Bed design considerations

[Mattia Valente]

[EDIT] that should be TABLE design considerations. Clearly I'm sleep deprived

Hi folks, this is my first post here - been lurking for a while.

My main woodworking related passion is guitarmaking (mostly electrics in my past, more acoustics in my future), I've built a couple of beds, and I'm currently preparing to tackle a few lager-scale working projects - a relatively involved bookcase (moving sections, rail and stile raised panel construction and so on, very much in the 'on paper' stages, might post for some feedback once it's matured) and, first on the list, a dining table.

The dining table was inspired by a recent wood score - bought a sizeable stash of indian rosewood for a song (about $6.50 a board foot). Most in shorter pieces suitable for guitar work, but also sawn 'wide' boards. Only about 10" or so to a panel, about 8/4-7/4 thick, and a lot (I do mean A LOT) of not that great looking sapwood, a few cracks, etc. Didn't want to do a live edge table type thing (not the right pieces for it), and decided they would make a great (start to) a tabletop. Boards have been acclimating in my living room for a good 3 months, so I spent a few hours yesterday trimming the pieces down and turning them into S2S lumber, currently have three boards measuring 8.5" x 72" x 1.5" (one's a little thinner due to some excessive cupping). They're currently stickered and weighted. I'm shooting for a table size of 72 x 39" (breadboard ends).

I had originally hoped to make a solid, rosewood-only top (with funky sapwood sections) by resawing the boards, but optimistically I would be looking 5/8" finished thickness, assuming resawing goes perfectly (I have a Woodmaster CT and I've got some experience resawing guitar backs, so not too worried about that). This strikes me as very thin for a tabletop, recipe for excessive movement, and high-risk of 'ruining' the boards and coming out with 1/2" finished panels, very flatsawn, and thus relatively prone to cupping and moving. I'll be making the base out of cherry (to match the future cabinet), so I'm pondering my options for the top:

'Rosewood only' solutions

1. Resaw down the center, shoot for 2 bookmatched sets (which won't be all that symmetrical) and one unmatched center section (the thinner board)
2. As above, add breadboard ends - Cherry or Rosewood
3. As above, build up the edges on the table to make it appear heavier/thicker using offcuts from the rosewood boards, leave breadboards and 7/8"-1" thick

'Mixed' solutions

4. Resaw conservatively, 3 indian rosewood boards flanked by a board of cherry on each side. 7/8" top thickness.
5. As above, add breadboard ends - Cherry or Rosewood

My stylistic preference is something relatively clean, and relatively light. Let the wood speak for itself, tapered legs, maybe a slight arch/camber to the apron, slight back bevel on the edges of the tabletop, no beading or other ornamentation. Will try to take some pictures of the boards this evening. Any thoughts, tips, hints would be very much appreciated.

[Jamie Buxton]

Here's one more option... Rip a thick rosewood board to get the two long edges to the table top. Do the same to get the breadboard ends. Resaw the other rosewood boards to get the middle of the table top. The result is an all-rosewood top, 1 1/2" thick around the edges, and 3/4" or so in the middle. If you're hesitant about the 3/4" middle, laminate that rosewood to some other species of wood to get 1 1/2" thickness there too.

[Mattia Valente]

Here's one more option... Rip a thick rosewood board to get the two long edges to the table top. Do the same to get the breadboard ends. Resaw the other rosewood boards to get the middle of the table top. The result is an all-rosewood top, 1 1/2" thick around the edges, and 3/4" or so in the middle. If you're hesitant about the 3/4" middle, laminate that rosewood to some other species of wood to get 1 1/2" thickness there too.

You mean a narrow strip off the side of two of the the boards (I have two thick, 1.5", one thinner, too thin to bookmatch)? I could joint that back almost invisibly, at full depth, and bookmatch the rest of the panels. I don't think I'll get a finished thickness of 3/4", more like 5/8". Simply wondering if that's too thin from a stability standpoint with flatsawn boards this wide. I'd be hesitant about laminating to a different wood, with a different expansion coefficient. Seems like a recipe for cupping, or am I missing something?

I have other stock I can use for the breadboards, so that's not a problem. I don't have any more long stock, however.

[Jamie Buxton]

You mean a narrow strip off the side of two of the the boards (I have two thick, 1.5", one thinner, too thin to bookmatch)? I could joint that back almost invisibly, at full depth, and bookmatch the rest of the panels. I don't think I'll get a finished thickness of 3/4", more like 5/8". Simply wondering if that's too thin from a stability standpoint with flatsawn boards this wide. I'd be hesitant about laminating to a different wood, with a different expansion coefficient. Seems like a recipe for cupping, or am I missing something?

I have other stock I can use for the breadboards, so that's not a problem. I don't have any more long stock, however.

Well, I wasn't thinking of ripping a particularly thin strip. I kinda lost track of how many of what thickness you have. I was just focussing on making the whole table top look like it is 1 1/2" thick, and all rosewood. In the attached sketch, the upper diagram is a cross section through the top as I was thinking about it. The lower diagram is option I mentioned of laminating the rosewood to some lesser species.

tablecrosssection.jpg

If you want to use a substrate species whose expansion coefficients are nearly identical to rosewood, consider poplar. Indian rosewood's shrinkage (from green to oven-dry) is 2.7% radial and 5.8% tangential. Poplar's is 2.6% radial and 6% tangential.

(Me, I think extreme matching is not required for stability. Notice that for those species, the difference between radial and tangential is about 2. When you're building a table, do you reject boards that are kinda quartered on one edge, but really flatsawn at the other edge? However, the expansion of those two edges would be different by a factor of 2 in this case. Yet most tables seem to do just fine like this. So I'm not very worried about mismatching the two laminated species.)

[Mattia Valente]

To be clear, I have 3 boards. 2 thick enough to resaw. Will take pictures later to help clarify the issues I have in terms of bookmatching.

As for the design, gotcha, thanks! I'm going to have a bit of a measure and a careful look at the grain patterns to see what I'm likely to get out of the book match. The method above will yield a slightly narrower table than I had palnned (33" finished). In terms of laminating, I'd always learned laminates should be odd numbered to prevent warp.

[Jamie Buxton]

.. In terms of laminating, I'd always learned laminates should be odd numbered to prevent warp...

That applies to plywood, where the grain direction of the layers runs across its neighbors. All I'm suggesting here is laminating the rosewood on to a substrate species, with the grain direction of the rosewood and the substrate running in the same direction.

[Jamie Buxton]

To be clear, I have 3 boards. 2 thick enough to resaw. Will take pictures later to help clarify the issues I have in terms of bookmatching.

As for the design, gotcha, thanks! I'm going to have a bit of a measure and a careful look at the grain patterns to see what I'm likely to get out of the book match. The method above will yield a slightly narrower table than I had palnned (33" finished). In terms of laminating, I'd always learned laminates should be odd numbered to prevent warp.

If you laminate rosewood on to some other species for the middle of the table, you can make the rosewood as thin as you can comfortably cut on your bandsaw. For instance, it could be 1/8" thick. You could get three bookmatched pairs from even your thin plank.

[George Gyulatyan]

I would take Jamie's idea a step further and suggest resawing veneers out of the rosewood (1/8" - 1/16"), and using MDF or MDF/honeycomb sandwitch (torsion box) as the substrate. This will open up some interesting design opportunities as well.

[Mattia Valente]

Hmm...interesting thoughts. I like the aesthetic of solid, bevelled edges and a slightly more rustic-but-refined look over boardroom flat, so a full torsion box doesn't seem to be the ideal solution for this, though I may have to build one as a router table soon. I like MDF for jigs and similar, but it doesn't feel right for use in a table I hope will be in use for a long time to come. Looking around at readily available wood species with similar properties and relatively low cost, I noticed Western Red Cedar has shrinkage coefficients and a ratio similar to EIR and is easier to find here than Poplar.

[Jamie Buxton]

Here's one more approach, taking off from George's suggestion. You slice one of the planks into bandsawn veneer -- like .1" thick. You build a core that has no hygroscopic expansion. It could be a torsion box, or it could just be two layers of plywood. You glue the veneer on the top of the core, and on the bottom too. This gets you the balanced panel you mentioned earlier. It also makes a panel which you cannot distinguish from solid lumber by looking at either the top or the bottom. On the edges of the veneered panel, you use pieces of solid lumber -- maybe 3"x1.5" in cross section, or some dimensions like that. The pieces on the short ends are arranged so they look like breadboard ends, covering the ends of the lumber along the long edges and the ends of the veneered panel. (The core has no hygroscopic expansion, so the breadboard ends can be glued solidly on, rather than the traditional sliding joint.) The result is a table that looks like a solid-lumber all-rosewood top with breadboard ends. You will know that there's a plywood core, but nobody else will be able to tell.

[Mattia Valente]

It's been, quite literally, years, but things like life, moving, new jobs and a PhD defense tend to get in the way occasionally. The main bit of the table was completed within a few months, but only got around to breadboarding the ends and finishing it off earlier this summer, and I figured it would be nice to post a few quick pictures of the result.

image1.jpgimage2.jpg

A few quick features:
- Base: tapered legs, European Cherry (2-piece laminates for the legs due to available material), mortise+tenon apron.
- Top: Solid Indian Rosewood outer panels, middle 3 laminated to WRC (top and bottom, 3/16" each, nicer laminates on top), final size 205cm x 106cm (about 80" x 42"). Solid breadboarded ends fitted dry, pegs made of scrap mahogany.

Finished using Osmo oil/wax products (Hardwax Oil for the base, Wax finish suitable for tropical woods for the top). I'm very happy with the result.