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Thread: Case design

  1. #1
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    I'm thinking of building a case for my tenor, and experimenting with steam bending at the same time. It would be my first time bending, so I would appreciate it if people that do this kind of thing could nudge me back on the right track. I'm planning on using 3"x48"x1/8" and 5"x48"x1/8" Spanish cedar.

    It's going to take several pictures, so it's probably best if you withhold laughter until the end.

    The design is basically a Valentine-candy box: two halves, one of which fits snugly inside the other. The assembled version is on the left, the two halves on the right.
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    First, a buck, made out of 1/2" plywood cut to form, separated by 2x2s to give it depth.
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    Then, a piece of 3"x48"x1/8" wrapped around one end.
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    The second one wraps around the other end, naturally.
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    Hi Kww,

    Sounds like a cool project. Looks like you have a good handle on the CAD end. Just curious-- why the "candy box" design? I would think a split/hinged design would be a lot easier to make (one form instead of two), and easier to open.

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    I'll manage it with one form ... just watch.

    Here, the two pieces butt-spliced, and then two more bent and laminated on using the first layer as a form. The green lines illustrate how far staggered the butt-splices are: the lap joint is about 3.5", which should provide plenty of strength.
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    1/4" strips added to the buck to support the top of the outer layer. Alternately, the top plywood sheet could be cut 1/4" bigger than the bottom two. Not sure how much difference it makes. I'm interested in whether not having the curves supported at the top is a real issue or not with 1/8" stock.
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    Next, the process is repeated with the 5" pieces, wrapped around the buck and the inner layer of the box, with the butt-joints staggered.
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    Cut a panel out of plywood to fit the interior of the bottom (this is being built upside down, if you hadn't noticed). Maybe glue it in now, or wait until the next layer is on. Again, advice welcomed.
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    Panel the top with 5" stock: the green lines show the cut pattern. 1/4" or so larger than the sides. Glue to the plywood panel. Glue to the sides now, or should the plywood panel and this be glued to the sides at the same time?
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    Trim the sides of the panel with a router, shape to fit the sides precisely, and the bottom is done. Attaching a panel to the top would be done exactly the same way as the bottom.

    Pictures done now, comments appreciated.



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    Well, I either planned it so perfectly that you are sitting in awestruck silence, or so badly that you can't stop laughing long enough to type. I wonder which it is.
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    What a cool process! #Well thought out, I want to see finished pix too! Could you still do the "split, hinged top" concept by simply sawing through, leaving the sides double thickness?



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    The candy box style is a unique design. How will you secure the top and bottom so the bottom doesn't fall out when walking around? Also, will you have to shake it to get the top away from the bottom (I would imagine you wouldn't get a perfect seal. If you do use a gasket to get a good seal (to aid in humidification during storage) that may be a concern for breaking the seal so air can get in so the two halves can separate.

    It is a neat looking woodworking project.

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  15. #15

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    Neat design, clearly very well thought out, but I fail to see the advantage of the candybox.

    You could take your inner part and attach a lid with a big piano hinge. What about a handle?

  16. #16

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    I wonder if its overbuilt. Why not build an outside mold and run kerfing around the edge for joining the bottom. Foam cut to fit would supply a considerable amount of support and you could then cut the shape of the instrument out of the foam.

    Also, if going with the candy box idea then you might want to leave a little bit of a lip on the bottom for the lid to rest on. In other words, use the top as the guide when trimming the bottom.

    I like the idea of building something unique yourself, but not sure how practical the design will be. What is the length and width?

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    Main advantage of the candy box is minimal protruding hardware: no hinges. I'm trying to devise a pinbutton system to do the latching, so it wouldn't have protruding latches.

    I hadn't thought about humidification, and probably wouldn't unless I moved. My environment is a stable 80%-90% humidity year round, with stable temperatures between 78F and 94F.

    Dimensions are 35"x14"x5.5".

    It probably could be hinged by making it out of three layers of bent 5" stock, and then carefully slicing the two halves ... I'll have to think on that.

    And yes, it's overbuilt. A problem I tend to have with everything.
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    Kevin,

    Lovely CAD drawings, and a very impressive, clean design. But I suspect that you will soon weary of the candy-box approach every time you want to pull out your instrument. I love the idea of the clean lines and minimal latches, but I think the actual opening and closing process will be very cumbersome and space consuming, and I think the double-shell approach will add a lot of unnecessary weight. Also, it seems like getting the tolerances on the clearances between the inner and outer shell would be very extremely critical. Too loose, and the two halves will rattle out of alighnment, too tight and they might create a vacuum when you tried to open it.

    Also, how are you planning to attach a handle? If it's only attached to the outer shell, you'll need to figure out a way to reinforce that area even more, and prevent the outer shell from stressing under tension and separating from the inner shell at that point.

    Most standard ply cases are either three or five plies, not solid cedar stock. I suspect the two plies you have planned will be sufficient for a single-shell approach.

    Is your design based on a desire to just eliminate hardware as much as possible? If not, there are some very cool, clean, lightweight alternatives to the conventional latches found on most cases. Check out the latches used on the BAM HighTech cases, for example.

    Still, it's a cool, unique idea, and we'll all learn something from your process--whichever way you go.

    Keep us posted.

    Good luck.
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    Good, detailed process. I guess my first take is the overall shape. It'd be tougher on the tolerancing, but I'd explore some shapes that match the instrument shape more closely. Just a thought.

    Nice job w/the texture mapping of the wood grain bitmaps. Whatp program you using? I'm working in Rhino now here at work.
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    This design is similar to some very old designs for a violin case. Three hundred years ago, wedge shaped cases were used with similar, some overbuilt, designs. What seemed to happen to them, and I'm just guessing, is that the hardware pulled out of the wood and they learned that an arched top and bottom are stronger. And that's where people and horses step on them! Still they are beautiful to look at and I've thought of making one. But I'll keep the horse away from it!

    Also padding on the inside is a big deal and I'm wondering what you plan for that.
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    Another post to congratulate you on your CAD work. It would seem a shame to go to all this work and not take advantage of what you can do with the "cold moulding" construction system. With the addition of arch top and back you can end up with a case that is as rigid and protective as a bank vault, yet compact and esthetically pleasing. The 1/8" thickness of your material might be a limiting factor, restricting the ablity to make some bends; with a somewhat thinner material you may be able to dispense with the steam bending. Vacuum bagging is of course a possibility (a real good one). We're you able to obtain the Spanish cedar on Bonaire?

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    The internet reaches all over the world, and 1/8" Spanish Cedar is available that way. There really isn't any bending stock available on the island, and I don't think anyone has a good thickness planer. Carpentry is a common profession here, but luthiery and other forms of fine woodworking are unheard of.

    I'm still rethinking this plan based on the comments I've received. Thinking of eliminating the candy-box, and simply recessing a lid. Saves wood and time, and eliminates the vacuum problem that I hadn't even considered.
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    One advantage - flatter shape, stickers won't wrinkle.
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