Original technical solutions applied on special ships can often be found later on on private yachts.
In the article Propeller Progress: Modern Yacht Propulsion Systems, I looked at the transmission of Thunder Child II, a fast ship from Safehaven Marine, as an example of shafts with partially submerged propellers. Even then, there was a desire to devote a separate publication to this original project, and the informational reason for it was the successful sea trials carried out at the beginning of the year.
For the first time, we wrote about this shipyard, located in the south-west of Ireland, near the university city of Cork, in the article “Barracuda Goes Through”. It manufactures vessels of various types, including pilot boats and special-purpose high-speed boats, the main difference being their high seaworthiness. Barracuda (project SV11) – a 10-ton patrol boat with a composite hull and a superstructure based on stealth technology – produced under two Caterpillar C9 engines of 575 hp each. from. speed 33 knots in such conditions when more powerful and faster “normal” boats did not dare to go to sea at all.
Another pioneering development of Safehaven Marine is the XSV20 (Thunder Child II) project, which is entrusted with the mission of a record crossing of the Atlantic.
Externally, the boat is distinguished by an extended foredeck, a wheelhouse shifted to the stern and a relatively small cockpit. The dominant feature of the wheelhouse is the control room almost from side to side, equipped with four Simrad 19 ″ MFDs. In front of him are two Military 4600 seats (for the pilot and navigator), four more – from the new X8 series of the same Canadian company Shoxs; all have a shock-absorbing suspension with a travel of more than 20 cm. In the bow of the hull there is a small saloon, cabins, a galley and two latrines – the atmosphere is Spartan, but the purpose of the boat is appropriate.
Armchairs with shock absorption, handrails throughout the wheelhouse, a waterproof cockpit door, durable glazing … The entire interior is subject to the criterion of functionality
To the right of the helm station, a passage to the cabins and a small saloon is visible, which transforms into a cabin
The most interesting thing about this boat is the hull. The composite structure is molded using aluminum borosilicate glass (E-glass), carbon, Kevlar (to reinforce high-load areas) and a binder – Scott Bader vinyl ester resin, which made it possible to obtain a durable structure designed for overloads up to 6 g.
Construction of the ship was preceded by six months of research. During this time, Safehaven Marine tested 12 scale model options in a pilot basin to optimize performance. As a result, Thunder Child II received an innovative hull shape (patent pending) with a steep reverse slope of the stem (wave piercing), deep V contours with extremely sharp waterlines in the bow and a smooth transition into asymmetric catamaran hulls. Other distinctive features were the cheekbones and longitudinal steps of complex curved shape, as well as two transverse steps. This “hybrid” design is designed to provide the required lateral dynamic stability in conditions of developed sea roughness, as well as to reduce roll during roll, the slamming effect when the boat is moving at high speed, and the shock load on the “bridge” between the hulls, which is typical for catamarans of conventional design.
29 800 kg
4 × Cat C8.7 (650 hp)
An important part is the hydrofoil system (developed by Hyuscraft) between the hulls in the catamaran area. When a certain speed is reached, the wings raise the body up to half a meter, reducing the wetted surface area and splashing. The bow sections are washed out only when high waves pass, when the stem cuts through them, gently extinguishing the wave energy (the effect begins to manifest itself at a wave height of 2 m). Such a design, as reported by its creators, is less sensitive to load compared to conventional planing hulls and allows for more significant fluctuations in mass, and the buoyancy of the bow allows avoiding an excessive decrease in clearance when the vessel is heavily loaded or forced to reduce the speed.
Like some other Safehaven Marine models, the Thunder Child II has the ability to self-heal after a rollover, which is verified by a special test. And unsinkability, as indicated in the specification, is provided by eight watertight compartments. Taking into account the likelihood of the ship hitting a storm and the expected loads from waves, Houdini windshields (ballistic glass) with a thickness of up to 25 mm were chosen; the rest of the windows are made of unbreakable polycarbonate (12 mm).
Engines and systems
Thunder Child II has four Caterpillar C8.7s with 650 hp each. with., drives – shafts with semi-submerged screws (France Helices, SDS3L). There are project options with two more powerful engines with the same transmission and even with water cannons (Marine Jet Power / Hamilton), but the four-engine installation should provide higher speed and reliability for such a serious journey as the planned crossing of the ocean, since even if one from the engines, the boat will be able to continue planing. Also, thanks to the lighter transmission model (270 kg), some weight savings are achieved.
Pivoting drives allow you to steer your boat and raise or lower propellers to trim and change propeller depth. In addition, on a large wave, when the engine speed has to be reduced and the speed drops, it is possible to use only two engines by raising the internal drives. There are also four automatic Humphree HE-series spoilers for steering trim and roll stabilization. Another “tool” for changing the trim (position of the center of gravity along the length) is a reserve bow fuel tank with the ability to pump 2000 liters of fuel there.
Semi-submersible propellers are effective at a certain depth, so the propeller shafts on one side are parallel to the bottom plane to match the wake profile behind the stern
Thanks to the lower gear ratio of the two-speed ZF 325ATS gearboxes, it is possible to significantly relieve the propellers when they are hydrodynamically “heavy” during excessive submersion (for example, at low speed). For this, air is supplied to the screws through the pipes (ventilation mode).
Dometic air conditioning systems (2 × 27,000 BTU) provide crew comfort on board.
The goal is a record
Frank Kowalski, founder of Safehaven Marine and author of shipyard projects, including Thunder Child II, is a seasoned sailor. In 2017, together with the team, he set the UIM (Union Internationale Motonautique) record in the race around Ireland and Rockall, the legendary rock in the Atlantic Ocean (the surface of the destroyed cone of an extinct volcano). The new task before him is much more difficult.
The purpose for which Safehaven Marine built this boat is the UIM-approved world record for crossing the Atlantic from Canada to Ireland. The complexity of the 2,400-mile route through Greenland and Iceland is due to the navigational situation: possible ice fields and icebergs, as well as cyclones typical of the high latitudes of the east coast of Canada, which will have to be skirted. But from mid-July to late August, a weather window opens here, after which the hurricane season usually sets in.
Seaworthiness is the main criterion when creating such boats
That is why the Atlantic crossing was scheduled for July. At first it was July 2019, but the completion of Thunder Child II and the preparation of the ship for such an expedition was prevented by the loading of the shipyard with other orders, which were given priority. There was also a benefit in this delay: there was time for additional trials of Thunder Child II, in particular those that took place in February. Last year, the boat was tested for two months off the Atlantic coast of Ireland, where it demonstrated excellent seaworthiness in difficult conditions – up to a wave height of 5 m.This year the test conditions were even tougher: with winds up to 40 knots, the wave height reached 6 m. Even in such a storm, Thunder Child II performed well. Of course, the skipper needs to be able to accurately estimate the time of approach of the wave so that the crest collapses before it overtakes the boat, but the experience of the Safehaven Marine team is not lacking. According to our colleagues from the British MBY, such a test is pure adrenaline, but this is the point of such tests: before the boat is delivered to the customer, it must prove its seaworthiness.
There is no official data on the actually measured speed, but the calculated one with four Caterpillar C8.7s of 650 liters. from. is 54 knots. A fuel reserve of 8000 liters gives an estimated cruising range of up to 800 miles at a cruising speed of 30-40 knots (and more than 1000 miles at 12 knots). Here the choice of the route becomes clear. For all its complexity, it is the only real one, with the longest section of the open ocean between refueling points about 760 miles (refueling in the middle of the ocean is not allowed by UIM rules). So, according to the calculations, everything should work out. And we have a chance to watch what is happening. Deck-mounted GoPro cameras will be filming from onboard, while electronic equipment from Dell and Navarino provides satellite communications and allows real-time tracking of boat movement during the Atlantic crossing on a special page of the 8West Consulting website.
Lifeguard or yacht?
Safehaven Marine is promoting its ships on the market by emphasizing their increased seaworthiness: the number of views of the video where Thunder Child II storms among the shafts reaches half a million, and this has nothing to do with the usual yachting for vacation.
Frank Kowalski, founder of Safehaven Marine
The capabilities of our vessels go beyond the typical operating model of pleasure yachts. Although conventional yachts have to withstand severe weather conditions, their constant operation in extreme conditions is not expected: there is a different set of priorities.
Of course, Thunder Child II is a special vessel, designed to perform the functions of patrolling waters and intercepting intruders, participating in search and rescue operations, etc. However, it is known that many innovative ideas, initially applied on special vessels, were subsequently used on pleasure craft. Therefore, it is possible that over time we will see how some technical solutions will migrate to high-speed private yachts. Or maybe someone decides to buy this (or such) Thunder Child II as a pleasure boat …
This is exactly what the customer of the XSV20 modification with an open helm station at the top did, which received his boat in Porto Cervo last fall. There, to Sardinia, she came under her own power from Cork, having covered 2,500 miles. Well, a yacht is a vessel for recreation, and everyone prefers to relax in his own way.