Superyachts with Open Side Windows in Aft Beach & Garage Areas

Looks like the latest Feadship "JOY" just appearing on the frontpage is another take on this. The tender garage on the bow is fully open. There would be a lot of water going through there in transit, so maybe temporary coverings are a part of the design.

I feel Joy would only have to worry about the 3000gt requirement, right? She's sort of in the middle of classes

T.K., I know which yachts and yards you are talking about. There are a lot of advantages for a yard keeping the GT below 500. Build and design rules are a lot easier (and cheaper). A yard which is able to build a 600 GT yacht as a 499 GT boat, has a ompetitive advantage, because of the lower purchase costs and operating expenses.

The problem with using this "trick" is convincing the clasification society, that those "movable side covers" and sometimes also rear ones are not representing an enclosed body. But the yards you are talking about are great with their arguments regarding volume. Like for example fixed deck stuctures being decleared loose furniture with just temporary storm protection . But all examples I have seen, were at or above main deck level and therefore not relevant for buoyancy or other safety concidarations. Just a matter of point of view and the flexibity of the classification society and the genius of the designer and NA.

I know of one larger yacht, where one aft deck can be completely surrounded with sliding glass panels, building a climate controlled upper salon. Class had mandated on this boat, that this encloser should not be used with the yacht on voyage. Doing othervise would be violating class.

But Quattroelle for example has the same feature on the upper aft deck, where a large totally enclosed salon can be arranged by sliding glass panels. Even the stairways can be closed. This salon can be heated and airconditioned. If you add the volume of this salon to the GT of Quattroelle, she will break the 3.000 GT border easily. But there is no restriction about the use of this feature in her classification paperwork.



Will say, when using a cooperative classification society (like RINA ), you will most likely end up with no restriction on this great feature. But just some opening side walls will not turn internal volume of a yacht into open deck space. You have to make class able to stay legal. A good naval architect and designer will know the differences. Trying the same design feature with NVGL, MCA or ABS, you may end up with restrictions or totally different results.

The partially open forward tender and service deck on the Feadship Joy will also not present a problem, as long as the green water entering this deck during higher seastates is able to float off the boat in the mandated manner and time. Interesting and really new feature.

Google "tonnage openings" to learn how such design features are used to circumvent certain regulatory issues related to tonnage measurements. Read the class rules for specific requirements.

Generally, no. Flag states may dictate specifics but typically any tonnage hatch or closure must be equal in strength and watertight integrity to the surrounding structure.

That is more a matter of seamanship than safety or regulatory issues.

T.K., if you are specifically talking about this aft beach club, I have my doubts about the conformity of the GT calculation of this 499 GT boat.



Just by using grids on both sides of the hull and the stern hatch with some sliding panels behind the grids and moving the watertight bulkhead forward of this area, will not turn this obviously integral part of the hull into open deck space. IMHO this "beach club" should count with its volume for the GT of this yacht.

Each rule has its "bandwidth". In some countries (like mine ) they may have the width of a raser blade, in others it seems they may have the width of a four lane road.

If this area is the deducted volume accepted by RINA, which makes it a 499 GT yacht, my (kindly meant) statement about RINA being very cooperative, is really true.

Just my 2 (Euro) cents

When I was in the brain storm and design phase for my present sailboat, I decided very early, to stay below 500 GT and (because its a sailboat) below 50 Meters in length. One has so many (I would say only) advantages by staying below 500 GT.

I am not talking about MCA classed, commercially used (charter) yachts. Just a yacht for private use. With staying under the above mentioned limits, we could build the hull as a single body (not counting the forward and aft collision bulkheads), had no requirements for a dedicated SOLAS rescue boat (also one RIB is equipped as a rescue boat), no requirement for an emergency generator in a dedicated compartement above main deck (we only have an independent diesel driven fire and bilge pump in the aft lazarette), less crew requirements with lower licensing, much simpler but still very effective fire figthing equipment.

If shopping for the biggest possible 499 GT yacht, I would still leave the hull alone. The hull stands for buoyancy, stability and seaworthiness, means safety. If you need to deduct about 100 GT from your design in order to reach 499 GT, do it on the superstructure.

I would start on the flybridge by removing fixed elevated sunpads, some optional fixed flybridge furniture, omit a jacuzzi, if neccessary and exchange the alloy hardtop (with frames and stringers) with a much thinner piece of CRP.

By carefully reviewing each deck, 100 GT can be achieved, without opening the hull. Remember, 100 GT are just 2,83 cbm.

Further to these open areas like on Joy. My first impression was what wonderful places these must be for the crew to hang out in.