Sloop hull construction

Discussion in 'Wooden Boat Building and Restoration' started by midiman, Jan 5, 2010.

  1. midiman
    Joined: Jun 2007
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    midiman Junior Member

    After finishing my last restoration project (http://www.woodboatblog.com/blog.php?ARTICLE_NR=100) I have my radar out for an upgraded project. I got a set of plans for a 24 foot bluenose sloop.

    http://joelro.com/snyders07/project_bluenose_sloop.html

    The plans are for a traditional strip planking hull. I was spinning some thoughts and would like some feedback to find the perfect balance that will make this project a floating success. Please keep in mind that I have a mechanical engineering degree and advances carpentry skills but this is a "hobby" project.

    A. How would cold molding vs strip planking impact the frame design?

    B. What is the difference in terms of maintenance (cost, time) between strip planked and cold molded hull?

    C. Any other thoughts on cold molding the above design?

    D. Caulking the planking with cotton seems very pure but not very effective in terms of maintenance. I there a modern method for better durability?

    E. What is the fastest (and cheapest) setup in terms of tools to shape planks? I already have table saw, planer, electrical hand planer, bench top band saw.

    Thanks

    midiman
     
  2. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    I would go with cold molding and make the 1st layer plywood and the top layer out of a hardwood if you want a bright finish. Cold molding goes quite fast and is waterproof and you have all the tools you need. Why would you want to caulk?
     
  3. DavidJ
    Joined: Jun 2004
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    DavidJ Senior Member

    I doubt the plans for a boat designed in 1948 used strip planking. Those build pictures show somebody doing what I would refer to as carvel planking. In that type of building the wood is exposed and therefore is expected to soak up water and the cotton caulking helps seal the hull.

    Cotton caulking is not required when using modern "sealed" wood methods such as strip planking or cold molding.


    Here is a quick summary of some planking methods by the designer Paul Gartside.
    http://www.gartsideboats.com/faq2.php
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Strip planking and typical cold molding use different engineering principles then carvel construction (what Bluenose is). With both strip plank (depending on the actual method employed, as there are many) and molded hulls, you can develop a fully monocoque hull shell, devoid of bent frames and stringers. This is a far cry from the structural frame work of the carvel, so you'll need to convert the plans to your desired method (best done professionally).

    Maintenance of a carvel is fairly high compared to both strip plank and molded builds. With the exception of traditional strip planking, both methods will have low maintenance requirements.

    Cold molding isn't the easiest building method, especially compared to strip planking, which is possibly the most user friendly method for the novice builder.

    Strip planking is easily the cheapest to set up. You just rip the strips, edge dress them if you want (cove and bead is common, though not necessary) and start planking over the station molds. It's a bit tedious as the strips are narrow, but still is faster the molding a hull.

    Molding a hull, except for Ashcroft method, requires you cut, fit and attach each plank, then once you've covered the hull, you do it again for each layer of veneer you need. This means you have to plank the hull at least twice, usually more. Ashcroft method is also a molded method, but the planks run the same direction and can be placed at the same time, so when you've planked the hull, you don't have to go back and do it again.

    You can also mix the two methods, which is often done so you can have varnished normal width planks on the outside. You'd strip plank the hull normally, then apply a single veneer of fore and aft oriented planking. Of course this is visible so you have to work especially neat, where you don't with other methods (the joy of putty).
     
  5. bertho
    Joined: Aug 2006
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    Location: asean archipelago

    bertho bertho

    hi,
    log on my on-going 50' project,
    picts even better than long explanation ! :D
    modern mothod and epoxy make the thinks more easy..don't miss it ! fully agreed with PAR ! not always complicated to do simple !!
    www.fusionschooner.blogspot.com
    cheer's:)
     
  6. midiman
    Joined: Jun 2007
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    midiman Junior Member

    Thanks for all these great thoughts and links.

    So I conclude that unless I want to alter the design cold molding is out. Additionally the original carvel construction is very high in maintenance. Just about where lapstrake would be.

    How would a hybrid construction? Double planked like here? Any concerns or gotchas?

    http://www.gartsideboats.com/jessie.php

    tnx
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I can understand why you want to avoid carvel. You have two good options, one is to find a design in a method more suited to your needs and the other is to have the plans you have converted.

    Paul Gartside's double plank method isn't a hybrid, it jut a very old planking method. Plank fitting is still difficult (rolling bevels, spiling, etc.), you have to plank the boat twice and it tends to be heavier then more modern methods. Besides, he's an ill informed jerk and I wouldn't patronize anything he does, but that's just me.

    Maintenance on glued lapstrake is very low. Maintenance on traditional lapstrake is also low, compared to carvel. Lapstrake is one of the best methods you can use for small craft. It's very light (always a good thing), naturally strong and if glued lap, absolutely water tight. Besides there's nothing that looks better too.

    In this size range, there are literally thousands of designs to choose from or you can convert. A lot depends on how much you're in love with Bluenose (which would look great as a lapstrake). Of course boats with these lines will tend to be older plan sets, so modern building methods may not be used. There are some modern plans that use hull shapes like this, but they will be fewer and harder to find.

    I'd recommend a conversion. The cost of plans and the conversion are a drop in the bucket compared to the total for the project, so it's a minor consideration in the big picture.

    The pictures of Bluenose being built show carvel construction, but you mention the plans show traditional strip plank as the method. Which is it?
     
  8. tkk
    Joined: Jul 2009
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    tkk Junior Member

    This is clinker originally and about your size:

    [​IMG]
     
  9. midiman
    Joined: Jun 2007
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    midiman Junior Member

    PAR. The plans I have are for carvel design. So unless I find an other very similar design they will have to be converted. As you mentioned I did search for modern plans with similar lines but had no luck in under 30'. And even then most of them had very deep bulb keels limiting the use in shallow waters.

    The bluenose has a projected 3'8" draft. 750 pounds of led in the keel and I simply love the clean lines. So what conversion would you suggest considering I am just building one hull mostly working by my self?
     

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

    3'8" isn't shallow draft, unless it's a centerboard fully down.

    As for the type of build method, that's a decision you'll have to debate with yourself. The easiest way is to make lists of the things you feel comfortable about, tools you have or might need, skill set(s) etc. One of the strip planking methods is a usual choice for the novice builder. Glued lapstrake is another option if you can get past the mental barrier of the separate planks. It's also the lightest of all the "usual suspects" for method choices.

    Personally, I think the design is screaming to be a glued lap build, but a lot of people wrongly think this is a difficult method. Yes, some elements of it aren't as easy as laying hundreds of glue coated strips against each other, but these aren't difficult skills to get a handle on. Lining off a hull for example is quite easy and enjoyable. You may end up playing with battens all day, to get it looking just right, but it's easy work. The same can be said of spiling a plank. If you elect to go this method there are a few of good books on the method. I'd recommend "How to Build Glued Lapstrake Wooden Boats" by John Brooks. I use slightly different methods, but his work fine too.

    A somewhat heavier, a little easier, but more tedious method is strip planking. There are several different types, some being little more then narrow plank carvel, with frames and stuff, while the other end of the strip plank spectrum is 'glass construction with a wooden strip core, with several in between, spanning the differences. Again most novices like the idea of strip planking, but in all honesty building the hull shell is a fairly small portion of the over all effort and cost on a build this size, so value the build method accordingly.
     
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