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Old 12 August 2008, 07:50   #1
Country: UK - England
Length: 6m +
Join Date: Aug 2008
Posts: 32
Cat B seaworthyness?

Hey Guys,

Super quick Q for the more experienced among you...

What exactly do the different Category classes relate to? I know Cat B relates to "upto force 8 seas with waves of up to 4m in height"... but what do the others give indication of in relation to how seaworthy they are?


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Old 12 August 2008, 13:41   #2
Bigmuz7's Avatar
Country: UK - Scotland
Town: Glasgow
Boat name: stramash
Make: Tornado
Length: 5m +
Engine: Etec 90
Join Date: Feb 2006
Posts: 5,064
I only have experience of Cat C & B boats, and I have reached the conclusion the CE marking is a sales aid only for distribution of boats in Europe. It is not a code for the quality, or integrity of construction of the hull.

I was lead to believe that a cat B hull would, by its rating, be stronger, harder, extra layup, stronger internals etc and more seaworthy than a C, and to some extent they are, in that it is a bigger boat,.. but that is where it ends.

If its a poorly constructed bigger boat as I found to my cost with an 8.5 Northcraft cat "B", you can forget placing any credence on its cat rating. To be fair, part of this crafts problem was that the manufacturer plated the transom to carry horsepower it couldnt handle.

But also, and this is important ..because of the weight distribution and layout of that boat, it was far too bow light, and to be honest taking a sea head on in a big six or seven was a challenge, so .. as to your question of seaworthyness, even supposing it was a top spec boat coded for B, if it aint balanced, or fitted in such a way as maintain good seakeeping, you can forget the cat system as having any real importance.

Ah just seen your other thread and posts

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Old 13 August 2008, 12:21   #3
MarkM's Avatar
Country: Netherlands
Town: Breda
Make: Scorpion
Length: 7m +
Engine: Evinrude 250 DI
Join Date: Oct 2003
Posts: 368
A = Ocean, force >8, waves >4 m.
B = Sea, force <8, waves 2-4 m.
C = Coastal waters, force 4-6, waves 2 m.
D = Inshore waters, force 4, waves 0,5 m.
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Old 13 August 2008, 13:35   #4
Country: UK - England
Length: 6m +
Join Date: Aug 2008
Posts: 32
Brilliant, Thanks gents.
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Old 13 August 2008, 16:20   #5
Country: UK - Wales
Town: swansea
Boat name: Too Blue
Length: 8m +
Engine: Suzuki DT225
Join Date: Mar 2004
Posts: 12,791
I agree the ratings are a joke. Some makers will be over optimistic and others will err on the side of caution so you can have a 9m RIB with the same C rating as a 3.1m dinghy!!!
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Old 14 August 2008, 03:08   #6
Country: France
Town: Cannes
Boat name: midkat 550
Make: apoge
Length: 5m +
Engine: 2x50 Tohatsu
Join Date: Jan 2008
Posts: 126
I agree - 100% - with bigmuz statements.

Now, Cat B requires more than 6m in length, that's all - and you could find several italian ribs with this category - and in the 4 to 4.5metre range - because italian had a different definition of distance off the shore, as their C category was limited to 4 miles.

No rough sea testing is required, unless a handling test at max speed on flat sea to check the ability to turn left and right in a short define distance.

Concerning the hull ability to sustain waves, it is the manufacturer responsibility to build strong enough

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