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--part1_fc.1ada0b95.2a661f09_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 7/16/2002 2:28:05 PM Eastern Daylight Time, xdream2000@ho*.co* writes: > I have a general question and am in need of some advice on best practices on > the subject of rigging and lifting an object (pipe-like, slightly curved) > approximately 8' long and 1' in diameter (about 50 lbs total) off the > bottom. (Yes - it sounds like a pipe) The problem is more in the > stability > than in purely attaching enough bags. > The biggest problem when using more then 1 lift bag in a linear fashion (along the length of a piece, instead of on top of each other) is to balance the buoyancy of the bags. You are guaranteed to put just a little more in one bag then the other and end up picking up an end. As soon as this happens and the bottom suction is broken you will have most likely lost complete control and are now sending a rocket to the surface. Wait a few seconds and it will be coming back down, most likely on top of you. Think of the films of the US Submarine Squalaus in 1939. What happened was just that, one end got out of control. Instead, and if posable, you should try to plan a lift from one end. Then when the object picks up on the lift end there should be enough weight at the other end to keep it on the bottom and under control. Now you can add just enough air to get it going to the surface under control. Your greatest problems will be 1) Breaking the bottom suction without too much lift. To control the break free, try blowing air or water under the object with the minimum amount of air in the bags. 2) Rigging a harness that will not slip off on the way up. You could try a ratchet type nylon web strap. Once the object is on the surface you can attach a bag to the deep end and bring it level for a tow in or lift it onto the deck. If you are towing it by boat, I suggest using only pillow bags. Normal lift bags tow like shit. Pete Johnson --part1_fc.1ada0b95.2a661f09_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: 7bit <HTML><FONT FACE=arial,helvetica><FONT SIZE=2>In a message dated 7/16/2002 2:28:05 PM Eastern Daylight Time, xdream2000@ho*.co* writes: <BR> <BR> <BR><BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">I have a general question and am in need of some advice on best practices on <BR>the subject of rigging and lifting an object (pipe-like, slightly curved) <BR>approximately 8' long and 1' in diameter (about 50 lbs total) off the <BR>bottom. (Yes - it sounds like a pipe) The problem is more in the stability <BR>than in purely attaching enough bags. <BR></BLOCKQUOTE> <BR> <BR>The biggest problem when using more then 1 lift bag in a linear fashion (along the length of a piece, instead of on top of each other) is to balance the buoyancy of the bags. You are guaranteed to put just a little more in one bag then the other and end up picking up an end. As soon as this happens and the bottom suction is broken you will have most likely lost complete control and are now sending a rocket to the surface. Wait a few seconds and it will be coming back down, most likely on top of you. Think of the films of the US Submarine Squalaus in 1939. What happened was just that, one end got out of control. <BR> <BR>Instead, and if posable, you should try to plan a lift from one end. Then when the object picks up on the lift end there should be enough weight at the other end to keep it on the bottom and under control. Now you can add just enough air to get it going to the surface under control. Your greatest problems will be <BR> <BR>1) Breaking the bottom suction without too much lift. To control the break free, try blowing air or water under the object with the minimum amount of air in the bags. <BR>2) Rigging a harness that will not slip off on the way up. You could try a ratchet type nylon web strap. <BR> <BR>Once the object is on the surface you can attach a bag to the deep end and bring it level for a tow in or lift it onto the deck. If you are towing it by boat, I suggest using only pillow bags. Normal lift bags tow like shit. <BR> <BR>Pete Johnson</FONT></HTML> --part1_fc.1ada0b95.2a661f09_boundary-- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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