Dave Gerr - Boat Mechanical Systems Handbook-How to Design, Install, and Recognize Proper Systems in Boats

PART SEVEN: ANCHORING SYSTEMS

want to use a yachtsman anchor as the working

anchor, use 1.5 times the bower anchor weight

above. Do the same for stockless anchors

for use in hawsepipes, such as the Manson

“kedge anchor” and the G. J. Wortelboer

“D’Hone Special.”

Keep in mind that displacement is in long

tons of 2,240 pounds or metric tons (tonnes)

of 1,000 kg (2,200 pounds). Say our trusty

Hold Fastis 32 feet LOA by 12-foot beam

(9.7 m LOA by 3.65 m beam) and displaces

21,000 pounds (9,530 kg). That’s 9.37 long

tons or 9.5 metric tons. Formula 24-1 says

you should use a 36-pound (16.4 kg) anchor: a

35-pound (16 kg) CQR, Delta, spade type (like

the Rocna or Manson Supreme), or Danforth

Hi-Tensile would fill the bill nicely.

You’ll notice lightweight aluminum anchor

manufacturers’ tables (e.g., Fortress or

Guardian) recommend much less weight.

Referring to the Guardian anchor table

(Table 22-3), we see that Guardian recom-

mends an anchor of just 7 pounds or 3.2 kg

(the G-16) to hold a boat this size. The table

also says, though, that this replaces a 14- to

18-pound (6 to 8 kg) steel anchor. We’ve

specified a 35-pound (16 kg) steel anchor.

Table 22-3 indicates that the G-37, weighing

18 pounds (8.1 kg), replaces a steel anchor

of this weight. This is the lightest I would rec-

ommend for a bower anchor on a boat this

size. This would be the bower anchor of

choice to keep weight to a minimum for per-

formance boats, though again, I personally

prefer and recommend heft.

Returning to Formula 24-1, we can round

out the complement of anchors for a cruis-

ing boat with a second working or bower an-

chor, a lightweight lunch-hook or kedge

(stream anchor), and a storm anchor. Re-

member, it’s best to have two different types

of bower anchors to ensure you have the best

combination for different holding grounds.

Thus, if your primary bower is a 35-pound

delta, a 33-pound (15 kg) Bruce or Claw, or a

spade type around 33 to 38 pounds (15 to

17 kg) would make an ideal second bower.

(You wouldn’t also specify a CQR, as that’s

another plow type like the Delta.)

The Guardian 18-pounder (8.1 kg) would

do nicely for a lunch-hook or stream anchor.

Using a Luke-pattern yachtsman anchor

stowed in the bilge as a storm (street) anchor,

we would find

2. 2 × 36 lb. =79 lb.; a 75 lb. (22.8 kg) Luke

would work well

Or

2. 2 × 16 .4 kg =36 kg; a 75 lb. (22.8 kg) Luke

would work well

An alternative to the Luke for a street

anchor would be a Guardian or Fortress

about equal to a 75- or 80-pound (34 to 37 kg)

steel anchor. This would be the Guardian

G-85, which weighs only 42 pounds (19 kg).

This is physically a big anchor, with a shank

fully 48 inches (122 cm) long. It, too, breaks

down to stow in the bilge until needed.

If you were setting a pair of anchors in

hawsepipes, port and starboard, you would

use a pair of Danforth Hi-Tensiles, each

35 pounds (16 kg). This boat is too small to

use stockless-type anchors in hawsepipes.

Sizing the Rode

Chain Diameter

For Hold Fast, we’ll order a 35-pound (16 kg)

Delta and a 33-pound (15 kg) Rocna. Now we

have to figure out what size chain to use.

Chain size based on anchor weight is calcu-

lated in Formula 24. 2.

Formula 24-2. Recommended Chain Size

BBB or “Proof Coil” Chain Dia., in.

or

BBB or “Proof Coil” Chain Dia., mm

NOTE: BBB chain is not metric, and the

chain wire diameter is larger than the nomi-

nal chain size, so refer to the BBB chain table

(Table 23-2). Convert the diameter in mm

from Formula 24-2 to inches, and read the

nominal size in inches. Then read the BBB

wire diameter in mm from the table. For

“Proof Coil” (Grade 30) chain, the chain di-

ameter from Formula 24-2 is the nominal

chain size. For high test or stainless, find the

=× 3. 305 3 Working Anchor Wgt.,kg

= Working Anchor Wgt.,lb.

3

10

Formula 24-2.