I think that under 45 foot its almost impossible to find a "real" passagemaker under power, the reason why i went for a 36 foot Motorsailor and yep a real trawler. Most boats will survive but the crew will be near to dead on a ocean passage. The motion of such a small trawler under "only" power in ocean conditions is terrible and exausting to the crew.
Sorry for the long qoute, but i think more then read worthy. Choosing a Passagemaker
Choosing a Passagemaker
By Dolph McCranie, DolphM@aol.com
the Right Whale, Krogen 48 Whaleback, hull #8
I wanted a true passagemaker. Robert Beebe in his book "Voyaging Under Power" says that a true passagemaker is a motor boat that can make an open ocean passage sufficient to at least cross the smallest ocean, the Atlantic. The shortest route across is from Bermuda to the Azores; a distance of about 1,850 miles. A safety factor in excess of ten percent should also be included. I felt that the minimum range I would be satisfied with would be 2,250 nautical miles. And this at a speed that would allow us still more range if we traveled even more slowly.
We had owned two boats before. Our first was a 25 foot Grady White Sailfish. A trailerable hardcore fishing boat but not comfortable for extended cruising. We next moved to a Grand Banks 42. Again a wonderful boat but not one that would allow us to fulfill our dreams. It was our dream then as now; to cross the Atlantic Ocean in our own boat.
In addition, my wife Beverly and I were looking at a complete life style change. The pressures of my surgical practice and the "new " medicine had become too much. We opted for an early retirement and life as live aboards.
So we now had several criteria that the new boat had to meet: it had to be a true passagemaker, it had to be livable, it had to be affordable and above all it had to be seaworthy. Not an easy set of specifications to meet.
It was time to truly do our homework! I read everything I could get my hands on about long range motor boats. I was most helped by Robert Beebe's book, "Voyaging Under Power." This book has recently been revised by James Leishman. Mr. Leishman added to the book and had the excellent sense to leave Beebe's text essentially alone. The book is a treasure trove of information. The chapter on the arithmetic of power boats, by itself, is worth the price.
From this source and others, I learned about above water to below water ratios, displacement length ratios, hull speed ratios and prismatic coefficients. Not to mention the all important "trawler truth ratio." All of these add together to form the mathematical description of a boat. They will tell you what the designer intended the boat to do. That may or may not correspond to the advertising copy.
The D/L gives you a number to use in determining the relative heft of various boats. The larger the number the greater the interior volume and corresponding load carrying ability. The D/L ratio is equal to the displacement in long tons, (2,240 lbs), divided by the cube of the loaded waterline length divided by 100. You shouldn't have to derive the number; the manufacturer should provide it. Most passage making motor boats in the 50 foot range have a D/L near 270. The smaller the boat the larger the D/L must be to give the necessary load carrying capacity. The Nordhaven 46 with her LWL of 38.4 feet has a D/L of 383. The Krogen 48 with its LWL of 45.5 feet has a ratio of 267.
The above water to below water ratio is just that. The height of the boat above the water divided by its draft. Captain Beebe felt that a ratio of 2.6 was the maximum allowable for boats that were going to venture into waters that were historically very stormy, such as the north Atlantic.
Hull speed ratios can be determined by dividing the speed in knots by the square root of the loaded waterline length. Conversely the boat's speed at a given ratio can be determined by multiplying the hull speed ratio by the square root of the loaded waterline length.
For a boat with a LWL of 36 feet the square root is 6. Her speed at a hull speed ratio of 1.0 would be six knots. At a ratio of 1.2 it would be 1.2 * 6 or 7.2 knots. Her maximum theoretical hull speed would be 1.34 * 6 or 8.04 knots. She would be most economical between 6 and 7.2 knots (a ratio of 1.0 to 1.2). The boat could probably be driven to a hull speed ratio of 1.4 or about 8.5 knots but with a significant increase in fuel consumption.
Prismatic coefficient, when I first heard the term my eyes crossed! We don't have to worry about its derivation, just find out it's value. It is really a mathematical description of how pointed the ends of the boat are. But each prismatic coefficient has a corresponding hull speed ratio at which the hull is most efficient. In the speed regions in which most passagemakers operate, (hull speed ratios of 1.1 to 1.2), the most efficient prismatic coefficient is 0.6 or a little under. Some times compromises in prismatic coefficient are made in order to increase the D/L for more internal volume. This results in a less efficient hull requiring more power to push the boat through the water with a corresponding increase in fuel consumption.
The "trawler truth ratio" is important; it estimates how closely the boat in question resembles a true trawler. Most long distance yachts have a reasonable relation to true trawlers. They do not have, or need, the load carrying capacity of a fishing trawler. That is to say they have a smaller displacement length ratio. They do, however, have the needed internal volume to carry sufficient crew, fuel, food, and supplies for self sufficient long distance voyaging. They are full displacement hulls and usually carry ballast.
According to Beebe, the weight of the ballast should equal at least fifty percent of the weight of the fuel. This prevents the boat from becoming too light and too high in the water as the fuel is burned.
Full displacement means that your boat travels through the water not on top of it; it has to displace the water as it moves through it. Your speed through the water is limited to "hull speed" or slightly over. As we have said, hull speed is related to the waterline length of your boat. The theoretical maximum displacement hull speed is 1.34 times the square root of the loaded waterline length. When a speed equal to a hull speed ratio of two is reached the boat is planing. With enough power most semi-displacement boats can be driven over maximum displacement speed but pay a major fuel consumption penalty. True planing hulls of course are designed to exceed hull speed and proceed on top of, rather than in, the water. Most planing boats in the fifty foot or less size class have a relatively limited range, as do semi-displacement hulls, especially when forced to plane.
When making long passages, for reasons of economy and range, most boats, regardless of hull type, are run at hull speed ratios between 1.0 and 1.2. As you can see this means relatively slow speeds unless you have a very large boat. (Those freighters doing twenty knots or better are traveling at hull speed ratios of about 1.1 to 1.2 or so, their most economical speed).
In boats you can go fast or you can go far, but you can't go fast very far. (Unless you have a very large boat and budget!)
We thought a cruising speed of 8.5 knots would be adequate and give us room to slow down if needed for more range. A LWL of forty five to fifty feet would give us the desired cruising speed. Very small changes in speed can result in major reductions in fuel consumption and increases in range. (Our boat burns about 2.1 gph at 7.5 knots and 5.6 gph at 9 knots)
All boats are compromises. You just have to decide what it is you really want your boat to do and which set of compromises you can live with. No boat can do it all.
We wanted to live comfortably and travel long distances safely and economically. This required a boat with a hefty displacement/length ratio, a single engine, an efficient hull with the right prismatic coefficient as well as sufficient waterline length to give us our desired cruising speed.
Single engines, (I can hear the flack already), I feel, are more fuel efficient than twins and the shaft and prop are protected by the keel. Usually the rudder is large and is protected by a large skeg. Far safer in the North West with its floating debris, logs and ice. The large central rudder and full keel are also of great help in following seas. That having been said, I also feel that an alternative form of propulsion is necessary for safety. Ideally this should take the form of a wing engine with its' own prop and shaft.
Of the production boats available in 1994, when we placed our order, the choices that met our criteria were few. We looked at all of them but like "Goldy Locks" we only found one that was "Just Right." We ordered a Krogen Whaleback. The Whaleback has a prismatic coefficient of 0.601, a D/L of 268, an A/B ratio of 2.6, and a LWL of 45' 5".
This means that she is efficient at speeds from about 6.5 to 8.5 knots and can be driven to about 9.7 knots. With a fuel capacity of 1000 gallons her range at 7 knots (with a safety factor of about ten percent) should be in excess of 2,250 miles.
I believe the Whaleback to be the largest and most commodious 48 built. Jim Krogen, the designer, did something that few designers do, he lived on his own boats. The living spaces in the Whaleback rival that found in most 60 footers, yet it fills all of Robert Bebee's criteria of a boat that can cross the Atlantic and venture in to the North Atlantic. The above to below water ratio, displacement length ratio, prismatic coefficient and range are all there. Add to that a pilot house that is to die for, with 360 degree visibility, chart table, settee that converts to a watch berth etc. etc.
The floor plan we selected has three staterooms. The boat itself has about 700 square feet of living space. The main living area is all on one level with the pilot house accessible via a winding staircase. Beneath the main deck there are four compartments: a large lazarette, engine room, forward machinery space, and a forward compartment. The compartments are separated by very substantial bulkheads.
The engine room provides complete access to the engine and generator, albeit on hands and knees. In the machinery space there is a "sit down" work bench along with the water tanks, house batteries, fuel filters and plenty of room for stabilizers, water makers, air conditioners etc. The forward compartment houses the 100 gallon holding tank, bow thruster, batteries for the windlass and considerable storage. We kept our vegetables and beer here on the Alaska trip. It was our "root cellar."
The price of the boat includes the windlass, anchor and rode, 12 KW Northern Lights genset, Heart Interface 2500 watt inverter, compass, rudder angle indicator, Princess gas stove, microwave oven, washer dryer, and other equipment as standard.
The boat was purchased from Bob Grant, former owner of Seaward Yachts in Portland Oregon. Unfortunately Seaward was sold to Grand Yachts North West subsequent to our delivery, and Bob is no longer with the company.
The boat arrived January 11, 1996. The dealer, Bob Grant, and I went aboard before the off-loading. The boat was immaculate inside. In minutes the longshoremen had the covers off and the slings in place. We watched from the dealer's boat as ours was unloaded from the freighter and placed ever so gently in the Willamette River. After inspection, opening the raw water seacock, and filling the Cat with coolant the engine fired immediately.
Then it was off to the fuel dock and down the Columbia River to Ilwaco, Washington, for commissioning. It was in Ilwaco that the "out of the water" part of the commissioning was done. Here the epoxy barrier coat and bottom paint were applied and the heavy equipment installed. We installed a hydraulic bow thruster and stabilizers manufactured by Wesmar.
In addition, the wing engine, a fifty Hp Yanmar, was installed, along with its own shaft and feathering prop. This little engine by my calculation should be able to push the boat to at least six knots. Subsequent trials proved the calculations correct.
A Sea Recovery, 600 gallon per day, watermaker was installed and all through hulls for sensors, future air conditioning etc. were also installed at this time. We also added bypass oil filters, from Gulf Coast Filters, on both the main engine and generator.
It was then back up the river to Rogers Marine in Portland for installation of the electronics and the thousand and one other things that are needed on a cruising boat. Rogers did a wonderful, but not cheap, job of helping with equipment choices and installation. Thank you Cheryl and Dennis!
Here we installed for navigation a Garmin GPS plotter and a Northstar 941x with built in differential as co-GPS. Both are run through a selection panel to the two auto pilots. Either GPS can run either pilot.
The auto pilots are ComNav units a 1001 and a 1420 as back up. Both are completely independent and have their own pumps etc.
The radar is a 48 mile Furuno, model 1941. The fish finder is a V850 Raytheon unit. For a trip log we chose a Standard MD 50. The unit was later replaced with a similar Auto Helm device.
The VHF radios are Icom, a M 126 DSC and a M 58 for back-up. the SSB is also Icom, model 710. The combination loud hailer and auto fog horn is from Standard. The speakers also act as an on-deck intercom. Very handy when anchoring or docking.
Just when the long suffering people at Rogers thought they were done we added a diesel-fired forced-air heater by Espar to the list as well as an auto Halon fire extinguisher for the engine room. Subsequently we added smoke detectors in all of the enclosed spaces with warning lights and a buzzer in the pilot house.
Our dingy is a 10-foot Carribe RIB with a 15 Hp Yamaha outboard. We get the dink on and off using the mast and boom, (rated to lift 1000 lbs.). We cheated and mounted a small electric windlass at the base of the mast to do the real lifting. The system works very well!
We have a Givens life raft and a Litton 406 EPIRB. We also carry four rubber survival suits. That water in the north west is definitely cold!
How did all this stuff work, you ask? After a 5,000 mile maiden voyage cum shake-down cruise to Alaska and back, I feel that I can answer that question.
First the wing engine, we had occasion to need it several times. All of the problems but one requiring the wing engine involved the hydraulics. The shaft connecting the engine to the hydraulic pump was not substantial enough and broke three times. When this happens you have to shut down the main engine. The little Yanmar saved our bacon, big time! Self rescue is not only satisfying but beats the Hell out of being towed. Especially since help would have been many hours or days away. Besides you can't anchor in front of a glacier!
The stabilizers and thruster work great. I hope that we now have the bugs out of the system and will have no more trouble. The hydraulic system itself has never been a problem, only the connection to the engine. With the single engine and large rudder I find that I use the thruster less and less as time goes on.
With the Gulf Port filters we have not changed oil for 700 engine hours. We have had the oil analyzed twice by Caterpillar, and it has been normal both times. We saved at least three oil changes with their attendant mess and oil disposal problems, not to mention the expense.
The auto pilots, radios, radar, fish finder and GPS units worked without flaw. The only problem was the MD50. This may have been due to some creative wiring. The Auto Helm unit has worked well.
The main engine, Caterpillar 3208 NA, has been perfect, as has the Yanmar. The genset had an oil leak finally repaired in Canada. The leak was due to a crushed O-ring. Once that was replaced we had no further problem.
Fuel consumption proved nominal. We burned 2,300 gallons of diesel fuel in 644 engine hours and 400 genset hours. This includes a very uneconomical run from West Port Washington to Channel Islands Harbor. We ran the boat at about nine knots or better all the way down trying to beat the weather. We succeeded too, except for some 15 footers at the Oregon California border area.
The boat itself has been magnificent. We have had no significant problems at all. Docking from either side has been a breeze. The lack of side decks has not been a problem at all. More important both myself and my wife have adapted to life as live-aboards without a single fist fight. Bev says that she doesn't miss the big house or all the work that went with it. We have both lost weight, feel fit and our friends say we look younger too! (Do I hear a stampede?)
At this writing we are in Southern California, and, rather than go through the canal, as previously planned, we have decided to go back North to Canada and Alaska once more. The Inside Passage is 1,100 miles long, but there is 27,000 miles of coast line. There is so much to see and so many tiny settlements to visit that we felt bound to return.
References and recommended reading:
Voyaging Under Power, Beebe/Leishman, McGraw Hill
Cruising Under Power, Burke, Putnam
Stapleton's Power Cruising Bible, Stapleton, Hearst Marine Books
Sell Up and Sail, Cooper, Sheridan House
Sea Sense, Henderson, International Marine Publishing
Gentlemen Never Sail to Weather, Moore, Prospector Press