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Old 21-03-2007, 07:07   #1
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Nomenclature question

I notice that most of the modern production boats have the bow drop almost vertically to the water. Connemara's bow, OTOH, slopes sternwards sharply, and eventually makes about a 60-degree angle with the water (or 120-degree if you look at it the other way).

Is there a word for that angle?

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Old 21-03-2007, 07:22   #2
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Rake would be my guess.
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Old 21-03-2007, 07:28   #3
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Ricks guess is spot on - bow rake is the answer.
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Old 21-03-2007, 07:56   #4
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The newer "almost vertical" rake is also referred to as a "plumb bow" in several advertisements, ie Hylas.
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Old 21-03-2007, 08:33   #5
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I would have thought that referred to the tilt of the mast, but shows what I know.

I was thinking it was "sheer" so now I dunno what sheer refers to.

Oh, the puzzlement.

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Old 21-03-2007, 08:36   #6
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http://web.nps.navy.mil/~me/tsse/NavArchWeb/1/module2/basics.htm

Sheer: The rise of a deck above the horizontal measured as the height of the deck above a line parallel to the baseline tangent to the deck at its lowest point. In older ships, the deck side line often followed a parabolic profile and sheer was given as its value at the forward and after perpendiculars. Standard sheer was given by:
sheer forward = 0.2L +20
sheer aft = 0.1L +10
where sheer is measured in inches and L is the length betweener pendiculars in feet. Actual sheer often varied considerably from sheer these standard values; the deck side profile was not always parabolic, the lowest point of the upper deck was usually at about 0.6L, and the values of sheer forward and aft were varied to suit the particular design. Many modern ships are built without sheer; in some, the decks are flat for some distance fore and aft of midships and then rise in a straight line towards the ends. Sheer increases the height of the weather decks above water, particularly at the bow, and helps keep the vessel from shipping water as she moves through rough seas. Some small craft and racing yachts are given a reverse or hogged sheer to give headroom amidships without excessive depth at bow and stern.
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Old 21-03-2007, 08:37   #7
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Rake: A departure from the vertical or horizontal of any conspicuous line in profile, defined by a rake angle or by the distance between the profile line and a reference line at a convenient point. Rake of stem, for example, can be expressed as the angle between the stem bar and a vertical line for ships with straight stems. For curved stems, a number of ordinates measured from the forward perpendicular are required to define the stem shape. Ships designed so that the keel is not parallel to the baseline and DWL when floating at their designed drafts are said to have raked keels, or to have drag by the keel.
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Old 21-03-2007, 08:48   #8
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Hah! Knew I could count on this forum for more info that I can handle. Like trying to drink from a firehose, some days.

Thank you, Rick.


Connemara.

(PS...only a few more weeks until launch, down here in sunny Toronto.)
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Old 21-03-2007, 09:07   #9
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Quote:
Originally Posted by Connemara
(PS...only a few more weeks until launch, down here in sunny Toronto.)
Keep an eye out, you might see the CCGS Martha L. Black breaking ice up your way. She passed through here yesterday opening the Seaway for the season.
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Old 21-03-2007, 09:22   #10
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In a similar vein. My bow is not a straight line (profile viewed from the side) but curved. I would suspect there is a name for this (and probably more math to do). Anyone know what this would be called?
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Old 21-03-2007, 12:41   #11
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Quote:
Originally Posted by Connemara

Is there a word for that angle?
Also know as "positive buoyancy". These "raked" bows HELP to keep the bow from nose diving into a swell/wave, which keeps the boat on top of the water. It's most common on race boats to help keep up the speed in the rougher weather.

The plumb bows have been showing up more recently on the production monhulls, I would guess to get more waterline/interior for ones boat. I'm not sure I'd want one for off-shore unless it had a lot of freeboard.............._/)
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Old 21-03-2007, 12:46   #12
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Quote:
Originally Posted by FrankZ
In a similar vein. My bow is not a straight line (profile viewed from the side) but curved. I would suspect there is a name for this (and probably more math to do). Anyone know what this would be called?
Either a "Spoon" bow or "Cruiser" bow. The cruiser being more straight up at the deck joint............................_/)
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Old 21-03-2007, 12:49   #13
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I think the plumb bow is driven by racing rules, so that you can get maximum LWL without going over a LOA limit. Why they are common in production "cruising" boats is anybody's guess. They don't give sufficient reserve buoyancy and from what I can tell, tend to throw up a lot of spray. To top if off, they don't look as good as a steeply raked bow.
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Old 21-03-2007, 13:00   #14
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Like cars, boat design is often driven by current racing design. Most street worthy cars are not track worthy, but that does not keep the marketing people for trying to sell cars with a sporty feel.
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Old 21-03-2007, 14:33   #15
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Quote:
Originally Posted by delmarrey
Either a "Spoon" bow or "Cruiser" bow. The cruiser being more straight up at the deck joint............................_/)
Thanks.. I like the looks more than a hard edge, whether raked or not (ok, so I like plumb bows even less).

Boats are like women, they should have curves and be well proportioned.
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