How heavy is the Cap on this Boat?

Discussion in 'Boat Design' started by RWJData, Feb 4, 2015.

  1. RWJData
    Joined: Jun 2014
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    RWJData Junior Member

    Hi All,

    I have started this project boat, and have completed the Transom and Floor, but I am now wondering if I remove the Cap, how mush weight am I likely to save?

    It is a great late 60's vintage Hull with four foam filled Stringers and is as solid as a rock. I feel the deck is heavy, so I want to remove it, and make a simple dinghy out of the Hull. Obviously, it will need some strengthening, but a lower centre of gravity would be nice too!

    I am not looking for greatness here, I just want a solid fishing boat with a low power outboard, my days of going flat chat are long gone. This is a "DoForNow" boat, as I have another 4.8m Glass Hull to prepare for my retirement in a few years.

    What is you valuable opinion about removing the Cap? Please.

    Cheers
     

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

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Boats of that vintage tend to be quite heavy. Don't be surprised to find large hunks of plywood and solid wood buried in the laminate. Even if it's all 'glass, it'll still be pretty heavy. As to how much, well it's tough to tell, but assuming the boat is about 18' and it's a typical 60's era layup, a few hundred pounds wouldn't be crazy, maybe more, maybe less.
     
  3. RWJData
    Joined: Jun 2014
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    RWJData Junior Member

    Yes, you're right, the deck is at least 1/4" thick, with plenty of Ply reinforcement. There is also solid Round tubes across the foredeck, so I would like to think by removing it, I can achieve a nice open runabout with a lower Centre of Gravity.
    The hull is 4.8m (15ft) and 1.65m wide, with around 18* deadrise at the stern. She is solid and good lines, so I go ahead and get it done.

    Thanks for your interest as well. I will continue to post some pics as I move thru the reno process.
    Cheers
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If you remove the deck cap, you dramatically weaken the athwart stiffness of the boat. In fact, once you remove the cap, you'll note the sides will become very floppy and the hull shape will possible distort, just from it's own weight.

    Usually, when you do this sort of work, you'll want to support the hull along the centerline and along the bilge a bit, possibly with a 2x4 nailed across the hull in a couple of spots, just to insure it stays the shape it is, before the cap is removed.

    What ever you replace the deck cap with, will need to have a small flange along the sides, which will form little sides decks, maybe say 6" (150 mm) wide, bow to stern. This will restore most of the lost stiffness, though you'll likely need more, especially forward. A casting deck could serve this role as could a mini foredeck maybe 12" - 18" (300 - 450 mm) deep on the centerline. You'll also want some hanging knees under the sides deck, bonded to the hull shell too.
     
  5. RWJData
    Joined: Jun 2014
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    RWJData Junior Member

    Hi Par,
    My research has seen a number of ways to achieve to achieve this, and I am willing to give it a go, as I have mentioned , I have already have the Transom and Floor done, so the "stiffness" i need to deal with is above that, and I will put a number of Knees in before the cap comes off, and two cross beams to hold it in place. There is already a mini foredeck (Foam Filled) under the bow section, but i know it is only thin Glass, but a quick ply overlay will quickly strengthen that area. A seat Across the front about a quarter of the way back will gibe me a strong front. The sides won't need too much work. Across the transom will be a full width seat (Boxed in Cupboards under) to hold the Transom intact.

    I will follow up with about a 25hp or 30 hp 2 Stroke.

    Should be nice when it's finished.

    I appreciate your input, it confirms my thoughts as well.

    I promise to put heaps of pics online soon.

    Cheers & Regards
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Boat seems to be built like a brick out-house, I doubt 25 or 30 hp will get it moving to your satisfaction. Maybe 50 ?
     
  7. RWJData
    Joined: Jun 2014
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    RWJData Junior Member

    That's why I don't want to throw it away! It also has some nice lines to the hull.
    Yes, a very solid vessel, so if I could save the hull, and lighten it up by removing the cap, I am looking at a good boat.

    As i mentioned earlier again, I also have a 4.8M Savage Whittley "Centurion" Hull only, which is NEW.....It came out of the mould with some damage to the Gelcoat. I bought it for A$152.00. It has a 2.2m beam, so I just can't wait to get into this project, but it is for my retirement, so I have a few years to get it right. For now, this little project is just to get me on the water quickly.

    I have to work tonight, but I am getting some pics together for everyone to follow.

    Cheers for now!
     
  8. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    Your existing cap already has the needed strength.
    Par mentioned taking off the cap you will need to build a strong shelf 6 inches wide.
    Well you already have that 6 inch shelf in the cap.

    When you finish making a new cap how much weight are you really saving?
    And if you make your new cap to be as strong as needed, your going to have one looking similar to what is there now.

    Why not just cut back the forward part of the cap where the steering wheel is then extend the existing cap all the way to the bow?
     

  9. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    The actual weight will be about 1 lb for every square foot, per 1/8 inch.

    Measure the square feet of the surface and multiply that number by 1 lb for every 1/8 inch of laminate.
     
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