I use the havalon baracuta for everything (same as the piranta just bigger). No need to hack through bones, just slip the blade between joints and your meat stays bone fragment free. If you go easy and don't cut bones the blade will easily last 30+ complete birds from killing, to gutting, to...
The stiff legs are just rigor mortis. That goes away after a day or 2 in the fridge. I keep mine in ice water for a few hours then stick em in the fridge for 2 days. I cut up most of my birds, so fitting in bags is not an issue. For birds to be frozen whole I cut a slit in the skin over the...
Here is a link to Kimball's blog, he describes the home made tool in detail. I made one very similar and it worked well. A few minutes soaking in very hot and soapy water will help too.
http://whizbangplucker.blogspot.com/2010/04/coming-soon.html?m=1
I highly recommend the whizbang plucker book. Lots of minor details can be changed to suit your salvaged materials. My pulleys are 18 and 2 inches. My drive shaft is 1and 3/16. My drum has a bottom and a discharge hole on the side. The exact details can vary you just need a bunch of rubber...
In my experience all the blood is out in about 30 seconds then the twitching starts and lasts about a minute. Be prepared for this because on occasion it can be violent enough for the bird to flop out of the cone. Realize that the bird is dead by this point and cannot feel anything. Use a very...
I use a big five gallon waterer for my six layers. Rinsed and filled with plain tap water about once a week they do just fine. If its off the ground high enough the water stays clean.
When I wanted to practice butchering and test my plucker I simply picked up a few cheap spent layers at a nearby livestock auction. Its easier if you aren't emotionally involved the first time. I bleed out birds for meat but beheading is fine too. The physical task is quite simple. You don't...
The plywood has held up fine through three small batches so far. My drum is the plastic outer drum from a washing machine. (don't do what I did and try using the motor and transmission from it, it doesn't work)
http://www.surpluscenter.com/ has some of the best prices for electric motors, bearings, and pulleys. Here in western PA plastic barrels are plentiful and cheap on craigslist. Look there first. I purchased my plucker fingers from cconly via Amazon and they are the cheapest and work fine (Kent...
A weekend with good weather should be plenty of time if you have a decent plan and you have all of the materials. (if you are like me there will be one or two extra trips to the hardware store near the end)
As far as calculating center height you can use an online calculator like this. http://www.handymath.com/cgi-bin/arc18.cgi?submit=Entry
Just enter the length of the panel for arc length and your desired width or height
Being able to stand may be wishful thinking though even at only 8 feet wide...
If the meat birds you are talking about are Cornish cross they will require special care to survive to laying age. If you somehow manage to get fertile eggs (possible I'm sure but not easy) they won't be Cornish rocks hybrids anymore and they won't have the same qualities.
I think we need to be honest about the size of that tank. The one pictured looks to be about 18 by 36 inches not three by five feet. (That would be a 300 gallon tank) The birds will certainly survive in there but you will need to add a cover to keep them in. Seems like a crappy life to me...