If you could build it out of internet posts you would have it done by now.

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On Wed, 6/6/18, StoneTool owly@ttc-cmc.net [harryproa] <harryproa@yahoogroups.com.au> wrote:

Subject: Re: [harryproa] Biplane catamaran
To: harryproa@yahoogroups.com.au
Received: Wednesday, 6 June, 2018, 10:58 AM


 












Mike:

    We all have our "shameful
secrets"......... Mine is a love for
the yawl rig.  That silly little sail sticking aft
has many uses,
far more than most people realize.  One of them of
course being as
an air rudder to balance the boat.   On a Bermuda
rig, one has two
or more sails up much of the time, and multiple
combinations
possible for balance.  On a junk rig you have a
single sail, which
is part of the beauty of the junk....... simplicity. 
The mizzen
on a yawl offers a balancing sail as it is so far
aft.  It can be
used to steer a boat, even with the rudder lifted on
many points
of sail.  Some yawlies actually use them to back the
boat up.   It
is often used to fly a mizzen staysail.

    Imagine the stares I'd get with a 30'
cat, a mast in one hull,
and a mizzen hanging aft on the other   ;-)



    I'm dubious about popping up after a
knockdown........... How
many large HPs have been knocked down?  The weight
being
concentrated in the windward hull, a knockdown seems
highly
improbable.  Does the leeward hull go completely
under?   That
seems unlikely, they look to have lots of
displacement.  
Presumably the occupied windward hull would have to be
lifted
beyond 90 deg, pivoting about the leeward hull. 
I'm sure it's
possible, but it would take pretty extreme conditions,
or pretty
extreme stupidity.   They might be knocked down the
opposite way a
lot more easily... though the wind should not be
coming from that
direction.   I've seen incredible winds, and
seen them do amazing
things.  I've seen 80 mph (not kts) every year
here.  I've seen
really wild stuff under thunderheads, gusts over 100
mph many
times.  I stopped on the highway one day a number of
years ago and
let a tornado cross in front of me in a remote
area.  



    In any case, multihull capsize is almost always
in the heat of
a race........ Pushing way too hard, you round a point
and a
sudden violent gust knocks you over before you can
release the
sheets, or when surfing down wind without some sort of
drogue to
keep you from burying your bows in the wave ahead.  
The very long
hulls on the typical cruising HP make diagonal capsize
unlikely I
would think, and that is the usual capsize mode for
multihulls.

    Personally I would not go to sea for long
passages without
some sort of drogue strategy.   Sea anchor would be
a good thing
to have aboard also...... The ability to just
"park" could be of
real value at times.  



    Structurally, I'm not especially worried
about a mast in one
or both hulls.  The loads are fairly easy to
calculate, and the
location would be right next to the standard mast
beam.  This is
something that many people have done, and is well
documented.  



                           
                               
   
                           
            H.W.





On 06/05/2018 10:39 AM, mcrawf@nuomo.com
[harryproa] wrote:


 


StoneTool,



  The Iriquois 30 with a biplane junk rig
looks
interesting.  It's edging towards as
close as you can get
with a catamaran to the safety/simplicity of a
schooner-rigged harryproa.



  At one point I was smitten by the
Radical Bay 800,
but eventually gave it up because there was no
way to give
it true double bunks, or queens for that
matter, without
making asymmetric hulls.  The same goes for
Cat2fold. 
Great designs, but too much money to consider
sleeping in
a tube if you're sharing a bunk.  And
since I've been
fixated on a trailerable/transportable boat, a
bridge deck
doesn't cut it.





  Reasons I like the schooner harryproa
(feel free to
disagree -- I know you're set on a
cat):



  - Less sail blanketing on some
reaches. 





  - Ability to easily steer/shunt with t
he sails in
any wind strength, even if both kick-up
rudders have
somehow been taken out of commission.



  - Easier to launch into the surf on a
beat of close
reach if you've beached the boat for
maintenance (hulls
meet the waves at the same time, shunting is
more reliable
and safer than coming about if the wind is
light or
heavy).





  - The potential, though no guarantee, of
being able
to pop back up from a knockdown.



  Other than that, the unstayed biplane
catamaran has
many of the benefits of the harryproas.



  One word of caution:  those hulls were
not designed
for the sailing loads of unstayed rigs. 





  I understand junk rigs can be more
lightly loaded
than bermuda rigs, and that the boat has
reinforcements,
but it's still something to consult an
engineer about. 
Those hulls are not very tall, and they we re
not built to
support the full loads of an unstayed mast. 
They even
have small ports directly next to the mast,
and an open
area just aft.





  You could reinforce everything with
enough additional
glass or carbon inside, provided you get the
directions
right, but that would be a lot of work to get
it right on
that particular hull design.





        - Mike


   






















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