building a pocket trawler from an S2 8.0 C

Discussion in 'Boat Design' started by popeyejackusn, Jun 3, 2019.

  1. popeyejackusn
    Joined: Jun 2019
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    Location: deland Florida

    popeyejackusn Junior Member

    I've just purchased an S2 26 ft center cockpit sailboat. I believe I can make a trawler from it. It is full displacement, 30 inch draft, with a Yanmar diesel. It weighs 5,000 lbs and is trailerable. I just wonder if anyone has heard of anyone building one from that same boat design.
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I am guessing that yours is the 8.0 C model, as per the link below?
    SailboatData.com - S2 8.0 C Sailboat https://sailboatdata.com/sailboat/s2-80-c

    Re 'making a trawler from it', what is your proposed plan?
    Are you thinking of building a wheelhouse over the cockpit area?
    Does it still have a sailing rig?
    Are you going to keep the Yanmar diesel that is currently installed?
    Is it the 8 hp YSM 8 as mentioned in the link below?
    Specifications of S2 8.0c Coming About ~ s/v Coming About https://s2-coming-about.blogspot.com/p/specifications.html
    You could put a bigger engine in (if desired), perhaps up to 25 - 30 hp at the most, but there is no point in going any bigger than this really.
     
  3. popeyejackusn
    Joined: Jun 2019
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    popeyejackusn Junior Member

    Yes, it is the 8.0 C model. I'll most likely pull the current motor YSB 8 and install a 2 GMF. Increase the fuel and water capacities. Install more ports and windows along the front of the raised cockpit. Build a hardtop from the front of the cockpit to the end of the stern. Not sure of enclosing it. It has no mast or rigging.
     
  4. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    That should turn out to be a very nice little trawler yacht.
    And with only 30" of draft, you shouldn't have to worry too much about her being 'too stiff' (re rolling) without the sailing rig.
    Re installing a 2GM engine instead of the YSB8 - this will be twice the power, so you might well have to change the propeller, depending on what the gearbox ratio is on the new engine when compared to the old engine.
    Here is some general info about the 2GM.
    Yanmar 2GM20 - Wikipedia https://en.wikipedia.org/wiki/Yanmar_2GM20
    And she should be VERY economical on fuel - at least 10 miles per gallon, probably more (15 even?).
     
  5. goodwilltoall
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    goodwilltoall Senior Member

    Saildata shows 4' draft, is it a CB boat?
    Its a small, light, displacement boat and the current engine probably gives her all the power she can use, it would be a lot of work/costs for small improvement plus take up valuable room
     
  6. goodwilltoall
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    goodwilltoall Senior Member

    Nice layout, I would concentrate on new deck and pilot house design, so many conversions ive seen turn into frankenboats
     
  7. goodwilltoall
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    goodwilltoall Senior Member

    Allweather boats, same dimensions as yours
     

    Attached Files:

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  8. Milehog
    Joined: Aug 2006
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    Milehog Clever Quip

    I'd try to catch a ride on another converted sailboat. I've heard they will roll your guts out.
     
  9. Phil_B
    Joined: Mar 2019
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    Location: New Zealand

    Phil_B Junior Member

    True - the mast acts as a roll damper as it has its centre of mass a long way from the roll axis.

    Tony Marchaj describes this phenomenon in his book "Seaworthiness - the Forgotten Factor" where he tested a model yacht in a wave tank and found that, contrary to the expected result, the model yacht without the mast was repeatedly rolled but the same hull with the mast was not rolled in the same wave conditions.

    Seek the advice of a naval architect about redistributing the ballast and/or restoring the roll inertia of the hull without the mast and even if it is possible.
     
  10. popeyejackusn
    Joined: Jun 2019
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    Location: deland Florida

    popeyejackusn Junior Member

    Well I got the boat home and started working on removing all the barnacles. I have already repaired the rudder and need to reseal the rudder stuffing box. I have to come up with some idea for the enclosure of the center cockpit.
     
  11. sharpii2
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    sharpii2 Senior Member

    I would consider adding a long, shallow keel. This would serve three purposes:

    1.) Give the boat better tracking ability, so the wind doesn't blow it all over the place.
    2.) Protect the rudder and propellor.
    3.) Dampen any rolling which is likely to happen with a hull which has a lot of form stability.

    This keel should be close to the LWL of the boat in length and deeper at the stern than at the bow. It would have little if any ballast--maybe just enough to counteract its buoyancy.

    By my envelope calculations, this keel would be about 9.6 sf in area an add at most 6 inches to the boat's draft. This is because this hull has a rather deep bow knuckle and a tucked up stern.

    You could keep the original swing keel and motor with it half retracted. This would give you the directional control you need, but it would not protect the propellor, and it would do little to dampen the roll.

    The proposed cockpit awning will add weight high up from the Vertical Center of Buoyancy, even if it is just a lightly framed fabric type.
     
    Last edited: Jun 25, 2019
  12. popeyejackusn
    Joined: Jun 2019
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    Location: deland Florida

    popeyejackusn Junior Member

    I drove down to Marathon Key yesterday and bought a Yanmar 2GMF20 for 500 dollars. It was submerged for some time. I'll rebuild it and install it in the near future. It should be a great upgrade over the old YSB8 I'm taking out. It was rebuilt and runs great. It's for sale. Cheap.
     
  13. Chuck Losness
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    Chuck Losness Senior Member

    You might want to consider adding a swim step/transom extension. Not that hard to do. It will smooth out the water flow off of the transom and help combat excessive squatting at higher speeds. It will also be a nice place to get on and off the boat. I extended the transom on my boat.

    IMG_3428.JPG

    Do a search for terminal trawlers and sailboat to powerboat conversions for more ideas for your project. I plan to do something similar if I ever sell my gulfstar 37.
     
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  14. popeyejackusn
    Joined: Jun 2019
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    Location: deland Florida

    popeyejackusn Junior Member

    That's a nice job you did on yours. I have a 31 ft 1984 Island Packet I've been trying to sell for over six months. It has no mast, rigging or sails. I'm unable to get 5000 for it . I'm on the verge of stripping it and using the 3gmf and all her internals to complete my trawler.
     

  15. goodwilltoall
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    goodwilltoall Senior Member

    I would do exactly as sharpii recommends adding a long shallow keel.
    Chuck, that extension is what I would want on any boat I owned.
    Popeye jack can you pm me re: boat for sale and location
     
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