|Subject: Re: [harryproa] Re: Changes|
|From: "Rob Denney" <firstname.lastname@example.org>|
|Date: 3/18/2008, 12:10 AM|
On Mon, Mar 17, 2008 at 9:03 PM, Mark Stephens <mark@harryproa.
> > G'day,
> > On Wed, Mar 12, 2008 at 10:14 PM, Mark Stephens wrote:
> > > I've never been quite sure about the extra sailing loads argument
> as the rigging loads on a cat are taken by strips of uni in the top
> and bottom of the bulkheads, not a big deal.
> > There is about as much material in these strips as in the glass which
> > goes around the hull to support the harryproa mast.
> I agree.
> > comparisons are:
> > 1) The cat has a substantial transverse bulkhead to keep the strips
> > apart and take the sheer loads, and a substantial compression post
> > under the mast, all of which needs to be very solidly glassed to the
> > very solid bridgedeck, hull and cabin roof. Some also have fore and
> > aft bulkheads to prevent the main beam buckling.
> > Harryproas have a single ring frame in the hull. Weighs less than 10
> > kgs glassed in.
> True but a catamarans bulkheads don't just hold the rig up they also
> hold the hulls together, segregate the boat into cabins, holds up the
> bridgedeck etc etc. Either only include the extra uni reinforcing in a
> cats bulkhead or add the weight of a proas beams to make weight
> comparison fair. The mast compression post isn't very heavy, usually
> just a piece of western red cedar glassed to the bulkhead.
> > 2) The fore and aft loads on the cat are enormous and require the
> > hulls to be beefed up (either with extra material or bigger
> > dimensions), plus a forebeam, a seagull striker and a mainsheet
> > traveller with a large beam to support it.
> No extra material is needed for fore/aft loads, the existing
> dimensions and laminates are enough to take care of these. True about
> the forebeam and mainsheet track but these are no heavier than the
> heavy balestron boom. Not having so many mainsheet control winches on
> a proa is a big plus.
> The forebeam then needs a
> > lot more hull height to keep it out of the waves. Not only heavy and
> > added windage, but it is in the extreme bow of the boat adding to the
> > pitching moment.
> Agree with this. Not having a fore beam and tramp is a great safety
> advantage and Harryproas certainly pitch a lot less than cats.
> > Harryproas have a simple stringer along the deck and the keel between
> > the beams. Maybe another 10 kgs.
> Modern cats don't have any stringers along the deck but do have souls
> and webs to walk on. Proas require an extra layer of glass over the
> leeward hull between the beams to take the mast loads, about 50kg.
> > 3) Cats, especially those with the user unfriendly 3 stay rigs also
> > need considerable structure to support the chainplates. Minimum is a
> > decent thickness half bulkhead, solidly glassed to the hull and deck.
> Most catamarans use an existing bulkhead to attach chainplates with
> some extra reinforcing.
> > Harryproas don't.
> > 4) The cat needs beefing up of the cabin top to take the headsail
> > track loads and the winches for the sheets.
> Not really much beefing up. A well designed saloontop with enough
> glass and thickness to support walking on will be enough to take the
> jibsheet loads with maybe an extra layer around the jib sheet track.
> Again, not having winches is a big proa benefit.
> > Harryproas don't.
> > > Also weight isn't necessarily a big factor. Where a proa saves
> weight is in not having so much material as they don't have such an
> extensive fitout, and not so much solid bridgedeck and saloon. I think
> a proa built with the same accommodation and appointment as a cat will
> weigh about the same.
> > Weight is a huge factor. Blind Date has 2 doubles and a single berth
> > with space for 2 more single cabins , huge deck space, covered
> > cockpit, galley, large nav station and toilet. It weighs 2 and a bit
> > tonnes/tons in sailing trim. There are no catamarans with similar
> > usable space that are anywhere near this weight. Lower weight means
> > smaller motors, smaller rigs, higher speeds, lower build and
> > maintenance costs, less to paint, easier to haul out, etc etc.
> Blind Date is a very nice boat and very light but it is also very
> basic with no saloon and very little deck space, being mainly tramp,
> one outboard, no anchor winch etc. It would be more appropriate to
> compare Rare Bird which weighs 3.7 tonnes empty because it has of a
> fitout more similar to a cat, though still only one hull fitted out.
> My original comment was to say a proa with the same level of fitout
> doesn't have a huge weight benefit. Put the same fitout of the typical
> cruising cat on a proa and it would be a dog and may not even shunt.
> Proas need to be kept light so they can take advantage of their
> waterline length of the leeward hull and not bog down their fat
> windward hull. Keep them light and they are magic.
> > The owner and I are working on tenders to build a 60' charter proa
> > optimised to take advantage of the proa and unstayed rig benefits.
> > The shell, bulkheads and beam materials are a touch under 2 tonnes
> > based on surface areas and laminates. This boat has 4 double cabins
> > (2 with island beds) each with a toilet and shower, a huge saloon and
> > covered deck space, plus enough cabin top to mount enough solar panels
> > to power the electric motors. Ready to charter it will weigh and
> > cost less than most 40' cats and outperform most 60 foot cats
> > according to the same spread sheet that accurately predicted Blind
> > Date's weight,.
> That will be very impressive if it can be achieved.
> > >Where a proa gets it's performance is in the extra waterline length.
> > It's pretty pointless comparing proas with cats as they are such
> > different beasts fulfilling different rolls.
> > The harryproa role is cruising comfortably and safely for a given
> > price . Most cat owners would say the same. Harryproas do this
> > extremely well. Look at http://www.youtube.
> > Has anyone sailed on a cruising cat at 15 knots boatspeed in 15 knots
> > wind speed in such comfort with such low stress? Mark Giles, who has
> > test sailed a lot of cats (and one harryproa) for Multihull World
> > magazine hasn't. The cat fulfills this role comparatively poorly,
> > unless the comparison is with a mono.
> Rare Bird is a joy to sail as are all the Harryproas I have sailed on.
> Nobody is disputing that.
> > Waterline length is part, but not all of the story. Other important
> > factors are:
> > The reduced drag from not having daggerboards and their slots.
> > Reduced weight and windage of superstructure that isn't compromised
> > for rigging loads and daggerbboards.
> > All the weight concentrated in the middle of the boat.
> > Higher righting moment for a given weight.
> > More efficient hull beam to length ratios.
> > Better rigs.
> > Superior hull forms (no rocker, high prismatic) which are not
> > compromised for tacking.
> As I said, cats and proas are very different beasts. Harryproas have a
> lot of great advantages which is why I like them so much, if I had the
> money I would buy Rare Bird tomorrow.
> Speaking of which the estate is desperate to sell Rare Bird. Anyone
> interested in making an offer approaching $200,000 would land them
> selves an absolute bargain and own a very special boat.
> All the best and goodbye,
Comparing cats to proas using cat's layout and structure as the
benchmark is a flawed premise. Modern cat layouts are the end result
of minimising the effects of the extra structure they contain.
Cats have to have high bows to keep the forebeam and tramp out of the
water. The marketing people point out the full headroom throughout,
despite the fact that it is the most uncomfortable place on the boat
and huge and unnecessary weight and windage.
The same applies to the substantial mast bulkhead being used as a
cabin wall when a lightweight partition is all it needs to be and that
this is a lousy place for a bunk. Ditto the chainplate bulkhead
doubling as another cabin wall and the massive traveller beam required
to sheet the main being used as the back of the cockpit, when a simple
rail or seat would suffice.
and so on.
If, instead of assuming that the current breed of cats cannot be
improved (They can, a lot. There may even be a harrycat in the
pipeline!) we compare them on suitability for purpose, it is a more
useful comparison for the end user. It is also much easier as we
have live examples to compare, rather than trying to sort out such
nebulous concepts as the "same accommodation and appointments"
For example: XL2 is a very fast racing cat (ex Brisbane Gladstone and
sundry other race records) on which I have done a lot of miles.
Crowther design, open bridgedeck, foam and vac bagged light kevlar
skins, nothing superfluous, no saloon or table. 38'/11.3m long, 9.9
outboard motor, porta potti, no anchor winch, it weighs 3.2 tonnes
ready to sail according to a load cell, as opposed to a designers
This compares with 2 and a bit for the 50' Blind Date, measured on a
load cell, then confirmed on another as no one (except me) believed it
could possibly be correct. XL2 struggles to do 15 knots in 15 knots
of breeze (Paul?) under working sail and certainly would not do it
with the sail shapes on Rare Bird (a simple fix, just not one which
anyone has done) or with as little effort or as much crew comfort.
Blind Date is 65% of Rare Bird's (the harry in the video) weight so
will be faster and more comfortable.
Mark says Blind Date has no saloon. What he meant is, it has no
saloon crammed into the middle of the very solid bridgedeck, with
curved seats which are impossible to sit or lounge comfortably on, and
a table with access from only one side at which only 4 people can eat
comfortably. Blind Date has seating for 8 around a huge table
accessible from either end. It can be under cover, or remove the
large overhead hatch and sit in the sun. Clears would make it
weather proof, but at sea or on the anchor, nothing comes in the open
side so it is not a problem. It is about designing for the required
purpose, not just following what everyone else is doing.
Mark also says Blind Date has little deck space. He should sail on it.
It has enough deck space for 8 blind people to move around on to
sail and operate the boat, without bumping into each other or the two
crew. Much safer and more user friendly than a bridge deck cat.
To say that Blind Date is light because it only has one motor and no
anchor winch misses the point. It is the user friendly layout and
minimalist approach to the rig and hulls that leads to the lightness.
It only needs a single motor as it can move almost sideways with the
single motor and the twin rudders. It is light enough, with low
windage enough that it does not need an anchor winch.
Stating that a proa with all the unnecessary (for a proa) weight a
cat carries "would be a dog and may not shunt" is an interesting
comment from someone who has sailed harryproas maybe a dozen times.
Suffice to say that this is a most peculiar argument, and as far as I
can see, incorrect. The closest I have come to it would be sailing
Elementarry with 4 people on board, all sitting on the windward hull.
This gave a boat weight of 130 kgs and a load on the windward hull of
about 200 kgs. Equivalent to Blind Date with 3 tonnes in the
windward hull, making it 5 tonnes all up. Shunting was effortless,
speed was down, but not by much. We all got a lot wetter than
normal.. Put 150% of the all up weight in one hull of a cat and I
suspect it would be a bit difficult to tack. A peculiar argument,
Saying they "need to be kept light" shows a lack of understanding of
the dynamics. Put the extra weight in the leeward hull and it will
go slower, but still faster than a similar weight cat. You will still
have the designed righting moment and the structure will not be
overloaded. Unlike a heavier than designed cat.
The difference in weight is made up of all the "just a bit here", "not
really much", "true, but", "not very heavy", "maybe an extra layer"
and similar comments in Mark's post. Being lighter and faster than a
mono is pretty easy. Being as light and fast as you can be, is a bit
more of a challenge.
The bottom line is pretty hard to disagree with. The level of fit out
on Blind Date is sufficient for 4 adults and 4 kids to cruise in for
their annual holidays, or 2 crew and 8 blind people to enjoy day
sailing on, including sit down lunches. Most 40' cat designers would
love to say the same, but are stuck with how many toilets they can
cram into otherwise unusable spaces. The fact that they struggle to
manage it in a 4 tonne boat, and certainly not in a two tonne boat
should be enough of a comparison for anyone interested in fast, easily
By the way, Rare Bird weighs 3 tonnes empty, not 3.7. And is
definitely a bargain at $200k.
Good advice Mike, let's hope the personal is kept out of it. And
thanks Doug, made me smile on anotherwise trying day.