Oceanvolt Servoprop regen tested by UMA

[Adelie]

Originally Posted by mglonnro

"$40k" is the price for the whole system including batteries and stuff. I listed the details from a real quote earlier in the thread somewhere.

Here's a link to OV's own page with a price estimate for the whole package, sans installation (Uma has the SD15).


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

Thanks for the info.

[NaClyDog]

Originally Posted by Adelie

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.

Maybe the SP is very effective but none of this math makes sense, even if you believe the marketing numbers;


"Hydrogeneration at 6kn: Approximately200W(SD) / 500W(SP)"


Really, how many hours a day can you expect to sail at 6kn? Even adding the solar of 640W, you aren't going to be adding much to the bank every day. This is even before you figure in any motor time.



"Range estimation: 25 nm (calculated with 19 kWh Li-NMC)"


Even if you only get your battery down to 50%, where do you get the 9kWh you need to top up?


Living on the hook for anything more than a few days just doesn't make much sense.

[Mike Banks]

Clearly folk here do not realize that once you reach hull speed, adding more power does not make your boat go much if any faster--

But you CAN use that excess power to counter the drag of a spinning prop which is regenerating power. That is why it makes very little difference to the hull speed once you get close to hull speed.


"Sailing Uma" is one of the most credible blogs there is--they tell it EXACTLY how it is as far as they are able. If they say so from their experience--and I have checked on most of what they have discovered--then it is so within the limits of their experiences.

Another blog well worth the following is "Free Range Sailing". I have never found anything they have said to be in error--because they do not speculate without saying so--then following through.

But one of my favourites is "SAILING GBU" I just find that for me, each time they post something new I know they are going to make me feel good.

[wingssail]

Originally Posted by tp12

You've reminded me of a question I had myself during the video - pinching? Is he describing pointing as high maintaining some speed as you can as pinching? I'm thinking pinching is the first flutter at the luff and losing drive? What's his understanding bearing in mind he's not a racing sailor

I would have thought he'd be wanting to obtain data for close hauled and not pinching; hence my wondering on his definition of pinching.

Oh and I thought I should type pinching one time - pinching...

Pinching

Pinching? Yeah. I noticed that. In fact the whole speed thing had me scratching my head. 6.4kts is pretty fast for a Pearson 36. If he was pinching (heading higher than close hauled) he'd be slow, much slower. So I don't get that.

[Dave_S]

Originally Posted by wingssail

Pinching? Yeah. I noticed that. In fact the whole speed thing had me scratching my head. 6.4kts is pretty fast for a Pearson 36. If he was pinching (heading higher than close hauled) he'd be slow, much slower. So I don't get that.

You can see from the speeds/power generated that there is a fair amount of current. The measurements are taken from speed over ground where meaningful data should be using is speed through water.

I get that this is an informal first impression but it is a bit misleading. He is giving us regen output for a speed over ground in the graph. The output should be the same for a given speed regardless of which way the boat is going relative to the wind.

I'm guessing but say for example pinching and running are perpendicular-ish to the current and beam reach was against the current, it would better explain the graph.

[wingssail]

Originally Posted by Adelie

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.

We've gotten lost in the weeds here. Forget the hypothetical and the physics. Take a step backwards and think about the overall regen vs electrical power needs for driving the boat.

Here is what is clear:

From the video it seems clear that with UMA's new OV system they can generate 300-500 watts at hull speed with apparently little reduction in speed. This is clearly a benefit. It seems more than enough to meet the house needs and keep the house batteries fully charged.

But we know that under power it will probably take 7500w to drive the boat at 5kts.

This means that they will need 25 hours of sailing with regen to get one hour's motoring. OK, 12 hours of sailing if they are satisfied with 2-3 knots under power.

Just motoring 10miles to get to their anchorage at the end of a passage when the wind drops will use all the power they gained through regen in two days of sailing, assuming they can store that many watts.

So, well, the regen of the OV system makes a good, or at lest fair, hydrogenerator, if a bit pricy.

But nothing in this analysis I've been reading here indicates that you can use regen to recharge your batteries so you can motor around under electrical power.

If you are using an electric motor for your boat, even a sweet electric system like the OV SD15, you will be mostly sailing or you will be dependent on a huge battery AND shore power to recharge it.

Well, thinking about it, that is not all bad. We all need to sail more and motor less and that seems to be UMA's choice and I credit them for it.

[Adelie]

Originally Posted by wingssail

We've gotten lost in the weeds here. Forget the hypothetical and the physics. Take a step backwards and think about the overall regen vs electrical power needs for driving the boat.

Here is what is clear:

From the video it seems clear that with UMA's new OV system they can generate 300-500 watts at hull speed with apparently little reduction in speed. This is clearly a benefit. It seems more than enough to meet the house needs and keep the house batteries fully charged.

But we know that under power it will probably take 7500w to drive the boat at 5kts.

This means that they will need 25 hours of sailing with regen to get one hour's motoring. OK, 12 hours of sailing if they are satisfied with 2-3 knots under power.

Just motoring 10miles to get to their anchorage at the end of a passage when the wind drops will use all the power they gained through regen in two days of sailing, assuming they can store that many watts.

So, well, the regen of the OV system makes a good, or at lest fair, hydrogenerator, if a bit pricy.

But nothing in this analysis I've been reading here indicates that you can use regen to recharge your batteries so you can motor around under electrical power.

If you are using an electric motor for your boat, even a sweet electric system like the OV SD15, you will be mostly sailing or you will be dependent on a huge battery AND shore power to recharge it.

Well, thinking about it, that is not all bad. We all need to sail more and motor less and that seems to be UMA's choice and I credit them for it.

Why should we forget about the physics? Physics is how we evaluate the numbers.

Under power Uma uses 4300W at 5kt. They indicated that in one of their videos. I have been recording the data for various boats as the owners provide it.

Assuming they regen 326W for 24h (326W of output become 300W after going thru the battery), they could motor for 1h40m at 5kt traveling 8.4nm.

If instead they motored at 3.0 kt they would be using 1200W and could travel 18nm in 6hr.

Why can't regen be used to recharge your batteries for motoring around? Does it create a different type of electricity that the batteries won't store or does electric propulsion use a different type of type of electricity that propulsion motors can't use?n What am I missing here?

[StuM]

Originally Posted by Muaddib1116

Dan was obviously not being very scientific, but if I recall, I think he was seeing 300W+ at around 6.5kts SOG. He then turned the system off and went up to 6.6/6.7, and turned the system back on and stayed the same and then went up to 6.8, so the wind was picking up a bit. It would be very hard to be scientific about it outside of a lab. Start watching the video at around 24min for his "testing".

SOG? There are so many variables involved there that any conclusions from a single run are essentially meaningless. (currents, direction over ground, point oif sail, wind direction, wind speed...)

[Dsanduril]

I see that StuM has joined the discussion, and just in time. I guess my reading of this thread led this ad:



And no noticeable slowing of the boat too

[George DuBose]

Originally Posted by wingssail

Pinching? Yeah. I noticed that. In fact the whole speed thing had me scratching my head. 6.4kts is pretty fast for a Pearson 36. If he was pinching (heading higher than close hauled) he'd be slow, much slower. So I don't get that.

Hull speed of a Pearson 36 is 8 knots. They can actually sail faster in flat water with no current.

Here Skylark is rounding Cap de la Hague with a following current.

[StuM]

Originally Posted by Dsanduril

I see that StuM has joined the discussion, and just in time. I guess my reading of this thread led this ad:

Attachment 245392

And no noticeable slowing of the boat too

ROTFLMAO !

[StuM]

Originally Posted by George DuBose

Hull speed of a Pearson 36 is 8 knots. They can actually sail faster in flat water with no current.

More like 7.2 knots according to the standard formula (for what it's worth).

[mglonnro]

Originally Posted by Adelie

Why can't regen be used to recharge your batteries for motoring around? Does it create a different type of electricity that the batteries won't store or does electric propulsion use a different type of type of electricity that propulsion motors can't use?n What am I missing here?

It can't be used to engine exactly the way we are used to with diesel, I guess.

So I need to update my ways of using the engine, if I go 100% electric. I can live with that

[Tupaia]

Originally Posted by Adelie

Why should we forget about the physics? Physics is how we evaluate the numbers.

Under power Uma uses 4300W at 5kt. They indicated that in one of their videos. I have been recording the data for various boats as the owners provide it.

Assuming they regen 326W for 24h (326W of output become 300W after going thru the battery), they could motor for 1h40m at 5kt traveling 8.4nm.

If instead they motored at 3.0 kt they would be using 1200W and could travel 18nm in 6hr

4300W is roughly 6hp, I can relate to hp easier than W as I have better experience of ICE.

So 6hp (a small outboard) will drive Uma at 5 knots in flat calm sea, yes no problem.

About the only times I have been completely "dependent" on my engines is when beating against wind and a current or tide in an entrance or river where sailing and tacking would be impossible. 6hp would not provide either the speed or in the case of electric propulsion the duration for such circumstances.

My current ICE setup gives 8.5 knots flat out or 5 knots for 140 hours. I have been in conditions, checking into NZ and Aus are both examples where river navigation is needed. Entering NZ I was down to 1 knot SOG against a 45 knot headwind and strong current. The 7Nm journey took 4 hours with engines running pretty near WOT the whole time. I had made record "sailing" time from Tonga, not suffering a 1 knot speed penalty for regen and was able to avoid being caught at sea trying to make landfall with a rather nasty approaching weather front.

The point I am making is if your current boat is fitted with a 30hp ICE that's 22000W why does anyone think 4300W is going to cut it. The reason it has 30hp is because experience has shown this to be the best size for all conditions.

Now if your approach is not consistent with this then why not remove the engine completely it can certainly be done. Living with inadequate power does not sound like a solution to a problem.

I also know a lot of long term cruisers, with poor performing sailing boats or who are overloaded that relay heavily on motor-sailing an option that is virtually impossible with such a reliance on regen. I have yet to meet a sailor who would rather sail slower.

[malbert73]

Originally Posted by mglonnro

It can't be used to engine exactly the way we are used to with diesel, I guess.



So I need to update my ways of using the engine, if I go 100% electric. I can live with that

Exactly. If you want to sail and have an “auxiliary” engine it could work. Other posters who try to reason between diesels and electric forget that electric is not designed to motor upwind against waves. You must be prepared to sail in that instance.
UMA is a very nice sailing boat and moves easily in light air. Their vulnerability is no breeze and adverse current- and it seems now they usually stop and anchor unless they will be docking at the end and can recharge

For mainstream sailors, I think electric could be great in the tradewind/tropical areas where solar, regen, and wind can keep batteries topped off and there’s nearly always breeze to sail in.
For me in a notoriously fickle breeze region with land ties and kids, I need the opportunity to motor for 20-30nm which you can’t do with electric