[Tdevin]

I am planning on brewing a Lambic tomorrow.  I am going to ferment in a 5 gallon glass carboy using Wyeast 3278.  This is my first time using this yeast. I'm wondering how aggressive the early fermentation will be.  How much headspace should I leave?  Do I need a blowoff tube?  I am planning on pitching and leaving in my basement at around 60-65 F for 12 months or so.

7lb Pilsner malt
3lb raw wheat
turbid mash

[reverseapachemaster]

It's pretty explosive. It has several Belgian strains and they will ferment aggressively the first few days. Personally I would plan on 0.75-1 gallon's worth of headspace and use a blowoff the first two or three days.