Rick, et al,

  I think we're talking about two different sets of requirements here.  he dynarigs are extremely good at what they do, but that doesn't mean they're good at everything.

  In Dennis' case, we're talking about a 60' racer/cruiser, a boat that needs to be as safe as possible while cruising, perhaps short-handed, and then moves as quickly as possible while empty.  This combination is something that a harryproa can be uniquely good at.

  For the sake of discussion, let's define the cruising-safety aspects of the boat as follows (Dennis, please feel free to correct me or modify the list):

  - The ability to depower instantly and completely, on any point of sail, by releasing a single sheet.

  - The ability to stay depowered, without intervention, as long as needed to reef or unreef, check a chart, pee, fix a gash in someone's arm, and so forth.  And remain depowered even if the wind changes direction or the boat yaws while drifting.

  - A fail-safe nature for all of the above, in that if the system fails, such as the mainsheet blows, the system goes to neutral and stays at neutral without intervention.

  - The ability to pull in just a touch on the mainsheet to get a just a touch of forward drive, even if there's too much wind for the sail area, and then back off simply by letting of a single sheet (and no other adjustments), going back to auto-depowered.  Such as if the wind unexpectedly picks way up, but you need to get away from an obstacle now, without the luxury of having time to reef.

  - The ability for one person to do all of this, without having had a lot of time to develop a feel for how the rig handles.

---

  The scenario I'd want to handle would be if I'm out with a few other people, a huge squall picks up out of nowhere, the winds increase from 15 knots to 40 knots, we're in an area that doesn't allow for miles of straight-shot sailing, and I'm either off-shift, incapacitated, or knocked overboard. 

  I'd like one person with somewhat minimal experience on the boat to be able to luff, stay luffed, and then reverse or go forward, as needed, without help.  Especially if I need them to pick me up.  I've had guests on multihulls before, who, though adept at sailing monohulls, were worried that they wouldn't be able to get back to the mooring without me.

  40 knots of true wind on sail area meant for 15 knots is scary, even if the sail is a hyper-efficient double-skinned wing, and therefore smaller than a traditional rig.

  A tail on a dynarig would help put it in neutral, but it wouldn't be the foolproof luffing of a more traditional rig, especially since you have to remember to set it -- that would be one thing people would forget in an emergency.  It wold also add one more adjustment on each shunt.  Also, if the tail powerful enough to keep the sail feathered at neutral in 20 knots, it might be adding too much drag or torque when sailing in 40 (or perhaps, the tail would have to be reefed).

---

  The rigs I'd consider would be:

  - Una.  This will definitely feather.  But will also need some hearty tension on the mainsheets.  More than I'd like to bother with.  And it's not a wing sail.

  - Easyrig.  More balanced than the una, but it's still not a wing sail.

  - Swing wing.  Semi-balanced like the easyrig, but with all the benefits of both a wing sail and a junk rig.  It would not be as efficient as a dynarig (no argument there), but it would be much more friendly than the dynarig in the worst-case cruising scenario.

---

  This is not meant to be a swing-wing versus dynarig discussion, by the way.  They are two different rigs with perhaps different purposes.  The dynarig is extremely good at what it does, and I'm grateful we have Todd, his models, and his full-size proas to help us learn about these issues.

  I simply wanted to highlight the importance of a rig that feathers, and fails, to neutral, if you're going to be cruising.

  Dennis, if you haven't yet read the various swing-wing discussions, I'd check out the following posts and their related discussions:

    http://au.groups.yahoo.com/group/harryproa/message/6687 
    (starts with Rudolph and includes the "threaded" view, from January 4 through 12)

    http://au.groups.yahoo.com/group/harryproa/message/7022
    (shorter discussion, just 26 and 27 May)


        - Mike



On 8/24/2010 7:36 PM, Rick Willoughby wrote:

 

Dennis

I doubt you could get much simpler than the arrangement Todd has on the model.  You cannot let go of control in the model but there are ways to overcome that.

From the point of view of weather cocking I expect you could set up a tail wing that would keep the wing at zero lift or adjustable AoA.  Something to think about and test - the tail wing has to shunt across or around the the wing of course during a shunt but it would be as simple as flicking a lever.  The moment on the sail is not large so the tail wing would not be very large.

The same can be done with the rudders.  They will have almost zero moment if connected with a reversing linkage so a small trailing vane off the steering linkage could be used to hold course. 

There are performance advantages in having asymmetric sections.  I don't think many have thought about the range of possibilities with proas.  

Rick

 

On 25/08/2010, at 2:42 AM, Dennis Cox wrote:

 

On a model, it seems clearly superior.  Maybe even on a small day sailer, I can imagine some advantages.  But on a cruiser... I have a big concern.  Maybe I don't understand the concept fully as it applies to the real world and its a non issue, but...

 

The concept saves you from having to reverse during a shunt.  BUT, since its balanced front to aft there is no weather vaning.  You have to actively position it versus letting the wind position it for you and just sinch down the sheet.  Doesn't this mean you actively have to be rotating it with sheets and/or winches WHILE you are shunting?  And if you're in a big wind... there seems to be a big risk of not being right and going over.  Whereas, the Easy Rig... you can just let go of the sheet, totally ignore it while shunting, and pick up the other sheet and pull it in.

 

And what happens when you are in gusty or major wind direction changes?  You'd have to be on top of it all the time.  Also, you could easily get aback while you're waiting for the winch to bring the sail into the proper location.

 

Just my 2 cents worth... or am I missing something?

 

Dennis