Re: [becs8399] PC Drag Table
> I'm having a little trouble understanding the organization of the spreadsheet, though.
What do you mean? Each row contains all the parameters AT a certain delay, each column contains the information as per column heading: time, distance fallen, speed, acceleration, air pressure, drag force in N for a 48" PC, drag force in kg for a 48" PC, and so on.
> Is there an easier way to look at it. or is there just that much info?
I don't know about an "easier" way to look at it. Just read carefully the text above the table because there it is explained everything you need to know to read the table and to adapt the table to yourself (=to your exit weight and to your terminal velocity). Just follow the tips.
Remember to change in cell C24 the "dimishing factor" from 1 to "something" else (=higher value). Leaving 1 gives you really theoretical values, just as if the PC were inifinitely rigid (=steel disk), perfect manufacture, no burble effects on the border of PC, whatever. These are issues that does NOT exist in real life.
To take into account EASILY of these effects altogether, just put in C24 a value higher than 1. In MY personal table I put 1.5: it seems quite reasonable to match "reality".
In fact, if you put 1.5 as "dimishing factor", after 1 s of freefall under a 48" PC the table says it pulls with 4.6 kg, that seems really reasonable. In fact, in reality, when using a 48" PC a throwing it after 1 s of freefall, it indeed opens the container and starts to extract the parachute (mine weighing about 4.2 kg): this is the reason that make me think 1.5 is quite an acceptable value. The above situation gives at 2 s a pull force of 17 kg. Really, really reasonable, provided that any force between 4.6 kg and 17 kg is capable (and responsible) to open container, to extract a 4.2 kg parachute and get it open at the 3rd s after exit. This matches perfectly with our experience. That's my justification that 1.5 as "dimishing factor" is a good and sound value.
And, lastly, don't forget it is just a table: it gives you a good approximation of reality. In fact, the pulling force after 3 s of freefall of a NOT inflated PC is ZERO, not matter what the table says...
