid up ashore safely in the hurricane season, boatyards must be
designed with plenty of strong points so this can be done. A
good example is the car-deck of a ferry, which has means for securing
big lorrieswith safety chains.

The only practical improvement which I can see to the present system
would to combine the adjustable struts with long flexible, padded
stringers so they could be adjusted to bear on the whole length of the
hull, not just at a few selected strong points. Then make sure the
tripods are set on large pads. Better still, have wide welded bases. Any
permanent cradle would have to allow for fore-and-aft adjustment, which
is absolutely essential to ensure supports are placed at bulkheads.
Otherwise they are just a more expensive way to do damage, which can
just as wellbe done with a cheap pit prop.

I still consider the safest place for a boat to be in a hurricane is
ashore, firmly secured and with its mast down and no covers to create
lift. But above all, observethe ancient rule which I often quote: "Watch
thy neighbor as thyself." Especially if he's bigger! Finally, I always
remember the advice given me many years ago by my old friend Eric
Hiscock, "Only a fool keeps a boat in the Caribbean during the hur-
ricane season." I know that will not endear me to those who run the
Caribbean boatyards. Hurricane Rule Number One: "don't be there", is
still the only really safe advice. But as Chris Doyle has said, "Where
do you go?" If we're going to be here, let's be ready.

Hugo du Plessfs, is an Associate of the Royal Institute of Naval
Architects, a yacht surveyor and GRP consultant. He is the author of
Fibreglass Boats, Adiard Coles Nautical ?2002. ISBN 0-7136-6209-3.