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Homemade sled for 2

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Aug 17, 2004
Recently my brother has gotten into freediving and we have been going together on the weekends. When I used to go by myself, I had experimented with using weights to drag me down really quick. Quite by accident while trying out my pipe mask one day, he saw me doing this and took to the idea immediately.

A few weeks ago we went shopping and bought a 150' line with d rings on both ends, a 10# anchor and a rather large bouy. We took it out to the water attached one d ring to the bouy, one to the anchor and the two d-rings to each other. The bouy was strong enough to float the weight by itself, which was exactly what we had in mind.

I will probably be unable to dive for the next 6 weeks, and have been using this time to think and increase my co2 tol. One of the hardest things about the setup we have now is that you have to drag the anchor back up from the surface each time. So I have been thinking about that. I had bought a tarp, and was considering making a lift bag out of it. But ultimately that is a little troublesome.

Then the other day I saw a post on here about a diver retreival system. And that got me to thinking about how to make a variable weight system for two that would bring one weight to the top as the other one descended.

I realize right off the bat that the system will try to attain equilibrium with both equal weights at the same depth.
But if you are starting from the high entropy scenario with one weight fully descended and the other fully ascended, when the reach equilibrium depth the first time the system will still have momentum, and the ascending weight will ascend past the equlibrium point. Now suppose you had freely compressible bouys attached to each weight. As they ascend, they would become more bouyant, and, if they were bouyant at the surface, they would have some depth D at which they would be perfectly neutral. If the momentum of the system was enough to carry the weight to this depth then the other weight would contiunue to descend and the system would end in the opposite configuration from the one it started in. If the amount of surface bouyancy could be made low enough that it would be easy to leave the surface with the anchor, is it reasonable to use a setup like this to atleast make it to 10 or 20m, and sink from there?


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I have since posting realized that some of my math was wrong, which makes this setup more likely to work than not. I don't totally understand boyancy math, and could still use some serious help/advice in this regards.
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