San Juan 21 to trawler

Discussion in 'Boat Design' started by woodlandbeacher, Oct 6, 2017.

  1. woodlandbeacher
    Joined: Oct 2017
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    Location: Delaware

    woodlandbeacher New Member

    Hey, new to the forums but read through a few threads here about people converting their trailer sailors to a trawler / motor boat.

    I recently got a San Juan 21 for a great price but I don't know how to sail and it needs all it's rigging and a sail. I've been taking it out with my Tohatsu 6hp Sail Pro and been having a blast though.

    I live right on the bay and I'm about 35 miles from some nice beach towns so I'd love to set up my boat to take that trip in a few hours down the coast and spend the weekend at a slip at the shore.

    I was wondering how much modification I would have to do to the hull to make it go at a minimum 15 knots and what size engine I should put on the back? I'd like to keep the sail pro as a kicker and setup remote controls.

    So a few ideas I had were mounting the motor on the center of the transom and extending a glass swim platform to help trim it out. Not sure if this would work or if I'd have to square off the transom. I'd really like to know if what I'm trying to do is possible without major hull modifications.

    Thanks in advance!
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    15 knots is not a practical proposition for a boat like that. You are more or less restricted by hull shape to never reach even half that. You could install a more powerful engine ands drive it past the 5 or 6 knots it would be happiest at, but all that will happen is a distinct nose-up attitude, and the engine working its guts out. It just does not have the right shape to be running at "15 knots minimum".
     
  3. woodlandbeacher
    Joined: Oct 2017
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    Location: Delaware

    woodlandbeacher New Member

    Yeah, the 6HP tohatsu I have now pushes it comfortably at 6knots. I'm guess that altering the hull would require some pretty major work?
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    There isn't much that can reasonably be done. It is just so different to a hull that is suitable for 15+ knots, no minor modifications would have any effect. And major ones that might work, would be akin to building another boat. The good news is your boat is much easier driven at say, 5 knots, than a similar sized boat that has a hull suited to 15+ knots, I realise that 35 miles is a long trip at 5 knots though.
     
  5. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    See if 5-6 knots will work for you and allow for tides, currents etc . If you have LOTS of spare time, it might work.
    And stay proud...try not to be humiliated when driftwood overtakes you ... and fish pass you with a grin!
     
  6. woodlandbeacher
    Joined: Oct 2017
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    Location: Delaware

    woodlandbeacher New Member

    Ah well I guess I'll just have to make it extra comfortable for the ride :)

    I'm pretty set on the idea of getting this boat setup over this upcoming winter to have it ready for summer beach cruises.

    I'd like to raise the cabin roof and extend it back into the cockpit and remove the bench seating and setup up a steering wheel.

    I'm not sure if I should keep the rudder and mount a motor on each side or remove the rudder and mount the new motor in the center and keep my sail pro as a backup. I like the idea of keeping the rudder so I can eventually get a raymarine tiller autopilot and have it drive itself down the coast. Is there a kit out there to setup mechanical steering to the rudder or kicker motor? I was thinking of attaching a kicker motor bracket to the rudder and motor to have it all controlled by the steering wheel.
     
  7. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    Adding stuff- Watch your weight and location.
     
  8. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    Not meaning to be a wet blanket, but the San Juan 21 is a great little sailboat, and I emphasize, sailboat. They are very popular here in the Pacific Northwest (They are named after the San Juan Islands) I think you would be better off getting the sailing rig and learning to sail. It would make your cruise much more enjoyable, and reduce the amount of noise and fuel used. And, sailing is not that hard to do. contact the class association and you may be able to find a used rig cheap. San Juan 21 Class Association http://sj21class.org/ (full disclosure; I do not own a San Juan 21 or have any affiliation with them. The closest I have come is the one two docks down from my Sea Ray. However I would love to have one, but I already have too many boats)
     

  9. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Agreed the San Juan 21 is a fine little pocket sailor, but you'll see 6.5 MPH most of the time, though you can push her to about 9 - 10 MPH in smooth water. You'll max her speed potential out with 10 HP and she'll be trimmed up pretty high at this speed.

    It can be a good motorsailor or even a "putt putt", but you'll never see anything close to the speeds you're hoping for. She's not going to like you building too much weight up high, so keep the cabin structure as low as practical, no fly bridges, etc. A small standup cuddy midship with a sitting headroom sleeping V berth forward. That's about all you can expect on this 1,400 pound puppy. Lastly, don't build her heavy, as though you likely can build her lighter with enough effort, she'll still need to weigh in at 1,200 - 1,400 pounds, so she'll be immersed enough to remain stable and not want to roll around on you, in certain sea states. In other words, leave an equal amount of the 400 pounds of ballast in this boat. This means you'll cut the case out, fill in the slot and get some lead (or cut up the swing keel) to put the ballast back in, right on top of the forward end of where the slot used to live.
     
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