I am currently conducting an experiment that may interest followers of this thread. 2.5 weeks ago I brewed 35 liters of wort using GordonT's recipe for malt/sugar with wheat and oats chosen 50/50 malted/unmalted, Hallertau Mittelfrueh hops aiming for 20 IBUs, spices as suggested by GordonT. Late addition of sugar (after 8 days) as also suggested by GordonT. Initial gravity of the wort was 1072 (calculated). I split the wort in 25 liters + 10 liters. The large batch is fermenting with original Bosteels yeast, harvested from 4 bottles of fresh Tripel Karmeliet. The smaller batch is meant as a reference, and is fermenting with a neutral all-purpose dry yeast, for which I chose Nottingham. After 10 days the SG of the batch with Bosteels yeast dropped to 1021, whereas the reference batch with Nottingham yeast was already at 1012. Taste of the Bosteels batch was better, more mellow. Too early to say if it will be similar to commercial Karmeliet.
The high SG for the Bosteels batch makes sense, as we think that the Bosteels yeast has a low attenuation. I measured FG of commercial Tripel Karmeliet last week, and it was 1016, which is high for a brew with 6% sugar in the mash. Kwak, another beer by Bosteels probably fermented with the same yeast, has a FG of 1020 with an assumed 10-16% sugar in the mash (http://www.homebrewtalk.com/f14/kwak-beer-252114/index2.html). I find these high FGs somewhat confusing. Any suggestions?
I will let the beers rest for another month, and then put them in kegs an bottles. The bottle conditioned ones will be the most interesting for the experiment, as they will resemble commercial Tripel Karmeliet the most. Final judgement expected in September. Keep you posted!