H68.0.02.6C-04
Operating Manual GMK 210
page 14 of 20
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10 Rating of GRP boat hulls
10.1 Design principle of GRP hulls
The load-bearing material of GRP boats is
G
lass-fiber
R
einforced
P
lastic. This plastic is extremely robust,
but water can entry to the laminate structure due to
osmotic and capillary effects and damage it
permanently: The material gets deformed and
unstable.
A
gel coat
layer protects the GRP laminate from water
entering.
Antifouling:
Paint coat protecting against growth of
algae/bivalves etc.
If water has entered the GRP structure it can be measures very easily nondestructively measured
with the GMK 110 without any further tools.
The device detects water inside the GRP structure by means of a capacitive measuring principle.
Water has a relatively high permittivity. Examples for different permittivity values:
Vacuum/air
1
Polyester- and Epoxy resin
~ 3...4
Glass-fiber
~6...7
Water
~80
ATTENTION:
Structures containing carbon fibers or structures with metallic/graphitic coatings.
Metallic elements will also cause increased display values.
10.2 Procedure
Recommended settings:
- Measuring mode,
characteristic “GrP”, %u, measuring depth 25mm.
-
or detector mode “dEt” %u, measuring depth 25mm ( refer to chapter 6.2)
NOTE:
Sometimes a wood characteristic (e.g. d.50) is used. Although this is not generally
senseless, you have to keep in mind that in this case the displayed values (in %) can
only serve as comparative values but not as absolute values.
The electric properties used by the device for measurement are different for wood and
GRP! Remember this problematic especially if you want to compare values of different
devices!
The surface of the hull must me dry for
measurement. Humidity on surface will cause
unrealistic high display values!
Additionally wait at least 2 days after the boat has
lifted out of water before starting a measurement:
the antifouling can contain a large amount of water
without causing any damage, but the measurement
would be falsified.
boat hull
G
R
P
Ou
tsid
e
