Oceanvolt Servoprop regen tested by UMA

[s/v Jedi]

Originally Posted by Tupaia

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.

We’re talking about sailboats; they use sails for propulsion. If conditions don’t allow sailing, you anchor or heave to and wait for the tide to turn or the wind to come down. Going at it for 4 hours at wide open throttle is how motorboats do it

[Dave_S]

Just out of interest

Some big numbers here, and this is before the new props

https://youtu.be/ebSotPQd3JY

[NaClyDog]

Originally Posted by Dave_S

Just out of interest

Some big numbers here, and this is before the new props

https://youtu.be/ebSotPQd3JY

How many boats do you know that can sail 20+ knots and for how long?


Also, the kw that are displayed... is that going into the battery or what is being generated?

[Adelie]

Originally Posted by StuM

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

Yep, +1

[wingssail]

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.

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?

Physics tell you that the electricity gained from regen is very low compared to the electricity required to move the boat and that the drag which results is not huge. But those are not the germane fact.

What is germane is that for most cruisers (and boaters in general) it is impractical to depend on the power gained through regeneration to drive your boat whenever you might want to. That is the fact that we need to keep in mind, not the physics of what percentage of the speed is lost to provide what amount of electricity.

Of course it is possible to have and enjoy a boat powered by an electric motor, and though regeneration you can obtain some usable power. With a big enough unit and plenty of good wind, you can get quite a lot, but not enough to run your motor for very long.

And even that requires a change in the way that most people use their boats, which I don't think is practical.

Most people motor much of the time, and almost all people simply turn on the motor whenever the sailing conditions are bad (light wind, strong wind, any wind on the nose) or when they just feel like it. I am a prime example: I am a sailor, first and foremost, yet I motor about 25% of the time during normal cruising. I could not do this with electric, it just isn't possible to collect enough watts to drive my boat 20-50 miles on electric power, mileage under power which I do from time to time. So I'd have to change my cruising habits. I admire those people who make this choice and can do it. Few people would.

My boat uses about 7,000 watts to motor at 5 knots. A 20mile trip under power would require 140,000 watts (or 280 hours of regen). Or 23 days of solar if I had 1000 watts of solar, which I don't have. I have less than 300 watts of solar. If I am coastal cruising where there are no marinas or recharge stations, anchoring each night, and where the winds are often light, electric just isn't going to work. I have to change my cruising habits.

So regen or hydrogeneration may be a good thing, but electrical power for cruising boats will only be practical and appeal to very few boat owners and regen won't change that. That is the fact that is important, not the physics of regen vs drag.

[Adelie]

Originally Posted by Tupaia

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.

If I was cruising I would not motor against current and 45kt wind unless it was a lot less than 7nm or there was an emergency reason regardless of whether I had an ICE or electric motor. I would find a hidey-hole and wait out the wind.

There are values judgements here:

You want to be able to progress despite significant wind and current against you.

Other people value things that EP gives theM: independence from needing to fuel up, philosophical opposition to fossil fuels, they don’t have the money to fix the inboard the boat came with. They are willing to have their schedule bend to accommodate adverse conditions.

Both ways are fine.

[wingssail]

By the Way adelie, the assumptions you put in your example about UMA are not valid, in my view.

Originally Posted by Adelie

...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.

UMA needs go go 6.4 knots to make 300 watts. In your example you spoke of doing that for 24 hours. I doubt that UMA's average speed under sail is 6.4 knots (or 153nm/per 24 hour day). More likely, if you look at 36' cruising boats, you'd find that they plan on 100-125 nm per day, about 5kts on the average. Far less than 300 watts I'd say. When evaluating something it is best to use a conservative figure not the most optimistic.

The most optimistic calculations are common in justification of electric boats using regen. People talk of 15 knots with a cruising catamaran. But I think it is rare that cruising cats average those kinds of speeds over long periods of time.

Further, to generate all that power that some people think is possible I think a lot more drag will be produced.

What UMA is doing is possible and admirable. It is not cruising their boat using regen to fully recharge their motor's batteries. Their passages will be too short for that unless they dramatically restrict their hours of motoring (which they obviously do). They aren't even crossing oceans.

[Muaddib1116]

Originally Posted by wingssail

What is germane is that for most cruisers (and boaters in general) it is impractical to depend on the power gained through regeneration to drive your boat whenever you might want to.

Is Oceanvolt actually marketing this claim?

[seandepagnier]

Originally Posted by Tupaia

. 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.

Somehow I sailed all over NZ and did not have an engine in the boat. Also captain cook did.

Entering NZ I was down to 1 knot SOG against a 45 knot headwind and strong current.

I don't believe you. A lot of people say 45 knot headwind but it's really only 25 knots. Did you sail to the south island?

Almost all the currents in NZ are tidal and reverse after a few hours.

The 7Nm journey took 4 hours with engines running pretty near WOT the whole time.

Completely idiotic thing to do and easily avoidable.

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.

What "record" ? I sailed from vavau (northern tonga) to NZ in 9 days (1200 miles) on a 27ft monohull. I didn't make any records I doubt you did either.

The regen is adjustable so there is no penalty: you can turn the regen off. The drag is no where near 1 knot.

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.

You have no concept for how inefficient your 30hp is. It is equal to far less than 22000W electric power. Something diesel junkies (addicts) fail to acknowledge is that their inboard drive system is a pathetic 20% efficient at best on top of 25% engine because your propeller is too small. Same with the uma prop, it is just too small to be efficient.

So until you correct this, you cannot even speak about horsepower with any sense of honest figure or calculation. Like trying to row your boat with a stick instead of a paddle and talking about calories burned.

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.

You said "can certainly be done" which implies it is adequate then contradict yourself in the next sentence saying it is inadequate.

[mglonnro]

Originally Posted by Muaddib1116

Is Oceanvolt actually marketing this claim?

Well, no. They recommend a hybrid system with a diesel generator for that use case.

[Tupaia]

Originally Posted by s/v Jedi

We’re talking about sailboats; they use sails for propulsion. If conditions don’t allow sailing, you anchor or heave to and wait for the tide to turn or the wind to come down. Going at it for 4 hours at wide open throttle is how motorboats do it

No, we are not, we are talking about replacing ICE with electric. Like I said if you want to "sail" take out the engine altogether.


In the instance I cited NZ do not allow anchoring prior to checking in under any circumstances dangerous or not. A fellow sailor unable to motor against the conditions ran aground and spent a miserable and stressful night on their side in the mud. He was refused permission to anchor or call for assistance.


Here are a couple of other examples where inadequate power or duration would be restrictive.


The Panama Canal.



I have been pinned against a dock unable to get off or out of the harbour without using full power.... in order to "sail" around to the other side of the island and anchor.



Have you ever tried "sailing" out over a bar against standing waves? The best time to do this is when there is little or no wind and it requires a lot of sustained power.


Have you ever entered a lagoon through a pass requiring full power and then having to motor for 10's of miles to avoid coral heads?



The Kinabatangan river requires 2 days motoring up and 2 days motoring back down, through the jungle no chance of sailing at all and nowhere to recharge. You could of course row.



Friends motored hard for close to on a day in order to reach Richards Bay in SA to beat an impending storm where many boats were damaged. I turned round and beat back to La Reunion under "sail".


The number of recreational boats that don't have motors is miniscule as are cruising boats with only auxiliary power. You just have to look at the engine hours on second hand boats and the size of fuel tanks on monohulls in particular to get a handle on how much the majority of sailors depend on their engines.

[wingssail]

Regen can be good to generate electricity for your house loads and help with motoring to a limited extent.

Most of us are coming to the conclusion the depending on Regen and other renewables isn't going to get you much useful energy to be used driving your boat. Most boats at least. (An aircraft carrier-like catamaran with 30,000kw of solar might have a different case).

What I object to is not folks like UMA or others willing to change their cruising (motoring) habits to make do with electric motor, given the envieronmental and other benefits.

It's the foolish ones who want a cheap engine replacement and use exagerated scenarios to justify it, and the electric motor/systems sales people who let those claims go un-challenged because they are trying to make a sale that I object to.

Originally Posted by 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.

You see, this is how proponents of these systems exagerate then build a case upon the exageration. How can you claim that the sails are pusing with 40hp when the claim is that UMA (for example) only needs 4300 watts (5.7hp)? to go 5 knots? The wind is pushing with 7 times as much power as is needed with the engine?

On the other hand, if the sails are pushing with 5.7 hp, .5hp of drag is substanially more.

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...

Another example of exageration. The theoretical hull speed of a boat with a 29' waterline is 7.2kts more or less. But typical boat speed in that boat is 5-6 in ideal upwind condtions and 6-7 average in boisterous downwind conditions.Typical average on passages will be more like 100-125 nm (5.2kts). I challenge anyone to show data that proves otherwise,

Originally Posted by seandepagnier

...You have no concept for how inefficient your 30hp is. It is equal to far less than 22000W electric power. Something diesel junkies (addicts) fail to acknowledge is that their inboard drive system is a pathetic 20% efficient at best on top of 25% engine because your propeller is too small. Same with the uma prop, it is just too small to be efficient...

Pretty strong claims Sean, care to back them up? But anyhow, that small propeller used for motoring is just as inifficent while used for regen, even more so. The little propeller is much more efficient at motoring than regen. At 1000rpm shaft speed the propeller's 18" pitch has a theoretical advance of 1500ft/min yet my boat speed is only 500ft/min. The propeller is pushing a horizontal column of water at a much higher velocity (think of a water pump jet drive) then the boat is going. But while in regen mode the prop is experiencing water flow of exactly, and ONLY, the speed of the vessel.

Originally Posted by Muaddib1116

Is Oceanvolt actually marketing this claim?

Maybe not, the hopelessly optimistic folks who want to go electric will make exaggerated claims to justify how it will work. Usually it doesn't.

[NaClyDog]

Originally Posted by Tupaia

No, we are not, we are talking about replacing ICE with electric. Like I said if you want to "sail" take out the engine altogether.

I'm not sure it's yet feasible to replace ICE with electric unless you can get to a dock every few days of sailing OR have a reliable source of abundant power on board (e.g. genset). Solar panels and wind generators will only take you so far.

[NaClyDog]

Originally Posted by wingssail

Regen can be good to generate electricity for your house loads and help with motoring to a limited extent.

Most of us are coming to the conclusion the depending on Regen and other renewables isn't going to get you much useful energy to be used driving your boat. Most boats at least. (An aircraft carrier-like catamaran with 30,000kw of solar might have a different case).

This is an interesting point but I'm still doubtful it would be possible. Everything required would also be bigger. Maybe you could achieve greater efficiency as you increase the sizes of everything but I am doubtful.

[Dsanduril]

Originally Posted by NaClyDog

This is an interesting point but I'm still doubtful it would be possible. Everything required would also be bigger. Maybe you could achieve greater efficiency as you increase the sizes of everything but I am doubtful.

It's been done (although 30MW is a stretch )