Custom 19' all weather, minimalist, strip plank composite 'go fast'

Discussion in 'Boat Design' started by socalspearit, Sep 2, 2021.

  1. fpjeepy05
    Joined: Jan 2010
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    Location: Hubert, NC

    fpjeepy05 Senior Member

    I'm not sold on the CF myself, but if you are doing it for the look I understand. Just remember CF is black and epoxy softens when it gets hot. Many a CF surfboards have melted in the sun.

    Hexcel makes a 9oz +/- 45 biaxle. That would provide fibers across all the strip joints. Personally, I would consider two layers, but I think one would definitely be better than 60oz woven.
    https://www.hexcel.com/user_area/content_media/raw/FGE198ST.pdf
     
  2. socalspearit
    Joined: Apr 2021
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    Location: Los Angeles, CA

    socalspearit Junior Member

    Good point on the heat. I don't think it will be an issue since the black CF is meant to be on the bottom of the boat at the waterline and it's intended to sit in the water, further cooling it, and it's a vertical surface but I am going to think on this and maybe run some tests. On the water, our air temps rarely touch mid 90'sF. My slip is actually quite shaded and at any time of the year never gets much direct sun.

    I will see how the hull feels when I finish but again, a 10" freeboard with laminated outwales and the beefy inwales on 1/2" red cedar hull is going to be very stiff. It would increase abrasion resistance but there is a law of diminishing returns in strength when you keep piling more fiber on. There is a good chart in the Gougeon book with different thicknesses of WRC and amounts and weights of fiberglass. On a hull that is entirely WRC (most common since it is so, so much easier from the joinery side) the added abrasion resistance given by every more layers of fiberglass would be helpful since WRC is soft enough to dent easily with a fingernail, but this build has white oak stem and keel, chine edges, and the back edges of the airboxes also, basically any surface which would within reason strike an object. Dunno how your waters are but we barely have trees here so no floating logs; I've put thousands of miles and hours into an inflatable over the last ten years and never run it into anything, or over anything.

    I'm doing some small vacuum pieces today to test the transducer through glass+CF before I make and patch the hole in my hull for the in hull transducer... kinda fun, I have done loads of vacuum and pressure casting for dive electronics but never much fiber work. I dunno, this is going well so I may think about doing a vacuum layup on the exterior instead of hand layup.
     
  3. fpjeepy05
    Joined: Jan 2010
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    Location: Hubert, NC

    fpjeepy05 Senior Member

    A single layer of 9oz biaxial would have three times the amount of fibers crossing your strip joints over the 60z and because it is stitched instead of woven I bet the resin used would be very similar.
     
    bajansailor and fallguy like this.
  4. socalspearit
    Joined: Apr 2021
    Posts: 64
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    Location: Los Angeles, CA

    socalspearit Junior Member

    Build update. I should finishing planking the hull this weekend. Shown here is the current state as well the scarf joints done as laps with 4.5" cheeks that some people commented on. All the scarfs joints are those type laps. There aren't really many since I was able to get 16' and 20' boards for the hull. You can also see some of the internal bulkheads around which I'm planking. It is still on the strong back but the hull is really solid, especially since a lot of internal structure is built in at this stage. Some of the planking a bit slow because I laid planks for both the sheerline and deckline to have guides for all that once I get to those stages, so there are more runouts to deal with.

    I got my fibers delivered. Exterior hull is going to be 6oz CF twill laid diagonal, covered by 6oz warp E glass laid transversely, with plain weave 6oz S glass laid straight. Most of the 'structural' elements is the wood and CF, the glass is just protection. I plan to lay the fibers on dry, wet them down, then vacuum bag it. Interior hull spaces will be sheathed in carbon fiber except for a some visible hull portions that will just be a few layers of S glass and finished bright.

    Next stage will be fairing the exterior, giving it a good coating of modified epoxy, then fiber.
    PXL_20220305_155425369.jpg PXL_20220305_155431098.jpg PXL_20220305_155545789.jpg PXL_20220305_155449320.jpg PXL_20220305_155418340.jpg
     
  5. socalspearit
    Joined: Apr 2021
    Posts: 64
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    Location: Los Angeles, CA

    socalspearit Junior Member

    fiber schedule:
    I started doing some tests of fibers adhered to epoxy coated western red cedar, in a vacuum bag. Wow, amazing. I was mainly testing how any seams would look... with 6oz cloth and vacuum pressure any overlapping seams basically disapear, especially after the weave is filled in. CF tape, since it has a more finished edge to resist fraying does leave a bit of a lump though. I am going to do a bit more testing to see if I can get something cosmetically perfect. I did three simultaneous layers, a Wood coated in expoxy -> 6oz warp E-glass -> 60z carbon twill -> 6oz S-glass... and I then I made some ridges and double layers of the exterior S-glass. I pulled too much vacuum too soon on the part vs prior panels I'd made so a little as expected the carbon under S-glass was a bit cloudy, which is how previous tests had looked when too much epoxy squeezed out of the fibers due to too much vacuum pressure too early. Okay for my purposes but I will do more tests. CF with nothing over it of course looks perfect but for the exterior hull I feel like a little S-glass on the outside would be a good idea.
     
  6. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Yes. A wee bit of glass will extend the boat life quite a lot. I have a cedar canoe 22 years old still going strong with epoxy and spar varnish with uv inhib.
     

  7. skaraborgcraft
    Joined: Dec 2020
    Posts: 32
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    Location: sweden

    skaraborgcraft Junior Member

    Has anyone mentioned that the carbon would be more effective on the inside of the boat as a laminate, rather than the outside?
     
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