Chainplate Bolts

The weak link in the rigging design, as delivered from the factory, is the choice of bolts that hold the chainplates to the bulkheads and knees. Bruce Rankin published an engineering analysis in the March 1992 Mainsheet and this is reprinted in the Maintenance Manual. I won't repeat the analysis here, but I will repeat the recommendation.

Increase the number of bolts from three to six or increase the size from quarter-inch to five-sixteenths-inch. Either will double the strength of the fastenings.

Add backing plates behind the plywood. We usually use quarter-inch by 1 inch by 6 inch long or so, in aluminum. Stainless would be better, but is impossible to drill in place.

Note also that these bolts should not be threaded down the full length of the bolt. Where the bolt passes through the chainplate, the metal should be full-diameter. This is called a shoulder bolt.

This Old Boat by Don Casey Subtitled "turn a rundown fiberglass boat into a first-class yacht on a shoestring budget," this book is the best introduction I know boat maintenance for the new or prospective owner of a "modern classic" sailboat. Starting with guidelines for selecting a boat, Casey proceeds to fiberglass repairs, cabin and deckwork, spars and rigging, boat equipment, woodwork, electrical, plumbing, refrigeration, painting, canvas work and sails. All of this is described in clear, simple terms perfect for the inexperienced. This is the book that taught me fiberglass work. But don't let it fool you; this book is appropriate for experienced boatowners, too. I still refer to it. Other books by Don Casey (Note: commissions earned from this link help defray the costs of this website)

• Chainplate Bolts
• Mast Base
• Running Rigging
• Rigging Measurements
• Rig Tensions

• Boat Maintenance
• Spars, Sails & Rigging
• Hull & Deck
• Deck Gear
• Steering
• Mechanical Propulsion
• Electrical
• Head
• Plumbing
• Accomodations
• Tools
• disorganized