big stitch-and-glue boat

Discussion in 'Wooden Boat Building and Restoration' started by Little Iris, Sep 2, 2007.

  1. Little Iris
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    Little Iris Junior Member

    Is it possible to build a 34 ft stitch-and-glue powerboat? Wouldn't it need stringers and so on to strengthen the hull? How thick would the hull has to be?

    Thanks,
     
  2. alan white
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    alan white Senior Member

    Any size boat could be built stitch and glue, I suppose. From a practical standpoint, it should be noted that maximizing the stitch and glue method means eliminating lofting. A larger boat such as 34 ft is going to be lofted anyway---- can you imagine patterns that big?
    A variant of stitch and glue would be a ply boat without chine logs, and to answer your question, there is no reason why epoxy/filler alone couldn't replace the chine logs and a lot of other framing as well. At a certain dimensional thickness, however, plywood is better fastened with screws or even bolts to pre-bent steel bar stock or wood blocks along the chines. Then, why not go a step further and have a solid wood chine log, which is a better means to line things up prior to hanging ply, allowing a means to scribe panels directly from the chine log curves--- remember, this ply isn't from a supplied pattern or picked up off the loft floor. It is probably rough-cut from a simple pattern made on the spot from a thinner ply and then trimmed to an exact fit along the chine logs.
    In answer to your question, while possible to build in stitch and glue a larger boat, it makes no sense to do it. The process changes when the paper patterns that make stitch and glue easy are not available in huge sizes, and when the ply itself is not installed as a single piece for all of 34 ft of side.
    Without an accurate pattern, chine logs become a faster way to get fair chines.
    Your question, how thick does the plywood have to be for a 34 ft boat, I think you will hear, at least 3/4", by building up two offset layers of 3/8" ply, e.g.. However, the scantlings of any boat relate to speed, displacement and intended usage. It is conceivable that a 34 ft boat might have a 2" thick plywood hull, or, if it were for example, an Azorian whaleboat, or a rowing gig, as thin as 1/2".

    Alan
     
  3. KnottyBuoyz
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    KnottyBuoyz Provocateur & Raconteur

  4. Pericles
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    Pericles Senior Member

    Sam Devlin published his book back in the nineties, in which he describes building stitch & glue boats up to 45 feet. http://www.devlinboat.com/dcsockeye45.htm

    He creates the basic hull in marine ply BS 1088, using a combination of double diagonal cold moulding where necessary and large shaped sheets of ply. He increases the thickness of the various parts of the hull to match the service conditions. The glass sheathing is for protection, less for structure and the hull is throughly encapsulated in epoxy.

    Permanent internal framing consists of transverse bulkheads and the use of seating and bunk flats etc., bonded to the hull as longitudinal strengtheners. The result is a vessel which is very strong and comparatively light. I like them.

    By combining Jacques Mertens jig building system, http://bateau2.com/content/view/71/28/
    epoxy resins, increased scantlings with cold moulding and S&G, you would have both accuracy and a rapid speed of build, eminently geared to the amateur boat builder who wants a seriously large boat. There are a number of very good books to start with at:

    https://www.boatdesigns.com/products.asp?dept=33

    http://www.devlinboat.com/

    http://www.parker-marine.com/parkerlivro.htm

    http://www.duckworksbbs.com/media/books.htm

    Good luck.


    Pericles
     
  5. Little Iris
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    Little Iris Junior Member

    Thank you all for taking time to answer my questions.
    I will start by building a small dinghy and then build my dreamboat!
     
  6. PAR
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    PAR Yacht Designer/Builder

    In large unsupported panels of plywood, you'll need stringers to transmit slamming loads (in powerboats especially) and eather bulkheads or a carefully positioned frame or three. Plus the unsupported areas will deflect under load (straining fasteners, glue lines and near by structural elements, if not breaking them), if no stringers are present and the panels have little torture in them. These areas are typically found in the topsides and the planning surfaces of a powerboat or aft run of a sailboat.

    I see a practical limit to stitch and glue, but taped seem may be able to grow larger, before similar issues of practicality arise.

    "Winging it' with the design and structural elements of a taped seam or stitch and glue craft, of large size is decidedly unwise. Scantling information needs to be processed and made accountable against many variables, of which the novice builder/designer must be aware. Dave Gerr's book, "Elements of Boat Strength" can be of great use in this regard, though a reasonable understanding of design and engineering structures, should be well absorbed before attempts at craft, of this displacement range are contemplated.
     
  7. Pericles
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    Pericles Senior Member

    Par,

    Agreed. Full length engine mount stringers plus outer stringers to internally support the hull bottom are essential, Jacques Mertens uses an egg crate style of transverse and longitudinal interlocked stringers epoxied in to support the hull bottom and sole as he favours lightish scantlings and foam cored cabin structures for his trailable boats and relies on biax tape and fabric for strength. Both Glen-L and Devlin Designs use thicker layers of marine ply for their craft as many of their vessels are larger. 2" hull bottoms and a little less for hull sides.

    Elsewhere in this forum I posted about power catamarans. Scroll down to see line drawings.

    http://www.alnmaritec.co.uk/downloads/Wave Angler.pdf

    I believe such hulls could be produced in epoxy ply composite form as a one off and deliver a very interesting motor cruiser. Then yesterday, the Slot Machine by Ken Hankinson popped up to confirm that idea to me. This boat

    http://glen-l.com/designs/hankinson/slotmachine.html

    and Cruise Missile are vacuum infused foam core built, but....?:D :D

    https://www.boatdesigns.com/products.asp?dept=734

    Regards,

    Pericles
     
  8. boatbuilder.org
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    boatbuilder.org Junior Member

    No you would not need stringers. The bulkheads should be placed no more than 4' to 5' apart with longitudinal bulkheads about 4' or 5' apart on each side of the keel. The hull thickness should be 1" to 1 1/4" on the bottom panels and 3/4" to 1" on the side panels. You would start with full length hull panels 1/2" thick and cold mold 8' sections of 1/4" plywood over that to get to whatever thickness you want. All interior joints (hull seams-bulkheads and longitudinals) should be glassed with a schedule of 4", 6" and 8" 12 oz biax with a layer or two of 6 oz cloth over that. 34' is no problem with stitch and glue
    ---Joel---
     
  9. alan white
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    alan white Senior Member

    I think a variant of stitch and glue can be used to produce a hull with frameless chines. Is that then stitch and glue, or something with some processes that are similar?
    I think the process changes when the panel shapes are taken from the molds rather than patterns. It changes also when multiple layers are added. The name of the process should also change in order to describe the actual process used.
    For example, the process described by Joel is more properly a conically-developed cold-moldied construction. Or, at least, not stitch and glue.
    This goes back to the beginning of this thread, when it was asked if stitch and glue could be used to build a 34 ft boat.
    I said it would be impractical, as did PAR------ meaning, stitch and glue as I understand the word to mean.

    Alan
     
  10. boatbuilder.org
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    boatbuilder.org Junior Member

    Here is a 45'er and all internal support ready for the panels to be stitched together.
    ---Joel---
     

    Attached Files:

  11. Pericles
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    Pericles Senior Member

    Joel,

    Good to have your advice. So, just engine mounts where necessary and transverse and longitudinal bulkheads. Thick bottom and hull sides by cold moulding additional layers onto the 1/2" panels draped over the temporary moulds and permanent transverse bulkheads and stitched, epoxied and taped together. When the time comes to roll the hull rightside up, without distortion, it's faired and finished and empty, just ready for internal glassing and fitting out.

    Alan,

    Rather than getting bogged down with conceptions of what is or is not S&G, should not we all realise that the pioneers of the new system contributed to evolving and promoting another method of building a boat in wood that does not require a long apprenticeship in steam bending frames, spiling planks, hand caulking seams and at the finish, have a traditionally constructed vessel that leaks like a sieve, :D and which then requires massive amounts of maintenance to keep it at sea.

    For those who do insist on using such skills, perhaps a look at Tenacious will offer a way forward.

    http://www.jst.org.uk/frames/index.php?pages=page1041

    To me, it makes most sense to cut the boat panels to size and shape in pairs, when they are flat on the floor, rather than build a framed boat and then cut the hull panels to fit, before positioning and fixing to the frame. The potential for a warped hull is greater if there are more components to the framed hull IMO.

    Time and tide wait for no man. I'd rather spent my time on passage rather than on the hard, figuratively trying to weld rusty air or hacking dry rot.

    Pericles
     
  12. alan white
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    alan white Senior Member

    How are those panels marked for cutting prior to hanging them? And are they pieced in or a single piece stem to stern?
     
  13. alan white
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    alan white Senior Member

    Little Iris had asked, in starting this thread, whether a 34 ft boat could be built using the stitch and glue method. Doesn't that depend on what exactly stitch and glue means to Little Iris? I think 90% of the questions on this forum are approached by those answering in the same way. The answer is meaningless unless the question is empirically understood to be the same for everyone.
    If someone had asked, "Is 13,450 about the right displacement for my hull?", imagine the answers. Pounds? Kilos? Empty? Fully loaded?
    So when you say, "...rather than getting bogged down with conceptions of what it means...", I would say, better to establish what the one asking meant, and to then align the respondant's concept WITH it, since it's obvious that each respondant is envisioning a slightly different process.

    Can I agree that modern building methods generally produce a more trouble-free hull structure? Yes, absolutely. I do think the amortized cost of any building process is what must be compared, however, especially regarding large vessels, since the "convenience factor" isn't the same for businesses as it is for people. It would need to be established that regular and proper hull maintainence on a plank and frame vessel would still not be more cost-effective long-term than if the hull were more expensively built using epoxy, etc., in the first place. We are accustomed to seeing planked wood hulls rotting and leaking because the oldest boats happen to always be planked.
    In fact, fiberglass at its best appears to have a far shorter lifespan than planked wood at its best. I do agree that so far, it appears that epoxy/wood composite has great potential for longevity. I don't know how that pans out when comparing the two processes side by side long term in a commercial vessel, but I suspect the epoxy composite is the winner. Yet, steel would likely be the very least expensive long term were it considered.

    A.
     
  14. boatbuilder.org
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    boatbuilder.org Junior Member

    Alan
    In the image you will see the hull panels cut out and laying on the floor. We just scarf up long sheets of plywood and loft them.

    Pericles
    None of the structure you see in the image is temporary. The bulkheads are placed to become part of the cabinetry and interior structure. They are not set up at random, but are placed in specific locations. Before roll-over I do glass on the inside. Just about everything but the overhead work, that waits til after roll over. I also add a strip of 12 oz biax on all exterior joints between each layer of 1/4" plywood.
    ---Joel---
     

  15. Pericles
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    Pericles Senior Member

    Alan,

    You are right that S & G means different things to different people. You used the term epoxy wood composite, which is exactly the description I use.

    Rather than "Precut, developed marine ply panels, framelessly sutured, strongback supported, jig mounted, taped, filleted, glassed, fully epoxy encapsulated, sheer clamped, transverse & longitudinal bulkhead strengthened, monocoque construction", or PDMPPFSSSJMTFGFEESCT&LBSMC for short. ;)

    For many (like me) to build a large boat without the necessary skills involved in traditional boatbuilding, we would still be standing on the shore, if it were not for those farsighted designers and builders who pioneered their methods and ideas, so that we can now build a better boat than we can buy. I'd love to be able to purchase a Vicem 54, but something along the lines of a DE25 will have to suffice for now. http://www.bateau.com/studyplans/DE25Cabin_study.htm?prod=DE25Cabin

    Joel,

    Your website is inspirational. Any updates for us?

    Regards to you both,

    Pericles
     
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