New yeast, or pitch on cake? Tripel formulation

Formulating a tripel here.... I want to be somewhere between a Duvel and a Maredsous 10, but if I come up with a new, signature tripel, so be it. As long as it's good! Which brings me to yeast:

WLP570 is said to be Duvel's yeast. Awesome! However..... I am doing a Biere de Garde on 12/14 that I already have a starter of WLP550 rockin' out for.

Based on those links, do you see any reason why I shouldn't do about a 3 week primary (want to do tripel on 1/3/09) on the BdG and then pitch the Tripel on the 550 yeast cake? I'm looking at about an 8.5% tripel, so pitching on a cake should be nice. But flavor and character-wise.... Any reason that either yeast shouldn't produce a nice tripel?

Looking at this (my eff% is less than 60 for now, may adjust later as I just got a mill):

13 lbs. Belgian Pils
2.5 lbs. Cane Sugar

1 oz. Styrian Goldings (Pellets, 6.00 %AA) boiled 60 min.
0.5 oz. Styrian Goldings (Pellets, 6.00 %AA) boiled 15 min.
0.25 oz. Saaz (Pellets, 5.00 %AA) boiled 2 min.

White Labs WLP550 or 570

Thoughts?

Ok, well I'm going to pitch on the cake.

How about taking some of the slury from the BdG, washing it, and using an appropriate amount of yeast in the next pitch? Yeast cakes would most likely be serious over pitching.

Mr Malty Pitching Rate Calculator

+1. Knocking out onto a yeast cake is significant over-pitching. One of the most objectionable symptoms of over-pitching is a noticeable lack of esters. One of the most desirable aspects of Belgian ales is the yeast ester profile. Do the math.

Harvest 50% more yeast slurry than Mr Malty tells you you need to properly pitch your Tripel. That'll give you plenty of slurry, even considering viability loss with a week's storage in the fridge.

Cheers!

Bob

Hmmm.... I always thought that pitching on a cake was desirable, especially for a high alcohol beer like this.

I'd honestly rather bottle the week before brewing the tripel, so I am inclined to just buy some 570, make a starter, and go with that.

Whichever you decide.

Sometimes knocking out onto a cake can perform a valuable service. I have in mind big beers like Imperial IPA, where yeast esters may be undesirable. But with beers in which a significant portion of the requisite character is provided by esters, you need to pitch a more measured amount.

Yeast create esters during the growth phase, when the initial inoculation population reproduces to form the colony which conducts the greater ferment. Over-pitching - or knocking out onto a cake - makes this reproductive phase unnecessary, as sufficient active cells already exist to ferment the available sugars.

Of course, this leaves aside the horrid idea of putting fresh wort into a fermenter crusty with detritus from the previous fermentation; I know others report no problems, but I just can't wrap my brain around putting fresh wort into a vessel I haven't cleaned.

You can quite successfully brew a Tripel with the yeast you've already got. You'll retain the lion's share of viability if you simply harvest some slurry of your healthy WLP550. But it's your beer!

Cheers,

Bob