![]() 316 stainless steel and Monel rivets are more than twice as strong as aluminum and do well in the marine environment, but both require a pre-installation coating of Tef-Gel, a PTFE paste, to reduce the risk of corroding the aluminum. Aluminum rivets won't cause corrosion due to dissimilar metals, but they are the lowest strength. ![]() Blind rivets for marine use can be made out of aluminum, Monel (a nickel/copper alloy), and stainless steel. Your choice here will be between machine screws and blind rivets.īlind rivets are the easiest, although you'll need a riveting tool. But sheet-metal screws should never be used to fasten hardware to extruded aluminum spars (masts, booms, spinnaker poles, and so on) because sheet-metal screws are designed to be held in place by a single thread and are not meant to cut threads - they distort the walls of the hole into a helix. So whether installing screws into solid laminate or through a fiberglass skin into a core plug of cured epoxy, use stainless-steel sheet-metal screws. Sealants won't prevent water from reaching and ultimately destroying core. In all cases, core around the fastener must be removed and replaced with epoxy putty sufficient to isolate the core from the fastener hole. You should never screw any type of fastener into (or through) core material. If you think an underlying wood core alters this, you are doubly wrong. Wood screws are for wood only, never fiberglass. This would include things like deck fills, ventilators, rod holders, flagpole sockets, and running lights. Hardware of lesser import or subject to little stress can be fastened with screws. In addition to nuts on the backside of the fitting, through-bolt mounting should include a strong backing plate made out of aluminum or stainless steel or, at the very least, heavy fender washers to spread the load.īesides eyes, cleats, and pedestals, the items that need to be secured with bolts that pass through the deck or hull include handrails, windlasses, and safety rail or lifeline stanchion bases davits, cranes, and pole mounts wakeboard towers and ski pylons and for sailors, winches, travelers, and headsail tracks. Bolts or machine screws must be used to secure any component or piece of hardware essential to boat function and/or safety that might experience a load that will or could pull or pry it from the boat. Threads cut by wood screws into wood, or by sheet-metal screws into fiberglass, lack the strength, consistency, and durability that machined threads inside a metal nut or other thick metal component can provide. In general, the weak link in the attachment of a fastener is the internal threads that the fastener's external threads engage. Pedestal seat bases pry up mightily on their forward fasteners, then on their aft ones as your body weight shifts in a chop. When the tide goes out, docklines start to tug upward on cleat fasteners. ![]() ![]() The load on lifting and towing eyes is almost entirely tensile - it is trying to stretch the fasteners or pull them from their holes. But with a tensile force pulling the fastener straight out, holding strength becomes increasingly dependent on the threads (or formed head in the case of rivets) holding the fastener in place. Any metal fastener will hold well against a sideways (shear) force. Selecting the right fastener (see below) begins by assessing the load that will be placed on it. Select wisely and install carefully to ensure your fasteners hold to their maximum strength. Metal fasteners set the bar for strength, offer unmatched longevity, and most can be disassembled without destruction. Most of the time, though, mechanical fastening will be the attachment method of choice. Today we have astounding glues that are stronger than the materials they bond, and some tapes are capable of joining railroad cars. Anything you want to attach to your boat has to be fastened in some way.
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