7
SEP 80/185 T - SEP 100/185 T - SEP 130/250T
1.0.0- 2010
Motstand forårsaket av tunnel
Prevent drag from tunnel
N
Et mulig problem for seilbåter eller meget hurtiggående båter er motstand
i tunnelen. Aktre ende på tunnelen vil være en liten loddrett flate mot
vannstrømmen som skaper uønsket motstand.
Denne flaten kan også forårsake problemer med at vann føres inn i tun-
nelen under seilas, eller kjøring i høy fart og får da propellen til å rotere,
dette skaper uønsket støy.
Det er to mulige løsninger på problemet, avhengig av hva som er enklest
å få til på båten.
1. Den løsningen som vanligvis reduserer motstanden mest er å lage
en fordypning i skroget i aktre ende av tunnelåpningen. Den loddrette
flaten vil da forsvinne og dermed motstanden. Hovedregelen å følge
er at bakkanten av tunnelen ikke skal synes når man står rett foran
båten og ser akterover langs båten senterlinje. Dybden, utformingen
og vinkling av fordypningen avhenger av båttypen, og hvordan vannet
følger skroget, men de fleste båter vil være tjent en fordypning som
vinkler lett nedover (Fig. 2).
2. Motstanden vil også reduseres av en spoiler i forkant av tunnelen.
Spoileren fører det meste av vannstrømmen rundt og forbi tunnelen.
Størrelsen og utformingen på spoileren avhenger av båten. Hove-
dregelen er at bakkanten av tunnelen ikke skal synes når man står
rett foran båten og ser akterover langs båten senterlinje. Den enkleste
måten å lage spoileren på er å la tunnelen stikke ut i forkant av tunne-
len, og forme spoileren opp mot den (Fig. 3).
Det er alltid viktig å avrunde tunnelåpningene mest mulig for å motvirke
støy og for å få mest mulig effekt av thrusteren.
Mer informasjon om dette på side 10.
GB
A possible problem in sailboats or fast powerboats is that they get a
drag from the back face of the tunnel, as this becomes a “flat” area
facing the water flow (Fig. 1).
This can also create problems with the thruster spinning (passive)
and making noise while sailing or driving the boat with water being
pushed through the tunnel at high speed.
This can be solved in two different ways, depending on what is
possible or easier to do.
1. The best solution which normally reduces the drag most is to make
a recess in the hull at the back of the tunnel. Thereby the back face
is gone and about all the drag (Fig. 2). The depth and shape of this
recess will depend on the boat. Basically you should not see the back
face of the tunnel when standing directly in front of the tunnel at the
angle of the boats centreline. The angle up or down backwards of the
insert in the hull, depends on the hull shape, but normally it is angled
slightly down because of the water flow on this area of the hull.
2. The drag will also be reduced a lot, especially in fast power boats, by
making a deflector / spoiler in front of the tunnel. This will push the
water flow out from the hull so that most of it passes by the back face
of the tunnel (Fig. 3).
The shape and size of this deflector will depend on the hull shape.
Basically you should not see the back face of the tunnel when standing
directly in front of the tunnel at the angle of the boats centreline. The
easiest way of making this is to let a part of the tunnel stick out in the
lower forward area of the hole, and use this as a support to mould a
soft curve/spoiler shape.
Remember to still round the tunnel ends as much as possible to get
optimum thruster performance and minimum noise. For more
information on how to practically do this see page 10.
14
SP 75 Ti / SP 95 Ti / SP 125 Ti
2.5.1- 2007
Segelboote und sehr schnelle Booten können gelegentlich durch
auf die rückseitige Fläche des Tunnels auftreffendes Wasser
gebremst werden (Fig. 1).
Dies kann dazu führen, daß sich der Thruster durch den perma-
nenten Wasserdurchfluß hörbar passiv zu drehen beginnt.
Das Problem kann je nach Möglichkeit auf zwei Arten beseitigt
werden.
1. Der störende Effekt wird am deutlichsten reduziert, indem man
im Rumpfbereich hinter dem Tunnel eine Aussparung vornimmt.
Dadurch werden Auftreffläche und störender Effekt eliminiert
(Fig. 2).
Tiefe und Form dieser Aussparung hängen vom Boot ab.
Die Innenseite des Tunnels sollte von vorne prinzipiell nicht
sichtbar sein.
Der mögliche Winkel der Aussparung hängt meist von der
Rumpfform ab. Bedingt durch die Wasserströmung in diesem
Bereich sollte dieser Winkel leicht nach unten gerichtet sein.
2. Der Geschwindigkeitsverlust kann speziell bei schnellen Booten
durch einen Abweiser bzw. Spoiler vor dem Tunnel deutlich
reduziert werden.
Das Wasser wird so beeinflußt, daß es größtenteils an der
frontalen Fläche vorbei geleitet wird (Fig. 3).
Form und Größe des Abweisers hängen von der Rumpfform ab.
Prinzipiell sollte auch hier die Innenseite des Tunnels von vorne
nicht sichtbar, sondern durch den Abweiser verdeckt sein.
Dieser läßt sich einfach realisieren, indem man den Tunnel ein
Stück aus dem Rumpf herausstehen läßt und darauf einen
geschwungenen Abweiser / Spoiler formt.
Die Tunnelenden sind zur vollen Leistung und minimalen
Geräuschentwicklung des Thrusters weitgehend abzurunden.
Weitere Informationen siehe Seite 20.
Optimaler Strömungsverlauf am Rumpf
D
Prevent drag from tunnel
GB
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A possible problem in sailboats or fast powerboats is that they get a
drag from the back face of the tunnel, as this becomes a “flat” area
facing the water flow (Fig. 1).
This can also create problems with the thruster spinning (passive)
and making noise while sailing or driving the boat with water being
pushed through the tunnel at high speed.
This can be solved in two different ways, depending on what is
possible or easier to do.
1. The best solution which normally reduces the drag most is to
make a recess in the hull at the back of the tunnel. Thereby the
back face is gone and about all the drag (Fig. 2). The depth and
shape of this recess will depend on the boat. Basically you
should not see the back face of the tunnel when standing directly
in front of the tunnel at the angle of the boats centreline. The
angle up or down backwards of the insert in the hull, depends on
the hull shape, but normally it is angled slightly down because of
the water flow on this area of the hull.
2. The drag will also be reduced a lot, especially in fast power
boats, by making a deflector / spoiler in front of the tunnel. This
will push the water flow out from the hull so that most of it passes
by the back face of the tunnel (Fig. 3).
The shape and size of this deflector will depend on the hull
shape. Basically you should not see the back face of the tunnel
when standing directly in front of the tunnel at the angle of the
boats centreline. The easiest way of making this is to let a part of
the tunnel stick out in the lower forward area of the hole, and use
this as a support to mould a soft curve/spoiler shape.
Remember to still round the tunnel ends as much as possible to get
optimum thruster performance and minimum noise. For more
information on how to practically do this see page 20.
