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Making a Decorative Sunburst

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?

Terminology

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.

(Note: Click any image to enlarge. Hit your browser's "back" button to return to this article.)

This Sunburst

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.

. . .

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.

Adapter with two #8 flat-head machine screws

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.

1. In this example, enter 48 Inches, then press the "Circ" key. The display will note 48 in. as the diameter.

2. Next, press the "Circ" key again. You'll see the area in the display.

3. Then press the "Circ" key once more, and the display will note the Circumference.

 

 

4. Because we're working with half the circle, divide the circumference by 2. The result is the arch length of our sunburst: 75 3/8 in. Because we're using 12 sun rays, divide 75 3/8 in. by 12. The result is 6 5/16. That's the width of each ray along the circumference.

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.

But you can use the calculator and a piece of flexible material—a thin rip of PVC works great—to make a flexible story pole.

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.

Geocentric Society

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˚.

Using a construction calculator, enter 24 INCH and press RUN.
Next, enter 15 and press PITCH. The calculator will know you’re working with 15˚.
Press RISE and the calculator will display the precise amount that a 15˚ diagonal line will rise across a 24-in. span—6 7/16 in.

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.

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.

• • •

AUTHOR BIO

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.

Comments/Discussion

24 Responses to “Making a Decorative Sunburst”

  1. David Pugh

    Terrific. I guess that doing an elliptical sunburst is similar by dividing into equal segments and then fitting them to a backboard which is elliptical. Right?

    Reply
  2. Anthony

    Nice tutorial Mike. I found this site not too long ago and thought the name sounded familiar. I wish I would have known about you when I lived around the block. I could have learned a lot.

    Keep up the good work

    -Fellow ex-Levittowner

    Reply
  3. gary

    Great explanation Mike. You should get a commission on the large construction masters you’ve sold.After your Kansas City visit I had to have the big one.I passed the smaller model on to my foreman who is an old dog thrilled to learn new tricks.
    Thanks and it was a great presentation at your show as well.

    Reply
  4. Laurie McDougall

    great article! I really like learning how to do the math, and using a square for other than a straight edge. Years back on the set of stargate (tv show) , I watched an “older” carpenter lay out a space ship using only a square- and he was drunk at the time!
    It’s almost a lost art. (the layout part, not the drinking)

    How did you heat up that PVC to 260 degrees? slowly heat it up with a heat gun?

    Thanks!

    Reply
  5. Craig A. Polley

    From personal experience, the only mistake I saw was quoting a price out of thin air. If you don’t mind, how much money did you lose on this project?

    Reply
  6. mgfranz

    Lots of information in this article, in fact, too much… Seems more like an advertisement or infomercial for Festool and Construction Master than an actual carpentry story.

    Reply
    • Gary Katz

      MG,
      I’m sorry if this article was a little too much for you! We thought, after the custom volute articles, that this one was pretty simple! And actually, Mike spent more time on this story, and during his clinics, explaining how to use a Framing Square to layout the sun rays, and how to make a jig to make the rays repetitively, then he did or does working with the calculator! And that’s a REAL difference for Mike. He believes a construction calculator–whether it’s make by Construction Pro or Build Calc–is more important than his hammer. He makes a lot more money using a calculator than he does driving nails!! :) And just because a carpenter finds it easier and more effective to use a saw with a guide rail doesn’t make it an infomercial. What’s the madder with you?? Every carpenter I know who has used a saw and guide rail won’t go back–in fact, DeWalt and Makita copied Festool and are now making similar tools. If you haven’t tried one…well….’nuff said.
      Gary

      Reply
  7. Pete838

    Any chance you could post some pics of the finished product?

    Reply
  8. Craig

    I would like to see a picture of the sunburst on the house. It is amazing all the many uses of a carpenters square.

    Reply
  9. Mike S

    Pete & Craig , Somewhere in the vast collection of photos , I probably have the original sunburst installed,, I’ll look for it , I t was in a Fine Homebuilding article some years ago . If I find it I’ll get Gary t post it.

    Craig, – My cost for material – a can of Glue …. It was pure profit ….
    It was all made from leftovers from the job.

    Laurie — I use a Heatcon Electric blanket, its a professional tool used in the electrical and Aerospace industry, Now they make a version for PVC..

    mgfranz, I used to use a slide rule a hand saw and a hammer.. But I found that by learning how to use the Construction master , I was able to cut my layout time down to a few keystrokes and eliminated errors substantially. Until recently, there was no other tool on the ,market with the capability to do the math so easily. The Festools ,make my life easier, They work cleaner , have all sorts of attachments I can’t get anywhere else. , and they are worth fixing if you break it. I still have my original TS saw from when Festool first started selling in the US, My Son has inherited it. My first circular saw has been replaced by at least 10 others in my 32 years on the job.

    Reply
  10. Mike

    That was one of the best finish tutorials ever. If that is the quality of your training I will look forward to your visits in WA. State.

    Reply
  11. Keith Mathewson

    Nice article Mike. You can also plumb up from the horizontal line to a point on the circumference if you use the other leg of the triangle.

    Reply
  12. Jon Wells

    I will be very anxious to see the finished product. Somewhat disappointing to see all the how-to information without it…

    Reply
    • Gary Katz

      Jon,
      Yeah, I’d like to see the finished project, too, but the story was really about how to do it. I think Fine Homebuilding may have taken the finish pictures for that story, in which case we won’t be able to publish them.

      Reply
  13. Larry O'Loane

    Great Article ! Just the way I like ‘em. Heavy on the data, well informed personel opinions and recommendations.

    Reply
  14. Ed

    I would love to see the elliptical version, layouts, math, jigs…

    Reply
    • Gary Katz

      Ed,
      Mike will soon be publishing an article on Ellipse layout. He’ll be sure to backtrack and describe the technique for making an Elliptical Sunburst, too.
      Gary

      Reply
  15. Greg martin

    Great article. especially for those of us carpenters who dont get to use this kind of math frequently. I need the refreshers and tips. Keep up the great work. Too much info?! There are many different levels of carpenters. They should all be able to get it with your good teaching skills. thanks

    Reply
  16. Sternberg

    I keep a copy of the Machinery Handbook, just for layouts like those. It will find you the dimensions of the chords across an arc, and let you make those layouts with ease. I also keep a vernier caliper on hand. Those have gotten to be relatively cheap.

    Reply
  17. Kyle

    Infomercial for Festool? Mike says (verbatim) “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.

    doesn’t say FESTOOL guide rail! are you hearing voices or something?

    I’ve been using a “Guide Rail” since before Festool guiderails were a figment of it’s inventors imagination.

    the old dog that taught me to take a piece of 1/4″, glue and staple a straight fence to it, then cut the kerf line (for each saw I own) was probably relaying what some old carpenter taught him..

    I bet this goes back to about 15min after circular saws were available…

    Mike doesn’t need to buzz Festool around here, we pros KNOW how great their tools are.
    -too bad ProTools (Festols sister company) are not yet available here in the US…
    and by the way, this carpenter DID pay attention in High School, and I still use a calculator to speed up calculations (a very inexpensive plain calculator ) although I wouldn’t mind having one of these construction specific models.
    that would make things go even FASTER and faster is better so long as accuracy is kept or improved.

    GREAT writeup! I know I just learned something! you do realize there are many many ways to do things, and I feel the point of all these TIC articles is to get the reader THINKING. -just one man’s opinion…
    this one has inspired me to think up a faster (better for me) way to layout and cut parts for any sunburst -ah! make that 2 new ways…

    Reply
  18. James O'Gorman

    Mike,
    I certainly see how this project is a good exercise to hone our calculator skills, I would make a suggestion on laying out a 15 degree angle which is much simpler.
    Begin with a square line from the origin of the semicircle upward, creating two 90 degree sides of the half circle. Mark a light line between (and find the distance from) the outboard edge at the top to the outboard edge on the right or left side, a distance which should be about 33.94″ for a circle with a 24″ radius. Then place a mark at 17″ from each end and draw a bisecting line between the two marks just made, creating two 45 degree angles. Find the distance between the outboard end of this line and the end point, then divide by 3 to trisect the 45 degrees into three 15 degree angles.
    Trust me, this process is much simpler than my description. I hope it makes sense to everyone.
    I really enjoy and have learned a lot from TiC, keep up the good work, all.

    Reply
  19. Ray Habenicht

    Nice article and videos. Makes me wonder when Katz Roadshow will be in the area again. Would love to attend another.

    Good info, very efficient work, great craftsmanship. Thank you Mike.

    Ray

    Reply

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