We struggle to find ways to reduce our footprint as we travel. Striving to save the planet is hard work when you're designing and building modern high performance yachts. But there are steps we can take in the right direction without building our boats out of biodegradable materials or figuring out how to turn our old boats into compost for orange orchards.
For a start we need to stop thinking about our boats simply in terms of length (and how much stuff we can carry in that length), and start thinking about how much air and water we are pushing around as we travel. Whatever it is we need to bring along; sleeping cabins, bathrooms, sundecks and water toys; the answer is to spread it out lengthwise instead of stacking it in vertical layers. Thoughtful design is part of the solution.
There's a pretty basic formula that measures this ease of motion through the water. It's the displacement to length ratio (DLR). It compares hull length against the vessel's weight and it's a reliable measure of how much resistance we are working against in the water. It can be a reasonable indication of air resistance as well because if you're heavy and you're not that long it's a fair indication that you have a lot of superstructure above the waterline. More weight drives the number up. Longer hulls bring it down. The lower the number the better.
A low DLR comes with a host of benefits. Lower fuel costs, extended range from a given fuel capacity, less sail area to drive the boat if it's a sailing boat. Longer hulls provide a more comfortable ride. And if your profile above the water is modest you have lower centre of gravity which means less roll and less pitch.
In the Sensori range we've deployed two specific design features to enhance performance and promote a low DLR. The first is the reverse bow which promotes maximum hull length on the waterline for minimum cost, minimum weight and minimum windage. It's a no brainer solution for maximum efficiency. The second is the CS (canoe stern) hull shape which enhances performance by encouraging laminar flow over a significant portion of the under body. Both of these features are discussed in detail in separate articles you can find in The LAB.
NEW! SENSORI MS (Master Suite) Series
Sensori MS Series brings greater breadth and diversity to the Sensori Range. The same focus on a low displacement to length ratio for efficiency and range, the same V bottom hulls for sea kindly motion, contemporary styling in keeping with our existing Sensori cats and a host of features that will make Sensori MS stand out from the crowd at sea or in port.
So what's new? While the existing Sensori range has all of the sleeping accommodation in the hulls, Sensori MS features a generously proportioned master suite forward on the wing deck with easy access to a private ensuite in one hull and a walk in wardrobe in the other. There are guest cabins amidships with private en suites and for the charter version there is ample space forward for a crew cabin. The forward cabin in the charter version can be split into two cabins each with an ensuite, or kept as a single spacious owners cabin.
There is also a Sports version with a more modest flybridge and an Expedition version optimised for a low centre of gravity, minimum windage and maximum unshaded roof deck for solars.
While the earlier designs in the Sensori range have the helm station in the saloon as a standard arrangement, the MS series features the helm and navigation on the flybridge for the charter model, and an option of helm up or down (or both) on the Sports version. For the Exp. model the helm is in the saloon. The roof features a low coaming and the roof top deck can be accessed for lounging and viewing if not completely covered with solars.
The Charter and Sports models both sport a large sun bed area on the foredeck, and the option of a set of steps up to the flybridge deck as well as the primary steps from the cockpit. The Expedition model will still offer the sun bed lounge as an option but otherwise the focus is on light weight and a streamlined wind profile. All of the designs in the Sensori series are able to be adapted to new technologies including hybrid electric power systems as they become more cost effective. Variations on the 54 will be coming to the web site soon and there will be other sizes in the series available later in 2021.
The model in the image above is the charter version with an extended flybridge deck for maximum passenger space. As well as the accommodation spaces in the saloon there is deck space and seating in the cockpit, on the flybridge deck, and in a generously proportioned sun lounge arrangement on the foredeck.
Sensori MS54exp. Eat up the miles without gouging on the energy reserves. A trim profile and low centre of gravity deliver a comfortable ride, economy and maximum range.
Legs long enough to carry a flybridge with protective roof. Yes you can put a helm station up there but please don't close it in.
There's accommodation space for up to four double cabins with en-suites, and a couple of crew berths if you need them. Like the 52 there is space for a generous sundeck forward of the saloon with direct access through to the saloon.
Sensori 78 is a dive charter boat. She carries 12 guests in 6 double cabins with en-suites and has berths and bathrooms for up to 8 crew (5 is the normal compliment). The main navigation station is in the raised pilothouse and there is a second helm station on the flybridge but the flybridge is not enclosed. Sensori 78 carries a 5m tender on a lifting platform. She has a 3000nm range with twin Volvo Penta IPS drive engines.
Evolution in Hull Forms
Everything comes from something that came before. Technological advance comes from finding new combinations of existing technologies.
To quote Brian Arthur from The Nature of Technology;
“If evolution in its fullest sense holds in technology, then all technologies, including novel ones, must descend in some way from the technologies that preceded them.”
It's hardly breaking news that the combination of a slim hull and a canoe stern makes for a very easily driven hull form.
Add some stability in the form of outriggers or a second hull, add some pitch damping technology in the form of asymmetric water planes and you have a highly effective means of voyaging at sea under motor with good fuel economy and a sea kindly motion.
Malcolm Tennant put all these technologies together in the 1980's to create a highly successful hull form that he labelled the CS (Canoe Stern) hull. The success of the CS hull form is firmly established and aside from being deployed Tennant's own designs it has been adopted by the builders and designers of displacement motor yachts around the world, especially for long range voyaging in open ocean waters.
We've taken the CS hull form one step further by maximising the length of the waterline in relation to the weight of the boat, with particlar emphasis on the bow. This allows us to use a fine bow for easy penetration of the waves while still providing adequate buoyancy forward to minimise the chance of nose diving.
In the quest for more accommodation in a given length of boat, seakeeping and efficiency (including low fuel consumption) have all too often be overlooked. A high centre of gravity promotes pitching and roll. Longer hulls dampen pitching and reduce resistance. A lower profile and longer hull provides us with a lower displacement to length ratio, a sign of an easily driven hull and greater fuel economy. Longer hulls are ideally combined with the a reverse bow which is ideally suited to motor yachts with CS hulls because it optimizes waterline length without significantly increasing weight or windage.