Optical alignment projects Summer of 2015 optical alignment

USCG Kiska, Honolulu, optical alignment check

It's been a busy 2015, including a trip to Hawaii to perform an optical alignment check on the USCG cutter Kiska, in Pacific Shipyard International's drydock in Honolulu. I have been in shipyards all over the world, and they all are pretty much the same- except sometimes you get a spectacular background like this. Kiska is a 110' cutter based in Hilo on the big island of Hawaii. I am familiar with the 110's as they are regular visitors to the Tampa area yards, and generally are straightforward shaft systems.

Optical alignment

Pacific Shipyards International did some preliminary checks with a target wire, and I went out to perform an optical alignment check on the bearing, stern tube, and reduction gear alignment. A quick trip to a beautiful place, and it is always a pleasure to meet and work with the men and women of the Coast Guard. They need the best equipment and support possible, they do a dangerous job with aplomb and enthusiasm, and I am honored to be asked to support them by providing fast and accurate onsite service.

Fitting targets

I fabricate precise target holders like the one in the picture to hold the optical alignment targets, and they are sized to fit the various standard and metric shaft sizes encountered. Sometimes custom targets are required, but there are a lot of stock sizes. Slight differences can be made up with feeler gauge stock, or bar stock turned to a precise diameter, or as in the picture standard thread pitch gauges can be used. Stern tubes without bearings, like the one in the picture have different degrees of tolerance. Lip-type seals are the most flexible, and face seals need to be both centered and plumb to keep the two faces parallel. Generally as long as the shaft is reasonably close to the center of this type of stern tube it's ok, but some shaft systems have no tolerance for any misalignment at the stern tube, even without a bearing. It all depends on the type of seal.

Rip or tear and delamination in a cutless bearing

This is a shot of the 11" bearing on a 210' USCG cutter, Confidence. While there is plenty of rubber remaining, you can see the separation of the rubber bearing surface from the brass shell, adjacent to the tear in the bearing. In relative terms this may not appear to be large damage, but once a condition like this is noted the prudent step is to replace the bearing. The cost of the bearing is small compared to the cost of delaminating completely in service.