NAVAL ARCHITECTURE
NA4 Ships Vibrations Test Model
NA8 Ships Stability Apparatus - Issue 5
The NA4-10 Ships Vibrations Test Model apparatus is designed to enable students to investigate a simple model hull form for resonance phenomena. It may be used in conjunction with the optional fresh water tank or any suitable tank which may be available. Many of the principal phenomena associated with ship resonant vibration are clearly demonstrated.
At a more advanced level the distribution of mass and second moment of area may be calculated and using a Young's Modulus value for the material of the ship shaped beam, the natural frequencies may be estimated by a simple tabular method or other means and compared with the measured value.
Right: NA8-10 shown with NA8-14 trawler model
The NA8-10 Ships Stability Apparatus
is designed for the study of ship hydrostatics and stability. A comprehensive
manual provides hydrostatic stability and other data for ship models. Also
information for a course of practical study in ship hydrostatics, flooding
and stability and describes a number of experiments which are useful to
students.
Exercises are conducted on a 1 /70 scale model of a vessel of 28000 tonnes ship mass. Rolling, righting and the effects of flooding various compartments may be studied.
Optional alternative ships models are also available for study.
ORDERING SPECIFICATION
Ordering Specification NA4
Apparatus designed to enable students to investigate a simple model hull form for resonance phenomena.
The apparatus comprises an experimental model hull, a rigid supporting
frame, a vibrator (complete with signal generator and power amplifier)
and an optional Flotation Tank (order code NA4-11).
The experimental model is flat bottomed, wall-sided and open topped. It
has an elliptical plan form.
- Length to beam ratio 8:1
- Length to depth ratio of 12:1
Used to demonstrate the principle phenomena associated with ship resonant
vibration.
Can be used to investigate resonance phenomena in both air and water.
Ordering Specification NA8
Apparatus designed to enable students to study ship hydrostatics and stability.
Supply includes a water tank, a floating ship model, a dynamometer and
a clinometer.
The model supplied is a 1/70 scale model of a 28000 tonne general cargo
vessel.
- It includes a number of transverse watertight bulkheads in representation
positions.
- The compartments are fitted with individual flooding valves.
- The model is constructed of glass reinforced plastic (GRP).
- Models of other ships are available as optional accessories.
The dynamometer measures the righting moment of the model.
- It holds the model at any angle of heel within the range, with the model
either free to trim or with heeling axis kept horizontal.
- It exerts no vertical force on the model.
- It is floor standing, with castors and is supplied complete with counterweights.
Battery powered clinometer measures the inclination of the model, over
the range of 0 to 45 degrees.
Demonstration Capabilities
NA4
In air to:-
> Investigate model characteristics of a simple suspended ship shaped box girder
> Produce a resonance curve .Produce the amplitude curve of a 2-node and 3-node
flexural model
> Illustrate the influence of mass and its distribution upon natural flexural
frequencies
In water to:-
> Measure the influence of added virtual mass on natural frequency
> Illustrate the effect of the addition and distribution of sand ballast on the
natural frequency
> Calculate the added virtual mass by different methods and compare with experimentally
measured influence using a Schlick-type formula
NA8
> Inclining experiment
> Influence of a free surface
> Influence of a suspended mass, especially with the crane ship model
> Effect of flooding various compartments
> Rolling experiments
OPTIONAL ACCESSORIES
NA4
NA4-11 Flotation Tank for NA4-10
NA8
NA8-14 Trawler Model: A 1 /25 scale model of an ocean going trawler of 850 tonnes ship mass constructed in glass reinforced plastic (GRP). The hull is fitted with a number of transverse watertight bulkheads in their correct positions. Flooding valves are fitted.
NA8-15 Crane Ship Model: A 1 /50 scale model of a crane ship typical of those used in off-shore industries. The hull is ballasted and fitted with a moveable derrick supplied with a number of masses for suspension.
NA8-16 Rectangular Barge Model: Moulded in GRP, dimensions 2200x400x250mm and fitted with internal bulkheads, supplied with the necessary ballast and trimming weights.
requirements
Electricity supply:
NA4-10-A: 220V-240V/1PH/50Hz
NA4-10-B: 120V/1PH/60Hz
Free water surface, if NA4-11 Fresh Water Tank not ordered
Shipping specification
NA4-10 only
Volume: 1.0m3
Gross weight: 120Kg
Overall dimensions
NA4-10 only
Height: 1.44m
Width: 2.66m
Depth: 1.17m
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