Just trust me on this.
I've been hunting around online and even reached out to the Museum of London and the Mary Rose Trust, but nowhere can I find a decent image that shows the bottom of one of these tankards. So I am going to have to guess.
I don't know if you've ever taken a good look at a bucket or barrel, but the bottoms sit in a groove called a "croze". Professional coopers have a special tool for cutting the croze into the barrel end which I do not posses, so to avoid making yet another tool (delaying completion yet again) and/or defaulting to my power router, I had to mark a line and cut the croze by hand.
The marking gauge from grandpa's toolbox is ideal for this. It has two sliding rules that I can set to separate depths. To scribe two lines at two different depths (the top and bottom of the croze in this case) all I have to do is set both pins and spin it around to make the second one.
As you can see, I've had to temporarily put the tankard together using cable ties. These are obviously not correct for the period, but a period cooper wouldn't need to do this step so I suppose I'll get over it.
The croze is, essentially, a dado, which is to say a groove in the wood to accept another perpendicular piece, the bottom of the tankard in this case. Incidentally, if I ever make more of these on a more generous deadline, I shall make that croze plane. Cutting an accurate dado on an inside curve is not something I care to make a habit of. This vessel is rather smaller than most antique croze tools I've seen, so I'll have to make it from scratch in the shop, hence skipping it this time in the interest of time.
So far so good. I was feeling pretty good about how things were going and forgot what Indiana Jones warned about Holy Grail about when things were going well.
"That's usually when the ground falls out from under your feet."
Bottom #1The concept is simple. A piece of wood is cut into a circle and the edge narrowed to be wedged into the croze, forming a seal. In a barrel, this is called the 'head', as in the saying 'cash on the barrelhead'. I had a large piece of tulip poplar lying around and used a coping saw to cut out a circle. Then I used chisels to cut a dado around the edge to slip into the croze.
It's not as messy as it looks in that picture. Honest. I was mid-way through the endless attempts at accurate shaping at this point. It didn't even pretend to fit. And as I whittled away more and more of the poplar, it just got worse.
Finally it just fell out and I left it lying on the grass.
The problem as I ascertained it was that because I didn't use the proper tool to cut the croze, the shape was not actually a perfect circle. I paused in my operations to clean up the croze and get a better handle on their actual inside shape. It turned out to be sort of a rounded octagon.
I took the last bit of poplar I had and used a handsaw to cut it into an octagon to better echo the interior shape of my tankard and then went back at it with my chisels.
The paring and whittling and chiseling and cursing went on for quite awhile before the wood split and I was left holding two bits of wood where only one should go. I was running out of daylight and poplar.
Time to switch woods and tactics.
Pine. It was all I had handy that was wide enough to cut a bottom out of and I was tired of wasting better wood on a learning exercise. Get a working bottom done, I decided; then you can use it as a template to cut one out of good stuff.
You know... what I should have done to begin with. Pride goeth before the autumn and it was darn well time for spring.
More later after I sort this out...