I read in the latest mutlihull world (the Aistralian version) that in
the races the newer bows actually had fewer pitchpoles than the
previous versions of the Nacra. If total volume of the bows is the
same then one would suspect this. Earlier bouyancy and less drag once
the bows are under. For Xkg depression of bow the fatter bow with
less height will depress less. When it is depressed to just burying
itself, the drag diminishes as underwater the optimum shape is more
cylindrical,and wave drag diminishes and the boat is still travelling
fairly flat. For the taller bows the bows have depressed more to the
point where the whole boat is pointing down. There is much greater
depth of forefoot in the water, greater surface area and the transoms
are starting to lift. There is greater drag on the taller bows. I
can't see that the crews' ability to get aft is any different between
the different types of bows. The way I see it, is that if you are
pressing a boat hard enough to start lifting the transoms it is
better to have the bows under water slightly first and you will have
better chance of recovery.
Regards,
Robert
--- In harryproa@yahoogroups.com.au, David Howie <dana-tenacity@u...>
wrote:
>
> we have those wavepiercer bows on the newest A class. Morelli &
Melvin have
> quite an extreme version but in an article said they'd never do it
on a larger
> design. It only works on small beach cats because of the crew's
ability to get
> the weight aft. On a larger boat they'd be very susceptible (sp?)
to nose
> diving.
>
> ------ Original Message ------
> Received: Sun, 22 Jan 2006 09:08:03 AM MST
> From: "Robert" <cateran1949@y...>
> To: harryproa@yahoogroups.com.au
> Subject: Fw: [harryproa] Re: sailing Elementarry
>
> Quite correcct. Limit of power. Speed of assembly is an important
> factor. You can cover a lot of ground in those extra minutes spent
> rigging. Light air performance is probably the greatest advantage
as
> you can get up into cleaner air. Still reckon the schooner will do
it
> for top speed unless you can get your backside further aft.
> Continue to onder if the latest Nacra type bows with fatter down
> below and less height may provide earlier bouyany forward and be
> slightly slipperier through the water in the intermediate stage.
> Again , getting your backside futher aft would be a lot easier.
>
> I am not quite sure if I am on the same planet as those who persist
> in a lw pod for a sailing proa. Am I missing somethingin my
> understanding of hydrodynamics and hydrostatics. My calculatons for
> the hydrostaics show the boat has a greater tendancy to keep going
> over if slightly >90degrees as the ww hull is more likely to go
paast
> top dead centre. But then again, the mast is not designed for those
> loads in Jzerro.
> Regards,
> Robert
> >
> > G'day,
> >
> > The diagonal stability is the limit on the power, not the speed,
> but on the face of it, you are correct. The lower coe will mean
less
> nose diving. However, there will be a weight aloft saving (as
well
> as a weight overall saving) which is a plus for the una rig and
> speed overall. There is also more twist (thus lower coe) in a
> higher rig, as well as better light air performance. Won't know
all
> the trade off until we try it. Thje una rig will certainly be
> quicker to rig, which is a concern as well.
> >
> > Should also note that with 22 sqm of sail, my El is definitely a
2
> person boat in a breeze. A crew will definitely increase the
breeze
> at which it falls over.
> >
> >
> >
> > regards,
> >
> > rob----- Original Message -----
> > From: Robert
> > To: harryproa@yahoogroups.com.au
> > Sent: Friday, January 20, 2006 10:20 AM
> > Subject: [harryproa] Re: sailing Elementarry
> >
> >
> > For Elementarry , the limit on speed seems to be the forces
that
> bury
> > the bow: drag on lw hull, height of coe of sail power, fore aft
> > righting moment. Making fatter or taller bows to improve fore
aft
> > righting moment may not do any good as it increases drag (In
fact
> > Nacra have gone the other way and chopped off the top of their
> bows
> > but kept or possibly increased the lower bouyancy); Going
longer
> > means a bigger boat; reducing depth and drag of rudders should
do
> > something; replacing a schooner rig with a una rig will lift
coe
> of
> > sail power and make it worse, unless through increased
efficiency
> of
> > the rig there is less drag on the hull and foils in preventing
> > leeway. Can't see it myself unless you go to wing.
> > Regards
> > Robert
> >
> >
> > --- In harryproa@yahoogroups.com.au, "Rob Denney" <proa@i...>
> wrote:
> > >
> > >
> > > G'day,
> > >
> > > Not much difference in speed, although I have no real
numbers
> to
> > compare as I have not used an Easyrig on Elementarry. Cost is
> > probably similar, the easyrig maybe a little cheaper. Ditto
ease
> of
> > construction. I would be quite happy cruising with either.
> Suspect
> > neither is as fast as a wingmasted una rig, which is the next
one
> to
> > try..
> > > I found it was easiest to drop the jib and sail with the
main
> > only when I needed to reef. This would not work on the schooner
> where
> > the aft sail would be reefed first. It is pretty easy to sail
> the
> > schooner on the front sail, very difficult on the rear one.
> > >
> > > Polycore butt joins with bog or nothing. It will require a
> lot
> > of resin to fill the gap if infusing so some form of filling is
> > probably required.
> > >
> > > Compounding Polycore may be possible with an iron, or with
> > slits. Need to do some tests to see.
> > >
> > > Regards,
> > >
> > > Rob
> > >
> > > I must admit the schooner rig appeals to me as well, though
> when
> > I pushed Rob
> > > he seemed to favour the easyrig (Harry) and after all it's
> his
> > baby and he
> > > probably has more time sailing both rigs than all of us.
What
> > happens to the
> > > balance of the easy rig with two reefs, or if you are
running
> > with the main
> > > down in heavy air?
> > > Would really appreciate a detailed comparison of the two
with
> a
> > few numbers
> > > thrown in (speed, cost, ease of construction).
> > > Another question about the poly-core, how do you do butt
> joins?
> > how do you
> > > form compound shapes? Sorry if this makes me sound like a
> Wally
> > who knows
> > > nothing but it's big project for me.
> > > Cheers
> > > David
> > >
> > > ------ Original Message ------
> > > Received: Tue, 17 Jan 2006 09:26:03 AM MST
> > > From: "Robert" <cateran1949@y...>
> > > To: harryproa@yahoogroups.com.au
> > > Subject: [harryproa] Re: sailing Elementarry
> > >
> > > For cruising I still prefer the schooner rig. Yes extra
> sheets
> > and
> > > sheet loads but you can bring sails closer to deck as you
> don't
> > need
> > > clearance for the forward part of the boom and you can
couple
> the
> > > sheets and use a small winch. Overall significantly lower c
> of e
> > of
> > > rig and therefore less capsizing moment for given sail
area.
> Also
> > for
> > > shallow water sailing there is some directional control
with
> just
> > the
> > > sails. Whether to go for a wingmast or a round mast with
> pocket
> > luff,
> > > I am ambivalent. Wing mast probably more efficient but I
like
> > > simplicity and reliability of pocket luff, Wharrams are
> pretty
> > happy
> > > with them (OK I know that is not necessarily an argument
> about
> > how
> > > well they sail but it is an argument over there
reliability)
> I am
> > > even tempted to go for a Wharram type gaff rig only using a
> > nicely
> > > curved carbon tube for the top spar. I like the idea of the
> > unstayed
> > > wishbone boom
> > >
> > > Down wind for cruising it has to be a kite. Lifting bows
> instead
> > od
> > > depressing them. On a long downhill section put all other
> sails
> > away
> > > and relax unless you want to get that little bit more out
of
> the
> > kite
> > > by figure of eight flying. No worries about leaping off the
> top
> > of
> > > the wave and plowing into the back of the next one,
stalling
> and
> > > pitchpoling as you haven't let go of the screecher in time
> and
> > the
> > > apparant wind has doubled. With a kite your bows stay up
and
> if
> > you
> > > do stall into the back of the next wave the kite will pull
> you up
> > > insead of over --- In harryproa@yahoogroups.com.au, Mike
> Crawford
> > > <jmichael@g...> wrote:
> > > >
> > > >
> > > > For going fast, I'm more a fan of Rob's schooner rig
than
> the
> > > easyrig.
> > > >
> > > > This is partially because there are no concerns about
> > forestay
> > > > tensions, and fewer concerns about rig stiffness, and
> mostly
> > > because it
> > > > provides for more sail area, with better foil shapes, and
a
> > lower
> > > center
> > > > of effort. When tacking downwind in light wind, two
> battened
> > foil
> > > > shapes are going to generate more lift than a main and
jib,
> and
> > > when
> > > > running the schooner could present quite a wing-on-wing
> profile.
> > > >
> > > > The schooner rig will require more winch work than an
> > easyrig,
> > > but
> > > > only when lazy sailing. if you want to be competitive,
> you'd
> > need
> > > all
> > > > sorts of additional strings on an easyrig anyway. I'd
> rather
> > go
> > > with a
> > > > pair of extra-tall mainsails for light wind, and reef
them
> in
> > > normal
> > > > wind, than to try to stiffen an easyrig with running
stays
> and
> > > attempt
> > > > to fasten additional headsails.
> > > >
> > > > ---
> > > >
> > > > Speaking of rig stiffness, I do feel the need to weigh
in
> on
> > the
> > > > comments about Rare Bird's rig. Yes, it's pretty
> flexible.
> > > However, as
> > > > the owner of a lightweight 27' cat, which can only be
> righted
> > by
> > > another
> > > > boat if capsized, I can appreciate a rig that will allow
> some
> > of
> > > the
> > > > gust energy to pass by the boat. Going over on a beach
cat
> or
> > > > Elementarry is wet and inconvenient. Going over on a 9+
> meter
> > boat
> > > is
> > > > tremendously uncool.
> > > >
> > > > If you've got everything right on the edge, with the
> windward
> > > hull
> > > > just skimming the water, it takes *very* little extra
gust
> > energy
> > > to
> > > > suddenly whip the boat over. The only solution is to be
> > lightning
> > > quick
> > > > with the mainsheet, but that's a tall order if you're
going
> to
> > be
> > > doing
> > > > it for more than ten minutes at a time. Flying a hull is
> great
> > > fun, but
> > > > any look at the Stiletto nationals will turn up some
boats
> that
> > > didn't
> > > > hold that fine balance in a gust. Even the skippers of
the
> > > Reynolds 33
> > > > lose it now and then.
> > > >
> > > > When cruising, going past this edge is entirely
> > unacceptable.
> > > It's
> > > > much better to have a flexible rig, with the addition of
> > perhaps an
> > > > outleader kite, than to risk gust-induced capsize (fool-
> induced
> > > capsize,
> > > > of course, is rig-independent).
> > > >
> > > > When racing, though, there's still something to be said
> about
> > a
> > > boat
> > > > that can handle the gusts. Let's say you can fly a hull
> with
> > 40 sq
> > > m of
> > > > canvas with a stayed rig, and 50 to 60 sq m of canvas
with
> a
> > more
> > > > flexible rig. The flexible rig provides two advantages.
> > First, in
> > > a
> > > > gust, the flexible rig will either allow you to keep
> sailing
> > > without
> > > > adjustments, or give you lots of time to adjust, while
the
> > stayed
> > > rig
> > > > will require quick reflexes in order to avoid a capsize.
> > Second,
> > > those
> > > > extra 10 to 20 sq m of canvas will come into play nicely
> in
> > the
> > > lulls,
> > > > do so automatically, while the stayed rig will need to
> either
> > > unreef or
> > > > hoist an extra sail to keep up.
> > > >
> > > > Supporters of a stayed rig will point out that the
extra
> > canvas
> > > will
> > > > create extra drag, so in theory the stiffer rig will beat
> the
> > > flexible
> > > > rig in some conditions. This is true. But a capsized
boat
> > > eliminates
> > > > all rig advantages. Besides, we don't all sail in
exactly
> 15
> > knots
> > > of
> > > > trade winds, and changing wind conditions will likely
favor
> the
> > > extra
> > > > sail area and self-adjusting nature of the flexible rig.
> > > >
> > > > ---
> > > >
> > > > The one change I would make would be to go with an
> unstayed
> > > wishbone
> > > > rig like they have on the Wyliecats.
> > > >
> > > > http://www.wyliecat.com/info/wishbone_rig.html
> > > >
> > > > One adjustment line automatically handles sail shape,
> leech
> > > tension,
> > > > and mast bend, with very little stress on the boom. Sail
> > shaping
> > > is
> > > > very quickly done, the boom creates its own lazy jack
> pocket
> > when
> > > taking
> > > > the sails down, and a reduction in heeling moment can be
> > achieved
> > > either
> > > > by reefing, flattening, or both, allowing for some quick
> sail
> > > > adjustments for a minimal amount of time and effort.
> > > >
> > > > However, I've never sailed a Wyliecat, so I can't speak
> from
> > > > experience. I just love the idea of it.
> > > >
> > > > - Mike
> > > >
> > > >
> > > >
> > > > dominiquebovey wrote:
> > > >
> > > > > Hi,
> > > > >
> > > > > Boats as light and canvassed as HP's mostly sail "close-
> > hauled"
> > > due to
> > > > > their high speed, so they need a rather flat sail
> profile.
> > But to
> > > > > start you need a hollow profile, so the sail should be
> > tunable
> > > quickly.
> > > > >
> > > > > I would see a 8.5m proa (maximum of M2 class) for 3
crew
> > (minimum
> > > > > number for racing on Lake Geneva), with easyrig, around
> 30-
> > 40m2
> > > sail.
> > > > > I am persuaded the easyrig is OK for racing, provided
it
> is
> > stiff.
> > > > >
> > > > > One of the crew would be adjusting the sail permanently
> > (making it
> > > > > hollower in the lulls, flattening it when speed
> increases).
> > > Another
> > > > > crew would be running up/down the tramp to keep the LW
> hull
> > just
> > > above
> > > > > the water, and the 3rd one steering.
> > > > > And all crew could be going on trapezes when needed. So
> you
> > need
> > > > > running sidestays which can be attached to several
> selectable
> > > points
> > > > > on the WW hull or on the beams.
> > > > > To go on trapeze, you unhook them off the boat, and
hook
> them
> > on
> > > your
> > > > > trapeze pants/harness whatever-the-word-is.
> > > > > Naturally the rig must be self supported without the
> runners,
> > for
> > > easy
> > > > > cruising.
> > > > >
> > > > > I know it is quite a new boat, something between
> Harrigami
> > and EL,
> > > > > with more displacement. The Elementarry lw "sinks"
about
> 1cm
> > for
> > > 15kg,
> > > > > for the 8.5m the figure should be 20-25kg, so a less
fine
> lw
> > hull.
> > > > > The Elementarry is unfortunately a little too light for
3
> > racing
> > > crew
> > > > > I am afraid, as we discussed last year.
> > > > >
> > > > > Regards
> > > > > Dom
> > > > >
> > > > >
> > > > > --- In harryproa@yahoogroups.com.au, "Rudolf vd Brug"
> > > <rpvdb@f...> wrote:
> > > > > >
> > > > > > Hi,
> > > > > >
> > > > > > Possibly the difference in sheeting in between you
and
> the
> > > Tornado
> > > > > lies in the fact that they where flying a spinnaker.
> > > > > > That sail is so much fuller in shape it would
redirect
> the
> > wind
> > > > > passing it much more than a flatter sail (or no sail at
> all)
> > > would.
> > > > > >
> > > > > > Some time ago I read an interesting article on a una
> rigged
> > mono
> > > > > with a wing mast. It was designed not to fly downwind
> extra's.
> > > > > > The owner did have a gennaker but it only gave him
one
> knot
> > of
> > > extra
> > > > > boat speed. It was concluded the tighter sheeting angle
> of
> > the
> > > main
> > > > > might be responsible for this. The gennaker would
> generate so
> > much
> > > > > disturbance of the air passing at the leeward side it
> doesn't
> > > attach
> > > > > to the main any more. Therefore the main doesn't
generate
> > lift as
> > > it
> > > > > does whith no head sail in front and is only producing
> drag
> > which
> > > > > helps downwind but not as much as lift would.
> > > > > > ----- Original Message -----
> > > > > > From: Rob Denney
> > > > > > To: harryproa@yahoogroups.com.au
> > > > > > Sent: Monday, January 16, 2006 2:19 PM
> > > > > > Subject: Re: [harryproa] Re: sailing Elementarry
> > > > > >
> > > > > >
> > > > > > G'day,
> > > > > >
> > > > > > Not sure the kite would have helped much as the
> apparent
> > was
> > > well
> > > > > forward of the beam. Still intend to try it because
they
> are
> > such
> > > > > great fun. Interestingly, the Tornado was strapped in
> hard,
> > > traveller
> > > > > on the centreline, whereas i was quite eased on the
same
> > point of
> > > sail
> > > > > and at the same speed. Lots to learn...
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > --------------------------------------------------------
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