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Old 06-17-2013, 08:53 PM   #1
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Thoughts on this Lafitte Skiff Hull

How efficient do you think a Lafitte Skiff hull could cruise with a smaller diesel engine such as a FL120 or something comparable? What exactly would this hull be by definition? Semi displacement?

These work boats are generally powered for shrimping so tend to have powerful engines to push/pull nets and carry home the payload. This one in particular has a Cummins 5.9 6BTA 330 hp which the owner says he "cruises the boat at 1600 rpms @ 8 mph burning 4 gallons an hour on most trips. The boat will plain up and run however and will run at 16 mph atabout 2600 to 2700 rpms buring 15 gallons an hour on plane. 19 mph at 2900 rpms is the best I've seen"

I'm curious as to what you guys think a hull like this would putt putt with a smaller engine? Or would the hull design itself not allow for anymore efficiency than its seeing now?








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Old 06-17-2013, 11:27 PM   #2
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Interesting hull (from what I can see) and used in hot sunny weather a lot.

She is not efficient either heavy or light.

If you have efficiency as a major need ..... find a full disp hull or a semi-disp hull that is, design wise, more like a disp hull.

One of the easiest ways to identify a full disp hull is that she will be basically double ended or have her transom out of the water at rest. That is ... the bottom of the transom will meet the aft edge of the bottom of the boat at or above the WL.

Planing hulls will require at least 3 times as much power (as a FD hull) to go roughly one knot below hull speed. Semi-disp hulls that comprise most of the trawlers here will require 1.5 to 2 times as much power.

Another thing to keep in mind is that narrow boats are considerably more efficient than wide boats. Long narrow light and with a minimum of wetted surface will be most efficient.
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Old 06-18-2013, 05:46 AM   #3
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15 gallons an hour on plane. 19 mph at 2900 rpms is the best I've seen"

Not very special 19 mph is about 15K

and 1 nm/gal is about what most plaining boats are set to do.

2900rpm is fine as cruise speed if the engine is gas, rather high for many diesels to maintain for 1/2 day.
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