I thought I read here one time when making thick bookcase shelving there is a honeycomb insert that would go between a substrate making wider shelving stronger. Does anybody have any information about this or other recommendations for making a 1 1/8'' x 60'' bookshelf stronger without sagging?

You could make it as a torsion box, which will resist sagging very well, with 1/4" exterior skins and 1" x 1 1/8" nosing.

You could use the honeycomb or just make a ladder-style interior core with unfilled voids, at that size the honeycomb wouldn't add much to an 'unfilled' torsion box.

Depending on just how much weight is going to be on these, I'd find it simpler to build them with 3/4" high quality plywood (ie, domestic or european), and put a 1-1/8" hard maple nosing along both the front and the back.

If the client requires the underside to also be perfectly flat, I'd attach the nosing on both long edges with glue and pocket screws to the 3/4" and then infill between the nosings with 3/8" MDF or plywood glued in.

I'm struggling to see a torsion box at only 1-1/8" thick be that much stronger than a plywood slab with double hardwood nosings. If this were 3" thick, then I'd definitely be looking at a putting in some torsion box architecture.

Even with ply and a hard maple edge sagulator comes up as acceptable barely on 60" span. Thats inputting 1 1/8 thick, 12" deep, 60" long fir ply, with 1 1/8" x .875" thick solid wood edges, 40lbs/sq' uniform load (books)

60" is a mile of span. 1 1/2" (either solid ply or two layers of 3/4 glued) and hardwood edge would be my lowest option for a 60" shelf and I would for sure make them flippable so as they sag (which they will) they can be flipped over time.

Be nice, but Ive never seen any type of torsion box calculator. Would be interesting to know if a well constructed torsion box would meet or exceed a solid shelf.

Nice suggestions and well noted but this particular customer I worked for before and I'm matching the bookcases that I made for him prior that are only 12 feet away from this new entertainment center project. The bookshelves need to be fixed and will be dadoed so the option of flipping them later is out. I'm thinking of using Baltic plywood with a front hard rock maple nosing and since they will be fixed shelves screw them tight through the back panel.

Anyway, thought I read here in this forum a honeycomb sandwich between shelving making them incredibly strong. I could be wrong.

Well if they are fixed it increases your load capacity. Go to the sagulator and punch in your options. 1 1/8" input ply, setup your faces, and your load. General rule is worst case for books can be 40lbs/ft.. but it can be as low as 20lbs for shorter/smaller/spaced books. You can make that call.

Ill bet 1 1/8" 60" wide FIXED mounting not adjustable, with hard maple edges will come through with flying colors especially if they are fixed to the sides and the backs.

Thanks, Mark. I think it will come through with flying colors but these are college professors and I just know they will shelf load up with books. It's always good to check with this group and of course, I'll check out the sagulator. Thanks again!

If they are fixed, put in a 3/4" plywood back with a dado in it too. That will make a tremendous difference.

Michael:

For a 1-1/8" shelf, I would dado 1/4" x 3/4" steel bar into the front edge full width, with the 3/4" face vertical. Epoxy the steel in place and trap it behind additional glued in wood blocking that is flushed up, so that when you add your nosing, it will have a full 1-1/8" wood glue face. If you go this route, you may want to change your shelf thickness to 1-1/4", and face glue 3/4" and 1/2' material together. Dado the back edge of the shelf into a 3/4" cabinet back as well, as Rich suggests, and you have done what you can do without a change of materials or design.

Overkill, maybe, but better safe than sorry. If the shelf is dadoed into the sides and back, you should be able to stand on that shelf with minimal flex. I once did a bookcase job for couple that were both NASA scientists, where the interior designer told me not to worry about structure, because the bookcase shelves would only hold knick-knacks, only to return to the job to find the entire cubic area between shelves packed solid with books, with additional books on the floor. I was lucky only insofar as the packing of books in the entire bookcase helped to keep the shelves from sagging too much, but I can't imagine it was easy to pull out a book from the bottom shelf.

That's when I learned to ignore designers. Hope this helps. Good luck
TonyF