Rule of thirds for redundant air supply
- Thread starter Foxfish
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Diving thirds can be done with double 130's down to a single 60. Thus the reserve gas load is all over the map. Diving rockbottom or min gas normalizes the gas load in the "get home" part of the equation.
You can easily violate rockbottom if diving thirds on a 60.
You can easily violate rockbottom if diving thirds on a 60.
I am not sure that 1.5 of back gas is really functional as some has put it. I think it is all in the math. take a al 80 and 1/3 is what 27. Now take the al 80 and take away from that 1/6 for the 500# min getting on the boat and you have 77 - 13 + 64 cuft. for those who want 800 on the boat to comp for an incorrect spg than you have 77-21 or 56 cubes to use. for the 1.5 camp 50& of the 56 cubes gives the the 27 cuft pony again.
Perspnally. Ignoring all the tec aspects and what ifs, if i dive my lp95 a 30 pony is going to be more than enough given if needed you gan ascent directly to the surface. after 15 min at 80 ft getting a failed reg. Switching to the pony will get you back. Probably even if it is a 13 cuft. once you start adding on entanglements ect you are still hard pressed to need over a 30-40. the 1/3 out and 1/3 back is moot in a failure cause it will be 1/3 out and 1/10 up cause this is not a normal ascent is is an emergency or semi emergency situation. If you cant come up directly then you are either pushing your luck to begin with or overheads are involved in which the dive is no longer a rec dive. I prefer a al40 because of the way it hangs without causing trim issues. Certainly every dive will vary and some dive areas in no way fit a basic simple rec dive model and hence some things have to be modified for those instances.
On the other end of the spectrum for those who favor the need for larger pony's, there is still the issue of of entanglement and putting you beyond the NDL. For those situations you dont have an equipment failure and you have all the back gas and the pony to get back so the 1/3 or40 is still a good choice. Good overall choices and minimum needs are not the same. There are lakes I solo in that are not deep and I take a 13 pony with me. That is even overkill for me cause I use H valves and twin regs. The pony will never get opened unless the dip tube gets fouled.
Perspnally. Ignoring all the tec aspects and what ifs, if i dive my lp95 a 30 pony is going to be more than enough given if needed you gan ascent directly to the surface. after 15 min at 80 ft getting a failed reg. Switching to the pony will get you back. Probably even if it is a 13 cuft. once you start adding on entanglements ect you are still hard pressed to need over a 30-40. the 1/3 out and 1/3 back is moot in a failure cause it will be 1/3 out and 1/10 up cause this is not a normal ascent is is an emergency or semi emergency situation. If you cant come up directly then you are either pushing your luck to begin with or overheads are involved in which the dive is no longer a rec dive. I prefer a al40 because of the way it hangs without causing trim issues. Certainly every dive will vary and some dive areas in no way fit a basic simple rec dive model and hence some things have to be modified for those instances.
On the other end of the spectrum for those who favor the need for larger pony's, there is still the issue of of entanglement and putting you beyond the NDL. For those situations you dont have an equipment failure and you have all the back gas and the pony to get back so the 1/3 or40 is still a good choice. Good overall choices and minimum needs are not the same. There are lakes I solo in that are not deep and I take a 13 pony with me. That is even overkill for me cause I use H valves and twin regs. The pony will never get opened unless the dip tube gets fouled.
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