Report KD 684 has been added at the menu KD-reports. The tittle of this report is: “Derivation of the formula for the cone angle epsilon for a constant chord blade which is connected to the hub by a hinge”. The formula for the cone angle epsilon was already derived in report R 409 D from 1980 but as this report is written in Dutch and no longer available, the derivation is now given in this public report KD 684. The formula is used to calculate the bending stress at the blade root of for instance the VIRYA-3B3 rotor as described in chapter 8 of report KD 484.