I thought the rudder version you had on solitarry, in the photos, where it had a tube sitting across the deck of lw hull was a good one.
Easy to rotate and swing up. Plenty of strength, support. Nothing catching near thd water line.

The only issue i could imagine on some of the ones, is that if it is a liftinb dagger board type then you can't use the practice of sailing in to the beach or across shallows with the tip ov ruddeff scraping along on sand.. This is easy with swing up, but not so easy with lift up vertical sort.

Maybe small point, but camp cruisers may prefer the swing up.

On El camper i had some bungee occy strap in the hold down line so it was safe to bump along bottom with rudder and no damage.
--------------------------------------------
On Thu, 14/3/19, Rob Denney harryproa@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:

Subject: Re: [harryproa] Re:: Flat bottom hulls?
To: harryproa@yahoogroups.com.au
Received: Thursday, 14 March, 2019, 6:29 PM


 









Great thread, keep it up.
A few comments:
Flat bottoms are much
easier to build and repair.  After fairing, fitting and
installing floor bulkheads is the most soul destroying boat
building job.    They also allow lower headroom, if the
hulls are designed right.  The weight and windage
advantages of these outweighs any small difference in wetted
surface/friction drag.  
2
(or three) piece sleeved masts for trailering are no
problem, and not much harder to build than one piece (the
joining sleeve is a cut off piece of one section slit and
glued into the adjacent one.  The important part of the
build is that everything is straight, which is as
easy/difficult for short bits as long.  My telescoping round mast
was probably more work than it was worth (I don't go
under bridges or have to tow my boat, which changes the pros
and cons), but telescoping wings have some potential.  A
couple of weeks ago a client was here and we played with
attaching sails to masts with hoops, which make telescoping
rigs more viable.  The results were promising, he will use
them on his 18m/60' mono.   More exciting is the work
Steinar (he is visiting, the ideas are flowing thick and
fast) and I have been doing on a telescoping wing mast (60%
of the chord) for his boat.  Ordered the sail yesterday for
a short length of 1/4 scale model.  If it works, it has low
sheet loads, little or no twist (ie no vertical sheet loads)
and no boom.   Results and pics next week, maybe.
 
Reefed sails rarely set
as well as unreefed (the sail luff is cut for different mast
bend characteristics ) and the drag of the top mast is
slow.  As Mike says, a bigger issue on a stayed mast than
an unstayed one.     
A
30' cat will weigh near enough the same as a 40'
proa for the same accommodation. The 18m/60' of cat
hulls are shorter than the 20m/70' of proa hulls, but
the proa hulls are lower and narrower.  Therefore the sail
area can be the same, although the proa will have much more
righting moment.  The proa accommodation will be more
usable.     The proa will be quicker to build (easier hull
shapes, only 2 appendages, no unnecessary curves, one simple
mould usable for both hulls/decks), faster, safer and more
comfortable as it is longer and both sails can be seen
without having to turn around.  It will also cost more in a
marina, but it will have a tender big enough that you can
anchor off, motor in and avoid paying altogether.  
  
New Ex 40 drawings are
finished, will be on the web page when Steinar stops
doodling telescoping wings.  ;-).   First one is being
built in Barcelona.  
We have also designed the
latest "best ever" rudder mount after 2 weeks of
discussion, sketches and finger drawings on the beach.  
Simpler, lighter and easily mounted on the inside or the
outside of the hull.  First part of the laminate for an El
test version is curing as I type.    It works for
bidirectional or one way rudder sections (NACA0012).
 
We spent today working on
rudder build methods.  I drew every one I had tried or
heard of in the sand (about 30m of sketches) and we picked
them apart.  Came up with something simple and
quick. 
Had a sail on Kitetik
(15m Solitarry, weighs about 500 kgs/1,100 lbs, plus 3 crew)
yesterday.  25 sqm/260 sq' (20 sq m projected, which is
less than a Tornado cat) leading edge inflatable kite, dirty
bottom, 10-15 knots of breeze, 30C air temp, a beautiful
day.  Top speed 8 knots, pretty poor up wind.  For the
first time, all the systems worked, so we can now move on to
boat improvements and bigger kites, starting with a
converted 28 sq m (28 sq m projected) paraglider. .































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