CONVERTING FROM 32 VOLTS
I really enjoy Steve D'Antonio's articles and his passion for boating, and I have a question I'm hoping he can answer. I own a 1979 Hatteras that is equipped with a 32VDC system, like most of the American-built boats back then. With the 32-volt parts, batteries, and so on becoming harder to find and very expensive, I am thinking about converting to 24/12 volts. What would be involved in this process?
San Diego, California
You're right; 32-volt systems are becoming increasingly difficult to service and maintain, and 32-volt parts that were hard to come by when a vessel was built are even harder to find now. It is a common and vexing challenge.
Conversion to a composite 24- and 12-volt system—you'll need elements of both—makes good sense from a maintenance and reliability point of view, although the conversion itself can be costly. Unfortunately, few of your 32-volt cables and wires would be reusable. They were designed for the lower amperages associated with the higher voltage, which is why Hatteras selected 32 volts to begin with. Technically, it made good sense; lower amperage meant lighter, smaller-diameter wiring could be used.
The electrical panels also will need to be replaced. (If they are the original panels, replacing this 30-year-old gear makes sense anyway.) The battery banks, chargers, alternators, starters, and other engine electrical components also will need to be replaced if you opt for a complete revamp. Any lights or bilge pumps that are designed to operate on 32 volts, along with their supply wiring, also will need to be swapped out, since they are not compatible with 24-volt power.
Alternatively, you could choose to upgrade the house system alone to 12/24 volts, leaving the engines as 32 volts. While that might save you some cash, it would complicate the vessel even further by having even more voltages (12/24/32 and 120/240).—Steve D'Antonio
SEACOCK INSTALLATIONS: DISPELLING THE MYTHS
I'm a big fan of Steve D'Antonio's "Gearhead" column and frequently learn something from it. However, I have to point out that the January/February column on through-hulls contained some very bad advice. It is a cardinal sin in boat repair to attach any part that might have to be removed later in a way that makes it impossible to do so.
Steve described replacing a through-hull and using 3M 5200 sealant as a bedding compound. This sealant has a tensile strength of something like 900 lb. per square inch—a lot, anyway. After installing a through-hull in this manner, it would be practically impossible to remove it without a chainsaw, if for some reason you had to (if it got damaged by electrolysis or needed to be replaced with a larger-diameter fitting, for instance).
In boat building and repair, when you attach something that might need to be removed later—such as a window, cleat, or hatch—you use what's called "bedding compound" between the item you're attaching and the thing you are attaching it to. Bedding compound is not a glue. It is a putty that never quite sets up. Its purpose is to fill any voids and prevent leaks. The bolt or screws do the attachment, not the goop. Dolfinite Fungicidal Bedding Compound is a longtime favorite, but regular old asphalt roof patch used on houses is a wonderful underwater bedding (although it's sloppy).
Real bedding compounds work on irregular surfaces. Steve said you have to grind down the gelcoat before laying the backing plate. If you use a real bedding compound, you don't have to do that, although it doesn't hurt to do so if there's room. You don't even have to remove old paint. Bedding compounds are sold in marine chandleries in the paint section and are labeled "bedding compound." As I said, Dolfinite is one of my favorites, and you'll never go wrong using it.
"Mastics" such as 3M 5200 have their place, but, frankly, there are few places in boat construction they should be used, because they grip so well you can't break the bond they set up. Once in place, they might be as good as a seam compound in a laid teak deck, but here, the oil in the teak might prevent the material from sticking. I've had that happen in hull planking, and it was a mess. The hull-to-deck joint on a glass hull seems another good place to use it, because the extra bonding power can't hurt. Just don't use it as a bedding compound!
I realize what I'm saying is contrary to common knowledge, but I promise you that if you ask any old-time, experienced boat repair or building guy, he'll tell you just what I've said here.
George Buehler Yacht Design
Thank you, George, for your thoughtful comments. Input from well-respected industry professionals is always appreciated. Indeed, you are correct: strictly speaking, 3M 5200 is not a bedding compound; it's an adhesive/sealant. I also agree that there are few places where I would recommend its use, and I would never use it on ports, cleats, or deck hardware. Having said that, because 5200 is an outstanding sealant with tenacious adhesive properties, I can think of few better places for its use than a below-the-waterline through-hull fitting.
I also agree that it's disadvantageous to install marine gear in a manner that makes it difficult to remove for service at a later time, provided the alternative doesn't compromise the overall installation. However, if there's one piece of hardware where I'm not terribly concerned about how easy it is to remove, it's a below-the-waterline through-hull fitting. My preference, in fact, is to ensure that these fittings are virtually permanent.
The saving grace of 3M 5200 and other polyurethane sealants as used in this application is that, with a judicious application of mild heat (no more than 200°F), they release quite easily. I've removed countless seacocks, through-hulls, and struts by using this method. In rare cases where through-hulls and seacocks cannot be separated, the external portion of the through-hull fitting can be ground away (usually a 10-minute affair) and the seacock simply pushed into the boat.
As far as using 5200 for teak deck seams, this practice is to be strongly discouraged, as 5200 possesses no resistance to UV light or spilled fuel. And, while I've used Dolfinite, I'm afraid I don't share your affection for this product when used as a through-hull sealant (or roofing tar, for that matter). Modern bedding compounds that are much more user friendly and long-lived have been available to boatbuilding professionals and do-it-yourselfers for many years.
I suspect you may have misunderstood my comments regarding gelcoat removal. My instructions regarding the removal of gelcoat before installing a seacock mentioned the use of epoxy, rather than adhesive/sealant or bedding compound. Removal of the gelcoat and preparation of the surface are necessary to ensure a tenacious bond between the backing block and the fiberglass. The adhesion between gelcoat and the underlying fiberglass substrate is notoriously weak, and it's not unusual for structural components that are laminated (incorrectly) over gelcoat to cause the gelcoat to release from the fiberglass beneath. I've seen countless bulkheads and shelves come to grief for precisely this reason. Thus, it's standard fiberglass boatbuilding procedure to always avoid applying resin or epoxy over gelcoat.
As far as applying a bedding compound, sealant, or adhesive over bottom paint, it stands to reason that this, too, should be avoided, because antifouling paints are slippery and are designed to prevent adhesion of barnacles and other marine growth. This makes it naturally more difficult for any adhesive/sealant or bedding compound to develop a reliable, watertight seal. Why tempt fate when a few minutes with a scraper and sheet of sandpaper can yield a clean, paint-free surface—one that complies with most bedding compound manufacturers' guidelines, by the way—to which the through-hull can be bedded?—Steve D'Antonio
ENGINE MOUNT QUESTION
My engine mounts look very similar to the one pictured in Steve D'Antonio's ad on page 43 of the November/December '09 issue. But, upon closer examination, I discovered that my mounts have no threads for the lower nut, so the nut must be for tightening the engine mount. But that begs the question, is the upper nut enough? Have you seen this type of setup before? I'll take a closer look next time I'm at my boat; hopefully I'll find a lock washer.
Indeed, the mount you have is a common variety and is of high quality; it incorporates an oil shield that prevents the flexible rubber mount material from being damaged by leaked oil or fuel. The lower nut appears to be correctly positioned. However, I'm unable to determine from the photo if the upper two nuts (on either side of the engine bracket) utilize a lock washer or other thread-locking device. Ideally, lock washers (such as Nord-Locks) should be used to prevent loosening. Motor mount fasteners are notorious for loosening because of the cyclical loading and vibration to which they are exposed. If your setup lacks a thread-locking device, I would, at the very least, install one under the upper nuts, which are most accessible.—Steve D'Antonio