with a variety of “fixes” being carried out, none of
which had a meaningful effect. Needless to say, Chris
and his crew nailed it once they got their hands on the
running gear, quickly discovering a serious, inherent
manufacturing flaw.
SHOP TALK
We walked to the back of the shop, to what I call
the tool crib, where Chris showed me Straight Line’s
primary weapon in the war against misalignment, a
series of precision optical scopes. Traditionally, these
scopes are used for land surveying, in the industrial
world for setting up alignment on equipment, and even
large gaps in the world of shaft alignment) are possible.
An optical alignment will get within .003 to .005 of
an inch. Lasers also require careful handling to avoid
eye damage. While I still believe lasers are an effective
alignment tool, especially for shorter shaft lengths,
and considering their return on investment (they are
comparatively inexpensive), that explanation made the
advantages of optical alignment crystal clear. Now, I
wanted to see it in action.
Left: The target for optical sighting, note the cross hairs. Right: Lasers like this are used for determining how much a vessel’s hull
moves, and accounting for it, during the hauling process.
inside very large ships’ engines. They are essentially
telescoped with a set of cross hairs—similar to a rifle
scope. Optical targets are 2-inch diameter pieces of
glass with micro-line cross hairs in the center. In the
hands of a seasoned professional, the optical scope can
deliver accuracy that is simply sublime (if you are an
alignment junkie like me, that is).
Many folks, myself included up to this point, have
the impression that a laser is, well, a laser beam. It’s
precise, as in laser precision (you don’t hear folks
say, “It has optical precision.”) I posed the question,
“Why is optical better than a laser, the latter being
my alignment tool of choice?” Chris was quick to give
lasers their due, but he pointed out several advantages
to using an optical scope over a laser, explaining, “A
laser alignment system uses similar principals—optical
targets creating a line; however, the level of accuracy
is lower. A laser spot is projected onto a target or
surface like a transmission flange center fastener. In
larger yachts the stretch distance between laser and
optic may be 20 feet or more, which creates a laser
spot up to 1/8-inch in size. The human eye struggles
to see the center of a dancing laser spot. As a result,
error rates of .050 to . 100 of an inch (comparatively
and how I could focus on different targets up the
scope’s line of sight (each target representing a bearing
location, you can’t do that with a laser), I was sold.
This is the ultimate in assessing the precision
of a running gear installation. Of course there’s
more to it than this. You can read the description of
the process in its entirety on Straight Line’s website at
http://highseasyachtservice.com/technical-articles/
optical-scope-alignment-the-basics.
