Bent Shaft and Strut – Too Bent to Repair?

2011 October 21
by Chris Brown

Straight Line Marine is a machine shop dedicated to running gear and the art of repairing bent shafts and struts. When looking at bent shafts we often get the question – is it too bent to fix?  The answer is simple – if it is not cracked then it can be straightened.  A cracked shaft is not repairable (focusing here on stainless steel marine shafts) and must be replaced. A bent shaft can be repaired. We use a cold, hydraulic press process that does not alter the metallurgy of the shaft. It takes a lot of practice and time to straighten a shaft. Some shafts have metal memory and need to be checked hours or a day later. If the shaft is bent badly enough (over 1/2″) we will run a red dye crack test when the straightening is complete. Unlike this experience straightening bronze struts, we have not had a shaft crack during the straightening process.

It is hard to imagine a 4″ shaft bending almost 1.5″ at the prop taper and even more difficult to see in a picture.  So here is a quick video showing one of our extreme projects.  This shaft was out of a 112′ Westport that ran hard aground.

The bent shaft was not the only damage – the V-Strut legs were “waffled” as it was pushed straight up towards the vessel’s bottom.  Straightening both legs took quite a bit of enginuity with a series of hydraulic presses.  We did save the strut and reinstalled it with an optical scope alignment.

Strut bent after running aground

Bent strut from a 112' Westport

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