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Old 06-03-2008, 22:05   #16
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Isn't that a spoon bow on the Viking ship?
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Old 07-03-2008, 11:10   #17
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Wasn't just warships, but a lot of steamships from the turn of the century had this reverse sheer. Image:RMS Luisitania.jpg - Wikipedia, the free encyclopedia
Again, not very pronounced - just off of plumb, but the rake increases considerably below the waterline - sorry couldn't find a drydock photo.
Is this Lusitania Liverpool dry dock pictures from history photos on webshots the image you were talking about? It looks more like a plumb bow to me. I'm sure they were trying to ape the look of the leading edge warships of the time, but you'd be hard pressed to call that a true reverse bow. It's certainly not a wave piercing design.
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Old 07-03-2008, 11:31   #18
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if that reverse bow goes into a big wave .. it may just become the submarine that it looks like and keep going down for a while.
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Old 07-03-2008, 13:45   #19
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Isn't that a spoon bow on the Viking ship?
Here are some samples of spoon bows.........
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Old 08-03-2008, 06:26   #20
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See the G-Force reverse bow:
http://www.schionningdesigns.com.au/...GForce1400.pdf
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Old 09-03-2008, 01:45   #21
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I dont mean to be rude but the the "boiler stack" works for me It makes the boat look like one of the Super Steam trains at the end of the steam era. What I do think is hilarious is that the air conditioner and entertainment system is listed under "Propulsion" Apart from a small amount of water shedding I cant see how it makes a great deal of difference to a vertical or sharpy style bow. ...
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Old 09-03-2008, 04:28   #22
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There is a lot of sense in a reverse bow as it significantly reduces hobbyhorsing and subsequent loads on the rig. It is interesting to compare sodebo and the bows of the tri that didn't make it round.
The idea is to provide hydrostatic lift early, and to reduce the sudden impact of a bow hitting a wave. Overhanging bows have a shorter time of impulse when they encounter a wave as the angle of the bow more closely matches the angle of the wave and a flared bow increases the resistance to forward motion suddenly and strongly. The reverse bows have little resistance to rising.
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Old 09-03-2008, 04:50   #23
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Have a look at greek galleys and early phoenician cargo boats. They have quite a reverse bow. Another more recent boat is 'Backslash', a small sailing cat.
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Old 09-03-2008, 11:28   #24
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Have a look at greek galleys and early phoenician cargo boats. They have quite a reverse bow. Another more recent boat is 'Backslash', a small sailing cat.
Robert
You know, that brings up an idea. If one were to build in a forward bulb similar to the ramming ships of the greeks or the tankers of today, it could be used as an intinuator to reduce collision effects with objects at sea.



Trireme

This would be fairly similar to a reverse bow or the modern Cats. I'm curious how it would react in a rough sea.
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Old 09-03-2008, 12:17   #25
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The original photo's of those megayachts look butt ugly in my opinion. And I really can not see the point. Sailing vessels have a very different reason for a bow like that. A powered vessel, of which this Forum is about" requires a very different approach to taking on large sea's and I can only say that to have a bow like that, you'd have to be nuts.
Bow Bulbs on ships is a very different reason compleatly. The bulbs are often full of fuel or water, so don't always offer xtra flotation, however, extra bouyancy on the bow is sometimes done this way. I know of several boats here that had this type of design done with the main priority to give the bow a lot of bouyancy. Personly, I feel it was because the original design never worked properly and the bulb was an "idea" to solve an issue in the design.
On large ships, that bulb is to change the bow wave and reduces large amounts of wave height moving out from the vessel. The size of the wake is a direct proportion to the amount of energy the ship requires to move through the water. So reducing the wake means less power required to push it along. Not greatly measurable in smaller vessels, but in large megaton vessels, small percentages of efficiency gains equates to large savings in fuel. Some of those huge container vessels can be burning fuel at a rate of upto 10tonnes/hr. The bulb also lengthens the water line which results in extra speed or reduced effort once again. It's quite amasing to find such small wakes behind many of the newer modern ships of today. Environmental impacts are trying to be reduced as much as possible.
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Old 09-03-2008, 12:38   #26
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You're probably right for small vessels. I've been doing some research while away. But there are advantages with longer vessels.

Cautionary Note

Bulbous Bow

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Old 09-03-2008, 12:41   #27
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Not greatly measurable in smaller vessels, but in large megaton vessels, small percentages of efficiency gains equates to large savings in fuel.
Nordhavn did some research on bulbous bows. If I remember correctly, they said something like 55-60' was the point where a bulbous bow became, on the average, more help than harm on a full displacement hull. Their 62' has one.
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