What makes a "Blue Water Boat"?

[alex folen]

...Thanks Eric Spon for the informative info....learning something new every day!

To any, what makes a "blue water boat"? In the past 7 months I've been looking for such a boat and many times have Googled the ultimate "Blue Water Sail Boat". The results are coming up with a West Sail (32), Pacific Sea Craft and several others, in which these boats were said to be "OVER BUILT" in hull thickness. This seems to be the major reason. This leads me to believe the thicker the boat (fiberglass thickness in this case) is the safer one, or more of a "Blue Water Boat"? Anyway, can I just thicken the hull of my Coronado 30 to an inch thick or more thus making a stronger and more "Blue Water Boat"? I should have the resources to add additional thickness to the hull if I want. I'm just curious to know if this has been done and also if new fiberglass has problems sticking to existing fiberglass? Thanks again so much.
:o

[Frosty]

Blue water boat does not exist. It is a name made up by shiny magazines for a boat someone wants to sell you.

[alex folen]

Yeah, thanks Frosty. True True...

[Guest62110524]

to me she is a boat that will take you in speedy safety, to anywhere you want to go
She has creature comforts, is a delight to sail, has no bad habits and will sail singlehanded
She is metal, probably aluminium because she will take knocks from ice, reefs, deadheads She wll have a refrigde sytem big enough to hold a big tuna, and one that runs only 2 hrs in 24 in the tropics
she will have shade from sun and shelter from driving rain, thats it,
simple

[FAST FRED]

Besides the interior comforts the hull can be picked up and dropped 15 ft on to the water , land in any position and suffer no damage , internal or external.

That's why so few boats really are Blue Water , and cost so much.

FF

[PortTacker]

It's a great pity. So many today are designed for the boat shows. Floating RVs. Wonderful at the dock. Good thing that's where most of them stay.
Huge open plan 'living rooms' with full length galleys across from the dining area are pretty. Huge panaramic windows are wonderful. Bathrooms with jacuzzis are impressive. Big walk around beds exude luxury. They sell boats.

Try preparing a meal in confused seas, you'll see why a proper galley is small enough to wedge yourself into.
Try using the head (the usual forward location) when beating into 10 foot 8 second waves- it's like being locked in a steamer trunk and being dropped off the roof - every 8 seconds. The ony time I've ever been injured offshore is trying to use the head! Needs to be small enough to wedge into, with ample hand holds.
Try making your way through that open cavernous interior when pounding along heeled at 20+ degrees. Smaller spaces with good handholds everywhere aren't Mode O'day, but they work.
Same for sleeping on that king size bed at sea.
At least with picture windows you might see the wave coming that bashes them in...

Boats that serve you well offshore are rarely all that hospitable for entertaining at the dock....

[amolitor]

Look for a copy of '20 Small Sailboats to Take You Anywhere' by John Vigor. It explicitly includes boats that are NOT really "blue water cruisers" but by showing you what is and is not "blue water" about each boat, you'll learn a lot.

[marshmat]

To any, what makes a "blue water boat"?
My $0.02 CDN (value of opinion depends on exchange rate?):

She has to be seaworthy. And by that I mean a comfortable motion, no unpredictable behaviours, and the ability to handle a decent storm without tossing the crew around like rocks in a clothes dryer.

She has to be strong. I'd expect her to be able to survive a collision with a whale or a 40' iso container, without breaching the hull or damaging any critical appendages. I concur with Fred's criterion that she must handle being tossed fifteen feet in any direction. And I'd like to see a rig that can, while fighting a storm, survive the failure of a shroud or stay without sending the whole works over the side.

I'd expect an easily handled rig with well-built sails, or if she's a power craft, a solid and reliable engine with serious fuel filtration. I'd expect to see things set up so that one normal sized woman, not a 300-pound gorilla, can comfortably mangage all the main controls.

And I'd expect her to be comfortable, but not so luxurious that you feel guilty about spilling something. Roomy enough that everyone has their own psychological space, but not so voluminous that you get tossed around while trying to cook or clean. And with plenty of easily accessible storage.

So if something seems to meet these criteria, then I might think of it as a possible "blue-water boat" by the time it's all fitted out.

If it meets all of this at a price that a normal person has a chance of actually being able to afford, then it starts to sound like a real blue-water boat.

Needless to say, I have not seen very many such boats....

[diwebb]

Hi,
have a look at the Bristol Channel Cutter, Alajuela 38, and the Cape George Cutters. All of these are, in my opinion, "Blue Water Boats". They meet the criteria expressed in previous comments without the obvious prejudices of only one material being suitable, and are available in the marketplace at prices that should not be too outrageous. The Westsail 32 and 40 also fall in the categorie of offshore cruising boats, and there are several other production designs that do not immediately come to mind. Steel boats offer advantages for cruising but also have the disadvantage of rusting, mostly from the inside. There are two steel cruising boats here in Whangarei at the moment having large sections of the hull replaced because of rust
In answer to your question about thickening an existing hull, dont even think about it. The hull thickness was specified to fit that particular design, and should not be arbtrarily thickend. The above mentioned boats were designed with strong hulls specifically for offshore cruising so have taken in to account all of the factors involved. Arbtrarily thickening a hull will cause imbalances in the design in performance, strength of rig, freeboard, ballast etc, etc, so why do it? If you want a long distance cruising boat look at what is available and choose the one that you like and meets your needs.
All the best.
David

[apex1]

My $0.02 CDN (value of opinion depends on exchange rate?):
Never, otherwise I´ll allways have a advantage 0,02€ .:p
She has to be seaworthy.
And to stand the 15ft test!
if she's a power craft, a solid and reliable engine with serious fuel filtration.
Almost allways a pity, how the greedy ****** deliver their filter installations
And I'd expect her to be comfortable, but not so luxurious that you feel guilty about spilling something. Roomy enough that everyone has their own psychological space, but not so voluminous that you get tossed around while trying to cook or clean. And with plenty of easily accessible storage.
A bit spilling can make life more relaxed.
So if something seems to meet these criteria, then I might think of it as a possible "blue-water boat" by the time it's all fitted out.
Needless to say, I have not seen very many such boats....

What about this?: Attachment
A very early and very basic sketch of a proposal for MY next boat.
At 90´ Loa. shurely not affordable for everyone.
She sleeps six at weekend trips and max 4 at passages, thats it.
Regards
Richard

[Frosty]

38foot is not blue water for the simple fact that you cant carry enough water, fuel, dinghy, outboard, liferaft and all the other stuff that is a must and still be able to walk on deck. It will not be enjoyable lets put it that way, another 10 feet makes all the difference.

[TeddyDiver]

38foot is not blue water for the simple fact that you cant carry enough water, fuel, dinghy, outboard, liferaft and all the other stuff that is a must and still be able to walk on deck.

I knew you didn't like canoes doing blue water but how much water and fuel is enough?
An avarage 38' is maybe the thruth as you say considering tankage with modern racer/cruisers and cats and they aren't even close to blue water in seaworthines and strength.. Daysailers and PierQueenies :rolleyes:

[TeddyDiver]

Bristol Channel Cutter, Alajuela 38, and the Cape George Cutters. All of these are, in my opinion, "Blue Water Boats".

But these are.. :)

[Frosty]

Are we not defining the words 'Blue water boat'? Thats a boat capable of going to sea and traveling which can takes months. This takes as much fuel and water as is needed, and then some.

A super car is not a Mazda even though it can go the same places.

[TeddyDiver]

Thats much better way to put it.. Just wanted to state that some 33' have more tankage than some 50'. Granted thou that it's a lot easier to take that dinghy on 50'.. Deck space? Maybe better to consider only the functionability of the cockpit. How long way it's to run to foredeck is a bit more controversial..

[timothy22]

Without leaving my desk I can see books by Hal Roth, Eric Hiscock, Lin and Larry Pardey, Robin Lee Graham, Blondie Hasler, John Guzzwell, John Letcher and, of course, Joshua Slocum, all of whom cruised blue water extensively in a variety of boats less than, sometimes much less than 40 feet in length. And books by Arthur Beiser and Steve Dashew, who routinely cruised in much larger boats. William Robinson owned his own shipyard and cruised in a 32 footer and a 70 footer. Gotta say they seemed to be more comfortable in the bigger boats, although when Eric and Susan Hiscock sold the 30 foot Wanderer 3 and bought the 49 foot Wanderer 4 they considered it too big, too expensive to maintain, and the extra room barely worth the trouble. Perhaps the second best way to find out what makes a succesful blue water boat is to read the books of those who have made blue water cruising a large part of their lives.

[FAST FRED]

"And I'd like to see a rig that can, while fighting a storm, survive the failure of a shroud or stay without sending the whole works over the side"

The best chance of a wire failure and keeping the mast is with a cutter , with running backstays , even if there only set up in a blow.

FF

[Frosty]

You know criusing the equater will mean many places not having too much wind. My last sail boat a 63 foot steel sloop with 3 tons of fuel and 1.5 Tons water, 135HP mistubishi was good at sea but would hardly ever fill the sails. With mostly myself and my girl friend it was big, yet big boats handle easier.

The best I had was the Cellestial 48,Ketch that was a nice boat, but yes both expensive in marinas but then we werent talking about that.

3 days motoring and the 48 was running out of fuel.


If cost comes into it then we are not talking blue water boats but what is the cheapest. Both a good question but must be seperated.


Living here in the Malacca straits, the door way to the round the world it is rare these days that you see a circumnavigator in less than 45 ft.

If you do it is common for them to have an eye out for something bigger to continue with.

They admit to making a mistake in choosing the size as people from Uk often seem to do, encouraged by the shiny magazines and boat shows that shamelessly call anything with an engine in it a Blue water cruiser.

Blue water cruising is supposed to be enjoyable, calm anchorages or effortless night time sailing and not cluttered decks without water to shower or a cockpit that you cant stretch out in while on watch.

I suppose a 240V generator would be throwing flowers down,--- it IS a necessity.

[PortTacker]

38foot is not blue water for the simple fact that you cant carry enough water, fuel, dinghy, outboard, liferaft and all the other stuff that is a must and still be able to walk on deck. It will not be enjoyable

Utter nonsense.
Tell that to Hal Roth. Their boat was a 35 foot sloop, and they sailed the entire Pacific rim, including Cape Horn and the Aleutions. I don't remember any refueling/reprovision ships meeting them...

or Robin Lee Graham (although I think most of us would agree that sailing round the world in a 24' boat isn't a great idea...)
or even John Guzzwell....

[Eric Sponberg]

38foot is not blue water for the simple fact that you cant carry enough water, fuel, dinghy, outboard, liferaft and all the other stuff that is a must and still be able to walk on deck. It will not be enjoyable lets put it that way, another 10 feet makes all the difference.

I disagree. My wife and I sailed a Bianca 27 from England to California, 11,000+ miles, and it was a very good boat. We had plenty of food an water (no osmosis machine on board) for crossing the Atlantic Ocean. We saw other boats on our trip that were smaller and very seaworthy, a Contessa 26, for example, which Tania Abei sailed around the world. The Bianca 27 is very similar to the Great Dane 28 and the Cape Dory 30, both good sea boats. The smallest boat that has sailed around the world is 12.5' long, if memory serves, a design and skipper from Australia, I believe. Length is not a defining factor when establishing what is or is not a blue water boat.

Eric

[safewalrus]

I don't really think the size has anything to do with it/ its what the boat can withstand in the way of poor weather and come up in one piece that really matters............there again Frosties earlier comment holds a lot of water (which is more than a 'blue water boat' should); its a sales gimmick!

[Guest62110524]

ok here you are, built by an old friend to a design by master Robert Clark of UK
NZ east to tahiti, Cape Horn, to UK to the Artic
on 32 feet, room of 36( plum transom)
deep finn, sailed on vane the whole way, extremly stiff
walrus has it right in many respects, total watertight integrity and strength and the ability to sail off a lee shore

[Frosty]

I knew this argunent would raise its head , it always does.

Some people have rowed the Atlantic,--this is a test of man, not the boat.

If you intend to sail off for years you will dream of having another 10 feet.

Its true that a lot of women got off after a few months and fly home disgusted. I heard of a few bargains in Guam where the wifes have left and the guy is now stuck trying to sell a boat.

Ive met people that WILL NOT go on bigger boats --it just upsets them too much.

You can do it yes, but--- well its not my idea of sailing.

10 feet more is a hundred times better.

[Guest62110524]

ja, it is generally ackowleged by experts that 45 feet fits wave patterns the best of all

But I saw a 110 superyacht, crossed Tasman same time as us, the things hatches leaked, they were wet , pissed off,
in this lil 32 footer they were dry, safe snug,

[johnelliott24]

Rarely do I read about what is best for laying ahull and rolling. I have been in 2 North Atlantic storms and have witnessed what the sea can do. So I want a boat that can take large rolling waves when I am hurt or sick and lots of things are going wrong. Any suggestions on boats that can take a beating and still sail well on the normal days?

[TeddyDiver]

Long keeled heavy gaffer..

[timothy22]

I think it may be useful to make a distinction between the ideal boat for cruising in the cruising grounds of one's choice, be it the Seychelles, the Bahamas, the Pacific northwest, the Med, the Baltic, Polynesia, etc. and the ideal boat for passagemaking, or getting there from wherever you are. There are very different requirements for each. Passagemaking puts a premium on the kind of boat that by design can keep course and take care of itself with little or no help from the crew, with large reserves of safety and stores to deal with the unforeseen. These tend to favor the boat with greater carrying capacity, easier motion, bulletproof, (or floating container-proof) hulls, and inattention-proof rigs. Folks with greater skills and a higher tolerance for privation can do with much less boat. Slocum's Spray and Tillikum were, even by the standards of the day, totally unsuited for the passages he made.
I have no direct experience with weather that required us to lie a-hull (we were racing, after all), but Timmy Hansen's Foolscap (ex-Figaro III) was fine in the roughest Annapolis-Newport ever. It was a classic S&S interpretation of the old CCA rule- yawl, modest draft, some forefoot, centerboard, and fat. When hove to for reefing, she just slid away from the worst of the seas. Later I read that more forefoot than is currently fashionable helps a boat hold her head up, and the shallow draft keeps her from tripping over her keel. Worked for us.

[timothy22]

Kenichi Horie sailed across the Pacific Ocean in 1999 aboard a 32.8-foot (10.0 m) long, 17.4-foot (5.3 m) wide, catamaran constructed from 528 beer kegs. The rigging consisted of two side-by-side masts with junk rig sails made from recycled plastic bottles.

I would have loved to have been at the party where they emptied the 528 beer kegs!

[apex1]

I would have loved to have been at the party where they emptied the 528 beer kegs!
That was a crew party exclusively.... I´m shure.:rolleyes: He otherwise might not have done the trip.

[Fanie]

You guys are all too serious. Especially Frosty and Timothy :D

A 'blue water boat' is a boat on blue water. If the water is green, it is a 'green water boat'.

I was under the impression that if you sail there you have a blue water boat.

If you are comparing the ability of a boat to live out there, well, then there is no such thing. Even the tankers drown if the weather goes bad enough as does everything else except maybe some of the fish.

We've now heard of 'blue water canoe's' and 'blue water beer kegs' only because they were there...

One thing I agree with Frosty, some boats called 'blue water' boats are just blue water enough to get you in the sh... I mean deep water.

[Somerville]

Having sailed two traditional long-keeled boats, one 45' and one 55', across an ocean with the usual mix of good and bad weather, my personal experience says it is the crew that makes a "blue water boat".

As long as the boat is well built, and the crew is knowledgeable, then many boats that traditionalists call unsuitable may be used for offshore sailing. My personal preference in size would be about 37-40 ft LOA, a modern deep fin and spade rudder underbody with a cutter rig.

Over the years, I've had two lower shrouds break, both of them were rod and one headstay clevis pin sheer - that was no fun, but we didn't lose the rig in any case. Inner forestay and double spreader with separate shrouds, not the modern setup of discontinuous seems to be the best for offshore - in my opinion.

Sufficient water is probably the most important requirement, in at least two, if not more, tanks - and the crew knowing how to ration water usage.

[Tcubed]

John, (post #25) your question invokes the all important matter of damping.

Without damping all boats would capsize eventually given randomly generated surface oscillations.

Generally, damping is augmented by large lateral planes and 'flats' in the sections.

When lying ahull there is almost no remaining aerodynamic damping (unless the wind is strong enough to effect damping on remaining windage) so hull damping is crucial to heavy weather survivability.

Most modern double wedge canoe forms with small high aspect appendages afford scant damping which is an issue of concern for all weather passagemaking.

It is therefore fairly obvious that the forms that were in favour at the height of sailing (pre motorisation) were full keel designs with large damping factors to be able to carry on with business as usual regardless of weather. The full keel has been shown to be one of the superior forms for consistency of performance across a broad spectrum of conditions.

If on the other hand ( as in racing , or racing scene inspired yachts) the operating conditions are anticipated to be within a certain window, then of course a fin keel can result in performance benefits.

[johnelliott24]

Good points. Talking once with one sailor that survived 2 big hurricanes he said that sooner or later the final resting position for a boat is ahull -- meaning that when drogue bridles break, or you are too exhausted or hurt, etc... you will end up ahull; therefore how the boat behaves ahull is important if you think you might end up in extreme conditions. Your dampening thoughts make sense. Thanks

[mydauphin]

Blue water boat is a matter of dreams, pocket book, preparation, living with less, enjoying the moment and not being in a hurry. Personally, I don't know if I would cross at mid ocean in anything smaller than 80 feet. Island hopping however is a different thing.

[Somerville]

Tcubed wrote:
"Without damping all boats would capsize eventually given randomly generated surface oscillations.

Generally, damping is augmented by large lateral planes and 'flats' in the sections. "

I think you are missing the importance of mast inertia in damping roll of sailboats in a seaway. Marchaj's investigations showed how the same hull with a rig was far more stable than without.

Add this to the wind resistance at high wind speeds of the rig (mast and shrouds) and modern sailing craft with less keel surface area may not be as unstable as you think.

I've only tried lying ahull one time, winds 50 to 65kts, for about 12 hrs, when the wind dropped below 45kts, the boat started to bounce around uncomfortably so we got back to sailing. This happened on passage from Azores to Bermuda, so we had plenty of searoom and I had enough crew that one could sit in the companionway to keep watch.

[Tcubed]

Let me gently correct your very good point .<<<<I think you are missing the importance of mast inertia in damping roll of sailboats in a seaway.>>>>

The increase in rotational moment of inertia about the roll axis (rmoiara) due to the mast is not the same thing as damping.

The windage of the mast is a powerful damper in strong winds. In no wind it is a negligible damper as it does not have enough area, but of course you would then hoist the sails which do damp very strongly in no wind, provided they are sheeted in, of course.


The 'rmoiara' will slow the roll period, in fact it slows it twice, because it also raises the boats CoG, lessening the righting moment. (based on the laws of simple harmonics)

This is very apparent when unstepping a mast and a passing motorboats' wake makes the now mast-less boat roll. It is immediately obvious the boat rolls much faster.

This correlates exactly with your experience that it damped the motion effectively with the strong wind but stopped being so effective once the wind eased off somewhat.

***

Now to this i would add two points;

The first is pedantic but valid nonetheless in certain situations, namely when in a strong left over sea but no wind. (These can be very terrifying as the sails seem like they will tear the rig out of the boat but to take them down makes the motion even more dangerous)

The second is something i do think is quite important and that is the boat with less rig windage would still be able to carry some sail and make way. What i mean is lessening rig windage is crucial to increasing the wind strength ceiling of positive VMG to windward, an often under appreciated feature of seaworthiness i feel.

So therefore, yes, spar windage will significantly damp a boat forced to lie ahull due to wind strength + other factors , but it is much better to have the damping come from elsewhere as per my above two points. Imagine you could still keep up a little trysail in that same wind?

[Somerville]

Your point about mast inertia slowing the roll period as not being the same as damping -

"The increase in rotational moment of inertia about the roll axis (rmoiara) due to the mast is not the same thing as damping. "

appears to be a matter of definition. I think that in your initial post you were talking about form stability as a means of 'damping' a vessel's roll period. Being pedantic, I think that damping is used as a general term describing a reduction in vessel motion by any of several means.

I'm not a big fan of traditional hull forms, and my personal experience has not shown increased damping owing to those hull forms. In fact, just the opposite is what I've seen. The roll period may be extended but the angle of heel to either side has been much greater which I think may be attributed to the more V-eed hull form of the traditional craft.

More later

[Frosty]

Blue water boat is a matter of dreams, pocket book, preparation, living with less, enjoying the moment and not being in a hurry. Personally, I don't know if I would cross at mid ocean in anything smaller than 80 feet. Island hopping however is a different thing.


Phew!! that god for that I was thinking I was the only one.

[Tcubed]

Somerville,

It is indeed important to define terms if one wishes to communicate ideas clearly.

I was and am using the same definitions as used C.A. Marchaj in his textbooks.

That is damping is how effectively roll energy gets dissipated (just talking about roll for now).

Roll moment of inertia / righting moment defines roll period. (this is an integral)

Form stability is not damping.

Maximum roll amplitude and roll damping are two separate things.

Myself i am a boat design atheist. Science and real experience are my guides. The working boats of the 19 th century proved themselves to be extremely able in all kinds of conditions and who knows where the evolution of boat design would be at today where the motor to not have made working sail almost extinct. We nowadays live in an age where all recent sailboat evolutions have been made with racing (note i say racing, not speed) and recreation in mind. This has made it difficult to remain objective and not influenced by current design fashions. Within the minute fraction of sailboats which can be considered serious blue water cruisers one observes a vastly larger proportion of 'traditional' forms however, which is hardly a coincidence. Keep in mind too that few of even the most adventurous cruisers consistently sail in as poor conditions as working sail, since they could rarely afford the luxury of staying at anchor. You do have Marchaj's book?

I cannot speak for your own personal experiences whatsoever, but there are certainly well accepted norms to augment hydrodynamic roll damping, such as large lateral planes, sectional flats, hard chines and other. This is one of the reasons freighters etc have slab sides and flat bottom. Observe the midsection of the great tea clippers and it's the same.

[Frosty]

Hey I know more than you do . I read a book N stuff, you must listen to me because I am done everything on bots.

The question is --What makes a blue water boat?

Not rolling or floating or mast inertia.

In simple terms --what size Tv do I need? how mush water to wash my T shirt?

Where is the authur? what do you mean by "blue water"?

[TeddyDiver]

what do you mean by "blue water"?

What other waters there is so we can exclude and the rest is blue?

White water? Kayaks and raft boats.. been there done that etc..for 25years
Sweet water? The main raw material for Grey water & black water? Hopefully only inside tanks.. but unfortunately also been there done that up to my neck bcs 've been a plumber :D
Ice water? Hey! I'm living 70deg N so got even a t-shirt..
Muddy Waters?

More? :P

[Frosty]

You see some people dont read the question. they think the question is what makes a seaworthy boat. Or what makes comfortable boat. Both those questions and the answers are important in a Blue water boat but not only.

Some read the question as how small a boat can I got to sea in, Or what conditions could you tolerate for extended periods of time.

What is a Blue water boat is personal, and to me comfort is of paramount importance and comes along with size, fuel, water, bathrooms etc etc

Cruising will involve you being in harbour 99% of the time.

[TeddyDiver]

What is a Blue water boat is personal, and to me comfort is of paramount importance and comes along with size, fuel, water, bathrooms etc etc
Cruising will involve you being in harbour 99% of the time.
Seriously speaking there's no excact length as you suggest to have those qualities if we just don't restrict our choices to mass production boats (which, in my books anyway, aren't true bluewater boats). However there are trade offs both in short and long hulls. One of the worst comes with long hulls trying to find an appropriate and affordable mooring for that 60' hull. It just restrict's the options to a fraction what can be gained with 30'er.. and as you say that's 99% of the time..

[mydauphin]

I tell people that usually buying a new boat for cruising is a waste of money. You usually have to start by removing a lot of stuff and getting bigger versions of everything. And invent new storage places for more things. I think I have like 5 anchors, 3 huge hurricane rope, 2 huge dock lines, multiple chains, almost 2 spares for every running part. Super duty windlass, multiple electrical systems, at least 4 vhf radios, like 10 bilge pumps, 6 fuel/water filter separators, emergency suits, 2 outboards, 2 dingies, 3 vhf antennas
A computer and log book to keep track of everything. Multiple charts, tech manuals on every piece of gear. And I personally know every wire, hose and clamp on board..... Boy, I am just tired of talking about it.

And this is just to be ready for Murphy to happen somewhere unexpected. So you need a boat big enough to carry all this stuff across the ocean and the fuel to get there with a reserve.

Oh, food, water , freezer, stores, stove, heating....

And we need low center of gravity, stability and everything needs to take jump 5 feet in air.

[alex folen]

Yes Frosty, the question is what ultimately makes a blue water boat, explicitly? In my original question I was curious to know if a more solid vessel ultimately makes a Blue Water Boat? Is it ultimately the strength of the vessel? Is it a bobbing vessel that can withstand tumbling in the seas and being dropped 15 feet or 50 and stay intact? Worse case seniors at sea, physically? ?If I construct a huge indestructible 20-inch thick carbon fiber airtight barrel with tons of water and food, is this blue water?. Forgive the ignorance but I would think a sinking vessel is pretty dramatic and probably lethal far at sea without help. One should and can plan how to conserve water and food reasonably. Not knowing if the boat will crack up is a little bit more out of your control I would think. (I saw a program on the Discovery channel of rouge waves being real). I?m all for science and I cannot even begin to express the value of which I have stumbled across here hence absorbing as much form the apparent and extremely experienced. Anyway, most beer is 90% water.

[Fanie]

Anyway, most beer is 90% water.
Frosty is 98% water.

So who has the most substance. Frosty or the beer ?

[Frosty]

What you just described was a seaworthy vessel, but can it carry enough water to live with?

A life boat is a seaworthy vessel but believe me the accomodation was last on the list when they built it, so its not a blue water boat.

Beer is 95% water if it has 5% alcahol--hic

[alex folen]

Funny fanie, I as substituting beer four water in the rations. However, blowing smoke is a different equation.

[Eric Sponberg]

It is worthwhile to note two good books:

"Seaworthiness, The Forgotten Factor" by C.A. Marchaj. It discusses capsizing primarily, and what constitutes good design for resistance to capsize.

The other is "Desirable and Undesirable Characteristics of Offshore Yachts" by the Technical Committee of the Cruising Club of America and edited by renowned offshore sailor John Rousmaniere. This was published in 1987, and while it has lots of good advice, I think it is a little dated towards the boats of the CCA rule era. Nevertheless, it has some good points about boat design, equipment, and handling.

Also, any of the books by Steve Dashew are recommended. He has shown that a well equipped (and by that I mean air conditioning, refrigeration, and all the niceties of life) in a narrow hull is very fast, seaworthy and comfortable. Whereas the two other books listed above speak about weathering storms when going slow, Dashew advocates that you should be able to go fast to stay out of and ahead of bad weather.

And that really is the crux of the matter--all boats can handle good weather, but only some boats (those that are better built, equipped, and crewed by experienced and prepared crew) can handle bad weather well.

Eric

[apex1]

Also, any of the books by Steve Dashew are recommended. He has shown that a well equipped (and by that I mean air conditioning, refrigeration, and all the niceties of life) in a narrow hull is very fast, seaworthy and comfortable. Whereas the two other books listed above speak about weathering storms when going slow, Dashew advocates that you should be able to go fast to stay out of and ahead of bad weather.
A very, very remarkable guideline, as many others the Dashews provided.Below you find the link
And that really is the crux of the matter--all boats can handle good weather, but only some boats (those that are better built, equipped, and crewed by experienced and prepared crew) can handle bad weather well.
Eric

I blow the same horn Eric, just like to point out two things.
1. The sailing boat (with cloth) usually cannot escape bad weather, whereas the motorboat can. What leads to Dashews philosophy again.
2. I widely agree with Dashews point of view and came to almost the same conclusions, but... it can be done for half the price to the same level of seaworthiness and comfort. The FPB is by far too playful, too fondly in sophisticated and exotic gimmicks.
and the link:
http://www.setsail.com/dashew/dashew228.html

my 0,02€
Regards
Richard

[Brent Swain]

My twin keels do a great job of damping. Even under bare poles in a left over chop, the boat rolls far less and the motion is far gentler than any single keeler I've sailed on.
Blue water is offshore water, a far deeper blue than many coastal dwellers can ever imagine. . It turns from green to intense blue about 100 miles off the Oregon coast. The blue comes inshore on the northern BC coast in winter, then moves a offshore in june ,as the water warms and algy blooms begin.
Brent

[apex1]

Blue water is offshore water, a far deeper blue than many coastal dwellers can ever imagine. . It turns from green to intense blue about 100 miles off the Oregon coast. The blue comes inshore on the northern BC coast in winter, then moves a offshore in june ,as the water warms and algy blooms begin.
Brent

Brent, we are just saying "blue water", we mean turqoise.................!
And, never build a twin keel boat (except for tidal waters).

Regards
Richard

[GTO]

apex1..

In another thread you used the nutshell analogy in regards to small boat strength. This was in response to my mention of the 10 foot yankee girl and 14 foot tinkerbelle.

I'm curious as to what point a boat ceases to be a "nutshell" and becomes a proper boat that is likely to not survive storm conditions in the Atlantic or Pacific due to being "too small"?

Is it the construction method that makes a boat (10' - 50' size range) a "nutshell", or just the overall length?

Or am I missing other considerations?

[TeddyDiver]

I'm curious as to what point a boat ceases to be a "nutshell" and becomes a proper boat that is likely to not survive storm conditions in the Atlantic or Pacific due to being "too small"?
:D :D So proper boats bust in storms :rolleyes:
Seriously it's a point of engineering not any length or building method thing..
Speaking of a bit larger boats (like some Colin Archers) considered as nutshells are in many ways "overengineered".. Rescue boats.. subs..

[FAST FRED]

A Blue Water Boat is able to handle equippment losses with ease.

Engine dies , so the auto pilot is dead , self steering gear does the watch.

Trickier is when the Self Steering dies and the helm is given over to a lashing , and the boats actual ability to hold course with minimum assistance.

This leaves mostly the older full keel boats as the only realistic option, as the modern "cruiser" seems to need constant attention.

"I'm curious as to what point a boat ceases to be a "nutshell" and becomes a proper boat that is likely to not survive storm conditions in the Atlantic or Pacific due to being "too small"?"

AS the boat construction/scantlings is never to scale , a smaller boat should survive much more than the weaker larger boats.

Think of a soda bottle , small and hard to break, tho it may have a wild ride.

FF

[GTO]

What prompted my question are the often made assertions that boats are "too small" for safe ocean sailing. However, Tinkerbelle made it across the Atlantic, and Yankee Girl sailed across the Atlantic and from the west coast of the U.S. to Hawaii.

I appreciate how strength does not scale upward well compared to the forces that act upon a boat/ship, and I can see how something like a supertanker can be subjected to incredible twisting and bending forces due to its size. But considering the normal sailboat size ranges of 20' to 50', are those forces that great with regards to the strength of the materials used in building these boats?

So I guess what I'm looking for is the typical reason why proper boats (or boats that allow at least sitting headroom, comfortable sleeping arrangements, and plenty of provisions) of a smaller size (say 20' - 30') can not or are not built to the "nutshell" standard. Or are smaller boats actually safer than most posters would have one believe? Still not sure I'm asking the right question but I'm trying. :)

And by the term "proper boat", I'm using Yankee Girl and Tinkerbelle as examples of what I do not consider "proper boats", as they were physically cramped and uncomfortable. Yankee Girl in particular was often wet, causing Gerry to develop a bad skin rash/infection. I feel a boat should provide for the physical comfort and well-being of the crew to be considered a good or "proper" boat.

[apex1]

apex1..
Is it the construction method that makes a boat (10' - 50' size range) a "nutshell", or just the overall length?

Or am I missing other considerations?
No, I do´nt think you´re missing anything, because in the latter post you are on track:
I appreciate how strength does not scale upward well compared to the forces that act upon a boat/ship, and I can see how something like a supertanker can be subjected to incredible twisting and bending forces due to its size. But considering the normal sailboat size ranges of 20' to 50', are those forces that great with regards to the strength of the materials used in building these boats?


And, yes the forces are tremendous, and the boats usually designed to be as light as possible (senseful), for performance reason. That is alright, if we have a look who actually is the average buyer / sailor. Read 999 of 1000 boats are not designed to survive in heaviest wheather.
Surprisingly (or not so, if you understand the reason), the very experienced Dashews (I mentioned several times), went for a light ship at the lower end of the scantling rules, which will not survive a breaking rogue wave (IMHO). But it has the advantage to escape the weather due to its (lightweight related) performance. So, again we have not the "one rule gives the answer" solution.
If you scale up the "Tinker Belle" to say 80ft keeping the scantlings "rigidity to lenght" ratio, you end up with a hull / deck about twice the weight of the customary and contemporary designs. If we translate weight to strength (wich is not really exact but makes it easy) than we have about 8 times the strength of the average boat! In real life it´s closer to 6 times. But it is "the nutshell".
Example: Aluminium plating of 5mm to 10mm = 5x5x5 = 125 or 10x10x10 = 1000.
Now we have moved our boat from say 50 tonnes to 75 tonnes completed dry weight. That means we need much more power, larger tanks, etc. We pay a penalty every single hour we are sailing / motoring for just "in case". But exactly this way I go with my next passagemaking motorboat.

Regards
Richard

[mydauphin]

I can travel from Miami to Brazil in 26' sailboat. I can cross the Atlantic, travel around Africa, cross to India island hopping and cross the Pacific... But would I want to do it. A 50' catamaran would be nicer, but would it be safer. NO. A 70' Monohull would be a safer if properly equip.

See they have the range because of wind power. Put a wind generator get a watermaker.

Personally, I like efficient trawler designs. Your fuel limits your range. But now a days with little money, water, navigation and weather forecasting are easy.
So it is question of what you and your crew can endure and the preparation of the boat.

[apex1]

Personally, I like efficient trawler designs. Your fuel limits your range. But now a days with little money, water, navigation and weather forecasting are easy.
So it is question of what you and your crew can endure and the preparation of the boat.

Right, apart from the Trawler, its a contradiction between efficient and trawler. It´s either, or. Moreover, a trawler is not a heavy weather boat! The fishermen would like to have narrower boats if they had a choice. If you go through serious weather, a trawler is slamming awfully and sometimes making no headway! Too beefy on the nose. Trawlers are not very famous for their ability to go fast downwinds (following sea). A long, narrow hull with a fine entrance, fine exit, minimized superstructure, is by far the better, faster and more economical choice. And can be the cheaper to build too.
Just to show another approach for a motorboat. If you look at the picture below, you´ll see the very first sketch of what I´m going to build for me. It´s not a motorsailer, the rig is a "coming home rig" only. The design is derived from a Buehler Troller, but round bilge, larger wider etc, etc. Do´nt value the appearence, I like the old workboats. They do´nt attract burglers, pirates and the like,to much.

Regards
Richard

[mydauphin]

As always, you are mostly right. I said, "I like efficient trawler designs". Not that trawlers are efficient but within the design limitations the most efficient for these. A narrow boat is best, but sometimes uncomfortable. A efficient design is something that works for you not just fuel. Everything is a compromised. After many boats , I have a 72 foot monohull Aluminum, 15 foot beam, 3 foot draft, with twin engines. Some people would say it is too big, others too small. Some would like it wider, others narrower, others single vs dual engines. There is no perfect boat.

Whatever works but if I ever cross the ocean it will be on a transport

[apex1]

As always you are mostly right. I said, "I like efficient trawler designs". Not that trawlers are efficient but within the design limitations the most efficient. A narrow boat is best, but sometimes uncomfortable. A efficient design is something that works for you. Everything is a compromised. After many boats , I have a 72 foot monohull Aluminum, 15 foot beam, 3 foot draft, with twin engines. Some people would say it is too big, others too small. Some would like it wider, others narrower, others single vs dual engines. There is no perfect boat.

Thank you. And I agree.
I edited my post, have a look.
My boat will be either alu or wood Epoxy, the decision is pending.
The dimensions are not too far from yours: 88´by 17,6´ single engine.

Regards
Richard

[Brent Swain]

All waters are tidal to some extent. I'm sure glad I went for twin keels , 25 years ago. I have crossed the Pacific many times in my twin keeler and wouldn't want anything with fewer keels.
A friend did a circumnavigation in one of my twin keelers and said the same . His next boat also has twin keels.
Decades ago, most of my boats were being built with single keels . Now most are being built with twin keels, and those who went for single keels almost all wish they had twin keels.
The greatest critics of twin keelers are usually people who have never cruised anywhere in one.
Brent

[mydauphin]

I am not sure how to post pics. If someone could tell me. I would post mine

Apex, on your design, looks like good boat for long distances. I would call it a trawler. Runs at hull speed, good size keel. What are does massive water intake in middle of hull, jet drives, portholes? Sails can be used at anchor to add stabilty.

[apex1]

I am not sure how to post pics. If someone could tell me. I would post mine

Apex, on your design, looks like good boat for long distances. I would call it a trawler. Runs at hull speed, good size keel. What are does massive water intake in middle of hull, jet drives, portholes? Sails can be used at anchor to add stabilty.

Go to your post, click edit, go down, click go advanced, go down click manage attachments, upload

Its a Troller, not a Trawler! Range is somewhere around 6500 to 8000 nm. As mentioned, this was the very first, and very broad sketch. I fiddled with the idea to install two different sized gensets and "Schottel Pumpjets" as propulsion. I would have always sufficient load on the engines, the jets would reduce friction at half of the hull to almost zero (laminar flow), they could act as some stabilization too, no drag of the prop below full throttle!!!, no drag of operating rudder (rudder is blocked if not sailing), maneuvrable like soap in a bathtub, no extra genny etc. etc.......
But a CPP is much less expensive, and all the stuff turned out a bit complex. I still develop the idea further and maybe build it once, but for my personal boat I have choosen a CPP arrangement.
I´ll attach a pdf to show you the interior layout at present stage.
My provider here in Turkey is so terrible slow on uploading it may take one hr. to get the 155kb up here, so come back please.

Regard
Richard

[apex1]

The greatest critics of twin keelers are usually people who have never cruised anywhere in one.
Brent

HaHa... have seen where I´m from? mud flats, tideland all the northsea coast.
My boats are single keel.

Regards
Richard

[mydauphin]

I would stick with props not jets for anything below 25knots. A properly sized single prop to a single diesel is hard to beat. My boat has one speed, and a forward and reverse. Yes I can adjust speed but not by much. 8-12 knots. I don't need Adjustable props... Rudders are not much drag at this speed either. Remember you need a rudder even if you lose power with emergency sail.


Have a smaller diesel that can run a hydraulic drive on main shaft, bow and stern thruster and windlass. Mentioning thruster because a 80 foot boat without thruster can be a handful to dock unless you have crew of 2 or 3. The thruster will help in this.

Your hull reminds me of a battleship hull. The BS is a little longer in the middle. The section in middle can be longer without inducing much drag. Of course water surface is bigger. How much horsepower and prop size your thinking .

[apex1]

I would stick with props not jets for anything below 25knots. A properly sized single prop to a single diesel is hard to beat. My boat has one speed, and a forward and reverse. Yes I can adjust speed but not by much. 8-12 knots. I don't need Adjustable props... Rudders are not much drag at this speed either. Remember you need a rudder even if you lose power with emergency sail.
Have a smaller diesel that can run a hydraulic drive on main shaft, bow and stern thruster and windlass. Mentioning thruster because a 80 foot boat without thruster can be a handful to dock unless you have crew of 2 or 3. The thruster will help in this.
Your hull reminds me of a battleship hull. The BS is a little longer in the middle. The section in middle can be longer without inducing much drag. Of course water surface is bigger. How much horsepower and prop size your thinking .
Dont mix "Schottel Pump jets" and ordinary jets, tey have nothing in common.
A properly designed Prop does´nt exist! It is designed to be optimal at one speed only! A CPP is always far better (in a displacement hull), because you can load your engine sufficient at low revvs.
You would be surprised how much drag a rudder makes (in service) if one would tell you with some real figures. And naturally the boat has a rudder (for sailing), look at the picture. Do´nt need a thruster, I managed 35 meter boat, steam engine, single prop, no engine control or gearbox, in heavy weather, with one deckhand. Articulated rudder is worth the effort, thrusters are not. It´s a passagemaker, not a weekender, docking is´nt the issue. About 15 to 12 years ago I was living on my boat, did´nt have a foot on the hard for 14 month.
The drawing does´nt show a real hull, so looks a bit ja, like battleship.
The prop size will be somewhere around 1,30 M, the engine 500hp. Too much, ja, I know. She would have 900 if she was´nt derated drastically. But I like it that way, and I know exactly what I am talking about.
In calm weather I´ll need say 150hp to achieve hullspeed (just a example), going uphill in a heavy seastate can easily need 350 to 400 if you like to make headway. Running away from serious weather some extra horses are always welcome for say 24 hrs at 1,4 lwl. Problem is, I underload my engine every day I enjoy a good weather trip, or I dont have the power to do what I want. The CPP is the solution.
Now how is your boat looking?
Regards
Richard

[mydauphin]

Familar with Schottel Pump, still think propeller, rudder, shaft more efficent at getting power to move boat. Properly sized single prop will work well with proper setup and can't be beat for price. CPP is good, but costs are prohibitive for me. Docking is not a issue until you have to do it and since I really dont want to take too many people along bow thrusters are great. I am trying to see if articulated rudder works into my system. I am keeping rudders small for effiency may add stern thruster to compensate. Twin engines help alot.
I understand reserve Hp for getting out of trouble the problem you know is loss fuel economy or underloading engine. I have 2 250 hp engines, will be working one day on propane injection for emergency power of 400 hp each.

I saw a setup that was perfect sometime ago. One transmission, one shaft, two engines with a clutch. You could pick a 200hp, a 300 hp or both.
Very old mechnical clutch system but what a concept.

On my boat, I need to get more updated pics, will send in a couple of days.

[apex1]

Familar with Schottel Pump, still think propeller, rudder, shaft more efficent at getting power to move boat. Absolutely! You can´t beat the efficiency of prop / shaft. But if we count every penny, the Pump jet design came very close in efficiency (at about twice the initial cost).
Properly sized single prop will work well with proper setup and can't be beat for price. CPP is good, but costs are prohibitive for me. The CPP is´nt that much above a good gearbox. It pays back within one year in a fishboat! All Skandinavian fishermen are using CPP only!
Docking is not a issue until you have to do it and since I really dont want to take too many people along bow thrusters are great. I was talking about my average use and my experience only. I managed a old Harbour Patrol boat of 22 mtr. for several years, single handed (single prop CPP, no thruster), and there are several thousand of commercial vessels doing it daily.
I am trying to see if articulated rudder works into my system. Try it, you´ll never again miss it. I am keeping rudders small for effiency may add stern thruster to compensate. Twin engines help alot. Naturally, it´s my personal preference to go with a beefy single instead.
I understand reserve Hp for getting out of trouble the problem you know is loss fuel economy or underloading engine. No, sorry, exactly that is wrong! I am never underloading my engine having a CPP !!! That is the only reason having it. It´s simply not possible to run a high displ. high torque engine with a fixed prop, at low rev. efficiently! You destroy it.
I have 2 250 hp engines, will be working one day on propane injection for emergency power of 400 hp each.
I saw a setup that was perfect sometime ago. One transmission, one shaft, two engines with a clutch. You could pick a 200hp, a 300 hp or both.
Very old mechnical clutch system but what a concept. Much more expensive than a CPP, and a coming home rig, do you agree?

On my boat, I need to get more updated pics, will send in a couple of days.
Hello dear fellow member, I hope you do´nt mind that I reply as I did above. It´s just easier for me.
Did you have a look at the accommodation plan (the pdf attachment in one of my earlier posts) ?
Kindest regards
Richard

[Tcubed]

CPP: controllable pitch propeller, captive power plant,.. Sorry if i missed a previous definition, could you clarify please?

[apex1]

CPP: controllable pitch propeller, captive power plant,.. Sorry if i missed a previous definition, could you clarify please?

the first bet................ Triple T

Regards
Richard

[Tcubed]

Ok now i'm a bit behind.

Looking at your image it looks like a ducted jet...

[apex1]

Ok now i'm a bit behind.
Looking at your image it looks like a ducted jet...

welcome TTT, and look here:
http://www.schottel.de/deu/r_produkte/SPJ/uebersicht.htm

Regards
Richard

[Loveofsea]

In '91 i designed and built a 19ft wooden, flatbottom dory-style skiff powered by a 3 cyl outboard tiller. Since then i have logged over 65,000nm of open sea travel and have spent over 600 nights anchored at the most desolate places off the Southern California coast, solo...I've made one trip less than 60nm offshore in the last decade. This is a true blue water skiff.


For me building a boat was a means to an end~


But when i was building it, the anticipation of what was ahead turned my backyard into a tropical paradise :cool:


Brad

(loves the sea)

[Landlubber]

Brad, 65000 miles in a droy would have to be a world record, have you ever been ashore, that is 70 miles a day every day from the day of build, your fuel bill could solve the world economic crisis!

[Loveofsea]

Landlubber, I wish! (check your math--)

i don't run like i used to, but my trips average over 170nm per..

Here is a satellite pic of my stomping grounds:

http://rapidfire.sci.gsfc.nasa.gov/subsets/index.php?subset=AERONET_La_Jolla.2005238.terra.1km

See that island that sits all by itself, the farthest offshore? I've made that run 131 times and have spent 213 nights anchored around that god-forsaken place that is affectionalely referred to as Jurassic Park--more commonly known as San Nicolas Island, The Island of the Blue Dolphins...

I do underwater photography as a hobby, so for me it is all about being able to get to those offshore destinations. I searched far and wide for a real blue water boat that would fit into my garage, but to no avail..

As you boatbuilders already know, that's why we build our own~!

[Tcubed]

Apex, That jet pump drive is news to me. I do read german so maybe you can fill me in on its pros and cons?

I presume the jet nozzle collar is rotatable 360 deg so you can aim the thrust any way?

However it seems to me that with all the accelerations that the water needs to undergo through the unit it must not be so efficient. By efficient i mean energy imparted to fluid/ shaft power.

[apex1]

Apex, That jet pump drive is news to me. I do read german so maybe you can fill me in on its pros and cons?
I presume the jet nozzle collar is rotatable 360 deg so you can aim the thrust any way?
360° full power!
However it seems to me that with all the accelerations that the water needs to undergo through the unit it must not be so efficient. By efficient i mean energy imparted to fluid/ shaft power.

You are right, it is not as efficient as a shaft prop arrangement, but if one counts every single point as previously mentioned, it comes very close. Main advantages are cutting the hull friction by approx. 40%, and reducing drag by eliminating the prop and prop well, another (different to measure) is the reduction of hull induced resistance due to steering the vessel. (You must not stem the whole ship against the waterflow when changing course).
It´s just a few % here and there but sums up noteicable. As does the cost! All in all I calculated twice the price as for a single engine CPP arrangement.

Regards
Richard

[Tcubed]

OOps i meant to say do not read german.

40% hull friction reduction ? How are you arriving at that number? I am not being judgmental , just want to know. Seems to me the parasitic drag of a well designed hub+shaft is an order of magnitude less than what you say.

As for forcing laminar flow a normal prop at the stern favorably affects the pressure gradient as well...

If it has 360 deg thrust capability then why are you putting them midships? Is it so you can more or less move sideways? Control would be almost impossible though. Seems to me more advantageous to put them aft (maximize benefits to BL) for control or even since you have one either side, staggering them one about 25% LWL aft and the other at say 85%. It would be asymmetrical but that does not matter much and it would give you excellent maneuverability.

Maybe i'm just not understanding very well. Perhaps we should start a new thread for this topic as well...

[apex1]

OOps i meant to say do not read german.

40% hull friction reduction ? How are you arriving at that number? By eliminating friction from amidships abaft ! I am not being judgmental , just want to know. Seems to me the parasitic drag of a well designed hub+shaft is an order of magnitude less than what you say.
You mean Prop+shaft ?
As for forcing laminar flow a normal prop at the stern favorably affects the pressure gradient as well...
No no, you are completely misunderstanding the subject.
If it has 360 deg thrust capability then why are you putting them midships? Is it so you can more or less move sideways? No, you could as well move sidewards if you mount them elsewhere .Control would be almost impossible though. That is wrong (see "Tractor Tugs with Voith Schneider" props, the best maneuvrability you can find).
Seems to me more advantageous to put them aft (maximize benefits to BL) for control or even since you have one either side, staggering them one about 25% LWL aft and the other at say 85%. It would be asymmetrical but that does not matter much and it would give you excellent maneuverability.
Impossible.
Maybe i'm just not understanding very well. Perhaps we should start a new thread for this topic as well...

Yeah, sorry, I was´nt precise enough, i reckon. You completely missed the subject. Please go to the website again (is completely in English) and have a deeper look.
You´ll understand then, the flux LEAVING THE PUMP is in contact with the hull about 1 mtr behind the outlet, forming a laminar flow, wich naturally reduces friction to about zero.
And yes there are two of them, if not, how would it function?
I do´nt like to annoy you, but please try again to get the "Pump jet" principle in.

Regards
Richard

[mydauphin]

One thing I ran into in using a jet drive in small boat I modified was the lost of displacement, by that I mean the water in drive made my boat heavier and sit in water more than just weight on drive. Here are some weird numbers for you. On a 14' boat, the jet drive weight 35lbs, water within drive 35lb, positive displacement if drive wasn't there 35lbs. Yes, I save a rudder drag, a prop and less draft. But I made boat handle like it had another person, didn't turn as well, accelarate as well and I believe the air intake adds drag .... I think jet drives are not as great as many proponents would like like you to believe.

[apex1]

I think jet drives are not as great as many proponents would like like you to believe.

Yeah...you´re right.
But we are´nt talking about Jet´s here. We are talking about "Pump Jet", a complete different world, and about a 80 ton vessel! The few cups of water in the pump are not worth talking.

Regards
Richard

[marshmat]

mydauphin,
Most data sheets I've read on jet drive units, from most manufacturers, give both the weight of the pump itself and the weight of the entrained water.

Richard,
I had a look through the entire English side of Schottel's pump-jet pages and their application brochure. They indicate that the jet outlet flow is angled 15 degrees downward from the hull, so I'm not sure where the idea of "flux leaving the pump is in contact with the hull about 1 mtr behind the outlet" comes from. Could you clarify?

Another thing- if the flow does bend upwards and roughly follow the hull (which it very well might, if the boat is moving somewhat), and if the jet outlet velocity is 10 m/s, the Reynolds number of that flow a metre behind the jet is on the order of 10^7. So even at fairly low power, the boundary layer of the jet wash along the hull underside is most definitely fully turbulent. At higher speeds it would become more turbulent.

I can see it being a very versatile unit for workboats that are often manoeuvring at low speed, in shallow waters, or with awkward loads. And, except for its 360 kg weight, the SPJ15 looks like it could be very appealing for a sailing auxiliary (no grounding damage! no shaft/strut drag under sail!). But I'd have to see a lot more test data in order to believe that it would have an efficiency advantage.

[apex1]

Richard,
I had a look through the entire English side of Schottel's pump-jet pages and their application brochure. They indicate that the jet outlet flow is angled 15 degrees downward from the hull, so I'm not sure where the idea of "flux leaving the pump is in contact with the hull about 1 mtr behind the outlet" comes from. Could you clarify?
Tests
Another thing- if the flow does bend upwards and roughly follow the hull (which it very well might, if the boat is moving somewhat), and if the jet outlet velocity is 10 m/s, I doubt it´s that much! Schottel claimed in a datasheet to have a very low velocity!the Reynolds number of that flow a metre behind the jet is on the order of 10^7. So even at fairly low power, the boundary layer of the jet wash along the hull underside is most definitely fully turbulent. At higher speeds it would become more turbulent.
Surprisingly it is said to be not!
I can see it being a very versatile unit for workboats that are often manoeuvring at low speed, in shallow waters, or with awkward loads. And, except for its 360 kg weight, the SPJ15 looks like it could be very appealing for a sailing auxiliary (no grounding damage! no shaft/strut drag under sail!). But I'd have to see a lot more test data in order to believe that it would have an efficiency advantage.


Hello Matt,
thank you for your valuable input.
First I should straighten out something:
I guess I have not expressed clear enough in one of my former posts that I am NOT a advocat of this system. It seemed to be of some advantages if compared with a classical single engine fixed prop, thats all. I still think I´ll give it another look in the future, but gave up for now, to follow the idea a year ago, for some very simple reasons, it´s at least twice (I reckon even more) the price as a single engine CPP system, and some of the parameters are still just estimations.
The figures, facts and estimations I posted, have been collected over a period of about 12 years.The sources are, the manufacturer, the HSVA Hamburg, a protocol of a two years operation of a 85 mtr. Coaster, some studies which I made in collaboration with a shipyard in Germany.
The effect of a noticeable reduced friction (although astonishing) was discovered by HSVA. I have no reason (and shure not the knowledge) to doubt their test results.
And, yes the outlet is 15° downwards, but the flow lays laminar at the hull after about one meter, even at slow speed.
The advantages of a eliminated drag of prop and well, as of rudder function should be clear and self-explanatory. As is the maneuverability and the fact, that a genny diesel never sees any underload. Alltogether still not unattractive, but... see above. And it´s not that I refuse to reply to any further question coming up about this subject, it´s just too time consuming. And as long as I have no access to my collected data (I´m in Turkey for a while), I feel unable to provide proven data. And it would make me dubious to guess.
So instead of developing this system further on here (which for me is riding a dead horse at present) I would prefer to come back to topic.

Regards
Richard

[TeddyDiver]

And, yes the outlet is 15° downwards, but the flow lays laminar at the hull after about one meter, even at slow speed.
The advantages of a eliminated drag of prop and well, as of rudder function should be clear and self-explanatory. As is the maneuverability and the fact, that a genny diesel never sees any underload. Alltogether still not unattractive,

Maybe starting another thread when you return to Germany? It opens whole bunch of possibilities.. like having multiple much smaller units around the hull to maintain flaminar flow constantinously..

[apex1]

Maybe starting another thread when you return to Germany? It opens whole bunch of possibilities.. like having multiple much smaller units around the hull to maintain flaminar flow constantinously..

Why not, or posting in the "New propulsion systems" thread. But at present, I think, it´s easier to disgrace myself, than to provide proven info.

So, what makes a "Blue Water Boat" ?


Regards
Richard

[GTO]

Posting proudly, based upon total ignorance aside from armchair reading and analysis, I've decided a "blue water boat" is whatever "boat" makes it across some "blue water".

Boat in this case being defined as any thing someone can at least hold on to and survive crossing "blue water".

From Hugo Vihlen's 6 ft April Fool, to the 10' Yankee girl and upwards, it has occured to me that a "blue water boat" is whatever anyone wants it to be.

If you are a tough sailor, you can sail across the atlantic in a 6 foot boat, or around the world in an open 19' Drascombe lugger. I've pompously decided that it is up to the people on a boat to determine if it's "blue water" or not, or even if it "is" a boat. How do we define "is"?

Say I build a "boat" with a LOA of 4 feet, but a draft of 16' to hold all the necessary provisions, and drift with the gulf current from the USA to the UK. Is that really a boat or ... ?

So in summary, I've decided that the sailor in question must define their "boat", determine if said boat, being built, actually meets their specifications, and then determine if their specifications were correct!

I would say the Titannic was not a blue water boat, as it was designed to be unsinkable, yet it did indeed sink! Having failed its design specifications, it therefore failed to be a "blue water boat" as its owners, designers, and builders specified one to be.

On the other hand, Webb Chiles' Drascombe Lugger was a perfect "blue water boat" as it carried him, mostly, around the world in the manner he expected it to carry him, i.e., half swamped on several occasions, and at sea level for one 2 week period.

So there you go, there is the definition of a "blue water boat".
Send me your gifts of gold, wimmins, and beverages (cold), and I will declare your boat a "blue water boat". :D

[alex folen]

Probably the most definitive and correct definition of a “Blue Water boat”, ..significantly eloquent and scientifically and spiritually exact in speaking. But every and ALL other definitions of a blue water boat have equal weight and value to me. I tend to agree if you can survive the seas on a floating log then that’s a blue water boat. Thanks fellows and gals.

[alex folen]

Whoops, Thanks GTO.

[alex folen]

Alabama! GTO? Yeah, right by the sea you is.

[mydauphin]

Hey GTO, you might appreciate this. One of the biggest boating experiences I ever had was crossing the Inlet at Mobile from Gulf Shore side to Dauphin Island in a 5hp 18foot canoe with three people. We ended up in sand island, both of the guys on the canoe were praying out load, and I was about to convert. The Canoe that is normally very fast was having trouble fighting incoming tide in shipping channel. I was going sideways, my arm was falling off from resisting current in outboard and we can within feet of landing on the rocks by the fort....

Moral of the story, sometime you get lucky, sometimes you don't. Even a bay it is no place to try it... Blue water boat - a boat and crew that is prepared for anything that can and will happen.

[apex1]

Blue water boat - a boat and crew that is prepared for anything that can and will happen.

First valid statement (all of mine included)....... mydauphins statement!!!!!!!

[Fanie]

Yeah Apex, but was the idea to get to the right answer so quickly? You're only at post #92.

[Loveofsea]

Full circle

Blue water is as blue water does.

:)

But don't EVER forget:

There is nothing like the feeling of utter security on a tumultuous sea~

[apex1]

Yeah Apex, but was the idea to get to the right answer so quickly? You're only at post #92.

Fanie, you mean the thread will be closed, now that we have the answer? I excuse, did´nt bear that in mind.



.
Life must be awful, nobody tries it twice.

[mydauphin]

Hey,

thats my post - don't steal it...

Blue water boat - a boat and crew that is prepared for anything that can and will happen.

[apex1]

Did´nt steal it..just qoute, see my comment.

[mydauphin]

Hey Apex my wife won't let me have last word... So let see if you let me on this one

Blue water boat - a boat and crew that is prepared for anything that can and will happen.

[GTO]

Alabama! GTO? Yeah, right by the sea you is.

Unfortunately, its north Alabama. I call Lake Guntersville my pond.
But I am aiming for bigger waters. One day....

[M-Sasha]

Hey Apex my wife won't let me have last word... So let see if you let me on this one
.

İf Richard is on the scene, it is not easy to have the last word, he is the boss.
But impressively, you managed it.:D
Cheers Sasha

[mydauphin]

Everyone check out this post, it is bluewater related and I want your answers.http://www.boatdesign.net/forums/boat-design/blue-green-water-anchoring-windlass-chain-anchor-26508.html

thanks

[rickthorn]

Fresh "Tidy Bowl" in the head?:p

[alex folen]

just wanted to tahnk you all, ...again for the extreamly valuable input. ...sorry for the clutter but felt it worth it...Cheers!

[Brent Swain]

My ideal of a bluewater boat is one that can easily survive a collision with a cargo container at hull speed with no serious damage .
Brent

[mydauphin]

My ideal of a bluewater boat is one that can easily survive a collision with a cargo container at hull speed with no serious damage .
Brent

Wow... I don't know many boats that would survive that. Even in a steel boat the hit might make a big enough hole to cause a major problem. But I feel better with an aluminum boat vs a fiberglass.

[Landlubber]

What makes a "Blue Water Boat"?

Blue water. Give her a gut full and if she comes home she is a blue water boat.

[Brent Swain]

One of my 36 footers hit a sunken steel barge at hull speed on the very sharp corner of the barge, hitting the boat 6 inches off the centreline foreward , no dammage. You are not going to get a more concentrated hit than that.
Brent