abbey dubble...

Hi all - this is my first posting here and very confident some of you can really help me on this.
i am planning a 5.5 gallon (UK) batch of something similar to a belgium abbey dubbel (about 8.5%ish). i have a recipe and am planning to re-culture some yeast from 4 bottles of Chimay Bleu (that'll be fun after 4 bottles!)

i have a few questions that no doubt you guys will be able to help me with:

1 approx how long will it take to culture enough yeast from the bottles ready for brew day? (& can i use household sugar for this or is malt extract best?)

2 how much yeast shall i pitch? i'm thinking about 70 grams of slurry but am worried thats too much?

3 how many degrees of attenuation is correct to bottle at and condition it well? i don't want the beer too dry, too flat or exploding! planning to start at 1078 or so, i need a racking grav ( am aiming for 1011ish?) and/or %  to transfer and lager at, and then a final bottling grav so it will secondary condition (or are they the same?) en bouteille. whats the best attenuation to profile/procedure in terms of stages, process and time for brewing/racking&lagering/bottling this kind of beer etc. i have a walk in fridge constant at 12.5 degrees C i can store at.

I have some good experience and have brewed many successful beers - but have never quite cracked bottling and never tried anything of such standard as a decent abbey style beer.  (i'm now an expert in brewing sanitation, i've lost one too many batches of good booze to those pesky critters -and only one!)

please and thankyou!

Hey Somerset,

I am not sure I understand what your doing?  Are you collecting the yeast from the four bottles to pitch into a fermenter?  If so, I would brew a mini-wort (around 1quart) at around 1.040-50 an create a yeast starter to be used for the 5.5 Gal batch.  I would make the starter about 2-3 days before the main batch.  I would use Dry malt extract to make the yeast starter wort.  This would allow your yeast to get started before you pitch it into the (relatively) high gravity wort of the dubbel.  It would also test out the viability of the yeast you collected.  If you don't have a good fermentation in the starter, then you might want to consider a 'plan-b' for the yeast.

Before you bottle, make sure the fermentation has completed in the fermentor.  The bottle conditioning fermentation should be from the priming sugar, not the fermentalbles of the original wort.  This will keep you from creating bottle-bombs because you can control how much CO2 is created by how much priming sugar you add.  The amount of attenuation will be based on the the mash profile.

Did I help?  Are there other suggestions from people?

yes that helped -thankyou. i have a plan B for the yeast because i have read about the problems of using old yeast. It is a Chimay Yeast from a batch bought in Belgium recently so i am hopeful!
with regards to CO2 in the bottle i agree that priming is probably better (safer!) How much would you add to a pint bottle and would you recommend repitching some yeast into the bottle too? If so i imagine its only going to be 2ml or something?
thanks for your reply -its the only one so far!