Robert,

Thanks for the input. I am optimistic about the fore aft rudder
opportunity, but only testing will yet determine response. That
50-70 ft LW hull is a long piece of boat and control in a
crosswind may be difficult. Most marinas I am familiar seem to
be relatively small channels, favoring sport power boats and
mono's of moderate proportions. They will probably gasp in
disbelief if I showed up with a 26ft beam 60 ft long cat.

I don't particularly like the crosswise thruster but seems most
economical to install and compact, thus getting it farther forward
as you recommend. I am not sure which drags more a parallel
thruster or crosswise. Likely a 210lb thruster would be only a 7.5
inch (190mm) opening based upon my calc of wind force
against the hull sillouette. It would only be used for docking or
tight marina handling.

I will be chartering the boat a little, mostly to build the experience
base of likely HP buyers and was trying to keep the dock
handling fairly simple and straightforward. Have to turn the
upwind wheel opposite direction to move the forward rudder to
turn the boat sharply. Of course turn them the same direction to
crab. Prefer not to excite the helmsman with new tools in their
early stages of experience.

The aft (main) motor will be directed at the aft rudder so that
should kick a turn off to a good start. That should be comfortable
maneuvering for a newbie.

I'll have to "thimk" some more on your forward parallel thruster
idea. I had not thought of that option.

I personally kinda like having all that propulsion stuff on the LW
hull as it focuses those purposes in one place and all the
support hardware can be colocated.

I do know Rob will prefer a clean sleek hull when under sail, I
would be damned as the basphemer to poke a crosswise hole
in his nice clean hull. Eh ? Still plan an outboard"ish" electric
drive for main power but it will retract (swing sideways & up)

Regards,

JT
--- In harryproa@..., "Robert"
<cateran1949@y...> wrote:
>
> Good to hear from you. I've had a little bit of experience with
bow
> thrusters on fishing boats. They are bow thrusters and really
need to
> be at the bows to work properly.The best one was one a 20m
purse
> seiner with the bow thruster in a pod attached to the front of the
> bow. There is always the problem of drag having a hole at right
> angles to the boat Unless you have a small thruster running ll
to
> the hull feeding onto the forward rudder- is this what you had in
> mind. My own feelings are that the paired rudder system with a
single
> outboard drive would give enough manoeverability for just
about any
> circumstances. This would be my preference but a paired set
of fixed
> screws that fed onto the rudders would also work. How about
an out
> board for the main propulsion and a small thruster to use
while
> docking .
> Robert
>
>
> -- In harryproa@..., "jjtctaylor"
<jtaylor412@c...>
> wrote:
> >
> > Been so long nearly forgot my password !
> >
> > With the progress so far with Johnnie's boat, the visionarry in
> > latest stage of development, the aux drive has left me with
some
> > questions and possibilities for input from our distinguished
> > forum. Albeit a quiet forum.
> >
> > Outboards is the current plan, a pair of 15 horse honda's
which
> > is a highly reliable 4-stroke. Certainly the most economical
> > choice and most likely to succesfully get it in the water.
> >
> > The question I have,... is there better choices ? Lot's of
history
> > with swamped outboards and propulsion woes with prop out
> > water in sloppy seas. I find the outboard closest to the WW
hull
> > most at risk since it is not really close to the hull itself but
> > suspended part way across the beam due the WW hull
> > expansion. Yes OB's are a workable solution in moderate
seas,
> > and perhaps a little awkward with initial manuevers in close
> > marineas cause the motor is not evenly spaced across the
> > beam, but functional. Rob's & Mark's plan includes 24 hours
of
> > fuel aboard.
> >
> > As food for thought to kick off the discussion I suggest a
single
> > electric drive near the LW hull either as outboard or
extendable
> > from inside the LW hull. Must be kept close to the hull,
> > upstream of the rudder to insure better helm control and the
prop
> > stays in the water. At the other end would be a bow thruster
> > likely just aft of the leading rudder. An electric drive is
> sufficient
> > to replace both outboards (an equivalent 20-25 HP diesel)
and
> > slow speed maneuvering can be deftly handled by the bow
> > thruster.
> >
> > Anybody ever had a bow thruster ? Some issues remain
such
> > as the thruster tube nacell, will it cause excessive drag in a
> > bi-directional shunting kind of mode ? There are retractable
> > options but much more costsly than an electric thruster and 2
> > batteries. (est 210-220 Lb force required)
> >
> > Taking input, preferences, previous experience, or technical
> > saavy !
> >
> > Regards,
> >
> > JT