New Hybrid: Small diesel/ Big OB in 33' S/D Hull.

Discussion in 'Boat Design' started by rustybarge, Oct 28, 2013.

  1. Stumble
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    Stumble Senior Member

    Rusty,

    Having done no research on what motors are acceptable I am certainly not an expert. But I would guess that the electric set up would be similar in weight to the twin engine rig. Particularly if the boat would have a generator installed anyway. Just dropping the transmission and second fuel tank would probably equal out.

    As an owner I would be much more likely to go with this hybrid than a gas+diesel hybrid! just because of the complexities in dealing with different fuel systems. I am not even sure if a diesel is available with all the flame suppressing gear you would need to also have an installed gas engine.
     
  2. rustybarge
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    rustybarge Cheetah 25' Powercat.

    that's a good point, i'd forgotten that you could drop the gearboxes on the gennys, which would probably equal the weight of the windings.

    looking at the power graphs of the Yanmar 75hp at 2000 revs it's about 20hp/4.5ltrs being used to propel the boat at over 6 kts. So an electric drive for displ. speeds would be quite feasible.

    Comparing the power graphs of the 75hp and the 110 hp, they are the same capacity and the same weight. 2000revs = 1gal.hr on the small engine, and 1800revs on the bigger one. the obvious choice would be the larger 110hp.

    Yanmar 75hp:http://www.yanmarmarine.eu/theme/ya...easure - datasheet/English/Yanmar-4JH4-TE.pdf

    Yanmar 110hp:http://www.yanmarmarine.eu/theme/ya...asure - datasheet/English/Yanmar-4JH4-HTE.pdf
     
  3. rustybarge
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    rustybarge Cheetah 25' Powercat.

    The very very Ultimate spec:

    the Nelson designs are considered the gold standard of S/D hulls in the world.
    'extraordinary' handling in rough conditions is an often used phrase.


    The Dutch version is available in a single engine version in 110 hp and 440hp.

    Write up on the Dutch Nelson hull: http://www.north-line.nl/uploads/_n...at & Yachting North-Line 37 Wheelhouse GB.pdf
    Specs: http://www.north-line.nl/nl/north-line/10/80/north-line-37-wheelhouse.html

    The English Seaward version is only available as a twin setup:
    http://www.seawardboat.com/New35.html
    Specs:http://www.seawardboat.com/35CPrice.html

    [​IMG]

    A hull moulding is available for home completion, to make this project affordable.
    Guess: £40k......

    Ok, it's very heavy at 10 tons, but......so was the Jetten at 11 tons.
    So the small diesel should be able to push it at hull speed, and a big v8 petrol should get it up to 15 kts S/D cruise.

    would this type of hull be suitable, or is it too radical?
     
  4. Stumble
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    Stumble Senior Member

    Assuming you went with the single 110hp version, get rid of the Diesel engine and install a 15kw generator and a 85kw generator. The small one for displacement speeds the big one for high speeds.

    Having not looked at the details of these engines I would probably oversize the electric motor assuming it would be a reasonable price so if I wanted to toss in a larger generator the propulsion power would already be there.
     
  5. rustybarge
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    rustybarge Cheetah 25' Powercat.

    The Seaward 35' is equiped with twin 240hp to give 20kts max, 15kts cruise.
    It would be a challenge installing a big enough electric motor as the main engine, but a displacement electric outboard motor could definitetly workout very well, maybe hung on an aluminium Armstrong bracket off the back of the transom; an easy mod for any shaft drive type hull would be to beef up the transom with fiberglass and maybe through bolt a frame to support the OB so that it can tilt forwards and out of the water.

    Another option has just occured to me:
    twin outboards: electric 80hp, and 300hp petrol. the diesel generator for the electric drive could then be located anywhere inside the hull to trim the vessel.

    advantage: both OB's can be tipped forwards, so the boat can operate in shallow water.

    the Seaward has twin 250hp .....that's 2 engines at 500kg, about a ton weight of engines.

    300hp OB.....300kg (someone in the states makes a gaint v8 500hp outboard?)
    elecric 80hp....125kg
    that leaves 575kg for the diesel genny![​IMG]
     
  6. FAST FRED
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    FAST FRED Senior Member

    7kts (30-50hp/1 gal.hr) not yet!

    1 GPH will usually only produce 20 hp , perhaps 22 with common rail electronic injection.
     
  7. rustybarge
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    rustybarge Cheetah 25' Powercat.

    if you refer to post #15 on the performence figures for the 37' jetten, the 75hp diesel is dilivering over 6.5kts at 2100 revs using 4.5ltrs which is one UK gallon.....yeah I know you have smaller gallons in the states.:p

    looking at the graphs for the engines in post #17..........you're on the money at relaxing 2000 revs. :)
     
  8. rustybarge
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    rustybarge Cheetah 25' Powercat.

    Maybe the Nelson designes are too hardcore, narrow hulls deep deadrise, which will cause extreme rolling at displ. speeds.

    Plan:B

    Floating condo S/D hull.

    They are quoting 20kts max with a single 375hp/8 tons, that's more like it!

    This hull has got a good reputation for seakeeping ( taking into account it's bulk).

    there's also a hybrid option offered.......

    [​IMG]

    [​IMG]

    [​IMG]
     
  9. rustybarge
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    rustybarge Cheetah 25' Powercat.

    Most UK boat manufactures will supply a hull moulding for home completion.

    Question: when rigging up a seperate wing engine to drive the main engine's prop shaft, will 'side load' torque applied to the main engine gearbox wreck the output shaft/bearings?

    Is there another solution to driving the main propellor shaft?
     
  10. eyschulman
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    eyschulman Senior Member

    I had a 16,000 lb lobster type at 38 ft with a 440 hp main diesel max speed low to mid 20 ks. I hung a 15 hp OB on stern and got 5-6 K. I suspect a 30 hp would have got over 7 K since the boat had a straight bow and long waterline with a hull speed about 8 K. Now thats a duel speed boat without any fancy and silly nonsense.
     
  11. rustybarge
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    rustybarge Cheetah 25' Powercat.

    aah yes....:D, but the original concept was a little bit different, that is to run a S/D hull 99% of the time at 7 kts displ. speed, because no normal citizen could afford to fill up at a fuel burn of less than 1mpg.....only cruising at 15kts in a beam sea, to stop rolling.

    so the small engine has to be a 75hp diesel, at 1 gal/hr instead of 2gal/hr with an outboard or large 440hp diesel at idle.:)
     
  12. rustybarge
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    rustybarge Cheetah 25' Powercat.

    Looking at an in-between hull, less radical than the Nelson, and less of a tub than the Broom: The Aquastar hull is really just a beamier Nelson hull design, leaner than the Broom and without the fly bridge.

    [​IMG]
    [​IMG]

    http://www.lochin.com/show_boats_for_sale.php?stock_id=LOCH 1022&boat=AQUASTAR -Oceanranger 33

    275hp gives a cruise of 12kts, max:16 kts........so should be perfect to dampen roll at 16kts.
    But is 12kts fast enough to steady the ride?

    The Merc. 5ltr mpi v8 260hp looks ideal as the main engine.
    Surprisingly heavy at 425kg, in comparison to the Cummins 265hp diesel at 392kg.
    Prices: Merc listed at £13k, (And the Cummins diesel at £30k.(both with outdrives))

    So we've saved £17k by choosing the Merc v8 as the main engine.

    The Yanmar 75hp(110hp same engine) diesel weighs 215kg, price: £12k.

    we're still ahead taking the two engines into account.

    (And the Suzuki 300hp outboard is £23k, the 250hp is £21k.......275kg.)

    Hull moulding : £45k
    Engines: £25k

    Next: Which engine drive setup?
     
  13. eyschulman
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    eyschulman Senior Member

    I still don't get it. With diesel motors big or small new or old one us gallon of fuel will yield 20 HP. If it takes X hp to get 7.5 K it matters not to the boat what size the motor is other than its weight. So a 75 HP motor at 7.5 K should burn about the same fuel as a 300 HP motor at 7.5 K. The only justification for the smaller motor is cost and weight. The concept that the 300 hp motor will get ruined at lower loads and rpm has been debunked especially with common rail newer technology and smart management. So if you want to travel at 7.5 K with the ability to go faster you select a hull form like say fast semi displacement and put enough power to get high end speed and run the boat at the slower speeds to save on fuel. I and many other boaters have been doing this for many years now. FYI a smaller motor does not in itself make a more efficient boat most of the efficiency will come from the hull form and overall weight of the boat. There is a boat sold in US northwest that uses a asymmetric cat hull with a single diesel that takes advantage of this and does well at low and higher speeds fuel wise(Aspen cat). You still have to attain the HP needed to move it at a cost of one gallon per 20 hp. The concept of putting two motors on the boat to attain efficiency makes no sense to me I don't get it.
     
  14. rustybarge
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    rustybarge Cheetah 25' Powercat.

    Ships of all sizes have multiple engines. A friend of mine worked as an engineer on a small 150' coaster, it had the main engine and two smaller 1000hp wing engines. They often just coasted along on one of the smaller diesels between Ports, when they weren't in a hurry, saving gallons of fuel.
     

  15. eyschulman
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    eyschulman Senior Member

    We are not talking ships and in recreational boats the # of motors of different sizes has little to do with fuel efficiency. Trolling motors and wing motors are very common nothing new there. The point I am trying to get across is you don't need a whopping big Ob and a smaller diesel to get efficiency and a duel speed range. A simpler approach is to keep the boat light have a hull type that will handle both ends of planed speed and a single diesel that can run at low and higher output. Why would you want to complicate that with two very different motors and two fuel types. Just the addition of petrol and its tank-age defeats some of the strong points of having diesel propulsion.
     
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