Building an in-water counterweight system to provide more flexibility than the No Bubbles/AIDA NZ catamaran mounted above water system.
I have a couple of issues I would like to get some feedback on from others within the forum.
1. The spreader bar - keeps the counterweight away from the dive line. How long is long enough to prevent a 'sailing' counterweight from getting around the dive line during deployment given:
- We generally use the system in a lake with minimal current action
- We use lead as a counterweight.
- Depth up to 100m+ although ususally <60m CWT/CNF/FIM
- We use a 16mm polyester braid line although it is possible that we may switch to a lighter 8 or 10mm braid for the real deep stuff.
- At present using around 20KG CW, although may go heavier, particularily if diving FIM.
2. What to do with the 'tail' of the line where someone is diving shallow?
- In deep water the counterweight could be kept on the end of the line and lowered ie if an athlete is diving to an AP of 30m we either use another line or have the counterweight 85m down in the lake. However there is a risk that you drift into shallower water and the counterweight hits the seabed befor the athlete surface.
- The only way I can see to get around this is to always have the counterweight at the surface. This can be effected by fixing the counterweight to the middle of the line, but then what to do with the tail? Coiling the tail in the boat or floating free runs the risk of snagging, another way would be to place the excess rope tail in a bag or coiled around a frame that gets carried down with the counterweight but that increases hydrodynamic resistance.
- Another way would be to have a pulley on the counterweight with the tail tied off on the boat, however due to the 2:1 mechanical advantage this would create you would need to double the counterweight weight. I also have some concern that swivelling in the counterweight could wrap the two lines around each other.
Comments please
I have a couple of issues I would like to get some feedback on from others within the forum.
1. The spreader bar - keeps the counterweight away from the dive line. How long is long enough to prevent a 'sailing' counterweight from getting around the dive line during deployment given:
- We generally use the system in a lake with minimal current action
- We use lead as a counterweight.
- Depth up to 100m+ although ususally <60m CWT/CNF/FIM
- We use a 16mm polyester braid line although it is possible that we may switch to a lighter 8 or 10mm braid for the real deep stuff.
- At present using around 20KG CW, although may go heavier, particularily if diving FIM.
2. What to do with the 'tail' of the line where someone is diving shallow?
- In deep water the counterweight could be kept on the end of the line and lowered ie if an athlete is diving to an AP of 30m we either use another line or have the counterweight 85m down in the lake. However there is a risk that you drift into shallower water and the counterweight hits the seabed befor the athlete surface.
- The only way I can see to get around this is to always have the counterweight at the surface. This can be effected by fixing the counterweight to the middle of the line, but then what to do with the tail? Coiling the tail in the boat or floating free runs the risk of snagging, another way would be to place the excess rope tail in a bag or coiled around a frame that gets carried down with the counterweight but that increases hydrodynamic resistance.
- Another way would be to have a pulley on the counterweight with the tail tied off on the boat, however due to the 2:1 mechanical advantage this would create you would need to double the counterweight weight. I also have some concern that swivelling in the counterweight could wrap the two lines around each other.
Comments please
