Please select your home edition
Edition
Maritimo 2021Oct - S60 LEADERBOARD

It ain't necessarily so - powerboat.world newsletter

09/06/2021


It ain't necessarily so

McConaghy Boats 2021 - LEADERBOARD

Sea Sure 2020 - SHOCK-WBV - LEADERBOARD

Bulbous bow on the starboard hull of the Aquila 44 powercat - photo © John Curnow


Dear Recipient Name

Please find below the latest e-news from powerboat.world

powerboat.world is a unique website that covers the latest news of new power boats over 10m and their associated accessories. News is posted within hours of being received and provides essential information for any marine company that has any connection with the 10m+ powerboat industry segment.

Not only do we welcome your feedback, but invite you to supply us with details of your products or services for potential inclusion on the site and in future postings of the e-newsletter. The editor's email address is editor@powerboat.world

If you would like to receive future issues, we will retain your details on our mailing list, otherwise you can unsubscribe accordingly.

Was a time when you either had to be really big, or just plain slow to have one. Perhaps even with one foot planted firmly in both camps. It was also quite amazing just how long it took the US Navy to deliver the Ford Class carriers, when they are really a Nimitz Class with a bulbous bow added on. What is with that?

Now in what seems like a trillion years ago, I had my first experience with bulbous bows on a more approachably-sized craft, and it could march into the low to mid 20s. Hardly the norm, or so I thought at the time, but alas it just meant the era of the Fast Displacement hull form had arrived. That vessel was the Aquila 44, which I drove in 2016 and reported on in Lots to Love.

Horizon FD75 - photo © Horizon Yachts
Horizon FD75 - photo © Horizon Yachts

Right. Seems I am not alone in considering all of this, either. Avid reader and friend of Powerboat.World, Pat Bray in British Columbia, has also been deliberating it all. Only difference is, he's a Naval Architect, and he's been kind enough to provide us with some very brilliant intel on it all, and thank you very much, Pat, who you can find at Bray Yacht Design And Research Ltd. So take it away, Pat...

Aquaventures 2021 - Sea Angel MOB - MPU Savvy Navvy 2021 PBW MPU v2

The Maths Lab

And that's math, not meth. We're cooking data here, not drugs. Taking their cue from fish boats and ocean freighters, long-range cruisers are capturing the advantages of the bulb, and there are many. Sceptics may question these claims, but solid proof is in the 'numbers'; the data not only from model test results, but from retrofitting bulbs to numerous types and sizes of yachts, with definite and measurable advantages.

Amnesia III with retrofit bulb - photo © Bray Yacht Design And Research Ltd
Amnesia III with retrofit bulb - photo © Bray Yacht Design And Research Ltd

Let me introduce you to some real-life success stories. The owner of a Symbol 72 found himself challenged by an overweight vessel with an excessive bow wave. Unable to achieve the designed speed and performance, a bulbous bow was recommended. Upon retrofitting a custom bulb designed specifically for the hull shape of his yacht, he experienced a much-reduced bow wave, leading to increased speed and fuel efficiency: 3.5 knots increase in speed, in fact. This owner then went on to commission a new state of the art yacht with an optimized hull form incorporating a fuel-efficient bulb.

The delivery trip on Amnesia IV from Vancouver, B.C. to San Diego, CA took 7 half days with an average speed of 9.6 knots over the ground. With generator run time included we averaged 3 litres per mile (6.25 US gal/hr). Even in 40+ knot winds and really big seas the boat handled very well.

Amnesia IV with bulb - photo © Bray Yacht Design And Research Ltd
Amnesia IV with bulb - photo © Bray Yacht Design And Research Ltd

Sea Sure 2020 - SHOCK-WBV - MPU Highfield Boats - PBW - MPU

Just what is a bulbous bow?

In the late 1930s research was undertaken to reduce the drag on large ships. With model testing and advancing knowledge of hydrodynamics, the commercial bulbous bow was formulated, typically giving a 5% reduction in fuel consumption over a narrow range of speed and draft. This was significant for a large ship crossing vast oceans at a time when the cost of fuel was rising, and in the 1950s bulbs were commonly used on commercial vessels.

At that time, this was not sufficiently worthwhile for smaller, non-displacement yachts, cruising local waters. However, once the market for long-range cruisers opened up in the late 1990s, innovative yacht designers began to look for ways to reduce fuel consumption. The bulbous bow stood out as a potential solution. Since then, technology has allowed for refinement of the bow bulb to give even more advantages.

Larger wave and higher running attitude without bulb - photo © Bray Yacht Design And Research Ltd
Larger wave and higher running attitude without bulb - photo © Bray Yacht Design And Research Ltd

In these model test photos, you can see the effect that the bulb has on the bow wave. The bow wave is pushed forward and flattened over the bulb, followed by a longer, lower wave, and also a reduction in the midship hollow. Overall, the wave pattern is flatter, meaning less resistance for the hull to move through the water.

Lower wave pattern and less midship hollow with bulb - photo © Bray Yacht Design And Research Ltd
Lower wave pattern and less midship hollow with bulb - photo © Bray Yacht Design And Research Ltd

Maritimo 2019 MPU Marine Auctions 2019 600x500

How does it work then?

Although much is known about the bulb, many of its functions are still in dispute. On a hydrodynamic level, the destructive interference of the primary and secondary wave trains causes an overall reduction in drag that is beneficial to the vessel's resistance characteristics. Or, on a more physical level, that the water coursing over the top of the bulb is exerting a downward pressure that is keeping the stern from squatting, thereby allowing flatter trim, causing the vessel to run with less resistance. In any case, it is a fact that bulbs do work, and do their best work above hull speed and achieve a resistance reduction of up to 23%.

MODEL TEST RUN, WITH BULB, FULL LOAD CONDITION - photo © Bray Yacht Design And Research Ltd
Model test run with bulb, full load conditions - photo © Bray Yacht Design And Research Ltd

Bulb proportions are critical, and derived from the features and dimensions of the vessel itself. The bulb must be designed for the specific hull it is to be fitted to. The vessel will pitch less, which will cause less disturbance in the water, and the passage of the vessel through the water will be achieved with less fuss and muss. Any time a vessel can be moved through the water with less waves and overall disturbance to the surface, less power has been transmitted to the water to create those waves, thereby reducing resistance.

McConaghy Boats 2021 - MPU Coast Guard Foundation MPU 1

How much does size matter?

Here on the West Coast where the fishing fleets run great distances over open ocean from California to Alaska, the desire for economy spurred on the optimisation of the bulbous bow.

In the late 1980s the University of British Columbia, utilising the B.C. Research Ocean Engineering Center, initiated model test work on 60-foot fishing seiners. Results then showed that running at continuous displacement and semi-displacement speeds for days at a time, coupled with the limited change of draft, then also made long-range motor yachts ideal for this application.

Kari 47' Trawler with bulb - the bulbous bow and fin design are giving us the smoothest ride ever - photo © Bray Yacht Design And Research Ltd
Kari 47' Trawler with bulb - the bulbous bow and fin design are giving us the smoothest ride ever - photo © Bray Yacht Design And Research Ltd

Even more current research demonstrates the results are significant in vessels over 40 feet, and real gains are being achieved above the 60-foot bracket. This difference may be due to the stockier hull forms required in the really small ships, which possibly are not quite as compatible with the characteristics that make the bulb work so well in the longer vessels. However, a correctly proportioned bulb can still provide advantages even in the smaller vessels.

In the more that sixty retrofits that we have engineered and collected data on, all of them report a minimum 0.74 knot increase in speed, or 12% drop in fuel consumption, along with a 50% reduction in pitching motion.

Kari 47' Trawler with bulb - the bulbous bow and fin design are giving us the smoothest ride ever - photo © Bray Yacht Design And Research Ltd
Kari 47' Trawler with bulb - the bulbous bow and fin design are giving us the smoothest ride ever - photo © Bray Yacht Design And Research Ltd

Pros and cons...

The benefit of a high-tech bulbous bow is that it will reduce your fuel consumption 10% or more, giving you the equivalent greater range, or higher speed, whichever way you choose to apply it. The greatest amount of benefit will be at the higher end of the semi-displacement speed range, reducing as your speed decreases.

At higher speeds, wave-making resistance accounts for the greater portion of the drag, and the slower you go proportionally more of the resistance is taken up by wetted surface drag. At low speed (around 6 knots and lower) the bulb may cause a slight increase in drag because of its greater wetted surface area, however at that low speed the added power consumption is negligible.

Generally little time is spent in this low-speed range, so the effect is not noticeable. In addition, you will find increased sea-keeping ability due to the 50% dampening of the pitching motion. One boat we tested could go two knots faster with the same degree of comfort in waves as it did at the slower speed without the bulb, and this seems to be the average result.

When charging into head seas there is a small chance of slamming the bulb on the troughs, but this is limited to a very narrow range of wave train and headings. A slight change in direction and/or speed will cure this ill effect. The increased comfort level (from pitch reduction) is the biggest bonus noticed (and appreciated) by owners of all the retrofitted yachts.

When anchoring off the bow ensure that the anchoring arrangement clears the bulb or as an alternative you could consider installing an anchoring bowsprit to ensure the anchor falls well away, especially in conditions where swinging occurs; or use anchor pockets port and starboard.

Overall, the pros far outweigh the cons, so enjoy.

Horizon 65 receives a bulbous bow - photo © Bray Yacht Design And Research Ltd
Horizon 65 receives a bulbous bow - photo © Bray Yacht Design And Research Ltd

At 1650 RPM the vessel previously did 11.5 knots; after the refit she does 16.8 knots. The trim angle at the old speed was 5 degrees and is now 2.8 degrees. Nautical miles per gallon went from 0.15 to 0.28, an increase of an almost unbelievable 186%. The fuel burn was reduced from 76.5 gallons/hour to 60; and all this at 16.8 knots. The bow spray is significantly lowered and the motion in a seaway is just as dramatically improved, with a major reduction in pitching motion.

So who can, and who can't?

Any vessel over 40 feet, regardless of size, material, or age can be retrofitted with a bulb. An often-asked question is; will the cost exceed the benefit? Generally the benefit outweighs the cost, especially if the boat is to be used for extensive cruising, it will provide a clear advantage.

Bulbs have been built out of steel, aluminium, fibreglass, and wood. For an existing boat they are attached externally to the bow, in effect creating a bumper, which if damaged does not breach the watertight integrity of the hull.

Once properly designed, any reputable shipyard can create and install a bulb in a short period of time with the vessel out of the water. Factors that can complicate the installation are bow thrusters that occur within the outline of the bulb, and transducers and thru-hulls that have to be moved or extended to reach the new line of the vessel skin, so be sure those are taken into account.

Horizon 130 receives a bulbous bow - photo © Bray Yacht Design And Research Ltd
Horizon 130 receives a bulbous bow - photo © Bray Yacht Design And Research Ltd

The bulbous bow above is performing perfectly. It has dramatically reduced "hobby-horsing" and we are now only burning 22.5 gph at 8.3 knots which has increased our cruising range from around 3600 NM to 4000 NM.

In new construction, the benefits of the bulb can be designed in from the start. It will be an integral part of the hull, with a watertight bulkhead separating it from the interior spaces. Successful new builds have proven the effectiveness and efficiency of this technology.

The real deal about bulbous bows

  • They are even more effective in reducing resistance once you get above hull speed. People think of bulbs only for displacement hulls where in fact a bulb starts to work most effectively once you approach hull speed, and reach their maximum benefit above that.
  • Reduce your trim angle by as much as 1 degree, improving visibility.
  • Reduce your pitching motion significantly, increasing comfort and improving seakeeping.

Computational Fluid Dynamics Model test image at 14 knots - photo © Bray Yacht Design And Research Ltd
Computational Fluid Dynamics Model test image at 14 knots - photo © Bray Yacht Design And Research Ltd

  • Lower the height of your bow wave, reducing water on deck and environmental wave train impact.
  • Increase your range under power from 12 - 15%.
  • Reduce your fuel consumption up to 23% depending on the vessel speed.
  • In a new build vessel you can fit an engine with 20% less horsepower, have fuel tanks 12-15% smaller, and still reach your contract/designed speed and range.
  • In a new build it will reduce your Gross Tonnage by reducing hull volume because the smaller fuel tank requirement makes for a lighter boat.
  • Work very effectively as a light icebreaker bow in new ice.

Takeaways

  • If your craft is over 40 feet in length, and does not go faster than 24 knots, then a bulb could be for you.
  • If you plan on doing some long passages, then a bulb could be for you.
  • If you want a more comfortable motion through the sea, then a bulb could be for you.

What is your next step?

Contact a Naval Architect who is knowledgeable about bulb technology. Be prepared to give them serious technical data on your vessel, or if you don't have that data, understand you will have the cost to re-establish that information. If you are willing to go with a bulb of relatively standard proportions and form, no model testing should be necessary.

Complete package in this upgrade - bowsprit and bulbous bow - photo © Bray Yacht Design And Research Ltd
Complete package in this upgrade - bowsprit and bulbous bow - photo © Bray Yacht Design And Research Ltd

If you are starting design and construction of a new vessel and want it to have a bulb, check with your Naval Architect. If they do not specialise in bulbs, consider having a specialist design the bulb to work correctly with your hull's shape and size. This will ensure the best possible benefits.

Ultimately, just add large amounts of ocean water and minimal amounts of power for many happy, and less expensive years of cruising lie before you. Bon voyage!

Thanks Pat!

Short takes

Reading that Lionheart Capital and John H. Ruiz bought Cigarette was enough to sit up and pay attention. Their current craft range is priced from USD 600K to 3.5M, but I got to pondering the future some more, and wondered if question was whether it is not all so James Bond and no longer has a home in the PC world?

Cigarette Racing Team 59' Tirranna Powerboat - photo © Cigarette Racing
Cigarette Racing Team 59' Tirranna Powerboat - photo © Cigarette Racing

I mean turbine powered cats obliterated them for speed. The more user-friendly outboard powered centre consoles pretty much took care of the remains. True, they have gone that very route themselves, but being skinny and not having the lumpy, straight through exhaust V8s just isn't the same thing, now is it?

Ultimately I remain interested to see what new money can do with the brand most synonymous with the era, and maybe they can share it all with Barbara Broccoli when they work it out. A good one to watch, me thinks...

Maritimo S600

The new M600/S600 pair are identical from the aft deck BBQ/seating console all the way for'ard to the stem of the brilliant M55/S55, including the engine room (just longer prop shafts). The big difference is the longer running surface out aft, which is really best described by seeing the transom rise up from the trailing edge of the optional extended adventure deck you see here on our test boat. That's huge!

It also allows for an even shallower shaft angle than the M55/S55's brilliant 9.1 degrees, and it is all done without the need for tunnels. Then there's the added buoyancy it provides for, the fighting chair and fish wells you can opt to have installed, along with a full wedge transom to back down hard on the big ones so they just can't get away, and lastly the option to go up to a pair of Scania's V8 1200s - the kings of the power to weight title fight. In those you would have to think it would be over 35 knots WOT and genuine low 30 knot cruise.

Personally I can see the single level Maritimo S600 with a half tower (I reckon we need to look out for a super-sexy version BTW), and the V8s getting the nod from serious fishos on both sides of the Pacific. Given the walk around decks, you could almost argue that it is one giant sized enclosed centre console...

Maritimo S600 Offshore Sedan Motor Yacht - photo © Maritimo
Maritimo S600 Offshore Sedan Motor Yacht - photo © Maritimo

OK. Today you will find that the website has an abundance of material from right across the globe, and if you cannot find something, just try the search button right up the top of the landing page, above our logo.

So as you see, there are stories, lessons, inspirations and history to regale yourself with. Please do savour... We're really enjoying bringing you the best stories from all over the globe. If you want to add to that, then please make contact with us via email.

Remember too, if you want to see what is happening in the other parts of the group, go to the top of the Powerboat.World home page and the drag down menu on the right, select the area/discipline you want to see and, voila, it's all there for you.

Finally, please look after yourselves,

John Curnow
Global Editor, Powerboat.World



One Ocean Crew and savvy navvy prepare to row the Atlantic
If you're in need of some motivation look no further than the awesome ladies of One Ocean Crew.

Slowboat Flotilla to Alaska - Wrangell to Petersburg - Day 14
The shortest navigable route from Wrangell to Petersburg is through Wrangell Narrows, a narrow, winding, rock-laden 22 nautical mile passageway with swift current and lots of traffic.

Maritimo unveils S600 Offshore Sedan Motor Yacht
Leading Australian luxury motor yacht builder, Maritimo, has unveiled the latest exciting addition to the recently revealed Offshore Series of motor yachts, with the announcement of the S600 Offshore Sedan Motor Yacht.

World Oceans Day 2021 - How to have an environmentally friendly yacht charter
Superyachts travel to some of the most beautiful destinations in the world to experience the finest natural beauty, enjoy the best diving sites and bask in the sun on white sand beaches.

Numarine delivers the 14th unit of the successful 26XP explorer yacht in only three years
Numarine, the European high-performance motor-yacht shipyard headquartered in Istanbul, has delivered a new explorer yacht. This is the 14th unit of the 26XP Series.

XO Boats expands its product range by launching the new DFNDR 9
The Finnish boating company XO Boats Ltd. has launched the newest achievement of its ambitious product development. The new DFNDR 9 follows the known principles of XO boats

The all new Sunseeker 100 Yacht launching in autumn 2021
Sunseeker is delighted to reveal the latest details and imagery showcasing the elegant and striking lines of the all-new 100 Yacht.

Testimonial from the owner of M/Y Friedrich
It's always nice when your customers are happy with their purchase. Even more so when they want to tell others about it.

Ferretti Yachts 1000: a thousand reasons to fall in love
Launched in March and the product of a design process inspired by the search for perfection, the new flagship is a truly impressive project, made of talent and technology, the ability to innovate, and craftsmanship.

Sanlorenzo launches eighth 500Exp
In the setting of the Sanlorenzo shipyard in La Spezia, the eighth unit of the 500Exp line has hit the water. An elegant and advanced interpretation of the Explorer typology, of which the ninth unit has also been sold

50-metre Columbus Sport M/Y K2
Columbus Yachts, a brand of Palumbo Superyachts, presents the new 50-metre Sport M/Y K2. The success of the SPORT line by Columbus Yachts, established in 2011 with the award-winning 40-metre models, is confirmed.

Raymarine & Marinas.com partner to bring better points of interest to Raymarine's LightHouse Charts
Raymarine have announced that its LightHouse Charts Premium service includes points-of-interest data provided by Marinas.com - the single best source of marina and waterway information for boaters on the web.

Bad weather boating tips
Welcome to Boating Tips LIVE with MarineMax! Join hosts Captain Keith and Captain Nick Mondays at 3 pm ET as they exchange stories and share tips and tricks while answering viewer questions.

ValvTect® welcomes 17 new marinas to the Certified ValvTect Marina program
The locations listed below are now fully authorized ValvTect Marine Fuel Marinas and all have met strict quality control specifications for fuel quality and formulation performance in accordance with ValvTect's marine fuel guidelines.

Grand Banks 85 Update: Interior Layouts and Design Revealed
Craftsmanship, ingenious ergonomics and interior volume redefine long-distance cruising

First award-winning CLX96 Sea Activity Vessel prepares to launch
The first CLX96 Sea Activity Vessel, or SAV, from CL Yachts is entering the final stages of construction, with its launch set for July and first public appearance expected at Fort Lauderdale International Boat Show 2021.

Rosetti Superyachts launches its first pleasure yacht: the RSY 38m EXP
Monday 31st May 2021, the launch ceremony of the new RSY 38m EXP took place in the presence of the owners and their family, in full compliance with the COVID measures, which did not hinder the important operations of launching a new boat.

Sub-500GT Incat Crowther 48 ShadowCat
Following the recent successful delivery of the 68m Wayfinder, Incat Crowther and YCTS, Ltd. are pleased to announce the release of a new 48m sub-500GT catamaran shadow yacht concept, named ToyBox.

First Columbus Atlantique 43 sold - Architecture for Voyagers
Less than two months after the launch of this new line, Columbus Yachts, a brand of Palumbo Superyachts, announces the sale to a European Client of the first 43-meter Atlantique unit that will be delivered in 2023.

Riva 76' Perseo Super launched in La Spezia
There are many reasons to fall in love with the new Riva 76' Perseo, heir to and evolution of the multiple award-winning 76' Perseo, which exceeds every expectation in terms of design, aesthetics, functionality, on-board liveability and performance.

Gran Turismo 45 - A unique blend of high-level comfort and sporty dynamics
The Gran Turismo 45 sets new standards in terms of functionality and on board hospitality. With its large windows, vast sundeck and U-shaped cockpit seating, the GT 45 fosters conviviality and the enjoyment of a great indoor-outdoor experience.

Nauta 54m Wide - an original concept conceived for modern family lifestyles afloat
The Nauta 54m Wide is a new concept with pure lines and original layout solutions conceived for modern family lifestyles afloat.

Savvy Navvy 2021 PBW FOOTER v2

Maritimo 2021 - M600 - FOOTER

This email was sent to the.recipients@email.address by YY Online Services Ltd.
Towngate House, 2-8 Parkstone Road, Poole, BH15 2PW
Registered in England No. 7895890

Our records show that you signed up to receive news from us on 1 January 2000

Please do not reply to this message as this address cannot receive replies.

You can unsubscribe at any time or email us here if you encounter any difficulties
Marina Exchange FOOTER 1Sea Sure 2020 - SHOCK-WBV - FOOTERCoast Guard Foundation FOOTER 3