Tite Bond glue for a 27' strip plank hull?

Discussion in 'Boatbuilding' started by Thomas Wick, Apr 15, 2007.

  1. Roly
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    Roly Senior Member

    I can relate to that intuitive thing. I am re-engineering my boat in terms of his construction. Strip plank on frames to strip plank with only minimum bulkheads & ring frames, sheathed inside & out with uni,biax,& triax. I was told by experts he was kindling. But my gut feel was his, (its a "he") life was just beginning.:)
    I have increased beam to the correct offset,increased LOA, length to max tolerance under class rules plus a liitle in the topsides.Shedding wt all the way. I have yet to optimise the keel.So far things are going well, except for the budget.People think I have "lost" it.I want this boat to sail to its rating.(Or better)
     
    Last edited: Apr 19, 2007
  2. frosh
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    frosh Senior Member

    Hi Tom, going back to your original post, re using a lesser product than epoxy glue to join cedar strip planking. I am sure that this is fine as long as you have thoroughly sealed and reinforced both inside and outside surfaces of the hull skin. If you are going to epoxy coat the interior surface why not add one layer of double bias glass. Cost is fairly low for this material, additional weight not significant on a 27' hull. The results will be well worth it for a huge increase in the inherent weak cross grain strength of the timber, and general hull stiffness, water resistance, and durability.
    As far as designing as you go, I often do this as well, but I am working on my tenth boat. The first few all came from proven plans. If this is your first boat project, then you are taking a risk that all the money and time you are putting in could be sunk eventually. And you might not find out until after launching. Best case scenario is that your creation sails reasonably well but has a very low re-sale value. This is not to denigrate you, just making you aware that unless you have sufficient design and build experience there are big risks. Good luck anyway!
     
  3. northerncat
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    northerncat Senior Member

    i would put some kind of glass on the inside as this is what actually gives you the strength unless of course your are using some kind of tongue and groove strip to interlock your strips together mechanically
    sean
     
  4. PAR
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    PAR Yacht Designer/Builder

    TiteBond (original) is a standard yellow wood glue and has a very limited use on a boat, none on a hull. TiteBond II is a type 2 adhesive and is water resistant and will fail after a short soaking in water. TiteBond III is a type 1 adhesive and will tolerate that test for water proofing, but again will fail in long term or continuous emersion. None of these three products are a structural adhesive, so unless your structure is relying heavily on strip edge fasteners and shell to framing fasteners, you'd be best advised to use a structural adhesive. This is one reason epoxy is commonly used in this application. It's physical properties can permit skipping the edge fasteners all together and forms a natural base for a sheathing, be that veneer or fabric. Keeping the strips in solid contact with each other is paramount.
     
  5. Thomas Wick
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    Thomas Wick Junior Member

    Western Red Cedar vs Port Orford Cedar?

    I would just like to thank you guys for all the info so far...building as I go and of course, the glue question. I will use epoxy to joint the planks after reading the posts. I was reluctant to cover the inside of the boat with biax as I read an article in the Wooden Boat Magazine that made me think I was deviating to far away from a true wooden boat. If I glassed both the inside and outside of the boat.. you really have a wood cored composite hull.
    I would like the natural look of the wood on the inside of the boat, making biax a NO option. I question just how much strength you gain from covering the interior of the hull with a light weight cloth, that would be transparent when coated, which of course is an option. Your thoughts would be appreciated.

    Thomas
     
  6. frosh
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    frosh Senior Member

    Hi Tom, you comment that by putting a decent thickness layer of biax over the inside of your strip planked 27' hull you get a wood cored composite structure. It sounds like you want a true wooden craft. Using strip planking of a lightweight timber such as western red cedar is a perfect core for a composite hull of this size. A thin layer of woven glass works well for a canoe that has very small loads relative to your proposed boat. I suggest you read the thread by Eric Sponberg NA on using minimal reinforcement in composite laminations. http://boatdesign.net/forums/showthread.php?t=16573
    You need to ask yourself if you are well enough equiped to design and build a boat of this size. A forum like this is good for advice but it cannot function as a complete design service.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Strip construction comes in several varieties, composite is one of them. You can't change mid stream from one to another. If your plans call for an inner and out sheathing, then it's very likely that this is part of the "laminate" schedule and contributes significantly to the strength of the hull. If they're calling for biax in the plans, then you can rest assured it is part of the scantlings for the vessel. Biax adds tremendously to the stiffness of the structure, as well as providing considerable increase in puncture resistance.

    Most often strip construction sheaths the strips to prevent print trough at the very least (the tendency for the strip seams to show through with age). Since this is an issue with striped hulls, most designers take advantage of this and use a sheathing, which can decrease strip dimensions and overall hull weight, if carefully engineered.

    Engineering "on the fly" has it's attributes, but is best applied to small pieces or individual problem solving. Winging yacht design on this scale isn't wise, though can be done. Successful attempts are usually with years of building experience or patterned after well established hull forms. I personally know of a fine builder, that builds by eye only, but he's been a builder for 50 years, his father taught him the technique that his father taught him. All the hulls are the same type, but dimensionally to the clients needs. Hookers where built this way (and still are), but it's not a recommended practice for the first time builder, without a master to nurse you along.

    Good luck with your project. Post some pictures so we can see how you've faired., For what it's worth, even the holy brothers over at WoodenBoat have to admit that a hull that is 51% wood is considered a wooden boat. A wood cored boat is a lot more then 51%, so fear not, it's wooden. If you have difficulties at times buying into this, release some termites into the bilge and see what happens.
     
  8. alan white
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    alan white Senior Member

    I'd have to agree, especially regarding inner tensile skin strength, which is orders of magnitude stronger than epoxy alone. the only way to substitute for glass inside would be close framing. The framing would serve not so much to stiffen the hull at rest, but to resist deformation and cracking under stress.
    The hull without some means of inner (vertical) tensile reinforcement (especially in flattish areas such as upper bow sections) is very fragile indeed.
    For instance, such a boat could be badly damaged from a relatively minor impact to the bow topsides, flat stern undersides, or elsewhere depending on design. Even the pounding of a fist.
    Some excellent strip-build schedules are used to construct multi-hulls like Chris White's 40' Skyhook design, which uses structural bulkheads at maybe 6-7 ft spacing, maximum maybe 4 ft vertical spans unsupported (by structural shelves, furnishings, etc.), and displaces about 8000 lbs., similar to a 27' monohull.
    The Skyhook design calls for 1/2" red cedar strips, epoxy-glued, with glass inside and out, finishing out to about 5/8" thick.
    Such a schedule would make for a pretty light 27' monohull, maybe suitable for a 4000-5000 lb boat, which is pretty light.

    Alan
     
  9. northerncat
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    northerncat Senior Member

    the inner skin bonds to all the strip giving it great strength, without it as said earlier you can just about punch some serious damage into a hull
    sean
     
  10. Roly
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    Roly Senior Member

    It surprises me that NA's stipulate less glass in internal sheathing than external. Dave Gerr -- 66% of external. Tom Macnaughton --equal.

    I guess both faces alternate in compression and tension as the mass of the
    hull & keel cycle thru negative and positive G's. And the force of the mast
    on the floors, & the rigging onto the chainplates. To me, the ideal way of spreading & balancing these loads is by sheathing both faces. A glue line in tension at 90deg to the glued face with metal fasteners to frames to support the glue lines does not fill me with confidence when falling off a large wave. Minimum bulkheads/ring frames
    and structurally sheathed both sides has to optimum solution.

    Unless, the vessel is 100% traditional;designed to absorb water and tension the hull hydraulically against substantial frames and fastenings.
     
  11. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    I think the extra layer on the outside is not for panel stiffness but for puncture and scratching resistance. Some racing boats with thick sandwich and thin outer skins is very vulnerable. You remember the story about the proud new owner/builder/designer that hammered on his new carbon hull and asked visitor to do the same? One visitor turned the hammer around and made a big hole.
     
  12. Roly
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    Roly Senior Member

    :D :D ...I shouldn't laugh...but....dumb move. Moral of the story...don't get a woman to hammer your hull.;)

    Gender prejudice is allowed here...........it is the boat shed...afterall.
     
  13. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    Yeah, I can imagine the face of the owner :)
     

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  14. alan white
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    alan white Senior Member

    If the material used to tensily stiffen (vertically in the case of strip construction) alone were enough (in this case, epoxy/glass matrix), the outer hull sandwich would be enough.
    Bulkheads serve to impart enormous stiffness, and so what lies between must carry loads that distance without deformation.
    One could, as an alternative, stiffen vertically with battens of solid wood with spaces between (or none, as in cold molding). It is a fact, however, that doubling the thickness of frames (from, say, 1/4" to 1/2") yields not twice but four times the stiffness, so there is value in going to (fewer) tall rather than (more) flat batten-like frames is stiffness alone is desired.
    Such a shape would have enough surface area to bond well to the inside of the hull, enough "height" to provide maximum stiffness for its weight, enough resiliance to suffer and survive a deforming impact without damage, and in most cases, a practical means to construct.
    At first glance, considering stiffness alone, the sectional profile of such a frame might be imagined to be like an I-beam. However, while stiff, the I-beam section deforms but little just prior to failure; it is enormously stiff but not enormously resiliant, and so is well suited to an inshore racing boat because it is the lightest way to build with frames.
    A collision with a pointed object at sea is exactly the kind of accident that would favor a flatter frame section, which could give more (better in the middle of a bulkhead space than close to it).
    Falling off a wave would perhaps favor a comprimise section; not flat, not tall, but maybe square, and a design that does not overly stiffen where bulkheads are located, allowing stresses of deformation to carry to the furthest limits possible.
    While epoxy/ two-sided cloth/bulkhead construction is very practical, the design limits the area of deformation to boxed panels which must handle impacts on their own, and differently too, depending on proximity to bulkheads. This is not nearly so significant on lightweight boats whose mass more readily yields to outside influences. On a heavier boat, damage can occur before the boat can react.
    If I were to design a moderately heavy ocean cruiser in strip construction, I would allow for a certain degree of flexure by eliminating structural bulkheads as ultimate stiffening members, and go with solid wood frames, glued and screwed. They need not be overly large if the outside is glassed well, but should definately be closely enough spaced to provide a modicum of stiffness. Allowing extreme stresses to carry to the boat's corners would be ideal.
    Bulkheads, then, would be "loose" walls made up of boards, for example, instead of rigid ply, if bulkheads are desired.
    A hull that can flex in a springy way will survive better than an equal weight hull of monocoque (panel and bulkhead) construction. It will be lighter too, and also more difficult to build. Much of the reason for bulkhead construction is handiness of construction. It is not the best way to get survivability even though it is a very stiff hull for its weight.
    I used to charter an Eldridge McGinness cutter built in Hong Kong of strip method. The boat was 8 1/2 tons on maybe 27 ft waterline length, 31 ft on deck. She'd once suffered a mid-ocean collision with a freighter and while her pipe life rails had been destroyed, the hull itself fared quite well.
    She had no glass, was edge-nailed and glued (assumedly with recorcinol) and had moderate frames.
    It is assumed she flexed and absorbed the impact with her whole side.

    Alan
     

  15. frosh
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    frosh Senior Member

    Hi Tom, going back to your first post where you asked about the suitability of Titebond I have another option to epoxy which should be cheaper, easier to use, quicker setting, 100% waterproof, and gap filling. I will give you link to the Australian web site that is the manufacturer of Purbond and you can read about it. You might be able to get this or equivalent in the US.
    This is not intended to minimize the importance of sufficient reinforcement on either side of the strip core. Have you considered cold moulded plywood as a construction method. This only needs a thin external layer of fibreglass for abrasion resistance, as the plywood layers once bonded are fully structural in themselves. http://www.boatcraft.com.au/adhesives.html
     
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