Star-Lord, Electric Trawler Conversion

[twistedtree]

Is there any info and conversation on BoatDiesel?

I don't know about conversation, but there are prop calculators that can be used to explore different props, operating rpm, and required power/load. They will also calculate boat speed based on available propulsion power. That's where the projected speed came from that I posted, but i was based on a guess of 40,000 displacement. Someone later posted another projects which probably came from the same calculator, but they will have to confirm that. The later projected was based on a more accurate 22,000 lbs displacement and showed about .5 kt speed improvement.


That would be a good place to start to narrow down a drive train that utilizes as much electric power as the builder desires, and matches that to a prop that can deliver the power to the water. Also to be considered is whether additional gearing it required/desired, or if it can all be accomplished via prop pitch and diameter with a 1:1 drive.

 

[Star-Lord]

I will check out the boatdesign.net forum. Thank you

I am on multiple forums. I use other forums for details on motor and battery control for example. This seems to be a good forum for the boating experience in general.

My props may be 23x26, 1.5" shaft. I can barely make out the markings. They are in bad shape and will soon need to be replaced. However this size may be right in the sweet spot for my electric drive setup. Better lucky than smart.

26" pitch gives me about 40 rpm / mph neglecting slip. My motor speed is voltage limited to about 4000 rpm and produces max torque up to about 1600rpm. So below 1600 rpm is a safe place to operate without concerns of enough torque. I have a 4:1 gear reduction which gives me a 400 rpm shaft speed.

I am wondering what the disadvantages of not using counter-rotating props might be. There is a slight advantage in my motor mounting if I don't use counter rotating setup.

I am still grinding out blisters and more delamination on the hull below the water line. I am concerned that this hull may not be salvageable. I really hope it is. I love the boat.

Thanks
Jeff

 

[Cliff Meima]

Assuming that you keep the rudders, In my humble opinion, there is no need for counter rotating props in your application.

 

[Nomad Willy]

Jeff,
Isn’t likely that prop will work. Too big for 40hp and way too much pitch.

Like Cliff says no need for CRP.

Hope the hull works out. It’s not ideal but very few easily driven hulls exist that are really easily driven.

 

[TDunn]

[SIZE=+1]Calculating the propeller parameters (Torque, efficiency, etc.) is actually very simple for standard props like yours. I used Oosurveld and van Oossanen (1975) (link - https://pdfs.semanticscholar.org/33ef/fe719f9292950e7f89f1122695256f16a3fe.pdf ) to calculate the propeller thrust and torque coefficients, Kt and Kq, respectively for Wageningen B-Screw Series propellers. You will also need resistance calculations for the hull. I used the methods outlined in [/SIZE][SIZE=+1][SIZE=+1]Larsson and Eliasson (1994) to calculate hull resistance.[/SIZE]You will need hull parameters to calculate the hull resistance which will require having the hull lines, but I assume you can take the lines from the hull if you can't find the designer to get them from. All very easy to do.[/SIZE]
[SIZE=+1]
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[SIZE=+1]Incidentally I considered going electric when I repowered my boat. My boat has a 32' waterline and the hull is a round chine full displacement hull which is very easy to drive. On flat water my boat requires about 5 kilowatts to maintain 6 knots. I have room for about a kilowatt of solar on my cabin top so it would take about two days to recover from 1 hour of cruising at 6 knots. At 4 knots my boat would take about 1.8 kilowatts so I could recover from an hour at four knots in a day most of the time. What decided me against going electric was the cost. I would need at least 20 kilowatts of batteries which was prohibitive cost wise back in 2010 when I was repowering. Even now usable 20 kilowatts of lithium iron phosphate batteries would cost me about $15,000, which is nearly twice what I paid for a new diesel. That cost doesn't include the electric motor, controller, battery charging capability, ancillary electrical components, mounting the motor and batteries or any of the costs for a solar array. My preliminary cost estimate back then was over $30K for a complete setup, which was cost prohibitive. Note that 20 kilowatts of battery power would give me a range of 44 nm at four knots and 24 nm at 6 knots. That would be adequate for a day cruiser that wasn't used every day, but would not be viable for multi day trips.
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[Star-Lord]

[SIZE=+1]Calculating the propeller parameters (Torque, efficiency, etc.) is actually very simple for standard props like yours. I used Oosurveld and van Oossanen (1975) (link - https://pdfs.semanticscholar.org/33ef/fe719f9292950e7f89f1122695256f16a3fe.pdf ) to calculate the propeller thrust and torque coefficients, Kt and Kq, respectively for Wageningen B-Screw Series propellers. You will also need resistance calculations for the hull. I used the methods outlined in [/SIZE][SIZE=+1][SIZE=+1]Larsson and Eliasson (1994) to calculate hull resistance.[/SIZE]You will need hull parameters to calculate the hull resistance which will require having the hull lines, but I assume you can take the lines from the hull if you can't find the designer to get them from. All very easy to do.
[/SIZE]

Thank you
will do

 

[Star-Lord]

[SIZE=+1]Calculating the propeller parameters (Torque, efficiency, etc.) is actually very simple for standard props like yours. I used Oosurveld and van Oossanen (1975) (link - https://pdfs.semanticscholar.org/33ef/fe719f9292950e7f89f1122695256f16a3fe.pdf ) to calculate the propeller thrust and torque coefficients, Kt and Kq, respectively for Wageningen B-Screw Series propellers. You will also need resistance calculations for the hull. I used the methods outlined in [/SIZE][SIZE=+1][SIZE=+1]Larsson and Eliasson (1994) to calculate hull resistance.[/SIZE]You will need hull parameters to calculate the hull resistance which will require having the hull lines, but I assume you can take the lines from the hull if you can't find the designer to get them from. All very easy to do.[/SIZE]
[SIZE=+1]
[/SIZE]
[SIZE=+1]Incidentally I considered going electric when I repowered my boat. My boat has a 32' waterline and the hull is a round chine full displacement hull which is very easy to drive. On flat water my boat requires about 5 kilowatts to maintain 6 knots. I have room for about a kilowatt of solar on my cabin top so it would take about two days to recover from 1 hour of cruising at 6 knots. At 4 knots my boat would take about 1.8 kilowatts so I could recover from an hour at four knots in a day most of the time. What decided me against going electric was the cost. I would need at least 20 kilowatts of batteries which was prohibitive cost wise back in 2010 when I was repowering. Even now usable 20 kilowatts of lithium iron phosphate batteries would cost me about $15,000, which is nearly twice what I paid for a new diesel. That cost doesn't include the electric motor, controller, battery charging capability, ancillary electrical components, mounting the motor and batteries or any of the costs for a solar array. My preliminary cost estimate back then was over $30K for a complete setup, which was cost prohibitive. Note that 20 kilowatts of battery power would give me a range of 44 nm at four knots and 24 nm at 6 knots. That would be adequate for a day cruiser that wasn't used every day, but would not be viable for multi day trips.
[/SIZE]
[SIZE=+1]
[/SIZE]

Thank you for the detail in your analysis.
Even today off the shelf solutions are cost prohibitive for me.

I hope to be able to procure salvaged batteries around $200/kwh (ie 20kWh=$4000)
My motors+controllers, gear reduction,generator, solar charge controller, house inverter for less than $5k since it will be a hack of EV components and custom built interface circuits and software by myself.

My entire project is to try and reduce the cost of electric conversion and maybe someday demonstrate boating in a limited capacity.

Jeff

 

[syjos]

Star-Lord,

Very interesting project. I've often said that if my single Lehman engine died, I would convert Sandpiper, a 40' - 40, 000 pound trawler to diesel electric.

Please continue posting the projects progress and don't let the negative comments deter you.

All you did was post your project and you started getting unsolicited advise

I'm on a lot of forums and criticism of unusual projects seems to be the norm. There are a lot of know it alls on the web that love to tell you how to do things, but have not done it themselves.

 

[Star-Lord]

Star-Lord,

Very interesting project. I've often said that if my single Lehman engine died, I would convert Sandpiper, a 40' - 40, 000 pound trawler to diesel electric.

Please continue posting the projects progress and don't let the negative comments deter you.

All you did was post your project and you started getting unsolicited advise

I'm on a lot of forums and criticism of unusual projects seems to be the norm. There are a lot of know it alls on the web that love to tell you how to do things, but have not done it themselves.

Thanks for the interest and encouragement.
Don't worry. I am pretty thick skinned.
I enjoy the negative feedback as much as the positive.
I am soliciting all feedback good and bad.
I can tell who backs it up and who doesn't.

 

[Nomad Willy]

syjos,
Did you see/read the article on PMM about 8 years ago on a Mainship? I have no personal interest in all electric propulsion but I’d really like the diesel/electric option. I loved the high and instant torque in the harbors. Also single engine twin screws has some distinct advantages. And I think as a twin engine diesel/electric twin engines of different sizes would offer even more interesting advantages.
With DE (diesel electric) can one use the propulsion batteries for domestic power? I’m probably showing my grey hole in electric propulsion but ??

 

[syjos]

I have not done a full research of the diesel/electric conversion since my Lehman keeps chugging along.

I envision charging batteries at a dock, cruising until the batteries are 1/2 depleted and firing up a large generator to replenish the batteries while still cruising. Recharge at the next dock or recharge with generator at anchor.

This is all supposition and some guess work for fun.

I've done some simple weight calculations using lead acid batteries and it may be doable. Removing the large fuel tanks and replacing them with smaller tanks in addition to the weight saving from the engine and transmission should offset the battery bank and larger generator. I have not explored lithium batteries either, new or used, due to the costs but they are coming down in price. And used components from automobiles are becoming available.

Cruising speed could be reduced by 1 to 2 knots to extend range.

I'm not expecting a 100% battery ride but possibly a reduction in fuel usage.

 

[Fletcher500]

There is nothing I can add on the topic, but I have enjoyed following along. An interesting topic. You will get some wonky comments, which are expected on any forum, but sounds like you already know that. Keep us posted as you progress through the process.

 

[hpogue123]

syjos,
Did you see/read the article on PMM about 8 years ago on a Mainship? I have no personal interest in all electric propulsion but I’d really like the diesel/electric option. I loved the high and instant torque in the harbors. Also single engine twin screws has some distinct advantages. And I think as a twin engine diesel/electric twin engines of different sizes would offer even more interesting advantages.
With DE (diesel electric) can one use the propulsion batteries for domestic power? I’m probably showing my grey hole in electric propulsion but ??

I remember several years ago at the Boston Boat show there was a ~40ft diesel/electric boat that looked great except the cost. Anyone remember the brand?
I was mainly a sailor then so only interested as an engineer. It could run from batteries or direct drive from diesel or diesel to gen. to recharge. Very interesting but big bucks. If I remember correctly, I think it had a 10 mile range on batteries.

 

[twistedtree]

I remember several years ago at the Boston Boat show there was a ~40ft diesel/electric boat that looked great except the cost. Anyone remember the brand?
I was mainly a sailor then so only interested as an engineer. It could run from batteries or direct drive from diesel or diesel to gen. to recharge. Very interesting but big bucks. If I remember correctly, I think it had a 10 mile range on batteries.

Not a Greenline?

 

[hpogue123]

Yeah that's it. Hear anything from any owners?

 

[Donsan]

Have you given any consideration to adding a frame or hard top over the aft cabin and adding additional solar panels?

 

[hpogue123]

I have 15kw (50 x 300w LG panels) on my house and 1200w on my camper (which adds to the house when I'm not using it). I plan on adding 1800w between the bimini top and sundeck on the boat from remaining panels. Check out pallet the pricing on panels, it really cuts the costs.

 

[Nomad Willy]

Yeah that's it. Hear anything from any owners?

This wasn’t the boat I was thinking about on PMM. It was modern like 80’s/90’s styling. I can dig it up when I have more time. I have a pile of PM magazines but it will take time to find. May have been direct diesel-electric w/o batts involved. Like a diesel/electric locomotive.

 

[Star-Lord]

Have you given any consideration to adding a frame or hard top over the aft cabin and adding additional solar panels?

Quick sketch of my solar panel plans.
4 panels aft with 6'6" head room and bench seating.
I want to make this strong enough to hang a dinghy.
9 panels above the saloon. 2 more forward.
Total of 15 panels.
I would love more panels and would love to point them at the sun.

However this simple fixed layout is my working plan right now.
It will change a 100 times and end up were I started I'm sure.

This layout gives me good walk around deck clearance without all the panels too high and top heavy.
I am going to make another helm station with joystick control above the aft cabin shown.
The whole thing needs to fit under an 11' fixed bridge in my neighborhood.



Thanks
Jeff

 

[Star-Lord]

I have 15kw (50 x 300w LG panels) on my house and 1200w on my camper (which adds to the house when I'm not using it). I plan on adding 1800w between the bimini top and sundeck on the boat from remaining panels. Check out pallet the pricing on panels, it really cuts the costs.

very nice

 

[Star-Lord]

This weekend I uncovered a serious blister and delamination problem with my hull. Right now I am planning to try and fix the situation. However, once I have all of them exposed I may need to rethink this donor boat. I am not happy right now. I don't know how bad it is yet.

I think I got one of the Gulfstars with the poor quality layer bonding.

 

[Star-Lord]

Here is a picture of the Prius transmission that I have working.
The center shaft is where the internal combustion engine (ICE) would connect in a Prius.

The axle CV joint is lower left and is connected internally to the electric motor with a 4.11:1 gear reduction.
This is where I plan to drive the boat shaft.
I will use the Prius axles via a rigid mounted thrust bearing to the propeller shaft.

The transaxle is all aluminium, liquid cooled and filled with lubricating oil.

 

[twistedtree]

Here is a picture of the Prius transmission that I have working.
The center shaft is where the internal combustion engine (ICE) would connect in a Prius.

The axle CV joint is lower left and is connected internally to the electric motor with a 4.11:1 gear reduction.
This is where I plan to drive the boat shaft.
I will use the Prius axles via a rigid mounted thrust bearing to the propeller shaft.

The transaxle is all aluminium, liquid cooled and filled with lubricating oil.

View attachment 89571

Is the differential part of that same assembly, and if so, how do you lock it? I'm presuming you will only use one of the output shafts, buy maybe not?

 

[Star-Lord]

Is the differential part of that same assembly, and if so, how do you lock it? I'm presuming you will only use one of the output shafts, buy maybe not?

The differential is inside. I will lock it in place. I have couple of ideas.
The transaxle is not too difficult to open and modify.

I will actually remove all of the heavy internals and just use the light weight shell during my motor mounting fabrication and moch up in the boat.

 

[twistedtree]

The differential is inside. I will lock it in place. I have couple of ideas.
The transaxle is not too difficult to open and modify.

I will actually remove all of the heavy internals and just use the light weight shell during my motor mounting fabrication and moch up in the boat.

Sounds good.


And speaking of the gear box, is it even necessary? Could you get the desired power with a direct drive from the motor to an appropriately sized prop? Or maybe the gear box is a convenient engine mount?

 

[Star-Lord]

good article.

https://www.agbm.fr/attachment/387917/

 

[Star-Lord]

Sounds good.


And speaking of the gear box, is it even necessary? Could you get the desired power with a direct drive from the motor to an appropriately sized prop? Or maybe the gear box is a convenient engine mount?

The gear reduction seems like it might be the perfect ratio needed for maximizing available power of the motor.

The electric motor stator and rotor bearings and all the gear reduction components are all part of the same assembly housing.

You could save weight by removing the gear reduction components and making a direct connection to the motor via the engine center shaft. In this case you would be at 25% of the available torque and spinning the motor very slowly.

 

[Ski in NC]

Make sure the output shaft you use can handle prop thrust load. In a car the axle shafts don't apply much thrust load. Some differential support bearings can take thrust as a component of gear loading probably makes thrust. But you want to check that.

Gear ratio probably in the "ballpark" for what you are doing. And e-motors are not picky with loading and rpm, to a point.

 

[Star-Lord]

Make sure the output shaft you use can handle prop thrust load. In a car the axle shafts don't apply much thrust load. Some differential support bearings can take thrust as a component of gear loading probably makes thrust. But you want to check that.

Gear ratio probably in the "ballpark" for what you are doing. And e-motors are not picky with loading and rpm, to a point.

I am adding an extra rigidly mounted thrust bearing to the propeller shaft mounted to the hull.
No thrust load on the automotive CV joints is expected.

 

[stubones99]

I happened to see a charter cat conversion video series about a boat named Top Secret where the gentleman had a off-charter boat that needed a complete refit and he chose to go electric instead of traditional diesel propulsion. He goes into the hows, why's and how much and how fast of the result boat.

He chose a Volvo DC genset which would not have been my choice, but has diesel to recharge the batteries (Not an AC genset, but diesel to DC genset.

He used oceanvolt propulsion drives, and said that he actually needs two, not four, but didn't know that at the time. The MFG said 4 and he went with it, but turns out the speed difference is slight, but power draw is double.

I am not sure a prius drive system would be optimum for a boat, since they are on fairly light load most of the time, where a boat is under fairly constant heavy loading.

I liked the open and honest comments of the owner of Top Secret, telling what worked and what didn't and even some unexpected benefits of the conversion.

There was an older sailboat around Merritt Island a few years ago that had two banks of panels mounted from the stub mast and adjusted with electric actuators to allow him to run completely electric, but it wasn't something you'd want to look at for long... effect perhaps, but fugly...