It's here!
It's cheap!
It's easy!
It's funny!
IT WORKS!
Buy this - set of 3 for £7.80:
http://www.amazon.co.uk/gp/product/B001 ... UTF8&psc=1
Then, here we go:

Notice hyper-expensive foil tray from Morrison's. £1.60 for 10...or is that 20 ?

Now, place a charcoal holder on one side of your kettle. And place a charcoal rail next to it, leaving a gap of an inch or so:

Place two of the trays in that 1" gap:

Notice that the charcoal holder has been pushed right up to one end (in this case furthest away from you), rather than central.
Fire up a Weber Chimney Starter * (small, portable job) full of briquettes:

Empty the briquettes into the charcoal holder, add wood chips. Now place the third stainless steel tray over the charcoal, with the Morrison's foil tray** on top:

Think about it - what is a smokenator? It's a stainless steel barrier to hold your charcoal behind with some holes in it to allow heat through indirectly, with a water bath.
Job done for less than £8.
Notice that the trays are exactly the right size. On their sides they fit almost perfectly between the charcoal grate and cooking grate. On its back the top one covers the gap between the edge of the kettle and the charcoal grate.
Does it work? Well, the ribs were delicious. I need to experiment a little more. I made the schoolboy error of introducing a new variable whilst trying this, as I used Heat Beads instead of my usual Weber briquettes.
Because of this I used a few too many briquettes (in this case 30), which gave an initial temperature of 160c. I did a 'faster' variation on 3/2/1 as the rack of ribs was quite small. I halved the timings to 1.5/1/0.5. After 1.5 hours when I foiled that was down to 150c. After a further hour when I added sauce it was 140. By the end of that half hour, after 3 hours in total, it was 130c.
Next time I'll try 25 heat beads briquettes.
Steve W
* Other chimney starters are available. But let's face it, they're pants.
** Other foil trays are available. But not at Morrison's.
SW

