Tag Archives: measurement

How to Draw an Ellipse

How to Draw an Ellipse

I have three new videos up on my Prop Building Guidebook companion website. Two are on painting techniques (spattering and sponging), while the third shows a quick method for drawing an ellipse. I’ve attached that below. My book comes out next Tuesday, so that is it on the videos for now. But if you want to request a video for a specific technique, or demonstrating a certain tool, let me know, and I’ll see what I can put together.

A Practical Guide to Friday Links

Mother’s Day is this Sunday. Bill Tull, the prop master on Conan O’Brian, has some Mother’s Day gift ideas for those on a budget.

Here’s a blast from the past: an Interview with Anna Marchant, who was a prop maker on the two Matrix sequels. It’s a great interview because it really cuts to the heart of what kind of materials she works with, how the prop department interacts with other departments, and all the other day-to-day details that other interviews forego to talk about “cool props” or “what it’s like to work with movie stars”.

Dallas Poll, a prop maker on Lord of the Rings, had his house burglarized recently, with a number of props and memorabilia stolen. To make matters worse, one of the items stolen was his Stormtrooper costume—and the thieves struck on Star Wars Day!

Rich Dionne’s latest post is about working together in the theatre. This isn’t just about how a playwright works with a director; this is about collaboration within the production department itself, and how important it is for props, costumes, lighting, sound and scenery to occasionally work together on tasks and not just throw walls up around their individual departments.

Robert Lang does a nice job summing up the advantages of not measuring your work. Relying on measuring devices introduces inaccuracies into your work. Sounds counter-intuitive, right? Check the article out.

Tape measure

A case against Metric

Suppose you want to divide one foot into four parts: that is three inches. Divide a foot into three parts and you have four inches. Divide a meter into four parts: each part is 25 centimeters. Divide it into three parts and you are left with 33.33… cm.

The same is true with liquid and dry measurements. Take a cup. Now double it and you have a pint. Double it again and you have a quart. Take a gallon and divide in four; that’s a quart. Divide a liter into four parts, and you have to call it either 2.5 deciliters or 250 centiliters.

Look at a clock; it has sixty seconds in every minute, and sixty minutes in every hour. You can divide a minute in half, thirds, quarters, fifths, or sixths and in every case, you are left with a whole number of seconds. No fractions or decimals.

Metric may be good for scientific and technical measurements with things that increase by orders of magnitude. For example, hard drive memory started out with bytes, than kilobytes, followed by megabytes, gigabytes and now terabytes. But when dealing with carpentry and recipes and other measurements used in the construction of props, you are not having to convert between units which are one hundred or one thousand times larger than other units. You are dividing things into halves and quarters and thirds. You want to be able to take a measurement with a ruler which gives you one or two whole numbers and a fraction. It is so much easier to say “this prop is one foot and three inches tall, two feet and five inches long, and three quarters of an inch thick” than it is to say “this prop is 38.1 centimeters tall, 73.7 centimeters long, and 19 millimeters thick.” Furthermore, when you look at a tape measure, the hash marks for the fractions of an inch are all different sizes, so you can easily see whether you are at 1/4 or 5/16. With a metric tape measure, you have ten tiny divisions per centimeter, all at the same height. Is that .7 cm or .8? Who knows! (Of course, the greatest sin is a tape measure with both metric and customary units.)

The system of inches and feet were developed from commonly experienced physical objects, like a human thumb and a human foot. Their subdivisions were developed to measure commonly constructed objects for everyday use. This is what we deal with in props; the construction of everyday items on a human scale. A meter, on the other hand, was derived as a fraction of the Earth’s diameter. How much more sense does it make to say “this bench should be as long as three of my feet” than it is to say “this bench should be large enough so that 3,187,000 of them will fit end-to-end from one side of the planet to the other, going through the center”? Balderdash!

Metric is a centrally-designed hierarchical system which is applied to the measurement of everything conceivable, while customary units are a collection of localized systems specifically altered to the items and entities being measured. It may be funny to dig up archaic names of measurements to ask rhetorical questions like “how many hogsheads in a morgen”. In reality though, you will never need to convert the measurement of a cask of wine to the measurement for a plot of land. As an aside, archaic units are not limited to the customary system; does anyone in metric still use a stère?

It may be tricky to calculate how many inches are in a mile, but you rarely need to use that conversion in day-to-day life. Finally, despite the often touted ease of converting from nanograms to kilograms to megagrams, scientists have settled on essentially using the kilogram to measure the mass of everything, from the sun to an electron. No need to convert anything!

This is not so much a case against metric, but an appeal for hybrid systems and specificity in measurements to the task at hand. There is no harm done if I build a bench using inches and feet while biologists measure the volume of a cell in micrometers. I don’t wear the same outfit as a biologist, and a biologist doesn’t use the same tools and machines as a props artisan. That would be absurd. Neither of us have to convert the volume of a cell to the height of a chair. That would be even more absurd. Both of us using the same system of measurements? That’s the absurdest.

Tape measure

Revised drawing showing thicknesses

A Common Error in Making Cutlists

One way to begin with a carpentry project is to make a cut list. You break apart the drawing into all the parts, figure out the measurements for each of those parts, and draw up a list of how big each piece should be. Perhaps the most common error in developing a cut list is neglecting the thickness of the pieces. Let’s say you want to build a cube which is one foot on each side. A perfect cube. A solid cube will be built with six pieces of wood. For this exercise, let us say you will build it with scraps of ¾” plywood you have laying around the shop. If you make a drawing of a cube, you may assume you need to cut six pieces one foot long and one foot wide.

A one-foot cube
A one-foot cube

Wrong!

Let’s look at the drawing again.

The top and the bottom can be one foot by one foot. However, if you make the front and the back one foot by one foot, the cube will end up being one foot by one foot, one and a half inches. See? You need to subtract the thickness of both the top and bottom from the length of the front and the back. In this case, ¾” and ¾” is an inch and a half, so the length of the front and the back would be 10 ½ inches. The width remains one foot.

Revised drawing showing thicknesses
Revised drawing showing thicknesses

The sides need the thicknesses of the materials taken away from both the length and the width. In other words, it will be 10 ½” by 10 ½”. So our final cut list looks like this:

  • 2 pieces at 1′-0” x 1′-0”
  • 2 pieces at 10 ½” x 1′-0”
  • 2 pieces at 10 ½” x 10 ½”

At this point I wish to add a caveat. Plywood does not come in exact measurements. While it is sold as ¾” thickness (or ½” or what have you), the actual measurements vary. Three quarter inch construction plywood is actually 23/32”. In some cases, you may not care about a thirty-second of an inch difference, though in others you may. One sure-proof method for accounting for the actual thicknesses of materials is to hold two pieces on the piece you are measuring and make your mark using them as a guide.

An easy way to account for thicknesses
An easy way to account for thicknesses

Now, in props, there is no reason to try and create a cut list for all the parts at the beginning before you begin working. Sometimes, it is nearly impossible to do all the math to discern the measurements of every single piece. Other times, you need to build a section and look at it so you can visualize the next portion of what you are building. It is not always necessary to have a project completely mapped out in your head at the outset, because better solutions may become apparent as the prop comes into being.

I’ve posted before about the importance of precision in cut lists. You will also find a link to a wonderful series at Popular Woodworking which has a more in-depth look at cut lists.

Sizes

You may have noticed a new link over on the side link: Sizes. If you haven’t checked it yet, you’re missing out. Sizes lists the sizes of things and the units used to describe them. It may sound dry, but it is an incredibly useful reference for a props person.  Here is just a sampling of the variety of information you can find there: