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  • Question about lap joints and wood movement

    Hi all,

    Still trying to plan this bookcase project before it actually begins. The herringbone pattern plan is on the table, this is the other plan ...

    Attached a pic of some walnut I got for $50 after I jointed 2 edges and got all this plus some smaller blocks of scrap.

    If I mill these to the same thickness and square them all up, and I join them with lap joints to make long boards and then laminate them to get the 12" of width I need for each shelf ... will they "be fine" or do I have to join them differently to account for wood movement .. or is this just not a good idea ?

    I looked into buying boards that were the length and width I needed, and unf. the place where I bought had them but they were kinda rough for my price range, so I had to chop em into pieces. I'm fine with doing a significant amount (to me) of lap joinery if the final product would be fine, but if someone here says I should do something else with this would and buy bigger longer boards for this project, I'd be inclined to heed their advice if there are compelling reasons to do so.

    If this'll work, I can go back to my guy with another $50 and get the rest of the walnut for the sides, then make the back out of plywood and get pre-fab mid-century legs
    Attached Files
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  • #2

    Re: Question about lap joints and wood movement

    I'd square up all the pieces (joint and rip) and laminate them together with biscuits and glue. Plane once everything is dry.

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    • #3

      Re: Question about lap joints and wood movement

      If I were to join two boards end to end, I'd probably use a finger-joint router bit. And if you don't want to see the joint from the front, just glue on a 1/4" thick edge piece.

      Edit:. My eyes saw "lap joint" but my brain registered "scarf joint". Lap joint might be fine too but you'll need precise cuts if you don't want to see a gap on either face.
      Last edited by sancyk; 09-18-2021, 08:30 PM.

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      • #4

        Re: Question about lap joints and wood movement

        Originally posted by ThePracticalPeasant View Post
        I'd square up all the pieces (joint and rip) and laminate them together with biscuits and glue. Plane once everything is dry.
        Would I need to join the short ends together with something? Or just glue between the short ends as part of the laminating biscuit-based glue up?

        If I have dowel pins (like 80-85 of them in a bag) and dowel centering thingos, and no biscuit joiner .. would dowels "work fine too" or are biscuits "way better" for this laminating job?

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        • #5

          Re: Question about lap joints and wood movement

          But then again, I don't think I'd use solid walnut for a shelf. Walnut-veneered plywood is what I would use.

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          • #6

            Re: Question about lap joints and wood movement

            Originally posted by sancyk View Post
            But then again, I don't think I'd use solid walnut for a shelf. Walnut-veneered plywood is what I would use.
            We are considering this as well. Why would you prefer walnut veneered plywood ?

            My girlfriend loves walnut, so her whole thing was "well, we can buy enough walnut for the thing for $100" or "we would spend $160 for the veneer and then would need to buy the plywood" ... And then we'd not have a "hardwood whole wood" furniture piece.

            What are the compelling reasons for not using solid walnut?

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            • #7

              Re: Question about lap joints and wood movement

              Originally posted by Jfd986 View Post
              What are the compelling reasons for not using solid walnut?
              The walnut you have: Time/Difficulty
              Stock more suited to the project: Cost

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              • #8

                Re: Question about lap joints and wood movement

                Originally posted by ThePracticalPeasant View Post

                The walnut you have: Time/Difficulty
                Stock more suited to the project: Cost
                Okay that's fair, but if the cost of sourcing stock more suited to the project were around the same as the cost of the veneer wood, and if my girlfriend decides she doesn't "need" the herringbone ... Then would you say the solid wood build is "better" for the piece than the "plywood/veneer" build in terms of structural integrity and durability? Or would you prefer the plywood and veneer build?

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                • #9

                  Re: Question about lap joints and wood movement

                  Originally posted by Jfd986 View Post
                  Okay that's fair, but if the cost of sourcing stock more suited to the project were around the same as the cost of the veneer wood,
                  I think that's a big if. There was a recent thread regarding walnut, and it seems to run around $10/bf right now.
                  Your project will use upwards 20bf. I've never purchased walnut veneer plywood, but I cannot imagine that a 4x8' sheet of 3/4" will be anywhere near $200.

                  and if my girlfriend decides she doesn't "need" the herringbone ...
                  You know her... For a project like yours, unless you're using the veneer to mimic a more complicated construction, i.e., the herringbone pattern, if I were using a plywood core, I'd attempt to buy plywood with the correct veneer on the faces rather than making it from plywood and veneer myself. Walnut veneer plywood is available.

                  Then would you say the solid wood build is "better" for the piece than the "plywood/veneer" build in terms of structural integrity and durability? Or would you prefer the plywood and veneer build?
                  In my very humble opinion...
                  - Both methods can yield a quality piece, assuming care and technique, etc.
                  - Assuming equal quality work, I think the two executions would look very different
                  Last edited by ThePracticalPeasant; 09-18-2021, 10:38 PM.

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                  • #10

                    Re: Question about lap joints and wood movement

                    Originally posted by ThePracticalPeasant View Post
                    I think that's a big if. There was a recent thread regarding walnut, and it seems to run around $10/bf right now.
                    Your project will use upwards 20bf. I've never purchased walnut veneer plywood, but I cannot imagine that a 4x8' sheet of 3/4" will be anywhere near $200.


                    You know her... For a project like yours, unless you're using the veneer to mimic a more complicated construction, i.e., the herringbone pattern, if I were using a plywood core, I'd attempt to buy plywood with the correct veneer on the faces rather than making it from plywood and veneer myself. Walnut veneer plywood is available.



                    In my very humble opinion...
                    - Both methods can yield a quality piece, assuming care and technique, etc.
                    - Assuming equal quality work, I think the two executions would look very different
                    I hadn't considered getting the plywood with the veneer already on it, yes that would definitely be much less than $200.
                    My guy Peter in Hamilton is selling me walnut for about $4-5.50/bf but some of it is rather rough, so like you said, it becomes more of a time/difficulty issue. I need the experience more than I need the time savings, so I'm down to try milling everything and then biscuit joining just for the experience. Would dowel joining also work fine though for laminating?

                    Agreed, they would look completely different. I'll get her to google more / go visit a pro wood shop somewhere in Guelph, so she can see some stuff, and then decide.

                    ​​​​​

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                    • #11

                      Re: Question about lap joints and wood movement

                      Originally posted by Jfd986 View Post

                      We are considering this as well. Why would you prefer walnut veneered plywood ?

                      What are the compelling reasons for not using solid walnut?
                      Stability, cost, effort required, tool availability, product uniformity, durability would all impact my choice of one product over another.

                      With plywood, you'll get a flat surface and you're not limited to the width of your thickness planer (if you have one).

                      A good quality walnut plywood is not cheap though. I bought a 1/2" x 4 x 8 sheet a few years ago and it was around $100.

                      Take a look at the walnut furniture I made. The headboard is walnut plywood. The skirt for the bed is solid walnut. The doors and drawer faces are solid walnut. In retrospect, I would have used more plywood

                      https://forum.canadianwoodworking.co...nally-finished

                      Solid walnut will hold up better if the furniture will be banged up. Hence my choice of solid wood for the skirt.

                      But like you, sometimes I make a choice in material or technique to gain some experience as I stated in my furniture post.
                      ThePracticalPeasant and Jfd986 like this.

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                      • #12

                        Re: Question about lap joints and wood movement

                        I'd make a flat face, then trim it to about 1/4" thick on the tablesaw , you might have to cut both sides flip and finish with a handsaw. you can go thinner if you are comfortable or if you use a bandsaw.
                        then plane them flat and glue them over a piece of wood of your choice, which will be the core and unseen.
                        for the end to end joints I'd cut beveled joints and butt them.

                        figure out the size you want then laminate them on like thick veneer. do both sides. when you are done you can give the whole thing a trim , thickness planer , hand plane or put it through the saw to rough it out. if you want to be meticulous you can keep the grain orientation so you see end grain on the ends and edge grain on the edges. If you care that much.

                        if you want more strength I'd build the front and back edges so they form a rib to prevent bowing and make the shelf edge appear a bit thicker than the rest. If you want you can put a back on it. you can run a molding cutter along the front and give it a profile you like. if you want a back you can attach a strip to it to carry the back of the shelf to prevent bending.

                        the core can be plywood or solid strips of lumber glued up into a plank. , use what you have up. old plywood? another tabletop that you scrounged? I'd avoid MDF as it isn't so strong but you could do that if the strength is taken into consideration in the build.

                        Id try not to overbuild it so the proportions look like practical use of the wood and not like it's a high school project made of lumber that's way thicker than necessary. a 1/2" core might be enough.


                        Id rather veneer a core than to try to make all those bits into something structural. you'll never see the core once it's covered up. you can stretch out your wood that way and do more with less of that expensive wood.

                        Ive done this and made up things like door casings, the part that fits above the doorway.. where I wanted 1" but since old growth fir was scarce, so I made them hollow as they aren't structural , just there for cosmetics. I sliced up my 2x material into 3 or 4 thinner pieces because I liked the plank and wanted to show the grain. no one can tell they are a hollow box. For a shelf you want the support so I'd use a core. you want to prevent sagging by designing it to take the load.

                        since it's thick veneer then you can do things like run molding profiles or add contours, that makes it look more like it's a solid piece. you can do some roundovers, etc which you can't do with thin veneer.

                        use dry wood and make good glue joints it should stay together then. If you veneer just one side then you may have more movement from expansion and contraction so I'd do both sides of it.

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                        • #13

                          Re: Question about lap joints and wood movement

                          Think about the glue-up process before you decide to the take the random lengths you have and try to make boards out of them. You will need a perfectly flat surface to sit the pieces on that will not stick to them when the glue is dry. You will need long clamps to apply uniform pressure along the length of each strip without making it flex. That will mean something holding the pieces flat. You will not get perfect alignment end to end so each "board" will need trimming width-wise to achieve a uniform width from one end to the other. Then three of these "boards" will need gluing up. They will slide under pressure with the glue on them so dowels will be needed to hold them in place. At the end of this you have no guarantee the new 3-board will not have some cup or bow in it. All in all this is a huge amount of work with a doubtful outcome. I would look at alternatives.
                          KenL and like this.

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                          • #14

                            Re: Question about lap joints and wood movement

                            Go for it. Just as in your original plan!

                            Run the boards you through a planer, organize them and cut them into strips of varying width to minimize loss, lap joint or finger joint the ends to get the proper length and then glue the boards together. Then glue the lengthened boards together. Use a proper jig for glueing. If glue runout will be a problem Saran Wrap works well.

                            No need for biscuits or dowels. Just glue and proper jigs is all that’s needed. C clamps for the laps & pipe clamps for the full length. Make sure you use cauls. No need to get complicated. When finishing the sanding dust can make joint look insignificant with the proper methods.
                            Last edited by Egon; 09-21-2021, 04:21 PM.
                            Egon
                            from
                            The South Shore, Nova Scotia

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                            • #15

                              Re: Question about lap joints and wood movement

                              it might be easier for him to use some plywood with black walnut veneer and then just use some of what he as for edging and maybe do some sort of profile on those edge pieces. I wouldn't be the cheapest alternative or a great learning project.
                              I think he said they are only like 2 feet long and to me, making a shelf from 3/4 material leaves a sort of overbuilt look. maybe 1/4" ply with veneer and some edging to support it could be nicer. otherwise it might look like some Ikea made in china with swedish flag advertising junk.. over thickness because its garbage, that sort of look is common these days and it might be nicer if it's more proportionate. like the cabinets they sell with 1 1/2" of material between two boxes. Its done often commercially because the material is cheap and it's cost effective concerning labor but it's also an ugly approach from a craftsman perspective. a 2' span with 1/4 ply and suitable edging front and back is plenty strong. It doesn't need to be overbuilt like a brick sh% house to look nice.

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