The International Association of Lighthouse Authorities (IALA) has endorsed a mooring line calculation software package called CALMAR, designed by world leading buoy manufacturer Mobilis. (1st July 2014)
Mobilis have supplied the marine industry with robust, IALA compliant and cost-effective navigation, mooring and zone marking buoys for over 20 years, which are exclusively supplied to the UK by Hydrosphere UK Ltd. Mobilis developed the numerical catenary mooring line calculator to enable quick and easy evaluation of all the environmental forces acting on a moored buoy. In the past, AtoN buoy mooring lines have often been dimensioned with the rule of thumb “use chain length three times the water depth”. This however, does not take into account the various drag forces exerted on the buoy and mooring by maximum site environmental conditions or the linear mass of the chain – both of which make a considerable difference to the necessary catenary length. As a result, moorings have regularly ended up being too short for most sites when weather conditions deteriorate.
Based on Mobilis’ own mooring calculation bank, the new IALA approved software integrates more load parameters than other calculators, taking into account factors such as absolute maximum depth of water and even increasing drag coefficient due to biological fouling on the buoy hull and chain, which allows for the exact equilibrium of buoy displacement, lifted catenary chain loads and horizontal drags to be calculated.
David Henry, Naval Architect for Mobilis has said, “At Mobilis we have been calculating moorings using a full analysis method for more than 20 years and have not experienced a single buoy mooring line breakage over several thousand buoy mooring specifications.”
CALMAR allows users to input or use libraries of buoy models or easily build their own buoy model for calculation, as well as compare the results between two different buoys or two different buoys’ mooring lines.
This software is being offered for free distribution and is available to download here.
An article about CALMAR has been published in the January 2014 edition of Bulletin, IALA’s quarterly magazine. Visit the IALA website.
More information on CALMAR can be found here or on the Mobilis website.