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

Formula 24-6. Recommended
Chain-Locker Volume

Chain-locker volume in cu. ft. =ft. of chain×
(chain size, in.)^2 ÷ 7
or

Chain-locker volume in m^3 =m of chain×

(chain size, mm)^2 ÷48,612

This is the clear volume measured from
18 inches (46 cm) below the bottom of the
spurling pipe down.
Example:Our Hold Fastwould then
require

100 ft.× (^1 / 4 - in. high-test chain)^2 ÷ 7 =

0 .89 cu. ft. for the chain; say, use 1 cubic foot.

Or

30 m× (7 mm high-test chain)^2 ÷48,612 =

0 .03 m^3

Rope-locker volume is calculated by using
the following formula.

Formula 24-7. Recommended
Rope-Locker Volume

Rope-locker volume in cu. ft. =ft. of rope×

(rope dia., in.)^2 ÷ 70

or

Rope-locker volume in m^3 =m of rope×

(rope dia., mm)^2 ÷481,620

This is the clear volume belowthe bottom of
the spurling pipe. (Yale Brait requires only
50 percent of this volume.)
Example:Our Hold Fastwould then
require

200 ft.× (^1 / 2 - in. nylon)^2 ÷ 70 = 0 .71 cu. ft. for

the rope; say use 0.8 cu. ft.

or

60 m× (12 mm nylon)^2 ÷481,620 = 0 .018 m^3

Accordingly, Hold Fast’s total chain and
rope locker should be at least 1.8 cubic feet—
2 cubic feet would be better (0.058 m^3 —0.06 m^3
would be better). The locker ought to be as
high, narrow, and vertical as possible, as well
as directly under the windlass. Again, keep

in mind this volume is only the volume below

18 inches (46 cm) beneath the bottom of the

spurling pipe.

Snubbing Up

One of the things I like about all-chain rode

is the ability to use a stopper to take the load

off the windlass. This should not be done

with a rope anchor warp. Such a snubber on

rope would be another rope fastened with a

rolling hitch, or similar, and these reduce the

strength of the warp they attach to by

50 percent! For chain, there are several stan-

dard metal stoppers available—all the stan-

dard ones work fairly well. You can see

chain stoppers on the foredeck photo of

Imagine(Figure 24-11) and in the drawings

of the 75-foot (23 m) cutter’s arrangement

(Figures 24-18 and 24-19), as well as in the

close-up photo (Figure 24-21). This style of

chain stopper used to be called a box chain

stopper.

On many boats, however, there isn’t

enough room to install chain stoppers. If so,

nylon snubbers can do the job.

Chain-Snubbing

or Anchor Pendant

In all cases, there’s an even better solution to

riding on the chain stoppers at anchor

(though these are recommended and will do

the job adequately). You want to add the

elastic snubbing action of rope to an all-chain

rode. This is done by attaching a nylon-rope

snubber to a cleat on deck, running it through

a hawse or chock at the bow, and fastening it

to the chain with a rolling hitch or chain claw.

The chain is slacked away so the load comes

on the nylon snubber. Note that when the

nylon snubber is run through a hawse or

chock on deck, it should be protected with

chafe gear at the chock for any long-term

anchoring.

Anchor Pendant or Snubber

to Bow Eye

My favorite solution, and one that beats a

standard chain stopper hands down, is to use

an anchor pendant (pronounced pennant)

Chapter 24: Sizing the Anchor and Rode and Selecting Anchor-Handling Gear

Formula 24-6.

Formula 24-7.