I was in SF Bay where there definitely are some currents. Even with a diesel motor I pay close attention to the tide charts.
Switched to Electric
- Thread starter Phil
- Start date
Hey, wait a minute, I thought it was I who was making all pf the insulting posts in this thread!sailboats and aux sailboats are two totally different animals. phil has a great, blue water sailboat. most of you don't. you have motorsailers. sailing from A to B is not in your playbook. you run your engine more than you sail when you go A to B. yeah, we see you and it's all good.
some boats are campers, some are condos. hiking a trail is so different than driving an RV to a campground.
phil is like a backpacker, most of yawl ain't. no need to compare the two. two different skill sets.
Given the complexity of the system; driving via the internal electric engine; regeneration of power through a turbine driven regeneration system - it is not as simple as your thought experiment.
You have to look at energy consumption via the drive system and then look at what the regeneration system generates. The impact on sailing speed is not a direct one-to-one. Just a snippet from Watt & Sea:
dj
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Hi @Phil ,
Thanks very much for the report. I'm really interested in hearing about your experience with regen once you've had time to use it more. Do you plan to experiment with motor sailing as well as regen? Where I sail, it's very common to have very light winds and strong wind on the same day, so I'm quite interested in the ability of an electric system to average that out by motor sailing when the wind is light and recovering when the wind is strong.
Thanks very much for the report. I'm really interested in hearing about your experience with regen once you've had time to use it more. Do you plan to experiment with motor sailing as well as regen? Where I sail, it's very common to have very light winds and strong wind on the same day, so I'm quite interested in the ability of an electric system to average that out by motor sailing when the wind is light and recovering when the wind is strong.
Using your example from 45% to 80% would be 105 AH for Phil’s 300 AH bank. The charger specs say it maxes out at 25 Amps @48V, which should provide decent headroom on a 30A 110V circuit. Assuming 90% charging efficiency (which Google seems to say is pretty conservative for LiFePO4 below 80% SOC) it would take 4.7 hours to go from 45% to 80%.
In any case for Phil’s use case an overnight charge after a run like that sounds pretty manageable. If most of his motor use is in and out of marinas anyway then it’s a non-issue. Keeping the speed to 2 knots is also perfectly adequate for that kind of use.
I’m with @jon hansen - this won’t work if you want to motor or motorsail for multiple days on a schedule. But if you want to be able to get your boat out sailing, enjoy the day, and have the occasional longer trip this sounds like a perfectly good auxiliary power setup.
I will definitely post more on the regen when I get a chance to test it out. Wind has been super light recently, but usually picks up in mid to late March. My daughter and I will be doing a multi-day trip in that time frame that will give us plenty of time to characterize solar and regen charging.
Thanks for pulling the actual numbers. Note that the numbers I threw out above all had "~" as in "approximate". I certainly didn't start a timer with the charge activities
. You also hit the nail on the head with, "motor or motorsail for multiple days on a schedule". This is something that I will never do. I bought a sailboat because I like to sail, not motor. I regularly do multi day trips with this boat and previous boats. In every trip so far the motor has been used to get in and out of the marina with the few exceptions when we had motor issues and had to sail back into the marina. Schedule has always been flexible and is about to get even more flexible when I take an early retirement from work.
Yeah...electric won't work for everyone, but it is more than sufficient for my needs and style of sailing.
Sue & I have been following Sailing UMA very closely for a while now and I am very interested in their experience with electric motors. For those not following them, they have progressed from a re-purposed electric motor with direct drive, to a used OceanVolt with an older saildrive unit, and now a new OceanVolt with a new propulsion system with saildrive to modernize their regen capability. I loved learning about their progression and I admire their honesty about how to cruise with electric. Their experience is invaluable and their discussions are honest.
This is good reading ... uma electric motor - Google Search
They truly sail everywhere and they discuss how they need to select weather windows when they can sail (it doesn't matter if it is cold, rainy, snowy, or whatever ... they go when they can go). One interesting discussion is they believe that when they regen with the new system, they do not sense any loss in speed - certainly not the 20% mentioned. But they regen when the wind is blowing 20+ knots anyway. They are sailors in the truest sense and handle difficult conditions rather nonchalantly.
It's a fascinating development in sailing for sure, @Phil . Keep us informed!
BTW, your installation looks fantastic! I think this is a great way to re-vitalize older boats!
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I'm curious about the regen characteristics as well. See if you can determine the speed reduction vs. charge current. That would be great to know. My guess is you won't see a lot of speed reduction, but charge will likely be only in the 30~40W range at 4 knots which is about 0.05hp so I doubt you will be able to measure the boat speed difference.
@DArcy Take a look through the Watts & Sea web site. They have about as much info as I've found. As far as the 30 to 40W range, that's low for them. Their small system puts out 100W and their larger system puts out 120W - both rated as such at 5 knots. They have a series of turbines optimized for different speeds - as one might imagine. I'm not trying to sell you on these folk, just that they seem to have more info than most. They are also the regeneration system of choice for the big around the world racers, so they can't be having much of an impact on speed or those folk wouldn't be using them. Just an observation.
The OceanVolt system that Uma uses doesn't give much info on their web site. They must have some mighty fancy engineering going into their propeller/turbine to make their system somewhat efficient at those two applications. You can't really have it both ways, you can't have an efficient propeller that is also efficient as a turbine. Well, at least I can't see how you'd get the maximum efficiency in both uses as you would having a dedicated propeller or dedicated turbine...
dj
I think a lot of people have missed the significance of this. Sailboat hull resistance is highly non-linear with speed. I ran some numbers on a hypothetical 26-foot sailboat a while ago and the effect is impressive. With 200 W (0.2 kW) boost you can add a knot of speed when the wind is very light (e.g., going from half a knot of boat speed to one and a half knots) and then, later the same day when the wind is strong, regen at 200 W with only about 0.1 knot of speed loss. That's been verified empirically by a sailor here in Vancouver who adapted an ebike drive system to a 24-foot sailboat.
That's actually one of the major reasons I'm interested in electric drives, and I suspect a lot of the people who are naysayers about the technology have failed to see the utility of that, in real-world sailing.
I was looking at the output curve for the 300, at 4 knots it is 40W with the 240mm prop. I would just guess the prop on Phil's boat is not as efficient as a generator so likely less. There is a lot of guess work in my numbers so put some big error bars on them
Still, I would guess, based on the information on the Watt&Sea site that you would not be able to measure a difference in boat speed when regenerating.
Well I know this is kind of snarky but the term that came to mind was egocentric... we don't all use our boats the same way as you... and most of us weekend sailors don't run a fridge and AC unit ... topping off during the week with solar is PERFECT for some of us. Maybe not the way you use your boat but for others the positives (no gas, silient motor etc.) outweigh the negatives.
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@Phil
Thanks for such a fantastic and info filled post. I have been thinking my way down this rabbit hole for some time and this was very helpful.
@Phil Herring can I nominate this for a sticky post?
Thanks for such a fantastic and info filled post. I have been thinking my way down this rabbit hole for some time and this was very helpful.
@Phil Herring can I nominate this for a sticky post?
That statement by Watt & Sea is nonsense. I am not kidding, I'm an electrical engineer, and I've made a study of energy conversion. Any bit of energy generated by the hydro charger is taking speed off your boat. Otherwise, it would be magic. Where do you think the energy is coming from?
That has nothing to do with what I posted. It doesn't have to do with use patterns or anything else like that, it's basic physics.
Well, yeah it does. You were critical and snarky at the start and before making those comments you and no one else had inquired about the boats intended use.
When someone posts about an unusual modification to their boat our collective assessment of that modification should include the boats intended use. As Sailing Uma demonstrates sailing long distances on the ocean with electric prpolsion is doable, even in high latitudes. Under other circumstances electric propulsion is a poor choice. A journey down the ICW with electric propulsion would be exceedingly slow and frustrating to most.
Let us all ask the right questions before issuing snarky comments about someone’s actual or intended boat modifications.
As a mechanical engineer, it makes perfect sense to me. They have a 300W unit which they say is used on boats up to 35 feet, and there a 600W unit for bigger boats. If you look at the power generation curves for the 300 you will see that it doesn't get to 300W until around 10 knots. You will need a LOT of power to get a 35 foot boat to 10 knots. The C&C115 I race on rarely gets there, only on a reach in 20 knots of wind. I would say you are looking at well over 50hp (probably more than 100hp) to get to 10 knots. My heavy, cruising, 36 foot boat will never get to 10 knots with its 50hp motor. 600 watts is less than 1hp. It is negligible, not magic, just not measurable. You will not notice the speed impact.
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In which case, it's a waste of time and money to try to put a meaningful amount of energy back into a propulsion bank with such a generator, no?