Hurricane season is on us. It's time to assess the strength of your
anchoring system.

The usual figure of merit for an anchor in a given type of bottom is
the horizontal load that the anchor will withstand before breaking free
divided by the physical weight of the anchor. This figure can then be
compared to a weight resting on the surface that would provide the
equivalent horizontal holding force. Lightweight anchors, the type most
of us use are just that, relatively light shapes that gain their
holding power by digging into the bottom and using the mass of mud or
sand to add to their physical weight. Admittedly west coast conditions
differ from east coast conditions, deep water from shallow water, rock
bottoms from clay bottoms. Further the nature of the rode affects the
performance of the anchor. Transient forces of wave and wind may
momentarily exceed the holding power of the anchor. An effective rode
will spread those forces out in time to reduce to forces below the
anchor's horizontal holding power. This attenuation is a function of
the rode's elasticity gained either through stretch or catenary forces.
It is quite evident that a heavy all chain rode permits a shorter scope
than a rope, wire, or composite rode. But to equal the elasticity of a
nylon rode a chain would have to be too heavy for most recreational
boats to carry.

Wind drag on a boat is a function of the projected area at right angles
to the wind, the square of the wind speed, the density of the air, and
the dimensionless coefficient of drag which depends on the shape of the
boat. Drag coefficients have been determined from wind tunnel tests.
Some representative drag coefficients are:

Open parachute (or efficient spinnaker) = 2.0
Hollow hemisphere, concave to wind = 1.7
Flat rectangular plate = 1.28
Wires, cylinders, masts = 1.0
Cargo ship, wind dead ahead = .95
Fishing trawler, wind dead ahead = .9 to 1.05, depending on
superstructure, outriggers, etc.
Streamlined passenger vessel = .70
Recreational trawler = .70 to 1.0, depending on superstructure, masts,
outriggers, etc.
Sphere = .47
Hollow hemisphere, convex to wind = .38
Modern automobile = .26 to .35
Airplane = .09

Using Area in sq. ft., wind Velocity in knots, and the U.S. Standard
Atmosphere for air density, the equation for Drag in lbs. can be
written as:

Drag = .00339 x Coefficient of Drag x Knots^2 x Area

In a 20 kt. wind, a boat with an area of 100 sq. ft. at right angles to
the wind with a drag coefficient of 1.0  will have 135.6 lbs. of wind
pressure on its surface. A conservative way to estimate frontal area is
to multiply the beam by the height of the superstructure. An even
simpler way is to multiply the beam by 3/4 of the beam. By this
calculation, a Willard 30' trawler has about 100 sq. ft. of area. A
Nordhavn 40 has 160 sq. ft. of area. A Nordhavn 47 has about 195 sq.
ft. of area. A Nordhavn 72 has 330 sq.ft. of area.

The strain on the anchor rode in hurricane force winds is far greater
than most boaters imagine.

For each 100 sq. feet of frontal area:
20 Kts = 136 Lbs.
40 Kts = 542 Lbs.
60 Kts = 1220 Lbs.
80 Kts = 2170 Lbs.
100 Kts = 3990 Lbs.
120 Kts = 4882 Lbs.
140 Kts = 6644 Lbs.
160 Kts = 8678 Lbs
180 Kts = 10984 Lbs.

The breaking strength of proof coil 5/16 chain is 7600 lbs., of 3/8
chain is 10,600 lbs.
The breaking strength of 1/2 twisted nylon is 7500 lbs., of 5/8 nylon
is 12,200 lbs., but nylon rodes should be loaded to no more than 1/4
breaking strength to assure adequate stretch with a margin of safety.
At first glance it appears that a 3/8" chain, typical of many trawler
yacht anchoring rodes, would be sufficient to hold a boat with 200 sq.
ft. of area in a Category 2 hurricane but all is not what it seems.
Long before the chain broke, it would be stretched bar tight. Any
transient forces of waves or surge would be transferred directly to the
anchor, which, in all probability would be jerked out of the bottom.
Either that or the cleats would rip out of the deck.

Stretch is the enemy in most tasks involving rope. This includes all
lifting and tying tasks. Also situations where the rope is to prevent
some structure from moving. Shrouds and stays on a mast come to mind.
But rope stretch is an asset in climbing and anchoring. The rock
climber wants a rope that will stretch if he/she falls to attenuate the
shock. Boat anchoring also profits by rope stretch. The elastic limit
of new laid nylon rope is about 25%. This means that it will stretch to
125% of its original length and return to its original dimensions when
the load is removed. This will occur when the rope is loaded to about
half its breaking strength. Stretch it much further and the fibers will
permanently deform or break. Repeated stretching to this point will
weaken nylon rope and it should be replaced as soon as possible. Nylon
loses about 20% of its ultimate strength when wet. But wet nylon will
handle transient shock loads even better than dry nylon. The water acts
as a lubricant, permitting fibers to slide over each other and
minimizing internal heating and friction.

It is important to remember that the safe working load of a rope is
dependent on its use, not its ultimate strength. The SWL is the
breaking strength of a rope divided by a safety factor, generally from
2 to 12, depending on use. Tasks that involve stretch or overhead loads
in working areas require the highest safety factors. A 3/8" nylon rope
with a breaking strength of 3000 lbs, used in an overhead lifting
situation, might have a SWL of 200 lb. Dacron rope, roughly equivalent
in breaking strength to nylon, might have a SWL of 600 lb. in the same
application because of its lower stretch. The safety factor is
generally determined by lawyers not engineers.

In anchoring situations, where we want stretch to the attenuate
transient shock of wind gusts and waves, a safety factor of 3 or 4
might be appropriate. Thus for a boat with 100 sq. feet of projected
area, an appropriate anchor rode for storm anchor sized to resist a 60
kt. wind would be 1/2" nylon at a minimum. A 5/8" rode might offer a
greater safety margin but would offer less stretch in lighter wind
conditions. Naturally all cleats must be sized and secured to handle
the maximum shock loading expected. Because of gusts and wave action
this may be two to three times the load listed in the wind force table.

After every severe storm, inspect your anchoring system and replace all
the parts which are suspect, particularly line which may have been
overstressed. "An ounce of prevention  - - - etc."

Larry Z

It's a fact, most of the peeps who post on here are male so I want to
ask you a question.

Imagine you're on a long passage, (5 days or more) and food becomes one
of those things that break up the boredom. What, food wise would
brighten your day?

P.

First choice:  Chocolate Candy Bar
Second choice: Chocolate Ice Cream
Third choice: Chocolate Cake
Fourth choice: Chocolate Cream Pie

One selection from each of the four major food groups!

Thom Rose
Oski
Californian 42
Everett, WA

-----Original Message-----
From: trawlers-bounces@lists.trawlering.com [mailto:trawlers-bounces@lists.trawlering.com] On Behalf Of Paige
Sent: Friday, June 01, 2012 12:22 PM
To: trawlers@lists.trawlering.com
Subject: T&T: Food

It's a fact, most of the peeps who post on here are male so I want to ask you a question.

Imagine you're on a long passage, (5 days or more) and food becomes one of those things that break up the boredom. What, food wise would brighten your day?

One of our favorites underway is a nice pasta salad. That and fresh fruit, sliced and made into finger food.  

Joel and Vicki Wilkins
m/s Miss Magoo
Columbia 45
Treasure Island, FL

I think for boats of the forty-foot range (give or take a few feet), one
needs to consider that open water transits of 4-5 days are going to include
sea conditions not altogether conducive to food preparation.  If you are
thinking about the American ICW or European canal cruising, it is simple
enough to eat ashore any time; so back to open water considerations.

Probably the best way to get warm comfort food ready is to make casseroles
and the like (lasagna comes to mind) before departure which can be grabbed
out of the fridge and enough for single servings dished up and slid into the
nuker between big waves.  For those in need of a hearty breakfast, something
along the lines on an egg-Mcmuffin can be prepared ashore or at the pier and
wrapped in aluminum foil and kept refrigerated for a few days.  Pop in the
nuker, and you're good to go.

For the odd day calm enough to cook a meal aboard, nothing tops off the day
like steak or fish.  There is a plethora of bagged, five-minute veggie
dishes out there to quickly add another food group or two to the menu.

A surprise item like a stowed away frozen pie you pop in the oven for an
hour or so can give the cook a real pat on the back when produced at about
the halfway point when ice cream is no longer unique (but NEVER dull), and a
special dinner of, say, pot roast near the end of the run will finish things
nicely.

Rich Gano
Calypso (GB42 Hull # 295)
Panama City area, FL

To top off the evening we usually enjoy a couple of decaf espressos
and biscotti about a couple of hours or so after dinner. Have one of
those neat Italian stove-top espresso makers that will make six cups
(enough for the two of us and a guest, when aboard). We find biscotti
along the way - some of the best came from some small shops in Canada!

One of our favorite meals on cool days is chili fixed in a crock pot
simmered all afternoon as we're cruising, then served with fresh hot
corn bread from the oven! Yum!

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