Scarf alingments?

Discussion in 'Wooden Boat Building and Restoration' started by BHOFM, Aug 20, 2008.

  1. BHOFM
    Joined: Jun 2008
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    BHOFM Senior Member

    We have started cutting parts for the boat!

    I have always tried to put the scarfs in the chine, sheers and
    stringers so they line with a frame member, thus having
    a fastener through them as well as being in a point of less
    bending!

    Does this make sense? Or am I overly cautious?
     
  2. WBC
    Joined: Aug 2008
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    WBC Junior Member

    I would say it is a good plan but then again I always over build. better to be safe than sorry ifin the sharks are out to bite
     
  3. BHOFM
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    BHOFM Senior Member

    We don't have a lot of sharks in Arkansas, well, not the
    water verity any how!
     
  4. WBC
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    WBC Junior Member

    what size craft are we talking about anyway. if it is say 20 ft I would just scarf 2-12ftr's close to midships. If it's longer, then I would just scarf as long as I could. If it works out on a frame, then right on score!
     
  5. BHOFM
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    BHOFM Senior Member

    I have a large cache of 1"X12"X12' rough sawn clear
    cedar! The boat is 16', 15'9" to be correct! It has three
    main frames equally spaced! In between each of these
    is a lighter frame, the main frames are 1 1/2X3 and the
    intermediate frames are 3/4X3!

    The original was built of solid planks with no frame! I am
    building a light weight frame and covering it with luan!

    I am hoping this will be a lighter build than the original!
    With 145sqf of sail on a 7/8th sloop rig, I hope it is a
    go'er!
     
  6. WBC
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    WBC Junior Member

    I hope your not talking about luan from your local home center...one scarf...good to go
     
  7. BHOFM
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    BHOFM Senior Member

    Yes?? The thicker frames are to allow butt joints of the
    skin rather than scarfs!

    it is a day use boat and will be stored inside a heated and
    air conditioned shop!
     
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    There are two different types of scarf, mechanical and bonded. A mechanical scarf is a perfect set of surfaces, fastened usually with shellac or varnish in the joint for good measure. Friction on the joint line and the fasteners keep thing together, moisture swelling the wood insures it's water tight. It's common to see this type of scarf on old school solid planking lapstrake, but it's not exclusive to them. It takes considerable practice to make one of these joints and expect it to hold water.

    With the advent of gap filling adhesives (epoxy) the bonded scarf has risen to prominence. These type of joints don't need fasteners at all, in fact, a fastener can cause a leak. A bonded scarf is stronger (and stiffer) then the surrounding wood, so making it land on a frame or in between, really doesn't matter in new construction. In a repair situation, the usual course is to have the repairs fall between frame bays, providing room to work on things.

    I would be very careful about what elements of the design you change. 145 sq. ft. of area on a boat with as short a LWL as you likely have (13'?), suggests this is a reasonably burdened hull shape. If you build it much lighter, that amount of sail area can easy be more then the boat can handle (read you'll capsize a lot, if you can keep the rig and crew in the boat).

    Lauan from the box stores is the weak kneed, red headed step child of 1/4" plywood, in comparson to marine ply. Other then design testing and disposable boats (read short life and easy to put a foot through when you step in it).

    Boats are shaped for their weight. If you reproduce a 1,500 pound boat, but it only weighs 1,000 pounds, she'll float high, requiring ballast. Of course you'll place some lead in the bilge and then the rig is strained beyond it's working limits, from the lowered CG. What exactly are you doing? I ask because you're substituting a very weak framing material (cedar) and using a very weak planking material (1/4" lauan), which is replacing heavy planking. Generally you use a heavy planking material and light (or none in your case) framing or light planking and closer spaced or heavier framing.
     
  9. BHOFM
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    BHOFM Senior Member

    Thank you for your time and interest in my project!

    I want a lively boat! We don't mind getting wet now and
    then!

    I am aware that the boat will be a bit delicate, I am used
    to that situation!

    I am keeping the proportions of the boat the same, going
    from 14 to just under 16'. I feel I have enough experience
    to build a suitable frame work that will be lite and strong!
    With a few pointers along the way from the great people
    here!

    I have looked at several scow designs and they all seem to
    have about the same proportions if it is 12 feet or 40!

    Here is the original design and the concept of what
    I want, the scale is feet!

    It will have a ballasted dagger board and the 145sqf
    is a wild guess at what the sails will come out, the
    cat rig on the 14 was 90!

    My scarfing jig I made will make perfect scarfs every time,
    in fact, I had one test fail because I over clamped and there
    was no glue in the joint. The router leaves a near mirror
    finish and I have to run over it with some 80grit to rough
    it up a little!

    Thanks again for your time with my crazy project!
     

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  10. WBC
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    WBC Junior Member

    All I can say is read what PAR says ..... he won't steer you wrong
     
  11. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    Best when there's no pattern at all regarding scarf alingnment. When using strips not more than 50% wider than thick it's also ok to but joint (except where tighter bending is needed)
    When using lighter and "weaker" timber you can increase the thickness to get closer to the original weight and strength.
     
  12. BHOFM
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    BHOFM Senior Member

    The main frames are laminated from 3/4 stock and
    mortise and tenon joined. The beam is 68" and the
    bow and stern are both 40 1/2" wide, the sides are
    13 1/4 wide, the transom is 9" high and the bow is
    4" so there is not much curve to any of it!

    The curve in the keel at the bow is 9 1/2" in 46"
    4" in 46" at the stern!

    This is a pretty flat boat! Several of the frames, fore and
    aft are bulkheads!

    It is not a boat you want to beach without some caution!

    Where we will be launching there are public docks, so
    we can paddle a short distance and rig the boat at
    a nice dock! It is not the ocean, it is a lake!

    I am also fitting the boat with oar locks!
     
  13. alan white
    Joined: Mar 2007
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    alan white Senior Member

    I'd be careful about a 145 sq ft sail area. My 15 footer has 155 but weighs like a Herreshoff 12 1/2 footer--- full keel with lead ballast.
    My plan, however, is to reduce the main to about 110. I've recently added a 30 sq ft jib and once the main is downsized, i'll add a 30 sq ft mizzen. That makes 170 total but with a lot of reefing options, and chiefly a choice between main only or jib and jigger, which is ideal, and even after that, a single reef with the main back up and I can handle anything that's thrown at me.
    The problem (and I'm now expreiencing this) is that sailing alone, 155 sq ft is a lot of sail to manage when it pipes up. Reefing a main is not as simple as striking a sail like a jib or a mizzen. What's at risk is your spars and sails.
    My feeling is, if you like a good ghoster (which mine definitely is), it's a good idea to work out a reliable and easy reefing schedule, one that can be handled in any condition alone.
    If you like a lot of canvas, and its a fractional sloop, make sure you've got a very good reefing setup.
    And if you use luan, boil a piece first and see what happens.

    Alan
     
  14. BHOFM
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    BHOFM Senior Member

    Thanks Alan, I will check it out!

    I can't find them now, but I came across a site with
    free plans and all the plans called for luan! And barn
    paint! They were really "building on a shoestring"!

    I have 60 years of sailing behind me, and have built
    some really crazy boats!

    I am not able to launch and setup by myself, so I will
    always have someone with me!

    And she is a big'n!
     

  15. alan white
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    alan white Senior Member

    You go for it, BH. But skip the barn paint!
     
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