I don't Know minimal materials,break through in the building
proccess minimum build time required etc..... This is what Rob
preaches as soon as any one mentions traditional design. Knowing
that a shunting outrigger canoe needs minimal amount of anything to
go 1 to 1-1/2 times the wind speed at any boat length. Is why I
ask.
I get the custom outfit. But 1/3 the price with half as much room
and with only 1/6 the hardware!?
Todd
--- In harryproa@yahoogrou
>
>
> The big question is why handmade boats of this size and speed cost
so
> little.
>
> - Mike
>
>
>
> Todd wrote:
> >
> > I like the idea of an unstayed mast especially on a boat that
> > doesn't need to have gobs of sail area to attain good overall
speed.
> >
> > Don't really agree with you on the wire vs foil thingy, may be
just
> > my misunderstanding. I don't have a formal education in
> > aerodynamics. But doesn't frontal area and cord width play a
part in
> > your apple vs an orange theory ;) I wonder what the out come
would
> > be with the same size sail for given length masts attach to each
> > would be?
> >
> > Rob,
> >
> > If the whole principal behind your designs are minimal material
and
> > hardware then why such the high price tag $$$$$ on used boats ?
> >
> > Todd
> >
> > --- In harryproa@yahoogrou
> > <mailto:harryproa%
> > wrote:
> > >
> > > The Wharram rig makes sense to me, possibly with a curved gaff
to
> > > sooth the exit. Not sure of how to set up the unstayed mast to
> > take
> > > the point loading of the gaff,
> > > Robert
> > > --- In harryproa@yahoogrou
> > <mailto:harryproa%
<brag_rotor@
> > > wrote:
> > > >
> > > > Greetings,
> > > >
> > > > This is a hopefully useful contribution to the debate on
> > > > sail formats for the HarryProa.
> > > >
> > > > We have sailed a Wharram Tiki 30 since the '90s,
and 'Pilgrim'
> > > > has provided us with a source of much glee in nailing much
> > > > larger and supposedly faster vessels on most points of sail.
> > > >
> > > > The numbers we can demonstrably repeat (especially since our
> > > > recent coat of bottom paint) caused some surprise when I
posted
> > > > them last time - apologies for my lack of tact. All boats are
> > > > an improvement over no boat, and it is not my place to
denigrate
> > > > anybody's design, multihull or monohull.
> > > >
> > > > Pilgrim is a small catamaran, and cannot comfortably sustain
high
> > > > speed in rough water - ask my wife! Well, Olly isn't
> > comfortable,
> > > > anyway. We will need something more comfy and spacious for
our
> > > > declining years, but I am most reluctant to give up on the
> > > > giant-killing fun we enjoy. Eaten any Oysters lately? #;^p
> > > >
> > > > That's why we're here.
> > > >
> > > > We did check our numbers and have also discovered (see PS)
that
> > we
> > > > can point and foot well under main alone. So my focus is now
on
> > > this
> > > > type of mainsail, and its possible application to an EasyRig.
> > > >
> > > > The Wharram Tiki Wingsail is a cunning combination of a wrap-
> > around
> > > > sleeve luff and a short gaff. Usually loose-footed due to the
> > huge
> > > > sheeting angle available on a cat, the rig is simple to use.
It
> > > will
> > > > reef going downwind (a major safety factor) because of the
loose
> > > > sleeve luff and the weight of the gaff bringing the top down;
> > plus
> > > it
> > > > is safe to gybe all-standing due to the lack of a boom.
> > > >
> > > > The gaff keeps the sail area useful to the top of the rig,
since
> > > > bermudan triangles lose performance rapidly as the sail chord
> > > shrinks
> > > > with respect to the mast. A square-top variant is easy to
make;
> > > > the gaff then becomes (in effect) a batten, but cheaper than
most
> > > > modern battens-with-
> > > >
> > > > Aerodynamics - this has been an interest of mine since
boyhood,
> > and
> > > > as a student I recall our aerodynamics instructor at the CAAE
> > > telling
> > > > us that even a small wrinkle or rivet can perturb the flow.
> > > >
> > > > His favourite example was a wire and a foil, which I have
> > uploaded
> > > to
> > > > the photos folder 'Aerodynamics and Sails' .....
> > > >
http://au.ph.
> >
<http://au.ph.
> > > >
> > > > This illustration is meant to focus on the importance of very
> > small
> > > > things in the overall drag picture - a sailing boat, for
> > example.
> > > >
> > > > Depending on the Reynolds Number....
> > > > (http://en.wikipedia
> > <http://en.wikipedia
> > > >
> > (http://www.princeto
> > <http://www.princeto
> > > > ....the foil could be of the order of 10x the thickness of
the
> > > > wire for the same drag. This can double at very low Reynolds
Nos
> > > > (Re) to around 20x - and sails run at low Re.
> > > >
> > > > Which suggests that a 5% imperfection might _double_ the
drag in
> > the
> > > > worst case. It can, too. Some shapes are worse than a round
> > wire.
> > > >
> > > > This puts exposed masts in a poor light unless they rotate
> > > > very precisely. Shrouds don't look good, either. They are in
> > > > the low Re zone for sure.
> > > >
> > > > Sailmakers do have techniques for picking up some cleaner
flow to
> > > > leeward of masts by putting a baggy step in the leading edge
of
> > > sails,
> > > > but it is still a disaster in terms of aircraft quality fluid
> > > dynamics.
> > > >
> > > > There is a _lot_ of improvement to be had over a bermudan
rig.
> > > >
> > > > The Wharram approach uses a deep sleeve luff, so that the
mast
> > > > 'disappears' aerodynamically inside the sail, like the spar
on an
> > > > aircraft wing. The cut is all-important, since smaller
> > > imperfections
> > > > start to matter more once the main sources of drag are
addressed.
> > > > Chris Jeckells made my sails, bless him.
> > > >
> > > > The thickness of the mast ceases to be of great aerodynamic
> > > importance
> > > > when the sail is hoisted, so it can be properly plump and
> > stiff.
> > > Not
> > > > too plump, since we do not want excessive drag when reefed
or in
> > > high
> > > > wind with the rig down. Fortunately the stiffness of a beam
or
> > pole
> > > > increases rapidly with diameter. Flexibility to shed wind
load
> > in a
> > > > gust could be added in the gaff - like a windsurfer's flexing
> > > batten.
> > > >
> > > > Two Tiki Wingsails are shown in the photo folder, one seen
from
> > > > another boat, and one shot from on board. These are not
Pilgrim,
> > > > and the sails do not seem to be setting as well as ours. A
lot
> > > > of people are relaxed about sails, and as I have admitted to
> > Rob,
> > > I'm
> > > > a pestilentially picky perfectionist when it comes to sail
shape.
> > > >
> > > > Wrinkles may be common - but I prefer them on other people's
> > sails,
> > > > not mine! Remember the wire and the foil. A 5% wrinkle
> > > > might double the drag - so how about lots of small wrinkles?
> > > >
> > > > The two photos are there to show the Wharram wingsail - more
at:-
> >
> > > > http://www.wharram.
> > <http://www.wharram.
> > > range/Tiki-30
> > > >
> > > > So what do you folks think, is there a case for using a
Wharram
> > > > sleeve luff/gaff combination on a HarryProa EasyRig?
> > > >
> > > > All the best, Ben
> > > >
> > > > PS
> > > > About that run up the coast of Lanzarote in January under
main
> > > > alone - lazy skipper, should have reefed both main and genoa.
> > > > But we learned something interesting.
> > > >
> > > > The tack was 88 degrees on the GPS (and compass - near as
> > > > one can tell on a compass) and we started footing upwind at
> > > > nearly 9 GPS knots. Tricky to get a main flying spot on
without
> > > > any genoa telltales, but eventually we had 9 knots -roughly-
> > > > showing on the GPS. Pretty good, I thought vaguely. It was
> > > > a pleasant surprise to point so well under main alone, which
> > > > is not usually our custom.
> > > >
> > > > Sea was bumpy, hence the reduced rig.
> > > >
> > > > Afterwards I had a look at the GPS points I'd put in and
> > > > from the times did a speed over ground by hand, which was
> > > > 8.8 knots, and 8.8/16 is 55% of max wind speed measured
> > > > 1/3 the way up the mast. 8.8/14 is 63%, so we were going
> > > > pretty well even without a genoa.
> > > >
> > >
> >
> >
>
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