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Thread: Need input on creating this laminated coffee table base

  1. #1
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    Need input on creating this laminated coffee table base

    My next project is going to be a coffee table. We've settled on this design from Restoration Hardware. The trick is their table is actually made out of metal: an iron base and a sheet metal top. I want to make the whole thing out of wood (currently thinking walnut).

    I've never done bent lamination before, been reading plenty about it, but thought I'd throw this out for any opinions before I seriously get started. You can see that each leg of the base is basically two U-shapes. Well, one's a "u" and one's an "n" I guess.

    I was thinking of laminating each piece like this: /````\ there'd be a couple inches completely flat, then the curves would kick in. Then I would glue up two of the u-shaped pieces (along the flat edge) to form one leg of the table.

    Do you think the curves are doable via lamination? Do you think the leg will be strong enough?

    In the pic below I imported the design into sketchup and did my best to get valid measurements of key dimensions (like the height and radius of the curves).

    Thanks for any input!Rest-Coffee-Table.jpg

  2. #2
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    Hi Chris---

    I've done a fair amount of bent lamination and I think this project looks quite do-able. The radii look fairly tight, so you will want pretty thin layers. Prep a piece or two and see how easily it conforms to your form. Err on the side of thinner pieces. And don't forget about springback.

    Strength won't be an issue at all, as I see it. You will need to create some rigidity between the leg sections.
    Overall, it looks like a good project for an introduction to bent lamination. Have fun and good luck.

  3. #3
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    Thanks Jerry, glad to hear I have a green light to proceed! Good thing you mentioned rigidity between the leg sections, I hadn't even put any thought into that yet. I was only thinking how easy it would be to duplicate what they did with the iron rod stretcher. But since I'm working with wood, and not having the steel top welded to the base, this thing won't have much racking resistance. I might need to come up with some kind of low profile apron system. Hmm, maybe two long 1x1 rails right beneath the top, connecting the tops of the opposing leg assemblies. That would give me a total of three rails between the legs.

    That might work out better because that will give me a better way to attach the table top. Right now I was thinking of screwing down through elongated holes in the top and into the four points of the legs. The top will be 1.5in thick, and I was going to recess the screw heads, then cover them with some large contrasting wood caps, lightly pillowed like Greene&Greene, but much larger, maybe two or 3 inches square to look proportional to the top.

  4. #4
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    angle table 1-1-13.pngarch table 1-1-13.pngI think you should think a little harder about racking strength. A 1 x 1 apron won't offer much. I don't want to highjack your design, but you might consider an angle brace, or even an arched brace----something along the lines of the attached sketches

  5. #5
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    Ooh I like that second one!! That'll be a challenge to make. couple questions though:

    Does the stretcher attach to the bottom side of the top? By what means, and how will it allow for wood movement?

    how much wiggle room will the stretcher allow across the curve? Seems like a pretty tall order to glue up something that long and get it to precisely meet in three points: the two legs and the top.

    thanks for the help on this Jerry.

  6. #6
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    I like the 2nd one too. I don't think you would need to attach the stretcher to the top. Still, the top of the stretcher could meet the underside of the top. Make the beam long of course and cut it to fit. If the beam is as thick as your legs I think flexing would be negligible, leaning to none. Attach to the legs with tenons or dowels even, though I'm inclined to the tenon for best gluing and rack resistance. And as Jerry cautioned - don't forget about springback - especially for the leg pieces. Great project!
    "... for when we become in heart completely poor, we at once are the treasurers & disbursers of enormous riches."
    WQJudge

  7. #7
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    I'm not used to thinking in three dimensions with these curves. That makes perfect sense to build the beam extra long then just trim to fit, plus as long as I make the base first then there is plenty of wiggle room to determine the final length of the top. I was shooting for 67in long but who cares if it ends up +\- an inch or two.

    Santa brought me a Domino for Christmas, so I was already thinking I would use that to join the stretcher to the legs. I'll just need to step up to the biggest tenon size they have and probably double up the tenons on each end.

  8. #8
    FWIW, if the stretcher is attached in the middle of the top, that's not going to be an issue for wood movement of the top. The place you need to deal with that is out at the tops of the legs.

    FWIW, I had a little play with your images in SketchUp, Chris. You probably want to rework the dimensions from what you got because some of them are not right. You could get closer with PhotoMatch although the image has been modified after it was shot so things don't line up perfectly. Still, you can get closer than what you've got.

  9. #9
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    Thanks Dave, I figured sketchup would have some kind of dimensioning utility like that, but I googled it for only about one minute and didn't see anything so I just winged it. I knew the height width and depth for sure so I just scaled the images to match.

    I'll have another go at it using photo match, thanks for the tip.

  10. #10
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    You can certainly use bent lamination to make those big C shapes. However, when you attempt to cut that flat on the C, things may get a little wonky on you.
    Here's the deal.... In general, the more laminates you have in a bent lamination, the less springback. Conversely, fewer laminates results in more springback. When you cut the flat into the C, you're reducing the number of laminates in that area, so there will be more springback there. That is, the C will try to straighten out.

  11. #11
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    I was thinking best case I would laminate them in that shape (with the flats transitioning to curves). If that isn't possible then I'd do the C shape and cut the flat as you mentioned, but I didn't realize that it would springback even after being laminated and cured. I'll have to cross my fingers that option 1 will work.

  12. #12
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    Quote Originally Posted by Chris Merriam View Post
    Does the stretcher attach to the bottom side of the top? By what means, and how will it allow for wood movement?
    Yes, I would attach it: dowel, screw, loose tenon (Domino), .... Wood movement here is not a problem---it attaches at only one place to the top so does not restrict wood movement (as Dave said in post #8)

    Quote Originally Posted by Chris Merriam View Post
    how much wiggle room will the stretcher allow across the curve? Seems like a pretty tall order to glue up something that long and get it to precisely meet in three points: the two legs and the top.
    I think you get it now that the arch is built long and trimmed to size after.

    Jamie is right about the C changing shape after the flat at the joint is cut. The answer, IMO is to make the C's overbent and over-long, trim the meeting flat first, then determine the cuts at the ends of the "arms" of the C last.

    This will be a great learning experience in bent lamination, and part of the beauty is the dimensions are not written in stone, so you can be a little flexible with radius and overall width of the leg assemblies. Keep track of how it all goes, and when you do your next bent lamination project, you will have significant experience!

    Have fun, and let us know how it goes

  13. #13
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    Quote Originally Posted by Chris Merriam View Post
    I was thinking best case I would laminate them in that shape (with the flats transitioning to curves)
    Chris--- I think you'd be better off bending the ends in a continuous curve and cutting the flats after. Design-wise, you want the inside of the C to be a continuous curve. Making the form transition from curve to flat on the outside and keep a continuous curve on the inside could be problematic. I would keep this project as simple as possible: simple, continuous curves for the laminations, with flats and joints cut after.

  14. #14
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    Lol I completely missed the obvious there, thanks for setting me straight! I certainly want a nice curve on the inside.

    I'm going to show your sketch to the wife tomorrow for approval then I'll hop into sketchup and get this thing drawn out for real.

    What do you recommend for the form material on this: mdf, plywood?

    I understand some forms can be crushed, not sure if my case is that extreme or not.

  15. #15
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    I usually use mdf because it's relatively cheap, stable, and easy to work with. But you can use almost anything. Particleboard is a little cheaper, and fine for this. Plywood is good, too. I usually use a liner of something smooth---could be masonite, an extra laminate, Formica, acrylic, ....

    Provide a place for clamping when you make the form----expect to use LOTS of clamps.

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