November 16, 2010

Ready to charter? (3)

HERE’S PART 3 of the 10-question charter quiz for your amusement and delight. Are you ready to charter yet?

Fuel tank range

Question 5. You’re cruising in your trawler-type power cruiser. Your proven-accurate fuel gauge says your 40-gallon diesel tank is two-thirds full.

You know your 36 hp engine uses 2 gallons an hour at your present cruising speed of 10 knots. In the absence of headwinds, currents, and waves, is it reasonable to assume that you:

(a) Could power non-stop to a port 125 miles away?

(b) Would need to carry 13.3 gallons of extra fuel in containers to make that same port?

(c) Should reduce speed to 5 knots to halve fuel consumption and double your cruising range?

The painter again

Question 6. Despite your very clear and calm orders, your dumb crew has allowed the dinghy painter to become entangled in the propeller as you power astern to set the anchor. What is the first thing you should try to do to untangle it?

(a) Shift gear to forward and give the motor a quick burst.

(b) Shift gear to forward and turn the motor slowly by hand with a crank or with a very short jab at the starter motor after activating the compression release.

(c) Shift into neutral and pull like hell on the end of the painter?


5(a). Two-thirds of 40 gallons is 26.6 gallons. So, consuming 2 gallons an hour, you can steam for 13.3 hours at 10 knots. That’s 133 miles. In theory, you’d make it. In practice, you’d want to top up the tank before leaving, or carry 10 gallons of extra fuel in jugs, just to be safe. And just in case you didn’t know, halving your cruising speed will add to your range, but it certainly won’t double it.

6(b) If you’re safely at anchor, this is the recommended method. Yes, it’s tempting to try a reasonably hard tug on the painter but it’s usually in vain and could actually tighten up the snarled line. Speeding the prop in forward gear is almost guaranteed to make matters worse. Even if it does clear, the painter will probably tangle up again immediately. Your last resort, of course, is to dive with a very sharp knife. The dumb crew, I mean, not you.

Today’s Thought
Our knowledge is a little island in a great ocean of non-knowledge.
— Isaac Bashevis Singer

Boaters’ Rules of Thumb, #121
Lateral plane as a percentage of sail area. Lateral plane area is what stops a sailboat slipping sideways in a beam wind. Sail area is what tries to make it slip sideways. As a general rule, the relationship between the two can be expressed thus:
— The total lateral plane (including the rudder) of full-keeled boats should be between 12 and 16 percent of the sail area.
— The area of a fin keel (only) should be about 7 to 10 percent of the sail area.
— The lateral plane area of a centerboard (only) may be as little as 5 percent of sail area.

“What are those marks on your nose?”
“They’re from my glasses.”
“Well for Pete’s sake why don’t you tilt your head back more?”

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