<<a slow sweeping tack may maintain that critical inertia better than a faster sharper one>>

  That's a good assumption, as well as mostly correct.

  Our Stiletto 27 weighs 1,100 pounds without a motor, so it has very little inertia for its size.  In moderate winds tacking is not a problem if you're accustomed to the boat, but light winds can be a challenge.

  If you try a sharp turn, the rudders scrub off all the speed, and the boat stops partway through the tack.

  If you try a slow, sweeping turn, hull friction stops the boat instead of the rudders, but you get closer to getting across the wind.

  The solution is a turn of continually decreasing radius, like a nautilus.  If you start the tack when hard on the wind (have to completely close-hauled first, before initiating the tack), and then bring the rudders over at an increasing pace as the boat slows down, you can tack without backwinding the jib in 1.5 knots of breeze.  But you have to get everything exact.

  I now backwind the jib anyway.  Partially because I felt no more need to do it the hard way after I'd mastered the technique, but mostly because it cuts down on sail flogging.  I have 2:1 jib sheets, so there's something hard at the clew that wants to slam into the mast if I don't keep some tension on the lines.  It used to have blocks, which I've replaced with low-friction rings, but it's still more pleasant not to have the sail flapping about.

  Instead of 15 seconds of listening to the sail slowly damage itself while everyone with a nautical mile can hear the chaos, I keep it taught until there's enough pressure to flip the sail over, and then haul in the new leeward sheet in about three seconds without any flogging.

  Of course, the technique is a really bad idea if you don't uncleat in time and you're in a lot of wind.

  My current solution is to hold the line -- no cleats involved.  My long-term solution is to get a boat where this isn't going to be an issue.


<<This is where electric drive, which I consider otherwise to be absurd, would  have some value>>

  Instant-on is always nice.

  That said, a schooner-rigged unstayed proa will never refuse to shunt, even in 0.5 knot winds.  It might take a little while, but you'll never have to worry about blowing the tack and then running into those rocks up ahead.

        - Mike

 

    How much of an issue that is depends on hull design & draft............ and of course any rudder deflection causes hull drag......   The rate of speed decay as compared to the rate of rotation would be the issue.     Not having sailed a proa, it appears to me that the wind is working with you when doing a shunt..... In either case you are rotating the same number of degrees, but you have a wind advantage in a shunt, while in a tack you depend on inertia for the duration of the tack.   During a tack the resistance of the hull to rotation will exist regardless.   Drag goes up with the square of the speed, so you may be right........ a slow sweeping tack may maintain that critical inertia better than a faster sharper one.   In any case, a low inertia multihull that must tack would seem to me to be better served by a hull profile that did not create much rotational resistance, depending on boards or rudders for leeway control.   It seems that some folks in catamarans motor through tacks.... if they sail upwind at all rather than motoring.   This is where electric drive, which I consider otherwise to be absurd, would  have some value.

                                                                                                                                                                                                    H.W.

On 3/21/19 8:17 AM, Björn bjornmail@gmail.com [harryproa] wrote:

 

Rotating the boat fast will make the hull ends move sideways though, creating drag and removing speed. I guess that is good for a shunt. But bad for a tack if the boat stops in the middle of it. Which is what happens on small light catamarans if you turn the rudder too fast..

On Thu, Mar 21, 2019 at 2:23 PM StoneTool owly@ttc-cmc.net [harryproa] <harryproa@yahoogroups.com.au> wrote:

 

Doug:

    I own a machine that steers on both ends... or front only.    When both ends steer, the rate of rotation as relates to the distance traveled is doubled.   The same should be true in a boat.  That strikes me as an extremely valuable feature when doing a tack or shunt in narrow confines.... It could be the difference between choosing to tack / shunt or motor....... It could be a life saver in an engineless situation.

                                                                                                                                                                                                    H.W.

On 3/20/19 9:07 PM, Doug Haines doha720@yahoo.co.uk [harryproa] wrote:

 

I will depend how you sail your HP.

Both boards down or one down and one up.

I tend to favour what i have already had working before which was only using rear rudder at a time.

But if able to leave both down all the time and simply fix one in straight position and unfix the other when doing a shunt then this is simpler and less work.

Maybe on a long continuous tack (shunt) may be improved with only one down? Not sure.

The idea of steering with the a front rudder though is not easy to grasp how that works.

Doug

--------------------------------------------
On Thu, 21/3/19, StoneTool owly@ttc-cmc.net [harryproa] <harryproa@yahoogroups.com.au> wrote:

Subject: Re: [harryproa] Re: Flat bottom hulls?
To: harryproa@yahoogroups.com.au
Received: Thursday, 21 March, 2019, 10:34 AM