I had the day off, so I went and bought a half rack of fat tire and a bottle of HEET to try the alcohol stove thing out. Built a "penny" stove, not into the priming/waiting thing. Built a double walled tricky pain in the neck deal, simmers 12oz water in 6-7 mins after gettin up to speed. So I do some research, try and refine it a bit. Not impressed.
By this time I've consumed enough beer to make all that work look pretty silly, so I do the 2 minute cut the can and punch a bunch of holes in it thing (like on the zpacks site), and this thing simmers the same pan of water in 6 minutes, no waiting for bloom.

Did I do something wrong (likely) or is the double walled v8 thing a bunch of work for no appreciable gain?

There's no way to know w/o knowing what the conditions were for your test. Ambient temp, water temp, wind conditions, windscreen, amount of fuel used, etc...

I've built many, many more dozens of pop can alky stoves than I care to admit (was a full on alky-addict for over a year, built four or five a day sometimes) and for an open jet kind of stove, I could reasonably expect to boil 2c of water (about 500ml)in about 5mins, with about an 8-10 minute burn time. Starting with bout 60f degree tap water, at about 50f ambient temps.

I kept notes, but I have had some much faster boil/burn times, and some really slow ones. Google mini bull designs sst if you want to see a fast boil time. I built one, and it was a bit frightening. The mbd nion style stoves I've found to be the most efficient, but slow. I could get a 2cups boiling in about 12 mins, but the stove would keep simmering for nearly 30mins on that same oz of fuel.

Most important with an alky stove is to have a very solid windscreen. The slightest breeze will destroy stove efficiency without one.

My #1 reason for using an alky stove is cost. You can't get a cheaper stove with a more available fuel.

BM

The windscreen setup is (to me) more important than the stove itself. I spent allot of time tweaking it and then many tries to get a setup that works on different terrain from grass, to rocks and dirt. The open burners work great but just use more fuel that the jetted ones. For about a year, I used the last inch of a beer can and just poured alcohol in it and lit it. No wait, and I could burn small trash in it when I was not cooking. I had problems with the stoves that acted as their own pot stand because when used on uneven ground it was a joke. Sure, if I looked around, I could find a good spot, but I want to cook in front of my tent while in a sleeping bag. It just takes some time to find a good setup that works for you.

Welcome to reality.

Cheers
PS: windscreens ! ! !

A pity we can't clone Roger Caffin but adjust the clone to prefer alcohol stoves:
then the depth of investigation applied to gas stoves would be applied to alcohol stoves, and then perhaps they could "catch up" (with gas stoves).

:)