Self-aligning PETP lower roller bearings type 6T


Type 6T000 bearing

The table below shows all key dimensions of the 6T series self-aligning PETP-GRP bottom roller bearings. The measurement D is the outside diameter for the sealing gaiter. 
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PART NO.

RUDDER SHAFT dia. "d"

TUBE dia. "D"

HEIGHT "H" *1

WEIGHT

WORKING
LOAD (max)

6T030 - 6T045

30 to 45 mm

90 mm

max. 1000 mm

1.7 kg

1300-1800 kg

6T046 - 6T060

46 to 60 mm

110 mm

max. 1000 mm

2.1 kg

2500-3200 kg

6T061 - 6T072

61 to 72 mm

130 mm

max. 1000 mm

2.8 kg

4200-4800 kg

6T073 - 6T095

73 to 95 mm

150 mm

max. 1000 mm

3.3 kg

4900-6200 kg

6T096 - 6T125

96 to 125 mm

180 mm

max. 1000 mm

4.3 kg

6300-8000 kg

6T126 - 6T162

126 to 162 mm

210 mm

max. 1000 mm

5.1 kg

8100-10100 kg

6T163 - 6T210

163 to 210 mm

260 mm

max. 1000 mm

7.5 kg

9900-11500 kg

*1: Longer tubes are available at a surcharge.

6T specification form:
Please click the left icon to open the 6T000 specification form in Adobe PDF. You can fill in the gray field with the correct info and tick the appropriate boxes. This form is required to guarantee a correct production of your bearing.

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.

Please remember that these guidelines represent good practice, however all structural components of a sailing vessel should be engineered by a qualified engineer for the actual case. JEFA MARINE takes no responsibility for any structural failures which might result from the use of these guidelines.


Installing the 6T bearing is a ready made hull:

Installation of JEFA Marine composite bearings in ready made 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. Make sure the hole in the hull is a few millimetres bigger than the bearing outside diameter and tape close the gap at the bottom.
  4. Cast some resin in the gap to close off the hull laminate .
  5. Laminate the hull and bearing creating an outer skin. It can be tapered down beginning just above the self aligning bearing in the bearing tube.
  6. On top of this outer skin there should be a foam ramp or fillet (minimum 200 kilo/m3 density), which encircles the bearing housing. Make a wooden circular tool to create a nice fillet.
  7. Laminate the hull and bearing 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.
  8. 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. (LWL in Meters).
  9. In stead of using a filled around the first outer skin, one can also make a web of triangles which will be included in the final lamination (see model below).

Please remember that these guidelines represent good practice, however all structural components of a sailing vessel should be engineered by a qualified engineer for the actual case. JEFA MARINE takes no responsibility for any structural failures which might result from the use of these guidelines.


Installation example of the 6T bearing not using a fillet for stiffness but a web structure

6T examples: