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Hey there,

i was searching for informations considering the force (the power they develope/drag) of different seized PC.
Are there any scales/diagramms for different PCs that show speed vs drag?

my questions are:
1) how much is the influence of the PC during canopy ride? (inhibit distance of an object,)
2) the use on SL jumps as a safeguard: I know the PC safed lifes. but how reliable is the PC (which value has it) far below terminal velocity?


thanx for your help

Most estimates that you hear are based on crude theoretical calculations, not considering details in design and other real effects.

Here's a thread on the subject from some time ago:

http://www.basejumper.com/...tring=pc%20;#2878179

I did some windtunneltests of several different pcs and measured dragforces at different velocities (~10, ~17,5 & ~25m/s). Results were posted.

the pc will certainly effect canopy performance, however this effect is essentially a nonfactor on base canopies. clearly on a pd velocity loaded at 2.2+ that can hit a horizontal speed of 60mph+ towing a large pumpkin of a pc is going to matter. on canopies under 1.2 i don't see it making a difference. typically pc size is determined by object height (typically but not always) and as such the bigger pc's are used on lower altitude jumps with shorter canopy times. so even if a 48" has drastic effect on canopy performance when this pc size is used it isn't a factor for very long. in other words when a very large pc is required the exposure of flying a fully inflated canopy with this pc is very short. i've never experienced performance issues when using very large pc and that has even been on jumps that were 'low' at the exit but very high under canopy. i'm sure manufacturers design canopies so that there are no serious adverse effects from towing a 32" pc all the way up to 48".