leveling an unfinished hull

Discussion in 'Boatbuilding' started by bluemarble, Jul 31, 2006.

  1. bluemarble
    Joined: May 2006
    Posts: 13
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    Location: Concord NH, USA

    bluemarble 40' Wooden Spray

    I have a 40’ Bruce Roberts Spray. It is a strip plank hull that is not finished yet. It is only a keel and 7/8 of a hull. Another man had started it about 20 years ago and never finished. I took the hull off of his hands and I am going to finish her.

    My problem is this:
    The molds have warped worse than a signpost during Hurricane Katrina. I can’t figure out where the headstock line is supposed to go and therefore I am having a hell of a time trying to level this boat. I can’t find a decent reference point to measure from. I think that I am level fore and aft, but side to side I can’t even tell if I am close. The strip planking has been built up slightly more on one side and it is messing with my visual assessments of “Level”. I recently bought a self-leveling laser level that projects a red level line spread out across 90 degrees. I think this may help me keep a straight line, but I don’t think it will help me figure out which way to tip the boat. I have also strung a plumb line down the center of the transom so that it drops below the keel and I have stepped back to see if I can see if it is parallel with the keel. (it seems to be plumb)

    I am fairly sure that fore to aft I am within 1” over the entire 40 feet of the boat. Side to side I think I am within 1” over 14 feet of beam. Is this acceptable? What would be noticeable to someone that didn’t know the boat was slightly out of level when she was built?

    As I was writing this I think I came up with a solution. I will use the laser level (it also has a laser plumb line) to project a plumb line down the keel (from the inside of the boat) and up the bow along the centerline. If my plumb line stays straight along the center line all the way up the bow I should be level. What do you guys think? Should this work? Does anyone who has done this before have any words of wisdom?

    Thanks for the help,
    Matt
     
  2. SeaSpark
    Joined: Mar 2006
    Posts: 593
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    Location: Holland

    SeaSpark -

    curious

    Just out of curiosity, is this the boat you are talking about?

    http://boatdesign.net/forums/showthread.php?t=10630

    If so the previous owner posted some threads on it:

    http://boatdesign.net/forums/showthread.php?t=10274
    http://boatdesign.net/forums/showthread.php?t=10277
    http://boatdesign.net/forums/showthread.php?t=10364
    http://boatdesign.net/forums/showthread.php?t=10537
    http://boatdesign.net/forums/showthread.php?t=10631

    About your question:

    Im am not a real expert on this subject but i think the 1" tolerance over lenght and beam is acceptable. No profesional boatbuilder would tolerate it in his new build boat but many old wooden ships have "sagged" way beyond 1" in their shape and are still perfectly useable. On a race boat an asymetric hull is not tolerated for performance issues, with a design like the Spray the effect will not be noticable.

    Good luck with your project!

    edit:

    Found the answer to my curiosity, it is the same boat, good thing you are saving it!

    From your post http://boatdesign.net/forums/showthread.php?p=96359#post96359

     
  3. SeaSpark
    Joined: Mar 2006
    Posts: 593
    Likes: 17, Points: 0, Legacy Rep: 96
    Location: Holland

    SeaSpark -

    Pilothouse

    Hoi Matt,

    Just had a look at your (good looking) website , are you planning to build the Brian Daigle pilothouse? It looks huge compared to the versions Bruce Roberts originally has drawn. A pilothouse this size will have a great effect on sailing performance and stability. The added weight will put bigger loads on the hull, in your case a 20 year old wooden one.

    If you do want to build a pilothouse this size i would recommend you seek assistance from a qualified naval architect.
     
  4. mobjack68
    Joined: Jul 2006
    Posts: 25
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    Location: Western East Virginia

    mobjack68 Junior Member

    Hey Matt, just a thought. You mention the molds have "lost their shape", my guess is that line drawings are possibly still available?? I would suggest re-making the molds and attaching them alongside the existing molds...this would allow you to adjust everything else based on "new" more true lines???
    mobjack68
     
  5. bluemarble
    Joined: May 2006
    Posts: 13
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    Location: Concord NH, USA

    bluemarble 40' Wooden Spray

    Hello All,

    Seaspark - Yes Brian did design that drawing on my web site. It was the only drawing I had when I had started the site. I haven't updated it in a couple of months. I am, however, planning on building the ship according to the Bruce Roberts designs. I am not a naval architect, so I'll stick with something that has been tried and true.
    Do you know of any ships that have been reworked while they were not-perfectly-level? Are there any other reasons besides aesthetics ones where I would want to be more precise?

    My plan is once I am satisfied with the levelness of the boat I will redraw the headstock line and continue the construction using this as my reference point. The worst case senario that I can think of is my hull may not be built up to the right point on either end of the ship, but it should be very close if I have leveled the boat well.
    Is there anything else that I should be concerned with that I am overlooking?


    mobjack68 - I don't have the full scale drawings. I do have the original plans that have been left out in the rain for about 30 days during their lives. the existing molds seem like the best reference for me. The curve of the molds has not changed only the way they sit in the ship. They have lifted up and slid forward or backward and I don't know where they are supposed to be. I am going to remove the molds and copy the curve onto stanchions then continue to build up the hull using the stanchions as my new mold. I only have 10-12 more inches of hull left to lay down.

    Once the boat is level I will use a laser level that I'll mount on a tripod in the center of the boat to project the headstock line around the boat. This headstock line will have been previously marked on every stanchion during my mold-copying process. I will attach all the stantions to the hull making sure my marked headstock line matches up with my laser line. this should be a fairly acurate way to preserve the original lines.
    I do have plans for the height of the deck and the rail, so I'll just measure up from my headstock line on each stanchion.

    I've probably confused everyone. Even myself. I'll let you guys know how it goes. I am going to work on her tonight.

    thanks for everyones input,
    -Matt
     
  6. mobjack68
    Joined: Jul 2006
    Posts: 25
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    Location: Western East Virginia

    mobjack68 Junior Member

    STRING...lots of string!!

    Hey Matt, don't forget your stringline. If you pull a line bow to midline stern, you can tie off of the midline with more line to the c/l of the ribs, you can square these as you go (stem to stern/port and stbd) and then use a plumb bob to check the location of the ribs along the side and down into the hull. This is of course totally dependent on the hull sitting as level as possible to start with (using the plumb bob that is) If the rib lines are square w/the midline, you can tell also if the ribs are offset front to back. You can also measure the length of the lines port/stbd to check for fair along the sheer... is this about as muddy as hurricane water??
    Good luck..
    mobjack68
     

  7. bluemarble
    Joined: May 2006
    Posts: 13
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    Location: Concord NH, USA

    bluemarble 40' Wooden Spray

    I can finally say (and feel comfortable) that the boat is level

    Thanks mobjack. That is a really good idea. It sounds way more accurate than using the traditional line levels (with the bubble) that I was originally using. I figured out another way last night - I hung two strings line @ the center line of the boat from the top of the transom down to the ground and from the top of the bow stem down to the ground. I took my new laser-level-thingy and had it project a plumb line directly on one of the strings that I hade hanging. I made sure to be right in line with the c/l of the boat and when I swiveled the laser line just a hair the laser line moved off of the string that was hanging and onto the boat. I inspected the front and rear of the ship this way and it turns out that at the highest points on either end of the ship I am about ¼” away from level. So I think I am going to be happy with that. Mobjack I think your method would be more accurate than my method because I lost a little accuracy when I lined the laser up with my external plumb bob and the centerline. If I was just slightly off to one side and not directly in a straight line from the c/l through the plumb bob my laser would project it’s plumb line slightly crooked along the surface of the boat because it is not flat. But it saved me time and was accurate enough that I am satisfied with my leveling job.
     

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