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Mobirise

The ship, concept and design

Dimensions | Design | Performance & Safety

Concept

As you can read in "The crew ,” we want a ship that will take us longer distances quickly and comfortably (as compared to going in and out of a harbor on a daily basis) and be a pleasure and a challenge to sail, as well as one that will lend itself to slow and gentle contact with whales and dolphins. We chose a catamaran over a monohull design for a lot of reasons, including lightness and speed, form stability, minimum heeling, more total usuable space than a same-length monohull, better rigging and handling, more comfort at anchor, ease in and out of the water to visit the whales and dolphins, and especially safety (it's virtually unsinkable).

Dimensions

The length on deck (LOD) of the Cachalote will be just under 65 feet (19.8 meters); the length at the design waterline (DWL) is just under 63 feet (19.2 meters); and the beam width amidships (BOA) is just over 35 feet (10.6 meters).
The ship is designed to sleep 14 people very comfortably - 4 crew and 10 passengers.

(For the experts: BWL of each hull 5'2", BMax per hull 7' 6", Draft in cruising trim, 3'9", Freeboard 7'6" in cruising trim, Cruising displacement, 45,000 pounds)

Design

The overall design of the Cachalote is based on the BigCat 65, designed and copyrighted by Tim Dunn of BigCat Catamarans. The drawings on this page are very early drafts of modifications to Tim's design to better suit our needs.

The BigCat 65 has many watertight compartments, greater privacy for the cabins than is usual, full engine rooms with shaft drives rather than saildrives, and is light for its length. The lack of berth "shelves" makes for simple construction, and because there are no "shelves," they can't make wave slapping or slow the boat.

This boat should move right along as it has a long waterline, narrow hulls, light displacement, and a large sail area. The rig is low and easily handled, so there is no struggle or anxiety involved in getting the best out of its performance potential. The vessel has a high bridge deck with over 3 1/2' clearance in cruising trim. Even overloaded to 70,000 pounds of displacement, there is a 3' bridge deck clearance.

The sterns are designed to have low resistance even if the vessel is drastically overloaded; and if overloaded, the hull beam and length keep the 12 to 1 ratio as the beam and waterline length increase proportionally. The low 1'2" hull draft (at 45,000 displacement) makes a shoal draft possible while still giving good lateral resistance due to the ample keels and skegs. This low hull depth is possible because the high-tech materials and construction, long length, and the relatively modest accommodations for a vessel of this size add up to a very light boat which displaces little water for its length.

The hull construction uses a radius chine design. A radius chine design is a hard chine design where the chine has been replaced with a semicircle to soften the turn of the bilge. This design has a 2' diameter at the turn of the bilges in all sections intersecting with the chine. Despite the large 2' radius, only 2% of the displacement has been removed from the chine version by softening the turn of the bilges. The diagonal measurement of this radiused area is about one foot.

The "V" section is carried right aft, insuring that the hulls will not slap even if anchored in an open roadstead. The transoms are well tucked up and the quarter beam buttock line exits at a very low angle, guaranteeing speed under sail. The bows are narrow at the waterline, have no bow overhang, and yet have a lot of reserve buoyancy to prevent burying the lee bow, because the deck is much wider at the deck than it is at the waterline at the bow.

This design has been thoroughly inspected by the engineers of the United States Coast Guard's Marine Safety Office in Washington D.C., in an exhaustive 10 month review process, and they have approved the design, scantlings, construction, rig, and equipment.

The hull and deck scantlings were designed to ABS Offshore Yacht rules, and the crossbeams to Lloyd's. All plans and details are compliant with CFR 46.

(SOLAS exempts vessels that carry 12 passengers or less on international voyages, so this design does not need to meet SOLAS requirements.

Performance & Safety 

There are watertight compartments in the hulls and full polyurethane foam floatation in the bridgedeck greatly exceeding the cruising displacement. The boat is designed to float high out of the water even if completely holed or upside down.

There is excellent all around visibility from the helm.

Kobelt hydraulic steering is specified.

Bill Roberts' K Factor of 3.3 (which is governed by the DWL to BWL ratio) predicts a maximum speed of 26 to 26.5 knots.

(For the experts: Prismatic coefficient of .65. LCB 36.25, LCF 35.9, PPI per hull 1345#, Hull Draft 1'2" at 45,000 displacement, Footprint Weight 19.5 pounds per sq. ft. - standard cruising catamarans are about 26 - DWL/BWL of hulls, 12.125. Bruce Number @ 45,000# 1.38, Air draft 70', Sail Area to Disp. ratio 30.35 at 45,000 displacement, Displacement to Length ratio 78.5 in cruising trim with full tanks, 61 lightship.)

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Sails and rigging

The masts have no stays and no potential failures due to stainless stress or corrosion fatigue.

The rig is a fully-battened WingSail, easily reefed and furled.
The maximum and working sail area is 2400 square feet (223 square meters).

The biplane rig is completely self-tacking and requires no sheet winches, despite its large sail area, due to its balanced design and 7 to 1 sheet purchase. Because the sail can be made as separate panels, which may be attached to the battens rather than each other, and because it has no camber cut in it (the camber coming from the hinging battens), no sailmaker is needed.

Another benefit of giving the rig its camber using batten hinges is that the sail draft is not affected by mast bend, which has been a problem in efforts to combine Marconi style sails with unstayed masts. This rig saves the builder 25% to 33% of the cost of building the boat.

It uses the Clark Y foil, recommended in an article by aerodynamic scientist and multihull sailor, Tom Speer.

This rig is as weatherly as a fixed keel catamaran can take advantage of, and the use of the biplane layout means that the sails will not back wind each other when running downwind. On a beam reach, the windward sail is slacked more than a marconi mainsail, the lee sail is hardened in more than a marconi mainsail, and they form, in effect, a single airfoil when seen in overview. This rig is capable of tacking through at least 90 degrees, and cruising catamarans are rarely capable of that.

Engines

The engines are ensconced in their own spacious engine rooms, where their noise and fumes are isolated.
The engines we have chosen are Deere 4045TFM-135 hp.(M3) 4 cylinder engines run at 2/3 of their rated speed (106 hp. each,) which would push the boat at up to 13.5 knots at 45,000 of displacement, and up to 10.8 knots if the boat were overloaded to 68,000 pounds of displacement. The Deere engines would between them use 5.2 gallons per hour at 1800 rpm, though they can use up to almost 8 GPH each run flat out. Running one Deere engine only at 1800 rpm. (a common practice on catamarans,) would push the vessel at up to 9.5 knots at 45,000 displacement, burn 2.55 GPH, and give a range of about 1500 miles. (There are 440 gallons of diesel tankage under the cabin soles.) These engines are said to be good for 20,000 hours.

With these Deere engines, ZF 63A 2.05 to 1 transmissions would give the boat 23" diameter propellers. Luke feathering propellers would be the choice for the props, located in front of balanced rudders which are fully protected by skegs and rudder mounting struts. We would use Racor 500MA fuel filters with bronze seacocks and cooling water filters, and fiberglass lift mufflers situated so as to be unable to flood engines under any circumstances

Mobirise

Hull cabins

The two hulls would be virtually identical.

Each hull would have two double cabins with queen-sized beds (60"x80", 153cmX200cm). Both double cabins would have private heads with toilet, sink and shower. Entry to both cabins is by stairs from the bridgedeck Salon; therefore, access to each cabin is protected from the weather.

In the bow of each hull is a single cabin. There is a possibility to have a sink/toilet combo as well in this cabin. However, access to this cabin is through an exterior drop-through hatch and is therefore most suitable as a crew cabin rather than a guest cabin.

Each hull houses an engine, as well as a fuel tank, a water tank, a sewage tank and a macerator under the cabin soles.

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Bridgedeck

The bridgedeck contains two cabins, the galley, and the Salon.

Each cabin has a queen-sized bed and its own private toilet and sink. There is a shared shower between the two cabins.
The galley has a refrigerator, propane stove, sink, and electric dishwasher.

The Salon is what's so unqiue about this design. It measures about 12 feet (3.7 meters) by 20 feet (6 meters). The Salon is where we will eat, so it must seat 14 people comfortably at tables. But it is also where we want the entire group to be able to meet in a circle, watch movies, dance, have a workshop, lounge around, etc.

Therefore, the dining tables will be removable and stowable out of the way - the same kind of design as in many motorhomes and travel trailers, with stainless steel supports that slide into a receptacle in the floor. The chairs will be stackable and stowable into a compartment to the left of the internal wheel.

All around the Salon - to the bow, starboard, and port - are 3-foot-square windows that open and lay flat on the top of the hulls, allowing the Salon to be completely open to the outside when the weather permits. The roof of the Salon will also be strong enough to hold ten people for sunbathing, meeting, or sleeping.

Solar pannels

Over the exterior bridge will be a fixed shade approximately 2' x 8', large enough to mount two KCM85 solar panels on top, for example. According to Kyocera (the manufacturer), these two panels could produce a maximum of 170 watts (17.4 Rated Voltage and 5.02 Rated Current).

We mention Kyocera because they claim "not all solar panels are created equal especially in Marine applications. Most solar PV panels of lower-cost are designed for use in residential applications. Beware these panels will not survive when installed on a vessel or near the water as they will delaminate, corrode or deteriorate and the manufacturer will not warranty their product accordingly. Our KYOCERA family of KCM solar panels have demonstrated successful and reliable operation over the years in a Marine environment and is backed up by the factory warranty. The Junction box is water resistant and we supply each unit with special watertight cable connectors leaving nothing to chance." (Kyocera's website)

However, Solarland offers a very similar panel in their Model SLP85-12 at a slightly cheaper price. (Solarland's website)
And the Sunware SOR70069 offers a little less power, but claim that it "runs cooler" and "have the highest power output to surface area ratio of semi-flexible panels on the market." (Even though our shade roof is fixed and rigid, we wonder whether there is any advantage to a semi-flexible panel (3cm over 1m) anyway. (Sunware's website)

We are hoping to hear from anyone with experience with these solar panels - especially in terms of operation, reliability, and maintenance - that would help us make our decision. Please email us.

Wind generators

We want two wind generators (for redundancy, in particular). They could either be fixed to the shade roof over the external bridge on the two aft corners, or they could be mounted on the outside edge of each hull at the rear beam.
From everything we read, Southwest Windpower is the undisputed leader in the field with their Air Breeze model. (Air Breeze website)

But what about the D400 direct-drive generator from Trans Marine (Trans Marine's website), or the Rutland 913 by Marlec (Marlec's website)?

What also looks interesting is the Forgen 500NT from Goodridge Engineering, with no rotary blades, super-quiet operation, and no need to disconnect in high wind. But we've also read some questionable reviews.

And is there an advantage to buying a hybrid wind/solar kit, for example with an Air Breeze or Rutland 913 wind generator and two Kyocera KCM 85 solar panels? (offered by eMarine Systems)

We would really like some feedback. Please email us.

Desalinator

There's no question that we want reverse osmosis desalinating capability on the Cachalote, able to produce about 400 gallons (1500 liters) per day. Obviously, that's more than 14 people would need, but we also hope to eventually run the ship's engines on water (see below), so we want to be prepared from the start.

The questions are:

1. What power source (AC, DC, solar) works best?

2. What are the maintenance requirements?

3. Are two desalinators really necessary for redundancy, or is it enough to have one with a good supply of spare parts?

4. What brand is best from the standpoint of operation, efficiency, production, weight, size, maintenance, etc.?

So far we have done just a little research - enough to discover a wide range of choices out there. For example...

- Village Marine Tec. has an impressive award-winning history, including working with the U.S. Navy. They also claim to "create the quietest pleasure and commercial watermakers on the market." VMT offers what they call their "Sea Quencher" models, "designed by boaters for boaters." The model SQ 200 uses either 12/24 DC or 110/220 AC power and produces 192 gallons (720 liters) per day. Is there an advantage to having the switchable option between AC and DC? (Village Marine's website)

- Blue Spring Corporation offers a very interesting solar-powered desalinator, Model EC-450S. It produces 120 gallons (450 liters) of fresh water in 8 hours of sunlight, and works on solar power only, battery power only, or solar/battery power simultaneously. This could also be a possibility in combination with our planned solar panels. (Blue Spring's website)

- The Spectra Newport 400 MKII touts its energy efficiency (supposedly one-third of the energy required by other systems), two-speed operation, unique backwash system and worldwide support. (Spectra's website)

We readily admit that we have no experience with any kind of desalinating systems on a ship, and we are hoping that others will share with us their experiences (especially with the brands and models mentioned above) and their suggestions.

We invite your input. Please email us.

Hydrogen/waterpowered engines

Our ultimate dream is to have the engines on the Cachalote powered by water instead of petroleum-based fuel or even biodiesel. This would mean converting the engines to use hydrogen-on-demand technology, fracturing desalinated water into hydrogen and oxygen.

Obviously, this technology is still in the developmental stages, although there have been certain breakthroughs already, such as Brown's gas and the controversial work of Stanley Meyer. According to the Wikipedia, Stanley Meyer "claimed that an automobile [engine] retrofitted with the device could use water as fuel instead of gasoline. The fuel cell purportedly split water into its component elements, hydrogen and oxygen. The hydrogen was then burned to generate energy, a process that reconstituted the water molecules. According to Meyer, the device required less energy to perform electrolysis than the minimum energy requirement predicted or measured by conventional science."

Part of our dream is that research into this area would be conducted at our landbase, for the non-commercial purpose of running our ship.

If you have good, solid technological input into water-powered engines, please contact us. (No conspiracy theorists, please!)

Redundancy

Basically, we want two of everything, for safety, and to continue to operate "normally" if one fails. We have two hulls, two masts, two sails, two engines, two fuel tanks, two water tanks, two sewage tanks, two independent wheels, and a backup navigation system.

The fuel tanks, water tanks, and sewage tanks would all be connected so that if one fails, the contents could be used or transfered from the other.

We also want two desalinators (maybe?), two solar panels, two wind generators, and two macerators.

Comments?