Seaworthiness

There are more ways to design for impact resistance than traditional heavy hulls. In my preliminary design concept for my own cruiser, all of my tankage is low profile integral tanks built below the waterline. (as part of the hull). In addition, integral water ballast tanks allow me to adjust moments of inertia for various conditions, to alter pitching and rolling; and of course to reduce heel angle. If properly designed and built, this concept provides a double hull below the waterline to help protect in the event of a hull breach. Although I don’t think it could be considered ULDB, the overall design can be considerably lighter than, other traditional methods of construction, especially when coupled with water ballast. The dual purpose use of tanks helps defray the cost (in terms of dollars, and weight) through the efficient use of materials. This isn’t a new concept of course, but more precisely an extension of an old idea to include water ballast and double hull construction below the waterline for extra protection, and flexibility in design.

 

Here is what the designer of the Pogo has to say:

The work achieved by skippers, builders and designers makes it possible today to cross the Atlantic single-handed in just over 8 days. Everyone can now dream of playing with the wind, the sea and the waves.

Still, we are worried about imponderables :
Lexibook, Hervé Papin’s Pogo 40, hit a container at 10 knots, causing the boat to halt suddenly. The outcome was limited to a big scare and a dent at the front of the bulb, and both boat and skipper were able to carry on with the race.

In the same vicinity, just a few hours earlier, in a strong, gusty wind, TMI Technologies, Joe Seeten’s boat, was sailing an average 17-20 knots, when it stopped extremely violently at the bottom of a wave. « Something extraordinary » even for Joe’s extensive experience. Did he hit a floating object, an animal or a rogue wave ?
Joe, thrown by the shock to the opposite side of the cabin, broke his shoulder and cut his forehead. The water was rushing inside the boat when Joe noticed that the bond between the keel and the boat’s structure had been damaged. A few hours later, he was rescued by a cargo ship.

Passive security systems performed perfectly, especially the buoyancy volumes, with the boat floating even with 50 cm of water inside.
The builder, and us designers, permanently wary about the strength of our boats, apply safety factors twice superior to those usually recommended by standards and norms. Nevertheless, we are still left to wonder if these precautions are sufficient enough considering the high speed these boats can reach nowadays.

It is necessary for everyone to consider that no one is safe from risks at sea (floating objects, waves too large for the boat past a certain speed)
It would surely prove an excellent idea that skippers, race promoters, builders and designers get together to give this a constructive thought…"

Groupe Finot

(bold mine)

10 knots and 17-20 knots ... One continues the race, the other didn't sink and the injured skipper was taken off.

Seems that the designer has some concerns and tries to design extra strength into the boats "just in case". It also appears that they have made a good job of it ... and they did it in a 4800 KG 40 foot boat. Maybe the designer knows just a bit more that the people that say a boat must be heavy to be strong? They also managed to build and sell it for 125,000 Euro, the defense budget of a very small contry.

 

Randy,
I would like to know how they manage to get that D/L ratio under 85. It is usually asumed in the industry that for usual construction materials and techniques, for an all around cruising design, is difficult to get a figure under 200. We can go somewhat lower than that, certainly, but....85?

Let's have a look at some intimacies of her basic specs:
(taken from: http://www.pogostructures.com/files/Pogo_15-9-2006_16:43:58.pdf)

Hull in GRP made by infusion with multiaxial glass tissues
Deck in PVC foam sandwich, glass, polyester made by infusion
Structure in GRP/PVC foam made by infusion
Buoyancy, 3m3 in close cells foam.

Carbon mast autoclave cured prepreg , 2 aluminium spreaders levels
aluminium boom, carbon bow sprit
monotoron stainless steel riggings, textil backstay and babystay,
vane, spectra halyards, deck sheets and ropes spectra and polyester

Deck hardware Harken, Wichard, Frederiksen (including spinaker items)
Spécific stainless steel ironware
Pullpit, pushpits, stanchions, all chain plates
Goiot portlights and hatches, GRP hood, lifelines, deck cleats

Keel, 2 draft choices : 2,20m or 3m
High strenght iron fin with GRP outline shape
lead bulb
Rudders blades in GRP with high strenght stainless steel rudder shaft
Spheric bearings with needles in the bottom one
Carbon tillers

Water ballast system 2x750L, filling pump, transfert knife valve

Inside fitting
Central charts tables / kitchen with cooker and sink
3x20L water tank, WC, tissue doors, cushions

Engine 30 hp VOLVO Sail Drive,
battery 55 Ah

No info on fuel storage

From my point of view this spec is a very scarce one. Accomodation looks very spartan (as per images and spec) and provided water tanks and battery capacity seem clearly insufficient for serious cruising. So it keeps looking to me what it always has: A boat conceived for exilarating short term coastal cruising, with no much more personal equipment that your swimsuit. A nice boat for that. Occasional quick, light crossings with short crew are possible, indeed, but, again in my opinion, that's its most.

What happens if you load it with all water, fuel, stores and personal items needed for a 6 people crew for, let's say, an atlantic circuit (europe, canaries, caribbean, bermuda, açores, europe)? Not to talk about those hundreds of kilos a cruiser accumulates of books and souvenirs from visited ports, or either high latitudes cruising equipment. An this not only from the point of view of performance and seakeeping abilities, but also from the point of view of possible structural overloads.

And, what about materials fatigue? Properly cruising purpose built and reasonably maintained 'slow' heavy/medium-weighters have been around here for decades in a healthy condition, even if severely punished. Are these fancy extra-light designs going to be there in, let's say, a 30 years time of globetrotting? or, at what cost? I would like to know.

On its price: Total EX-WORKS price excluding taxes is 145876 euros, for this very, very basic spec. Even CE mandatory items such as the holding tank or bilge pumps are optional. So, what's the final price for cruising mode? Adding items from their option list I come to a figure of 186.973 euros with the medium priced electronic package, but some items' prices seem not to include installation. Knowing what I know after having purchased several boats myself, having had several responsibilities at pleasure boat yards, and after quite some surveying and appraising activity, my opinion is that Pogo's cruising 'go sailing' price may very well be around 200.000 euros, ex-taxes (+/- 250.000 USD). And this without sails. Nor personalized caprices.

Has somebody asked for a quotation?

More:
"Lexibook, Hervé Papin’s Pogo 40, hit a container at 10 knots, causing the boat to halt suddenly. The outcome was limited to a big scare and a dent at the front of the bulb..."

I would like to have had the opportunity of performing a thoroughful inspection to the hull and structure at the aft end of the keel-hull joint. I have my doubts.

Cheers.

 

What's the size of your design?
Cheers.

 

Good grief.

 

Guillermo,
If the budget pans out, between 70 and 80 feet(21 to 24 meters)I'm a ways out before I can start construction. In the mean time I have much studying to do.

 

It's an interesting study, but it deals with a very unusual style of boat that has a very unusual motion in any case. Australia II was well known to have had poor motion due to excess weight in the ends (ie the end of the keel) compared to other 12s. This was noted before the boat even arrived in the USA.

And I think we can safely say that none of the other 12 Metre design/test teams, who would almost certainly have spent vastly more time and effort in testing their designs than the Stevens Institute, ever tried to increase the weight in the ends. The "Glassgate" incident in Perth 1987 was mainly about the fear that other syndicates had that the Kiwi GRP boats had superior weight concentration. This is spelled out in the Farr/Bowler bio and Conner's "Comeback" as well as contemporary sources.

If the Stevens Institute study is right, then just about every other designer and study team, and everyone who has written a book on sailing, is wrong. Connor and the Kiwis and the USA II team and Blackaller's designers like Mull, and the other 12 or so teams, would all surely have spent multiple times as much in tank testing as the Stevens team. It would be surely highly unlikely for the Stevens team to be right and everyone else to be wrong.

Wasn't Mariner the result of a Stevens testing programme?

In some conditions, yes the higher gyradius can be faster as is generally agreed.


GUILLERMO

I agree that the tankage of the Pogo is extremely light. However, not everyone cruises in the way that most people do. Some people DO cruise on extremely light boats, like the French couple who have been sailing around the Pacific for a decade on Accanitto, a lightweight almost flush-decked stripped-out IOR machine with tall fractional rig, in-line spreader and runners.

I have spoken to them about the boat and they love it. It suits them. Surely the Pogo style could suit similar people.

PS I regularly hear about the way lightweights lose performance radically when overloaded. I don't actually see this very often. One recent example was the last Mooloolaba race here, where some boats continued on for about 900 miles more after crossing the finish line for a 430 mile race. The guys on boats as light as Farr 40 ODs reported no major loss in performance from the extra food and water for 900 extra miles for about 10 men. Similarly, I have yet to hear of anyone using lower target speeds at the start of a Sydney-Hobart, when boats as light as 2,500kg are carrying supplies for 6 men for 7 days.

Sure, cruisers carry more than this in overload. But having done things like live ab aboard (and race) a 2,200kg 8.5m boat and raced a few boats of similar weight on long races, I wonder whether the lightweights really do lose much pace when loaded up.

Pic is the lightweight Sayer designed- and built- 11m "Belle" coming over a bar in Queensland. No damage, I believe. Not all lightweights are fragile.

 

Behind ISO 12217, (the one that certifies EU boats on the different categories) is ISO 12215. This is the one that certifies that the boat pass the structural demands to be approved by ISO 12217. Among many specific demands the ISO 12215 demands on scantlings a safety factor of 2.3.

ISO 12215 follows ABS another Classification Society Code. Prof. Paul Miller considers that a boat that is made under the ABS code is fit for offshore work.

In the keel area the safety factor of Pogo is 6. This factor is only found in some racing boats, and not many.

They are going to improve on that safety factor, making it even bigger, in what should be a record in the industry.

Why?
I believe that the description made by Rhoug, quoting, I believe, the manufacturer is not entirely correct. I had read the description made by the skypper and he had said that after being suddenly stooped at the bottom of the wave, the boat was caught by a huge breaking wave and dragged violently sideways (a situation that would have rolled a traditional boat).

It is believed that it is this fast sideways movement that can jeopardize the keel integrity (unless the boat had hit something). This is a situation that is new (other kind of boats roll) and the keel is theoretical good to stand a sideways movement of 25K. But we know that sometimes things don’t go as predicted and they are improving the safety factor.

None of the 25 boats have been capsized on those big storms on the “Route du Rhum”, but several had been caught by big breaking waves and experienced a big lateral slide.

About cruising, in what structures concern, the demands for racing in extreme conditions are much bigger than the ones needed for cruising, even with a loaded boat. Safety factors in boat structure of a racing boat are incomparable bigger than the ones you use in a cruising boat.

About the seakeeping abilities while loaded (cruising) you have seen that the boat has a bigger STIX when loaded, and we have seen that the boat has a very good load capacity. So if the boat is not loaded over its Max load capacity, regarding seaworthiness, it would be more seaworthy than in Light condition, but probably, not as fast.

 

I thought so. You need big lengths to arrange DWL level 'double bottom' tanks and then a decent room height.

For sure, but I'm talking about 'average' cruising people.

In my opinion, what could be a first approach to a modern nice '40 ft trotter cruiser' for the average people and all around cruising, is a boat more or less like the following:

Loa (Lh) = 12,00 m
Lwl = 10,71 m
Bmax = 3,24 m
Bwl = 2,90 m
Draught T = 2,06 m
Body draught Tc = 0,60 m
Disp (light) = 8000 kg
Disp (loaded) = 10142 kg
Ballast, fix = 3600 kg
Sail area = 75 m2
Engine Power = 30 KW
Heeling Arm = 6,90 m
Wetted Surface = around 30,00 m2
Angle of vanishing stability = around 130 deg
Downflooding angle = not less than 105 deg
STIX = 39 - 40
Negative GZ area/Positive GZ area = not bigger than 20%
LCB around 0,38 m aft of mid section.
Cp = 0,59

Cutter rigged.
Bulbed keel (not extreme).

How about that?

 

This one seems to meet your criteria. A little bit lighter (200kg) a little bit narrower (6cm). It is a luxury Danish cruiser, bought mostly by Swedes and Germans. It has 140 AVS, very small inverted stability and a Negative GZ area/Positive GZ area smaller than 20%.


I find it a very nice oceangoing cruiser. What is your opinion about it? (I like other kind of boats, beside beamy boats ).

http://www.nordborg-baadbyg.dk/da/index.php?B%E5dtyper:Nordborg_40:Tekniske_data

 

Very nice boat, Paulo, much in the line of what I'm talking about. Thanks.
A cutter top masted rig would be more appealing (safer) to me, from an all around cruising point of view.
Cheers.

 

All valid points Guillermo.

Rather than compare the Tankage etc. to other 40 foot boats. Compare it to my 30 foot of about the same displacement.

The Pogo carries almost exactly the same amount of water and fuel as my Catalina 30.

The C30 empty is about 4800 kg with D/L 300.

The C30 would be very hard pressed to accommodate 6 crew for an Atlantic crossing also. Both boats are equally able as far as stores capacity.

The big difference comes with cruising speed. 3000M at 5 knots means the C30 must have stores for 25 days. 3000M at 8 knots means the Pogo must have stores for 16 days. 9 days of Water, Food, and Fuel is ??? pounds per person? 10 pounds per person per day?

If, the C30 has the ability to make crossings (it does), then the Pogo can support the same number of crew, since it's capacities are similar to other boats of the same displacement.

I know that a 5000kg boat has room for more than more than just a swimsuit, but I may save this post and use it as an excuse to limit the gear that female crew can bring on-board ...

I will be visiting the yard in July. If I like what I see, I will most likely take an option for 2009 delivery. If I have misgivings about the build quality or scantlings, I'll pass.

As far as the interior goes, I like the look. I'm not in love with high maintenance wood interiors. The cruising version has just enough wood (cabin sole and nav station) to make it look almost perfect to me. I agree that the canvas "door" in the head and no door for the other cabins is a bit spartan. However, I place a higher priority on sailing performance than on luxury interiors. Those that buy Shannon's (at $600,000+) have different priorities. The one glaring omission in the interior is a lack of a hanging locker. Hanging lockers are of little value under sail (the boat's motion chafes the clothes), but are wonderful when living aboard in port. The head is well placed (close to the companionway) and is the logical place to hang wet gear at sea. In port, I don't care to live out of a sea bag, so some portion of the load budget might go for storage.

I'll agree that if you are planning to spend years cruising (that means 80% of the time in port and 20% of the time at sea for many), your boat must look more like a house. My idea of cruising is 80% sailing and 20% in port. Coastal cruising here is mostly 25-50 mile day sails, anchoring out sometimes and making it into a harbour with laundry and showers every few days. You might spend a week in one place, but not often. As Guillermo says, the Pogo would be great at that.

Wench won't be making long passages with me, or living aboard for extended periods, so we don't need a boat that fits the 80% in port living aboard, 20% sailing that I agree make a good traditional cruiser. I think the Pogo will be a very good fit for our cruising plans.

I don't think that boats like the Pogo are a good choice for traditional cruisers. I think that there is little doubt about their seaworthiness.

 

Our fellow Pericles passed me an info on another keel lost related accident, this time in the UK. Thanks a lot Perry.

"A man in his 20's died and four other crew members were rescued from a life raft after the Hooligan Five sank on Saturday at Prawle Point near Salcombe.
The Marine Accident Investigation Branch will look into reports that the boat capsized after losing its keel...."

See: http://news.bbc.co.uk/2/hi/uk_news/england/devon/6329071.stm

Once again. Too many accidents related to keel loses, lately. Why?

 

Randy,
Let me quote you from another thread:

"Another interesting data set is:
1851 America, 0.70 S/L average
1866 Henrietta, 1.00 S/L average
1931 Dorade, 1.14 S/L average
1955 Carina, 1.18 S/L average

Compare these boats and numbers to the numbers posted in the S-H this year:

Ichi Ban, 1.23 S/L
Wild Oats, 1.11 S/L
Love & War, 1.07 S/L
Skandia, 1.04 S/L

Anyone care to try to put this in a light that shows great progress since 1931? Are the new boats more or less seaworthy than Dorade and Carina? Are they more or less seakindly?"

I would like to know your own answer.
Cheers.

 

It's statistically wrong to use one race, or a limited number of figures, to try to prove that old boats are fast. It's about as statistically valid as saying that because the plumber who just came to my place had a blue shirt, every plumber in the world has a blue shirt.

This year's Hobart was a notoriously slow race. To compare an upwind bash to largely downwind races is not valid. "Great progress" is not defined, however many advocates of heavy displacement complain bitterly when the rating rules supposedly disadvantage their favoured craft a minor amount, so "great" is obviously in the eye of the beholder.

The latest Sydney-Hobart provided ideal conditions for the 47 foot Love and War. Despite that, she was 1 knot slower than the state-of-the-art (non radical) IRC boats a foot or two shorter. She was beaten across the line by 9 hours by a Swan 45, a luxury racer/cruiser. She was 1/2 knot slower (7.3 v 6.8) than the first Sydney 38, a cheap one design racer/cruiser. She was beaten by cheap cruiser/racers like Beneteau 44.7s, by 40 footers, 42 footers, 43 footers, and 38 footers.

Love and War succeeded not because she is faster than modern boats; she is not. She succeeded because the rating rule recognises that she is a heavy old boat and therefore gives her a much lower rating than new boats get. Given normal conditions she is much more than 1 knot slower.

As has been pointed out here several times, new boats ARE faster than old ones. Even in the most advanced of sailcraft, speed advances are not always spectacular. The foiler Moth has advanced about 35% (approx) in speed since 1930, in the change from planked scows to carbon foilers. Merlins and National 12s (development class dinghies) have advanced something like 1% per decade since the '30s and '40s. WIndsurfers have doubled in top speed but the modern speed boards cannot actually sail properly in light winds. In light winds the original Windsurfer is faster than many modern boards. In small cats, the Tornado was the fastest boat (apart from the rare C and D Class) in the '60s, in 2007 it's still just about the fastest thing.

The other forms of sailing aren't being transformed with speeds 50% or 200% greater. Why people expect displacement-style rating yachts to improve their speed at a rate that is faster than any other craft is something I cannot fathom. Since about 1973, rating monohulls have increased in speed about 13%. That's respectable compared to typical beach cats, restricted development dinghies, windsurfers in average winds, etc.

Re Dorade. Easiest way to look at her real performance is to look at Stormy Weather which was a faster update. She has raced in Fastnets recently, went faster than she did when she was young, and was well beaten by much shorter modern yachts. Put Dorade up against a modern raceboat (rather than comparing her decades and thousands of miles apart) and she will be beaten handsomely.

I'm not sure if the '55 Rhodes Carina is still racing. Similar vintage Rhodes designs are still sailing; for example an Offshore 40 put out a Mayday in the NZ-Tonga rally (one of those events where heavy cruising boats rolled and put out maydays en masse) and a sister won the 2000 Bermuda race. She rates about as fast as a modern 25 footer. Once again, NOT a fast boat by today's standards but successful due to her low rating.

America and Henrietta are no longer racing, of course. Big boats like the J Class and the 140' schooner Adela are rated IRC and rate slower than modern boats 50% as long. If the rating was innacurate, the big old boats would beat the small boats on IRC. They don't. The IRC rating is fairly close to reality, and the big boats are as fast as modern 70s.

I've raced 12 Metres; great old boats, but slow by today's standards and struggling to keep pace with boats 20 feet shorter.

I know people, extremely experienced people, who maintain that newer boats ARE as seaworthy and more seakindly than earlier boats like their 1950s Arthur Robb long keelers; their steel double-ended Halvorsens from the '60s; their timber S&S classics from the '60s and '70s; or their Frers boats from the '70s. I for example hate the motion of Finnisterre types, Malabar yawls, Swanson double enders, etc. They have greater amplitude and go slower and take lots of water over the deck in my experience. That does not suit my own taste.

Years ago I did an article on sailing techniques for older boats like '70s S&S designs. The top sailors I spoke to emphasised how important it was to keep weight out of the ends, because those old boats (with their fine sterns) bounced more (albiet slower) than new boats and that slowed them down notably. That may not be everyone's version of seakindly.