is 6.3 pounds per 100 feet, so 200 feet is 12. 6
pounds. Total anchor and rode weight is 157.6,
say 160 pounds, and 3× 160 pounds gives a
windlass-pull rating of 480 pounds. We could
safely use any windlass from about 480-pound
pull and up, but more is better, within reason.Or
Total weight of anchor and chain are then
48 kg chain plus 16 kg anchor equal 64 kg.
Twelve-millimeter nylon (from Table 23-12) is
0 .097 kg/m, so 60 m is 5.82 kg. Total anchor
and rode weight is 69.82 kg, say 70 kg, and 3×
70 kg gives a windlass-pull rating of 210 kg
(2 kN). We could safely use any windlass
from about 210 kg or 2 kN pull and up, but
more is better, within reason.
Several windlass would fill the bill. The
Sprint 600 is a vertical unit rated with a
600-pound (272 kg) pull and for^1 / 2 - inch (12 mm)
line and^1 / 4 - inch (7 mm) high-test chain. This
would work. If we wanted to stick with the(^5) / 16 - inch (8.73 mm wire dia.) BBB, we could ask
if a matching chain wildcat was available on
special order, or we could simply switch to the
(^1) / 4 - inch (7 mm) high test. The Maxwell Freedom
500 RC (Figure 24-2) has similar specs, as does
the Simpson-Lawrence Horizon 600G, but in a
horizontal configuration.
If we had an all-chain rode of 300 feet
(90 m) and wanted it to be able to haul our
75-pound (23 kg) Luke storm anchor, we would
need to increase windlass size as follows:
300 ft. 5 / 16 - in. BBB chain @ 110 lb./100 ft. =
330 lb.
75-lb. Luke anchor
Total 375 lb.
3 × 375 lb. =1,125 lb.
A windlass with 1,200 pounds of pull
would do. For an ordinary 32-foot motor-
yacht, this would be overkill, but not if our
Hold Fastwere a globe-girdling voyager.
Or
90 m 8.73 mm wire dia. BBB chain @
1 .6 kg/m =144 kg
23 kg Luke anchor
Total 167 kg
3 × 167 kg =501 kg
A windlass with 500 kg (4.9 kN) of pull would
do. For an ordinary 9.7 meter motoryacht,
this would be overkill, but not if our Hold
Fastwere a globe-girdling voyager.
Windlass Power
Considerations
Electric-powered windlasses draw substan-
tial amperage. This has to be considered
carefully. The Maxwell Freedom 500, for in-
stance, is not a large windlass. Nevertheless,
it draws 600 watts at full power. Since amps =
watts ÷volts, this means that the windlass is
drawing 50 amps at 12 volts (600 watts ÷
12 volts =50 amps). This kind of draw will
flatten a battery bank fast and requires large
electric cables. Assume that the house bat-
tery bank is somewhere aft of midships in the
engine compartment on our 32-foot (9.7 m)
Hold Fast. This means that the length of the
cable run to the windlass (including all
bends—running up and to the side, then for-
ward and back to the windlass on the center-
line) will be about 26 feet (8 m). (This dis-
tance should be measured accurately on the
actual installation or on the boat’s drawings.)
To size wiring for a given amperage, you need
the total length to and fromthe battery, so a
total of 52 feet (16 m).
Some guides allow heavy equipment, like
windlasses and bow thrusters, to experience
a 10 percent voltage drop, but this reduces
performance and increases heat buildup. Bet-
ter to stick with 3 percent allowable voltage
drop where possible.
The size of copper wire in circular mils
for a given length and amperage can be found
from Formula 24-5.
Formula 24-5. Copper Wire Size for a
Given Voltage Drop
or
Where
cm =circular mils
mm^2 =wire-conductor cross-section
area, nominal metric wire size
amps =current in amps
mm
amps length, m
55 .97 allowable voltage d
(^2) = ×
× rrop
cm
10 .75 amps length, ft.
allowable voltage
=
××
ddropPART SEVEN: ANCHORING SYSTEMS
Formula 24-5.