Sleipner SE60 - Tunnel End Design for Performance

10
5693
21 2023
-
SE60/185 s2
MG_0002
R = 0,1 x D (10%)
D


1
2
3
Angled tunnel ends for
steel/ aluminium hulls
Cavitation
MG_0003
High water force
while underway
High water force
while underway
from wave contact
To protect the propeller from water entering into
the tunnel at high speeds (25 knots +) the
extended deflector/ spoiler must provide
protection from the front and the bottom. In the
event when the boat is traveling at high speeds it
will commonly pound upon the water surface.


1 2 3
4
Tunnel Ends
MC_0003
Rounded tunnel ends will maximise thrust and minimise noise and cavitation.
For best performance round the tunnel connection to the hull-side as much as possible. The minimum rounding has a radius of 10% of the diameter of
the tunnel.
Signi cant advantages of a rounded tunnel over a sharp tunnel to hull connections are:
1. A rounded tunnel end will prevent the creation of turbulence/ cavitation created from a sharp tunnel end when water passes by the tunnel.
- The turbulence/ cavitation will block the outer area of the tunnel and thereby reduces the effective tunnel diameter and thrust.
- Turbulence/ cavitation on the propeller will lessen the thrusters performance and create excess noise.
2. For steel/ aluminium hulls angled tunnel ends also offer similar performance as a rounded connection.
3. A rounded tunnel end makes the thruster draw water from along the hull-side, creating a vacuum that will suck the boat sideways and thereby give
additional thrust.
- With a sharp tunnel end, the thruster will be unable to take water from along the hull-side, and you will not gain the desired vacuum and
additional thrust. This “free” extra thrust in optimal installations be 30 - 40% of the total thrust.
(NB: A Sleipner thruster propeller does not produce cavitation at working speed. Therefore, any cavitation and cavitation noise in the tunnel will be
caused during improper tunnel installation.)