I was working on a remodel—a high-end home near the Hamptons—when the homeowner came out the front door with a magazine in her hand. “Look!” she said. “This is exactly what I want on top of my front door!” She tilted the picture toward me: a handsome Greek Revival portico decorated with an elliptical sunburst. “It’s going to cost you,” I told her. “How much?” she asked. “About $1,200,” I said. She smiled and said, “Do it.”
That’s when the fun started. I figured I’d order a standard polyurethane sunburst from my local supplier, but the house didn’t have a standard entry door—the door and sidelight were mulled together. I needed a 58 1/2-in. sunburst to fit that opening! And no one made one. I spoke with one manufacturer and learned that they’d make any custom size I wanted. The good news was that after they charged me $1,500 to make the mold and $800 for the sunburst, each additional sunburst would cost only $800. But I needed only ONE!!
Sometimes it’s not smart to quote a price—even an estimate—while you’re talking to a client!
Like a lot of construction problems, I fell asleep struggling for an answer and woke up with a perfect and simple solution: I’ll make the sunburst myself. After all, how hard can it be?
The sunburst in this article is pretty simple—it’s a half-circle. You can use the same technique to create a elliptical sunburst, but that’s a story I’ll save for another time.
In order to make a simple sunburst, you need to understand the terminology (see photo, below). First, we’re working with a half-circle. Every circle has a radius—that’s the distance from the center of the circle to the outer edge (or, circumference). The diameter of a circle is the distance across the circle at the widest point—it’s also the radius multiplied by 2.
The sunburst I’ll be making for this article has a 48-in. diameter, which means it has a 24-in. radius.
However, those measurements are to the outside edge of the trim! Because of the exterior Versatex trim I’ll be using, I have to subtract 3/4 in. from the outside dimension (O.D.). That means that the radius for the backboard is 23 1/4 in. and the diameter of the backboard is 46 1/2 in.
There’s one more circular element to a sunburst, and that’s the sun itself. For this example, I made the sun 9 in. in diameter—a 4 1/2-in. radius. During my Roadshow presentations, I use one trammel arm with three center points to scribe all three diameters, but I use another trammel arm—attached to my router—to cut the backboard, and a third trammel arm to cut the center sun.
Cut the Backboard
There are countless ways to attach a trammel arm to a router. I’ve found that the best method is using a Festool 1400 router along with a template guide adapter. I bought several of the adapters, and made an assortment of snap-on trammel arms for different size radii, and for ellipses, too. That’s the beauty of the Festool system—attaching a trammel arm, or switching trammel arms, is literally a snap.
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I’ve found that it’s easier to drill center points exactly in the center of the bar stock if I first run the aluminum through my table saw and cut a shallow kerf (see photo, right). Next, I bolt the aluminum to an adapter with two #8 flat-head machine screws (see photo, below). The adapter must be drilled for those screws, and the holes must be countersunk, too.
I use a down-cut spiral router bit, which helps keep the PVC dust against the backboard, and makes for easier dust collection. That’s another reason I prefer using the 1400 router. PVC dust is nasty stuff—I’d rather have it vacuumed up quickly than spread all over the work piece, the work table, and my clothes. If you don’t have good dust collection on your router, try using Static Guard. Spray it on your tools, your work area, and your clothes, and the dust won’t stick—it’ll fall right off, like sawdust should!
Even or Odd Rays
Before laying out the size of each ray, you have to decide if the sunburst will have an odd or even number of rays. If you use an odd number of rays, a single ray will land right at the apex of the arch—like a keystone.
If you use an even number of rays—which is what I’ll be doing in this article, two rays will meet and flank the apex of the arch. I’ll use twelve rays in this example, six on each side of the apex.
Layout: The Hard Way
There are several ways you can lay out the rays on a sunburst. When I first started making these ornaments, I approached the problem by dividing the circumference by the number of rays. (Spoiler: If you want to save time, skip ahead to Layout: The Easy Way!)
To find the circumference of a circle, we were all taught in high school to use the formula: 2 x pi x r. Of course, most carpenters weren’t paying attention in high school. I know I wasn’t. But, today you don’t need to remember formulas. You can use a construction calculator, and it’s much easier—every step of the way.
You might think you can cut a gauge block or use a compass to strike marks for every ray, but you can’t, for two reasons: First, 6 5/16 in. is a measurement along an arch or radius—it’s not a straight line measurement; and second, the measurement is not really 6 5/16!
|The calculator rounds off the real decimal number to the nearest friendly fraction. To find out what the real decimal number is, press the Inch key: 6.2832. Good luck finding that precise measurement on a tape measure.|
To layout the story pole, use your calculator to locate measurement marks for every ray. Just press the + button once, and the = button once to find the second ray; then press the = button to find the location of each succeeding ray. You’ll discover very quickly that the calculator will eliminate cumulative error—it will add 6.2832 in. to itself for each layout mark, and round the sum off to the nearest 1/16th, every time.
Layout: The Easy Way
Using a story pole is accurate—if you use a really sharp pencil and you mark each measurement precisely. But that kind of accuracy isn’t easy, in fact it’s difficult and slow. For that reason—and because Gary Katz figured out how to make a jig for both cutting and routing each sun ray—I use a new method now, which actually eliminates the whole layout process. Rather than concentrating on the circumference of the sunburst, I now focus on the angle of each ray.
Did you ever wonder why there are 360 degrees in a circle? What’s that have to do with this sunburst? A lot. The possible answer dates all the way back to early civilization—when we counted the number of days in a year measured by the time it took for the earth to orbit the sun. Of course, we didn’t know that’s what was happening—we thought the sun was orbiting the earth. And we thought it was 360 days, when it’s actually 365 1/4—or something close to that. Regardless of the real reason, a circle still has 360 degrees.
If a circle has 360 degrees, and we divide it in half, we’re left with 180 degrees. And if we divide 180 degrees by 12 rays, each ray has an angle—or PITCH—of 15 degrees. And PITCH is the key concept for laying out a sunburst the easy way.
Framing Square as Protractor
A lot of carpenters use framing squares, but few of them ever stop to think where these magically simple tools originated. The first steel squares were apparently manufactured in the 1820s by the Eagle Square Company in Vermont, but the design and use of the square dates back much further. According to Don Dunkley, Tools of the Trade’s “professor of framing,” “wooden squares dating back to 1500 B.C. have been found buried ceremoniously in the tombs of master Egyptian builders.” Don’s been known to exaggerate a little, but even if his dates are only close, I bet a lot of carpenters have never realized that a framing square is really just a very precise protractor.
Most of us think that a framing square is meant to describe roof pitch: for instance, if a roof rises 6 in. vertically for every 12-in. horizontal run, the roof is known as a 6/12 pitch—a very easy concept for a carpenter to get his hands around—after all, angles can be confusing; it’s much easier—and more precise over long distances—to work with a 6/12 pitch than it is with a 26.57˚ angle. However, sometimes you need to work with precise angles, and a framing square is still the best tool for the job.
High School Math Class
Let’s go back to high school for just a second and take a look at the right angle. According to Pythagoras, if we know any two elements of a right angle, it is easy to find all the other dimensions.
If we know the rise and run, we can determine the pitch; if we know the pitch and the run, we can determine the rise. And we can also determine the diagonal—which comes in handy when laying out stairs.
For the sunburst I’m laying out, we know that each sun ray has a pitch or angle of 15˚. And if we use the 24-in. leg of a framing square to layout the first ray, we know that the run of the right angle is 24 in. Using a construction calculator, it’s easy to solve for the rise—that’s the element we really need to know in order to strike a line at exactly 15˚.
While I could use a framing square to lay out each sun ray, that’s not the most efficient or the most fun way to build the sunburst. Instead, I use the framing square to lay out a cutting jig.
We now know that the ray rises 6 7/16 in. every 24 in. To make a cutting jig, just place a framing square across the edge of a board with the end of the long leg touching the edge. Adjust the square until the 6 7/16-in. measurement mark on the short leg is also flush with the edge of board. Then trace a line along both legs of the framing square. (Click on the images below to enlarge them.)
Attach stops to both layout lines. But leave the stop short along the 24-in. line, so you have room to cut the radius for the sun, and so there’s enough room to run a router with a pattern bit across that radius.
Instead of using the fold-down guide rail on my MFT table, I attached two taller stops to the back of the jig. Those stops position my guide rail perfectly for every cut.
Rabbet the Edges
With a small sunburst like this one, it’s difficult to stack each ray on top of the preceding ray—the thickness of the sun increases with each layer. Instead, I opted to rabbet the sides of each ray, creating a groove—or dado line—separation. I used a bearing guided rabbeting bit, but you could just as easily run a V-groove bit on the edges of the rays, or a core box bit—any detail that creates some separation between the rays.
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Mike Sloggatt is a frequent contributor to the Journal of Light Construction magazine and writes for Fine Homebuilding and Tools of the Trade, in addition to moderating the JLC Rough Carpentry Forum. For the past four years, Mike has been the Frame-to-Finish (Rough) Carpentry presenter for the Katz Roadshow. Mike also teaches seminars and clinics in all aspects of carpentry and remodeling, and is a regular presenter at JLC Live, The Remodeling Show, and the International Builders’ Show. He takes education seriously, especially for the construction industry, and appears frequently at association meetings, including NARI and other regional builder and material groups and lumber yards. Mike has more than thirty years of experience, and he specializes in high-end, challenging remodels near his home on Long Island.