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History of the Retractable Keel Design

History of the Retractable Keel Design

One of several factors that helped the C-22 launch the trailer sailing market in the early seventies and earned her a place in the American Sailboat Hall of Fame was her superior retractable keel design. A unique system utilizing a pair of robust bronze castings is employed to secure the C-22’s keel into the boat. It is much stronger and more trouble free than any competing retractable keel boat’s system. It’s great for a boat to be trailerable, but even better for the keel to stay firmly attached and trouble free for long periods of time!

There were a number of small retractable keel boats being designed at the same time as the C-22. In fact several of them were sailing before the first Catalina 22 was launched on 1969. An early example of the genre was the Venture 17. Although its construction was quite light, it was a fast and fun boat to sail. Several other boats come to mind... The San Juan 21, Cal-21, Clipper 21 Aquarius 21 and 23. were all early examples. But they all suffered from one common flaw. Each had a swing keel secured into the boat by a simple but not well engineered system.

Most keels were installed with a large bolt which passed through the keel trunk, then a hole in the keel, then again through the trunk on the opposite side. Locking was achieved by using a second smaller bolt installed above the first. This simple system had a couple of major flaws 1) The pivot bolt was below the waterline. Try as one might, it is very difficult to keep it from leaking. There is considerable stress from both the ballast and the lateral loads from keeping the boat from sliding sideways while sailing. In a few months or a few years, the pivot bolt began to leak.

Running aground was a disaster for this design. With any speed at all the smaller locking bolt would do two things. The first thing to give was the bolt itself. It wouldn’t break, it would simply bend in a “U” shape making it impossible to remove. After it wouldn’t bend any more, the small diameter of the bolt would tear a perfect arc in the keel trunk, one on each side.

The result compromised the integrity of the hull and created a costly repair. Invariably, removing the bent locking bolt created an even larger hole through the keel trunk. Serious fiberglass repair was necessary on both sides of the keel trunk extending from the keel pivot pin to the keel locking bolt and beyond. By the time the boat was seaworthy again, many hundreds of dollars were spent on the repair.

Frank Butler realized that the retractable keel design could be improved. Somewhere around hull number 280 (there are no good records of exactly so don't take this number as gospel), the C-22 was equipped with a new keel pivot design. This design is superior in several ways: 1) It eliminates all below the waterline penetrations of the hull for the purpose of securing the swing keel. The system is leak free when maintained in good condition. 2) If run aground, the friction locking bolt slows the boat to a stop making it safer for the sailors aboard. 3) The design reduces the likelihood of damage. 4) Damage that does occur is accessible and inexpensive to repair. 5) Even damage from repeated groundings never compromises the integrity of the hull. 6) Keel removal and replacement is simplified. With the advent of the new design, the sales of the C-22 increased dramatically.


Keel Locking Bolt
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