2.2.1 A requirement of good design in that a system
has reserve strength beyond that required to withstand anticipated
loadings. The reserve strength in free-fall lifeboats is demonstrated
by launching the lifeboat from a height greater than that for which
it is to be certified. As such, this test is often referred to as
the overheight test. The lifeboat will probably never experience a
launch from this height during its service life. The purpose of the
test is to demonstrate that the lifeboat has some reserve strength
so that it can survive unexpected events. The actual reserve strength
should be higher than that demonstrated.
2.2.2 During this test, the primary structural
and watertight components of the boat should not be rendered ineffective.
The test should be considered successful if the structural and watertight
integrity of the lifeboat is maintained regardless of any cracks and
delamination that may have occurred as a result of the test. The lifeboat
does not need to be in such a condition that it can be launched again
but it must still be able to serve as an effective lifesaving appliance.
In this regard there are two issues. First, what are the primary structural
and watertight components? Second, how much damage can be tolerated?
These issues are best addressed separately.
2.2.3 Because there is much variation in lifeboats
produced by different manufacturers, each boat must be evaluated separately
to determine which components are the primary structural components.
As a minimum, the primary structural components are the outer hull
and canopy. The inner liners could be primary structural components
if they were designed to work with the hull and canopy to resist load.
The watertight components are the hatches, windows, and other closures.
These components keep water and weather out of the lifeboat during
operations.
2.2.4 Although it is always desirable that the
lifeboat is not damaged during the reserve strength test, the occurrence
of damage is not necessarily cause to reject the lifeboat. The amount
of damage permitted will always be a subjective issue. In general,
though, cracking of the gel coat during the reserve strength test
is not serious, especially if the cracks do not penetrate the underlying
material. At corners and sharp contours, the gel coat will almost
always show some signs of cracking. These cracks are caused by the
natural flexibility of the boat and are only cosmetic; it is virtually
impossible to prevent these cracks from occurring.
2.2.5 Cracks which penetrate beyond the gel coat
or delamination of the hull and canopy may be indicative of more serious
problems. Such cracks and delaminations are often observed at corners
and sharp contours. Cracks and delaminations that do not provide a
path for water ingress, and do not render the lifeboat ineffective
as a lifesaving appliance, probably are acceptable because there is
no requirement that the boat be in such a condition that it can be
launched again. It is only required that the boat continue to be a
usable lifesaving appliance. However, if the cracks and delamination
are extensive, some remedial action may be required.