Ok complete change of plan

Discussion in 'Boat Design' started by Boston, May 4, 2010.

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  1. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Just one thought.

    The Atkin boats were using GASOLINE engines at that time.

    Even the best , purpose built boat engines cruised at 50% power and higher power was for minuets not hours.

    That means Atkins choice, a 70 Hp Red Wing or similar could easily be replaced with a far lighter diesel of perhaps 40 rated HP.

    That starts a great design spiral, lighter more efficient engine , less fuel needed for the same range . All good.

    Using a bigger engine (70HP diesel) would not make the boat appreciably faster ., only empty the fuel tank quicker.

    FF
     
  2. Easy Rider
    Joined: Oct 2009
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    Easy Rider Senior Member

    He's going to make the boat much bigger Fred so the 70hp may be just fine.
    And the run aft is rather straight, very much like the Handy Billy that goes 12 to 15 knots on a 21' hull. Another Atkin design (Tang) is very similar in basic form and is a 26' boat w 35hp specified. I don't know how much I agree w you on the Atkin power specs. Many of his boats seem underpowered w the power specified but your implication/statement that they only used half that leaves them WAY underpowered. I was there in the 50s and I remember marine engines had special valves, guides and other parts to handle high continuous loads. I also remember going up long mountain passes in big old sedans without much power "pedal to the metal" for fairly long periods. Sure the old engines wore out about twice as fast as a modern engine but they worked very well until they died. I do wonder how to interpret Atkin's power specs. I assume his power specified is for an engine that makes that amount of power as it's maximum output. I think his speeds are maximums also. A full disp boat could/should be spec'ed for the power required to attain it's design speed which is well under max speed and a SLR of one. But I see that if a boat is capable of 8.5 knots and designed for 7.5 knots working speed the boat will be spec'ed for the power required to make 8.5 knots. What think FF

    Easy
     
  3. Boston

    Boston Previous Member

    all other considerations aside I am struggling to justify not buying a new engine

    what size engine is another question entirely but the idea of swapping out my old engine isn't sitting as well as it could be

    I'll probably just buy a new engine and trany combo
    assuming things work out the way I'd like to see em

    cheers
    B
     
  4. masalai
    Joined: Oct 2007
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    Location: cruising, Australia

    masalai masalai

    Depends where you feel you may like to cruise but "nanni' is based on the Kubota, has a very good reputation for reliability and parts throughout the Pacific and Australasia and a 4 cylinder 40 to 50hp saildrive would make a neat and easy package to install and give you capacity to swing a standard of folding 15" or so wheel and no shaft log and stuffing box etc to worry about...

    I have 2 x 21hp 3 cylinder saildrives at 144Kg each and got the OEM pack which is the full package for engines sorted... for AU$32,000.00 odd from memory... including fuel filters and folding props - everything... With the fitting of a pair of mini-keels, everything is "protected" and she sits straight when the tide goes out...
     
  5. Easy Rider
    Joined: Oct 2009
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    Easy Rider Senior Member

    masalai,
    What is "nanni"? The Bear is not a sailboat ..why would Boston want a sail drive. I've seen what Vetus has to offer. Slick units to be sure and as I peck this post advantages are poping into my mind. I can't imagine anyone buying a folding prop and suffering the efficiency loss not to mention the dollar loss.
    $32,000 for 42hp package sounds extreme to me. I paid about $8000 for my 40hp power system (except gear box). Enlighten us .. what are the advantages of saildrive?

    Easy Rider
     
  6. masalai
    Joined: Oct 2007
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    masalai masalai

    http://nannidiesel.com.au/Marine-Engine/Sail-Drive/N3-21-SD/ is what I have (a pair of), and the range options include http://nannidiesel.com.au/Marine-Engine/Sail-Drive/N4-50-SD/ and the image is not a saildrive but uses a shaft and "normal mounting" - I like the saildrive for its minimalist approach to holes in the hull... and I have seen them used to great effect on "displacement speed" power-boats... - Just a nice option and if cruising the Pacific/Australasia, a model where one can readily get spare parts at a reasonable price conveniently... - It all depends on what region one proposes to cruise, say year 5 to 10 after the build... USA stuff may be the best choice in the Eastern Pacific/Western Atlantic, but not necessarily so elsewhere...

    Last I looked, Post #91 by Boston, the image had a stick and steadying mainsail, to me that qualifies as a sailboat? - and a mighty fine live-aboard cruiser at that, in the dimensions proposed by Boston in his next post, except for the toothpick of an anchor may need to be re-rigged for some sandy bottoms when the 'trades get up'.... My build continues here http://boats-n-stuff.com.au/forum/index.php/topic,2.new.html#new
     
  7. Boston

    Boston Previous Member

    my option to the engine out of my truck which has less than 100,000 on a IDI international 7.3 diesel is to go find the most common diesel engine manufactured for the longest period of time and mate it with a similar transmission

    think Chevy 350 of the diesel world and you will begin to get the picture of what Im after

    off the rack all the way and none of this custom expensive stuff, I want parts whenever I need them and cheap cause they made millions of it, whatever it is.

    if they made a diesel tractor motor in the power range I need that would be perfect cause we have more farm equipment supply houses than we will ever know what to do with in this country. My bet is International diesel makes a 70 hp diesel low RPM heavy duty tractor motor and that would be the kind of thing I am after. The Atkins is a moderately paced power cruiser and this motor is not going to be "pushed" to its limits. Instead its going to be a nice easy cruiser working in an area known for dead heads and snags. No sense in bombing round the countryside when there's pot holes everywhere, if you know what I mean.

    just looked it up and the most popular and most produced diesel ever was the GM 6-71 but its in the 200+ hp range so I'll have to keep looking

    ok so I been looking for a while and Im almost inclined to try and find a factory rebuilt 7.3 just like the one I have cause its only 170 hp and all the other most popular models are in the 200+ range

    what I need is a dam popular 70~100 hp naturally aspirated diesel with a marine transmission kit or rigged to a simple generator and I run an electric motor cause I need a gen set anyway and the house bank can buffer the gen set to the motor

    oh well
    Ill figure it out eventually
     
  8. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    Tractor diesels are a good option in that they are often used in their rated max output for full working days. But they are often heavy, with cast iron oil pans etc. In newer (21st century) engines finding a normally aspirated diesel engine gets harder because of the emission rules pushing for intercooled turbos.

    We have two Perkins diesels around the farm, one is driving a Swedish Jonsereds 5-cutter shaper plane and the other is now driving a circular saw mill. The first is a D27 that I believe has been used in boats and the other is A4 212, mostly found in MF 165 tractors. Both are rated around 60 hp. These are older engines but the parts are still easy to find.

    Lurvio
     
  9. Brian@BNE
    Joined: Jan 2010
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    Brian@BNE Senior Member

    Tractor diesels also typically have large radiators for cooling, but in an enclosed engine room in a boat they might still be undersized. If you then need to 'marinize' with wet manifolds etc, why not just go to the older marine diesels anyway? And a bit of cross checking might point to, for example, a Perkins Sabre that has the same block/short motor as the Perkins tractor diesels that Lurvio mentions, so repairs and maintenance can still source parts from the farm suppliers.
     
  10. masalai
    Joined: Oct 2007
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    masalai masalai

    Too many options Huh Boston?, Progress on the build will force the choice eventually, like, will fuel be available in 2 to 5 years when USA is busted and broke?
     
  11. Boston

    Boston Previous Member

    nah Im getting them narrowed down

    got the boat picked out and now for the engine

    got a pretty good idea as to what I want in a motor so my choice of a very common diesel tractor motor is perfect to fit that bill

    after that its the transmission and little stuff

    Im going to aim for no through hulls so I'll have a few issues surrounding that but no big deal
     
  12. masalai
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    masalai masalai

    I thought you might - that is why I suggested a sail-drive, - which also has a spare access for sea-water... My intention being to pump from the inlet point to feed the RO watermaker system...
     
  13. Boston

    Boston Previous Member

    I dont really have the sails to drive the sail drive
    the Atkins has whats called steadying sails
    they are designed to slow the roll motion in a sea state and provide some assistance off the wind
    a few knots at best
    maybe three or so but not much and certainly not enough to make sail-drives worthwhile
    Ill have some wind turbines and maybe ( big maybe ) an electric hybrid system
    thing is I just want to get on the water with a minimalistic system so nothing fancy and nothing I cant service myself
    most common engine preferably with interchangeable parts
    locally produced and able to run through a common transmission
    nothing custom for me
    what I want is serviceability all the way
    ease of maintenance and guaranteed parts availability right off the rack if you know what I mean
    Im aiming for a minimalistic approach to the mechanical on this thing
    I probably aught to start a new thread for the best engine transmision choice as I have a lot to learn about the options and it would be an interesting study with lots of input from all our usual friends who generally all have some really good input on things like that.

    anyway hope all is well
    B
     
  14. Easy Rider
    Joined: Oct 2009
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    Easy Rider Senior Member

    I bought my new engine from:
    klassenengine.com
    They cater mostly to the fishing fleet in the greater PNW. They specialize in Isuzu and Mitsubishi. Sample their prices. All or most of their engines feature steel (special alloy) exhaust manifolds. Trust me and tell them your a fisherman when they ask.

    Easy
     

  15. Boston

    Boston Previous Member

    wouldnt be far from the truth Easy cause I plan on doing fishing guides if I can get the boat up to coast guard specs for x number of passenger
    I love fishing and I love to put folks onto some fish if I can
    that and its just a dam good time to take folks out and show them the wilderness
    my boats going to be slow
    easy
    comfortable
    safe
    and has plenty of beer in the fridge
    that and I'll have nothing better to do than fish all day anyway, so I should know the local water pretty quick
    might even hire a guide to help me get to know the tricks of the area

    cheers
    B

    oh
    I'll be making my decision based on sales and availability so the engine is going to be a "most popular" variety and not just something exclusive to boating, hell add the word marine to anything and double the price is what I seem to remember, so I'll definitely not be buying a "marine" engine. Thing will most likely be an off the rack model for farm use. Ill use the two speed trany common to the modern tractors and go with the dry exhaust system and standard radiator. Hell its Alaska for Petes sakes Im sure I could use the extra heat and if not I'll run the coolant through the hand rail just a Mark suggested.
     
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