Cutlass Bearing “Float” Alignment

When a strut is out of alignment there are two approaches to correct the problem.  The choice of which approach to take was usually decided when the vessel was constructed.  Most fiberglass yachts up to a certain size have struts that are bolted to the hull.   Getting a proper bearing alignment for a bolted strut requires positioning the entire strut to get the bearing into alignment.  This was covered in the technical article here.

For steel or aluminum yachts the strut is welded to the hull.   It is almost impossible to weld a strut into position and obtain the necessary tolerances for a perfect alignment (within 0.005 inches).  Therefore the boat builder takes a different approach.  The strut barrel (the bottom of the strut) is constructed so the inner bore of the barrel is considerably larger than the outer diameter of the cutlass bearing.  The gap between the cutlass bearing shell and the strut bore can be 1/2″ or larger.  This allows the strut to be welded to the hull in roughly the right place and leave plenty of room to align the cutlass bearing at a later time.  This process is called “floating” the bearing.

If a floated bearing needs to be removed and aligned the process begins with removal of the bearing and floating material.   The bearing is cut out and the old float material is chiseled or ground out of the strut barrel.  A honing tool or whippy wheel cleans the strut barrel in preparations for new material. 

Set screws are placed in the wall of strut barrel in order to hold the cutlass bearing in alignment prior to the injection of new float material, .   You can usually find the original set screw holes that need to be cleaned and tapped.   Finally, there will be one or two holes in the strut barrel used for injecting the floating material.  Those holes need to be cleaned and tapped in preparation for injection ports (hose fittings).

With all the cleaning and prepartion complet it is time to install the new cutlass bearing.  We prefer to use non-metallic bearings in float aligned installations.  We do this to make it easier for the next yard to cut the bearing out, three to five years later, without damaging the float material.  The fiber shelled bearings are much easier to cut with a sawzall.   All set screws are run through the barrel.  The bearing is then suspended in place in the middle of the barrel and pinched or bound with the set screws.  The bearing is now properly aligned using the optical scope and adjustment of the setscrews.  When the bearing is in the final position the ends of the barrel must be dammed up in order to form a mold that retains the floating material.  We like to use a two part material such as Splash Zone or any heavy bodied filler material.

With the injection ports in place and the ends dammed it is time to inject the floating material.  Our favorite material in this application is Chockfast.   The Chockfast will be pumped into the strut barrel from the bottom injection port.  The upper port should be position at the highest point.   As the Chockfast is pumped in from the bottom, the upper port allows the air to escape.   You know the entire void between the barrell and the bearing is filled when the Chockfast apprears in the upper vent.  It is a good idea to use a long clear hose taped up high to give you a visual aid on the Chockfast without having it spill all over the strut, the floor and nearby employees.

The last step is clean-up.   Pull the hoses and injection ports.  Grind down any lumpy material.  Clean up the Cutlass bearing making sure none of the Splash Zone or Chockfast is in the rubber area.

This process takes quite a bit of practice and the right tools.  Without experience it is possible to spend a considerable amount of the owners money and not get a precision alignment.   Many companies do not have this experience and subsequently, they will remove and reinstall your shafts without ever looking at the alignment.    A proper alignment will result in longer bearing life, smoother rides, more comfort and better fuel economy.  Next time you need to have your shafts removed for maintenance or repair please find an experienced running gear company to look over the entire alignment.