fairing a 30 foot bright hull

Discussion in 'Materials' started by H A van Nes, Feb 15, 2015.

  1. H A van Nes
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    H A van Nes designer builder sailor

    What's the best way to fair the wood for hull that will be all varnished as for a classic runabout. Can one use an air driven in line sander as often used in auto body work?
     
  2. gonzo
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    gonzo Senior Member

    You could use it for the initial rough work. If you want a really fine finish, a scraper is the right tool. Sandpaper has to be used only along the grain. Orbital sanders won't give you a showroom finish.
     
  3. redreuben
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    redreuben redreuben

    At what state is the hull in now ? Has it or will it be sheathed ?
     
  4. redreuben
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    redreuben redreuben

    Ok, saw the other thread.
    If the hull is just planked start with the longest plane you can find and work your way down to fine paper on longboards. Keep the power tools well away, the only thing they do faster is make mistakes.
     
  5. H A van Nes
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    H A van Nes designer builder sailor

    Thanks redreuben. The hull is actually 11 years old with six seasons on the Hudson near Ossining and 5 separate spread out years on the hard. I am now using a log board. I guess there is no easier way.
     
  6. PAR
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    PAR Yacht Designer/Builder

    Fairing is a bit of an art form and to really get a fine finish, you plane it down, then sand it smooth and finely, you scrape the surface to cut, rather than tear the end of the wood fibers, which allows any finish to get a much better grip on it. To see how this works, simply take a hunk of wood and sand it with whatever you want, 220, 340, whatever and along side a portion of this sanded area, use a cabinet scraper. Varnish both areas at the same time and see the difference. Before you apply the varnish, you'll note the difference, but once the varnish is applied it's more obvious. After the varnish is applied, wet sand and polish it (of course after it's well dry) and a much bigger difference will be seen. On the other hand you can skip all this an just go to a boat show. A regular varnish job will look like a redheaded step child, next to a scraped and buffed varnish job and it's easy to see in bright light.
     
  7. SukiSolo
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    SukiSolo Senior Member

    Completely second PAR. Also worth noting that some timbers really reward using the scraper, especially stuff like Holly. You can just feel the difference with your fingers, it's like silk compared to rough wool almost. The scraper actually 'cuts' rather than being rough and removes any very fine scratching from even fine sand paper. Expect to have to resharpen the scraper a bit though as it will blunt, because it's edge will be damaged by fine particles of abrasive left on the wood surface.

    On the plus side, it does not usually take too much work to refine a faired surface if it has been done with fine/very fine grit paper. Too coarse and it is a different matter....;)
     
  8. H A van Nes
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    H A van Nes designer builder sailor

    thanks guys: I know scrapers are used on fine violins but never thought of it for the boat. Actually when I first launched the boat looked great. I shaded down to 120 then applied CEPES then light scotch bright followed by 5 coats of high UV protected Polyurethane. Four years later I lightly sanded and applied 2 coats of spar varnish and it looked good. Now its 9 years later with a few wear and tear bumps and scratches and bigger ones from Hurricane Sandy.
     
  9. H A van Nes
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    H A van Nes designer builder sailor

    All finish is now off and I'm working on getting her FAIR to an 80 grit level. Once there I think I'll be fine. It's on getting to that degree of fairness that I'm looking for help. I'll post some pictures if I can figure out how on this website.
     
  10. gonzo
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    gonzo Senior Member

    Fairness is what the overall lines/curves of a boat are. Smoothness is the degree of surface roughness.
     
  11. PAR
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    PAR Yacht Designer/Builder

    Fairness is what you can see with your eyes, while smooth is what your hand's feel. There's a huge difference between the two. For example, a big dent in a car door is clearly unfair, but if freshly polished and waxed, can be quite smooth.
     
  12. TANSL
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    TANSL Senior Member

    PAR, good definition and enlightening example. Now I understand.
     
  13. redreuben
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    redreuben redreuben

    My method is to imagine the water flowing around the hull and sand at plus/minus 45 to those lines.
     
  14. PAR
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    PAR Yacht Designer/Builder

    Fairing a hull at angles is standard practice, but the angles are dependent on the shape(s) you're sanding, not the flow lines.
     

  15. gregkuiper
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    gregkuiper Junior Member

    I can see using an electric planer for the initial rough work, but definitely hand tools once you get the edges knocked down. The cheap little Ryobi planer that I use planes in increments of 32's so you don't worry about taking off too much material if you are careful.
     
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