We did a contract milling job for a local school this week, which involved a double ended chainsaw mill with an 84" bar, and a lot of effort!
It was a good experience, and went according to plan. Priced as a three day job, the cutting was done in two leaving me to shovel sawdust at a leisurely rate on day three.
Two men, two days cutting, and 415 hoppus foot of boards produced. About 250 cube of that was at 2", with the remainder at 3 and 4 inches.
Technically it was a bit of a challenge with the first log. The first cut was started at pretty much head height, which meant that we had the inevitable rise and fall in the cut at the start of the cut, which migrated slowly down the log as the cutting progressed. With the sheer weight of an 84" mill set up, and nature of starting a cut 6ft off the ground, I'm not sure how to avoid this practicably. Given that there is no other way of cutting a log like this, I think it's a far trade off.
The cutting was easy and quick with the double head set up. We were getting a consistent cut rate of 3ft/minute through full width (65-67") cuts. The real challenge is having the patience to take the depth gauges down enough. I need to start pleading with chain manufacturers to produce ripping chains for people with high power output saws (or indeed two of them) because a stock chain is like trying to run a Ferrari V12 through a Ford Fiesta gearbox - you cannot realise the power. I must have taken about 25 stokes off every depth gauge, and it could still stand to be much lower. Either way, on a 13 ft cut, we were getting 3 cuts to a tank.
So, as ever, I'd strongly recommend that for anyone doing any large diameter chainsaw milling, ditch the single head set up and get a double headed mill. It's not twice as quick, it's four times as quick. You save fuel (I used 20 litres to produce 415 hoppus foot), chain sharpening, stress on your machines, stress on you and lots and lots of time.
Photos (apologies for the lack of mid cut photos - our promised help didn't really materialise, so we could only photograph when not cutting.