Hamilton Jet HJ241, Manual

Page: 38 / 202

3.4
3 DESIGN BASICS
3.2 H
ULL
D
ESIGN
HJ-241 / HSRX
3.2.2 Mono Hulled Vessel
1. Aerated water generated by the vessel’s bow
wave must not pass directly aft to the Jet Unit
Intake(s).
a) A vee'd bow stem in conjunction with 10º
minimum deadrise angle is recommended.
b) Mount multiple Jet Units as close to the keel
line as possible ("Staggered" engines can
allow closer centres).
c) Planning strakes, keelsons, "plank keels" and
any other appendage causing turbulent flow
into the Jet Unit(s) must be removed from in
front of and closer to the keel than the Jet Unit
Intakes. Recommended strakes are shown in
the following diagram.
2. For speeds over 30 knots, monohedron (constant
deadrise) hulls are recommended for directional
stability without appendages.
3. Displacement speed and warped plane (reducing
deadrise going aft) hulls may need additional
directional stability. Twin "bilge keels" are
normally sufficient. These do not increase draft
or interfere with water flow into the Jet Intake.
4. Immersion. The Jet must be immersed with the
water line at least up to the underside of the
Mainshaft (at the Impeller) in order to prime
(pump water) when the engine is started.
5. Minimum distances between Jets for multiple
installations. Refer to Figure 11: Installation for
Multiple Jets.
a) For dimensions A and B shown in Figure 11:
Installation for Multiple Jets for Twin and Tri-
ple Jet Installations, refer to the Installations
Drawings shown in
Section 5 Installation” of
this manual.
b) For applications using more than three Jets,
consult C.W.F. Hamilton & Co Ltd for
recommended distances between Jets.
Figure 10: Mono Hull Design Recommendations