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BigBeakie · 14-09-2021, 21:34

In past long discussions about whether there is speed robbing drag caused by the Oceanvolt regen system, what has been missing is visual confirmation, one way or the other, with a working system.

It got quite tedious trying to explain why the resultant drag is very minimal ( perhaps tenths of a knot), as members kept up the old "physics is physics" justification for their opinions on some technology they had no first hand experience with.

So, although it seems to have taken a very,very long time for a user to film the Oceanvolt regen system in operation, finally Dan of Sailing UMA YT channel has tested his new SD15 Servoprop regen systen and recorded the result, and whadayouknow? there is no appreciable drag that slows a boat down. Of course it DOES slow a boat down ( because yes, physics is physics), but as several of us have maintained from the beginning, NOT to any significant degree. Here it is at about the 25:35 point in the TY video below if you want to skip ahead:

https://www.youtube.com/watch?v=HouwSrzKvKU

NaClyDog · 15-09-2021, 06:20

I don't mean to rain on your parade but just because someone says something in a video posted online, does not make it true.

I'm not disagreeing that the drag may have a negligible impact on performance, I'm simply stating this is not any kind of proof (I have not watched) unless all the inputs have been controlled and the results can be reproduced. Is this a person's experience or are they showing actual proof?

**StuM** · 15-09-2021, 06:24

Came across this one today

**tkeithlu** · 15-09-2021, 06:36

No problem with it being low drag. The problem is that the energy used (drag) has to be more than the energy stored by the battery. In other words, the drag during generation will be more than the propulsion available as a result. It slows the boat by a fraction of a knot? It will propell the boat at a smaller fraction of a knot for the same distance/time. Any other outcome would be a perpetual motion machine.

marcjsmith · 15-09-2021, 06:53

Quote:

Originally Posted by tkeithlu

Any other outcome would be a perpetual motion machine.

As Montgomery Scott would say "I canna change the laws of physics jim"

NaClyDog · 15-09-2021, 07:01

One more question... were these people compensated in any way to perform this "test"? I'm guessing only the manufacturer and "tester" will know this but it's always important to keep in mind where the "interests" are at.

mglonnro · 15-09-2021, 07:07

Quote:

Originally Posted by NaClyDog

I don't mean to rain on your parade but just because someone says something in a video posted online, does not make it true.

Have you no faith!!

Quote:

I'm not disagreeing that the drag may have a negligible impact on performance, I'm simply stating this is not any kind of proof (I have not watched) unless all the inputs have been controlled and the results can be reproduced. Is this a person's experience or are they showing actual proof?

They are obviously not showing any definitive proof, but it looks good anyway! Can't wait to try it myself

NaClyDog · 15-09-2021, 07:10

Quote:

Originally Posted by mglonnro

Have you no faith!!

They are obviously not showing any definitive proof, but it looks good anyway! Can't wait to try it myself

Wonderful. I can't wait to hear the results from someone who isn't a paid schill and has no vested interest in the results... be they positive or negative!

mglonnro · 15-09-2021, 07:12

Quote:

Originally Posted by NaClyDog

One more question... were this people compensated in any way to perform this "test"? I'm guessing only the manufacturer and "tester" will know this but it's always important to keep in mind where the "interests" are at.

I think they mentioned a "collaboration with Oceanvolt".

Personally, I think they should record all data and make it publicly available. Btw, does the OV system support logging of performance data? Does it send anything to the NMEA bus?

Muaddib1116 · 15-09-2021, 07:36

Quote:

Originally Posted by tkeithlu

No problem with it being low drag. The problem is that the energy used (drag) has to be more than the energy stored by the battery. In other words, the drag during generation will be more than the propulsion available as a result. It slows the boat by a fraction of a knot? It will propell the boat at a smaller fraction of a knot for the same distance/time. Any other outcome would be a perpetual motion machine.

That's not how that works. It's not a rubberband. The rate of charge can be much lower than the rate of discharge, so you can have a lower drag during charging over a longer period that will equate to a higher thrust over a shorter period.

BillKny · 15-09-2021, 07:39

The problem is with the "physics is physics" answer is that it ignores the fact that physics is all about numbers. IF you really understood physics, and therefore the numbers involved, you would know that while the speed reduction MUST be real, it also IS trivial.

The real problem with this as the only means of charging a battery for an electric propulsion system is the amount of energy you can make (and store) in a mile of sailing will take you just a few yards when it is time to run the engine. Low drag = low energy production. A prop powered regen system can easily supply quite high house loads without noticably slowing the boat down. BUT... Propulsion loads are at least two orders of magnitude higher.

NaClyDog · 15-09-2021, 07:43

Quote:

Originally Posted by BillKny

The problem is with the "physics is physics" answer is that it ignores the fact that physics is all about numbers. IF you really understood physics, and therefore the numbers involved, you would know that while the speed reduction MUST be real, it also IS trivial.

This has all the flavors of the argument (one of the very few actually confirmed as false here on the forum) that a prop creates more drag when spinning than when fixed.

Is it trivial though? What may be trivial for you may not be for someone else. Trivial is subjective.

Actual and verifiable numbers would allow people to make their own determination of what is and isn't acceptable.

EngineerRetired · 15-09-2021, 08:00

Truth is, as much as I hate saying it the youtubers all have financial involvements with the vendors they talk about on their channels. I would hardly expect one of them to say, "we tried it and it sucked" when they are getting the system free or nearly free

Keep in mind this is the third oceanvolt system they have installed...

Not saying it isn't a good system, I just won't say it is based on the testimony of someone being compensated to use it.