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Posted by Jon Taft
on 10/22/2009, 8:31 pm, in reply to "Off the subject: skiff load capacity"
24.128.68.172
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: Can you explain to me how a little
: skiff with only twin 75 HP Yamahas could
: load and handle 4 tons? Go to the HI RES
: photos: http://www.navy.mil/search/display.asp?story_id=49106
Hmm, pretty big "skiff", I think the USN RIB pulled up next to it is a 24 footer. The "skiff" is about 1.8x that length or around 40', though the LWL looks more like about 35'. The skiff has a fairly high prismatic coefficient (narrow beam compared to length) and is probably moderately efficient. The twin Yamaha 75hp engines (total 150hp) would probably not have much problem driving it loaded at displacement hull speed which would be about 8 knots [1.34 * SQRT(LWL)].
As to load, the "skiff" looks pretty heavy (fiberglass or wood/glass) but has no deckhouse and apparently no inboard mechanical gear. The empty boat probably weighs 5000-10000 pounds. Adding a load of people and 8000 pounds of drugs would not be too difficult. The midships beam at the gunnels looks to be about 9 feet. The boat is narrower than that at the waterline and narrows to a point at the bow. Just as a total guess say the average waterline beam over the whole 35' LWL is about 6' That would give a waterplane area of 210 sqft. Seawater weighs about 64lbs/ft^3. That yields a ppi (pounds per inch immersion) of 1122 lbs/in. So 8000 pounds would drop the boat about 8 inches in the water. And, indeed, looking at the picture the boat does look a bit down on its line (especially in the 2nd picture below).
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