A bluewater, ocean going water ballasted matorsailer. Why not?

Did I say : I like to quote Paul Ricchelli?

signed
a "semiprofessional"

 

Par, you really don t get it, do you. There are some truly fine motorsailors available, manufactured by respectable companies that are dying every day like the soldiers in the western front, because nobody buys their fine product. ( I have a friend with a 165 sailing yacht that exceed my expectations without water ballast). You obviously have no financial knowledge or stake in the motorsailer market, so frankly you are just typing for entertainment value.( So do I ! ) There are many well executed customs and semi customs out there, that are waiting for clients to buy them, but the clients of the old heavy slow motorsailers are born ages ago, so now they don’t buy them as they themselves are also dead and buried. Maybe you d be better off talking to a local distributor of a motorsailer and get a clue about the past and the future of the motorsailer market, because frankly your arguments ( that the grandmasailers you think are the last and final evolution stage of sailing motorboats, something like the wheel), have little merit. I would think this more fruitful than attempting to persuade starving professionals and semi professionals within the vanishing industry that your little understanding of the shortcomings of the old motorsailers ( and of the possibilities of novel types of sailing motorboats) is going to pay them the rent. You could better start reading about the complex hydrostatics of modern self righting water ballasted lifeboats, starting from your little understandings of the 3000 years old principle of Archimedes in his second book : ''On floating bodies.'" I suggest you first read the relevant article of Chris Rorrer
http://www.cs.drexel.edu/~crorres/
http://www.math.nyu.edu/~crorres/Archimedes/Floating/rorres_paraboloids_MI.pdf
to try to understand the issue even in the simplest case of a paraboloid, then proceed to the self righting mechanism of the Oakley Class lifeboats, then to 47 ft MLBself righting capabilities
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA247184&Location=U2&doc=GetTRDoc.pdf
and then, dear PAR, we can both start trying to get it!
Doubt is unpleasant, but certainty is ridiculous. Have a little, just a little doubt when you are approaching something new. Your extensive knowledge, which I do not question of course, is going to acquire a broader base. No hard feelings ! I tried to answer in your style.

 

Thank you White Wolf,
Yes, this is a young motorsailer ! It could possibly open a new market. Very low ballast ratio, a hybrid keel ballasted/water ballasted craft like the one TeddyDriver is saying he is building in post #3. I find it quite heavy and luxurious for my taste, though. I want MORE speed out from a 50 ft sailing motorboat, because otherwise PAR will tell me to just buy , with less money, his friends 65 ft grandmasailer that goes 18 knots too, and he would be right this time...

 

Let me summarize the issue in a different wording.
Motorsailers are beautiful ships that offer as much as possible of both words, sailboats and motorboats. For some people the whole is more than the sum of the parts. For some other the limitations of each part are doubled in the whole. The truth is that, with the coming of modern materials and powerful engines, the motoring speed of the motorsailors does not satisfy a great number of people, especially the young, because they live in an epoch where speed matters. This is probably the main reason behind the sad fact that very few companies are manufacturing very few motorsailors nowadays, while the motorboat market is booming. The bigger companies, many of which produce sailboats and motorboats, ( like Beneteau, for example ), are left out of the shrinking motorsailer market, which is served by very few small yards, unable to develop the concept further or to reduce the cost.
There is an obvious way to achieve greater speed, that is taken in both the sailing and the motorboat word. Multihulls. Multihulls have many advantages, but two shortcomings which are very serious for a number of people : They are not self righting, and they pay expensive marina fees. If one ignores these two factors, the simpler and cheaper way to go faster is a cruising multihull.
Self righting ? What does this term remind us, except monohull sailboats? Lifeboats, of course. And modern lifeboats achieve self righting in two ways. Either they use a water ballast system ( invented by Richard Oakley ), or they use a high raised deckhouse.
It is a small step from here to ask ourselves the question of this thread : Is a water ballasted motorsailer, lighter and faster than the traditional motorsailer, a bluewater self righting vessel just like the lifeboat, a viable alternative ?
The great majority of people in the sailing world, expert sailors with millions of miles sailed and expert naval engineers with millions of tons designed, are getting angry, some even mad, when they listen of water ballast. They are conservatives, and they are right to be so. Experiments are deadly in sea, and there were deadly experiments with poorly designed water ballasted sailboats.
But the scientific mind is not trapped in the past experiences of the laymen or the present opinions of the experts, it does not obey majorities and authorities, and scientific knowledge is the fruit of the doubt.
A similar issue was raised when a small minority of sailors and designers decided that another way to increase speed, other than the very long multihulls, is by lifting the hull above the surface and the waves, by using foils. The idea took almost a whole century to evolve, and part of the delay was due to the majority of expert sailors and the majotity of experts designers conservatism. But now the older and most prestigious sailing event, the America s cup, is raced by foiled multihulls that combine both ways.
I think that by combining both ways of self righting in the lifeboats world, water ballast and high raised deckhouse, one can achieve self righting even in the more difficult case of a sailboat, where the appendices add harder obstacles. In one hundred years the sailing motorboats would be different from the today’s motorsailers. And who knows ? May be they will be using water ballast and high raised deckhouses. We will not be alive to tell who was right....

 

Interesting thread. Water ballast has been discussed at length before in this forum, and no doubt will again. It is an alluring concept that seems to make a lot of sense.

Because of water’s tendency to slosh around, only a full or empty tank is stable so using it to actively control heeling or vary displacement requires multiple tanks. That stuff can go wrong at sea, halfway through a water-transfer operation for example. Imagine trying to fix a system that’s open to the water and below the waterline during a major storm, with the boat heeling in the wrong direction, in the dark ... let’s see, that’s one hand for yourself, one for the flashlight, one for the tool and er ...

What happens if you add side tanks? If you add them externally, that’s the same as adding them internally in a beamier hull. The hull is more stable with the tanks empty if they are above the center of gravity, as is likely. Whatever righting moment can be achieved by filling a side tank, more be provided by a chunk of metal at the bottom of the keel, which is always where it’s needed.

Add an external tank under the hull and nothing happens to the stability, it is only neutral mass, all that has happened is the wetted surface has increased. Pump it dry at your peril though, the boat’s stability will go down alarmingly. You could drain it for trailering, other than that or one some special purpose vessel, it doesn’t seem worth the trouble. Trailering seems an unlikely option for a true ocean-going boat, more of a day sailer requirement.

One place where water ballast might be useful would be in a raid boat: use the ballast for sailing, a self-bailer gets it out again ready for rowing - or keep the ballast for rowing if the added inertia helps punch through waves.

I strongly recommend trying the idea out first in a model. Cheaper, quicker, and nobody gets killed. Why not put the into effort designing and building a ballasted keel that can be raised for shoal conditions and maybe motoring too. If it gets jammed, you can still motor with it down or continue with reduced sail.

 

Personally I prefer the water to be on the outside of the boat. There was this one time when...

 

LOL I finally get what Xan is trying to do here, and I am going to have to agree with him. What we need to do is get the designers to stop worrying about what they know and design what I want regardless of the conventional wisdom, testing, or experience. I know this will work, because I would like it to, and certainly the laws of nature will bend to my will.

So here is the design spec for our new Motorsailor...

1) Must motor as fast as now available powerboats. Since we want this to be the best, lets use large twin hull ocean going racing boats as the start. So our boat should have a top speed of 100kn or so. But we want it to be self righting, so get rid of the cat design, and get the same speed out of a monohull.

2) Add to this the sailing ability of a foiler 100' Trimaran. So under sail it should have a top speed of say 40kn as a baseline, but lets hope we can get it to go faster than that with practice.

3) Remember this is a motorsailor, so it must also have volumous interior volume ready for long distance cruising. Lets say 2,000 sq foot in the 50' model. We may need it to be 3 stories, buts that's ok since high bridges are good for self righting capability.

4) Lead ballast is heavy, so all ballast must by from internal fluid ballast systems. Water is prefered over something that could actually help only because getting murcury in this large volume is hard.

5) Keep the entire price in the $2,000,000 range since it needs to be affordable.

6) With the foils down we still want to be able to cruise shallow water so it can't be deeper than 24" at 50'.

7) This is a Bluewater boat, so it must be able to roll through 360 degrees with no damage

8) Remember operational costs must be kept low, so under power it must get at least 10km/gallon of diesel.

The only question I have is would it be possible to make this trailerable, preferably towable by a Geo Metro?


So here are the design specs for the boat, now I know people are going to say that it is impossible. But that is just because they are blinded by their knowledge, while I who have no degin experience or scientific knowledge know it must be possible because otherwise I couldn't have what I have always dreamed about. As we all know science must bow to the desires of man, and the refusal to recognize this fact simply proves that the people refusing are blinded by the incomplete knowledge they have, and fail to recognize the potential for advancement by pushing the envelope.

 

Thank you ancient kayaker,

Could this tendency be contained to acceptable level through the use of compartments within the same tank?

The water in the tank below the waterline is released to one sidetank through a system of automatic valves only when the boats is laying upside down. The floating of one side tank changes the equilibrium of the boat. Of course, the weight of this tank, always filled with water, increases the wetted area of the hull. But not so much as a lead keel, which was used in the older lifeboats in nineteenth and early twentieth century. This was the system of the Oakley Class lifeboats, a self righting system that saved many more men than the victims of accidents with water ballasted sailboats ! ( me included, if apex1s wish is heard by his highest authority ).

 

Fanie, water is everywhere, because all things are made out of water ( Thales, 2500 years ago. Thales is the name of my son, too.)
Stumble, I am glad you have read all my posts so carefully to be able to twist them for your humorous reply. That is a style that I prefer from somebody who needs to expose a negative criticism without cursing, does no harm to anybody, and is in accordance with "typing for entertainment value", as PAR and myself like to do. Keep trying !

 

Actually I was being serious (except maybe about the towing ability).

For a moment lets put aside the physics, and everything known about boat design. Now given this unreal world what exacally are you trying to get this boat to do? Initially you wanted a motorsailor, but the design has changes radically from that, so instead of pidgeon holing it, lets put some real parameters to it.

1) Speed desired under sail and power
2) Range under power
3) Ability to handle what type of conditions (lake cruising or open ocean weather)
4) Self righting from a rollover, or just to some % of heel
5) Length
6) Draft maximum
7) Max beam






Living acomodations for X number of people

 

This was a very entertaining thread to say the least. I think what zaraz may not be aware of is what equations really control and how the equations really work and what they mean in a blue water setting.

If we look at the Gerr equations its obvious that comfort and speed are much more achievable with a narrow beam, long waterline and high specific gravity ballasting. Clipper ships were long and skinny.

It does not take much increase in beam to negate substantial weight saving in displacement mode. Instead you are pushing more towards a planing hull that will require more power to achieve the same speed and therefore cut range under power or require more sail. More beam is never the way to go for more speed unless you intend to do most of your cruising coastally on plane at high power.

Yes you could take a planing hull in blue water and it will give a slightly better ride right up to the point in sea conditions where it becomes very much worse than the narrow displacement hull and far more dangerous.

I certainly like the ultra light blue water concepts but they are not practical with wider beams and certainly not practical with sail unless they carry high density ballast down deep. There is just no way around what the math tells you.

 

The highest authority on earth is the sea. Her rules are not to bend nor to argue. Her forces neither to handle nor to escape. We are silly little creatures when this authority speaks. The only way to survive at sea is to learn avoiding the most furious seastates and to find a valid compromise in the less dangerous situations. A moveable liquid in a ship is the largest danger at sea, far superior to fire. Why for mankinds sake should one just try to make such danger advantageous? For a racer (or the small lifeboat operating some 3hrs from homeport), you may find a reason, on a true bluewater boat it makes as much sense as a open fire for cooking.

To the "wish" mentioned above: I beg your pardon for having said that! By no means I did wish in all seriousness that you should loose your life at sea! But you know it is easily said "I wish you would..." what so ever, in a moment of emotional arousal.

Have a look here to see how the best performers in their business do.
http://www.dgzrs.de/index.php?id=321
http://www.dgzrs.de/index.php?id=94
and look how they do the capsize tests on the new vessel prior to delivery:
http://www.dgzrs.de/index.php?id=400
there is a video link too.

when this is your daily business you do´nt play with systems!




Regards
Richard

 

Thank you Pierre R.,

http://www.boatdesign.net/forums/boat-design/hull-shape-hull-speed-13929.html
Leo Lazauskas ;
Ship hydrodynamics has advanced very little over the last 40 years so
amateurs shouldn't despair at not understanding the wave-making
problem…( I do not... )
…we are still a long way from even a reasonable understanding of the physics involved. CFD is, of course, an enormous advance because we can now display our almost complete ignorance in fullcolour!
When I look at the seething mess of splash, spray and white-water around a fast-moving ship, I think of the great simplifications needed to make the problem mathematically tractable. After all the required simplifications and excisions are made, are we really justified (or sensible) in using sophisticated techniques?
My dear Pierre, I promise you that I will be siting in the front row when you will be honoured by the Fields, Abel, Nobel, e.t.c. prizes after you will have solved the Navier-Stokes equation for the semi-displacement hull of sailing motorboat...and I hope you will offer me some days of free vacances aboard the heavy, slow, beautiful motorsailor you will buy with the one million dollars of the Millenium price.
Everything should be made as simple as possible, but no simpler

Are you telling me that the beamy 47 ft MLB "is cruising coastly", in "sea conditions" where "it becomes far more dangerous "? Remind me not to motorsail near the US coast, because apex1 wish may still be heard by his highest authority, and I dont want a beamy, dangerous, coastal lifeboat of the US Coast Guard to wait for sea conditions to improve before it tries to save me...
"This was a very entertaining thread to say the least", indeed !

There is a large speed window, and a vast area of ignorance, right above the pure displacement hull speed. Wide beam semi displacement hulls are very difficult to study, and the progress there is really slow, because the physics are very complicated, the mathematics are very complicated, and the computers are still not fast enough to simulate the phenomena.
As far as the laws of mathematics refer to reality, they are not certain, as far as they are certain, they do not refer to reality.
P.S. instead of solving the Navier-Stokes equation, you could solve the 1666 340 years old three body problem of Newton, (the complete equation of newtonian gravity for the Earth, Sun and Moon. It is still unsolved, I guess. If we can not solve the three body problem of such a simple equation, how on Earth, Sun and Moon do we hope to solve "the seething mess of splash, spray and white-water around a fast-moving ship''' that involves interactions of millions of water and hull body particles described by a more complex equation?

 

Well thats not true! The fact that we do´nt have computer models and algorythms to calculate the phenomena in a predictible manner does´nt mean we have a lack of knowledge in that speed range.

This:



is a semidispl. vessel and we know almost everything about it.

 

happy to see the name calling and stuff has stopped and the thread is attracting some great posts
It is a pity that someone with over 800 pts chose to wipe all Xaraxs, points, simply becuse he disagreed
Richard, that pic, looks like a painting, a very good one , but cant open or enlarge it
When I was on tugs North sea , it always felt good to have a ship below one
in the conditions depicted here, it would be rather scary, at sea in a cat, or a flimsy sailing boat