Micro Cruiser

Discussion in 'Boat Design' started by d1970, Apr 20, 2015.

  1. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    In the US you can buy a 25 foot sailboat in fair condition for under $2000 any day. We just cut two for scrap. The lead in the keels was worth more than the boat would.
     
  2. d1970
    Joined: Jun 2012
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    Location: canada

    d1970 Junior Member

    I mentioned the controls inside since my sinuses bugger me quite a bit. I'm looking into them.
    Ok,then what good,reliable small diesel genny can be found? I don't mind investing in a couple good units. In that size, there probably isn't any water cooled(radiator) unit,though I'd prefer air cooled due to simplicity. Unless the water cooled versions dont need as frequent oil changes,servicing,etc.
    Heat wont be an issue, rather a welcome addition on the cold seas.
    Gonzo,that is music to my ears.
     
  3. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    I think that if you are thinking about a genset and smallest possible boat you have bit funny balance. What do you need the genset for? Run the main engine for an hour or two/day and add a solar panel to that.

    Also I think its silly to star sailing with the same boat you are thinking of crossing an ocean with. I am going to use an analogy: I want to be a film maker and shoot the next Star Wars movie. I have near zero experience of filming but I have strong preconceived ideas of what features I want. What camera could I buy for cheap to shoot the film with?
    Sound silly, right?
    It would not be realistic to think that:
    1) You could get gear for a serious job for cheap
    2) that you would buy a camera capable for the serious job as your first camera - the same you want to learn with
    3) that you would be - as a beginner - in a position to truly understand what features and why are relevant in choosing the pro camera.

    As with the film making example it would be far far wiser to ask what is the best affordable gear to get into the _right path_ - or in this case in water.

    Get a boat you can do weekend trips with. Start with minimal gear and add as you learn to know what counts. No shortcuts to experience - but remember that gaining that experience is fun! It is also usually much more fun AND FASTER to learn on beginner friendly equipment vs something big/advanced. Same thing goes to so many other things. One example that comes to my mind is motorcycles: people who 1st get a beginner bike for a year will be better riders at three year mark than the ones who directly got the big bike.

    Not trying to discourage - jus trying to help you realize that its easy to rationalize shortcuts in your head but usually the commonly taken progressive path is the smart one.
     
  4. peterAustralia
    Joined: Mar 2006
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    Location: Melbourne Australia

    peterAustralia Senior Member

    Hi Gonzo

    How much did you get for the lead. Rough guess, a 25ft sailboat with 40 percent ballast ratio. A compass 28 has 1.8 tonnes of lead. My guess is that a 25 footer might have a tonne or so of lead, is that worth $500 to $1000?

    Then you have the fittings, compass, winches, barometer, sails, anchor, anchor chain, bilge pump, shackels, lines, depth sounder, cabin lights, maybe a vhf radio, maybe an old outboard (which might work quite ok). I wonder if these little fittings would get a bit if sold individually?

    One thought if building a new flash boat,,, build the hull, buy an old boat, take the fittings from the old one, put them on the new one.... or just buy a decent second hand boat in the first place
     
  5. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The old stuff has some value if you are in the boat repair business. Customers may need a matching winch or cleat that is no longer available. The labor of taking a boat apart and disposing of the leftover garbage makes for a small profit. However, these were abandoned boats that hadn't paid storage in years. The lead was worth $410.00. Hardly enough to break even.
     
  6. pdwiley
    Joined: Jun 2008
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    Location: Hobart

    pdwiley Senior Member

    It's not the difficulty so much as stacking losses. You run a diesel engine to generate electricity to run a motor to drive a prop shaft to push you through the water. This makes no sense on the scale you want to do it. Sure, diesel electric systems are in use but in fishing vessels and the like not small pleasure craft.

    What you want to do is adding points of failure and losing fuel efficiency not to mention increasing weight for no good reason, on a small boat hull not over-endowed with storage to start with. In addition electricity & the salt environment don't play well together.

    Afterthought: unless you have 3 phase you have no way of running in reverse - unless you plan on grafting a g/box onto the end of your electric motor which is adding more complexity. Also you have 1 shaft speed unless you add a VFD to drive a 3 phase electric motor.

    Just how big an electric motor do you think you'll need? You *do* realise that the generator has to be sized at around 6X the running current of the motor to cope with the starting current demand? You can get around this somewhat by using..... wait for it....... a 3 phase motor driven by a VFD configured for soft start.

    We've been down this road a number of times on this forum. The idea is superficially attractive but impractical. And I say that as a person with a full machine shop at my disposal, with 3 phase motors and variable frequency drives for the same sitting in my storage racks and installed on a number of my machine tools. I may even use one to drive an anchor winch, but no way would I do it for my main engine.

    PDW
     
    Last edited: Apr 24, 2015
  7. d1970
    Joined: Jun 2012
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    Location: canada

    d1970 Junior Member

    Ok,so get a boat to learn the ropes first. Makes sense Mr kerosene.
    Now,how would you go about sipping fuel ad still be able to make good progress,Mr Wiley?
    Small diesel engine with direct drive(one of those joints to take out vibration,break instead of breaking the motor when I hit something with the prop) mated to a self feathering prop ,so even at idle you're pushing? I did figure I need a 3 phase motor,maybe 1-5KW depending on boat size/weight, getting fed by a battery which would be charged by a genny, to get away from the 'large' demands at startup. No problem with the electrical/mechanical part, me pop's an electrical engineer, me mom's a mechanical engineer. Though I won't be specifying anything complex,rather simple stuff that anyone could fix/operate.
    Probably asking stupid questions,sorry for the head aches.
     
  8. Easy Rider
    Joined: Oct 2009
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    Location: NW Washington State USA

    Easy Rider Senior Member

    There was an article in Passagemaker magazine approx 7 years ago about a micro passagemaker from Australia. She was 20' long and a very creative design. Don't recall any sails. Perhaps a search would be successful.
     
  9. ch3oh
    Joined: Mar 2015
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    Location: fin

    ch3oh Junior Member

    A Fisher 25 could suit your needs. They have been around since 70's, are rather small and have a wheelhouse you can see out of. Lots of retired brit couples get a fisher and hit the baltic/med/longer voyages. It's way too heavy to trailer behind a car, a very slow sailer and even older ones might be expensive and hard to find in can/us.
    First thing you might want to do after some sailing lessons is to hitchike a offshore ride to really get a clue what it's like out there. Donate bunch-o-money to your local voluntary SAR boat, they can take you safely out on a really bad weather. Your mind and your wishlist will be totally blown when you get some experience. You'll cross out diesel-elecric propulsion too.
    One thing you'll realize by learning is that you need 2 boats- a trailer sailer and something to cross the pond. If it's all about taking the beloved family generator along, do it in the trailer boat and ffs take an outboard as backup :)
     
  10. d1970
    Joined: Jun 2012
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    Location: canada

    d1970 Junior Member

    Easy : I'm looking for it.
    ch3oh : That is one fat boat. Love the dimensions. Noted. I thought about owing two boats(one trailerable,the other heavier),
    but the costs will be doubled, so I'd rather have one for all,much like an SUV : not a proper sports car, nor a rock crawler,but does both
    onroad and offroad relatively well. Oh,and 5-6 tons is not that heavy,though I might need a CDL.
    Love this site,you lot are great.
    PS Having a OB for backup never crossed me plans. Can they motor for a full day or two?
     
  11. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    In ideal world, *if the hull shape permitted*, I'd buy a Sabb 10HP diesel engine with a controllable pitch propellor.

    However it isn't an ideal world and Sabb no longer make them so....

    Next alternative would be a 10HP single cylinder Yanmar or ideally Bukh with hand and electric start coupled to a self-feathering adjustable pitch propellor.

    There are a lot of threads on controllable and adjustable pitch props here, do a search.

    My personal choice for the 12m steel sailboat I'm building was a 36HP Bukh diesel with a 3:1 reduction g/box and a 22" Autostream adjustable pitch prop. This combination is not for the light of budget, however.

    Earlier this year I managed to acquire a Sabb 16HP diesel complete with its controllable pitch propellor, all in excellent condition. I'm hanging onto it in case I decide to build another boat at some point. There are probably a lot of these Sabb engines still running in Norway, just need to track one down.

    You, like many others, are attempting to circumvent the 'good cheap fast' rule. You only ever get 2, and that's on a good day. There is no way you're going to get a dirt cheap sailboat, even a 22' one, with a really fancy & efficient propulsion system unless you build it yourself, as I did, and even then I can assure you that it won't happen fast.

    PDW
     
  12. d1970
    Joined: Jun 2012
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    d1970 Junior Member

    Ok, the shape impacts performance, though is there a formula for calculating roughly how much hp you need to push a displacement hull through the water?
    Slow large prop vs faster smaller prop : I've read 8 hours on the subject till my eyes crossed out lol,cant make up my mind on which is better,except it seems
    with a low power motor turning a larger slow prop seems more efficient? Can you push a 10-12k lb boat with a 5hp motor? How about a 2.5hp, or even a 1hp?
    Edit : One of my favorite diesels are gardners, and unless you go into the bigger models, the 1-3 cylinder versions had very few ponies, and they were installed
    in heavy boats.
     
  13. nemier
    Joined: Jan 2004
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    Location: Panama

    nemier Junior Member


    No.

    1 hp = 500 lbs displacement

    12,000 lbs = 24 HP, to push at full chat for a displacement vessel.
    However, my personal rule of thumb is that 37% of the HP figure is typically used at cruise, so 37% x 24HP = 8.7 HP (5hp still not enough, although will get you somewhere I suppose,,,but good luck in weather & tide.)
     
  14. Rurudyne
    Joined: Mar 2014
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    Rurudyne Senior Member

    Nemier, I'd previously read power estimates for at around 5, or even 10, HP per ton (never really clarified exactly which ton: long, short, metric, Ancient Alien...) which may be slightly higher to much higher than what you gave above.

    To make sure I understand you correctly, say a 10,000# boat like a Bolger Wyoming, 51'6", would only need, rough estimate, 20 HP for displacement speeds at "full chat" (a new term to me). Now, the description of the boat says that with a 50 HP engine "well throttled back" it would get about 8kt. Or roughly an SLR of 1 for the boat.

    I guess what I'd like to clarify is what in your estimate generally is "full chat" for a displacement hull?

    http://www.hallman.org/bolger/Wyoming/
     

  15. nemier
    Joined: Jan 2004
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    nemier Junior Member

    Hi Rurudyne,
    Sorry for the local colloquialism ; ) full chat = WOT (wide-open-throttle) Maximum rated HP for the engine. The point at which an increase in HP would not create any more speed for the full displacement hull, just push water up hill.

    The estimates you have read about are all correct, but they typically refer to slightly different circumstances or boats (hulls). For instance, I find different HP requirements for diesel engines vs gas engines. Not a lot, but yes, slightly different.

    The "1 HP = 500 lbs" example I presented was based on a full displacement hull which I currently have experience with.

    The "4 HP = 1 Ton" usually refers to a metric ton, or Tonne (Te) which is 2,200 lbs. So, in this case, this equates to 1 HP = 550 lbs (2200 / 4 = 550)

    You see there is not much difference, just some figures a little more acurate than others. I'm finding that this precise accuracy is not warranted though, because there are so many other factors involved affecting these calculations.

    My biggest take-away recently, is that many full displacement vessels are in reality, overpowered. If you use my boat as an example. The maximum designed Gross Tonnage of 77 Te (169,400 lbs) calls for a 338 HP engine (169,400 / 500 = 338 HP) I have a 325 HP continuous rated Lugger (Komatsu block 6125A). I burn 6 gph at cruise (7.8 kts) which equates to 120 HP, which means I'm only using 37% of the engines HP, 95% of the time. And my installation is a conservative example. Many other vessels have way more HP than is required.

    Anyway, lets get back to your Bolger,,,
    Yes, 50 HP would be more than enough to power the boat, and 20 HP would be the more realistic max required for displacement speeds (SL 1.0 - 1.2). In reality, 10 HP would be all that you'd need to propel the boat at cruising speed most of the time. HOWEVER, I note the boat was not designed from the get-go as a full displacement hull, so I'm sure these calcs would be tainted in some way. :eek:
     
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