Edge joining eight boards, one slightly cupped, should I?

[Ed Bray]

I am making a garden gate for my neighbour from my remaining Iroko planks. Last week I prepared eight boards which are 66" x 3½" x ⅞", this will give me a door of 66" x 28" x ⅞". When I went to prepare the boards this morning for edge jointing, I discovered one of them now has a slight cup along its length.

I am planning on using 8mm Dominos along the lengths of the boards to align them and using Titebond 3 to glue them up. The gate will then have 3x straight braces across the width along with 2x Diagonal braces between them.

If I put the cupped board in the centre of the panel and align it with the dominos would it be likely that they and the bracing pull the cup back into a straighter position, or, would the cupped board be likely to throw out the rest of the door? All the other boards are relatively flat. I don't want the boards to be any smaller, so if this is not a good idea I will have to machine some further pieces.

Also, not having made a door like this before, do I glue and screw the bracing on the door, or just screw it?

TIA, Eddie.

 

[Jacob]

If it's out in the open I wouldn't use Dominos or glue - the weather will pull it all apart. The other boards are likely to cup or otherwise distort once they are out in the weather.
I'd stick to trad gate construction - vertical boards (if dry to start with) with a gap to allow for expansion, nailed or screwed to ledges and braces. You could cap the top of the gate to protect the end grain.

 

[Ed Bray]

Thanks Jacob.

This is to replace a door that is already in situ and has been for 30+ years. It was been painted about every 3-4 years over this time and has rotted out in and around the places where the metal-ware has been (lock, latches and hinges), the main body of the door has survived really well even though it was made from pine T&G floorboard stock. There were no gaps left in the door and I understand that it was also glued along the joints.

My door (probably shouldn't have called it a gate) when completed will be finished with teak oil, I've called it a gate, but it is to go where this old one stood. Should I perhaps T&G the joints before attaching the ledges/braces?

Old door in situ:

 

[custard]

Regular Dominos, as Jacob said, will rot pretty quickly, but you can get "Sipo" Dominos in long lengths and cut off the length you need. It's also not difficult to machine your own Dominos out of Iroko or whatever material you want, for the 8mm cutter you'd need a 4mm radius round over bit, or cut the Domino mortice on the "sloppy" setting and use square edged stock machined to 8mm thick. Or knock up a simple jig and use an 8mm bit in a router and you've got exactly the same loose tenon operation that a Domino gives you, but without the "Festool knows better than you do" restrictions...and at a fraction of the price!

By the way, in my opinion Cascamite would be a better glue choice.

 

[Ed Bray]

Thanks, I've got some Cascamite, bought it and have never got around to using it.

Just out of curiosity, if the Dominos are inside the joints that are sealed with waterproof adhesive, how would they rot?

I have some thin bits of Iroko so may make some loose tenons from.

 

[custard]

Just out of curiosity, if the Dominos are inside the joints that are sealed with waterproof adhesive, how would they rot?

Moisture vapour still permeates waterproof adhesive, and in a typical M&T joint the differential movement between end grain and long grain means that moisture will before long freely access the tenon via cracks in the adhesive barrier but it won't dry out as quickly.

 

[RobinBHM]

If I understand correctly, it sounds like you are gluing all the boards together to make one large solid board.

The iroko will be kiln dried, which will then go outside into an environment with much higher humidity. There is quite a risk of significant movement, Its quite risky, I think a conventional t and g door would be a safer option -as Jacob suggests.

 

[Ed Bray]

If I understand correctly, it sounds like you are gluing all the boards together to make one large solid board.

The iroko will be kiln dried, which will then go outside into an environment with much higher humidity. There is quite a risk of significant movement, Its quite risky, I think a conventional t and g door would be a safer option -as Jacob suggests.

Yes, one large board.

No, not kiln dried, the planks were removed after many years as baffles in a water treatment tank and I then kept it in the garden for more years. When cut after removal from the flocculation tanks the water penetration was only about 1mm on each face, maybe 2mm on the board ends.

See here for more info: wip-old-iroko-planks-into-t84892.html

I've already used it quite extensively outside to replace outside doors and frames around my house, this was then treated with 3 costs of Sikkens Cetol HLS Plus stain and then 2 coats of Sikkens Cetol Filter 7 Plus and this has held up very well, but then it has only been in place for two years now.

 

[No skills]

Other build choices aside would it be best to run the cladding boards right to the bottom unhindered to allow water run off?

 

[Ed Bray]

It's also not difficult to machine your own Dominos out of Iroko or whatever material you want, for the 8mm cutter you'd need a 4mm radius round over bit.

By the way, in my opinion Cascamite would be a better glue choice.

Took your advice and made 110 Iroko Dominos this morning. I made them to fit the larger of the XL Domino Widths and I had to round them over with a 3/8" radius bit as I didn't have a 4mm one, but whats a few 10ths of a mm between friends. Actual finished size is 8mm x 60mm x 24mm



Quite a nice fit:

 

[custard]

Nice job, it's certainly handy to know you can always cut your own tenons, especially so with the XL. It also opens the door to overlapping the Domino mortices and making up your own wider tenons, which gives you a lot of extra flexibility when it comes to laying out the M&T's to suit your rail dimensions, rather than having to design the rails to suit the standard Domino sizes. I've often been in the situation where a rail could really do with two dominos, but they won't quite fit. However if you can produce your own custom tenons it's easy to make up tenons that are 10 or 20mm wider than standard and just shunt the Domino machine 10 or 20mm along from the first cut and widen the mortice appropriately.

For a job that requires lots of M&T joints the extended open time of Cascamite is a real help, it gives you the time to glue both the tenon and the mortice (which I believe adds about 30% to the strength of a Domino joint) and to carefully check for square.

Good luck with the gate!