Results 1 to 24 of 24

Thread: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

  1. #1
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    I have a high regard for many of the engineer-minded folks on this site, and hope they might be willing to help me noodle a project I'm considering.

    The current situation-

    My commercial salmon troller, a 47' steel Monk design I fish in Alaska and Washington with, is going to get a new generator next year. The boat has a 21KW 208v 3ph genset that powers the freezer system, along with most other AC electrical needs while running. The freezer does not currently have a "soft start" installed, but I could theoretically add one and reduce the generator size required to do the work.

    OR-

    I could take this opportunity to keep the same size or actually increase the size of the Genset. I'd use the extra power generated to drive the boat while I'm trolling/longlining. A lot of the fishing work I do is at low speed while I'm running the freezer off the generator. On an average season, I spend about 1100 hours running my main (Sisu 6.6 liter turbodiesel, 235HP) at between 650-850 rpm, moving my boat through the water at 2.0-3.0 knots, and another 600-700 hours running at higher rpm while fishing, idling at the dock, transiting to/from fishing grounds, etc. My freezer is basically running the entire summer salmon season from July through the end of September (save 5-7 days for our August break), and during my Spot Prawn season from Oct 1 to about the 20th. Given a few more days of shutdown here and there, I run it non-stop about 100 days a year. So basically, the breakdown of hours on each engine looks like this:

    Main-
    1100 low speed hours
    650 high-speed hours

    Genset-
    2400 hours

    I'd guess at least 800 of those low speed hours on the main are racked up in 16-18 hour chunks while the genset is also running. These are the hours I think I could shut the main down and run the boat at slow speeds off of an auxillary drive powered by the genset. By doing this I would expect a small savings in fuel, and a large savings in main engine maintenance and longevity. I just rolled 17,000 hours on my main engine, and expect it to go to 30,000 hours before needing a major overhaul (my genset just rolled 25,000 hours, and the Isuzu driving it will need rebuilt or replaced soon). Finally, having an auxillary drive would be nice as a "get-home" option in the case of a failure with my aging main engine and gear. There is no TowBoat USA where I work. I limped back to town about 80 miles (took 26 hours) on a bad injection pump a few years ago, would have much preferred to shut down the main and not risk damaging it.

    My main powers my hydraulics that are required to run my fishing gear via PTO (trolling gurdies don't require much, buy my longline hauler needs about 10 GPM@1500PSI to be at it's best), so shutting down the main means I need to drive hydraulics off the genset somehow.

    I would also need to figure out a way to turn the propshaft, and this is where the crux of the matter comes in. Do I drive it hydraulically or electrically? I have a 4:1 reduction gear, so at 1000 engine rpm (the max I think I'd need to troll with in 90% of conditions) I spin the prop shaft at 250 RPM. The power curve graph I have doesn't go down to 1000 rpm, but it is well below turbo-spooling speed and my guess is I am using about 50 hp to drive the shaft at that speed. I'm very into discussing everybody's thoughts on what I am actually using power-wise at this engine speed.

    The hydraulic vs electric debate is interesting. What are the pro's and cons of each in a situation like this?

    If I do this, I can size up the genny to accommodate the new config, to a point. I'm probably limited by space to a 50KW 4 cyl turbo genset in my engine room (like this https://citimarinestore.com/en/mer-e...-1800-rpm.html ). I have a about 16" of drive shaft exposed from the coupler to the bulkhead that I could attach an auxiliary drive to somehow.

    This would be done over the next winter lay-up. From a cost standpoint, there are low-interest loans available for documented fuel efficiency increases and reduction in emissions. My genny is starting to need a bit more fuel to get the job done as she ages, so I will meticulously document all fuel burn this year to establish my baseline.

    My gut tells me to go with a 40KW genset, a robust electrically-driven hydraulic pump, and drive the shaft from a multi-piston pump driven by chain to a sprocket on the shaft. But I'm concerned a bit about the loss in efficiency by converting rotational power to electric power, then convering it to hydraulic power, then converting that back to rotational power. I think it would be relatively cheaper and easy to do, and pretty simple with some trick valving and electric actuators. A quick look at electric drives seems expensive, and is a little out of my general sphere of knowledge. Hydraulics are dead-simple to me, but the voodoo involved in controlling speed in an electric drive is so much magic smoke to me. I'm just a fisherman, after all...

    Anybody interested in working out some of the pros and cons with me on this thread?

    20190402_132153.jpg20190326_192546.jpgIMG_20200106_122549484_HDR.jpg

  2. #2
    Join Date
    Jun 2000
    Location
    Pleasant Valley NS Canada
    Posts
    24,358

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    An interesting proposal, Hans2. You are correct that the efficiency losses in routing power through engine-genset-electric motor-hydraulic pump-hydraulic motor-shaft would be substantial (I got tired just typing all that out). Just a guess, but I would suspect a loss of 30% - 40% would be unsurprising. Again just guessing, but I suspect that to achieve 2-3 knots you will need to push around 10 - 15 hp through the shaft. With efficiency losses this would mean an electric load of between 7 and 11 kilowatts. My thought would be to take the hydraulics out of the equation (hydraulics has the highest efficiency losses in propulsion applications) and use the genset to drive a 10kW electric motor that drives a chain to the shaft, with a clutch mechanism between the motor and chain drive to disengage the motor when not in use.

    A separate electric motor would be required to power your hydraulic pump for deck operations. Your information above works out to be about 10.5 hp, or about 8 kW.

    Your present genset powers the freezer and house loads with 21 kW. Add the power needed for hydraulics and propulsion, plus a little bit of 'headroom', and it appears that you're gonna need between 45 and 50 kW to drive what I have just proposed.

    I have looked at gensets rigged to drive the prop shaft via a sprocket on the genset motor shaft, but I am pretty sure that would violate any warranties you'd get with a new generator, and require a bunch of custom machining of bits and bobs. That, plus the one that I looked at - on a 'trawler-yacht' - required manually putting the chain on the shaft sprocket every time it was needed. I am quite sure that is a deal-breaker for you.

    Lastly, but just to make sure that I have covered all the bases, do you have space in your engine room for a small diesel engine dedicated to providing hydraulic power? Leave the propulsion engine to propel the boat, the genset to provide electricity, and all the hydraulics - including slow-speed propulsion - to this new powerplant. Seems like about 30 - 40 hp would be needed.
    Hope for the best, but plan for the worst.

  3. #3
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Great points, mmd. Thanks for jumping down the rabbit hole with me.

    Very interesting idea of a direct drive for the hydraulic pump. It is rare that I'd need hydraulics while running at higher speeds. I could simply rebuild my Isuzu generator engine (the gen-end is only a few years old, a Stamford/Cummins 21KW unit) for a fraction of upgrading the genset and spend the money on a dedicated hydraulic drive.

    Fitment is an issue, though. My genset is mounted ahead of my main transversely, and the only easily available space to use is on top of my starboard fuel tank where my battery bank currently is. I don't have much vertical room there, 26" max, I'd guess - and I think I'd never want to adjust the valves... Here's a pic of my freezer's compressor and condensor pump mounted on the port side, mirror image of the most available space on the starboard side-

    IMG_20200506_223458302.jpg



    Upon reflection, adding another engine to take care of, stock filters for, change oil on, etc., is less exciting to me than trying to use the Genset if possible. It is a clever idea, but the reality is if I do this I'd most likely need to do it with my Genset powering it somehow.

  4. #4
    Join Date
    Jun 2000
    Location
    Pleasant Valley NS Canada
    Posts
    24,358

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Yeah, I know... My day-to-day job is providing technical & design services to the fishing fleet and boatbuilders in SW Nova Scotia. I fully recognize that most engine spaces look like a box full of earthworms. "Aww, just put another engine down there" is usually met with astounded looks and howls of laughter.
    Hope for the best, but plan for the worst.

  5. #5
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Haha, ya, I can see that!

    I'm not going to give up yet, though - with the amount of low-speed hours on my main (a turbo diesel, not at it's happiest or most efficient running at just off of idle) accumulating each year, I do think there is an opportunity here.

  6. #6
    Join Date
    Jun 2000
    Location
    Pleasant Valley NS Canada
    Posts
    24,358

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    I agree. You may just recoup some of the expense of the modifications by not having to have your main serviced so often. Carbon build-up ain't just a problem in the sky...
    Hope for the best, but plan for the worst.

  7. #7
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    50,610

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    I read, must be over ten years ago, that tugs are doing something like this so's to save fuel when running light.

  8. #8
    Join Date
    Jun 2000
    Location
    Pleasant Valley NS Canada
    Posts
    24,358

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Well, I am off to run the mutt on the beach, go to town to do a few errands, and get supper, but I will be thinking about this intriguing proposal. If I come up with any worthy thoughts, I'll be back tomorrow morning, same seat, same 'pooter, same level of chronic confusion...

    Caio, folks!
    Hope for the best, but plan for the worst.

  9. #9
    Join Date
    Mar 2007
    Location
    East Quogue,NY
    Posts
    23,144

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    I ran a motor yacht--- 34 Beneteau Trawler--with deisel-electric main propulsion. Both the deisel engine ( A Cummins 220 in this case) and the electric motor ( I think 20 w Elco) were installed inline, on the shaft. The electric motor was aft of the diesel engine and when running the deisel, the shaft turned through the electric motor. Press a button, shut down the diesel, and you are running off the electric motor. Very slick, tidy install and slick to use. For that boat it was sunset cruises, docking and no wake speeds on electric; get up and go with the deisel as needed or wanted.

    Here's a pic I took of the engine/ motor install:

    VGFWDG6FGUPXYKNMUCXJB6DXME.jpg

    Point of sharing all this is that Elco ( no affiliation) has off-the-shelf solutions for basically what you are thinking. Not saying you have to buy a package from Elco, but if you talk to them, maybe some key details you'll need for your project will be revealed.

    This is very interesting. I'll be following!

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  10. #10
    Join Date
    Mar 2007
    Location
    Almost in BC, CA
    Posts
    6,707

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Hi Chris. i remember you and the Diamond Lil from Sitka. I left Sitka a few years ago and miss the place desperately.

  11. #11
    Join Date
    Mar 2009
    Posts
    1,995

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Install a larger engine driving the existing genset and a hydraulic pump or 2 - One for drive, one for deck gear. I worked for an engine builder one summer, and they could hang a hydraulic pump off just about any rotating shaft on the engine: Main shaft, cam, fuel pump. I saw the same on a Kubota backhoe, it had 3 - 4 separate pumps hanging off various shafts. Hydraulic pumps and motors are not super efficient, but they are very small. Using several pumps means you can customize the pump for the application, so if your deck gear needs one pressure and your drive motor needs something different, you aren't wasting energy in pressure drops to accommodate the different requirements. Also, you don't have to change the deck gear - less cost.

  12. #12
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Quote Originally Posted by TerryLL View Post
    Hi Chris. i remember you and the Diamond Lil from Sitka. I left Sitka a few years ago and miss the place desperately.
    Hi Terry - Please forgive me, for my brain has been awash at the P-bar one too many times and is failing me - how do I know you from up here?? I'm having a hard time matching the avatar to a face...


    You are right, it really is a special place to live. I am very fortunate to have been able to make this my home.



    Chris

  13. #13
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Thanks for the tip Breakaway, I've reached out to Peter at Elco and we're going to take a look at the possibility of an electric drive from them.

  14. #14
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Quote Originally Posted by robm View Post
    Install a larger engine driving the existing genset and a hydraulic pump or 2 - One for drive, one for deck gear. I worked for an engine builder one summer, and they could hang a hydraulic pump off just about any rotating shaft on the engine: Main shaft, cam, fuel pump. I saw the same on a Kubota backhoe, it had 3 - 4 separate pumps hanging off various shafts. Hydraulic pumps and motors are not super efficient, but they are very small. Using several pumps means you can customize the pump for the application, so if your deck gear needs one pressure and your drive motor needs something different, you aren't wasting energy in pressure drops to accommodate the different requirements. Also, you don't have to change the deck gear - less cost.
    This is an interesting take, and you've given me something to think about here. A variable rate piston pump via Lovejoy off the front of the crank, and I could probably belt drive (with electric clutch) a vane pump to handle deck chores. I have a clutched PTO pump on the main engine running all of my deck hydraulics now (fishing gear, boom winch, anchor winch), might be able to replicate that on a PTO off of the front of a Genny engine.

  15. #15
    Join Date
    Mar 2007
    Location
    Almost in BC, CA
    Posts
    6,707

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Hi Terry - Please forgive me, for my brain has been awash at the P-bar one too many times and is failing me - how do I know you from up here?? I'm having a hard time matching the avatar to a face...
    I only spent a few desultory evenings in the P-bar, so I doubt we met there. Maybe at SSS or SPC, or maybe on the docks. I don't look much like my avatar, but my cat sure did.

  16. #16
    Join Date
    Apr 2005
    Location
    Hills of Vermont, USA
    Posts
    41,062

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    While I'm an amateur, it seems to me that you have a generator for making electricity, so why add hydraulics into the "pushing the boat" mix? While the inline setup Kevin (Breakaway) mentions is nice - it'd mean a total redo of your drive system I'd think. Great to consider it you plan to repower though.

    As mentioned by Michael (mmd - and he is a professional) - a chain drive off an electric motor makes the most sense to me. You would need a clutch or gear setup to disconnect the prop shaft from the gearbox though.
    "If it ain't broke, you're not trying." - Red Green

  17. #17
    Join Date
    Feb 2002
    Location
    Shubenacadie NS
    Posts
    5,301

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Some sort of parallel hybrid setup could work here perhaps?
    If one advances confidently in the direction of his dreams, and endeavors to live the life which he has imagined, he will meet with a success unexpected in common hours.
    -Henry David Thoreau-

  18. #18
    Join Date
    Mar 2011
    Location
    Mukilteo, WA
    Posts
    3,481

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    It might get you made fun of down at the docks, but the easiest way to provide 15hp of propulsion is an outboard on a bracket. Would probably cost less too.

    While we're spitballing....

    I do like the electric chain drive option though. You'll only leave the clutch engaged when starting the main engine once, as I suspect the electric motor will become a smoking mess.

  19. #19
    Join Date
    Jun 2000
    Location
    Pleasant Valley NS Canada
    Posts
    24,358

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Quote Originally Posted by Hans2 View Post
    Thanks for the tip Breakaway, I've reached out to Peter at Elco and we're going to take a look at the possibility of an electric drive from them.
    A complete store-bought unit would be the best option, if it is do-able by all other constraints. Warranty, minimal custom machine work, probably more compact that cobbled-together applications, etc. If you would, it would be nice to see what Elco can come up with for you (leave the price quote out, though). Chase this lead to exhaustion before spending much time on other options.
    Hope for the best, but plan for the worst.

  20. #20
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Quote Originally Posted by J.Madison View Post
    It might get you made fun of down at the docks, but the easiest way to provide 15hp of propulsion is an outboard on a bracket. Would probably cost less too.

    While we're spitballing....

    I do like the electric chain drive option though. You'll only leave the clutch engaged when starting the main engine once, as I suspect the electric motor will become a smoking mess.
    It might be the easiest, but unless it was an XXXXXL shaft model I just don't think I could keep the prop in the water...


  21. #21
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    After much discussion with my gearbox manufacturer, I've decided to skip this upgrade for now. They didn't feel the as-built gear would survive long term use in this situation, and we couldn't find a way to plumb in an aux electric oil pump without some significant machine work and trick valving.

    Perhaps in another 13,000-ish main engine hours I will look at a complete diesel-electric conversion, but probably not...

    Thanks to every body who joined in the fun for this thought exercise.

  22. #22
    Join Date
    Jun 2000
    Location
    Pleasant Valley NS Canada
    Posts
    24,358

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    Well, that is a bit disappointing. I thought it was a fine idea, while it lasted. At least, now you know more than when you started.
    Hope for the best, but plan for the worst.

  23. #23
    Join Date
    Feb 2020
    Location
    Sitka, AK
    Posts
    25

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    I definitely do, and maybe the motor tech will develop to the point I will go diesel-electric when it's time for an overhaul on the main.

  24. #24
    Join Date
    Jan 2001
    Location
    Whangarei, New Zealand
    Posts
    1,040

    Default Re: Auxilliary drive on commercial fishing vessel - Hydraulic or Electric?

    I see that this is sort of closed now but as a Hydraulics man I was just going to say that I liked mmd's suggestion of a 3rd small diesel for the hydraulics. Couple that with a a load sense Variable pump and that could drive both your deck hydraulics at low pressure and a high pressure Bent Axis high efficiency motor (Parker VOAC F11 or F12 or Rexroth etc) for shaft drive.
    Some Gen sets also come with the option of adding a pump on the end but the fixed speed reduces flexibility and even with a load sense pump at low pressure stand-bye you are still adding some rotational load.
    Z

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •