Building a 20’ Gothic Arch
I value truth in materials in 3-D art making. But in this project, engineering concerns, public safety and budgeting nuanced the considerations. In the proposal drawings for Gordon-Conwell Art Commission, a Gothic arch would act as a visual unifier organizing multiples within. Lending its rich conceptual freight, it would serve as a link between the church past and present. After a search for a ready-made arch, I came to the conclusion that in order to not compromise on quality and aesthetics, a custom 20’ x 12’ gothic arch would need to be crafted by hand. This was quite a daunting challenge in terms of both size and technical skill. Several kinds of media were considered: metals, stretched fabric, paper, cast plastics or plaster. But wood arose as the best material all around in terms of its workable qualities and light weight relative to other choices. Additionally, it could be built in sections for transport and installation.
After careful measurement of the wall space and consideration of scale within it, I was able to grid out an initial outside measure. To determine the width of the columns, I cut paper to the sizes I thought had potential and tested them within the space itself. Eight inches provided a proportion that looked in harmony with Gothic arches of the past. Also, the parts would need to be light enough for 2-3 people to hold out awkwardly over the side of the lift while anchoring to the wall. Five sections became the most obvious division to allow for building, transport and installation. I needed a carpenter with the guts and innovation to try something new, and I knew just
the man who’d be up for it. So I asked my father, Jerry Spinks, a fine carpenter himself, if he would be game. He didn’t flinch but accepted with excitement.
Neither of us had studio or workshop space large enough to build the work indoors, so we determined to build it in his driveway at his home in Charleston. He set up a large tent used for my sister’s outdoor wedding years ago. It hadn’t rained for weeks, but of course, it poured once we began working. We constructed the sill first since this would bear
the weight of the arch above and if built correctly could aid as the base to ease installation of the columns. So we cut the 12’ x 8” backboard on a table saw out of professional grade ¾” plywood. In anticipation of the columns to flank each side, the ends were cut at 45 degree angles with 3 load-bearing French cleats evenly distributed from center.
The arch is the outer container unifying the inner action. Therefore, to lead the eye inside the art, the arch itself needed to bevel down into the containing space. How would we do this? Dad came up the idea of cutting ribs distributed throughout. It added a lot more work, but the effect was well worth the time and costs.
We cut the 200+ pieces to 8” (matching the width) on a chop saw. He made a jig were we could cut consistently to shape on a band saw the outside edge at 3 ¾” and inside at 1 ¼”. My 7 year old niece who wanted to help sanded the ribs and actually did a thorough job – no redo’s required.
These ribs were distributed along the backboard about every 8”. They were affixed with Liquid Nails and nail gun. A 2” strip topped the inside rim, and a 4” plywood strip cut to size with a circular saw lined the outer. We now had the sill. We did likewise for the side columns. We had about 11’ before the arch kicked in, so these were built by similar process.
The two top arch sections (each 10’ in height and 6’ in width) were by far the most challenging. Our measurements were in place, but how do we draw a smooth arc for cutting? We tried making a jig to no avail. Then we tried bending a flexible plank around the measures, but this wouldn’t yield a consistent bow. What worked was a nice section of 1/8” square brass bar stock. We aligned it to the measures, bowed it to a nice consistent bend, and then traced the arc around it. Once we had the outer line, we could measure for in the inner line. The backboard was cut out by a scroll saw, flipped, traced and cut to give us the other arch side. Then they were ribbed and sides affixed.
To ease installation, we made joints that would fall into the right places at the angles needed. Guides were placed on the joints so that we wouldn’t have to fish for angles or level the pieces under strain on the Skylift. It also limited the range of direction that the part could fly out of control during installation. Part could fall to the outside only but would be stopped by the flanking wall. But the more dangerous possibility of falling forward or inside was limited.
Now for the facing… In order to firmly anchor the arch to wall, the face was left open to be attached on site once the arch skeleton was affixed. The column and sill faces were cut by a circular saw. The outer edges were then cut on an angle on a table saw to match the bevel incline. This took a little trial and error. I googled geometric formulas to account for the difference the bevel would make, but to no avail. So we just had to take a pass at it.
The sides and sill went fine. The arch was another story. Not only did we have a curve to contend with, but the bevel incline offset the measure. And I had no formula. The bevel prevented us from laying the face board flat for a good trace. We tried making a trace from the backboard but had major gaps because the flatness simply created a different arc. I made a paper pattern, traced off a direct impression and cut to size. It laid perfectly as a pattern, but once tried in wood, there were just too many
variables to control to get a perfect match. We finally made a rough cut about 2”-3” over size of the facing. We only worked one side at a time, cutting slowly on a scroll until a good match was formed. Once one side laid in its groove, calipers run along the opposite edge traced out the opposite cut line. After cutting, a belt sander was used to match the bevel along the outer edge and shore up any differences in the facing.
We worked 10-12 hour days for a week and a half. The mental and physical work was draining at times. On the final measurement, we got within 1/1000th of an inch on BOTH sides! We had a lot of people praying for us and we could feel the Spirit's winds fill our sails. Once assembled to full size in the driveway, we were excited about the results and the part it would play in the final work.