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Thread: Beginner question laminated vs solid wood

  1. #1

    Default Beginner question laminated vs solid wood

    Let me see if I can phrase this correctly

    as a general rule would a 3/4” x 1 1/2” x 8’ beam be stronger, stiffer, less resistant to breaking, etc if it was one solid piece (assuming proper grain orientation no run outs etc.) or laminated from 3 1/4” x 1 1/2” x 8’ pieces (assuming it was glued correctly)?

    i know back in the day wooden bows were often backed to resist breaking even to the point of cutting the wood lengthwise swapping the ends and glueing the same piece back together

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    Default Re: Beginner question laminated vs solid wood

    Yes laminated I’d stronger .
    Three quarters of an inch by one and a half inch is a beam?

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    Default Re: Beginner question laminated vs solid wood

    Same straight grain timber for both makes no difference. Each will be as strong as the other.
    It really is quite difficult to build an ugly wooden boat.

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  4. #4

    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by wizbang 13 View Post
    Three quarters of an inch by one and a half inch is a beam?
    it was an example I could have called it a stringer or a rib it was just a way to ask the question

  5. #5

    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by Peerie Maa View Post
    Same straight grain timber for both makes no difference. Each will be as strong as the other.
    so does laminating become stronger when the wood isn’t perfect re grain?

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    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by jaxenro View Post
    so does laminating become stronger when the wood isn’t perfect re grain?
    When the wood for which isn't perfect?

    As as a general rule, laminating will be stronger than one piece.

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    Default Re: Beginner question laminated vs solid wood

    Laminations used in boat building generally are used to make parts that have curvature or would other wise be difficult to cut from one piece of wood.

    Laminates are stronger than parts cut from straight grained boards where the curvature creates crossgrain runout. They may or may not be stronger then parts cut from natural crooks.

    Actual strenght gains in laminated straight beams verus solid lumber is dependent on multiple factors. In your example of a 3/4" board there would be little to no gain in strenght from 2 glue lines. The member would be predominantly dependent on the strenght of the wood not the glue.

    For further reading: http://www.woodcenter.org/docs/ramme96c.pdf

  8. #8

    Default Re: Beginner question laminated vs solid wood

    Interesting reading thanks

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    Default Re: Beginner question laminated vs solid wood

    One advantage to laminating is that it saves precious wood. On my Lightning, my bottom frames are mahogany, and some of them are 6 ft long with a modest but still significant curve to them. As a rookie, I just went ahead and sawed those frames out of solid mahogany. But I had a heck of a lot of waste.

    By the time I got to the deck beams, I realized that I could make my curved components from straight strips of wood, and was convinced it was worth the extra effort to laminate them. It was slow going but I think I saved a lot of expensive wood.

    In addition, my naval architect friend advised that laminated components would be stronger, figuring that very little solid wood has perfect grain and is completely free of voids.

    So my current thinking is to laminate early and often. But, if you are a hurry, you need to take into account the time and effort that goes into laminating.

  10. #10

    Default Re: Beginner question laminated vs solid wood

    I guess I am more trying to understand the benefits vs drawbacks

    i have made quite a few wooden bows and I almost always backed (laminated) them because they were less prone to breaking especially ones made from boards. But then again they bend over and over. Plus with bows it is often common to use dissimilar wood for the back and belly to take advantage of the different properties of each but I see little of that in boat building?

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    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by jaxenro View Post
    I guess I am more trying to understand the benefits vs drawbacks

    i have made quite a few wooden bows and I almost always backed (laminated) them because they were less prone to breaking especially ones made from boards. But then again they bend over and over. Plus with bows it is often common to use dissimilar wood for the back and belly to take advantage of the different properties of each but I see little of that in boat building?
    Laminates always make a stronger beam for a simple reason. The grain is not continuous through the whole piece so the weak points of one laminate will be supported by the adjoining laminate that has its weakest points at different locations. You can think more complicated, but that is about it.

    Stability of the final glueup will also be much improved by laminating. In this case, its the natural grown in stresses of individual laminates that get distributed that make it more stable.
    Tom L

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    Default Re: Beginner question laminated vs solid wood

    The comparison of bow construction and boat construction is not really valid. The designed use of the materials is entirely different.

  13. #13

    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by navydog View Post
    The comparison of bow construction and boat construction is not really valid. The designed use of the materials is entirely different.
    Of course but like any beginner I am relating it to things I know in order to frame my questions. I know why I laminate a bow I am trying to understand why for some small boats parts like stems are laminated and for others sawn, and for others sawn from plywood which seems a little of both

    although if laminating something like a curved bent rib would it make any sense to use a wood for the inner laminations that handled compression well and for the outer one that was stronger under tension?

    Hickory for instance is tough and bends well but heavy but would s thin layer laminated to WRC give you the best of both worlds?
    Last edited by jaxenro; 04-29-2018 at 10:52 AM.

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    Default Re: Beginner question laminated vs solid wood

    Compression and tension are created during the installation process. By using a lamination most of the forces of bending are eliminated or at least greatly reduced. The important properties of a rib is it's ability to resist deflection and shearing.

  15. #15

    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by navydog View Post
    Compression and tension are created during the installation process. By using a lamination most of the forces of bending are eliminated or at least greatly reduced. The important properties of a rib is it's ability to resist deflection and shearing.
    interesting thank you. More research reading for me on deflection and shearing now.

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    Default Re: Beginner question laminated vs solid wood

    Besides it's being often being a more efficient use of lumber as well as an excellent way to eliminate run out on a curved member laminating curves has a further advantage. When comparing the forces of tension and compression on the faces of a 1/4" curved lamination to those same forces on the faces of a 3/4" bent board those forces will be considerably less on the thinner piece. By distributing those stresses amongst 3 laminations you reduce the likelihood of rupture or crushing. That's why laminating works so well for a bow, and the same applies to ribs, and up to a point, the more laminations the better. It's not that important for a stem, since they are more heavily built and well supported by the planking and decking, but it's still advantageous to avoid the end grain that's exposed when sawing out curves, plus of course the savings in lumber.

    Regarding that savings in lumber, it's not always that useful since a lot of wood goes into making sawdust and shavings, but by laminating at least one needn't source wider lumber.

    If you really want the member to be stronger you can back and belly it with materials that have the appropriate properties, as you mentioned, but for ribs, which are inclined to flex in both directions you would want to use something that's appropriate under tension and compression, Yew or Osage Orange for instance. Both are very rot resistant and are good choices for boats.

    You can also stiffen a curved laminated member by laying glass between the layers in epoxy. I know, the glass will add more strength if it's applied to the faces, but if you don't want to see it and don't want to have to protect the epoxy from UV adding it between the layers is a viable option. I've done this and can say that it adds a lot more stiffness than one would expect. If the face veneers are thinner than the rest the glass will be closer to the surface and will add more stiffness than if the laminations are all the same thickness.

    I expect WRC would make a pretty good neutral wood if the back and belly materials were thick enough. I'd be much more inclined to use AYC, but then I'd just use AYC for the entire piece, and usually do. It will hold fasteners better and is even more rot resistant, and will probably weigh the same.

    Hickory rots.

    A laminated straight beam will seldom be more than marginally stronger than a solid one, given the use of straight grained lumber, unless of course there is glass between the laminations.

    What are you considering building?
    Last edited by Gib Etheridge; 04-29-2018 at 12:28 PM.

  17. #17

    Default Re: Beginner question laminated vs solid wood

    For starters just a decked canoe of a Rob Roy type and I will stick to what the designer recommends. I am still debating glued lapstrake or other methods or even GABoats skin on frame Rob Roy.

    I know enough not to try to reinvent the wheel on my first build I will buy plans and follow them closely this was more a academic discussion trying to learn

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    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by jaxenro View Post
    For starters just a decked canoe of a Rob Roy type and I will stick to what the designer recommends. I am still debating glued lapstrake or other methods or even GABoats skin on frame Rob Roy.

    I know enough not to try to reinvent the wheel on my first build I will buy plans and follow them closely this was more a academic discussion trying to learn
    There is normally only one straight piece of wood in a boat, that is the keel. Keels are always sawn from solid, no one has seen the need to laminate one. As to stems, frames, planks, stringers, and deck beams they are all either curves or bent, so the curved stuff can benefit from laminating if they won't bend in the solid.
    Bent timbers or ribs are better steam bent as making a laminating form for every frame, and lofting and cutting the bevels is also a shed load of extra work. Laminating comes into its own for scantlings too big to steam bend to tight curves.

    A clinker boat gains its strength from being monocoque, each component supports its neighbour and so can be lighter.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by Peerie Maa View Post
    Keels are always sawn from solid, no one has seen the need to laminate one.
    There are dozens of wooden boat designs built with laminated keels. Hundreds or thousands with laminated stems. Simple reason in the US these days it's a pita for most people to source appropriate timber.
    Last edited by Hugh Conway; 04-29-2018 at 05:23 PM.

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    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by jaxenro View Post
    Let me see if I can phrase this correctly

    as a general rule would a 3/4” x 1 1/2” x 8’ beam be stronger, stiffer, less resistant to breaking, etc if it was one solid piece (assuming proper grain orientation no run outs
    etc.) or laminated from _3 1/4” x 1 1/2” x 8’ pieces (assuming it was glued correctly)?

    i know back in the day wooden bows were often backed to resist breaking even to the point of cutting the wood lengthwise swapping the ends and glueing the same piece back together
    No, you didn't phrase it correctly. But we know what you meant.
    Tom's answer is correct.
    Quote Originally Posted by Tom Lathrop View Post
    Laminates always make a stronger beam for a simple reason. The grain is not continuous through the whole piece so the weak points of one laminate will be supported by the adjoining laminate that has its weakest points at different locations. You can think more complicated, but that is about it.

    Stability of the final glueup will also be much improved by laminating. In this case, its the natural grown in stresses of individual laminates that get distributed that make it more stable.
    You rarely see solid girders in building construction. They use multiple 2x stock even though the total thickness is less (three 2x10s = 4.5" thick one 6x10 is 5.5" thick), because the defects tend to be smaller and more scattered. Since boat builders generally select and pay a premium for better quality stock, this should be less of a factor. Still true, but not as important with premium quality starting material.

    Quote Originally Posted by navydog View Post
    Compression and tension are created during the installation process. By using a lamination most of the forces of bending are eliminated or at least greatly reduced. The important properties of a rib is it's ability to resist deflection and shearing.
    Minor clarification: This applies to laminating curved pieces to avoid difficult bends. When straight pieces are laminated to make them larger, it is usually due to a lack of available large stock.
    Quote Originally Posted by navydog View Post
    The comparison of bow construction and boat construction is not really valid. The designed use of the materials is entirely different.
    I will disagree here to some extent. While it isn't obvious in a thicker, more rigid structural member, the physics or engineering are the same. When you are building more flexible parts like masts, spars and oars where considerable flexure is intended, the relationship is more obvious. A bow is just an extreme example where the intended induced stresses are very high. An engineer might call the difference stiffness limited vs stress limited design.
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    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by Hugh Conway View Post
    There are dozens of wooden boat designs built with laminated keels. Hundreds or thousands with laminated stems. Simple reason in the US these days it's a pita for most people to source appropriate timber.
    Woodwinds keel is lammed of 2X6’s of AYC. It makes it more stable, more strong, more rot resistant,more worm proof,faster to build ,quicker to season , than a big nog of tree.

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    Default Re: Beginner question laminated vs solid wood

    Glass (or carbon) in a wood lamination has its place.
    If the glass fibers are across the piece, cross-grain strength is improved. Useful if the end of the lamination is to be screwed to install.
    If they're along the lamination, the long-way properties of the lamination are improved. It's amazing what a little glass or carbon uni under the outside plies can do.

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    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by jaxenro View Post

    although if laminating something like a curved bent rib would it make any sense to use a wood for the inner laminations that handled compression well and for the outer one that was stronger under tension?

    Hickory for instance is tough and bends well but heavy but would s thin layer laminated to WRC give you the best of both worlds?
    There is a type of boat that employs bent forms wherein the inner/outer skins are different from the core layers. The all wood planks of modern iceboats are typically constructed of inner/outer skins of a hardwood, usually ash, and inner cores of a softwood, like Sitka, basswood, WRC, etc., All of the stresses, which in iceboating are enormous, are born by the inner/outer layers. The prevailing wisdom says that any light "white" wood will do for cores. In iceboating the lighter your boat the faster you go. The strength of the inner cores, up to a certain point, are irrelevant. This construction practice is relevant to softwater sailing if you are seeking ultimate lightness and strength for perhaps racing or portaging scenarios for wooden boats. Other than that I can't think of any really good reasons to bother.
    Last edited by Dusty Yevsky; 04-29-2018 at 11:45 PM.

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    Default Re: Beginner question laminated vs solid wood

    Quote Originally Posted by MN Dave View Post
    No, you didn't phrase it correctly. But we know what you meant.
    Tom's answer is correct.
    You rarely see solid girders in building construction. They use multiple 2x stock even though the total thickness is less (three 2x10s = 4.5" thick one 6x10 is 5.5" thick), because the defects tend to be smaller and more scattered. Since boat builders generally select and pay a premium for better quality stock, this should be less of a factor. Still true, but not as important with premium quality starting material.


    Minor clarification: This applies to laminating curved pieces to avoid difficult bends. When straight pieces are laminated to make them larger, it is usually due to a lack of available large stock.

    I will disagree here to some extent. While it isn't obvious in a thicker, more rigid structural member, the physics or engineering are the same. When you are building more flexible parts like masts, spars and oars where considerable flexure is intended, the relationship is more obvious. A bow is just an extreme example where the intended induced stresses are very high. An engineer might call the difference stiffness limited vs stress limited design.
    Dave,
    I'll stick with my comments as a mast and oars are not boats. Additionaly hulls and decks are designed to achieve rigidity using an elastic material to create curved shapes, where as a bow is designed to utilize the elastic properties of wood each cycle of use.

    Because wood is the primary substance comprising either a laminated part or a solid part there will be potential for flexation.

    A minor correction in your comments concerning glulams in building construction. The main reason glulams are used is do to the lack of available trees to make large beams and the cost of associated with a solid beam. Additionaly glulams can be built longer, larger and in arched forms that could never be achieved from single timbers.

    The over riding factor in glulam use is that anybody can make them from availible lumber supplies.
    Last edited by navydog; 04-30-2018 at 05:00 AM.

  25. #25

    Default Re: Beginner question laminated vs solid wood

    I want to thank everyone for posting to what was essentially a academic question it was very educational for me. One of the designs I have been looking at is the Chuckanut 15 which has this interesting tidbit

    "To avoid hogging and keep the sheerline as designed, we will simply laminate the gunwales in place on the frame. That is, the gunwales will be made up of two smaller pieces of wood that are glued together"

    From what I understand of this even though one piece can be bent to fit without too much difficulty the natural inclination of the wood to eventually return to straight is offset by gluing two pieces of wood together with the proper shape glued in
    Last edited by jaxenro; 04-30-2018 at 07:57 AM.

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    Default Re: Beginner question laminated vs solid wood

    Nathanial Herreshoff often used sheer strakes that were thicker on the edges, near the caulk seam, than in the center of the plank on small craft. This, reduced weight a bit and created a concave cross section that resisted edge flexing and hogging of the sheer.
    Jay

  27. #27

    Default Re: Beginner question laminated vs solid wood

    I get the feeling that for every one question two people will provide three different answers, all valid, and there is probably a fourth way as well. So many different ways of getting to the same end and all perfectly valid

    just to do do a little sorta version of the Rob Roy I see traditional lapstrake, edge glued lapstrake, stitch and glue, strip planked, and skin on frame all ending up with a version of a decked canoe. Each different in some ways and similar in others and all perfectly valid approaches

    even skin on frame can run from sawn plywood frames to steam bent ribs lashed with sinew or glued with epoxy

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