Butters,
I doubt you could get FG 1.018 with and OG 1.040 even if you planned (except if you added lactose). Churchys beer has for some reason stopped before ferment has finished. Bottle bombs will most likely result unless vented or drunk quickly.
cheers
darren
Short answer is "********". Of course you can.
Longer answer is, I get 1012 consistantly from an OG of
1026-1028, even when using Nottingham....because I mash a specific way to force it to do so. If you know how to manipulate your mash in that fashion, to favour the production of dextrins over maltose, you can drop your apparant attenuation from the projected 70 (ish) % down to as low as 40% (theoretically. That being said, I've never been able to drop much below 50%).
Have a look through literature for "jumpmash" aka "springmaischverfahren"
Various special mashing programmes are used in Germany (Kunze, 1996; Narziss,
1992a, b ). In the jump-mash system (Springmaischverfahren), which is used to produce
wort with a low fermentability, a thick mash is prepared at 3540 C (95104 F). Then
boiling water is stirred in over a 15 min. period to give a temperature of 72 C (161.6 F).
By this means the grist is hydrated and some of the thermolabile enzymes have a chance
to act before the temperature is increased to permit starch liquefaction and dextrinization
while minimizing saccharification. The mash temperature is increased to about 78 C
(172.4 F) before wort collection. The wort has an attenuation limit of only about 40%.
From Brewing- Science and Practice, 2004.
The main difference between this deliberate technique (which works on a HB scale, I know, I've done more than half a dozen of them), and the accidental result achieved by the OP is the pre-hydrolisation of the grist into a thick mash (0.1L/Kg above grain absorption). Either way, denaturing of the beta amalyse accounts for reduced fermentabilty. Another method available is the Kubessa process, but this is very different.
No such thing as imposible, if you think outside the square.
edit to remove smiley that somehow came into being of it's own accord through cut and paste.
edit v2: that being said, I maintain my opinion that
unplanned low attenuation should still be treated with caution as far as bottling is concerned.