7
EB 20/110 S - EB 40/160 S - EB 60/160 S - EB 75/185 S - EB 90/185 S
1.0.6 - 2014
Tunnelåpninger
N
Avrundede åpninger vil minke støy, og maksimere effekt.
Vi anbefaler å avrunde tunnelåpningene mest mulig.
Den optimale avrundingen har en radie som er 10% av tunnelens diam-
eter.
Hvorfor er en avrundet tunnelåpning så viktig?
1. En avrundet tunnelåpning vil forhindre at det oppstår turbulens / kavi-
tasjon, noe som vil oppstå ved en installasjon med skarpe kanter.
Turbulensen forårsaker mer støy, og begrenser skyvekraften.
- Turbulensen / kavitasjonen blokkerer tunnelen og svekker skyvekraf-
ten.
- I det kavitasjon og turbulens når propellen påvirkes ytelsen til denne
og øker støyen.
2. En avrundet tunnelåpning gjør også at thrusteren suger vann langs
skroget på båten. Dermed oppstår det et lavtrykk som vil hjelpe å suge
båten i dreieretningen. Med skarpe åpninger klarer ikke thrusteren å
suge vann langs skroget, og lavtrykket uteblir. Så mye som 40% av
skyvekraften har blitt målt til å ligge her på noen installasjoner.
NB! Propellene til Sidepower thrustere kaviterer ikke på arbeids-has-
tighet, så kavitasjon og støy som oppstår som følge av kavitasjon,
skapes av tunnel installasjonen.
NB! Selv der en perfekt avrunding ikke er mulig er det viktig å runde av
kantene så mye som mulig, en tunnelåpning med skråkant vil ha
stor effekt fremfor en med skarpkant (se side 10, ill. 1b & 1d).
Tunnel ends
GB
Rounded tunnel ends will maximize thrust and minimize noise.
We recommend rounding the tunnel connection to the hull-side as
much as possible.
The optimum rounding has a radius of 10% of the tunnels diameter.
Important advantages over sharp tunnel to hull connections are:
1. The rounded tunnel end will prevent creation of turbulence
cavitation that will come from a sharp tunnel end when water
passes by fast, thereby preventing a double negative impact on
the thrust and noise level (Fig. 1 & 2).
- The turbulence / cavitation blocks the outer area of the tunnel
and thereby reduces the effective tunnel diameter and thrust.
- The turbulence / cavitation hits the propeller and thereby reduce
the propellers performance and creates noise.
2. The curved tunnel end makes the thruster take water also from
along the hull-side, creating a vacuum that will suck the boat
sideways and thereby give additional thrust (Fig. 3 & 4).
With a sharp tunnel end, the thruster will be unable to take water
from along the hull-side, and you will not get the desired vacuum
and additional thrust. This “free” additional thrust can in optimal
installations be as much as 30 - 40% of the total thrust.
NB! A Sidepower thruster propeller does not cavitate at working
speed so that all cavitation and cavitation noise in the tunnel will
be caused by the tunnel installation.
NB! Even if it is not possible to make the perfect rounding, it is very
important to round the tunnel end as much as possible. A
angled tunnel to hull connection will also do much of the same
job as a rounded connection (see page 10, Fig. 1b & 1d).
12
SP 75 Ti / SP 95 Ti / SP 125 Ti
2.5.1- 2007
Formgebung der Tunnelenden
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Abgerundete Tunnelenden erhöhen die Schubkraft und
reduzieren das Geräuschniveau.
Der Bereich Tunnelende / Außenseite des Rumpfes ist soweit
möglich abzurunden. Der optimale Wert für den Radius dieser
Rundung beträgt 10% des Tunneldurchmessers.
Vorteile gegenüber einer scharfen Tunnel / Rumpfverbindung sind:
1. Abgerundete Tunnelenden verhindern Turbulenzen / Kavitation,
wie sie an scharfenkantigen Tunnelenden auftreten. Damit
werden zwei negative Auswirkungen auf Schubkraft und
Geräuschentwicklung vermieden (Fig. 1 & 2).
- Turbulenz / Kavitation blockieren den äußeren Tunnelbereich.
Dadurch werden effektiver Tunneldurchmesser und Schub-
kraft reduziert.
- Die Turbulenz / Kavitation trifft auf den Propeller und reduziert
dessen Effektivität und führt zu zusätzl. Geräuschentwicklung.
2. Abrundungen ermöglichen, daß Wasser entlang der Rumpf-
außenseite angesaugt werden kann. Dadurch entsteht ein
Vakuum ("zusätzliche" Schubkraft"), das das Schiff seitwärts
bewegt (Fig. 3 & 4). Bei scharfkantigen Enden kann kein
Wasser entlang der Rumpfaußenseite angesaugt werden,
wodurch das benötigte Vakuum nicht zustande kommt.
Diese Schubkraft kann bei optimaler Installation bis zu 30-40%
der absoluten Schubkraft betragen.
NB ! Sidepower Propeller sind so ausgelegt, daß sie nicht
kavitieren, sodaß die Geräuschentwicklung aufgrund von
Kavitation durch die Tunnelinstallation bedingt ist.
NB ! Ist eine optimale Abrundung nicht möglich, so sind die
Tunnelenden soweit möglich abzurunden. Angeschrägte
Tunnel / Rumpfverbindungen sind zu einem gewissen Grad
ebenfalls mit ähnlich positiven Auswirkungen wie eine
Abrundung verbunden (siehe Seite 20, Fig. 1b & 1d).
Tunnel ends
Fig. 2
Fig. 4
Fig. 1
Fig. 3
GB
D
R = 0,1 x D (10%)
R = 0,1 x D (10%)
D
Rounded tunnel ends will maximize thrust and minimize
noise.
We recommend rounding the tunnel connection to the hull-side as
much as possible.
The optimum rounding has a radius of 10% of the tunnels diameter.
Important advantages over sharp tunnel to hull connections are:
1. The rounded tunnel end will prevent creation of turbulence
cavitation that will come from a sharp tunnel end when water
passes by fast, thereby preventing a double negative impact on
the thrust and noise level (Fig. 1 & 2).
- The turbulence / cavitation blocks the outer area of the tunnel
and thereby reduces the effective tunnel diameter and thrust.
- The turbulence / cavitation hits the propeller and thereby reduce
the propellers performance and creates noise.
2. The curved tunnel end makes the thruster take water also from
along the hull-side, creating a vacuum that will suck the boat
sideways and thereby give additional thrust (Fig. 3 & 4).
With a sharp tunnel end, the thruster will be unable to take water
from along the hull-side, and you will not get the desired vacuum
and additional thrust. This “free” additional thrust can in optimal
installations be as much as 30 - 40% of the total thrust.
NB! A Sidepower thruster propeller does not cavitate at working
speed so that all cavitation and cavitation noise in the tunnel will
be caused by the tunnel installation.
NB! Even if it is not possible to make the perfect rounding, it is very
important to round the tunnel end as much as possible. A
angled tunnel to hull connection will also do much of the same
job as a rounded connection (see page 20, Fig. 1b & 1d).
