Please select your home edition
Edition
Barton Marine 2019 728x90

Square peg, round hole. Round peg, square hole.

by John Curnow, Global Editor, Powerboat.World 23 Sep 00:00 PDT
The 86 footer, AmnesiaIV - from Vancouver to San Diego in 7.5 days, averaging 9.6 knots over the ground, all at 3l/nm, including generator time!!! Now that's efficiency... © Pat Bray

If you think about fluid dynamics for just a second, one thing is pretty clear. Smooth and flowing wins the day. Be it aerodynamics, and how the little probe goes out in front of the car to show the way the smoke moves around the car in the wind tunnel, or hydrodynamics where charts plot the waves heights, and tank testing shows the results in real time.

It could even be more low tech, like the late and great Kiwi yacht designer, Jim Young, who used to tow freshly caught fish along in the shallows. His aim was to study the results over their bodies, and more importantly their appendages, like fins and tails, for they resembled keels and rudders.

Now when I got a note that said we have empirical proof that our hard-chined hull did better than a round bilge in a full suite of tests, well the first thing that came to my mind was the very heading above. Next I had to evaluate in my mind the thought that a brick with a nose cone had done better in a tank than a whale, whose only straight edges exist on whatever form of teeth it has, and then the leading edges of fins and tails (and there's that appendage word again...)

Here's the excerpt from the CFD report 2017 - Mavi Innovations Inc., Vancouver, B.C., Canada. "The CFD results showed a marginal increase in resistance for the round bilge hull, along with a change in trim angle. This was not the anticipated result, as round hulls typically outperform hard chine hulls."

"The important conclusion to draw from this analysis is that the chines on the vessel are shown to be well designed. The added cost of fabricating this hull form with round bilges is therefore not warranted, as it would not lead to substantial reductions in fuel consumption."

As it says, add in that a hard-chined vessel with its square corners is both easier and cheaper to build to the better fuel economy and range from the tests, and you had to wonder about why was this coming about now. How could this be? It literally flies in the face of the norm. When additional stability is also on offer, as well as easier placement of machinery and tankage, it not just piqued one's curiosity it demanded close attention.

This all came about after an earlier editorial on bulbous bows, called It ain't necessarily so. Once again, Canadian Naval Architect Pat Bray has offered some illumination over the matter, and proffered this analogous situation as a way to begin to contemplate it all.

"Take the progression of the internal combustion engine, from the first inefficient version to its modern-day efficiency. One of the first engines (1890) was a 1.1 litre motor capable of 4hp @ 900 rpm (Daimler/Maybach). Today that same size production motor with today's efficient carburettors, turbochargers, header exhaust, fuel injection, and careful intake and exhaust porting can develop up to 100 bhp @ 6000 rpm, whilst still being lighter and more fuel efficient than the original model."

Still not a believer, then just look at the production Toyota Yaris GR which will make 268hp (200kW) from just 1.6 litres!

Stay with us now

Bray added, "The basic principles of combustion and even the general design of these motors have not changed greatly from the initial concept, but fine-tuning the design has brought huge gains. Much of this has been brought about by bolting on better carburettors, tuned air intake and exhaust systems, etc. In that same spirit, the principles of a good, basic hull design were evaluated and then means reviewed, so as to increase efficiency by utilising enhanced 'bolt-on' appendages."

This all means it is a case of refinement, refinement, and refinement, rather than the light bulb paradigm moment. We also have to thank the Canadian Government at this point, for in the 80s they funded all the modelling and testing that delivered these results, as they aimed to achieve better outcomes for their vast fishing fleet in the face of rampaging fuel costs. It was all open source material, and the era of the slippery hull form and bulbous bow had dawned.

All of the work was done in Vancouver, at speeds of up to 24 knots in a smaller type tank, for the larger ones get under the auspices of the military PDQ. Now when the facility at Vancouver was closed, the Dean of Naval Architecture at the University of British Columbia just happened to be Turkish, and knew of a facility in Turkey that was small enough to handle the project, and offered faster speeds.

Bray's Bulb#2, as it was known, was created in 2012 and tested across the same, efficient 45m displacement hull to provide continuity. Assoc. Prof. Emin Korkut, Superintendent of Ata Nutku Ship Model Testing Laboratory, Technical University Faculty of Naval Architecture and Ocean Engineering, Istanbul, Turkey, stated, "Model testing and CFD - OS 45m (Enigma). - I should tell you that your form has been one of the best forms we have tested recently in our towing tank."

Thereafter, the research moved back to Canada and crossed over to Computational Fluid Dynamics (CFD) as the march of computational power meant more reliability and faster turnarounds. Again, the support of the Canadian Government through the National Research Council of Canada, and the Industrial Research Assistance Program (NRC IRAP), showed that appendages were the answer.

Here's the deal

The mid-ship bulb had been under consideration since 2006, and they had done a run at one speed only, and found it offered a 6% reduction in power. There was no more budget to pursue this at the time, nor take on the stern bulb the Japanese had discovered much earlier, but for which there had not been much appetite given fuel was comparatively cheap at the time.

Bray added, "This is how I met Gabor Karafiath. He researched stern bulbs, as he'd worked at Cardrock Annapolis Naval Facility. He now works for DARPA - the Defense Advanced Research Projects Agency. The thing is that you start with a good basic hull, place all three bulbs on one vessel - and it works - it's actually cumulative. Being 40% more fuel efficient is on the cards because you require a smaller engine and carry less fuel to feed it, all for the same speed and often more range."

"Interestingly, at 12 knots there is a 25% improvement, where as at 16 knots it down to 16%, but by the time we are back up at 20 knots it is 20%. The bow is creating a wave, with the pressure overlapping or out of sync, and thereby flattening the whole wave train."

Additional benefits are a reduction in pitch by 30%; the bow can work well in new ice for Explorer class vessels; you have a quieter acoustic pattern for all on board and undersea; and the smaller engines need smaller tanks, create less noise and pollutions, and deliver more room for the all important accommodations.

Bray also added, "When looking at the vessel afloat, the chine is almost entirely below the waterline, unseen to enquiring eyes. Use the glitz and the glamorous styling for the topsides, and go with the efficient, cost-effective form of the chined hull below the water, thereby enjoying its many benefits."

So the extensive research and testing have proven that as long as the chines follow the flow of the water (flow lines), then there is no powering penalty over the traditional round bilge shape. "The amount of stern immersion is far more critical in determining performance, so that must be kept in mind when designing the hull", said Bray in conclusion.

It gets even cooler from here, for soon all the material from the extensive, years long research will get revealed. Stay tuned... it's going to be good!

Congratulations!

You've made it this far... So as a reward, this videos will help you see for real some of the elements we have just been banging on about. the rest we'll all have to wait for. Enjoy -

High speed in flat water to taking a pounding

The rise of the Day Boat

Jeanneau's new DB/43 looks pretty good, and is certainly part of the burgeoning category, of simpler, easier to run boating that is appealing to many who don't see how a Convertible/Sportsfisherman/Flybridge craft applies to them and their lifestyle. Outboard Express and Inboard Efficiency are on offer to go with her modern and clean lines.

Not entirely sure when a dealer can take an order from you, and there is not any more information than that already released, so it looks like we're all on the hook together for now...

Off we go!

The Amels/Damen Yachting SeaXplorer 105 with its twin helo hanger certainly was one to ponder over extensively. Recently, the new SeaXplorer 60 was announced and continued the theme with hybrid propulsion, a matching limousine tender, along with that clever for'ard observation lounge. She's under way now, with a target delivery in 2024. That leaves plenty of time to work out which souls will be on your 100-person guest list for the Christening Party that you'll stage on her helo deck.

OK. Today you will find that the site 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 site you want to see and, voila, it's all there for you.

Finally. Please look after yourselves.

John Curnow
Global Editor, Powerboat.World

Related Articles

A Q&A with Mark Wheeler on the 2021 J/111 Worlds
An interview with Mark Wheeler on the 2021 J/111 Worlds Sail-World checked in with Mark Wheeler, regatta chairman of the 2021 J/111 Worlds, via email, to learn more about this One Design championship. Posted on 14 Oct
Spain SailGP debriefing, U.S. Youth Championship
Latest newsletter from Sail-World's David Schmidt in the USA While early October is always a great time for racing in North America, last week's sailing news cycle was dominated by the Spain SailGP event, which unfurled off Cadiz, Spain, on the country's southwest coast. Posted on 12 Oct
Jumbos rule
B&G gave us Nemesis, and this was a pretty cool piece of kit indeed. Not all the world's jumbos got retired and parked in the Arizona desert at the beginning of 2020. Boeing's venerable bus had served us all - so, so well… Later on that same year, B&G, gave us Nemesis, and this was a pretty cool piece of kit indeed. Posted on 10 Oct
Nancy Pearson and Buttons Padin on the Viper640 NA
David Schmidt checks in with the event co-chair and class administrator Sail-World checked in with Nancy Pearson and Ed “Buttons” Padin, event co-chair of the 2021 Viper 640 North American Championship and Viper 640 Class Administrator (respectively), via email, to learn more about this One Design regatta. Posted on 5 Oct
What's happening in America's Cup land?
Like it or not, it is the pinnacle event in yachting A lot is written about the America's Cup, and a huge amount of it is speculation. Like it or not, it is the pinnacle event in yachting, and for those who try to win it, it becomes an all-consuming obsession. Posted on 4 Oct
Hinman Trophy, offshore sailing, and Mini Transat
Summer may have handed the baton off to autumn, but the sailing scene hasn't been cooling off Summer may have handed the baton off to autumn, but that certainly doesn't mean that the sailing scene has been cooling off in North America, at least not yet. This past weekend gave the sailing world multiple great events to follow and participate in. Posted on 28 Sep
Hooray for the hundredth!
Here is our card to the J/99, which will soon enough have 100 vessels sailing all around the world. Now if you're a British subject that means you get a letter from HRH QEII. If you're French, maybe you get one from President Macron. Certainly POTUS does to US citizens. Posted on 26 Sep
James Keen on the Screwpile Lighthouse Challenge
An interview with James Keen on the 2021 Screwpile Lighthouse Challenge I checked in with James Keen, chairman of the 2021 Screwpile Lighthouse Challenge, via email, to learn more about this exciting regatta. Posted on 23 Sep
Mixing it up
A few sailing events which are a bit 'out of the norm' As we head towards the end of September, I've been thinking about which events, and days out sailing, have been the most fun this year. There are a few to choose from, and overall it's been a good year for time on the water. Posted on 21 Sep
Michael Weber and Jeff Braddon on the Jackrabbit
An interview with Michael Weber and Jeff Braddon on the 2021 Jackrabbit J/22 regatta I checked in with Michael Weber and Jeff Braddon, who serve as advisor emeritus and chair (respectively) of the 2021 Jackrabbit J/22 regatta, via email, to learn more about this freshwater One Design regatta. Posted on 15 Sep
Lloyd Stevenson Catalyst 45 728x90px3 BOTTOMC-Tech 2021 (Spars-QFX Racer) 728x90 BOTTOMSOUTHERN-SPARS-AGLAIA-SPARS_728X90 Bottom