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those parts in the lower part of the top sphere. An acoustic Desired iron anchor air weight = Desired iron anchor release board or countdown timer release with their batteries water weight x (7.9/(7.9-1.03)), or approximately: could also be in a sphere further down the stack, with just the Desired iron anchor air weight = Desired iron anchor transducer placed in an unobstructed position to see upwards. water weight x 8/7

It could also occupy one of the spheres in one of the Auxiliary

Side Pods. Thus, if a desired iron anchor water weight is 10-lbs: • Sizing the descent weight: Fixed counterweights, lead or 10-lbs (water weight) = 10-lbs x (8/7) = 11.4-lbs air steel, are added to position the upper half of the top sphere out weights of the water. The water weight of the descent weight, most of- ten a stack of iron barbell weights, is approximately equal to the This provides the same force pulling the lander to the sea? oor positive buoyancy of the full upper sphere. as it will have coming back up. A ? rst approximation: a 10” sphere is 9-lbs positive, so a minimum 11.5-lb air weight iron

Water weight of a solid material is calculated as: descent weight should be enough if half of the top 10” sphere is Water weight = Material weight x ((Material Speci? c above water. A thirteen-inch sphere is 24-lbs positive. A mini-

Gravity-1.03)/(Material Speci? c Gravity). mum 28.5-lb air weight iron descent weight should be enough if half of the top 13” sphere is out of the water. A 17-inch sphere If iron has a speci? c gravity of 7.9, and seawater is is 57-lbs positive. A 65-lb air weight iron descent weight should 1.03, a 10-lb iron anchor in air will weigh 8.7-lbs underwater. be suf? cient if half of the top 17” sphere is out of the water. If bottom currents are suspected, an additional 20% weight could

Alternately, to calculate the air weight of an iron anchor of a be added to keep the lander from hopping across the sea? oor.

desired water weight: We discussed ferrocement anchors in the January 2022 MTR, • Bathymetry • CTD & Environmental • Current • Sound Velocity • Tide • AUV, ROV & ASV • HYDROGRAPHY • HYDROMETRY • METROLOGY &

SWiFT CTD POSITIONING

Measured CTD, with all the • OCEANOGRAPHY • PORTS, HARBOURS bene?ts of the SWiFT & DREDGING • RENEWABLE ENERGY

To find out more contact [email protected] +44 1803 869292 | www.valeport.co.uk www.marinetechnologynews.com 23

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