Process: Tristan Al-Haddad's "Stealth"

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Forms being checked and touched up in the studio before transporting to the site for casting.
Forms for Tristan Al-Haddad’s Stealth being checked and touched up in the studio before transporting to the site for casting.

For months, a mass of scaffolding on a Midtown sidewalk has been raising curiosity about what it conceals. The soon-to-be-revealed answer: a public artwork by Georgia Tech architecture assistant professor Tristan Al-Haddad, commissioned by Cousins Properties for an undisclosed price. The work is scheduled for completion in mid-September.
Titled Stealth, the fluid geometric form comprises two interlocking anamorphic forms with two perspectival axes: a rectangle aligned with the Woodruff Center, and an elongated hexagon aligned with Peachtree and 15th Streets. In other words, the sculpture seems to shift between two and three dimensions — expanding and collapsing — as one approaches and moves around the work.
It has taken two and a half years to realize the project, with a year and a half of that being for the conceptual and technical design development. “It’s a major structure with serious technical feats,” says Al-Haddad, who worked with Jim Case at the design engineering firm Uzun & Case.

Stealth from Tristan Al-Haddad on Vimeo.
Using the 3-D modeling software Rhino with the Grasshopper plugin, Al-Haddad played with 200 variations, studying how the work would seem to transform as one walked around and through it. “It’s standoffish versus seductive or welcoming” depending on the angle, says Al-Haddad.
Made of reinforced, high performance concrete that is very fluid when poured, the 33-foot-tall sculpture weighs 70,000 pounds, 190,000 with the base included. At the base, the concrete is 14 inches thick and tapers to 7 inches. Using a structural framework constructed in the studio, the sculpture was cast in place, in one 4-foot increment per week, allowing time for the material to cure and rebar to be formed before the next pour.
To create the framework, made of thin strips of marine-grade plywood, Al-Haddad and his 11-member staff and about 45 (so far) other helpers used a host of high-tech equipment and software, such as Alphacam and a CNC 3-axis router — no chisels here.
Al-Haddad and his team are still putting on the finishing touches, polishing the concrete, filling bug holes, and installing lighting. He expects the work to be unveiled in October.
Despite Stealth’s mathematical precision, high-tech construction, and careful planning, Al-Haddad wants the work to be “about feeling, not about thinking.”
Here’s how it was built.
 
Forms dry fit and finished at Formations Studio workshop.
Casting forms were dry fit and finished at the Formations Studio workshop.

 
Fitting the forms to rebar at the foot.
On site, fitting the forms to rebar at the foot.

 
Foot reinforcing steel at zero point base.
Reinforcing steel is installed at the base.

 
The sculpture's two forms emerging from the base.
The sculpture’s two forms emerging from the base.

 
Heavy steel reinforcing at base requires extremely tight tolerances for both form and function.
Heavy reinforcing steel at the base is tightly fitted for both form and function.

 
Sinclair crew at work - placing wet concrete from pump truck.
Sinclair crew placing wet concrete from pump truck.

 
Concrete pour at +19’.
The concrete pour at 19 feet.

 
Tension straps resisting 16,000 pounds of Self-Consolidating Concrete hydrostatic pressure.
Tension straps resisted 16,000 pounds of pressure during the concrete pour.

 
Reinforcing steel weaving at upper fold.
Reinforcing steel weaving at upper fold.

 
Tension straps at fold transition.
Tension straps at fold transition.

 
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View into the form before a pour.

 
The razors edge - concrete fin diminishing to less than 1/4-inch thickness .
The razors edge—concrete fin tapering to less than ¼-inch thickness.

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The super thin edge on an upper portion.

 
A seemingly weightless concrete curve.
A seemingly weightless curve of concrete.

 
Sinclair Construction Group workers ‘wrecking’ forms (don’t mess with these guys)!
Sinclair Construction Group workers “wrecking” the plywood forms.

 
Top of sculpture as forms are removed. Urethane form liner adhering to surface will be scraped before polishing.
The top of sculpture with forms freshly removed. The urethane form liner adhering to surface will be scraped off before polishing.

 
'Strip down’ - Upper fold demolded.
The work’s upper fold, demolded.

 
The definition of intensity. Helena harnessed up and clipped off for safety while scrapping at + 30 feet.
Helena in a secured harness 30 feet up, scraping off the urethane liner.

 
Helena, Miriam, and Sky removing urethane liner.
Helena, Miriam, and Sky removing urethane liner.

The beast yet caged. 35 foot high scaffold with four work platforms (by Sunbelt Scaffold).
The complete 35-foot-high scaffold with four work platforms.

 
From work in place.
Getting close.

 
Wet polishing with diamond cutters to expose the black-blue Adairsville Granite aggregate from north Georgia.
Wet polishing with diamond cutters to expose the black-blue Adairsville Granite aggregate from north Georgia.

 
Almost there.
Almost there…

 
Stealth detail.
Stealth surface detail.

 
Stealth detail.
Stealth detail.

 
Nearly finished!
Nearly finished!

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Stay tuned! We’ll post images of the completed work soon.