Hamilton Jet HJ212, Installation And Service Manual, Page: 21 / 198

Installation and Service Manual
Design Basics
3 - Design Basics
In This Section
Propulsion System Design ..................................................................................................... 3-1
Drive Lines ............................................................................................................................. 3-4
Universal Driveshaft Alignment ............................................................................................. 3-5
Jet Mainshaft Alignment ....................................................................................................... 3-8
Water Offtake ........................................................................................................................ 3-9
Engine Location and Mounting .............................................................................................. 3-10
Dry run kit (optional extra) .................................................................................................... 3-11
Propulsion System Design
Jet unit selection
Jet unit selection is a complex task and C.W.F.Hamilton should be consulted for advice in all cases.
Hull Design
Not all hull shapes are suitable for propulsion by waterjet. Guidelines on suitable hull shapes,
performance and engine matching is provided in the designers manual.
Mono hulled vessel
Aerated water generated by the vessel’s bow wave must not pass directly aft to the jet unit intake(s).

A vee'd bow stem in conjunction with 10degree minimum deadrise angle is recommended.

Mount multiple jet units as close to the keel line as possible (staggering the engines can allow closer
centres).

Planing strakes, keelsons, plank keels and any other hull appendages that may create turbulent water
flow into the jet unit(s) must not be fitted in front of or adjacent to the jet unit intakes. Refer to figure:
Mono hull design on page 3-2.

For speeds over 30knots, monohedron (constant deadrise) hulls without appendages are recommended
for directional stability.

Displacement speed and warped plane (reducing deadrise going aft) hulls may need additional
directional stability. Twin bilge keels are normally sufficient as these do not increase draft or interfere
with water flow into the jet intake.

The jet unit must be immersed with the water line at least up to the underside of the mainshaft (at the
impeller) in order to prime the jet unit when the engine is started.

For applications using multiple jet units, contact C.W.F.Hamilton Ltd for jet unit spacing details.
3-1