Self-tackers, radio trouble and diesel versus gas engines
SELF-TACKERS WORTH IT?
Q: I’m seeing more and more self-tacking jibs out on the water (and in the pages of SAIL) these days. I can’t help thinking these boats are all hopelessly underpowered, especially off the wind, when compared to boats with even slightly overlapping headsails. But I could be wrong. How much extra power do you get from an overlapping headsail (as opposed to, say, a 150 percent genoa) compared to a typical self-tacker?
BRIAN HANCOCK REPLIES
When a yacht designer comes up with the sailplan for a design he/she has a certain amount of sail area that can be incorporated based on the righting moment of the boat. In the past, there was a feeling that a big headsail and a small mainsail was the way to go, in part because mainsails were a pain to deal with. However, as hardware changed and mainsails became easier to manage, designers found that it was better to concentrate the sail area there rather than the headsail. They therefore increased the sail area of the mainsail and moved the mast forward to keep the center of effort (CE) in the correct place. The net result is that you have the same sail area as before only distributed differently, so no, the boats are not underpowered. Also, except in all but the lightest of conditions, overlap is overrated. The 50 percent that wraps back around aft of the mast only causes the boat to heel once the wind comes up. Self-tacking jibs also more than pay for themselves in terms convenience.
MORE ON ‘HARD-WORKING’ DIESELS Q: I have always heard that diesels operate best under mid-to-high operating load, like being run for long periods of time and that this provides the best miles per tank, something that is especially appreciated by sailors who do serious cruising. That said, living on Long Island Sound it appears to me that very many, if not most of the sailboats I see are used for Wednesday night/Sunday afternoon one-design or PHRF racing, or basic daysailing. The regular drill for engines on these boats is to be started at their slip or mooring and run at relatively low rpms for 10 to 15 minutes before being shut off for sailing—which begs the question: if so many people with sailboats, old and new, operate them in ways that are inefficient for diesel engines, why are there no options to power a sailboat with an efficient, stateof-the-art gasoline inboard auxiliary? I would think that someone would see an opportunity to market smaller, more efficient gasoline auxiliary engines to the sailing community. Or do diesels like and excel at light work as well? — Peter Bigelow, Darien, CT
DON CASEY REPLIES
The lauded penchant of diesel engines for hard work has always struck me as more interesting than important: not unlike knowing that refrigerators are more efficient when full, or that lead-acid batteries last longer if you don’t discharge them deeply. The real always takes precedence over the ideal. Diesel engines are by design more robust because they operate at high compression levels. Even under light load this makes them longer-lasting. They are also more reliable due to the absence of electrics and tend to develop peak power at lower speeds, making them a good match for turning a prop. Beyond that, the elephant in the room remains the volatility of gasoline. A diesel leak inside the boat is an environmental issue. A gasoline leak has tragic potential for both boat and crew. Recurrent news stories of boat explosions almost invariably involve gasoline. Rarely are sailboats involved, because so few now carry gasoline in internal tanks. The prudent sailor even stores gasoline for the tender outboard on deck. With the ready availability of lightweight diesel engines, the choice today to retain gasoline power is almost always driven either by cost, complication or a desire to maintain originality. As for inboard gasoline power for all other sailors, I’m pretty confident the verdict is already in.
TO SWITCH OR NOT TO SWITCH…
Q: My 1982 7.5hp Evinrude outboard fried my new AGM battery in two years. I saw the voltage at 15.1 volts most of the time. I since have installed two diodes in series in the charging line. I also added two switches in parallel to each diode. I start the day motoring with both switches open, but as the battery charges I close one switch first, then after the battery charges more I open the second. I always stop the motor before making the switch. Do you think it would be OK to change the switches with the motor running?
NIGEL CALDER REPLIES
Problems arise when you disconnect or otherwise switch off the output cable from an alternator while it is running. There is a voltage spike that can destroy the diodes in the back of the alternator. However, in your case the alternator remains connected to the batteries at all times. So yes, I am pretty sure you will have no problems opening the switches with the motor running. That said, I would run with one of the switches open at all times. Assuming this imposes a voltage drop of around 0.6 volt, it will drop the voltage at the battery to 14.5 volts, which is about where you want to be in terms of the absorption voltage, with no risk of accidentally driving the battery higher. When the battery is fully charged, opening the second switch will drop the voltage to a little below 14.0 volts, which is about where you want to be for a float voltage. Note that to make sure these are the kinds of volt- ages the battery is seeing, you need to test the voltage across the battery posts as opposed to anywhere else in the system.
AM RADIO STRIKING OUT
Q: On weekends, I am addicted to my trusty AM radio for the ball games now that football is back. I recently installed a new marine audio system, and it works great for the media I plug in. It also works fairly well on the FM music classical stations my wife loves. However, for AM stations I have literally no reception, even though I am using my marine VHF masthead antenna up 40ft off the water. What gives?
GORDON WEST REPLIES
Sounds like you are using an entertainment radio antenna splitter to the VHF antenna. While splitters for AIS may work on a masthead VHF antenna, you cannot rely on these splitters to work at all on broadcast band AM on a marine VHF antenna. Most masthead VHF antennas have a coil “shunt fed” to mast ground, and at AM broadcast radio frequencies your signal is grounded totally out. The cheap no-name splitters are not a good match to your lifesaving VHF marine radio either. Ditch the AM/FM broadcast radio antenna splitter and go to a local auto store for a rubber replacement whip antenna and cable. Plug in the cable end to your marine stereo and enjoy both improved FM and loud-and-clear AM radio ball games. Hide the whip anywhere belowdecks for best reception.