Re: [Amel Yacht Owners] Re: Slowing down in increasing winds


James Alton
 

Bill,

   Your comment about a real preventer needing to run to the end of a boom raises some interesting questions.  Namely what are some factors that determine the shock loading that the boom and the rig receives in an uncontrolled gybe?  Here a a few things that I believe are significant:

1.  The elasticity of the mainsheet.  A modern super low stretch fiber as opposed to using conventional Dacron for instance will greatly increase the shock load.   

2.  Because our mainsheet attaches to the bottom of the boom and the mass of the boom is I assume above the centreline of the boom with the sail attached, the ability of the boom to rotate longitudinally should absorb some of the shock since that rotation would occur in opposition to the membrane of the sail.  A fixed/ non rotating gooseneck on the other hand would receive a large torsional load by comparison.   I would very much be interested in your input on the rotating gooseneck design of our boats because I had not thought much about it until this discussion came up,  but I am starting to like it.   

I would like to add that compared to what I am used to on other boats, the weldements on the boom for the attachment of the mainsheet seem to be incredibly strong.  The boom itself also seems to be a heavier extrusion than what I would expect for a boat the size of mine.   Being a Ketch of course shortens both the main and the mizzen booms and thereby reduces the risks of a jibe causing damage.  While all measures to prevent an accidental jibe are important,  it seems to me that Amel may have done a lot to help reduce the risk of damage to the rig due to an uncontrolled gybe.  

Does anyone know of an instance where the main or mizzen boom or rig of a SM,  SN or Maramu was damaged in an uncontrolled gybe?   That could be an interesting data point given the Ocean miles that some of these boats have accumulated over the years.

Thanks!

James
SV Sueño
Maramu #220


On May 29, 2018, at 10:57 PM, greatketch@... [amelyachtowners] <amelyachtowners@...> wrote:

It is important to remember that the Amel tackles are vangs to pull the boom down and control sail shape, and are really very poorly set up to function as preventers--no matter what Amel calls them.


Anytime the boom is further outboard of the end of the traveler, we tension the vang to control sail shape and keep leech tension up and reduce excessive twist.  The boat goes faster with the whole sail, top to bottom, trimmed to a proper angle to the wind

In strong winds and rough seas counting on a line connected to the middle of the boom to stop an accidental gybe is a very bad idea.  Never on an Amel, but on other boats, I have seen lines rigged that way cause the boom to fold in half in an accidental gybe, or when a deep roll caused the end of the boom to dip into a wave.  That ruins your whole day.

A REAL preventer is attached at the outboard END of the boom and lead forward, then af t to the cockpit so it can be eased--under control--if needed.  

We never sail wing-on-wing on Harmonie.  If we are going downwind, the ballooner is set. If we are not going downwind long enough to justify the effort of the ballooner, we reach at 150 degrees to the true wind and then we make better VMG downwind than we would wing-on-wing.  If we really need to sail straight downwind a short distance for some reason, I furl the main and go jib-n-jigger. We might lose a little speed, but for a short distance, the peace of mind is more than worth it to me.

I personally would never sail wing-on-wing with the main boom anything other than fully out to the shrouds.  An accidental gybe happens when the boom crosses the wind.  If the boom is not all the way out--as far as it can go--you make an accidental gybe that much more likely.  It is not worth it.

The number of boats I have seen seriously damaged by an accidental gybe has taught me to avoid them at all cost.

Bill Kinney
SM160, Harmonie
Norfolk, VA, USA



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