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Read all about
the Dutchman Boom Brake
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Boom Brake Technical Information
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Basic Set Up
The Brake is attached to the boom where
the vang normally attaches. A line is
run from an attachment point at or near
the aft lower chainplates, through the
Brake and back down to a turning block
near the opposite chain plate, and back
to the cockpit. You must be able to
adjust the Brake line tension from the
cockpit. There are two ways to do this.
Either use a line stopper and winch, or
use a block and tackle (low friction, 4
to 1, for the small 250 series, 5 or 6
to 1 for the 500 series, 750 series will
need a winch). Hand tension is NOT
enough. Although it is slightly better
to run the line back to the cockpit on
both sides, it is usually not worth the
extra cost. Normally, the brake line is
run back to the cockpit only on one
side. |
Brake installed behind a rigid vang.
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Brake Line Diameter
Note that different line diameters can
be used in each Brake. larger line sizes
generate more friction. The
specifications provide a good starting
point. Switch to a larger size if the
braking effect is too little, or a
smaller size if it is too much. some
lines will need to be washed to remove
silicone residue from the manufacturing
process. |
Brake attached to a through-bolted bail.
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Locate Deck Attachment Points
Use the following criteria to select the
ideal location for the deck attachment
points:
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1. |
As
far outboards from the mast as
possible. |
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2. |
Within one foot (30cm) fore or
aft (closer is better) of the
aft chain plate. |
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3. |
Clear of walkways, if possible. |
The most common locations, in order of
preference, are:
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A. |
The
aft lower chainplates if they
are set inboards. |
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B. |
A
car on an inboard Genoa track if
it extends to the chainplates. |
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C. |
A
deck-mounted through-bolted pad
eye, or the toerail. |
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D. |
A
pad eye at the corner of the
cabin house, if a high
cabin house with narrow decks,
like on Valients, Pacific
Seacrafts, or Island Packets.
Most boats have several possible
attachment points. Locate
several possibilities, then move
on to locating the boom
attachment point.
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Chain plate Attachments
If using
the aft lower chain plates, you can
directly attach the brake line and
turning block to the chainplate if a
U-Bolt style. Never attach anything to a
toggle or turnbuckle in a way that can
pull it apart. If your chainplate is a
conventional metal strap or bar inserted
through the deck, measure the clevis
pin. Use a shackle that has the same pin
diameter as the clivis pin if your chain
plate is parallel with the centerline of
the boat. If you chain plates run
athwartships, or 90 degrees to the
centerline, use a cast SS eye bolt in
place of the clevis pin. We can supply
these parts.
Locate Boom Attachment Point
The
Brake will be about 1/4 to 1/3 the boom
length back from the mast. More
precisely, the distance from the mast to
the boom attachment point will be about
the same as the distance from the mast
to the deck attachment. Use the existing
boom vang attachment point or bail as a
starting point. If the boat is fitted
with a rigid vang, the Brake normally is
aft of the vang.
Check Line Tension
Set the
boom height to the lowest normal sailing
position and snug up the vang. Locate
the boom on the centerline. Run a
1/8-inch to 1/4-inch line through the
potential boom attachment point. Tie or
tape the block or shackle to the boom if
needed. Then run the line down to the
potential deck attachment points. Snug
up the line and secure it 9with tape if
needed) Now swing the boom out, and
check the tension on the line. The line
tension should not change significantly
as the boom swings through its arc. As a
rough guide, the tension should not
change more than 4 inches for the 250
series, 6 inches for th3 500 series, and
9 inches for the 750 series. The line
should become looser, not tighter, as
the boom moves away from the centerline.
In general, by moving the boom
attachment point back or the deck
attachment point outboards, you will
make the line looser as it moves away
from the centerline. It may take a few
tries to find the best combination. You
may find that, if you have any kind of a
cabinhouse, the Brake line will rub
against it or the handrails at some
point. This is often unavoidable. Bear
in mind that the Brake slides along the
line and the line itself does not move
significantly. The line will not cause
significant chafe. Teak handrails will
need metal chafe guard strips.
Specifications: Brake, Hardware, and
Line
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Brake Model |
250 250B
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500 500B
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750 750B
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Typical Boat Size |
20 - 32' / 6 - 10m |
30 - 45' / 9 - 14m |
42 - 60' / 13 - 19m |
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Max Mainsail Area |
250 sq ft / 23m |
500 sq ft / 45m |
750 sq ft / 68m |
Safe Working Load
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1,600 lbs / 700 kg |
2,700 lbs / 1,200 kg |
4,100 lbs / 1,800 kg |
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Line Specs, Minimum |
1/4" - 36' / 6mm - 11m |
3/8" - 44' / 10mm - 13M |
1/2" - 60' / 13mm - 18m |
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Line Specs, Maximum |
5/16" - 40' / 8mm - 12m |
7/16" - 50' / 11mm - 15m |
5/8" - 75' / 16mm - 23m |
These specifications are for
conventional, moderate displacement
monohulls, and provide a rough
indication of which Brake to use. Heavy
displacement or offshore-intended
sailboats should move up to the next
larger Brake if near the maximum sail
area. The BB250, BB500, and BB750 are
used with rigid vangs, in a soft vang
applications with 2 attachment points
(bails) on the boom, or if there is no
vang. The BB250B, BB500B, and BB750B
have an additional shackle at the bottom
of the Brake. They are used with “soft”
(block and tackle) vangs. The Brake is
attached to the vang bail on the boom.
The vang is shackled to the bottom of
the brake. The Safe Working Loads are
for the respective Brake and any
mounting hardware used to secure the
Brake or run the line back of the
cockpit. Any parts you use should follow
these SWL recommendations.
The Line Specs are given for both the
minimum and maximum size we normally
recommend. Lengths given are normally
enough to run the line form the
chainplate, to the Brake, back down to
the other chainplate, and back to a line
stopper and winch in the cockpit. Add 50
percent to the length if you intend to
run back to the cockpit on both sides.
If your boat is towards the smaller end
of the mainsail area / boat size range,
then you probably will use the minimum
line specs, and if your boat is closer
to the maximum mainsail area / boat
size, use the maximum line size. 7/16” -
11 mm line is often a tight fit with the
500 series. It helps to have a messenger
loop whipped onto the end of the line,
to pull the brake line through. Also,
note that 9/16” line can be used with
750 rake with boats in the middle of the
specs. If the line provides too much
friction, you may need to go down one
line size. Too little friction, go up
one line size. Finally, some lines may
hve silicone residue or other lubricants
remaining from the manufacturing
process. Wash the line with a load of
clothes.
The
Boom Brake Owner’s Manual has more
detailed information about installing
your new Boom Brake, but this should
help you figure out if and how the brake
will work on your boat. And you can
always call us if you have any
questions. |
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