Subject: Re: [harryproa] Re: mast bouyancy
From: Mike Crawford
Date: 2/7/2006, 6:20 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

<<what if a mast head flotation system could be built that actually enhanced the anti-capsize function while having a positive gain on aerodynamics? Would that get your interest?>>

  Well, only a fool would say "no" to that question.  :-)

  If I were to try to design such a system, I'd ponder the following:

    - Minimal impact in huge gusts.  If one were to get caught in a 60-knot squall (and the sails are reefed), the resistance of anything at the masthead could represent some additional heeling moment, as well as additional stress on the tops of those flexible masts.

    - Minimal heeling moment due to weight at the masthead.

    - Compatibility with the flexible unstayed masts.


  I like the compressed gas system because it represents no aerodynamic profile or drag, but you could argue that it's a complex system that might fail.  A fixed system that just works without any kind of trigger mechanism would likely be more reliable.  And assuming you only need it in extreme emergencies, that's a good time for something to be reliable.

  Assuming the masts rotate freely, you could probably put something up top that works like a foil to create some lift with little drag additional drag, kind of like a fixed sail top.  Is that what you're thinking?

       - Mike



Chris Ostlind wrote:
So, Mike, what if a mast head flotation system could be built that actually enhanced the anti-capsize function while having a positive gain on aerodynamics? Would that get your interest?
 
Chris
----- Original Message -----
From: Mike Crawford
 
I've had conversations with three racer/cruiser open deck catamaran manufacturers about masthead flotation systems.  All three chose to avoid them because the extra windage that high is pretty significant, and also because they wanted to avoid weight at the masthead.

  One manufacturer decided to avoid righting systems altogether, one went with a compressed-gas system that will inflate a bag at the masthead, and one has yet to unveil its new righting system.

  A schooner rig with wing masts would likely offer enough flotation.  I'd still consider a compressed-gas system as well.  Either that or I'd keep an inflatable dinghy ready, as well as a spare halyard, and make sure I had a system to hoist it up the masts when the boat is on its side.

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