Lifeline stanchions take a terrible beating. Theyre long, thin and almost impossible to install with any pretense of engineering integrity. They might have been designed as levers to pry open a deck. In fact, whenever someone shoves a boat off a dock with a hearty thrust to a stanchion, thats exactly what can happen. In a fiberglass deck, stanchion movement can cause crazing and cracking in the gel coat. In a wood deck, movement will strain the fasteners and loosen the base, disturbing the bedding compound that forms a vital waterproof seal.
In each case, saltwater and rainwater leaks result. Telltale brown stains then will appear inside lockers, above the pilot berth, or on the cabin liner, usually (but not necessarily) directly beneath a stanchion. Leaks can run along stringers and liners, emerging some distance from the source. But leak damage isnt just cosmetic. It can rot interior woodwork or saturate a deck core, leading to delamination, structural degradation and costly repairs.
A leak signals that you need to rebed your stanchion bases. If they were properly fitted in the first place, this is not a big job. You can do one at a time, but its wiser to rebed them all at once. When one springs a leak, chances are the others wont be far behind.
Some stanchions are two-piece affairs with separate bases and upright posts. Some are bolted through the base plate only and others are reinforced with attachments to a bulwark or high toe rail (which makes them substantially stronger). Whatever the make-up, these are the key elements of good stanchion installation:
- Backing pads spread stress loads.
- Flexible bedding compound seals joints against leaks and, in a cored deck, sealed bolt holes keep the core dry.
- Stainless steel bolts/nuts/washers give strength and security.
Keeping these basics in mind, heres a step-by-step guide to rebedding a stanchion base:
Remove the wire lifelines. Remove the stanchion from its base (if the two are not integral) by unscrewing the retaining nuts or removing the cotter pins. Lay it aside. Place masking tape flush alongside the edges of the base and tamp down firmly.
Remove interior trim or headliner to expose the nuts holding the stanchion base in place. Remove the nuts with a wrench. You may need a helper on deck with a large screwdriver to stop the bolt from turning. Withdraw the bolts and inspect for pitting or crevice corrosion. If need be, replace with new stainless steel bolts of the same size (but at least 1/4-inch in diameter).
Lift the stanchion base from the deck, prying gently with a wide screwdriver if necessary. Gently scrape bedding compound off deck and bottom of base. Wash away remaining bedding compound with solvent (paint thinner or mineral spirits if it was an older, linseed oil-based marine putty such as Dolfinite bedding compound; or acetone if it was polysulfide or silicone).
Thoroughly sand the deck inside the masking tape with 120-grit paper, taking care not to sand the tape itself, protecting it if necessary with a piece of Formica or similar held in place. Sand the bottom of the base, too.
If necessary, prepare a new backing plate. For materials, use at least 3/32-inch-thick stainless steel, 1/8-inch aluminum or 3/16-inch marine plywood. It should be 50 percent longer and wider than the stanchion base, if possible. Place the base on top of the backing plate and mark for holes. Drill holes in the backing plate 1/16-inch larger than the bolt diameter, to allow for bolt drift.
For decks cored with balsa or foam, and if the edges of the bolt holes have not been sealed with epoxy to prevent water ingress, there is an additional step to insert here. With a drill, ream out the existing bolt holes through the deck about 3/32-inch larger than the bolt diameter. Tape the bottom of the holes, but prick a small hole through the middle of the tape with dividers or a large needle. Mix a small quantity of epoxy resin with a bonding powder to the consistency of peanut butter and fill the bolt holes, forcing the resin down from the deck until a tiny worm of putty squeezes through the air holes in the tape. Allow the epoxy to cure. Then, using the base plate as a template, carefully re-drill the original-size holes through the middle of the epoxy.
Cover the deck area outlined by masking tape with a generous layer of polysulfide sealant such as Boatlife’s Life Calk or 3M 101 marine sealant. Silicone may also be used to bed the base, but polysulfide is the preferred sealant. Polyurethane bedding compound should not be used because it is a powerful adhesive that makes subsequent removal of the base difficult, and will likely cause structural damage to the deck. (Note: Sikaflex claims this effect won’t occur with its less adhesive 231 polyurethane formula and says it’s suitable for bedding deck fittings.)
Smear the bottom of the base with a layer of polysulfide sealant. Also smear sealant under the heads of the bolts. Place the base in position and drop the bolts through. Line up the slots in the bolt heads as required, but don’t turn the bolts again or you’ll destroy their waterproof seal. All tightening will be done from inside.
Down below, fit the base plate and the washers, and screw on the nuts while a helper holds the bolts in place on deck. Tighten the nuts only until a fat bead of compound oozes out all around the edges of the base. Remove the excess compound with a putty knife or scraper and a rag soaked in mineral spirits, then smooth the sealant against the edges of the base with a finger or a plastic spoon.
Allow the sealant to cure according to the manufacturer’s instructions. This could take anywhere from 48 hours to a week. With a helper again on deck to prevent the bolts from turning, tighten the nuts home one by one. Replace the stanchion post in its base and rerig and tension the lifelines.
Stanchions rebedded in this manner will provide many years of good service and add substantially to the security of the deck lifeline system.
The American Boat and Yacht Council suggests that the entire lifeline installation be capable of withstanding a ÒstaticÓ force of about 600 lbs.
In his book Surveying Small Craft, British author Ian Nicolson warns owners to watch out for stanchions secured with screws. All deck fittings should be thru-bolted, he says.
Furthermore, as far as stanchions are concerned, surveyors agree “that there should be underdeck pads to take the nuts and washers, almost regardless of what construction material is used. Mass-produced boats need adequate checking, because there is a tendency to omit these pads or locate them carelessly so that the bolts do not pass through the pads.”
Nicolson advocates using backing pads on top of the deck, between deck and stanchion base, and below the deck.
Dan Spurr, author of Upgrading The Cruising Sailboat, warns that stanchions should be made of stainless steel pipe, not tubing, and should have lock nuts under the deck. “Stanchions should be welded or thru-bolted to their bases, because Allen set screws only dimple the metal, at best, and are not very secure,” he writes.
To keep the exterior of the stanchion base smooth or to prevent damage to a chromed base, you may want to drill only the stanchion. Mark the position of the set screw with the stanchion in place. Remove the stanchion and center punch the spot, then drill and tap it to receive a machine screw. To use the Allen set screw, drill partially through the stanchion to provide a recess into which the set screw can securely sit. Always use LokTite or a similar product on the threads of the bolts, machine screws or set screws to keep them from working loose.
If there are only three holes in a round stanchion base, locate two holes inboard, Spurr advises. The stanchion will better be able to withstand a sudden outward thrust.
John Vigor is a regular contributor to Cruising World