Oceanvolt Servoprop regen tested by UMA

[Adelie]

Originally Posted by NaClyDog

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.

Their big money source is their YT subscribers and their patrons. They are not going to risk that for a free motor from one vendor.

They may unconsciously uprate their opinions slightly from good to pretty good or pretty good to great but they won’t say something is great that they feel is actually mediocre.

[Muaddib1116]

I'm not sure how they would be risking their youtube success in any way by being sponsored by Oceanvolt. In what way is that automatically a negative?

[Adelie]

Originally Posted by Paul L

So how many watts are generated per 0.1 nm of drag?

Depends on whether you are going 1kt, 3kt, 5kt, or 7kt.

Non-linear speed/power relationship.

[zstine]

if they are generating 400watts, then there's 400watts (min) of drag, or about half a horsepower. conservation of energy is a bitch! obviously if you are making hull speed and the sails are pushing with 40hp, 0.5hp drag isn't much. but at low speeds/wind, then it can be a big deal.

[Pete7]

Originally Posted by mglonnro

I (Also, I'm don't know what the dark shaded bar means )

I think the black line is the electrical power Uma needs when sailing, instruments, VHF and chart plotter etc. Presumably the regen takes some power to run itself. In other words, if they generate anything over 150w then they have a surplus which starts to charge the batteries.

Pete

[seandepagnier]

Originally Posted by BillKny

What's REALLY trivial here is generating 300 Watts and thinking you are going to go push the boat anywhere with that.

my electric outboard uses 120 watts and pushes me 2 knots.

On my boat that's my normal house load when I am sailing! It would barely keep up with my usual usage!

your "usual usage" is pretty excessive it seems

[Adelie]

Originally Posted by Pete7

And the price to you or I? about 40,000 $ or Euro.

Guess its back to the alternator on the propshaft then

Where'd you get this number?

[EngineerRetired]

Fer goodness sake, does everything on this site have to turn into a useless pi**ing match?


Seriously CHILDREN... (If you think I may be talking to you, then you are probably right!)

[NaClyDog]

Originally Posted by Adelie

Where'd you get this number?

I've done some research and it appears they were "given" a Saildrive 15 with the Servoprop;


https://oceanvolt.com/saildrive-15/

PrICE starting from: 38650€ (SD) / 46600€ (sERVOPROP)

*The price is excluding VAT, shipping, installation & certification.

[Dave_S]

For the positive.

As the boat approaches hull speed, drag increases at a much higher rate than the loss of speed created by the prop so I can happily agree there is not much speed loss.

The regeneration on a fast boat that will happily cruise at 15kn must be a huge benifit even at the cost of a couple of knots especially were you might be looking to slow down a bit.

For the negative.

I think they cooked the books on that chart.
The figures quoted are SOG not STW so they are not taking into account of the current which is clearly evident in the figures. i.e. Reading the graph, it makes more power based on apparent wind.... Not, or does it? Can it measure how much speed is lost and adjust the pitch appropriately, I doubt that's the case but maybe... Anyone?

I also wonder how much grip a small diameter prop like that will have when driving.

Jimmy Cornell's boat didn't regenerate well in swell, I hope they have fixed that.

[Adelie]

Originally Posted by Paul L

Don't have the bandwidth to be downloading long Youtubes.
So how much practical use is 300 watt-hrs? How many watts does it consume to motor at 6kts, in comparison?

I want a Cal-34. 300W-hr would push that boat at 2kt for 1hr.
To go 6kt it would take 6720W or about 22x as much power. 300W-hr would push the Cal-34 at 6kt for about 3min, netting a bit less than 1/4nm.

If I dropped the speed to about 3.5kt 300W-hr would push the boat for 20min or just over 1nm.

Longer boat with the same displacement is going to use the same power to go a bit faster, or go further at the same speed.

[Dsanduril]

Originally Posted by NaClyDog

I've done some research and it appears they were "given" a Saildrive 15 with the Servoprop;


https://oceanvolt.com/saildrive-15/

Just an observation, I don't know anything about it, but I'd love to hear a discussion (from UMA) about motor sizes. Their first homebrew was a 3.6kW motor that they pushed to 7kW. When they first looked at that and OceanVolt they were looking at the 8kW OceanVolt, and, if this report is correct, they have moved up to a 15kW OceanVolt.

That looks (from the outside) to be a pretty steady progression to bigger motors, I wonder if they find the lower speeds available at the lower power levels limiting? Or is it all a function of changes in battery capacity?

As noted, an observation, would love to hear what they have to say (and whether or not the observation is even correct).

[Adelie]

Originally Posted by NaClyDog

....
If their system was so great, why has it required 2 replacements? Do they have any additional power generation and can they actually supply all their power needs by simply sailing? How long can they actually be "off-grid" without plugging-in or starting the genset?...

The first OV motor they installed was a gift from a patron who was upgrading his catamaran. Uma wanted it because it gave them some regen and because they thought it would be more efficient than their DIY motor. Both came to pass. I believe it also occupied a little less space.

A year or so in during a haulout they noted the lower unit was making odd noises. Yep, it was bad. OV realizing the potential for bad press if they didn't act, coughed up a replacement lower unit which netted them good press. The motor itself was fine and was not replaced, it was a mechanical problem in the lower unit only and that was replaced.

This current motor and lower unit are all new, same power for traction but more efficient in the regen mode, that is more energy harvested for a given amount of drag. In order to be more efficient in regen OV had to use a fundamentally different approach in their propeller design. OV I assume did the redesign because they realized that their existing regen system really wasn't worth the money to most monohull boats given the modest output and I think they gave the unit to Uma for the PR. Uma wanted this for the significantly increased efficiency, they are trying hard to become more energy independent.

Regarding other power sources, since the beginning I believe they've had 640W of solar. They have also just gotten a vertical axis wind turbine. I'm curious about how that will work out.

With the solar they've managed to supply all their house loads and slowly build up a reserve for traction, my sense was it took over a week to recharge if they had used the motor a significant amount and had drawn the bank down.

On passage apparently they recharge faster as they are using their computers less and once they installed the first OV faster still since they were getting some regen.

Off season in the UK and Norway they have needed to be berthed with shore power in order to heat the boat.

Unless they added a serious amount of insulation to the boat, I don't see them being able to do winter cruising without installing a stove. Maybe they have, I haven't looked for it.

I have never seen them mention using a generator.

[Adelie]

Originally Posted by NaClyDog

I've done some research and it appears they were "given" a Saildrive 15 with the Servoprop;


https://oceanvolt.com/saildrive-15/

Thanks.

The SD-8 is still E13,000 per https://oceanvolt.com/saildrive-8/ but doesn't have the servoprop, apparently that only comes with the SD-15 and the E40,000 price tag. No thanks.

The SD-6&-8 have some regen just not nearly as much, the Servoprop is really effective.

[Adelie]

Originally Posted by Dsanduril

Because they didn't quantify numbers in any meaningful, scientific, repeatable way. In fact, at one point they turned on the regen and their speed went up. If that was a result of just turning on the regen we're back at perpetual motion.....

The speed going up when they turned on the regen was a function of more wind and/or moving into a tail current. They don't have a speedo on the boat, only the gps readout.