Nitronic Stanchions


Stanchion DrawingJay Paris

With the investments of time and treasure and a little help from my friends, my 32 (9.75m) sloop, Petrel, has enabled me to realize many long-contemplated and refined design concepts, among them these minimal-windage lifeline Nitronic stanchions made from the high-strength, corrosion-resistant 22-13-5 alloy (also sold as Nitronic 50).

Petrel’s distinctive lifeline stanchions were fabricated from 0.59-diameter (15mm) Nitronic 50-60 rod rigging. The choice of material was informed by an earlier event that I had heard about. When Ken King was the head of rod-rigging supplier Navtec, he made Nitronic stanchions for his boat. On one occasion they tangled with those of another boat. The stanchions on both boats bent back until they disengaged; reportedly, King’s sprang upright, and the other boat’s remained bent.

Stanchion rodsJay Paris

The comparison of a 1″-diameter stainless-steel tube for a conventional stanchion with the Nitronic stanchion fabricated from rod illustrates the latter’s approximately 40% reduction in windage. The taper of the upper portion of the rod is just visible where it is not shown on the original drawing above.

While that anecdote underscored the practical serviceability of the material, my primary design objective was to reduce windage from conventional 1-diameter (25mm) stanchions. My planning included a 3⁄16-thick (5mm) base plate and a 1⁄16 (2mm) addition to compensate for deck camber so that Petrel’s upper lifeline is 24 (610mm) above the deck.

The first task in fabricating these Nitronic stanchions was to straighten the Nitronic rod rigging, which is shipped in coils. Before use, the stainless alloy must be fed through a straightening device, which any rigging shop that fabricates rod rigging would have. Once it was straightened, my friend Steve Loutrel, Navtec’s director of engineering, and I measured the stock to length and cut it. We did all this on specialized equipment at Navtec’s Littleton, Massachusetts, facility, but the cutting to length could have been accomplished with a grinder cutoff wheel. Next, we used Navtec’s powerful hydraulic press to create flats in the rod that would be drilled for the upper and middle lifelines. Note, this is not a process rod rigging is commonly subjected to.

The upper lifelines are 3⁄16-diameter 1×19, and the middle ones 1⁄8-diameter (3mm) 1×19. For both, I used antimagnetic Nitronic 50 1×19 wire that had been produced for the U.S. Navy for use on minesweepers but is no longer available. Its advantage for lifelines was that there is no worry about corrosion inside their end fittings.

Lifeline WireJay Paris

Flats hydraulically pressed into the tapered Nitronic rod at Navtec were later drilled to accommodate Nitronic 50 wire lifelines.

To reduce stanchion windage, the portion between the middle lifeline flat to the upper one was tapered from 0.59 diameter to 0.50 (15mm to 13mm) by machining the almost-complete stanchions on a lathe at Aeromarine’s Brunswick, Maine, shop. The resulting stanchion has 12.36 sq in (79.7cm2) of area exposed from forward. That’s just 59% of the area of a comparable 1-diameter tube. Note that my overall windage calculation does not include the bottom 3 (76mm) of the midships stanchion masked by the bulwark.

Each Nitronic stanchion weighs 1.74 lbs (0.79 kg), which is 94% of a 3⁄32/2mm-wall 1-diameter stainless-steel tube of the same length. And when it comes to comparative durability, I have in my inventory some old 1⁄16-wall stanchions that had been overloaded in service, leaving them bent in way of the holes for the middle lifelines.

Jay Paris

The stanchion bases were fabricated on a jig that adjusts for custom angles so stanchions are perpendicular to the water despite variations in sheer and deck camber where they mount.

The Nitronic stanchions are attached to the deck and bulwarks with stainless stanchion bases custom-fabricated to fit the structure and angles in the six locations where they are installed. The welding jig, shown above, holds the vertical tube that receives the stanchion and its attached elliptical plate for fastening to the bulwark. It is adjustable for each of the six stanchion configurations. The bent piece of rod just visible behind the jig is inserted into holes to change the weld angle to match the sheer.

Stanchion BaseJay Paris

Elliptical plates bolt firmly to the deck and bulwarks.

The next step was attaching the elliptical base plate for bolting through the deck, followed by a diagonal bracing rod that holds the base rigid to the angled mounting plates.

The upper bulwark fastenings are threaded into 3⁄4-long (19mm) silicon-bronze inserts epoxied into the 1-thick bulwark.

The lifelines terminate aft at the forward upright portions of the two U-shaped handrails, which serve the same function as stanchions. The lifelines are tensioned forward where they are lashed to the bow pulpit with multiple passes of Dyneema line.

About the Author: For more than 60 years Jay Paris has been a naval architect, oceanographer, winch designer for ocean racers and AC 12-Meters, author, and technical editor. His yacht designs include the 1968 Aeromarine 50, the first U.S. Airex-cored boat, which had unidirectional glass skins; the Freedom 33 cat ketch; and the P-32 Petrel. Many of Paris’s designs were made to illustrate his numerous articles and lectures.