The basic VS invention was in 1928, so the base patent is long gone. While
VS may have built a patent forest around the base tree to prolong the life
of its patent monopoly, this is probably far enough away from 5,000hp tugs
that it's outside the forest.

It does raise interesting possibilities. We are using hydraulics to drive a
bow thruster and a get home chain drive to the screw, both 60hp. This might
do it with one unit, and, if you put it in the middle of the boat, give you
the dockside maneuverability that you get only with bow and stern thrusters.



--
Jim Woodward
www.mvFintry.com


...
"Evan Gatehouse" wrote in message
...

"Glenn Ashmore" wrote in message
news:JDPqb.10756$62.1728@lakeread04...
I don't think it is quite ready for prime time yet but here is an
interesting idea. A small retractable Voith-Schneider drive like those
used on modern tugs. Retracts flat into the hull and when extended will
deliver thrust in any direction. http://www.spw-gmbh.de/en/hb/

Wow. I'm not a great fan of VS drives ('cause they have lower efficiency
than ducted props) and they are hideously expensive. I'm surprised he has
got around the VS patents!

The new Volvo 70 rule allows for retractable propulsion systems - using a
Volvo engine and shaft drive. Not sure how designers will make this work
but it will be interesting to see if can trickle down to more mainstream
designs. Now I want to sit down with a sketch pad and start thinking
about
this!!


--
Evan Gatehouse

you'll have to rewrite my email address to get to me
ceilydh AT 3web dot net
(fools the spammers)