Hydraulics Stink…Or Do They?
Regarding your article on hydraulic drives for sailboats (May 15, 1998), in my capacity as a marine surveyor I have extensively handled three hydraulic propulsion installations.
One of the vessels came close to causing my first marine disaster when the hydraulic line to the windlass failed during our fight to keep off a lee shore at Key West during the Storm of the Century. The failure of the windlass hose not only left us without the windlass, but without drive power, and the spilled oil created a slick in the boat.
The three Cherokee catamarans with which I am intimately familiar had a single Thornycroft Model 90, 38-hp. engine driving standard hydraulic motors. Circa 1970, this was an expedient way to put twin drives in a catamaran because of weight and expense. In later years, diesel engines became lighter and less costly. In modern times, the sail drive has become almost universal, and actually does a better job of answering every criteria stated in favor of the hydraulic system in your article.
The problems I found were: 1. Hydraulic motors are not of marine materials, thus are a constant source of rust. 2. Hydraulic motors are very heavy. 3. The hoses and diverter valves, designed for industrial machinery, are heavy, clumsy and difficult to install. 4. The hydraulic system is noisy! 5. Hydraulic oil, high-pressure hoses, and seals in both master and slave motors all need continual renewing. 6. I have not seen an installation that wasn’t wet, meaning bleeding hydraulic fluid from joints and seals. 7. There is about a 20% power train loss. 8. You still have to deal with shaft logs, stuffing boxes, struts, cutless bearings, etc.
Based upon my usage and familiarity with these systems, my opinion is that they are overly complex, heavy, expensive, power inefficient, dirty and inappropriate for installation on a sailboat.
Key Largo, Florida
The author of the article failed to mention that the aft position (of the engine) opens up the possibility of using a dry exhaust system and therefore, for metal boats anyway, internal keel cooling, allowing the elimination of at least one large through-hull. Another possible advantage of hydraulics on catamarans is having a single engine drive two props.
I have two problems with the article. Firstly, athwartship mounting of engines. Many engines will have lubricating problems if run when tilted more than a few degrees longitudinally. Secondly, the suggestion that horizontal propeller shafts eliminate transverse thrust when maneuvering. This is incorrect; transverse thrust is evident even in large commercial vessels where the propeller shaft is totally horizontal.
While building a 40' cruising sailboat in 1973-1978, I was looking at all options. I installed a hydraulic system. Absolutely powerful and reliable. Every five years I change the fluid, which takes less than one hour. One repair since 1978. In 1998 I replaced a leaking shaft seal. One motor and two drives would be perfect in a catamaran. Keep doing what you do so well—keeping us informed.
For several years I owned a 1976 Winga 31, built in Sweden. The boat is powered by a hydraulic system made by Volvo, consisting of a 25-hp. MD2B diesel, which drives a Volvo hydraulic pump, which in turn drives a Volvo hydraulic motor, which drives the propeller shaft. The engine sits under the cockpit sole, accessible by lifting a large hatch and/or removing the companionway steps. The hydraulic pump is bolted to the end of the engine. The hydraulic motor is mounted underneath the first floorboard in the cabin.
Indeed, my propeller shaft is horizontal, which is the most effective angle for the two-blade prop. The system is highly reliable, almost maintenance-free and gives excellent performance. Under power I easily get 6 to 6.5 knots with the engine running at 2,000 rpm.
It is also 22 years old and has had only one problem—the hydraulic pump—which was fixed by a mechanic.
The concept of hydraulic power for boats is apparently nothing new.
Colonial Beach, Virginia
My first experience with hydraulic propulsion was a friend’s Bruce Roberts 22, with a one-cylinder diesel mounted on springs that shimmied like Jello on a plate—at no harm and indeed with much less transmitted vibration. It was a sensible, convenient engine and shaft placement with enough power for Force 7 Galveston Bay chops.
My second experience is with our own Presto-type 35 gaff-rigged centerboard sharpie catboat, Phil Bolger’s Palo de Agua. When the original builder, Brad Story in Essex, Massachusetts, modified her six years ago, contrary to your advice, we moved the engine out of the cockpit and into the saloon. We gained shop-like access to five of its sides. We easily retrieve even tiny dropped items from a wide fitted pan. Translocating weight from the stern lowered the center of gravity (CG) . The ride improved, especially in short, choppy seas, as well as her ability to carry sail on and off the wind.
We didn’t use elegantly light hydraulics described in your article. Instead, we used Gloucester fishboat hydraulics, cousins of farm tractor units, commonly available, easily serviced, cheap, massive old reliables that any farm implement mechanic will recognize. You won’t need a gearbox or a gear reversal, so chuck them. You will need a custom-machined adapter to mount the hydraulic motor to your engine shaft.
Would I use such a system again? The convenience made a remodeling possible. But it is a hydraulic system, with multiple points at which unpleasant surprices can arise.
Just as with everything else on your boat, you need to think out the compromises.
Robert Rosan, MD
Buffalo, New York
Just read through the new PS. I agree with your comments on aft engine rooms, but I have had some negative experiences over the last 20 years with hydraulics. On our projects the systems have come out heavier, more expensive, less efficient, and much noisier than the folks that sell the systems wanted us to believe would be the case. Multiple-use systems are the worst as they get you into the issue of balancing loads, which is difficult to achieve. Finally, hydraulic oil is messy to clean up and stinks—these systems always leak somewhere. When we design or build a vessel we do everything in our power to avoid hydraulics!
How about eliminating the hydraulic pump and go all electric like the diesel/electric locomotives? You don’t need a lot of power and you can use a large generator on the engine to power an electric motor (or even two) on the drive shaft. The engine could be placed anywhere belowdecks. You could have electric winches, kitchen, windlass, etc. You could under-power the generator and use the batteries with the generator to get into and out of an anchorage with short bursts of speed. With the addition of a wind generator and/or solar panels you could power for short distances even if the engine was out of commission. Also, a portable generator with a plug-in connection could be a good emergency back-up.
Somerset, New Jersey
This bilge cleaner called Ultra-Solv sounds wonderful. Unfortunately, I have contacted numerous janitorial supply companies in the Baltimore, Washington, Northern Virginia area and nobody has ever heard of it. If you have any more information, I hope you will print it.
Richard C. Rhame, MD
According to Bill Seifert, who first recommended Ultra-Solv to us, “The product is made by Savin Products Co., Inc., 214 High St., Randolph, MA 02368. Phone 781-961-2743, fax 781-986-6204. Savin only sells to janitorial supply houses, primarily in the Northeast. I buy Ultra-Solv from the T.J. Russell Co., 500 Wood St., Bristol, RI 02809. Phone 401-253-2882. Fax 401-253-2975. A case of 4 gallons is about $30. T.J. Russell accepts credit cards and will ship case quantities anywhere in the US.
“Wear rubber gloves and use a Scotchbrite pad to loosen the years of accumulated gunk. Ultra-Solv has a PH of 13.7, and the EPA considers anything above 12.5 to be corrosive.”
Bill added that it won’t hurt keel bolts if left in the bilge for several hours, but he wouldn’t leave it for days. He also gave us a copy of the Material Safety Data Sheet (MSDS), which lists the hazardous components as potassium hydroxide (caustic potash) gas, nonylphenoxypolyethoxyethanol (nonionic surfacant), and 2-butoxyethanol gas. It is a severe eye irritant and may cause burns. Prolonged exposure may irritate the skin. Inhalation may cause dizziness, nausea and breathing difficulties. Ingestion may cause distress and nausea. There is no evidence of chronic hazards known. It is completely water soluble.
We sprayed Ultra-Solv on Viva’s bilges last spring, and it did an excellent job.
The letter about Prop Protector in your April 15 issue intrigues me. The writer says he was disappointed after reading about the Prop Protector fitted to Viva. I would have thought that your comment that “no news is good news” was a positive statement.
He need not worry about professional fishermen in this regard. We advertise in the National Fisherman every month and are selling lots of units to professional fishermen, including lobstermen. Their view is that they would rather lose a pot or two than their “wheel.”
Concerning propeller cages, some fishermen don’t like them because if a pot or buoy is sucked into such a cage it can bend or break loose and damage the propeller and/or bend the shaft.
Also, in your May 15, 1996 review, it was pointed out that such a device is “essentially a 3" diameter circular razor blade—divers beware!”
Although no human cuts have been reported by the hundreds of Prop Protector owners, we will provide each buyer with two decals that say, “Caution: This vessel is prop protected with a rope & weed cutter.”
Pointe Claire, Quebec, Canada
I would like to suggest a better alternative, a deflector which consists of two blunt-edged scimitar-shaped stainless steel blades welded to the prop strut. On a three-week cruise in lobster pot-infested Maine two summers ago, my prop was not fouled once, even though I ran over the traps with abandon. This method saves lobsters which may have entered traps and the cost of the lobster traps for the hard-working lobstermen.
Daniel Choy, MD
New York, New York
I was very disappointed to see the article on rigid bottom inflatables (April 1, 1998). I think you do your readership a disservice by ignoring an alternative that could prove very useful to many. While I admit that Dinghy Dogs will not turn a typical hard dinghy into a powerhouse of a sport boat, it does make it as stable as the RIB without the expense.
Harvey N. Waxman
1010 Pleasant St.
Worcester, Massachusetts 01602