A question for my learned friends.

[Shifty]

I purchased an Atlantic 460 last year, which is a category A vessel. I am intrigued as to how they arrive at this as a lot of bigger boats Sunseeker/Princess/Fairline etc, are Cat B.
I‘m certainly not not one of those who thinks they can venture out in any weather, but would be interested in peoples views.

 

[Chris_d]

An old question

(59) Cat.A or B ? What makes the difference? | YBW Forum

Same boat could be A or B its up the manufacturer to go the extra bit if they feel the need.

 

[Shifty]

An old question

(59) Cat.A or B ? What makes the difference? | YBW Forum

Same boat could be A or B its up the manufacturer to go the extra bit if they feel the need.

Thanks for the link, I’ll browse later.

 

[philipdawsonladds]

I've got an Atlantic 42 and am also confused. The rating plate shows Category B - 6 passengers - 3500Kg. My previous boat was a Sealine SC35 which was also rated B but for 10 passengers and 1000Kg. Seems odd, much bigger boat with a lower passenger rating.

 

[Tranona]

RCD categories are complicated things. The biggest differentiator between Cat B&A is stability - the ability to cope with waves of a particular height without capsizing. Generally speaking planing hulls with relatively shallow draft and high topsides are poor in this respect compared with displacement and semi displacement boats - nor are they actually very good performers in heavy weather. In reality few planing leisure boats ever venture out in heavy weather so not so important to have Cat A - even if it could be achieved. The passenger load within a category will depend on the displacement and spread of weight therefore designers will aim to get the sort of carrying capacity that reflects the target market. It is also important to note that the categories also determine design features such as weather tightness - opening hatches and doors plus levels of safety equipment.

It really is not sensible to compare the rating on two different styles of boat like an Atlantic (which is based on an all weather commercial boat) and an SC35 which is a weekend fairweather high speed runabout - but bigger. Not intended to knock boats like the SC35 but they were never designed for serious offshore work.

 

[Shifty]

I've got an Atlantic 42 and am also confused. The rating plate shows Category B - 6 passengers - 3500Kg. My previous boat was a Sealine SC35 which was also rated B but for 10 passengers and 1000Kg. Seems odd, much bigger boat with a lower passenger rating.

I share your confusion, I also had a a Sealine previously (S43) and that was recommended 12, yet my bigger Atlantic CatA is 7 persons.

 

[SC35]

I've got an Atlantic 42 and am also confused. The rating plate shows Category B - 6 passengers - 3500Kg. My previous boat was a Sealine SC35 which was also rated B but for 10 passengers and 1000Kg. Seems odd, much bigger boat with a lower passenger rating.

What's on the plate is what the manufacturer decided to certify.
This generally matches with the intended use of the boat, but sometimes results in anomalies.

What it does NOT mean is that taking out an SC35 with 10 people on board in 4m waves is a great idea: you might not sink, but there could be damage and the people on board might sue for PTSD.

My interpretation of the categories:
RCD D: The tender
RCD C: Speedboat, RIB, Small Cruiser not too far from shore, or in company
RCD B: Cross Channel, but you need to look at the forecast
RCD A: You will give up before the boat does

 

[Chris_d]

I share your confusion, I also had a a Sealine previously (S43) and that was recommended 12, yet my bigger Atlantic CatA is 7 persons.
View attachment 130565

Its about the category and the number of people, to meet cat A it can have a maximum of 7 people in the worse possible location e.g all sat up on the flybridge/helm, it could probably carry more people very easily but wouldn't meet the stability rating if they all sat up top at the same time, so would only be cat C or B. Hence the SC35 can have more people in its low down cockpit and meet Cat B requirements, but more than 7 on the flybridge of the Atlantic and it would be too unstable to meet Cat A so be downgraded to Cat B.
Atlantic are trying to sell to serious cruising folk so a Cat A rating gives it credibility, they will not be the target audience for the SC35 which may appeal more as a party boat

 

[ari]

I share your confusion, I also had a a Sealine previously (S43) and that was recommended 12, yet my bigger Atlantic CatA is 7 persons.
View attachment 130565

The Sealine wasn't 12 at an A rating though.

Sometimes they have a people rating at 2 levels, so 7 at A, 14 at B for example. But that's the reason this is 7 and the Sealine 12, because it was at a lower threshold.

 

[Tranona]

The Sealine wasn't 12 at an A rating though.

Sometimes they have a people rating at 2 levels, so 7 at A, 14 at B for example. But that's the reason this is 7 and the Sealine 12, because it was at a lower threshold.

Yes, common to give 2 ratings for sailboats as well. My Bavaria 33 is 6 at Cat A and 10 at Cat B. They do this because many European states use the CAT ratings for licencing - so my boat could get an inshore commercial licence for 10 people and 6 for offshore. This is a lazy way of coding compared with the UK which has its one commercial code with much higher standards. Same would apply to motor boats.