DESIGN LOADS
and ATTACHMENTS
Drogue
Design Load
The
design load for each drogue configuration is adjusted for the
displacement of the yacht.
The design load is the ultimate, once in a lifetime, peak transient
load that would be imposed on the drogue in a “worst case”
breaking wave strike. The working load during a severe storm is
about 10 % of this value.
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MONOHULLS
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MULTIHULLS
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Displacement
|
Design
Load
|
|
Displacement
|
Design
Load
|
|
10,000
#
|
8,000 #
|
|
6,000
#
|
10,000
#
|
|
15,000
#
|
10,000
#
|
|
12,000
#
|
12,000
#
|
|
20,000
#
|
13,000
#
|
|
18,000
#
|
14,000
#
|
|
25,000
#
|
16,000
#
|
|
30,000
#
|
19,000
#
|
|
30,000
#
|
19,000
#
|
|
|
|
|
35,000
#
|
22,000
#
|
|
|
|
|
40,000
#
|
25,000
#
|
|
|
|
|
45,000
#
|
27,000
#
|
|
|
|
|
50,000
#
|
30,000
#
|
|
|
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Bridle
Legs
The
design loads for each of the bridle legs are 70% of the drogue
design loads.
Attachments
on the Hull
The
hull attachments for the drogue should be as far outboard and
as far aft as possible.
I have no information on the ultimate strength of a typical sheet
winch installation, and it would be difficult to evaluate each
structure. Unfortunately, a winch is not an ideal structure, since
the load is applied above the deck line and tends to overturn
the winch and pull it out. The optimum attachment for the drogue
is clearly a strap similar to a chainplate, bolted to the hull
at the corners of the transom and extending aft with a shackle.
For a load of 14,000 lbs, a strap ¼ x 2.25 x 18 inches
attached with six 3/8 bolts would provide a conservative design.
A large steel cleat would be acceptable if the deck is thick solid
fiberglass and a steel plate is provided underneath.
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