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Thought this article sounded interesting.  Might work on sailboats too? Maybe those orcas off Portugal this summer were trying to tell us something. 

https://france3-regions.francetvinfo.fr/bretagne/finistere/propulsion-des-navires-une-nageoire-de-baleine-mise-au-point-par-l-ifremer-et-bluefins-1973236.amp

Google translated of French version:

Ship propulsion: "a whale fin" developed by Ifremer and Bluefins
Reduce the energy consumption of ships by 30%: Ifremer and the Breton startup Bluefins have developed an appendix, comparable to a "whale's fin". This uses the energy of the swell to help propel large ships.
Posted on 02/26/2021 8:09 AM
Updated 02/26/2021 at 10:05 am
Whale fin for boat designed by Ifremer and Blue Fins
The size of the foil (in green) adapts to that of the ship: it can reach 25 m long and 10 m wide for a 300-meter boat • © Blue Fins
Finistere
"The idea is really to reduce the consumption of large ships by adding a device to them that recovers the energy of the waves to transform it into auxiliary propulsion for the boat," Olivier Giusti, architect explained to AFP. naval head of Bluefins.

The device should be marketed by 2023, say in a press release the French Research Institute for the Exploitation of the Sea (Ifremer) and the startup, based near the headquarters of Ifremer in Brest.

The foils are like submerged airplane wings that support the ship and reduce the friction of the boat's hull on the water. Their movement, generated by the swell, makes the ship move forward a bit like a whale's tail

Olivier Giusti

60389ccf7c9b3_la-taille-du-foil-en-vert-est-adaptee-a-celle-du-navire-elle-peut-atteindre-25-m-de-long-sur-10-m-de-large-pour-un-bateau-de-300-m_1-5210248.jpg

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I like the idea that the motion of the vessel up and down on a wave- which is going to happen anyway - is what provides propulsive power.   The Rolls-Royce wave foil aims at reducing fuel costs - sort of like a spoiler or wing on a car?  The Ofoil aims at replacing propellers, but still has an engine to drive it.  The leading edge uses water flow to generate electricity. Though the electricity could be used to move the boat, that probably isn't efficient, and wouldn't work well if you wanted to go downstream.

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1 hour ago, PaulK said:

I like the idea that the motion of the vessel up and down on a wave- which is going to happen anyway - is what provides propulsive power.   The Rolls-Royce wave foil aims at reducing fuel costs - sort of like a spoiler or wing on a car?  The Ofoil aims at replacing propellers, but still has an engine to drive it.  The leading edge uses water flow to generate electricity. Though the electricity could be used to move the boat, that probably isn't efficient, and wouldn't work well if you wanted to go downstream.

It would work great, if you want to go downstream faster than the current.... oh wait

FB- Doug

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Anyone remember the Gosfin?  I remember her (it?) in Bronte harbour c. 1980.  A strange fiberglass egg with fins sticking out to turn wave action into forward motion.  Hearsay says it worked, sort of.  Obviously not well enough to encourage replicas.

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Have had a bit of exposure to these things. If idea is to utilise wave induce vessel motions to create propulsion, it is important to note that there is certain sweet spot in vessel size due to available wave lengths (and desired speed).

So in this sweet spot it can provide quite meaningfull thrust, but outside not so much in practice.

There are also some full scale applications out there: https://wavefoil.com/teistin/

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Might help. The US Navy added a simple “stern Flap” to the DDG 51’s, etc to get a “free” 3/4 knot speed increase at no increase in fuel flow. Alternatively, the last numbers I saw showed a $240K annual fuel cost savings per ship following the installation. . believe it or not, fuel burn/cost is tracked very carefully as it’s big bucks across a battle group. A million here. A million there starts to add up. 
 

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The point of those papers: while something simple does work, in fact biology has evolved amazingly efficient systems that utilize many, many degrees of freedom -- not just one or two as in the first post. It is these many degrees of freedom that provide the efficiency, not just wiggling a fin. Sculling with a single oar is substantially less efficient (but sometimes more convenient) than paddling or rowing or a propellor.

Propellors are pretty efficient, especially if the diameter can be large enough. A propellor with the same diameter as a whale fin is VERY efficient.

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imple idea with too many parts to break, rememeber the sea is not always kind.

 

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Lift increases with the square of velocity. 
 

That is why props work better than flapping wings. Our motivation technology is fundamentally better than nature.

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  • 2 months later...

Everglades Challenge, Race to Alaska...all look for human powered propulsion for light sailboats.  Yuloh works side to side with similar idea.  Seems you could "teeter totter" on your outboard support with a long lever with a flexible fin "easier?" than side to side.  Dunno though.  

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What a terribly complicated-looking (and surely expensive) mechanism to hang off the very extreme end of your ship. Pretty cool idea until you want to go any direction but dead down sea.

 

There has to be some better way of capturing the energy of ocean swells. Our smaller fishing boat cruises at 18 knots and, when going down the tall face of a huge, long ocean swell, easily hits 23 knots. It's pretty scary when you plow into the trough at the bottom and the forefoot grabs the water and slews you over but we haven't tipped over yet...

 

I've been told that the ancient Hawaiians rode paddleboards between the islands by waiting for the swell to run the right direction and riding the face of a swell for hours at a time. I wasn't great at SUP when I had one but I can definitely see how the principle would work.

 

Honestly, it seems like simply finding and riding an ocean swell going the right speed and direction as you is a much better solution than a fragile multi-million-dollar whale tail mechanism unless the whale tail somehow works going across the swells or up sea.

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