GRP-PETP self-aligning bottom roller bearings type 6T

The applications for the 6T series bearing:
The 6T series bearings combine a very simple installation with a very smooth operation under all circumstances as the bearing will always be aligned to the rudder shaft. The bearing is made of PETP (also known as Arnite, Ertalyte, Sustodur & Ultradur) in a GRP tube, allowing it to be laminated directly into the hull. A separate rudder tube is not required as the bearing housing is designed to extend above the boats waterline. It must be sealed to the rudder shaft with a gaiter. In the case of female moulded production boats the bearings housing can be mounted into the hull mould before lamination and gel coating begins. After gel coating the hull is laminated as usual with the exception that the hull laminate runs up the side of the bearing housing. This means that the bearing is already installed in the hull upon de-moulding, thus providing an integrated rudder support, and saving production time. It’s advisable to add some webs around the bearing to allow the rudder forces to be spread on the hull. As the bearing is self-aligning, there will be no torque transmitted to the hull, just rudder forces and the bearing will never try to twist out of the hull. The bearing ball can be easily dismounted out of the housing for installation safety or replacement when any damage in the future may happen.

Installation of JEFA Marine composite bearings in female moulded hulls:

1. The GRP tube of the 6T bearing is delivered with a shiny resin surface. To achieve a good bonding to the hull it’s important to roughen the outside surface with a grinder or sanding machine so no shiny surface is left. This should be done just prior to laminating the bearing to the hull.
2. Secure the bearing-housing in it’s place in the hull. The bearing should be jigged in place firmly so that it won’t alter position when worked during lamination and remove the bearing ball to make sure no resin will enter the rollers.
3. Tape a bag over the top of the bearing to cover the entire bearing neatly.
4. Gel-coat the hull.
5. Just prior to lamination, carefully remove the bag.
6. Laminate the hull making sure that the laminate runs up the side of the bearing in full thickness. It can be tapered down over a 100 mm span beginning just above the self aligning bearing in the bearing tube.
7. There should always be a skin joint around the bearing that is at least three times the bearing housings measurement in diameter, and the laminate should have a minimum thickness of 1.5x(1.8+(LWL/1.8), this thickness is not including the foam ram mentioned bellow.
8. When laminating the hull the first 10% of the prescribed laminate should be laid directly into the hull to bearing housing joint. On top of this “outer skin” there should be a foam ramp or fillet (minimum 200 kilo/m3 density), which encircles the bearing housing. The remainder of the laminate runs up over the foam ramp.
9. When the hull is de-moulded and the deck bearing is ready for installation the bearing ball can be inserted into the two slots in the bearing housing and rotated into place.