Ask Sail: the Best of August

Every month, SAIL gives its readers the opportunity to interact directly with sailing experts regarding sails, maintenance, electronics, systems and more. Check out our questions and answers from the August issue and feel free to send in some questions of your own.
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By using sail area and expected wind speeds, you can easily estimate headsail loads

By using sail area and expected wind speeds, you can easily estimate headsail loads

Larry Schnell, Cooperstown, NY

Q: I would like to add an inner forestay to my Hughes Columbia 40. The sail for this is 350 square feet. What safe working load would I need for an exit block for the mast as well as jib tracks and leads?

Win Fowler Replies

A: The load on a sail is proportional to the sail area times windspeed squared. The formula is: (sail area [in ft2] x windspeed2 [in knots]) coefficient = load. In our shop we use a coefficient of 0.00431. For a 350ft2 sail in 30 knots this yields a load of 1,358lb. In 40 knots of wind, the load climbs to 2,414lb. We assume that this is the load on both the sheet and the halyard. I would think a safe working load of 2,500lb would be pretty good.

Fowler-head

Chris Bosworth, Newport News, VA

Q: My sailboat is equipped with a Yanmar diesel. Often while motoring, the tachometer suddenly pegs out beyond the highest value. At these times there is no change in the engine itself; it is not racing. The only solution seems to be to kill the engine and turn the key off. (Simply killing the engine does nothing for the tachometer until the ignition key is turned off.) Might this be an intermittent bad connection? If so, should I look at the engine or behind the instrument panel?

Nigel Calder Replies

A: Yanmar has two types of tachometer: one of them (the GM series, which I suspect is what you have) employs a sensor screwed into the flywheel housing; the other (which is found on most other models) takes information from the alternator. The alternator type senses the frequency of the three-phase output of the alternator before it is rectified to DC current to charge your batteries, and when it fails it will likely default to zero, which is why I think you have the other type. The flywheel type could potentially go to full rpm if shorted. (Full disclosure: I am not entirely certain of this.) According to Yanmar, the most likely problem with this kind of tachometer is the connection plug on the wiring harness, though this doesn’t seem to fit your having to turn off the ignition to reset things. Still, I recommend you check this plug, as it is easy to do. If this doesn’t fix things, find the sensor on the flywheel, unscrew it, clean it and check all the connections and wiring, including those at the gauge end. The following website has some useful information on tachometers and more: yanmarhelp.com/s_tach.htm.

Calder-head300x325

Marc Meacham, Queensbury, NY

Q: I am replacing the rubrails on my 26-year-old Pearson. I have removed the many bolts that hold the rub rail to the deck and the deck to the hull. They do not appear to be corroded. Can I reuse them, or is it better to buy new bolts?

Don Casey Replies

A: My own boat turned 45 this year, and the caprail/hull-deck joint is still fastened with the original bolts. However, some time ago I replaced all of the nuts and washers because they had begun bleeding rust. The bolts have recently started to do so as well, and they are now on the list for replacement this year. This sounds like I am saying your fasteners could be good for another couple of decades, but the bolts Pearson used were almost certainly type 304 stainless steel. Type 316 stainless steel bolts are now readily available, and they are substantially more rust resistant. Given the relatively low cost of new bolts, I strongly encourage you to replace all those you have removed with type 316 bolts, nuts and washers. Hardware replacement is a bit like reefing. When you wonder if you should, the safe answer is always, yes.

Casey-head

R. Miller, Anacortes, WA

Q: Can a forward-looking sonar effectively spot floating deadheads ahead in the water when cruising in the Pacific Northwest?

Gordon West Replies

A: Forward-looking sonars for recreational boats are purposefully tilted down to minimize false returns from the surface of the water ahead. This makes them ideal for spotting submerged rocks ahead when you are entering a cozy little harbor up north. If a forward-sounding sonar was angled high enough to look ahead at the sea surface, you would constantly see “targets” dead ahead that are nothing more than wave action or reflective dead-calm sea surface. Therefore, your best bet against hitting a deadhead floating on the surface remains a maintain a sharp lookout.

West-head_0

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