Replies

1. 
   JeffKurtz | Nov 08, 2003 04:43pm | #1

   Frame and panel?

1. 
   BG | Nov 08, 2003 05:24pm | #2

   ??  Jeff, I'm not familiar with 'Frame and panel'...could you give me a hint?

   thanks

2. 
   Ricky_Yu | Nov 08, 2003 06:01pm | #3

   Since you are concerned about wood movement, I am assuming a solid lumber bottom. A rabbet along the bottom edges will not accomodate movement as you would have to glue it in place. I don't think dovetails are appropriate because, assuming the sides of your box has the grain running horizontallly, then the bottom-to-side joints will be end grain to side grain on two of the sides and side grain to side grain on the other two. As your concern points out, dovetails are more of an end grain to end grain joint so that any movement is uniform between the two members. Also, the tails or pins are more likely to break off when you do them in side grain.

   One possible solution is instead of a rabbet use a groove and trap the bottom in it dry, leaving enough space to allow for movement. However, because you're working with relatively thin material (1/4"), your groove can't be too deep. If you are concerned that the shallow groove might reveal gaps as the panel shrinks (and that will depend on your wood species, climate, and size of your panel), then you can do what Jeff K suggests and make a frame and panel. It's more stable, and your tolerances in the groove can be tighter--but make sure the panel can still move within the frame.

   By the way, depending on your dovetail joinery, you will most likely have to run a stopped groove on at least two of your sides so that the groove does not show on the outside of your piece. An alternate method is to run through-grooves and then plug the offending holes caused by the grooves.

1. 
   BG | Nov 08, 2003 06:15pm | #4

   Ricky,

   Ahhh...that is what Jeff meant by frame and panel...

   So what your saying is run the rabbit on the case and frame the bottom sheet allowing wood movement in the frame...smart.  The bottom will be about 13" wide...if I leave a 1/4" or so for expansion...??

1. 
   Ricky_Yu | Nov 08, 2003 06:39pm | #5

   If you go with the frame and panel bottom, then you won't need a groove as I suggested. You can glue the relatively stable bottom directly to a rabbet on the bottom edges of your sides. I forgot to mention this but I'm glad you picked up on it because a rabbet will take up less interior room of your box then a groove. Regardless, the panel will still "float" in the frame as stated earlier. I'm not up on my "Shrinkulator" calculations, but 1/4" seems reasonable (somebody pipe in if I'm off-base). The frame allows for more play in terms of allowances for wood movement than do the 1/4" thick sides.

3. 
   RRusso | Nov 08, 2003 06:43pm | #6

   BG,

   I wouldn't dovetail the bottom like you're thinking of doing. By locking in the bottom to the front, back, and sides, you're asking for problems. You could use a sliding dovetail front to back... If you drop in the bottom, then use plywood. If you're using solid stock, then rabbet the sides and front, but leave the back open, securing the bottom via a slot and screw or nail (also goes for the sliding dovetail). Just make sure you run the grain parallel with the front and back.

1. 
   BG | Nov 08, 2003 07:16pm | #7

   RRusso,

   What I did not include in my orginal post was the fact that this lap top desk has a draw on the right side, and a shelf inside.  The overall dimensions are about 13x19" with 6" in the back and 4" in the front...11 degree slope on the writing surface.  Also, on the right side there is a draw about 2" deep or less...depending on how much room the bottom panel takes up.  If I tack on the bottom (as the plans call for) I have a draw that is almost 2" deep ( 2" minus the thickness of the shelf, which also will act as a stop for the front of the draw).  Now that I'm droping in a bottom, I'm down to about 1 1/2" deep draw (2" minus 1/4" for the shelf, 1/4" for the bottom).  I love the sliding dovetail idea...but I don't have any skill to do that by hand...or tools that could make someting that small..

   It's a fun project..just a bit small for my big mits.  I'm doing all my resawing on the TS..that is exciting....lol

   thanks

4. 
   forestgirl | Nov 08, 2003 07:23pm | #8

   BG, thanks for asking this question, as you're getting lots of expert advice which I fully intend to file away for future consultation!!  I've been reading up on "boxes" which is, in a way, what you're doing here and it seems like plywood is substituted for solid wood bottoms these days because it so much lessens the risk of wood movement destroying the piece.

   One thing I don't think was mentioned above is that if you use a groove to capture a panel, a spot of glue in the middle of the ends will direct any movement in each direction away from that spot.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

1. 
   BG | Nov 08, 2003 09:03pm | #9

   FG,

   Yes, this is the kinda help that saves us much frustration.  I'm glueing up panels of 1/4" maple because I'm loaded with short pieces...and of course those 36" Jorge's need to start earning their keep....lol.  Otherwise, believe me, it would be plywood...

   thanks for the tip on the glue...did not know that.

1. 
   RRusso | Nov 09, 2003 09:26am | #10

   Ok, I see what you mean. Actually, I was thinking 1/8" ply, though. With something that small, I wouldn't think you'd have a problem with strength, especially if you glued it to the dividers and such, too. A few drawing pencils, pens, and paper don't weigh that much...

   Whatever you decide, make sure you post it, so I can file it away, too. :)