Hydraulic drive for catamarans

Discussion in 'DIY Marinizing' started by Steve W, Nov 13, 2014.

  1. black_sails
    Joined: May 2016
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    Location: Minnesota

    black_sails Junior Member

    If you have any sources for cheap surplus hydraulics hook me up, don't keep it a secret. :^)

    You'll note I didn't tell you not to do it, just tried to point out what I foresaw the problems to be. I found it a little silly the way some people argued in other threads telling people to not do something or to do something else - it just seems more useful to explain the consequences and let someone choose themself if something is still the best solution for their particular scenario. If neither efficiency loss nor conversion cost is an issue it at least seems a viable option for some scenarios. Though I don't think it's common enough that i'd expect commercial conversions to be expected in the market which is why we don't really see them.

    If you have one show a pic of the 'single center mounted outboard' - I was always wondering whether that would be a problem under certain wave conditions and such else why don't we see it more.
     
  2. Steve W
    Joined: Jul 2004
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    Location: Duluth, Minnesota

    Steve W Senior Member

    Surplus center is one place I have looked and there are others that advertise in boats and harbors magazine. Its pretty well known that there are losses in a hydraulic drive systems but specifically for catamarans it is intriguing, by default when using an industrial gasoline engine you end up with more hp than you need anyway to compensate for any efficiency losses. While liquid cooled diesels are available in many sizes most of the smaller gas ones are aircooled which are pretty noisy because of the fan but when you get up in hp such as the Toyota ,Ford etc forklift engines they are maybe 60hp or so which is about ideal for a 40ft+ cruising cat. Heat generated is the biggest issue imho but liquid cooling the oil should not be a problem on a boat whereas in land based operations you need a large quantity of oil and air cooling. In a boat system you have to be able to keep the quantity of oil down or any weight savings is gone.
    Regarding the single center mounted outboard on a cat I have an old gemini cat with a center mounted 9.9 Yamaha high thrust an a couple of years ago we motored all the way from Connecticut to Duluth and I was very impressed, we experienced none of the cavitation issues folks warn about and with remotes and steering tied into the rudders maneuverability is excellent. I don't know how to post photos but there are hundreds of Geminis out there.
     
  3. brian eiland
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    brian eiland Senior Member

  4. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    If the plan is to run one big engine, then I would use a DC generator and electric drive motors. It would be far more efficient than a hydrolic system, less maintenance, and can double to operate the house loads (with a big inverter and battery bank). Not thathydrolics don't have their place, but I just don't see any advantage for hydrolic over electric.

    Installing a second smaller DC generator just for house loads would also provide limp home capabilities at a pretty reasonable cost.
     
  5. brian eiland
    Joined: Jun 2002
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    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Lousiane Cat

    I was, and still am, a big fan of diesel-electric (or gas-electric) drive systems, but they have proven a bit difficult to get totally right. And they have proven to be relatively expensive and cantankerous. There a several really long subject threads on them on this forum.

    Relatively simple mechanical systems are more to my likely in many cases,...and I believe more in line with the OP's intentions?

    When I imported the first F/P Louisiane 37' catamaran I put one of the new (at that time) 9.9 4-stroke Yamaha outboards on it. That engine had an extra gear reduction in the shaft so it could turn a bigger prop at a slower speed. It managed to push the 37 cat up to 7 knots in flat water, and with some cupping of the prop we got 7.3 knots at one time.

    We then ran two soft lines between the engine and the tiller crossbars so the engine was 'steered' in unison with the tiller. This was great in slow speed maneuvering during docking,...you could almost parallel park the vessel.

    These 'soft lines' were then disconnected when out sailing or powering along at speed. And of course the engine could be pulled up out of the water totally,...and/or the amount of engine/prop down in the water column could be varied to cut down on the drag presented by the amount to shaft/prop in the water (its quite surprising how drag is created by the shaft-housing/prop that is being dragged along under aq vessel,...we learned a lot about this when racing Zodiac inflatables equipped with outboard engines).

    http://www.boatdesign.net/gallery/showphoto.php/photo/15296/ppuser/399
    ...not our cat, but similar

    ...more Louisiane images
     
  6. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    Brian, what you describe on the FP is exactly what I currently have on an old Gemini 3000 and it works brilliantly, the soft lines attach to the transom hung rudders and the Yamaha 9.9 (old white one) hangs in the middle on what Gemini call the bucket, which pivots up and down with a tackle system. The steering lines have to be uncleated to raise the "bucket". When I bought the boat I had convinced myself that a catamaran needed 2 engines, That was before I tried this system. We motored the entire delivery trip from CT to MN, something like 1500 miles which included a lot of maneuvering which included many locks of the Erie canal and Trent Severn waterway so I am very happy with this system now and like the simplicity. This is the standard system on the Gemini 3000 and 3200 cats before they went with the bridgedeck mounted diesel and Sonic leg, which is still a single steerable, retractable leg, unfortunately very prone to mechanical issues. I prefer the outboard. The Yamaha 9.9 high thrust is an amazing engine and is the only one of its type in existence, that is, with really low gearing ( 2.92:1 reduction) and giant prop. Every other " high thrust" that I have found is 2.33:1 with a smaller prop. I wish someone would make larger engines with low reduction.

    Steve.
     

  7. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Brian,

    Diesel-electric is a pretty dead simple system. What all the threads on in do is try to build a battery-electric drive, which I agree is pretty stupid, or do diesel(undersized)-battery-electric.

    I am not sure that there is much to gain by diesel-electric versus two diesel propulsion motors, but I think it would be far simpler than a diesel-hydrolic system.
     
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