Hi All,
It has been put to me that my last two posts have been anti Harryproa
and that I have damaged my credibility by a sudden change of view.
This is certainly not the case. I have spent many years developing the
Harryproa concept and wish to see it flourish, I was merely pointing
out that I needed to make a living which wasn't possible with
Harryproas so had to move on.
My answer to Robert Dalton's post should not be taken as promoting the
catamaran over the proa but a discussion of whether a proa is
inherently a lot lighter than a catamaran, all else being equal.
Pointing this out is not saying the boats are no good. The
fact that I am now designing catamarans is irrelevant to the
discussion, both types have their merits and downsides and I don't
have a preferred loyalty to one or the other.
Rob has requested I not make any further 'negative' comments on this
group. I believe that a discussion group should be open and free to
express an opinion without it being seen as disparaging; a discussion
group that only allows the views of the moderator is of little value.
As Harryproa is now Rob's I will honour his request and
not make any further posts. I do reserve the right of reply to Rob's
last post and hope it is seen as a useful discussion.
>
> 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.
Other
> 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,
Mark
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