Cope and Stick vs half lap joint

[Edward P. Surowiec]

I'm designing a Guitar Case cabinet with humidifier. The two glass panel doors will have a 2 1/2" frame. Each door is 61"tall X 18 1/2" wide. I am concerned about corner joint failure and racking. Is a cope and stick joint strong enough to keep the door square or should I add a half lap joint over the full 2 1/2" door frame in addition to the cope and stick joint??:confused:

[Gene Howe]

I'd go with half lap. You could add through pegs, too. I'm assuming the rails and stiles are 3/4" hardwood. In which case, I wouldn't think you'd need to layer it.
I'd also give some thought to some very strong hinges. That glass is heavy! You might consider a center rail so you could use some sort of long leaf hinge in 3 places.

[pat warner]

I think the lap (p://patwarner.com/images/dovetailed-lap.jpg) and cope & stick are mutually exclusive. If you can make a sample I'd very much like to see it.
And, I agree with your concern. A shallow router cut C&S is under rated for medium weight doors.

[John TenEyck]

You could add a loose tenon at the stile/rail intersections to increase the strength. That will give your the same strength as a mortise and tenon joint while still allowing you to use the cope and stick. You should have room for a 1/4" tenon even if the stick is more than 1/4" deep, by off-setting it a little closer to the back side.

[Neal Clayton]

i agree with mortises/tenons for longevity, and use them on everything i build simply because it's considered the 'right' way.

but they are, honestly, superfluous in many cases...

glass isn't weak, glass is actually incredibly strong because it resists flex and cannot compress edge to edge. you can build windows exposed to the weather without any fasteners on joints other than nails and glass coupled with glazing putty will hold the sash together for decades.

so here's my opinion, as someone who builds windows and doors (which must be flat as yours must be, and must stay that way).

a) the wood structure needs to be dead flat when you assemble it and glue it. use whatever means you have to with cauls or weight to achieve that.

b) while it's clamped up flat, set your glass in a bed of clear caulk or glazing putty with glazing points before you remove the clamps. typically a glass rabbet is 3/8 x 3/8, that'll leave a quarter on the inside to trim. i use a point gun (http://www.amazon.com/Fletcher-Terry-Co-Point-Driver-07-500/dp/B000DZF41W) for window sashes but there are hand driven points available from window hardware suppliers if you prefer.

once the glass is set and points set to hold the glass in place, and if that was done while the door was flat, the glass will hold it that way.

this is assuming your door will have true divided lights, of course, which results in smaller, and therefore more rigid, panes of glass. if not you could always use thicker glass (a bevel is always nice ;)) to compensate.

either way the glass is the source of strength for any type of window, be it an actual window or a cabinet door with a window, not the wood.

[Russell Sansom]

Thanks to Neal for a lucid explanation. I'm ready to head to the shop and put together a glass door!

[Mike Schuch]

I have added dowels to cope and stick joints when I have been in doubt and often even when I am not (They are great for keeping everything aligned while gluing). I have a horizontal boring machine which makes dowels very easy. I will usually drill for the dowels before shaping the rail and style and just add about a 1/4" to the depth of the dowel hole to make up for the extra depth of the joint.

[Curt Harms]

Freud makes an adjustable cope & stick set that can cut tongues as long as you'd want. I've seen the set demoed, I've never used it myself.

http://www.freudtools.com/t-PremierRailandStile.aspx

This set will make the extended tenon. I assume you'd need to make the deeper-than-standard mortise the old fashioned way. Of course, you could make a bridle joint and have the surface area of a half lap with the appearance of cope & stick, it seems like.

[Peter Quinn]

I agree very much with Niel about the glass adding strength. I do like a frame that can hold together though and don,t consider cope and stick sufficient for large panel or sash doors. A few dowels or a loose tenons would add the strength to keep things together over the long haul. A little clear silicone bead between glass and rabbit before adding the stops will certainly allow the glass to add rigidity to the frame and avoid any rattle. Remember to finish the frame before getting near it with silicone!. A half lap frame would certainly be strong enough but I don' understand how this can be combined with a cope and stick set?

[John TenEyck]

I can't argue with the guys who do this for a living, but glass will only add rigidity against racking forces, not bending or twisting. Glass is incredibly stiff and strong, compared to wood. However, it also is very brittle while wood is more elastic, and if you subject a sheet of glass to even small bending or especially twisting forces, it will break. So the key is to make sure your frames are dead flat with just normal clamping. If you have to force the frame flat through any extra means it is likely to break the glass, sooner or later, as the wood tries to spring back to its original shape. In a flat frame, a glued in piece of glass will add a tremendous amount of racking resistance.

[Edward P. Surowiec]

Thank you for all of the good replies. Some folks picked up my error of implying that the cope and stick profiles would be combined with a 1/2 lap joint. Ishould have said that the cope profile on the inside edge of both the rail and stile would be cut at 45 deg to form a square inside corner then a 1/2 lap would be cut on each of the rail and stiles.
Thanks again for your help.
Ed