Tips for Underwater Mooring
Bottom Mounting
In a bottom-mounted system the DSG is attached to an underwater mooring, which can either be a weight such as a cinder block. Note that cinder blocks on their own are not heavy underwater, and can be moved by strong currents. So, multiple blocks should be used and connected by chain. Weight can also be increased by filling cinder blocks with instant cement.
Mounting on a Subsurface Line
The DSG can be attached to a sub-surface line. For this setup use a heavy mooring or tie-down anchor (if the bottom is sediment), and attach a bouyant float to the top of the line. Note that many floats will compress under water pressure. Inexpensive hard floats can be made from sealed PVC or purchased from fishing supply houses.
Attach the DSG to the line using 316 stainless steel hose clamps. Protect the line with tubing or PVC where the attachment will be made. Lines easily chafe and fail underwater under stress and long deployments. Typical failure points are at the mooring and the site of attachment.
Safety Lines
A safety line should be attached to the mooring and then run slack to the main line holding the DSG or to the DSG itself. If the main line breaks the safety line will keep the DSG attached to the main mooring.
Hardware
For all attachments using stainless steel, use type 316 Stainless Steel. Note that on aluminum housings it is best to not have stainless steel directly contact the aluminum housing, because it can increase galvanic corrosion.
Bottom Paint
The use of anti-fouling 'bottom' paint is helpful to minimize growth. A small coat on the hydrophone will not significantly affect sensitivity, and is much better than having barnacles growing on it.
Note that on aluminum housings be sure to use bottom paint designated for use on aluminum.
Avoiding Noise
Chain: If using chain underwater, wrap duct tape around the entire length to prevent the links from clanging together
Anything that touches the hydrophone or hits the housing will create noise in recordings. Be aware of stray lines or anything that could rub against the hydrophone.
Resources
McMaster-Carr supplies a wide variety of hardware helpful for mooring, including 316 Stainless steel hose clamps and wicked huge cable ties (get the black ones, which are UV resistant).
Support
Please contact us with technical questions and concerns by email or telephone at any time.
Email: dmann@loggerheadinstruments.com
Phone:
941-923-8855 (office)
941-321-5437 (cell) (941-321-LGER)