Joy of Sectors II: Revisiting "The Arte & Misterie of Coopering"

You may remember this picture of a persnickety Perkins working the angles on a coopering demonstration.

With a bit of math and the able assistance of my consulting engineer, we determined that the eight perfectly-equal staves of my Mary Rose tankard needed to have 67.5 degree bevels so that they would align to form a perfect circle of watertight, oaky goodness.

This assumed if you didn't round off your tankard/bucket/barrel or whathaveyou that you'd have an equilateral polygon. All sides (eight sides in this case) were the same and would be worked with the typically-modern obsession with precision and symmetry.

As we discussed yesterday, that wasn't quite right. Coopers make their staves whatever width their wood allows and it's not always symmetrical and there aren't always an even number of staves. This is important since they were cutting wood straight from the log and doing a lot of their shaping with an axe. (Axes are awesome and speed up woodworking considerably, but they're not really precision instruments.)

All of which throws off my equation a bit. You could still figure it out, of course, but it just got a bit harder.

Part of the problem here is that I tend to think of barrels and tankards as segments of a ring rather than pieces of pie. I've been peeling all these apples, so let's make a pie.

Not a meat pie, you goofball, an apple pie.

Much better. (The ice cream's a nice touch, but we won't be needing it today so I'll just eat it and get it out of the way...)

Like a period tankard or bucket, the average pie slicing cook isn't going to make every slice exactly the same size. The piece for the baker is big and the piece for the kids are small. Also Aunt Agnes, who always says she's on a diet, but takes twice as much ice cream as everyone else.

The nice thing about this way of imagining a coopered vessel is that you could (if everyone can hold their forks for a minute) rearrange those pieces any way that you want and you'd still have a pie the same size as you started with. The pieces would all fit together no matter how you rearranged them in the pie plate.

But with coopering, you're starting with a pile of uncut sticks and an entirely imaginary pie that you're trying to craft out of thin air and oak. So how do you do this when you don't start with a pie?

Enter the Sector.

If you remember, at its simplest form, the sector is two straight pieces of wood hinged at one end. Pretty much exactly like a pair of dividers, except made of wood.

The geometry of the sector is devilishly simple: The two legs are equal, meaning that the legs will form an isosceles triangle. If you place it at the center of your imaginary bucket (or whatever you're making), it forms an imaginary piece of pie. If you want to make a ten-inch bucket (measured across the bottom) you just mark your sector five inches from the hinge.

That's the inside diameter of your bottom.

The second mark you see there indicates the desired thickness of the walls of my imaginary bucket.

Now, no matter where the sector crosses the the outer wall of your bucket, or how far apart the the legs of the divider have to be (to accommodate your rough-cut variations in stave width) the legs form the angle that you're shooting for. 

You found your stave bevel without writing a single number on a single piece of paper.

As you can see, this is also helpful if you decide to repair or knock off an existing bucket.

But wait, there's more!

It's not just a measuring device for finding the angle of your bevel either. It's also a jig you can use to monitor your progress as you create the bevel on your staves. Hold the bevel up to the stave as you work and align it to your marks as you go. 

The angle of the sector will tell you how far you need to lean the stave over as you plane the bevel. When the stave sits snugly in the sector between the marks, you're golden.

The importance of this cannot be exaggerated for the working cooper. And this is the part that I forgot when I was doing my demonstration.

I almost wish that building that bakery at the Washington Midsummer Renaissance Faire had been the first step in this project rather than happening in the middle. I suspect that I've fallen down on most of these projects simply because I'm thinking in terms of one-off bespoke items rather than the economies of production.

The practicing cooper isn't making one bucket at a time. This isn't bespoke bucketing on Bond Street, it's mass production because a cooper (and his apprentices) gotta eat. So if they're making as many buckets at a time as they can reasonably get away with, there's no room to be fiddling about with equations and making these exacting symmetries that we've become so accustomed to post industrial revolution.

A cooper's shop is making piles and piles of rough-cut staves and assembling them into a pile of ten-inch buckets and they all have to fit together no matter which bucket they're getting shoved into.

Yesterday I asked where I should stop. I don't know that I'm going to go back and repeat every experiment and demo that got us this far, but going forward I will certainly be taking a hard look at each of these trades and asking the question that should be obvious: How did they do this fast enough to make a living at it?

Because therein lies the real secret of most of these trades.

Now go eat some pie. You've earned it.

-Scott 

Postscript

The "Aha!" moment for this didn't come from thin air. (They never do, no matter what anyone tells you.) I've been reading about sectors recently, mostly using Jim Tolpin's books and articles so I was in the right mindset when I had the good fortune to catch an episode of Roy Underhill's "The Woodwright's Shop" featuring white cooper Norm Pederson who actually demonstrated many of the things that past coopers on that show had previously waved away as "something you learned with experience."

The episode is not available online anywhere I can find it, but you can download it for $3.99 from Popular Woodworking here: https://videos.popularwoodworking.com/courses/the-woodwrights-shop-s24-ep04-norm-pederson-white-cooperage  

Or you can buy the whole season on DVD like I did. I highly recommend it if you have any interest in trying this out yourself with better results than I had on my first outing.

Further watching...

This is not that video, but it's an excellent demonstration of white cooperage filmed at an outdood event, so the sound isn't always so great.

Thoughts from the peeler: The artisan obsession and where does it end?

There is in just about every artisan, a touch of obsessive compulsion. Whether or not it's a disorder depends on how you feel about being both obsessive and compulsive at the same time with sharp implements in hand.

I don't want to make light of a genuine medical disorder. As someone who suffers the black periods of lost joy and time that is depression, far be it from me to make light of someone else's affliction.

Obsession and compulsion exist on a sliding scale, which is set by the same people who have categorized an affection for coffee as a mental disorder.

So let's ignore those folks for a bit.

For all practical purposes, it boils down to whether your obsession/compulsion is positive or destructive influence on your life.

Be ye moderate in all things except moderation.

So it is with caffeine and beer and so too it is with handicrafts.

But where is that moderate line? When do I stop? How far do I take each of these explorations of a craft? When do I tie it off and call it good? Do I keep going until I've got it perfect? Is perfect the enemy of the good?

I discovered recently when I began exploring the uses of the sector, that I was wrong in a very important way when I discussed the many ways for finding the angle at which the staves of a bucket or tankard meet.

My methodology was modern. For one thing, we started with an equation. For another, it depended heavily upon looking at the tankard as an equilateral polygon and we did some really sweet math based on that assumption.

That was an inaccurate assumption.

Even though it worked.

As I examine more coopered buckets and tankards, it because clear to me that the old coopers didn't think that way. The staves of a bucket are rarely all the same size, and no two identically-sized buckets seemed to have the same number of staves.

My math was accurate, but my method was wrong.

The period method is really cool. It's easier. And it involves a sector and some different neat math having to do with isosceles triangles and dividers.

My assumptions were wrong and even my successful result was... I don't know. Was it a failure to achieve the goal by apparently modern means?

A period item was created, but it was based on best guesses made with a modern mind. My methods of arriving at that item were modern even though I used my best period tools to achieve the result.

I know all of this because I didn't finish exploring coopering when I finished writing about it. I kept going. I kept talking to other coopers. I examined barrels and buckets in antique shops. I made a bucket. Then I made a butter churn. Then I repaired some damaged buckets and barrels and tankards back to working order.

I know I was wrong because I didn't stop.

I made an ale pail that would hold ale, but did I succeed or did I fail.

Sorry, that was Seussical. Sometimes I can't resist.

At some point do I stop going back and adding to these projects?

Or is this exploration of artisans a reflection of artisanship itself in that the learning never actually ends? And if that's so, is my quest really impossible after all? Will I ever have more than the most surface knowledge of any of these crafts if I cannot devote more than the duration of a few blog posts to each of them?

How do I know when to stop?

And if I'm honest with myself, can I stop even if I want to?

- Scott

My Staves Are Numbered: Making a Mary Rose Tankard Part Four

I forgot to mention one of my mistakes in that last post, but that's okay. I didn't need to dwell any more than I did and thankfully, it's not like hide glue wasn't available in the 16th century*. Oak is a cantankerous wood and tends to be ultra-dense and sturdy except when it isnt, and when it isn't, it tends to be at the worst possible moment.

That chunk missing from stave #8 is not intentional. It's the result of a slipping chisel and a fault in the oak that was just ready to slip.



It will be repaired after the tankard is fully assembled.  Which brings us to numbering the staves. It almost seems logical to just number them one-through-eight, but that ignores an important fact of handworking wood: each side of each stave is different.

So, as you're fine-tuning each stave to match up to the one next to it, it's important to number the joints rather than numbering the staves.

Stave 1-2 matches up against 2-3, which matches up with stave 3-4... etcetera.  On the bottom, that means numbering the points of the octogon. The bottom too will need to be individually trimmed and scraped to fit into the croze.

The tension of the wood as it swells (as it will when it gets wet) will push against the hoops, which will push back and that tension will seal up any miniscule gaps left.

And that's how coopering works!

I hope.

Anyway, as you can see, every piece is complete. You can see in the picture above, the lid and handle are complete and it's all ready to go. Come what may, leaking or not, this ends tomorrow.

~Scott

-----------
*Speaking of 16th century glues, I was recently gifted with a copy of "Il Libro dell'Arte" (The Craftsman's Handbook) by Cennino d'Andrea Cennini by one of my readers. For the record, I don't court such random acts of generosity but I approve of them wholeheartedly. Thank you Noel Gieleghem for the kind gift and your support past and present. I have already put it to good use!

The Man with Three Bottoms: Making a Mary Rose Tankard Part Three

When I get stressed, I make things. Yesterday I made mistakes. But they were 100% lovingly hand-crafted mistakes, so at least I have that going for me...

Incidentally, if you ever want to try doing this, a book I recommend that you get your hands on is called "100 Keys to Preventing & Fixing Woodworking Mistakes" by Alan and Gill Bridgewater. There are probably a thousand books like it, and you're going to need at least one.

Just trust me on this.

Bottoming Out

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 #1

The 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.

Bottom #2

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.

Bottom #3

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...

~Scott

The Arte & Misterie of Coopering: Making a Mary Rose tankard, Part Two

This being the part where we turn math into a drinking vessel...

You may remember this bit of algebra from last week. Contrary to what I've been seeing on an alarming number of YouTube videos and woodworking forums, it's the way to find the correct angle to cut your bevels on the staves of your bucket/tankard/butter churn, or whathaveyou.

n = the number of staves you want in your vessel.

And it doesn't change no matter how big or small your vessel gets.

There seems to be a lot of confusion about that out in the Interwebs. The angle is the same whether you have a diameter of ten feet or ten inches or two inches. For an octogon (or an eight-piece circle) the angle for the cut is 67.5 degrees.

Geometry is awesome like that.

The mystery of the bevel solved, it only falls to us to decide how to cut that angle accurately. As I said in the lead-in to this project, every source I have just says "the cooper eyeballed it." And the tool they used for that eyeballed angle was a big jointer plane mounted upside down on the floor of their shop.

You can see one being used in this engraving from my muse and tormentor Jost Amman. That's one seriously large piece of equipment. I checked around and those things are expensive even if you make your own (mostly the cost of getting the blade made).

Image source: Wikimedia Commons
Cleaned-up digitally by yours truly.

You can see it in use in this video I posted the other day of Ramona Vogel, journeyman cooper at the Colonial Williamsburg living history village: http://vimeo.com/11313428 I think that beyond some basic geometry, the real "art and mystery" here is how to finagle the right tools to make it all work.

Thankfully, the woodworking blog I got that video from (The Village Carpenter) came to my rescue once again with this post about a friend of hers who makes buckets.

He doesn't use a huge floor-mounted jointer; he uses a hand plane mounted upside down and it seems to work just fine. He also uses a jig, but I wanted to try my hand at this "eyeballing" thing that everyone seems so impressed by, so I grabbed my largest bench plane and a handful of clamps and my eyeballs this is what I ended up with...

I've already leveled the sole of the plane, now I'm making some fussy adjustments on the blade.

Taking the first few swipes across the blade.

Note that I'm wearing a glove on my pushing hand and keeping my fingers well back. I want to keep my fingertips on my hand and not on the ground where they'd get dirty and I'd have to hire someone to sew them back on...

Thankfully, the upside down plane worked a treat and I didn't so much as trim a fingernail on that razor-sharp blade that made such short work of that dense oak stave.

Take another look at the Mary Rose tankard we're imitating here and you'll note that the top is narrower than the bottom. Sort of an inverted pint glass shape. So I have to not only trim a bevel on either side of each stave, I needed to make each stave slightly smaller at the top than at the bottom. 

Forgot to mention that I also made it thinner when I was shaping them on the shaving horse. The intent being to give a more substantial foot to this thing since it's going to be quite tall and on the rolling deck of a ship no one wants to spill their beer.

The tool I'm using to check the angle in the photos below is called a sliding bevel.  I pre-set it to the correct angle and locked it off. I've only to hold the piece up to the light and slide the blade of the tool along the wood, watching for gaps.

  

I tried to find out how they did this in the 16th century. A lot of tools like dividers and the like predate the period, but I can't find anything concrete on the topic of the sliding bevel. If anyone has anything on this, I'd love to hear it.

The results are eight staves, evenly shaped to form a circle which will, under compression from its hoops, swell to become water-tight.

It's almost but not really discouraging to note that if you have a sliding compound miter saw, a couple of router bits, and a table saw, this project really would take you an afternoon. But it wouldn't be nearly as cool as this one.

Or so I keep telling myself...

Still a lot of work to do with the scrapers on the inside and quite a lot of fiddly work aligning the staves and making everything work out just right.

Then I can make a handle and a lid.

Note: Don't worry, it only looks like I'm behind. I'm also learning to knit, making a leather bottel, and getting started on hornwork.  More updates on all that stuff later this week... I hope. 

~ Scott

The Arte & Misterie of Coopering: Making a Mary Rose tankard, Part One

Imagine that you possess a monopoly on the secret for creating the only fit container available to move almost all the world's goods.

The Worshipful Company of Coopers had that monopoly. 36th in the great order of precedence for livery companies, the Coopers were nonetheless one of the few solvent enough to rebuild after their guildhall was destroyed in the Great Fire of London in 1666.

There's money in packaging.

Barrels, of course, were the only fit container for moving wine, spirits, ale, and beer. But barrels kept moisture out as well as it kept it in, and they were also used to move goods that needed to be protected from moisture (or rodents) especially at sea. As shipping between England and points far across the sea picked up, barrels were in much in demand to move wheat, barley, tobacco, anything that could be crammed into a nice, dry, barrel-shaped container.

But the "Arte & Misterie" of coopering wasn't limited to barrels. You have to start somewhere. Apprentice and journeymen coopers cut their teeth making buckets and washtubs and tankards like the one I'm demonstrating here. If it was made from pieced-together staves and meant to be water-tight, odds are, a cooper made it.

And though the internet tells you that coopering has fallen by the wayside, in sooth it has merely been decentralized and mechanized like everything else.  The examples of the cooper's art shown above took me about five minutes to gather from around the house. And while I wager my wife and I have more buckets and barrels around than the average American household, if you looked around, you could probably find a few examples yourself. Even if only in one of those half-barrels they sell by the gross at the garden stores to use as planters.

It seems like everyone has one. Just follow the scent of petunias.

Outside of the occaisional barrel, modern coopering tends to rely on glue and/or tongue and groove jointing to hold the staves water tight. The bucket for my ice cream maker shown at right is a prime example of this method of joinery.

And truth be told, if I were to use the tablesaw and router, I could have this project done in an afternoon. There's probably a special place in heaven reserved for craftsmen who are wise enough to use best of the tools given them in their time and place. I can't help but imagine how frustrated my long-dead ancestors are as they watch me muddle through on half-remembers hand-joinery lessons from my grandpa when there's a metric ton of unused automation sitting just offstage.

I won't be allow into that room today. I'll be outside with Follansbee and Underhill and all the rest, making sawdust under a tree as my grandfather and great grandfather did before me...

Tankard-crafting: Part the First

When last we left our aspiring cooper, we were talking about math. Specifically the angles necessary to turn this drawing into a real-life stave for a Mary Rose tankard.

(Note that we're using the term "Tankard" loosely here since the Mary Rose piece holds an estimated nine pints. Which makes it a mug-shaped pail in my book, but no one asked me.)

I think that there are as many ways to do this as there authors writing about it. This is how I did it.

I started by hollowing the inside of each stave with a type of specialized drawknife called an inshave. The actual depth of the concavity is deeper than my inshave can easily accomplish, but with several shallow passes, I was able to pull it off.

After several passes, I had reached close to the desired depth for my staves. I left it a bit shallow, intending that there would be a good deal more fiddling about as I bring it all together, using scrapers and scorps to carve them back into a more or less perfect circle.

The next step was curving the outside, which involved a spokeshave and an array of drawknives. The draw knife and the inshave are potentially the two most expensive tools I've used on this project, so it's worth a moment to contemplate how or whether to bother trying to do this on the cheap.

Below are three types of draw knife I own, counting from top down. 

1. The top one is the cheapest draw knife I could find anywhere that could actually cut wood when I brought it home. I bought it at a home store in Missouri called Menards. It cost about twelve bucks and it'll do in a pinch.
2. The blue one is properly known as a spokeshave, but that's being a mite too charitable. It came from Harbor Freight and cost about eight bucks, which was eight bucks too much. I believe they've stopped trying to convince anyone it was worth even that much, and dropped it entirely. If you find one and have some time on your hands, here's a guy that lays out how to rehab the thing into a usable tool. Too much effort for too little return in my view.
3. This is a proper drawknife, or what a cooper would call a "backing knife". It belonged to my great grandfather and that handle's been missing longer than I've been alive. You can buy these new for $55.00 and sky's the limit for a decent one, but I see these turn up in antique stores for around $20.00 all the time, wanting only some TLC and a sharpening stone.

I bought the prewar Stanley spokeshave you see below yesterday at an antique store for all of twelve dollars. I don't know where people get these things to sell at their antique stores because no one I know who has one would let you have it for love or money. The blade is sharp as the day it was made.

Anyway, the end result is a big pile of shavings and eight curved staves that are ready to be turned into a tankard, bucket, butter churn, or whatever suits your fancy.

I like the look of piles of wood shavings so much that I'm going to show you another picture of them. Just because I can.

You would not believe how much of this stuff I have to fish out of my trouser cuffs and the pockets of my leather apron.

More to come tomorrow.

~ Scott

Calculations, Coopering, Cats, and Cooking: Current events

Sorry I've been remiss this week. All of a sudden, there are a lot of balls in the air and I'm rushing to catch as many as possible before they hit the ground.

Calculations:

The Engineer doesn't want you to think she can't figure out the inside angles of a polygon. She just didn't see the point in giving me the answers.

Can't just tell me the answer, oh no, that would be cheating. I manage a tutoring center for a living. Math people. Go figure. Like any good teacher, she helped me get there on my own.

I should have known better than to think I could get out of this without learning some math.

Anyway, I've decided that there are eight staves in the tankard I'm making, so that makes it an octagon. Thankfully, this chap named Euclid wrote some books on geometry way back when* and that shifts things into the realm of history. Which moves the ball back to my side of the net.

The formula for determining the interior angle of a regular polygon is simple enough. The number of sides minus 2, times 180 and then divided by the number of sides. (No, I didn't know that, I looked it up.) That gives you 135 degrees.

Then, as any woodworker can tell you, you halve the angle to determine the angle of your cut. The bevel on each side of the stave for an eight-piece bit of coopering is 67.5 degrees.
So there.

Then I Googled it to check my work and discovered a lot of websites where I could just type all those variables in and let it figure it all out for me. Seriously. How do people not pass math classes these days?

*Note: Whatever it might normally mean, "Way back when" is now officially 300 BC. Just so you know.

Coopering:

In the meantime, in case you missed the post yesterday, I'm hard at work making that stave tankard I was calculating earlier.

Here's an article about another one of the same sort that was found in the mud along the Thames by a mudlark. These things are pretty big by modern standards. According to the article, it holds three pints. The Mary Rose one I'm basing mine on holds 8 pints, probably as storage for a sailor's beer ration.

Unless I'm way off, I calculate that mine will hold roughly two pints.

Cats:

We've adopted a new 9 month old kitten from the Tacoma Humane Society. Our other two cats are boys and The Engineer was feeling outnumbered by all the Y chromosomes. Also, one of our cats will turn 15 years old this year and he's slowing down a bit. Which means the 7 year old -- who is naturally runs in the neighborhood of 25 lbs anyway -- is getting torpid because he doesn't have an active sibling to play with.

Ladies and gentlemen, meet Cleo. She's our newest family member and I'm sure she'll be in charge in no time at all. 

Cooking:

In my bio I say that I'm not a reenactor or a member of any of the reenacting groups. And that's true, but it's not for lack of trying. Long ago, I attempted to create a group of my own, centering on Renaissance foodways, centered around a guild of actors at the Washington Renaissance Fantasy Faire.

We called ourselves Saint Brigid's Hearth, named so in honor of a dear friend.

The reality of setting up and creating a reenactment troupe was a bit more involved than I gave credit for. It was rather like setting up and running a small business.  The from-scratch nature of this meant building more or less from scratch, beginning with costume and characterization.

In short, the acting concerns outweighed the reenacting concerns.  That was a number of years ago and in the interim, the ren faire where we originated fell and a new faire arose to replace it. I pressed the guild into other hands and moved on to other things as they continued as an acting troupe for awhile before fading away as Real Life Concerns drew the attentions of the actors and the guild went dormant. 

That's when serendipity took over: I conceived of and began this project.  A project that will include cooking, baking, brewing, bricklaying, and other things that will be of concern to the craftsmen who built and used the kitchens of the renaissance.

Over the course of the past few months, I've been in negotiations with the Washington Midsummer Renaissance Faire to revive the group as a proper reenactment society. To build a period-appropriate kitchen on the faire site and do cooking demonstrations. To make history entertaining and trick people into maybe learning something.



This week, the last of the i's and t's were dotted and crossed (not everything in this post can start with a c...) and I turned in the final designs and addressed the fire concerns for the wood-fired bread oven. So the Renaissance Artisan will team up with St. Brigid's. The prototype oven will be built in my back yard as part of this project, and then in late July we will duplicate it on the faire site.

"Because he needed something else to do?" is probably what you're saying, but there's nothing in the presentation of foodways to a ren faire crowd that I'm not already going to be saying to you.

And I'm not going to be doing it alone.

It's going to be more than just "The School of the Renaissance Artisan in front of a live studio audience" because St Brigid isn't about me. It's about providing a community of and for other people with the same aim as me: to celebrate the workaday peacetime world of renaissance England.

The Arte & Misterie of Coopering: A method to the mathness...

This is going to be a longish post and it's going to involve some basic math. If you've a fear of either, I feel for you because though I'm not skittish about reading novel-length posts as long as I'm learning something, math isn't my bestest friend in the whole wide world.  I may be a nerd, but when I was a kid there were math nerds and there were art nerds and there were comic book nerds and band nerds.

The venn diagram of my life intersects all of those, but didn't cross the border of math nerddom until I married one.

And if I want to make it as a cooper in even so small a way as this, I'm going to have to shake hands with a math book. This is what we're going for with the coopering portion of the project.

Image Source: Wikimedia Commons

Image Source: Wikimedia Commons

It's a tankard that was brought up from the wreck of the Mary Rose.  It is one of the many tankards of a similar sort that are knocking around museums in Europe. Several were brought up from the Vasa. They seem especially common in seafaring contexts (shipwrecks and port cities) and are hooped with wood or cane, which is easier to fabricate without a smithy (mine isn't built yet) than iron or copper.

One of the key "mysteries" of the cooper is judging the correct angle for the staves to meet in order to make a perfect circle. The resources online and in the books I have available to me aren't a lot of help on this one. Like the cooper in that video I posted, most sources simply say that a cooper learned to 'eyeball' it over the years.

Obviously, I don't have years to devote to this. I've achieved a measure of acceptance for the idea that I'm never going to get past the apprentice level for most of these trades. The eternal apprentice am I.

The inner and outer curves are easy enough to make up as I go along; the bevel is another story all together. If the bevel's wrong, this thing isn't going to fit together or it's going to leak like a sieve.

Which is to say that I need to figure it out using math.

Somewhere a math teacher that I told "I'm never going to need this after I get out of school" is laughing uproariously.

It's nice that I can continue to amuse them so many years later.

Step One: Ask an Engineer

I asked my wife how to figure out the correct angle for the sides of each stave of the tankard.  She looked me right in the eye and said "AutoCAD". After a moment's reflection, she changed her mind. "Actually, Solidworks is better for this kind of thing."

Hmmm... Thanks, honey.

Okay, for the record, I studied technical drawing "the old fashioned way" in art school and can use CAD if I have to. I could also have my dearest darling draw it up for me. And she offered to do so.  It would certainly be easier for her since numbers aren't really my favorite thing and tech drawing wasn't my favorite class.

The problem with teaching anything, is convincing the student that the subject will be important enough for them to pay attention to. In my past experience, math teachers were especially bad at this. Mine certainly never really did a very good job of telling me why I needed to know this stuff.

To be honest, I didn't do a very good job of listening either, so a plague on both our houses, I guess. Like almost everyone in the world, I use algebra and physics on a daily basis. Only as an adult did I come to really appreciate that fact and had to go back and teach myself (or humble beseech my wife to teach me) those subjects.

Pay attention in math class, kids.

There are several ways to do this without using a computer, or even using a calculator.

Step Two: Do It the Easy Way

Years ago when I started making wheelbarrows, I had to figure out how to cut felloes of the correct arc and length. ("Felloe" is the technical term for the wheel sections of a wooden wheel.) I made my template by cutting out a circle and folding it in half several times to make something that resembles a pie.

If your scale is 1:1, then each pie piece is the correct size and the edges are at the correct angle for a section of a wheel or the stave of a tankard. Cut the center out and the widest point of each pie piece is a template for every angle you're going to need.

If you run on a smaller scale, this method is almost infinitely scalable. Just use a sliding bevel to translate the angles from the template to the wood and you should get it done with a minimum of futzing around.

Step Three: Find a Method Closer to Period:

One of my favorite measuring devices is an ancient tool called dividers. They appear in museums (these supposedly belonged to Michelangelo) and paintings and drafting sets and the bookbags of school children.

Most of those children grow up to be adults who call them "compasses" and think that all they're good for is drawing circles. And for most people, that's enough.

About the only places I still run into them being used in their original capacity is in navigation where they're used to mark out distances on charts and in woodworking. Woodworkers tend to use them to scribe circles and copy relief surfaces.

This is historical woodworker Peter Follansbee's article on using dividers: http://pfollansbee.wordpress.com/tag/compasses/.

They can be very expensive and finely made or they can be cheap as chips, bought in the school supply section of your local Target.

I own several pairs of varied vintage and before the project's finished, I suspect you'll see all of them. The ones in the photo below were purchased for a couple bucks at a Harbor Freight in Tacoma. 

If you stand your staves in a circle and set your dividers to the width of the farthest point, you can draw the line of the bevel as illustrated below.

This gives you your bevel as well as letting you "eyeball" how much material you're going to need to remove in order to get the walls to their desired thickness for your bucket, tankard, barrel, or butter churn. All of those things were made by coopers, and all demand slightly different wall dimensions as dictated by their end use.

I admit it. I needed geometry and math and all the things my high school math teachers had to put up with me complaining I'd never use. I not only needed them, I also needed to know how to apply them when the time came. My apologies to math teachers everywhere.

~ Scott