Oceanvolt Servoprop regen tested by UMA

[Rjstutch]

Originally Posted by EngineerRetired

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.

Not so, it is the 2nd motor was oceanvolt which was a gift from a follower or patron. The first one was a forklift motor converted.

[BigBeakie]

Dan said in his latest UMA vid ( at 4:40 mark) that regen meets their house loads at 5.5 knots and over 6 knots they are charging their batteries with the excess regen produced. And they have had no solar input for several days, so all the power to run the house and charge batteries is coming from the regen only when under sail.

For a cat that makes 8 to 10 knots under sail, the regen starts to add up fast.

[jmh2002]

@BigBeakie

IIRC you have regen installed on your cat I think? How is the noise from the rotating prop, shaft, motor, etc, when in regen mode?

[Tupaia]

Originally Posted by BigBeakie

For a cat that makes 8 to 10 knots under sail, the regen starts to add up fast.

The drag adds up very fast too. Typically this is about 20% so at 8 to 10 this reduces to 6.4 to 8 respectively. This is not necessarily a linear increase either as a rotating propeller will have an effect beyond its diameter the faster it rotates that can only really be determined empirically. This is reasonably well (better) understood in aeronautics where the propeller efficiency can be expressed as a function of the flight speed, but is still difficult to calculate. Also demonstrated by the twisting of blades on wind generators (Aerogen).

In addition the drag is not just the effect of the propeller itself but the disturbance of the flow around the hull. This maybe why towed and remote (WhatandSea) generators are quite successful on cats because they do not change the hydrodynamics of the hull.

A cat relies heavily on the low form drag to achieve the speeds that it does having a propeller disturb the laminar flow around the hull could and most probably does have a more profound effect on the speed unlike the case of a monohull where this is largely absorbed by the excess sail power once it has reached hull speed. So when comparing regen the type of vessel is very relevant.

[Adelie]

Cat rely on the very narrow beam of the individual hulls and the comparatively light displacement to achieved higher average speeds.

A flow disturbance near the stern is not going to affect boat speed significantly more than the same disturbance well aft of the stern.

Percentage drag of prop relative to the hull does not vary in step with the total drag in the hull. Because it is full immersed Drag of the prop varies with speed thru the water per a power function of the speed. Drag of the hull varies as a power function of the speed and another function that depends on speed and length.

As the boat goes faster the percentage drag of a prop drops whether it is fixed, spinning freely or spinning with energy extraction.

[JustMurph]

Originally Posted by Tupaia

The drag adds up very fast too. Typically this is about 20% so at 8 to 10 this reduces to 6.4 to 8 respectively. This is not necessarily a linear increase either as a rotating propeller will have an effect beyond its diameter the faster it rotates that can only really be determined empirically. This is reasonably well (better) understood in aeronautics where the propeller efficiency can be expressed as a function of the flight speed, but is still difficult to calculate. Also demonstrated by the twisting of blades on wind generators (Aerogen).

In addition the drag is not just the effect of the propeller itself but the disturbance of the flow around the hull. This maybe why towed and remote (WhatandSea) generators are quite successful on cats because they do not change the hydrodynamics of the hull.

A cat relies heavily on the low form drag to achieve the speeds that it does having a propeller disturb the laminar flow around the hull could and most probably does have a more profound effect on the speed unlike the case of a monohull where this is largely absorbed by the excess sail power once it has reached hull speed. So when comparing regen the type of vessel is very relevant.

Is this based on your practical experience on a fast cat equipped with regenerating electric drives?

[BigBeakie]

Originally Posted by jmh2002

@BigBeakie

IIRC you have regen installed on your cat I think? How is the noise from the rotating prop, shaft, motor, etc, when in regen mode?

Not noticeable on any OV boat I've been on.

However watch the below video of Kato sailing at over 20 knots and regenerating over 5.5kW from each motor. At that speed you'll hear the prop whine from the high RPM's. If you were ever going to hear anything, it would be then.

You hear that because there is no roaring diesel......

https://www.youtube.com/watch?v=6xi7gXDHc6Q

[jmh2002]

Originally Posted by BigBeakie

Not noticeable on any OV boat I've been on.

However watch the below video of Kato sailing at over 20 knots and regenerating over 5.5kW from each motor. At that speed you'll hear the prop whine from the high RPM's. If you were ever going to hear anything, it would be then.

You hear that because there is no roaring diesel......

Thanks for the info, I'll check out the video

[JustMurph]

I think another important point that needs to be made (in the context of a fast cruising cat with regen), even if the claims of 20% loss of speed were true (which I doubt), when you're regenerating 1.5-2kw @ 10 knots....your batteries will be full in no time. Not to mention with the amount of solar going onto BigBeakie's boat he'll be making power by moon light.

So once your batteries are full, you're no longer regenerating and there are no losses to speak of. It's not like you've permanently made your boat slower.

In fact I'd go so far as to say with a big solar array you won't even need to use regenerating very often. Only on successive overcast days.

[BigBeakie]

The idea that there is anything like a 20% loss of boat speed due to regen prop drag on the Oceanvolt systems, is just laughable. When you turn it on and off, repeatedly, there is no perceptible change in speed over the normal tenths of a knot fluctuations due to moving in a seaway. I don't know how many times that has to be restated for it to sink in. This is NOT A FIXED PROP!

You watched it for yourself in the UMA vid. If they lost 20% off the 6 knots they were going, it would have dropped to 4.8 kts. It didn't.

[Pelagic]

Not to derail this electrical propulsion thread, but is there another thread about electric outboards as featured on sophisticated lady?

[JustMurph]

Originally Posted by BigBeakie

The idea that there is anything like a 20% loss of boat speed due to regen prop drag on the Oceanvolt systems, is just laughable.

I'd like to see someone actually produce some evidence of this 20%...

[NaClyDog]

Originally Posted by JustMurph

I'd like to see someone actually produce some evidence of this 20%...

Good on you. I would like to see someone actually produce some evidence of what is being claimed in this thread.


At the risk of sounding like a broken record, a youtube video is not evidence.


I think if reality matched the claims, there would be many many more people doing this and we would have ample proof.

[malbert73]

Originally Posted by Tupaia

A cat relies heavily on the low form drag to achieve the speeds that it does having a propeller disturb the laminar flow around the hull could and most probably does have a more profound effect on the speed unlike the case of a monohull where this is largely absorbed by the excess sail power once it has reached hull speed. So when comparing regen the type of vessel is very relevant.

Adelie:

Cat rely on the very narrow beam of the individual hulls and the comparatively light displacement to achieved higher average speeds.

.

Correction - “fast cats” , which are rarely seen on new boat market- rely on narrow beam and low form drag to achieve higher average speeds.

Standard production “condo” cats have more drag than most boats and average speed only is faster in heavy breeze

[lestersails]

Originally Posted by NaClyDog

I think if reality matched the claims, there would be many many more people doing this...

Not at the prices I have seen quoted in this thread!