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Old 12-28-2012, 08:13 PM   #21
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Greetings,
Or keeping abreast of the newest technology.
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Old 12-28-2012, 08:22 PM   #22
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Maybe the owner of the tanker was a "Boob" man!
Apparently so as he ran aground.

My question would be even if a bulbous bow made a measurable difference on a 40-50 foot boat, would it be enough to make it cost effective to add one?

My initial feeling is no.
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Old 12-28-2012, 09:21 PM   #23
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Quote:
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Maybe the owner of the tanker was a "Boob" man!
Who isn't?
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Old 12-28-2012, 10:00 PM   #24
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So, should we classify these bow shapes between phallic and mammalian?
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Old 12-29-2012, 09:48 PM   #25
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Quote:
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Apparently so as he ran aground.

Actually they had a smoking problem. Ship was in transit and part of the crew was cleaning a couple of ethanol tanks while someone was smoking (you can't make this stuff up). A fire starts and all but 6 of the crew come on deck to fight the fire. It's late in the afternoon and a fishing vessel (some miles to the west) sees the Sun setting in the West and the remaining ethanol (3.5 million gallons), diesel (48,000 gallons), and fuel oil (193,000 gallons) tanks explode in a massive fire ball to the East. The captain of the fishing vessel describes the ball of fire as a new Sun rising to the East. Another fishing vessel (30 miles to the North) describes the fire as being visible with flames hundreds of feet in the air, and the explosion sending flames thousands of feet in the air.

Note to self: No smoking aloud on any of my boats!

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Old 12-30-2012, 10:02 AM   #26
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Steve Dashew has reported that some think bulbous bows on smaller hulls present more of a tripping hazard in large following seas as the vessel will tend to bow steer. Hollywood raises a good point, no Nordhavn designs have incorporated them for over 16 years.

The most rigorous tank testing on smaller vessels has been in sailing fraternity. No bulbous bows there.
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Old 12-30-2012, 11:14 AM   #27
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The efficiency of a vessel is measured by how much power it takes per ton of displacement to be driven and for a bulbous bow to even stay attached in rough going it must be very heavy. So to just break even it must overcome that large increase in weight PLUS the extra skin friction drag just not to be a loss. So it appears the benefit would need to be great just to break even and overcome it's own penalties. And their benefit is only available at a certain speed since their whole function is dependent on the length of the vessel's own wave starting at it's bow and becoming longer and shorter depending on speed.

Probably would work on Willy though as we almost always go 6.15 knots. The whales of McKay Reach may view it as a battering ram though.

I think it would be better and not any or much more trouble to just make the boat longer. And considering that a great deal to most BBs are fitted to vessel's with very raked bows so just a plumb stem like the Titanic should get much the same result. But the plumb stem would probably not fly in our "in w the new out w the old" mentality of our pop culture. New is always better even if it's not.

So the possibilities for a BB on small boats is limited at best and the only weak possibility exists almost exclusively for full disp boats. And there are VERY few of them in the powerboat world.
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Old 01-01-2013, 12:41 PM   #28
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bow bulb

Not sure what the cargo is, could be grain or lumber products but it's heading downstream on the Columbia. Video taken last year while returning a 65ft feadship to Portland from San Juan Island for the owners.
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Old 01-01-2013, 12:55 PM   #29
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Slowboat,
I've seen the BBs at work too and it's amazing how they lift all that water up and recoup all the energy it takes to do that. Notice also here that the WL is considerably below it's static line as can be seen to the right of the video arrow. Once all that water starts moving away from the hull it wants to keep going .. away from the hull and that inertia pulls the water away from the hull as seen here at the WL to the right. But perhaps they don't do so well after all but lots of vessels of this type have them. And you'd think if they didn't pay for themselves you wouldn't see them in numbers.

Feadship. Beautiful boats and partly because there's no bow pulpit. I remember them from Motor Boating magazines of the early 50s. Top class boats. My dad gave me a subscription to Motor Boating. I think they still make Feadships.
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