Schock 40 Keel
The Metallurgist's Report

By now many of you are familiar with the story about the keel falling off of builder Tom Schock's own Schock 40 SchockaZulu. Much speculation sprang forth (mostly on these pages), but we wanted an official verdict, and here it is courtesy of Tom. - The Ed.

Dr. Praful Patel, the metallurgist at Smith Emery, has determined that the strut of SchockaZulu broke off because of four cracks in the welds. One crack was 1-1/2" long, one was 1-1/4" long, and the other two were about 1/2" long. The cracks represented about 25% of the welded area and had not propagated. There was corrosion in the cracks, which led Dr. Patel to believe the cracks were old. He also concluded that the part would not have failed if the cracks had not been there. Dr. Patel confirmed that the weld is proper for the job and that there was no fatiguing of the metal. The heat treatment was also proper.

SchockaZulu hit a rock soon after it was launched. We hauled the boat after this incident and found that the lead had a good scratch in it. There appeared to be no other damage, but we didn't look at the weld. Because she is kept in a very shallow section of Newport Harbor, SchockaZulu also ran aground in the mud in Newport Harbor on two occasions and one more time in Long Beach. These occurred at very slow speeds.

Based on Dr. Patel's findings, we feel confident the strut on SchockaZulu broke due to damage sustained when it hit that rock off the Long Beach jetty. The mystery, though, is why it waited until 20 months later to fall off during 8 knots of wind. Why didn't it break during the 2001 and 2002 Santa Barbara to King Harbor Race, or during the 2002 Ensenada Race?

Based on this experience and the findings of Dr. Patel, it is apparent that a die pen test of the weld should be conducted following any impact to the center strut. Matt Brown has written instructions that include a drawing that shows how to access the weld through the fairing. The test is not difficult to perform.

The strut on the Schock 40 is designed to break away before the leverage of the strut and torque shaft can put a hole in the hull. It is definitely better to have a damaged boat float upside down than to have it sink. Unfortunately, there is no way to determine just how hard you have to hit something to do this kind of damage.

SchockaZulu is looking as good as new and will go back into the water March 21.

Tom Schock

W.D. Schock Corp.
23125 Temescal Canyon Rd.
Corona, CA 92883
www.wdschock.com
schock@wdschock.com
909-277-3377