Category C open boats?

Can someone explain to me in layman's terms what factors allow an open dayboat to be category C?

I thought one of the requirements was self bailing cockpit, but then I saw on Francois Vivier's site many designs that do not appear to be self bailing, yet are rated category C provided there are not too many passengers. Examples include Ilur and Ebihen.

 

C category is attributed to boats compliant with C category requirements. Compared with A category requirements :
- the structural strenght /minimum skin thickness is reduced
- the stability and buoyancy / Downflooding height and angles are reduced, Resistance to wave and rolling in wave is reduced
- the cockpit / Minimum height of the cockpit bottom is reduced, Maximum acceptable draining time is increased, Sill height of quick draining cockpits (partially enclosed or fully enclosed boat )
- security / Low gard-rail and high guard rail, hooking points, jack line attachement, footstop are optionnal

 

You will get better answers here to direct questions, than opinions of seeking unicorns on that other site. Cat C is an EU definition and I do not know if it has an accepted USCG parameter, though the stability and bouyancy aspects are both "similar" . You can have a small 14ft cruiser that is unsinkable and self righting from 180, but due to size, can never be in Cat A, despite having better "numbers", than some full size cruisers. The RCD was a way to lay down parameters for safety, but as few people who have lost their lives cant tell you, just because something has a plate saying Cat C rated, does not actually mean anything at sea. I wont mention the manufacturer, but it took some years to get the boat taken off the market, while people were still buying it and being put at risk.
The EC22 with a raised floor and flotation in the right places is a good start. The only downside is the requirement for a keel to keep it self righting with 8 people on board, where it could be much lighter and easier to trailer, if it was just a requirement that if she goes over, people float alongside.
My question to you, for a homebuild, do you need to get it USGC inspected in order to get it registered and insured?

 

Thanks Alan,

If I am interpreting correctly, under cat C decked boats with cockpits have a draining requirement, but open boats do not? Strange.

Skaraborg craft,

I'm just interested in this from a safety perspective, not a regulatory one. Here in California there are no safety requirements to have a homebuilt boat registered, as far as I know. The coast guard might stop you and make sure you have a ships bell, some flares and some pfd cushions, but that's about all.

If you are taking paying passengers then you need to meet USCG requirements.

 

Nope.. it is the Sill height (of compagnion way) of quick draining cockpits (partially enclosed or fully enclosed boat ) that is lowered in C category.

The draining time of cockpit is increased in C cat compared to A cat. Of course, if the cockpit is self draining, this draining time is not relevant, but you have to verify that the cockpit configuration is indeed self draining.

In short, self bailing cockpit alone do not give access to C cat. For instance, a self bailing cockpit with a too low bottom (to the water plane) will given access only the D cat for the boat.
A contrario, an enclosed cockpit is not sufficient to ensure a sufficient security level by itself. The draining holes should have the required surface area in compliancy with the draining time requirement (depending on a fraction of the total cockpit volume).

 

In which case, I would be happy enough to know the boat wont sink when flooded, and can be righted with minimum crew in case of capsize. In other words , basic common sense. I dont sail on a lake with +4 degree water in a boat that will sink or cant be righted, the same would apply if I was elsewhere with warmer water.

 

Thank you, that all makes sense.

However, you say "For instance, a self bailing cockpit with a too low bottom (to the water plane) will given access only the D cat for the boat." In the case of Ebihen 18, the cockpit floor appears to be below waterline at DWL, which I would think restricts the boat to cat D, but Vivier says it is cat C with 5 crew, cat D with more. This is why I'm confused.

Perhaps the drawing is at max load but with fewer passengers the floor is above WL and you can pull a plug and drain the boat?

 

This is quite sensible.

 

I think the open boat will be required to have buoyancy chambers that are sufficient to keep it afloat,but the cabin boat with cockpit needs to demonstrate that it will shed water quickly and effectively with calculations and measurements of height of thresholds and downflooding angle.The number of people on board will have an influence on this volume of water and the maximum number will be indicated on the RCD plate.The whole business is quite a bit more complicated and the manual for the boat will need to show escape routes,location of fire extinguishers and fire blankets together with the locations of skin fittings.The last time I was involved,I had to provide something like 28 different illustrations of systems within the boat.

 

The measurement of the cockpit height shall be full charge, and I see no seacock in the drawing. Then I assume that the cockpit is no self bailing one, but simply a watertight one. That way, with the requirements given by wetfeet, it may be possible for this boat to be in C category.

 

The complete answer to your question is in the application of ISO 12217-2 , not free of charge unfortunately, here below you have only access to the free preview. More exactly for your question :
** The Table 2 in chapter 6.1 Requirements to be applied propose you 7 options , 5 of which (3 to 7) being possible for any boat (i.e. not only fully enclosed one) and a classification in category C. For example, for C and not fully enclosed boat :
- option 4 includes requirements about : 6.2.1 Downflloding openings, 6.7 Knock-down recovery test, 6.9 Floatation requirements, 6.11 Detection and removal of water.
- option 6 ... : same but with 6.8 Wind stiffness test instead of 6.7 Knock-down recovery test
Likely that Ebihen 18 was classified under one of these 2 options.
ISO 12217-2:2022(en), Small craft — Stability and buoyancy assessment and categorization — Part 2: Sailing boats of hull length greater than or equal to 6 m

 

USCG small craft rules are separate from the ISO rules which the EU uses, though there are similarites in certain aspects. USCG small craft rules only apply to monohull motor and row boats under 20 feet in length. There are no USCG buoyancy and stability rules for sailboats of any size or any boats over 20 feet used for recreation.

The USCG does not inspect "small boats". The manufacturer self certifies, and the USCG may check the manufacturers certification. There are no USCG requirements for home built boats.

 

If true, I stand corrected. Odd why a company cutting and designing cnc kits for a plywood runabout would bother with the expense of stability and buoyancy testing, if the USGC didnt apply to home build boats.

 

The USCG rules do apply to boats built by amateurs from purchased "complete" kits which is why CLC and other kit makers now include capacity plates for some kits. The USCG requirements do not apply to boats built by amateurs from partial kits such as CNC cut plywood parts only.

For boats which require a capacity plate the builder decides how many passengers, the total load and power to put on the capacity plate and certify the boat as meeting applicable USCG requirements. They can determine these numbers by physical testing, computer modeling, pencil and paper calculations or any other method they chose. However the builder is legally liable for the boat meeting the applicable USCG requirements when loaded to the maximum capacity with the maximum power engine displayed on the capacity plate.

 

So, not so different from the RCD after all.