Ovolo glazing bar joint

[bunnyboiler]

I would like to install some double glazing panels (14 mm thick) in an arrangement of Ovolo glazing bars which I would make using the router cutter scribing sets that are generally available for this kind of job.

I imagine that some kind of mortise and tenon joint would be used to connect the glazing bars at their intersections (see attachment) and that the joint would be made within the rebated section of the glazing bars. Is this correct and is anyone able to offer any advice as to the details and proportions of the joint and the minimum advisable thickness of the glazing bar "fin" after rebating?

 

[GLFaria]

I would like to install some double glazing panels (14 mm thick)...

I don't know where you live, but double glazing 14mm thick overall isn't going to take you anywhere as far as insulation goes. Even assuming that you are going to use 4mm glass panes - which anyway is the very minimum - this will only allow for a 6mm air gap. Which, even if it is argon filled, will not be nearly enough for any kind of thermal insulation in whatever climate.
I never understood how people are happy with a 6mm air gap, which is nearly useless. And believe me, I've manufactured a lot of it - you've got to make what the customer asks for...

G.

 

[JanetsBears]

I don't know where you live, but double glazing 14mm thick overall isn't going to take you anywhere as far as insulation goes. Even assuming that you are going to use 4mm glass panes - which anyway is the very minimum - this will only allow for a 6mm air gap. Which, even if it is argon filled, will not be nearly enough for any kind of thermal insulation in whatever climate.
I never understood how people are happy with a 6mm air gap, which is nearly useless. And believe me, I've manufactured a lot of it - you've got to make what the customer asks for...

G.

I used to dream of having double glazing with any air gap. Now I just lie awake at night shivering, looking through my 8mm single glazed windows, curtains gentle wafting in the draughts...

 

[Beau]

Made a few windows over the years. I picked up this set of tooling for them http://www.tilgear.info/vp1382wss--vipe ... 12in-shank I made the tennon where the bearing is of the top cutter. Full width of the section and down to the level of the rebate. Hope that makes sense. May have a sample in a box somewhere if the above makes no sense.

 

[blackrodd]

The stub tenon is usually within the flat between the mould and the rebate, at the thickest part, in you're pic.
https://www.google.co.uk/search?q=rebat ... B798%3B579
The rebated piece left, although small will be supported by the glass which should be fitted after the primer and undercoat is applied but before the window is fixed.
Make sure the windows are closed while glazing in case of a slight "wind", that sometimes arises,
as this will tend to keep the shape.
Regards Rodders

 

[blackrodd]

I don't know where you live, but double glazing 14mm thick overall isn't going to take you anywhere as far as insulation goes. Even assuming that you are going to use 4mm glass panes - which anyway is the very minimum - this will only allow for a 6mm air gap. Which, even if it is argon filled, will not be nearly enough for any kind of thermal insulation in whatever climate.
I never understood how people are happy with a 6mm air gap, which is nearly useless. And believe me, I've manufactured a lot of it - you've got to make what the customer asks for...

G.

I used to dream of having double glazing with any air gap. Now I just lie awake at night shivering, looking through my 8mm single glazed windows, curtains gentle wafting in the draughts...

Slightly off topic,
Have you ever thought about Secondary glazing?
Works a treat and easy with Glazelite from B&Q
Rodders

 

[Mike.S]

By coincidence I'm currently building some French doors with ovolo moulding on frame and glazing bars, as you picture.

I took apart a section of the old doors and found that the method used was to use a lap joint where the bars intersected with the ovolo section mitred. The lap joint (right term?) was a ('fin', say) 10mm cut-out at right angles, half-way through the vertical bar and a mirror cut-out in the horizontal bar, enabling the two pieces to be slotted together to form a cross. The ovolo sections were cut at 45 degrees (i.e. mitred). Where the bars joined the rails/stiles they were scribed with stub tenons/mortices.

However, another pair of French doors I have use a different method. The horizontal rails are complete from stile to stile and the vertical bars (muntins?) are individual pieces scribed on the ovolo section and butt jointed at the rebate with stub tenons to fit into a through mortice in the central 'fin' of the horizontal bar. Sorry, that's a long sentence but hopes it makes sense.

The latter method is demonstrated in a PDF that John Brown (anor forum member) has just sent me. PM me if you'd like a copy - much clearer than my description :!:

Mike

Edit: to answer your specific question - the 'fin' on my existing bars (29mm thick) are 10mm. The width will be dictated by the cutters you use and the size of the quirk (the small stubby straight bit abutting the curve of the ovolo). My new doors will use a slightly thinner bar - 27mm - and I'll have a 9mm fin.

Edit 2 14/5/15): the joint I'm trying to describe in the 2nd paragraph is depicted in a video here (at about 9m50s in).

 

[Racers]

St Roy shows a couple of ways near the beginning of this video http://video.pbs.org/video/1427712894/

Pete

 

[Mike.S]

Pete's link to St Roy demonstrates the two methods I was describing. The video trumps my words - so much clearer!

 

[JanetsBears]

I don't know where you live, but double glazing 14mm thick overall isn't going to take you anywhere as far as insulation goes. Even assuming that you are going to use 4mm glass panes - which anyway is the very minimum - this will only allow for a 6mm air gap. Which, even if it is argon filled, will not be nearly enough for any kind of thermal insulation in whatever climate.
I never understood how people are happy with a 6mm air gap, which is nearly useless. And believe me, I've manufactured a lot of it - you've got to make what the customer asks for...

G.

I used to dream of having double glazing with any air gap. Now I just lie awake at night shivering, looking through my 8mm single glazed windows, curtains gentle wafting in the draughts...

Slightly off topic,
Have you ever thought about Secondary glazing?
Works a treat and easy with Glazelite from B&Q
Rodders

It was fitted in the house when we bought it 11 years ago but all it did was to form a void behind which masses of ladybirds gathered, having sneaked through the gaps in the old sash windows. We're hoping to renovate all the windows eventually, but the ones we've done so far we've just had to repair so they've stayed single glazed. I'm hoping to make my first complete replacement window this summer so I expect I'll be asking for advice. :wink: It's not an opening one, it's just a 2' wide by 6' tall one so shouldn't be too much of a problem (he says hopefully!) but it's an ideal candidate for double glazing.

Chris

 

[siggy_7]

I'm making a set of glazed garage doors, for the mullions (vertical rails) I used the second method that Mike.S described to attach them to the rails. I wrote up making the joints, working out sizes etc here, which includes some pictures of the end of the mullions: https://www.ukworkshop.co.uk/forums/double-workshop-doors-t88458.html I can't view the links on this thread at work, but I think the other method Mike.S described sounds like a half lap with a mason's mitre on the profile.

 

[Mike.S]

Interesting siggy, I seem to have missed your post that you link to. Note that you used the same Wealden cutters and Incra fence as I have. Latter is an excellent bit of kit which I plan to adapt to be used on a combined saw and router table set-up as you have (I don't have space for the saw at present).

Great minds think alike

 

[bunnyboiler]

Thanks to everyone who replied.

I neglected to mention that the glazing bars are to be incorporated into a partially glazed external door to an unheated vestibule. For this reason, I am not particularly concerned about heat loss although I know that building control will require double glazing.

I am trying to keep the thickness of the door as close to 45 mm as possible and this means that the viper cutter suggested by Beau would create too deep a section.

I have looked at the St. Roy video referred to by Mike.S and Racers. His cross-halving and mitre method looks very strong but, as he says, there is the problem of the shrinkage causing the mitre to open up.

I think my answer is in the Builderbill material supplied by Blackrodd which places the mortise and tenon in the rebated section of the rail.

Thanks again.

 

[dzj]

Some good drawings here:
http://forums.ukworkshop.co.uk/viewtopi ... 9&p=731989

 

[katellwood]

Some good drawings here:
http://forums.ukworkshop.co.uk/viewtopi ... 9&p=731989

Beat me to it

 

[blackrodd]

Some good drawings here:
http://forums.ukworkshop.co.uk/viewtopi ... 9&p=731989

As you say, good drawings, well found, Follow that lot!
Regards Rodders

 

[colt1954]

St Roy shows a couple of ways near the beginning of this video The Woodwright's Shop | Corner Cupboard, Part 2 | Season 29 | Episode 13

Pete

Yes a brilliant description, the best I've seen

 

[rogxwhit]

A mortice & tenon is normally sited where the flat is - where the bars are thickest, about the midpoint in the depth.

Trad bars may be mitred & tenoned (because the tenons at bar intersections are so short, some people even lap them). Or they may be scribed but the same applies.

Appearance-wise all the router cutters I've seen available are of such a profile that a slender bar is impossible, however for the larger rebate / thicker bar that double glazing needs they may be entirely suited - but the fact remains that you can't have the traditional elegance of a narrow bar with that scenario. Dg is heavier so the joints need to be correspondingly strong (think of the door slamming shut ..).

Building control may ask for dg, but more than that they may stipulate a certain u-value & it would be up to you how you achieved it.

It is possible to have full-spec glazing units to current regs made up to order with intermediate ('duplex') spacer bars inserted, and apply shallow section 'faux' bars with hi-spec double-sided tape at those positions - the duplex spacers avoid sight-through at an angle between the inner & outer faux bars, which can look awkward. This (1) achieves compliance with regs, (2) obviates the need of jointing the bars and (3) means that your faux bars can be as slender as you like.

For a door the glass will have to be toughened. Another aspect is relative cost in that glaziers have a minimum unit charge that might be based on a unit of 1/3 or 1/4 sq m, so a single unit of the full door size can be a lot cheaper.