Cruising power boat design

Discussion in 'Boat Design' started by Dan Rol, Sep 29, 2012.

  1. Dan Rol
    Joined: Sep 2012
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    Location: Florida

    Dan Rol GreenDroll

    I have been contemplating building a Chesapeake Bay Hooper Island style cruising boat using a Detroit 353 for power. My concept was around 57 feet long, 9 feet wide, 3 feet draft, decked entirely. I live in Florida and would use the boat for cruising to/from/around the Bahamas, where draft is a concern. I have built several boats (timber and plywood) when I was younger and would likely lean toward plywood, epoxy and cloth covered on a bulkhead with longitudinal frame structure, maybe using plastic panels where appropriate.
    My question is, what do you experts think of this idea? What are your estimates for what I can expect for speed and fuel consumption?
    I think I can build a sufficiently rigid hull, but I am not confident about locating the weight of the tankage and engine. I am adverse to long shafts and was thinking of a small cabin/workshop behind an engine room aft with the accommodation forward.
    I made friends with some fishermen in Annapolis back in the 1970's when I was a sailor and was impressed by the way their funky but fast launches with Studebaker engines ignored the choppy conditions on the bay, making good speed in weather I dared not take my old Hanna Gulf Weed out in.
     
  2. WestVanHan
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    WestVanHan Not a Senior Member

    Seems a prudent idea to have a NA draw something up.

    I guess you have the 353 handy,otherwise I'd put in something more modern.
    Like a reman Cummins 4BT.
     
  3. Dan Rol
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    Dan Rol GreenDroll

    I was leaning toward a 353 for two reasons, cheap and available. I looked at a marine version of a Kabuta of similar horsepower but it cost almost twenty thousand dollars...
     
  4. gonzo
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    gonzo Senior Member

  5. Dan Rol
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    Dan Rol GreenDroll

    Thanks, I have almost all of Chappelles books and have built several of his designs, the last was the 36 foot halibut schooner. I am from the Chesapeake and most of the older workboats I admired were just long v-bottom skiffs with generous deadwood keels. The boats were pretty long so it didn't seem to matter much where the weight was distributed. An engine room with tanks on each side under benches could be located anywhere from the transom forward, most of the bay launches put the engine slightly aft of the middle of the boat to reduce the shaft angle. I have seen them with the engine pretty far aft though, and while in my youth the workboat guys would drive pretty far for a flathead Studebaker engine, nowadays an over large Cat or Detroit Diesel seems to be universal, and really really heavy.
    This boat is not intended to plane, but to be relatively easy to push through the water. I thought a 353 would be plenty of power and not have to work very hard, but noisy to those that don't like the two stroke sound. Not too heavy was another consideration, as I would like to devote plenty of weight to fuel capacity. A water tank under a forward pilot house could be used to adjust the trim some, but I remember a drinking party on a big crab skiff back in the 70's (not very clearly though) where seven or eight of us were unable to effect the trim of the boat by congregating on the transom, I am guessing we weighed together about 1500-1700 pounds.
     
  6. keysdisease
    Joined: Mar 2006
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    keysdisease Senior Member

    Find an existing design you like and buy the plans. Trying to do this yourself and get it right the first time is just too big a risk for too little return. An existing design will have a track record, perhaps revisions, the engineering will already be done so there will be no guesswork.

    And I agree with WestVanHan, you can find a 4 or even a 6BT for easy money and have much more efficient power than a DD

    Steve
     
  7. Dan Rol
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    Dan Rol GreenDroll

    So no one likes the idea of the DD 353. What would one expect for fuel consumption from a 4BT? Would it generate the same torque the 353 would at low rpm? I am sure it would be less noisy and certainly less smelly. My old Lister gave me a soft spot for three cylinder engines........
     
  8. Dan Rol
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    Location: Florida

    Dan Rol GreenDroll

    Anyone interested in drawing this up for me? 57*9*3 v-bottom forward, flat bottom aft, big skeg, full length deadwood keel, balanced rudder, decked with a small pilothouse forward, standing headroom throughout (except maybe aft). Single screw diesel, lots of tankage, non-planeing. Fabricated in plywood over longitudinal frames is my preference, but I can build in steel as well. I have built a few cross planked boats, but I would like to avoid it with this one. Overall goal is something that will not gulp down fuel that I can take on extended fishing trips into the Bahamas (where fuel is even more expensive than here).
     
  9. WestVanHan
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    WestVanHan Not a Senior Member

    Dan -I assume you'll want to reg and maybe insure it,don't know your laws but will they even allow a DD into a new build?

    Can get a new block and reman 4BT for $4-5k,a reman twin disc trans-I don't know.
    I do know there are many old Cummins from Dodge trucks in fishing boats-so it has been done a lot.

    Consumption I think the BT are around 20 hp/gallon/ hour,the DD around 15 hp/gal/hr.
    So suppose it takes 80 hp to run your boat,Cummins= 4 gph,DD=5.4 gph
    So say 1.5 gph difference which is $6 an hour more,put on a few hundred hours and the Cummins is free.

    Google-marinise 4BT, reman 4BT,etc look on ebay for an idea of price.
     
  10. Tad
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    Tad Boat Designer

    1 person likes this.
  11. WestVanHan
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    WestVanHan Not a Senior Member

    Brand new-not reman- ones are $5500 for the basic engine...
     
  12. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    By using a great engine that is less common in the marine industry BIG savings are easy.

    As all have an SAE bellhousing , sticking on the marine tranny of your choice (a reman to save bucks) is off the shelf bolt on.

    With a keel cooler and Dry stack , no marinization of the engine is required.
    No wet manifolds , no heat exchanger , no seawater pump or filters.

    My favorite is the International DT 360 or 466. These are very well made , and can be had with or without electronic fuel injection. Mechanical, and repairable , for me.

    They are used in skool buses which when crashed are replaced , not repaired (taxpayer pays) .

    An engine with under 20,000 miles (abt. 400 hours) should be about $3000 , more $$$ with fewer miles.

    They seem to be becoming more common on lobster boats as cost counts to commercial folks. With the proper pilot house design (well located hatch) the engine can be R&R overnight for replacement instead of repairs.

    Service life probably 3X a cummins 6 cyl pick up truck engine.
     
  13. p_smith
    Joined: May 2010
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    p_smith Junior Member

    I like the concept, is there a reason for the exact dimensions? The beam could be pushed a little more to 12 ft or so since it is too big for a trailer anyway?
     
  14. p_smith
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    p_smith Junior Member


  15. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    Cummins recommendation is to rebuild when it uses a litre of oil in 10 hours.

    I know people with 6-8k hours and doing fine with little or no oil use,and 15-20k hours in gen set situations with a 6BT.

    At the end of the day,any decent engine will last far longer than anyone will ever use-he'll never hour it out.
    If wee're talking used, a good used 4BT will go for $2-3k.
     
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