When you decide to modify the keel fin and/or bulb there are several very important processes to adhere to so a smooth transition can be achieved for both the IRC and ORC Rating certificates.

For ORC it is essential to provide the Rating Office with the new design files in 3D CAD format. Our office can create a new offset file using the CAD data and replace the existing fin and bulb in the current offset file. While this office can complete the change of an appendage there is still the need to get approval from the ORC Chief Measurer and the new offset file reissued for ORCi. 

Once the work has been completed the boat will require re-inclining to determine the new stability. 

IRC requires additional records of the changes to the appendage. When collecting data for IRC ensure that the load cell used in calibration and has class “A” status in the range of loads being measured.

To ensure the weights are all correctly recorded the following should be done

1)    Weigh the fin and bulb before commencing work as a unit.
2)    Separate the components and weigh the fin in particular
3)    If the bulb is being machined record the weight when the machining is completed
4)    If the fin has been altered reweigh the fin when the work is completed
5)    Determine the weight of the fin plate either by weighing or calculation
6)    Finally, when the fin and bulb are reattached, filled faired and painted

The final bulb weight includes the fasteners and all fairing at the base of the fin and fin plate.

To learn about ORC and IRC ratings, click here.

By Chris Zonca