Why are we not using this?? Ian's bulbous Bow for rowing - it is faster and legal!

[@pankow2893]

Love the thinking...I do think that the pulsatility of the shell drive (as contrasted the steady drive of large ships) will create differing challenges to the optimization of the approach, but look forward to hearing more!

[@daniellyne9420]

I have built a couple of singles myself and it has occurred to me before that this could work!

[@chrischamberlaine4160]

Bulb bows on commercial vessels evolved for very practical reasons. They work efficiently at one speed and one displacement because they are designed to suppress the bow wave of a vessel in synch with its natural bow wave at that speed. At full load the vessel can cruise from China or the Gulf using about 1 to 2% less fuel which is the main objective. In ballast they do not work and any oceanic wave condition eliminates effectivness. A light displacment sculling boat has a very small bow wave at its operating speed so any bulb feature is probably adding a little waterline length at the cost of greater wetted area with the bulb itself is adding a bow wave and therefore resistance. A bulb will not work efficiently if the velocity varies as in a sculling boat for each stroke and they will be useless in a seaway where pitching will negate any benefit. This is a case of grabbing a bit of tech from another regime and creating a good sales storyline for those who don't understand hyrodynamics. We tried bulb bows and sterns in six metres sailing yachts in the '70's. Although different to oared boats the experiments failed for a variety of 'sailing related' reasons one of which was desperatly poor turning ability. I went to sea as a navigator in tankers at the age of 16 but followed that up with a career in engineering, yacht design and racing at top level but I have also designed a few production recreational sculling boats as well as a succesful coastal four for Southampton Rowing Club. I'm now 80 and scull most days offshore in my Mondego. I'm afraid to say that this is technical nonsense which simply adds to the cost of production - but selling boats always benefits from a good bit of mumbo jumbo - and if you 'believe' and the other guy has not got the new idea there is a psychological advantage. When sails went plastic and multicoloured - if a blue sail won a race everyone wanted one of those blue sails.

[@ianjosephrandall]

I guess it depends on how you measure the "light" displacement and the "small" bow wave. Both the displacement and the bow wave are significant elements of a rowing hulls performance. Specifically, the bow wave sticks and runs all the way down the hull until the next rowing stroke produces another wave that sticks and runs ... This has now been eliminated with this bulbous bow. It's working.

[@schoonerman421]

Actually the bulbous bow increases the prismatic coefficient of the hull, making the water eact to the displacemt of the hull through the water as if it were a longer hull, thus giving a larger hull speed. The breaking up of some of the bow wave is an incidental effect, although usefull, is not generating as much speed increse as the increase in hull entry finess ratio as sous the inxrease in prisnatic coefficient. For the rowing shell, there is a different predominant dynamic in effect. Fines ratio is the most important drag factor, NOT wetted surface. If that was the case, you would see shoerter perfectly rounded bottom shells that take max advantages of their displacemt for the amount of wetted surface, i.e. wtted surface is somewhat important, but seconday. Yacht design has proven this wuite thoroughlt. Sompare the old CCA desgns to modern designs, which carry far more wetted surface for a fiven displacement. The dogma of think stricktly wetted seurface reduction led to long overhangs, with shorter water lines. Yes, these types of old vessels , were incredibly effectly in light air zephyr condions, which advantage was far surpassed by a higher fineness tatio, for a geiven displacement. In the case of the rowing shell, it is more productive to think of it a the need to minimally open then close the water, as it displaces the water, than to consider wetted surface.

[@GlobetruthFU]

If sliding outriggers hadn't been banned all the boats would be smoother and faster.

[@simonh9290]

I believe there's a difference between a displacement vessel and a rowing shell in that the rowing boat is a needle shape with very different forces at play. One reason why a catamaran (needle shape) can reach higher speeds than a monohull sailing boat (displacement vessel) even with just one hull in the water (i.e. with comparable waterline)

[@dc14522]

Thanks for this... I just bought a sailing trimaran (windrider 17), and I'd love to try something like this to improve the performance.

[@ttmallard]

Very cool, perfect way to handle the cg's of sliding seats per stroke ! Cheers, good one 🍺

[@phillipsmith4979]

Reminds me of the Baidarka bow from Aleutian kayaks

[@georgedoolittle9015]

There are two ways to think of the bulbous *"water line ependage"* none of which have anything to do with hydrodynamic efficiency or *"improving the flow at the waterline."* The first is as an attempt to actually create friction at the bow in both weight and mass to keep the bow in the water thus keeping i think it be called a *"control surface"* or the entire bow *"in the water"* (fighting any wave action where it matters... at the bow.) The other possibility is by adding a massive *"bulb"* appendage again *"breaks up the waves"* basically by creating one as a freighter type massive ship these are made for are pushing *THROUGH* the water not on it like a racing skiff or #skull as it were. Also i thing these massive vessels that use this have a "plum bow" in order to maximize ever square inch of volume. Add a "bulb" to the lower front and that would be the "raked bow" part. There is a lot to be said for *"breaking up the water"* whilst pushing forward absolutely as water of any type is *CRAZY DENSE* on of the heaviest objects we know is a gallon of water actually. This might be a reason for the "inverted bow" or #tumblehome_hull for example on the US Destroyer DDG-1000 Class of vessels meaning the purpose is not to go over the wave but *"break"* through the wave instead creating in theory anyways a much more stable *"vessel in water "* would this hull type work in a racing skiff hard to tell until it was tested as such but yes they most definitely prefer a plum bow for skiff racing such as done here as a single human let alone 8 is a massive *"weight"* in the vessel creating displacement #displacement_theory

[@Johnninham-ur1dr]

'Some thing which I have thought about from time to time for many years and did not attend to for 1 reason or another.... a packing system under the slides, so the sculler and rower can readily have control of the seat and slide/deck height within the rig aggregate. If you can adjust this area conveniently it would improve the rigging for the athletes they pack them vicariously with plywood packers for years but if you work specifically with increments of 1,2,5 mm with a standard plastic infrastructure one could procure a simplified system.....

[@ChrisRRRRRRR]

This looks interesting. I would like to try it. Will it be available anytime soon?

[@ianjosephrandall]

Get in touch with Aram. The 3D file is available for testing and adapting.

[@schoonerman421]

Actually the bulbous bow increases the prismatic coefficient of the hull, making the water eact to the displacemt of the hull through the water as if it were a longer hull, thus giving a larger hull speed. The breaking up of some of the bow wave is an incidental effect, although usefull, is not generating as much speed increse as the increase in hull entry finess ratio as sous the inxrease in prisnatic coefficient. For the rowing shell, there is a different predominant dynamic in effect. Fines ratio is the most important drag factor, NOT wetted surface. If that was the case, you would see shoerter perfectly rounded bottom shells that take max advantages of their displacemt for the amount of wetted surface, i.e. wtted surface is somewhat important, but seconday. Yacht design has proven this wuite thoroughlt. Sompare the old CCA desgns to modern designs, which carry far more wetted surface for a fiven displacement. The dogma of think stricktly wetted seurface reduction led to long overhangs, with shorter water lines. Yes, these types of old vessels , were incredibly effectly in light air zephyr condions, which advantage was far surpassed by a higher fineness tatio, for a geiven displacement. In the case of the rowing shell, it is more productive to think of it a the need to minimally open then close the water, as it displaces the water, than to consider wetted surface.

[@michaelkourakoss6014]

question! is rowing on C2 sliders more "optimal" than static, in regards to doing steady state. when the overall goal is boat speed, is sliders the way to go, or are static ergs better for personal speed development

[@AramTraining]

Sliders do less harm to the back in a linear erg than static. Your specific erg is too light, though, to create sufficiently similar muscle memory to be able to use it in the boat I personally did not find an improvement on the water with any of the two options, rather the opposite

[@marcelocastelocarvalho2102]

Excelente

[@AramTraining]

Thank you!

[@DaystromDataConcepts]

This isn't a new idea in the world of rowing. I saw something like this used on a boat almost forty years ago at Henley if I recall correctly. Quite a bit of spray coming up from it. Good ideas in rowing aren't always continued. In fact, they're sometimes rejected in favour of more conventional approaches. I cannot help but be reminded of the advantages of the sliding rigger designs we saw way back in the early 80's. Empacher and Glyn Locke singles used the design. It seemed more efficient to me, but FISA banned it, so go figure.

[@ianjosephrandall]

I heard of this ... Couldn't find any details. Can you describe it?

[@AramTraining]

Excellent point made!

[@DaystromDataConcepts]

@@ianjosephrandallSadly not I'm afraid. It was a fleeting view as the boat passed and those in the know told me the spray being kicked up at the bow was due to a bulbous bow design.

[@juandlepringle9312]

This is legal?

[@reint88]

Please, the real win is in designs like the TU delft did with a hydrofoil. I believe that these clubrowers managed to go below the world record of the m8+, even though they didn't have elite fitness levels. Video can be seen here, as you can see the also adapted the sliding rigger, also a big efficiency gain: kzbin.info/www/bejne/bH7FkIhjo8prb6Msi=P4jDgz3K3nMFjDwF

[@AramTraining]

Excellent concept. However, impossible to use under the current rules and regulations. Which is exactly the point

[@reint88]

@@AramTraining yes, that's the shameful problem with rowing. The sport is stuck in a conservative thinking pattern. Lots can be gained, technically but especially in the in racing distances. I always have found it strange that rowing is the only aerobic Olympic discipline that has one racing distance...

[@ianjosephrandall]

I think any bulbous bow design will naturally have turbulence and spray. This may seem undesirable however the alternative is to have the consequences of the current surface drag. I think this will create some hesitation from the rowing community ... aesthetics over performance.

[@Jpifr]

Not exactly legal but lets watch that Video...

[@ianjosephrandall]

This has been submitted to World Rowing Equipment Committee. It does not break any laws.

[@Jpifr]

@@ianjosephrandallThat's why I said "not exactly" as it's against the spirit of the rules. In fact anything that give a advantage can be regarded as against the spirit of the rule. The rules also stipulates that the hull should be strictly a smooth displacement hull, so any wetted surface that shows some kind of nervures or hard angle could be regarded as not within the rules. I'm happy they are open to innovations but I'm scare that they would change their mind if someone or too many peoples actually shows up at an international event with this type of product. I know all that because I'm currently designing a boat for myself and asked FISA about what could be done or not and what's on the edge. Anyway, I just being geeky Cheers

[@dermotbalaam5358]

I think that inexpensive innovation will be ok. It doesn’t became an impediment to adoption, unlike for example sliding riggers.

[@jameslittle8891]

I believe the rules state that nothing should be added to the hull that modifies the behaviour of the water. This addition has a multi faceted surface specifically designed to turbulate the water, this would be classed as modifying the normal flow of the water. I would question whether disrupting the laminar flow of the water and so bringing a turbulent state of flow forward is beneficial? As an earlier comment pointed out, the surge of a racing shell compared to the steady state speed of a ship is quite different. A true bulbous bow would work better and could technically be part of the hull but in protruding forward would almost certainly hook and weed/debris and be counter productive from a drag perspective. I would be surprised if FISA allowed this.

[@ianjosephrandall]

Greetings James Little. This form could easily be made as part of the hull form rather than "added". I have been keeping World Rowing updated and all communications have been without objection and the Equipment Committee have given the commitment for it to be allowed to be used in racing.