I have also thought about this kind of arrangement for the auxiliary. The idea I
like most is twin keel with saildrive unit between the keels or even faired in
to one of the keels. Twin keels should move the CoE less forward and they would
give great protection for the drive unit. Retractable thruster would of course
be nice but also complex and expensive. Steerable electric saildrive would
provide great manouverability in all conditions, especially if combined with
electric outboard close to ww hull. Would the complexitiy, weight and price of
electric be worth it... well let the boat buyer decide. Inboard and saildrive
would be enough for most situations.

Arto



From: Mike Crawford <jmichael@...>
Subject: Re: [harryproa] Re: sailing BD with leeboard
To: harryproa@...
Date: Monday, November 2, 2009, 5:38 PM


 




  One thing I have debated for a while is going with a propulsion-rated
retractable thruster in the lee hull for the boat's motor.

  On one hand, I realize that this carries a $10,000+ penalty when compared to
outboards, as well as some weight (once you figure in a genset and any
propulsion batteries). 

  On the other, it would have a number of benefits:

  - Convenient collapsing without having to worry about 000 cables, outboards,
or other apparatus.  Everything could be in one hull, with just house power
going to the windward hull.

  - A highly cavitation-resistan t drive system that's unlikely to get beaten up
or swamped by waves or chop.

  - The ability to drive forward or reverse without issues.

  - The option of charging batteries, either propulsion or house, while under
sail.

  - The option of using diesel, or fuel cells in the future, instead of
gasoline.


  But retractable thrusters are expensive, and they likely won't take very well
to grounding or running into logs.

  A mini keel could be a nice way of making sure there's something sturdy to
take impacts that would wipe the  thruster out.  There could be either two
mini-keels in tandem, each with its own foil shape, with the thruster in the
middle, or the keel could be one piece with the thruster angling out to
windward. 

  There would be less need for a keel if the boat had a deeper draft and the
thruster could poke out above the hull bottom on the side, but that's not likely
to happen with a proa that has any reasonable performance.

       - Mike

 
 

rpvdb@ymail. com wrote:
 

Hi,

We sailed BD again with the repaired leeboard.
I fixed it to the lw hull with a Dyna One line through the hull side to the mast
frame. There were a lower and upper guard to keep it in position, at least that
was the intention. It appeared very hard to obtain enuogh tension on the line to
keep the board thightly next to the hull. A bolt would be better.
Results of the sail pretty much confirm the earlier ones.
I asked somebody new to the boat to come along for the test.
When we where less concentrated on sailing the boat (too busy talking)the board
would come off the lower guard and after that it was hard to bear away and the
boat luffed into the wind a couple of times.
Next day I sailed with the board of the foundation owning the boat and
After a while the line connecting the leeboard to the hull broke.
Now they could see with their own eyes the difference between having the
leeboard and not having it. The boat would luff into the wind when steering
higher that a close reach.
For simplicity they prefer a keel as I expected.
The extra hassle of uphauls and downhauls and keeping an eye on the leeboard is
more that they care for.
So I will try to get a keel under the boat before winter really kicks in.
Regards,
Rudolf