Haunched or not?

[stuartpaul]

I'm about to start on a set of panelled garage doors and I've been trying to work out wether I need to use haunched M&T's or not? I wasn't going to considering 'plain' ones acceptable strength wise.

Basically 100 x 50 stiles with 150 x 50 rails. Looking to use 70 mm deep tenons.

If haunched are best why?

 

[deserter]

You'll have to haunch the outside tennons, other wise you'll end up with bridle joints. Also a point worth mentioning is that on a 150mm rail your going to want a double tennon, so basically you'll have tennon, haunch, tennon, haunch on each joint.

 

[andy king]

You'll have to haunch the outside tennons, other wise you'll end up with bridle joints.

No, you can still make the tenon narrower to allow it a proper M&T, but a haunch is definitely the way to go.
The haunch is designed to keep the rails from twisting or moving, locking the full width of the rail into the stile.
One other advantage usually overlooked, is water integrity.
If there's any breakdown in the shoulderline, without a haunch water will wick through - the haunch prevents it. (depending on your construction - a rebate will still give integrity, but if its a grooved one for panels then there's the chance it can still let water through)
As pointed out by deserter, wider tenons will need to be made as doubles - middle rails are usually tenon, haunch, tenon, bottom rails are tenon, haunch, tenon, haunch.

HTH,
Andy

 

[stuartpaul]

I think I'm understanding!

Found this:

http://www.geoffswoodwork.co.uk/mortise01.htm

Which I think helps make it a bit clearer?

It's what I'll be following when I start tomorrow.

 

[Sawyer]

Haunches also give you a much stronger glue line. Otherwise, the un-haunched part is just end grain glued to side grain, which has very little strenght, no matter how good the glue is. For something like a garage door, you want to build all the strength you can get into your joints. I'd also through mortice and wedge them - stronger still.

 

[deserter]

I'd agree with the wedges or alternatively draw bore them.

 

[Jacob]

Haunches also stop what is sometimes called "lipping" - where the faces of the rail and stile go out of flush for whatever reason.
The haunch needs only to be as deep as the tenon is thick i.e. square in plan, unless there is a slot, rebate or other detail to take account of.