African Mahogany Watch Box Design Questions

1) a 12×14 bottom is definitely too large not to worry about wood movement. If you have the capability, make your own mahogany plywood for the bottom – 3 to 5 layers. Might be easier to laminate mahogany veneer (shopmade or otherwise) onto plywood or MDF, both sides of course. Or use a frame and panel design, which might make the bottom thicker than desirable.

2) 1/8 is sufficient. 1/4 is thick, heavy and way overkill for the application.

-- Mark Kornell, Kornell Wood Design

A drawing might help.

-- W James Brokenbourgh Custom furniture maker http://artisticwoodstudio.com/

LSGss, welcome to LJ’s by the way. I was just going thru the posts since last I’ve logged on and followed around an interesting link.
http://lumberjocks.com/topics/44349

The target of the link points to an article of an exceptional box maker who is also a member here. If you chase around the projects and blogs by him you will see some beautifully executed examples of artwork in both the literal interpretation and craftsmanship.
At any rate, if you view his postings you might see that his sides and top are a integral glued up unit prior to separation after the glue up process. Notice the grain orientation, wood movement is allowed for by the fact that similar woods of similar grain patterns and orientations should be similar. In his blog uses a wood bottom, but it seems that there are possibilities to insert a glass pane or attach the glass by other methods. Although I personally have not tried this process / procedure I feel it offers a valuable insight into building with wood as opposed to trying to work around the characteristics and properties of wood.

I always put glass in a rabbet and glue it in place with Lexcel caulk. It is a very clear ,rubbery, mineral spirit base caulk. Takes a few days to cure fully,but remains flexible. It will not release and pull out in a strip like silicone will.
1/8 glass is fine. A 1/4 bottom( or thicker and rabbeted ) fitted into a groove 1/2” up from the bottom edge will work fine. It can be the full length on the long grain, but make it 3/16 narrower in width. Only glue or pin the center of the long grain ends into the groove. Center it so there is a slight gap on each side to allow for seasonal wood movement.
Depending on your type of construction you might need to cut blind grooves to prevent it from showing. Mitered corners will conceal it.

-- Fine Custom Woodwork since 1978

I would go with veneered ply. If the bottom is to be captured completely. As stated above frame and panel construction with a solid mahogany bottom would work as well. Quarter inch ply, which is not really 1/4” and veneer on both sides fits perfectly in a 1/4” slot.
Good luck on your build and welcome to Lumberjocks!

-- Made in America, with American made tools....Shopsmith

Here are my drawings, I typed in the writing because I have bad handwriting. I apologies if I don’t know how to draw. If you see a question mark or a range of values that means I am still deciding or don’t know, feel free to comment.

Thank you for everyone’s help.