Subject: [harryproa] Re: On board sailing report
From: "Robert" <cateran1949@yahoo.co.uk>
Date: 2/24/2008, 6:46 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

I can't see why bow burying should be a problem. The boat with a high
prismatic coeffient and long bows has plenty of hydrostatic lift with
a long lever arm and therefore has plenty of resistance to burying. As
soon as you start adding extras, you tend to cause extra drag as the
boat goes through waves, and if you have the wind behind you,
increasing the load on the bows, slowing the boat even more, and
possibly leading to pitchpoling. The bows, as they are, shed water
easily. There are good reasons for the latest crop of round the world
racing tris going to low resistance bows. If hydrodynamic lift is
required, it is better further back, using well constructed foils that
could lift the boat and reduce resistance. But that is a very
different concept.
Consider the way that the bows meet a wave. The low down bouyancy
meets the wave early and starts to gradually lift the boat and if the
wave is steep, will go through the wave, still lifting the bows with
hydrostatic lift, but not slowing the boat too suddenly, until it
starts to come out of the back of the wave still shedding water, and
having provided enough lift to hopefully allow the crossbeams to clear
the wave. Compare this with a bow with greater flare and more rocker.
The bow hits the wave and bounces up if the wave is small, stalling
the boat and making a mess of the flow of air across the sail. If the
wave is too big and steep, then the bows will bury and because of the
flared bow, there will be more resistance to the bows lifting again.
One needs to consider that the bows of any boat are depressed enough
to counteract the lever arm of the driving force, ie the sails. The
lower the resistance , the less force needed to drive the boat and the
lower the leverage pressing the bows down. By having little or no
rocker, long bows and plenty of bouyancy low, the boat sails very
flat. A boat with more rocker, less low down bouyancy, shorter bows
and flare in the bow, would be nose down in similar circumstances with
a much more variable lift and resistance as it tried to go over or
through waves and less ability to shed water off its top sides.
I must admit, the concept of flying down the face of a wave into the
back of another, does not appeal , but when closely looking at the
dynamics, I do not see any advantage in adding bits. (Though I had
considered the idea of a small 'Whale Tail' appendages below the
waterline, that were prevented from going above the horizontal when
the boat was pressing down and angled enough on the way up to add to
propulsion. Something like the fins on a mirage drive. The complexity
I think makes it impractical).
I think cheers is a wonderful boat and followed closely its original
passage across the Atlantic but do not consider the Hobie 16 shaped
bows the way to go for the open ocean.
Robert

--- In harryproa@yahoogroups.com.au, "Gunnar Westholm"
<gunnar.westholm@...> wrote:
>
> How aboue the bow design as on Cheers:
>
http://membres.lycos.fr/ugmarie/zacheers/cheersjpg/rougevinbaville/cheersparrougevinbaville0005.html
> No extra drag in water or wind...
>
> /Gunnar
>
>
> 2008/2/24, numar28 <nuno.marques@...>:
> >
> > Bow burrying is one of my concerns with this design, any one
> > considered if the addition of side lifting strakes would improve
> > this characteristic? drag wise eventually would be less or similar
> > to lenghtening the hull.
> > Regarding the reported drag streams at the rudders, it looks like
> > this is what we call in hydrodynamics 'ventilation' . To cure this
> > in a previous catamaran I owned, with stern hung rudders, I used a
> > suggestion from the Marchaj(?)book, adding a ring of about one
> > inch wide perpendicular to the rudder profile and paralel to the
> > water line, in my case in line with the continuation of the hull
> > (5CM deep) but in the case of side hung rudders I would place them
> > deeper in a way to never be exposed above water surface even when ww
> > hull flies.
> > My rudders became much more responsive (just like on a rail track)
> > and ventilation disapeared.
> >
> > rgds,
> >
> > Nuno
> > --- In harryproa@yahoogroups.com.au
<harryproa%40yahoogroups.com.au>, "Rob
> > Denney" <harryproa@>
> > wrote:
> > >
> > > G'day,
> > >
> > > Excellent! Any idea how quick it goes with the hull up? How much
> > wind to
> > > get it flying? Have you got a plan for it it goes over? The
> > masts will
> > > float, but make sure they are tied into the boat or it gets messy
> > when the
> > > boat is on it's side with the masts pointing upwind. The hulls
> > blow down
> > > wind and the masts stay where they are.
> > >
> > > regards,
> > >
> > > Rob
> > >
> > > On Feb 14, 2008 10:35 AM, Doug Haines <doha720@> wrote:
> > >
> > > > Hi,
> > > >
> > > > Sailing getting up in air easily, steering to controllift. Nose
> > not
> > > > digging too bad, but rudder develops those drag streams -
> > separation off the
> > > > foil at about time get airborne. Not fair enough after adding
> > extra
> > > > elongation recently
> > > > Doug
> > > >
> > > > *Doug Haines <doha720@>* wrote:
> > > >
> > > > Hi,
> > > >
> > > > Sailing's been pretty good lately, fast and fun, and mostly dry.
> > > > I get to the limit of my nerves or of the boat fairly easily
> > now - the ww
> > > > hull has definitely been up out of the water, immediately at
> > which time I
> > > > dumped sheet.
> > > > The other thing that is limiting is the bow burying into the
> > water. It
> > > > could probably take more submersion, but I get too scared and
> > ease off. The
> > > > hull is lifting up a bit usually at about the time that the bow
> > is digging
> > > > in a lot, so all in all I just ease sheets and speed drops back
> > to like 9-10
> > > > knots. The top speed has been around 13-14 knots. Using GPS lent
> > to me.
> > > > FAirly satisfied with that I guess.
> > > > Sail are could stay the same and a longer lw hull would increase
> > speed a
> > > > lot. My overall beam is very narrow only 3.?m and is about right
> > for current
> > > > dimensions of rest of boat.
> > > > Extra metre beam would combine with a longer lw hull and make
> > more speed
> > > > possible.
> > > >
> > > > Maybe harrygami size lw hull, 4.5m overall beam, and two
> > schooner masts
> > > > with just a bit more area than mine with flat heads/fat heads
> > sail tops.?
> > > >
> > > > Good enough as is though. Tough enough to anchor (pulling up),
> > lots of
> > > > windage, especially when sails hoisted, woudn't like any more
> > work than
> > > > already have.
> > > >
> > > > Doug
> > > >
> > > > *Rob Denney <harryproa@>* wrote:
> > > >
> > > > G'day,
> > > >
> > > > I have put some photos in the Files section (not sure why I
> > didn't put
> > > > them in Photos). They are not pretty and it is definitely time to
> > > > paint all the changes and mistakes, but they work. Any
> > questions, let
> > > > me know.
> > > >
> > > > regards,
> > > >
> > > > Rob
> > > >
> > > > On Jan 21, 2008 5:55 PM, Jim Baltaxe
> > <jim.baltaxe@<jim.baltaxe%40vuw.ac.nz>>
> > > > wrote:
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > Hi Mark &al
> > > > >
> > > > > Any chance of some photos or drawings of the beam mounted
> > rudders?
> > > > >
> > > > >
> > > > >
> > > > > Enjoy
> > > > >
> > > > > Jim Baltaxe
> > > > >
> > > > > They said, get a life. I looked on TradeMe but I couldn't find
> > one.
> > > > > ________________________________
> > > > > From: harryproa@yahoogroups.com.au
<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>[mailto:
> > > > harryproa@yahoogroups.com.au
<harryproa%40yahoogroups.com.au><harryproa%40yahoogroups.com.au>] On
> > > > > Behalf Of Mark Stephens
> > > > > Sent: Tuesday, 15 January 2008 11:20 p.m.
> > > > > To: harryproa@yahoogroups.com.au
<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>
> > > > > Subject: Re: [harryproa] Re: Anyone there ?
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > The biggest negative about the hull hung rudders, well the mk
> > 2 version,
> > > > is
> > > > > they would be difficult to replace once the shear pins broke.
> > At the
> > > > moment
> > > > > they are designed to 'break away' in the event of a collision.
> > You would
> > > > > then have to retrieve them from the end of the attachment line
> > and refit
> > > > > them with new shear pins. This may seem like a big
> > disadvantage but it
> > > > will
> > > > > only happen in a catastrophic event which would render any
> > catamaran
> > > > with a
> > > > > stuck and broken daggerboard at best and a split hull and bent
> > rudder
> > > > shaft
> > > > > at worst.
> > > > >
> > > > > We are not in the business of selling boats using boatshows and
> > > > brochures.
> > > > > We are enthusiasts trying to promote the proa as a viable
> > alternative to
> > > > > people who understand that Harryproas don't have the decades of
> > > > development
> > > > > other multis have. Some things, rudders in particular, will go
> > through
> > > > many
> > > > > iterations before the perfect solution is reached and we keep
> > all of our
> > > > > developments transparent. Maybe not commercially sensible but
> > that's not
> > > > > what we are about. I'm sure all those subscribed to this group
> > are here
> > > > > because of this.
> > > > >
> > > > > Hopefully the beam mounted rudders will prove to be the best
> > option. Rob
> > > > has
> > > > > experimented with them and they seem to be working well. The
> > biggest
> > > > concern
> > > > > was the distance from the boats centre but this has proven OK
> > on
> > > > > Elementarry. Blind Date will be trying them as will Solitarry.
> > As they
> > > > will
> > > > > kick up in both directions and won't be as draggy let's hope
> > they prove
> > > > > successful.
> > > > >
> > > > > Mark
> > > > >
> > > > > Rob Denney wrote:
> > > > >
> > > > >
> > > > >
> > > > > G'day,
> > > > >
> > > > > The side of hull mounted rudders work well, as did the in hull
> > dagger
> > > > > rudders before them and the in hull spade rudders before them.
> > They
> > > > > are far better than the rudders and daggerboards in most
> > multihulls.
> > > > > However, none were the perfect solution and this is what we are
> > > > > looking for. The beam mounted rudders are another (quite
> > large) step
> > > > > in this direction and have been tested by me on my
> > Elementarry, and
> > > > > now on my solo boat. They will then be included in the plans.
> > > > > Anyone who is now at the rudder stage of their build should
> > discuss
> > > > > the options before they proceed.
> > > > >
> > > > > Because I believe it is in everyone's interest if I am upfront
> > about
> > > > > what we are doing and give details of experiments that have
> > been tried
> > > > > (rail mounted riudders etc) there is a lot of discussion.
> > These are
> > > > > ideas, not "designs" and they may or may not end up on the
> > plans.
> > > > >
> > > > > Rudders and daggerboards/keels are the "Achilles heel" of
> > almost all
> > > > > boats. We are trying to reduce the potential for damage,
> > reduce the
> > > > > cost and improve the performance rather than taking the stance
> > of the
> > > > > rest of the industry that there is nothing that can be done
> > about it
> > > > > and that it is normal for daggerboards to break and hulls to
> > split
> > > > > when they collide with something and that boats should be
> > confined to
> > > > > deep water because of the depth of their rudders.
> > > > >
> > > > > The side of hull rudders in dagger cases do hit a fair bit of
> > water
> > > > > as can be seen in the Rare Bird video. They may or may not be
> > > > > draggier than the conventional slot for daggerboards. They are
> > not
> > > > > likely to cause any handling problems and the spray they kick
> > up is
> > > > > not likely to reach the cockpit. They do have the advantage
> > that in a
> > > > > collision, they kick up and in storms, shallow water and on the
> > > > > mooring, they can be lifted. Their biggest advantage is that
> > in the
> > > > > event of damage, there are no holes below the waterline.
> > > > >
> > > > > The beam mounted rudders keep all these advantages and solve
> > the spray
> > > > > problem. They are also considerably easier to build.
> > > > >
> > > > > regards,
> > > > >
> > > > > Rob
> > > > >
> > > > > On Jan 15, 2008 1:54 PM, Jim Baltaxe
> > <jim.baltaxe@<jim.baltaxe%40vuw.ac.nz>>
> > > > wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > Hi Robert
> > > > > >
> > > > > > If what you say about the rudders is true then why is there,
> > or has
> > > > there
> > > > > > been, so much worrying about the design of the rudders? Rob
> > and others
> > > > > have
> > > > > > been concerned about the lower brackets being caught by
> > waves, designs
> > > > > have
> > > > > > been posted for rudders hung from the akas and there was
> > even a
> > > > proposal
> > > > > to
> > > > > > hang rudders from stub akas. I'm not even talking about
> > hanging a
> > > > single
> > > > > > rudder/daggerboard from a track on the lee hull and hauling
> > it end to
> > > > end
> > > > > > during a shunt.
> > > > > >
> > > > > > I am aware that there are other things than simple strength
> > or turning
> > > > > > moment involved in rudder design but it seems to be received
> > knowledge
> > > > > that
> > > > > > rudders are the "Achilles heel" of proas.
> > > > > >
> > > > > >
> > > > > >
> > > > > > Enjoy
> > > > > >
> > > > > > Jim Baltaxe
> > > > > >
> > > > > > They said, get a life. I looked on TradeMe but I couldn't
> > find one.
> > > > > > ________________________________
> > > > > > From:
harryproa@yahoogroups.com.au<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>[mailto:
> > > > harryproa@yahoogroups.com.au
<harryproa%40yahoogroups.com.au><harryproa%40yahoogroups.com.au>]
> > > > > On
> > > > > > Behalf Of Robert
> > > > > > Sent: Monday, 14 January 2008 4:01 p.m.
> > > > > >
> > > > > > To: harryproa@yahoogroups.com.au
<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>
> > > > > > Subject: [harryproa] Re: Anyone there ?
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > -Hi Jim,
> > > > > > I was certainly impressed with the build when I saw 'Aroha'
> > in the
> > > > > > earlier stages- I even helped with a bit of the fairing on
> > one of the
> > > > > > rudders so it must be good! I cant see any problems with the
> > rudders
> > > > > > as far as slowing the boat down and Rare Bird was a good
> > pilot study
> > > > > > for the robustness. The brackets are strong enough to take
> > the sailing
> > > > > > loads so the bit of slapping won't worry them. There is not
> > much
> > > > > > increase in wetted area if the brackets hit a wave and it
> > would damp
> > > > > > even further the minimal chance of hobby horsing, which
> > could actually
> > > > > > improve performance. (I reckon they also provides a means of
> > getting
> > > > > > on board again from in the water)
> > > > > > Coming over bars is a good test for robustness
> > maneuverability and
> > > > > > handling.
> > > > > > Wish you well in the legal wrangles,and I am sure that Bain
> > would be
> > > > > > happy for Aroha to go to a good home,
> > > > > > Robert--
> > > > > >
> > > > > >
> > > > > > In harryproa@yahoogroups.com.au
<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>, "Jim
> > > > Baltaxe" <jim.baltaxe@> wrote:
> > > > > > >
> > > > > > > Hi Robert
> > > > > > >
> > > > > > > I did get out onto him/her on the last day before Bain so
> > kindly
> > > > took me
> > > > > > > to the airport, but unfortunately it was pelting down like
> > mad. We
> > > > rowed
> > > > > > > out to the boat, moored in a river near Bain's house and
> > had a good
> > > > look
> > > > > > > around but never got off the mooring. We had neither the
> > time nor
> > > > the
> > > > > > > breeze to prove much.
> > > > > > >
> > > > > > > The boat appears to be very well built and very much what
> > I do want.
> > > > > > > Enough room for one or two people for extended coastal
> > cruising and
> > > > the
> > > > > > > pop-up canopy over the upper cockpit was a cozy place for
> > us to
> > > > shelter
> > > > > > > in the rain and talk about, as well as look at, the boat.
> > > > > > >
> > > > > > > My only real reservation about the design is the ongoing
> > question of
> > > > > > > rudder attachments. Aroha's appear solid but the lower
> > brackets
> > > > > > > certainly will certainly be caught in almost anything more
> > than a
> > > > flat
> > > > > > > sea. I really don't know whether that would make much
> > difference to
> > > > > > > overall performance, though.
> > > > > > >
> > > > > > > I did see Aroha come across the bar into the river a
> > couple of days
> > > > > > > earlier and it was an impressive sight.
> > > > > > >
> > > > > > > I am still working on the legal and financial issues so I
> > am hoping
> > > > that
> > > > > > > I will be able to make a reasonable offer fairly soon. In
> > the
> > > > meantime,
> > > > > > > I do wish Bain good luck and if I miss out, so be it. If
> > everything
> > > > > > > works well, perhaps I'll be able to get across for another
> > look and
> > > > a
> > > > > > > ride later this year.
> > > > > > >
> > > > > > > Enjoy
> > > > > > >
> > > > > > > Jim Baltaxe
> > > > > > >
> > > > > > > They said, get a life. I looked on TradeMe but I couldn't
> > find one.
> > > > > > >
> > > > > > > ________________________________
> > > > > > >
> > > > > > > From:
harryproa@yahoogroups.com.au<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>[mailto:
> > > > harryproa@yahoogroups.com.au
<harryproa%40yahoogroups.com.au><harryproa%40yahoogroups.com.au>]
> > > > > >
> > > > > > > On Behalf Of Robert
> > > > > > > Sent: Thursday, 3 January 2008 11:58 p.m.
> > > > > > > To:
harryproa@yahoogroups.com.au<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>
> > > > > >
> > > > > > > Subject: [harryproa] Re: Anyone there ?
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > -G'day Jim,
> > > > > > > Sorry to hear of your difficulties. Not a nice situation
> > but there
> > > > can
> > > > > > > be an afterlife
> > > > > > > Did you get a chance to sail on Aroha?
> > > > > > > Robert
> > > > > > >
> > > > > > > -- In
harryproa@yahoogroups.com.au<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>
> > > > > >
> > > > > > > <mailto:harryproa%40yahoogroups.com.au> , "Jim Baltaxe"
> > > > > > > <jim.baltaxe@> wrote:
> > > > > > > >
> > > > > > > > Hi Robert &al
> > > > > > > >
> > > > > > > > I'm in exactly the same position which is why I've had
> > my head
> > > > down
> > > > > > > for
> > > > > > > > a while, since Derek's workshop and my visit with Bain.
> > I'm still
> > > > > > > trying
> > > > > > > > to work out the "disengagement" (what else do you call
> > a "divorce"
> > > > > > > from
> > > > > > > > a legally recognised, long-term, relationship?) so that
> > perhaps I
> > > > can
> > > > > > > > get the money together. Sorry Bain but I am trying,
> > really hard.
> > > > > > > >
> > > > > > > >
> > > > > > > > Enjoy
> > > > > > > > Jim Baltaxe
> > > > > > > > 209 Derwent Street
> > > > > > > > Island Bay, Wellington
> > > > > > > > NEW ZEALAND
> > > > > > > > +64 (04) 938 6018
> > > > > > > > 027 563 5018
> > > > > > > > They said, get a life. I looked on TradeMe but I
> > couldn't find
> > > > one.
> > > > > > > >
> > > > > > > > ________________________________
> > > > > > > >
> > > > > > > > From:
harryproa@yahoogroups.com.au<harryproa%40yahoogroups.com.au>
> > <harryproa%
> > 40yahoogroups.com.au>
> > > > > >
> > > > > > > <mailto:harryproa%40yahoogroups.com.au>
> > > > > > >
[mailto:harryproa@yahoogroups.com.au<harryproa%40yahoogroups.com.au>
> > <harryproa%
> > 40yahoogroups.com.au>
> > > > > >
> > > > > > > <mailto:harryproa%40yahoogroups.com.au> ]
> > > > > > > > On Behalf Of Robert
> > > > > > > > Sent: Thursday, 20 December 2007 4:16 p.m.
> > > > > > > > To:
harryproa@yahoogroups.com.au<harryproa%40yahoogroups.com.au><harryproa%
> > 40yahoogroups.com.au>
> > > > > >
> > > > > > > <mailto:harryproa%40yahoogroups.com.au>
> > > > > > > > Subject: [harryproa] Re: Anyone there ?
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > -waiting with bated breath for the next development of
> > the Harry.
> > > > Love
> > > > > > > > to see the promised photos of Sidecar and Solitarry I am
> > still
> > > > keen to
> > > > > > > > get a Harry but health and wealth defy me. The concept
> > still makes
> > > > the
> > > > > > > > most sense to me and the boats out there look pretty
> > good. If I
> > > > had
> > > > > > > > the cash I'd probably just buy Bain's Aroha and get
> > sailing.
> > > > > > > > Meanwhile I'm investigating doing a KSS system using
> > polyprop and
> > > > > > > > epoxy with an end bulkhead with foam ends.
> > > > > > > > Robert
> > > > > > > >
> > > > > > > > -- In
harryproa@yahoogroups.com.au<harryproa%40yahoogroups.com.au>
> > <harryproa%
> > 40yahoogroups.com.au>
> > > > > >
> > > > > > > <mailto:harryproa%40yahoogroups.com.au>
> > > > > > > > <mailto:harryproa%40yahoogroups.com.au> , "vertiges59"
> > > > <vertiges59@>
> > > > > > > > wrote:
> > > > > > > > >
> > > > > > > > > Nobody more in this group ?????
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > > ________________________________
> > > > >
> > > > > No virus found in this incoming message.
> > > > > Checked by AVG Free Edition.
> > > > > Version: 7.5.516 / Virus Database: 269.19.2/1224 - Release
> > Date:
> > > > 14/01/2008
> > > > > 5:39 PM
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > > ------------------------------
> > > > Support the World Aids Awareness campaign this month with Yahoo!
> > for
> > Good<http://us.rd.yahoo.com/mailuk/taglines/isp/control/*http://us.rd
> > .yahoo.com/evt=51947/*http://uk.promotions.yahoo.com/forgood/>
> > > >
> > > >
> > > > ------------------------------
> > > > Yahoo! Answers - Get better answers from someone who knows. Try
> > it
> > now<http://uk.answers.yahoo.com/;_ylc=X3oDMTEydmViNG02BF9TAzIxMTQ3MTc
> > xOTAEc2VjA21haWwEc2xrA3RhZ2xpbmU>.
> > > >
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> > >
> >
> >
> >
>

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