Fuel Efficiency

[pdecat]

Scott: You are talking planing boats. Once you go on plane then weight and bottom shape are the most important issues. Light weight and flat bottom use the least power to stay on plane at a particular speed. Unfortunately light weight and flat bottom are the opposite of what you would want for sea keeping and drivability.
Long skinny displacement boats will give better economy but to get to 13knots off plane you need about 90’

I the real world though you can halva a boat which runs well both fast and slow to give good speed when you want that or long range when that is appropriate. The difference can easily be 400% better at slow speed.

 

[Ghost]

Wow. I knew I had a lot of caffeine yesterday morning with the diet mtn Dew bombs, but sheesh. Sorry folks!

7 knots seems boring until you try it in a larger boat. When I sold my twin diesel 28 sportfish that cruised over 20knots in most conditions I really worried about the "trawler" speed.

Scott consider the 48 Tolly. It will easily cruise 12 knots, top speed of 17 knots and gets good mileage. It's a semi displacement hull. Not a really deep keel, but unlike most semi displacement hulls it has round chines. The 48 Tolly is very well known for its seakeeping abilities. She's rides very nice, very gentle and very predictable. It's not a boat you get pushed around in much. It's all about waterline length and hull speed. If you get below the hull speed you get good mileage. At 12-14 knots your going to be 1.5-1 mpg. At less than 10 knots you are 2mpg-6mpg efficient.

Go bigger.

Did anybody catch the chevy volt story on the news this morning? They are claiming 3 digit miles per gallon. Anybody want to bet a case of beer that figure includes the "free" energy coming across the power cord and is in fact a bogus estimate? Nothing more than marketing again. There's another case of beer that says that on whole the media will eat up those figures as fact and most of the public won't call them on it.

 

[David M]

quote:

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Originally posted by Ghost

Wow. I knew I had a lot of caffeine yesterday morning with the diet mtn Dew bombs, but sheesh. Sorry folks!

7 knots seems boring until you try it in a larger boat. When I sold my twin diesel 28 sportfish that cruised over 20knots in most conditions I really worried about the "trawler" speed.

Scott consider the 48 Tolly. It will easily cruise 12 knots, top speed of 17 knots and gets good mileage. It's a semi displacement hull. Not a really deep keel, but unlike most semi displacement hulls it has round chines. The 48 Tolly is very well known for its seakeeping abilities. She's rides very nice, very gentle and very predictable. It's not a boat you get pushed around in much. It's all about waterline length and hull speed. If you get below the hull speed you get good mileage. At 12-14 knots your going to be 1.5-1 mpg. At less than 10 knots you are 2mpg-6mpg efficient.

Go bigger.

Did anybody catch the chevy volt story on the news this morning? They are claiming 3 digit miles per gallon. Anybody want to bet a case of beer that figure includes the "free" energy coming across the power cord and is in fact a bogus estimate? Nothing more than marketing again. There's another case of beer that says that on whole the media will eat up those figures as fact and most of the public won't call them on it.

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I thought the Volt was pure electric. Guess I was mistaken.

You want reasonable mileage, Kurt is spot on. Get a cat. The only draw back is the length to width ratio is so large some have limited slip availability. There is a 40+ sailing cat in Chesapeake. He needs two slips to handle her.

That add$ up quickly.

 

[MEfirst]

pdecat, I realize semi-displacement is still planing. The Mainship 34's have a fine entry, flat stern, soft chines (I believe), small keel, and get around 2mpg at 12-14 knots. I like some of the down east style boats and the True North looks cool, but they are pricey.

My question is why aren't more boats built like this? Seems like it might be a good market niche. Fuel prices are a bit down off their peaks, but they won't stay down forever. Is there something in this design that makes it terrible if one wanted to do the great loop or head off to the Bahamas?

 

[mixman]

quote:

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Originally posted by KiDa

You want reasonable mileage, Kurt is spot on. Get a cat. The only draw back is the length to width ratio is so large some have limited slip availability. There is a 40+ sailing cat in Chesapeake. He needs two slips to handle her.

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Actually, while quite true of sail cats, not so true any more with power cats, especially newer models. The builders are very aware of this concern and thus I rarely ever see a power cat wider than 16'. Many are 14'. Mine is only 10'. The DS3 above is 17' beam.

This cat is only an 8'6" beam:

 

[pdecat]

Ghost: in the typical 25 mile trip that most folks make daily any all electric vehicle would get infinite miles per gallon ignoring A/C, lighting and heating. as said above the economy of hybrids hasn’t increased over the last decades anywhere as much as the increase in marketing baloney.

 

[stmbtwle]

I agree GM is "massaging" the numbers but real-life "mileage" would depend on how you drive the thing. Sorta like those "results not typical" weight-loss ads.

http://www.usnews.com/blogs/flowcha...-chevy-volt-will-transform-mpg-standards.html

And how are they going to measure the Focus EV; which won't even HAVE a gas engine?

 

[surprise]

Actually the old Mainship 34's have a hard chine, there is even a bit of reverse chine. The hull is much like a hard chine lobster boat, fine entry and a keel with the engine well forward, so that the shaft angle is nearly flat. The later versions with 200HP engines are supposed to be able to cruise at 14 knots at maybe 1.5-1.6 nmpg.