Sail hull power conversion questions

Discussion in 'Boat Design' started by JohnRichard, Sep 9, 2020.

  1. JohnRichard
    Joined: Sep 2020
    Posts: 2
    Likes: 0, Points: 1
    Location: Atlanta, Georgia

    JohnRichard New Member

    Greetings all. I have a few questions which I hope this community can help me with. I have the opportunity to acquire a Morgan/Starratt Jenks 45 hull.

    It has no mast, rigging, or other sail equipment. Engine status is unknown. The interior is in workable/repairable conditions, and it currently floats, with no leaks.

    I assume it will need everything else. I thought I might ask some questions here regarding a sail hull conversion. I'm very new a figuring out these types of things, which is why I am asking questions, and have not yet said YES to taking the hull.

    Based on the owners numbers, and what I could find published about the original boat, its a 28,000 lb hull, 12,000 lb ballast, with a LWL 31.42 feet. It has a giant lead keel, and a draft of about 6 feet.

    My goals: Explore east coast, cross to Bahamas, build enough range to reach Caymans (700 nm). It would be nice to explore east coast ICW passages, Blue water crossing may not be possible, I understand that, but if a 40' houseboat, or a little 20' center console fishing boat can do it, I feel its not a stretch on calm days. It would also be nice to reach as close as possible on the inside ICW leg to Atlanta - I also understand this may not be possible with the draft.

    I don't love the overhangs, and further research leads me to believe this may not be the right hull for me.

    The calculations I did give me a hull speed of about 7.5 kts. Does that seem appropriate? The current owner suggested a 50+ Horsepower engine be fitted. That seems excessive, but it is heavy, so perhaps not? Of course the dream would be hybrid diesel electric generator, and electric thrusters. But that seems a bit expensive at the moment. Its got a prop, shaft, and rudder already, just need to choose a suitable powerplant. It is my current thinking that an electric system with diesel genny could produce more range - exchanging sail power for solar electric generation. Its not as efficient, but its better than nothing. I fear there would be less room to carry 500 gal of fuel. I could be wrong.

    I would like to turn this into an extended range cruiser/live aboard for diving adventures a few weeks at a time.

    Roll - I can only find a single video of this type of craft sailing. And I can find no videos of anyone talking about trawlerizing a larger boat such as a 45. Plenty of 12 foot and similar small sailboats, just attach an outboard and go! I read that without the mast, the boat will probably roll uncomfortably. I also read that reducing the size of the keel can help with this. Reducing the draft would be a benefit for my goals (6 feet currently to bottom of keel), but it may not help stabilization. Alternately adding a short mast could also help calm the roll, and be something to hang flags, cameras, radar from, definitely not opposed. I am not opposed to finding a mast/rigging/sails to bring it back into correctness, but I'm also not opposed to simply motoring everywhere. Speed is not essential, efficiency is more important.

    Finally, its an aft cockpit design, so adding a pilot house seems relatively straightforward? Build walls and roof area over the existing cockpit. What I would really love to do is cut a giant hole in the back, create an aft cabin, down to the waterline, change to a reverse transom with steps, and add a dive platform that would support the weight of two divers. Another dream, and likely to cost more than the project is worth.

    Love to hear thought about this. If there is a more appropriate place on the internet to ask these questions, please advise.

    While researching motorsail type boats, I did run across the MacGregor 65, which I am now in love with. Could I buy a cheap Carver 40 and do all the things I want? Sure, but I dislike the look of most wedding cake trawlers, preferring long, narrow boats.
     
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,954
    Likes: 605, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    It sounds as if the motor is not operating, which is a shame, as a demo of what the motions are like sans sails, might be informative. I guess that varies from boat to boat, and the reaction of those exposed to it, varies from person to person. I am not looking out for them, but I can't recall seeing too many sailboats that have abandoned the sails, and just motor around, and you can't see what they have done with the keel anyway, unless out of the water.
     
  3. bajansailor
    Joined: Oct 2007
    Posts: 1,244
    Likes: 340, Points: 83, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum John.
    The Starratt 45 has a powerful sailing hull - and 6'6" draft in her designed loading, which will exclude many skinny water anchorages.
    More info about her here -
    https://sailboatdata.com/sailboat/starratt-jenks-45

    Starratt 45.jpg

    Here is one for sale on Yachtworld -
    1977 Morgan Starratt-Jenks 45 Cruiser for sale - YachtWorld https://www.yachtworld.com/boats/1977/morgan-starratt-jenks-45-3645865/
    The long overhangs will do you no favours if you are intending to use her as a motor cruiser - but they add useful waterline length when she is heeled under sail, as in the photo above.
    Even if you are literally getting the boat for nothing, you should still think twice about what you are proposing - by the time you have flung a small truck load of $$'s at her to convert to what you want, you will realise that it would have been much easier / cheaper in the long run to buy a second hand motor cruiser that will be much more suitable for the job that you have in mind.
     
  4. fredrosse
    Joined: Jan 2005
    Posts: 358
    Likes: 32, Points: 38, Legacy Rep: 56
    Location: Philadelphia PA

    fredrosse USACE Steam

    For good propulsive efficiency, you need about 1.50 - 1.75 horsepower per ton, at displacement speed, about 8 knots. But you need an efficient propulsion system, which translates to a large diameter propeller at low RPM. Something like 30 inch diameter, 34 inch pitch, 350 RPM. Understand that going with a much smaller propeller will significantly cause efficiency loss. Can the hull be made to accommodate such an arrangement?
     
  5. bajansailor
    Joined: Oct 2007
    Posts: 1,244
    Likes: 340, Points: 83, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    The Starratt 45 appears to be very similar to the Morgan 45 -
    But in response to Fred's question, she appears to have a relatively small propeller aperture in the keel, hence it is very unlikely that a 30" diameter propeller could be fitted.

    Morgan 45.jpg
     
  6. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,954
    Likes: 605, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    There are vexing problems in trying to make a motor cruiser from a fixed keel heavy ballasted sailboat, a sail cat is a far more likely candidate, there being no ballast, and stability comes from form, not ballast.
     
    bajansailor likes this.
  7. JohnRichard
    Joined: Sep 2020
    Posts: 2
    Likes: 0, Points: 1
    Location: Atlanta, Georgia

    JohnRichard New Member

    https://www.sailboatlistings.com/sailimg/m/59777/IMG_1050.jpg

    Judging from the above picture, I would assume not? I can find no answer as to what size prop is standard on this make.

    From other conversations, I've just about decided to find a more appropriate project.
     

  8. Will Gilmore
    Joined: Aug 2017
    Posts: 223
    Likes: 80, Points: 28
    Location: Littleton, nh

    Will Gilmore Senior Member

    John, perhaps there is someone on here who would be happy to help you work out a design for an easy to build custom cruiser that has similar style, but performs more like a power cruiser.

    The amount of work in converting a hull like that isn't that much less than building from scratch and you have less compromise of design.

    -Will (Dragonfly)
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.