Fairinig carvel planked hull

Discussion in 'Wooden Boat Building and Restoration' started by wonderfulworm, Oct 13, 2009.

  1. wonderfulworm
    Joined: Oct 2009
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    wonderfulworm Junior Member

    Hi, help please...

    A few weeks ago I spent the best part of a week "fairing" about 600ft of newly-fitted larch topside planking.

    Using 5 inch plane I planed diagonally across the planks in both directions to take off the high spots and finished with an orbital sander. The job was pretty damn good, even if I say so myself and with a good weeks work under my belt I left the hull as it was and moved onto repairing an old bodge someone had perfomed on the transom and fitted couple of transom planks..

    With the transom finished I moved onto the rubbing strakes and noticed the once very smooth and evenly faired hull was all over the place!

    The only thing I can think of is the planks have swollen / shrank due to the changes in weather over the last few weeks.. it was pretty hot and consistantly dry when ther hull was faired and in the last couple of weeks the temperature has really taken a drop and we have had a lot of rain.. The boat is on hardstanding outside so exposed to the elements...

    What should I do?

    Suggestions please

    Many thanks
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The orbital sander over a soft wood might have done it. Are you sure that the difference in perspective or light is not what is letting you see the defects now? Use a long batten with chalk to mark the high spots and plane or scrape them down.
     
  3. dskira

    dskira Previous Member

    Depending the type of hull, you can just leave it alone, paint with a sating flat paint, not glossy. Try some king of off white or eggshelf.
    Enjoy the season, and when the boat is stabilized, you can reconsider. I am afraid fairing to much will loose some planking thickness. but all that depend also the thickness you have.
    Personaly I don't like a hull to much fairerd and glossy, I like to see the work of the man in every plank. But this is my own view!
    Cheers
    Daniel
     
  4. wonderfulworm
    Joined: Oct 2009
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    wonderfulworm Junior Member

    I'm afraid it is much more than this... the new planks have swollen at different rates... some of the planks are now considerably thicker than others (around 2mm difference). It really looks like it hasn't been done at all... will try and get a photo sorted today of immediately after fairing when nice an smooth and its current state... looks bad! by the way the old planks have not budged a jot and are still evenly faired... The new planks range between 30mm and 35mm.... This was the size of the old planks adjacent to each new plank location... thanks guys... will check in later after the days work on the boat and get some images posted... Tom...
     
  5. gonzo
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    gonzo Senior Member

    Are the planks still tight to the frames?
     
  6. alan white
    Joined: Mar 2007
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    alan white Senior Member

    Shrinkage and expansion will differ between adjacent planks if the planks vary in grain orientation, from flats-sawn to quarter-sawn. The difference can be as great as double.
    Assuming all of the planks had approximately the same original moisture content, only grain orientation could be the culprit. This is assuming each plank lies against its frames. Much uneveness can be caused by cupping of some planks with growth rings concave to the outside surface that are expanding outward at their edges. You could have multiple causes, in other words, but all due to grain orientation.
    If the planks were all carefully chosen from quarter-sawn stock, I am wrong, but I'm guessing the wood is mixed, and mostly flat-sawn.
    You have no choice but to re-fair and prime soon thereafter to prevent rapid moisture changes within the wood. It'll be okay, but quarter-sawn wood makes the best planking stock and it will always shrink and expand less than flat-sawn.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Bingo Alan. I'd also add it would be very difficult to truly fair a hull with a 5" plane. An orbital isn't going to do much either, except smooth over the waviness a touch. I suspect the new planks are flat sawn and the old ones proper quarter sawn stock.
     
  8. wonderfulworm
    Joined: Oct 2009
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    wonderfulworm Junior Member

    Hi Guys,

    The planks are all copper roved and are still tight to the oak frames.. The Larch used was bought in butts from a sawmill in Scotland and was indeed flat sawn. The two butts used were purchased at seperate times though, roughly 6-8 months apart but they were from the same supplier and I was told from the same batch..

    The problem is not one of random high spots along the length of the planks, it's where individual planks have swollen at different rates (i.e. each whole plank has swelled equally and the difference between the planks is uniform along its entire length). The planks are of course all of different lengths ranging from 12ft to 35ft and range from around 30mm to 38mm in thickness dependent on the size of the old planks adjacent.

    The two additional days of rain we've had since my last post have made some difference and the planks are more even again.. that is all bar 1 plank! I would love to be able to say that this particular plank is by far the longest and thickest on the boat but this is simply not the case... Only thing I can think of is, it might have been taken from closer to either the heartwood or the sap and just swelling much slower that the others??

    Another point to consider maybe... The planks are not receiving the same quantity of rain/weather either.. the boat has no deck and the wheelhouse and aft-cabin are yet to be constructed..

    From amidships to stern has been left exposed (6.5m) and the bow (8m) has been covered with a tarp which pulls down to a couple of planks above the waterline each side.. The planks below the tarp have received a small amount of water through condensation.

    To keep the exposed hull and below the waterline thoughout nice and tight sheets of ply have been used as a temporary floor to prevent sun damage and around 8 inches of water have also been held in the bilge allowing the lower old planks to pull up water (*only topside planks replaced). The planks above the waterline have also been sprayed from the inside with water for a couple of hours every fortnight allowing the water to run into the bilge replacing any lost through evapouration and capillary action up the planks etc..

    For the time being I'm going to wait a while longer and see what happens before looking at again... By the time I get the deck on we will no doubt have had more rain and hopefully the 'problem' plank will have sorted its self out..

    In the meantime any thoughts are welcome though..
     

  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Quarter sawn lumber is the usual choice for planking, simply because it doesn't move nearly as much as flat sawn. Moisture gain in flat sawn material can be dramatic as you've seen.

    The planking will adopt a natural balance with the environment surrounding them. Of course immersed is one thing, but on the hard they'll take up for a few weeks, then acclimate to the general humidity, rain, no rain, etc. isn't especially relevant after this.
     
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