Another dive to 45m for 50 minutes, on the other hand, would require the use of 2 x 18-litre twin tanks and an Alu80 (11 litres) with 50% nitrox for accelerated decompression. Decompression will also result in an ascent time of 59 minutes and 119 minutes of total dive time. This dive is outlined on the graph on the right (below), but with a different display.
Gue Deco Planner Software
These oversimplified examples are just scraping the surface of what this software is capable of doing, as we have not even made a mention of trimix or open circuit, which is where its strengths come to the fore. There is also a long list of options for setting parameters and preferences, which can be seen on the right side of the screenshot above.
V-Planner is a decompression program that uses the Varying Permeability Model (VPM-B) for decompression profiles. The VPM-B decompression model is well suited to today's technical diving. The deco profiles will start deeper than traditional models and account for micro bubble growth and keep overall supersaturation lower, and giving a better overall decompression.iPhoneAndroidiPadDive computersMultiDeco-TDC is installed in the Technical Dive Computers TDC-3 model.The dive computer's firmware is aligned perfectly with the MultiDeco planning software. This continuity across the dive platforms, gives a consistent result between the surface planning and the actual dive. Plan your dive, and dive your plan.Windows / Mac / LinuxThe VPM model is the most widely used bubble model by tech divers today.
V-Planner makes plans for Lost deco gas, Turn pressures, Range plans, RB bail outs, watches and warnings. Includes Gas Mixer, Turn pressure formula, Layouts for saving complex dive plans, Graphs, data export, etc.
The Bubble models and similar deep stop profiles, have become the standard fortechnical and deep diving, with many training agencies including bubblemodels into their courses. The VPM bubble model uses math to simulate andmeasure micro bubble growth, and set limits accordingly. The output of abubble model is similar to many established deep practices suchas Pyle Stops, Florida cave practices, DIR, ratio deco plans and others.
The Varying Permeability Model was originally developed by Yount and Hoffman in 1986. It was further developed by David Yount, Eric Maiken, and Erik Baker from 1999 to 2001. In 2002, after considerable diver feed back, the model was further developed by Erik Baker, to the current VPM-B model. The V-Planner program was developed by Ross Hemingway, and presents the VPM-B algorithm inside a complete and useful Windows dive decompression program. See also... VaryingPermeability Model (VPM) References
MultiDeco is a decompression program that uses the Varying Permeability Model (VPM-B) and the Bühlmann (ZHL-16) for decompression profiles. The VPM-B decompression model is well suited to today's technical diving. The deco profiles will start deeper than traditional models and account for micro bubble growth and keep overall supersaturation lower, and giving a better overall decompression.iPhoneAndroidiPadDive computersMultiDeco-TDC is installed in the Technical Dive Computers TDC-3 model.The dive computer's firmware is aligned perfectly with the MultiDeco planning software. This continuity across the dive platforms, gives a consistent result between the surface planning and the actual dive. Plan your dive, and dive your plan.Windows / Mac / LinuxMultiDeco calculates all types of Nitrox, Trimix, TriOx, HeliOx, OC, SCR, CCR, RB80, KISS and multilevel dives.
MultiDeco makes plans for Lost deco gas, Turn pressures, Range plans, RB bail outs, watches and warnings. Includes Gas Mixer, Turn pressure formula, Layouts for saving complex dive plans, Graphs, data export, etc.
The ZHL-C model comes from the work of Dr. Albert Bühlmann and his research into decompression. His ZHL-C model was published in 1984. In the mid 1990's, Erik Baker devised a formal method to lower the supersaturation exposures of ZHL-C and thereby append both deeper stops and/or longer deco times onto ZHL-C. This is called Gradient Factors (GF) and is the ZHL-C + GF combination is use today. The available GF settings are wide ranging in their effects and are able to emulate other decompression model attributes.
The Varying Permeability Model was originally developed by Yount and Hoffman in 1986. It was further developed by David Yount, Eric Maiken, and Erik Baker from 1999 to 2001. In 2002, after considerable diver feed back, the model was further developed by Erik Baker, to the current VPM-B model. The MultiDeco program was developed by Ross Hemingway, and presents the VPM-B algorithm inside a complete and useful Windows dive decompression program. See also... VaryingPermeability Model (VPM) References
To many, that sounds too good to be true. Almost all decompression software, dive computers and tables in current use are based on Buhlmann or VPM-B decompression models or some varient thereof. These models have received theoretical and real-life testing, include calculation for sixteen different theoretical tissues, and permit unlimited combinations of dive depths, durations, breathing gasses. Surely this cannot be replaced by a new decompression model calculated on-the-fly by the diver.
In reality, ratio deco is not a decompression model. Rather it is a series of approximate relationships and trends that can be observed from ascent schedules calculated using existing models. Searching the internet suggests GUE Ratio Deco is derived from either VPM-B with +2 conservatism, or Buhlmann with approximately 30/85 gradient factors. Either way, it is attempting to replicate a bubble model profile, so comparing it to VPM-B +2 is justifiable.
Whether bubble models generally, or VPM-B specificaly, are the best choice of decompression model is another topic or much debate. But if we think of ratio deco as an approximation of VPM-B used within set limits, the concept is not so radical.
GUE and related organizations have adopted standard gas mixes, selected according to dive depth, and have standard ascent and descent rates. With these known, for a set depth and over a limited range in duration, it should be possible to find a linear approximation of the relationship between bottom time and decompression time.
Figures 3 and 4 compare the bottom time to the deco time for VPM-B +2 dives to 45m and 51m, respectively, using 21/35 or 18/45 trimix bottom gas and 50% nitrox decompression gas. As described above, deco time is taken as the time from the first stop until leaving the 6m stop. It does not include the time to ascend from the bottom to the first stop, or the 6 minutes to ascend at 1m/min from the 6m stop to the surface. For comparison, the 1:1 ratio line is plotted on the 45m plot, and the 1:1 ratio plus 10 minutes (5 minutes per 3m increments beyond 45m) line is plotted on the 51m plot. So to is a line at 1:1 (or 1:1 + 10 minutes) ratio plus 6 minutes, representing the surfacing time, which is when the ceiling must have cleared so as not to be broken.
Figure 3 shows that for a 45m dive, the 1:1 bottom time to deco time ratio provides a good approximation when using 21/35 trimix bottom gas, up to about 35 minute bottom time. Beyond this the decompression time increases, diverging away from the 1:1 ratio. However, the 6 minutes taken to surface from the last stop provides some buffer, so for dives using 21/35 trimix, the ratio might be used up to about 50 minute bottom time without breaking the VPM-B +2 ceiling. Compared to 21/35, 18/45 trimix includes a greater portion of inert gas, so it is not surprising that decompression time is increased when using 18/45 trimix bottom gas. But for dives with bottom time up to 30 minutes, the 6 minutes surfacing time provides enough of a buffer that the VPM-B +2 ceiling might not be broken.
Figure 4 shows that for a 51m dive, the 1:1 + 10 minutes bottom time to deco time ratio is a poor fit. To be clear, this is beyond the specified depth range (maximum 48m) in the Team Foxturd post. It is more conservative than VPM-B for shorter bottom times and more aggressive for longer bottom times. However, up to 30 minute bottom time, the 6 minutes surfacing time provides enough of a buffer that the VPM-B +2 ceiling might not be broken when using either 21/35 or 18/45 trimix bottom gas.
Another way to compare ratio deco ascent schedule to the VPM-B model is to enter the ratio deco profile into Subsurface as a dive and see if the VPM-B +2 ceiling is broken at any point. If the ceiling is not broken, the profile is acceptable according to the model, and if the ceiling is broken the profile does not comply with the model. Where the ceiling is broken is also relevant. Some divers would excuse spending a minute or two just above a deep stop ceiling calculated with a bubble model like VPM-B (which calculate much deeper ceilings early in the ascent than a conventional Buhlmann model), so long as the time was minimal. Such a case is illustrated in Figure 5, which shows a 51m dive with 35 minute bottom time using 18/45 trimix bottom gas and 50% nitrox for decompression. Surfacing before the ceiling had cleared, such as illustrated by Figure 6 for a 45m dive with 60 minute bottom time, would be considered more risky.
Figures 7 and 8 plot the total runtime for profiles calculated using the ratio deco method outlined by Team Foxturd according to bottom time for 45m and 51m dives (noting that 51m exceeds the depth limit given), respectively. Also plotted are the runtimes when the VPM-B +2 ceiling clears, calculated by entering the ratio deco profile into Subsurface. For instances when it took longer than the total dive time for the ceiling to clear, the time to clear was determined by extending the final stop as long as necessary. 2ff7e9595c
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