Waterline Square Bridge
Gardner Pickering, Hewes & Company
The caller described it as a strip-plank canoe. Serpentine. 90 feet long. In Manhattan. Two of them, plus a spiral staircase. How could we not be interested?
Joe Jaroff contacted us in January of 2017 about an interior steel walking bridge that his firm was building that needed to be clad in ‘sinuous’ varnished wood. Jaroff Design provides custom architectural metal and glass design and fabrication services to the architecture, interior design construction and art communities.
Hewes & Co is active in a specialized market CNC machining parts for boatbuilders and has a large cabinet shop staffed with veterans from many local yacht yards. While the scope of this project was unusually large, the steps were not so different from other projects that we have tackled, plus the steel structure was being fabricated only two hours away in Newport, Maine.
From the 3-D CAD drawn by Craig Chowaniec of The Rockwell Group, I sliced the bridge into 30” sections and machined ¾” plywood bulkheads to size; tabs were welded into the steel structure to bolt them in place.
The structural steel bridge was shipped to our shop in 30’ lengths and assembled upside down; plywood bulkheads were bolted down and 1” thick maple top and bottom caps (the keel and shear) were CNC machined to size, then attached to the plywood bulkheads with pocket screws and epoxy. The sides were filled in with 27,000 feet of 1” x ¾” tongue and groove maple strips, custom milled with a 2° bevel to account for the curved sides. The T&G maple was glued together with 3M 5100, a fast cure one-part polyurethane glue. Sloped half-lap joints separated the wooden sections every 12’- 20’ feet, which fell at the bridge steel support posts.
West System Six10 was used where the wood met the plywood bulkheads. Later this joint was filleted and a 10oz fiberglass tab was epoxied in place on the inside. After several thousand hours of shaping and sanding, starting with 36 grit longboards and taking it up through 180 grit pneumatic 5” DA sanders, we rolled on Sherwin Williams Wood Classic Interior Oil stain, a product that we had tested for its compatibility with epoxy (since discontinued). As the stain reveals previously unseen scratches, we had to sand off the stain at least twice on each piece before we had an acceptable finish. Then one coat of epoxy, a 2nd coat with 4 oz fiberglass boat cloth, followed by 3 more buildup coats of epoxy (all West System 105 resin and 207 Special Clear Hardener with no fillers) followed by a hard fairing and sanding, then two coats of Epifanes one part high gloss varnish and two coats of Epifanes Rubbed Effect (satin) varnish, cut with Epifanes Easy-flow and rolled (but not tipped) with a fine foam sausage roller
The staircase needed to look the same, but because of the tight curves, couldn’t be constructed from ¾” thick maple. We ‘cold molded’ the staircase by wrapping 3 layers of 6mm meranti plywood around the plywood moulds in different orientations with thickened epoxy between each layer. After re-fairing the plywood skin, 1/8” x 1” maple strips were laid over the plywood into thickened epoxy and attached with 23-gauge pneumatic pin nails through the face, which are not visible under the final varnish. The layout pattern was particularly tricky here; starting at the shear, the strips had to follow the curve they were lying on, which made for many wedge-shaped pieces.
The wood cladding on the inside of the walkways is ½” meranti plywood on the straights and 3 layers of epoxy laminated 4mm meranti plywood on the curves, with ¼” x 1” maple strips epoxy-vacuum bagged to the face, and then finished off as the rest of the wood. The finished bridge is in the underground room connecting 3 new residential skyscrapers (Waterline Square, Manhattan). We sealed the inside with epoxy to minimize movement from changes in humidity, as there are two swimming pools, a tennis, basketball, and squash courts in the adjoining spaces.
Starting from an ‘art’ rendering of something that’s never been built before is a tricky proposition. We were fortunate to be surrounded by a set of extremely talented boatbuilders; Artisan Boatworks, Ocean Stars Yacht Painting and Belmont Boatworks sent their talent down to help us for months at a time; Brooklin Boatyard, Epifanes, and Gougeon Brothers provided crucial technical and troubleshooting support. The construction concepts that we initially started with generally proved to work out. One very pleasant surprise was the talent and versatility of the installation crew. As this was a New York City union job, we did not do the installation, but I spent 4 weeks there offering technical support. Eclipse Contracting did an amazing and careful job hoisting, installing and aligning the finish varnished wood cladding pieces, some of which were 20’ and 650lbs. Waterline Square is set to open summer of 2020
Would we answer that call again from Jaroff Design? Absolutely.
CAD drawing
The initial 3-D CAD model from The Rockwell Group
Shear Plank
Epoxy fillet and fiberglass tape on the inside of the maple to plywood joint. The shear planks sit on the white structural steel plate at the top of the photo.
3M
3M 5100 polyurethane squeeze out on the T&G maple strips. The angled half lap joint is milled during construction.
3-D CAD
From the 3-D CAD drawn by Craig Chowaniec of The Rockwell Group, I sliced the bridge into 30” sections and machined ¾” plywood bulkheads to size; tabs were welded into the steel structure to bolt them in place.
Bulkheads
¾” plywood bulkheads extracted from the CAD model slices were bolted onto the steel structure
Sanding
After sanding through the grits to 180, a sacrificial stain coat was applied and fully sanded off to remove all the scratches.
First Layer of Glass
One layer of 4oz fiberglass boat cloth followed by 3 coats of epoxy was applied to minimize movement and cracking at the seams
First Layer
First layer of 6mm meranti marine plywood for cold-molding the staircase.
Screen Shot 2021-02-17 at 1.19.58 PM
Varnish
Buildup coats of gloss varnish over epoxy
Final
Final varnish on a staircase part
Steel Runners
Inner cladding sets on steel runners and is held to the glass by French cleats bolted between the glass seams.
Waterline Square
The bridge is under the garden connecting these two buildings, One Waterline Square, Manhattan
Crane
Craning the first piece in place.
Finished
Glass
Final wood and glass install.
