Replies

1. 
   JohnWW | Jan 08, 2009 11:28pm | #1

   Gerry,

   If the shelves are more than three or four inches deep you should be concerned about the stresses created by wood movement.

   You can rabbet the ends of the solid wood shelves, stopping the rabbets short of the front edge of the shelf and slide the shelves over 1/2" square cleats attached to the case sides. The shelves can be left loose or just pinned at the front edge leaving a bit of room at the back edge for the shelves to expand in damp weather.

   John White

1. 
   Gerry_G | Jan 09, 2009 12:34am | #2

   Thanks for your feedback John!I was wondering about doing something like that. Do you think the 1/2 x 1/2 rabbet would weaken the shelves too much? Also there will be a back to the bookcase, which I was going to fasten to the plywood carcass, and the rear of the shelving with narrow crown staples. The bookcase is about 80" tall. If all the shelves are floating on the cleats, Do you think the unit will be wobbly? I've never seen it mentioned, but does anyone ever use sliding dovetails in plywood/wood situations like this? (Solid maple carcass isn't in the budget)Gerry G

2. 
   Gerry_G | Jan 09, 2009 05:33am | #3

   Hi John,I had another thought, a spin off of your idea. What if the cleat was a dovetail and I machined the shelf end to fit over it. That should allow for expansion and also keep the cabinet stable. I could just pop a few screws through the back to anchor it. I've never used sliding dovetails before, any pointers???Gerry

1. 
   JohnWW | Jan 12, 2009 06:14pm | #4

   Gerry,Sliding dovetails are a great idea in theory but difficult to make work. The fitting is the problem, too loose and joint looks sloppy and you won't have the reinforcement you want, too tight and the joint will be near impossible to assemble and won't slide to allow wood movement. The fit is hard to adjust because there usually isn't a simple way to fine tune the joint, you can't go in with a hand plane and shave off just a little bit.I would build the case with the square rabbeted slots and use one screw from the outside, covered by a plug, on the middle shelf to pull the sides in if that is your worry. If the plywood sides of the cabinet have a slight bow in them, which is probable, have them bow in so the shelves are a tight fit that pushes them out, and straight, when the shelves are inserted.John White

1. 
   Gerry_G | Jan 12, 2009 10:27pm | #5

   Thanks again John, I talked with my clients today and we've changed the design to go with straight banded plywood. It just seems like combining ply with fixed solid wood is more trouble than it's worth...which adds up to more expense for them.I appreciate your insight into the issue tho...thanks very much.

1. 
   JohnWW | Jan 12, 2009 11:07pm | #6

   In this case I would agree with you that mixing solid wood and plywood is making the job more difficult. To get a stronger shelf you could glue a piece of 1/2" ply onto a piece of 3/4" ply to get a shelf that would be probably be stiff enough to not need a facing.John W.

2. 
   Gerry_G | Jan 12, 2009 11:22pm | #7

   Hmmm,
   It could work, but I'd still need to edgeband it anyway. When I spoke with them they approved of putting in a partition, which will drop the shelf span below 22", allowing me to just use the 3/4" ply with 1/4 x 3/4 edgebanding. I think its one of those cases where the KISS (keep it simple stupid) principle applies. I just like experimenting with new techniques, but in this case I think the straight plywood/partition will fill the bill the best. I'll leave the experimenting to MY projects, then I'll know the limitations. :)Thanks,Gerry

3. 
   JohnWW | Jan 12, 2009 11:27pm | #8

   The shorter shelf length is an even better solution. It will also look better, shelves that are thicker than the sides of a case don't look as good.John W.

4. 
   Gerry_G | Jan 13, 2009 12:47am | #9

   Hi John, I don't know what the protocol for this would be in terms of posting, but the design changes have created another problem 4 me. The bottom of the cabinet has an interior shelf behind 2 doors. They don't want a partition in the bottom so that they can store large games etc.. in them. I'm using a dropped edge on that shelf. (all shelves will be fixed. The next shelf up will be the one upon which the partition for the 3 shelves above will rest. However, there is no partition to transfer the weight to the cabinet base. I was considering using a drop edge on the front and rear of this shelf. The doors will hide the drop edge. The remaining exposed shelves only need to be 3/4". My questions are:
   1) would the supporting shelf be up to the task?
   2) Is there a way of doing the front drop edge so that I could keep the 3/4" profile visually?I can send you a sketchup file which may help to clarify this, if appropriate.Thanks again,Gerry