Newbie question about bookcase design


I'm building a bookcase with four fixed shelves (plus the top). It will be a total of 50" high and 30" wide.
The shelves will be sliding "half-dovetails." I've _tried_ to illustrate below what I mean, but basically think of a dovetail with only one angle cut in. I got the idea out of a design plan I bought, but the plan was more of a Craftsman-style bookcase with slatted sides, and I want solid sides.
The bookcase is being built out of flatsawn cherry (YOU try finding rift/quarter-sawn!), and the sides will be a total of 12" wide.
So here are my two questions:
1. Because the wood is flatsawn, the grain patterns are harder to match-up, so I would like to glue-up two 6" boards, rather than three 4" boards. I am doing this for the sides and the shelves. Because this is flatsawn, am I setting myself up for problems with cupping/etc?
2. The reason I'm doing the half-dovetails, instead of simply dadoes, is that I want the sides of the bookcase to be held together by the shelves themselves. I am NOT gluing the dovetails, but rather pinning them in the front to allow them to expand freely toward the back of the case. However, am I running the risk that, because I'm using flatsawn boards, that this whole thing is literally going to pull itself apart over time?
Thanks for any help you guys can give...illustration is below.
| | | | Shelf | _|_________ | | | |/|_________ | | | |
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You should be fine. Cherry is pretty stable. You identified and fixed the one big problem by pinning the dove tail, even though it is actually not an opposed grain situiation so the side and shelf should expand together.
One help for cuppng is to try and get boards that have the grain lines running as close to perpendicular to the face as possible, ie close to quarter sawn. Also, glue up the boards and let them settle for a few days. If any of them cup, just rip them down and re-glue.
Another somewhat radical idea, but it could be a nice effect, would be to bread board all of the pieces, sides and shelves. One advantage of this would be on the shelves you would be cutting your modified dovetail groove with the grain as opposed to cross grain. However, I would use and extra deep tennon to ensure you get good structural conformance from the shelf.
Sounds like a cool project.
BW
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wood snipped-for-privacy@yahoo.com wrote:

Why not use full sliding dovetails? Easier and double the grab :) ______________

It will be fine. Would be too if you glued them (I would) as any expansion in the shelves and ends is in the same direction. For that matter, you could dump the dovetails - half or full - and just glue shelf tenons into side dados...assuming the dados/tenons are a decent fit the sides aren't going to pull out.
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wood snipped-for-privacy@yahoo.com wrote:

board bark-side up and the other bark-side down. Result of any cupping will then be a wave in the board rather than a deep cup or hump.

Why? isn't the grain on the sides vertical, and on the shelves along the length of the shelf? If so, the sides and shelves should have the same front-to-back expansion, so no reason not to clue the sliding DTs.
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On 3 Oct 2005 08:01:56 -0700, wood snipped-for-privacy@yahoo.com wrote:

There should be problem with your plan. Traditionally, these would be dadoed and glued without any problem of expanding/contracting as there is NO cross-grain at these joints! It may be helpful to study grain directions so that you know exactly where to be concerned.
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wood snipped-for-privacy@yahoo.com wrote:

Go play with the Sagulator (google) before building any bookshelves more than 2' wide.

Even simple dados would be adequate. If you're routing these dovetails, then a full dovetail is probably easier to cut. Don't be afraid of getting an accurate fitting joint here - it's one of the easier parts to get right.

Actually I have no trouble (although cherry is itself scarce in the UK). It's a high-end timber, so it's one of the few where there is an obvious trade in quarter-sawn.

Now this starts to worry me. I think your shelf plan is sound, but a big slab side like this might need some care in design and construction.

Actually figure, rather than grain. Grain's the little stuff, figure's the big "cathedral" patterns you see on a flat sawn board.

For the shelves, then stop worrying. Assemble 4" boards because they're easier. On a loaded bookshelf you'll never see the difference. 6" boards sound quite reasonable for the sides though.

Depends more on the quality of your timber than on the size difference to 6". Personally I'd already have had this board in stack for a year or two before I got round to using it. I'd certainly store it at ambinet use humidity for a few months before planing it (you do have some $5 air hygrometers, don't you?)

Up to you. It's no problem to glue them because it's not a cross-grained joint. Personally I wouldn't even pin them - friction is plenty adequate. Just pinning at the front would be the right thing to do though, if you did pin them.
Any relative movement in the timber is going to be cupping, not shrinkage (if these boards are all the same timber from the same batch). I'd worry about cupping in the sides, but not the shelves.
Personally I'd be concerned about the sides in this design. I'd want something to support the sides against cupping, particulary if they're 6" wide and relatively thin. This could be framing top and bottom, full-blown frame and panel, or a sliding dovetailed batten on the inside. Most of all though I'd just want those sides to be well-dried before I planed them, and not too thin.
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snipped-for-privacy@codesmiths.com wrote:

wouldn't his sliding dovetail shelves serve this purpose?
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