Yards Moving Forward - GL Group

PHOTO: VOLVO OCEAN RACE
Will the Rig Hold?
nonstop spoke to the rig expert and naval architect
Hasso Hoffmeister about the current trends. “The development
generally starts at the Grand Prix level, as is so
often the case in sport,” Hoffmeister points out. “PBO and
carbon cables are increasingly also being used for the
superyachts”.
Small wonder: the use of fibre cables saves weight.
Ropes of PBO or carbon fibre weigh only a fifth of what
regular steel shrouds of Nitronic 50 put on the scales – and
all for the same breaking load and stiffness. Weight saved
in the rigging has a direct effect on the stability.
Depending on the type and size of boat, a saving of 100 kg
in the rig weight on a 80 ft yacht permits a reduction in the
ballast of 500 kg or the corresponding decrease in draught.
The cables are available in configurations that are quite
usual for superyachts. Diameters ranging up to that of a
coffee cup and breaking loads of up to 400 tonnes are all
part of the delivery programme.
Rising Demand
What does the cryptic abbreviation PBO mean? “PBO
stands for poly (p-phenylene-2,6-benzobisoxazole), a flameresistant
and high-tensile material which was developed
in the eighties,” explains Hasso Hoffmeister.
The properties of this material meet the stringent
requirements posed by marine sports. “The sustained
interest in standing rigging made of PBO and carbon
fibres was the decisive factor in compiling the new guidelines
for the approval of rig cables of synthetic materials,”
says Hoffmeister. Published recently by Germanischer
Lloyd, the “Guideline for the Type-Approval of Carbon
Strand and PBO Cable Rigging for Sailing Yachts” is setting
a new technical standard for shrouds and stays of artificial
fibres. The new Guideline was developed in close cooperation
with the customers of the classification society,
including mast designers and the manufacturers of PBO
and carbon fibres.
Worldwide, only a handful of companies are able to
produce standing rigging from these high-tensile and
ultralight fibres. However, the market is on the move. Until
now, mast builders usually purchased the standing rigging
YACHT TECHNOLOGY
In cooperation with mast designers and manufacturers of PBO and carbon fibres,
a new guideline on the approval of the standing rigging of fibre cables has been
developed by GL. On regatta yachts like the spectacular Volvo Ocean Racers, shrouds
and stays of PBO or carbon fibre have been used for several years now.
from supply companies. At the same time, they are required
by law to guarantee the integrity of their rigs. “As a
result, there was a real need and request by the mast
designers for guidelines on the approval of tear-proof synthetic
cables,” the rig expert adds.
The guidelines give the manufacturers of synthetic
shrouds and stays an independent verification of the
suitability of their products. A prerequisite for this verification
is that a number of certified loading tests must be
performed on the stays or shrouds. Amongst others, these
include an impact test, a chafe test and a fatigue test.
Test Triathlon Needed
For the impact test, the fibre cable must resist the
damage caused by a falling blade. Since PBO strands are
very sensitive to UV radiation and no light must therefore
be allowed to fall on the material at all, the frictional compatibility
of the plastic jacket is examined by means of the
chafe test. A spinnaker sheet rubbing on the shrouds
generates heat, against which the fibres have to be adequately
protected. The fatigue test scrutinizes the longterm
cyclic loading of the material. The cable is clamped
in a test setup which is used to induce a tensile force corresponding
to the maximum working load of the material.
The cables must withstand up to 100,000 load cycles. At
the end of the fatigue test, the maximum tensile strength
is determined.
How long when have you been concerned with carbon
fibre rigs? Hoffmeister: “For over ten years now, Germanischer
Lloyd has been assessing the construction and
design of carbon fibre masts and is therefore only classification
society that has intensively supported the development
and application of this technology.”
What further developmental steps are likely? For
Hasso Hoffmeister, there is no doubt that standing rigging
of synthetic fibres will soon come into widespread use.
Once again, Germanischer Lloyd is at the forefront with
the corresponding guideline. ■ OM
For further information: Hasso Hoffmeister, Deputy Head of Department,
EU Certification of Recreation Craft and Rigs, Phone +49 40 36149-411,
e-mail: hasso.hoffmeister@gl-group.com
nonstop 3/2006 33