New skiff - bottom with keel/rubbing strakes

Discussion in 'Boat Design' started by CaptChap, Sep 13, 2022.

  1. CaptChap
    Joined: Aug 2022
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    Location: Jonesport, ME

    CaptChap Junior Member

    This is the 18 ft. flat-bottom skiff I'm building. Just finished coating the bottom with epoxy/graphite, and next will prime & paint the topsides. The entire hull (outside) is sheathed in xynole/epoxy, with multiple layers on the keel & runners/strakes, before coating with the epoxy/graphite. This should be a tough, yet slippery bottom.

    Skiff Bottom - Better angle.jpg
     
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  2. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    I respectfully argue that Graphite content of the epoxy surface will not make the boat more slippery in the water. The smoothness and continuity of the wetted surface is a major determinant.

    Looks like a practical and useful boat. The picture suggests that it has some aft rocker which would imply a displacement boat. (could be only a quirk in the photo or my admittedly flawed perception.) Tell us more about your build and its intended purpose.
     
  3. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    The graphite is supposed to increase the abrasion resistance versus plain epoxy.

    No?
     
  4. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I'm wrong. Graphite in epoxy is softer.

    But it sure is pretty.
     
  5. mc_rash
    Joined: Aug 2020
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    Location: Netherlands

    mc_rash Senior Member

    I thought graphite is only used to turn epoxy black, correct me if I'm wrong.
    Still I like this boat, homebuild I guess? :)

    edit:
    A quick google search showed that graphite filler is used for low friction, bearing surfaces.
     
  6. CaptChap
    Joined: Aug 2022
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    Location: Jonesport, ME

    CaptChap Junior Member

    Correct...that is why I put it on; mainly for reduced wear on bottom from trailer loading and the occasional landings on gravel beaches.
     
  7. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Graphite is softer than epoxy.
     
  8. CaptChap
    Joined: Aug 2022
    Posts: 14
    Likes: 6, Points: 3
    Location: Jonesport, ME

    CaptChap Junior Member

    Thanks for your thoughtul comments.
    The intent was to add some abrasion protection on trailer loading and occasional beaching/grounding; plus, it just looks sexy and should last longer than plain old bottom paint (or any other paint), hopefully. Also, according to my limited research on the subject, graphite actually does not impart any additional hardness to plain epoxy, it just adds (supposedly) a lower cooeficient of friction. And you are right, academically, about super-smooth wetted surfaces increasing drag (parasitic?) to surfaces in flow, but I doubt that I'll notice any major drag due to its smoothness.

    And, you are right about the bottom contour; My design was for a slight rocker forward with a perfectly flat aft section, but what I ended up with does have a slight (3/4" or so) bit of aft rocker also. This may (slightly) affect the planing speed somewhat, depending on the amount of HP I push it with, but I'm not going to worry about it.

    As for my intent with this boat, I wanted a small, inexpensive to operate (i.e. hp range from 40-60 hp) skiff that I could easily build in my small garage/shop at my summer vacation home in Downeast Maine. Since the water up here (down here?) is cold even in the summertime, I decided to design a small lobster-style pilothouse for it, even though all the purist said it was a design sin to put a pilothouse on a hull that small. Next summer I hope to finish the project and launch her and see how she works.
     

    Attached Files:

  9. CaptChap
    Joined: Aug 2022
    Posts: 14
    Likes: 6, Points: 3
    Location: Jonesport, ME

    CaptChap Junior Member

    Second coat of EZPoxy topside paint done; next is the 2-1/2"wide white boot-stripe, then I'll flip her over and start on the internal framing & decks.
     

    Attached Files:


  10. CaptChap
    Joined: Aug 2022
    Posts: 14
    Likes: 6, Points: 3
    Location: Jonesport, ME

    CaptChap Junior Member

    BAR ISLAND SKIFF - Hull painted .jpg
    Finally finished the hull painting; many delays due to weather up here on the bold coast. The bow-on photo looks distorted due to the camera angle... she's really not as narrow as the shot makes it look.
    Now I'm getting ready to rig it to flip it over inside this tiny shop. Will have about 7/8" clearance when I rotate it. Will try to post pics of the flip (if I do it without any loss of life!)

    Hull painted 2.jpg
     
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