Basejumper.com - archive

Why are these crap? Why should you avoid the cap on top? Does it just make it more unstable?

Also, why aren't the vented PC's available for skydiving if they are more stable?

I'm guessing but maybe becasue at higher airspeeds instabilities of the pilot chute effect opening characteristics less than at low airspeeds?

Gus

This may be a better question to post on BLiNC, as there is a far greater level of technical sophistication there, so you'll get better discussion and more opinions.


They're not. I've used an old CR 46 ZP with a cap as low as 230' hand held, and 265' stowed. There are better alternatives, but people have used them for years.


The cap on top (or any other weight there) causes the crown of the PC to slump to the side during the inflation sequence at very low airspeeds (46" PC's are intended for delays of 0-1 second). This slumping can delay inflation (i.e. the PC can hesitate). Obviously, a PC hesitation, no matter how short, can be quite exciting under 300'. I personally switched over to an uncapped BR 48 ZP after my third sub 300' PC hesitation on a capped CR 46. My experience was that the PC hesitated noticeably around 1 time in 10, however, my PC appears to have been particularly bad, for no reason that anyone can identify.


Once the PC is inflated, the cap has minimal effect on stability (oscillation or orbiting). The weight on the apex of an inflated PC will be far outweighed by other factors (like crosswind or pitch direction).

So, if you are over 300', I wouldn't worry about it. If you are getting into ultra low (sub 200') free fall, I'd recommend investing in a capless PC.

I have seen them in use for skydiving, mostly by French skydivers.

Generally, the result of an unstable PC is an off-heading opening, and in skydiving that may not be worrisome enough to convince people to spend the extra money on a vented PC.

As an aside, the greatest equipment related cause of PC instability is asymmetric attachment, which can be addressed by PC construction, but which is not helped by topskin venting. Vented PC's definitely help if you are doing everything right, but there are several minor errors (asymmetric attachment and pitch style come to mind immediately) that will have a far greater impact on orbiting.

when packed, Capped PCs are the least aerodynamicly effiecient of all PCs.
a 8cm cap would be geting dragged throught the air at speeds up to 300 km/hr. they fall out sometimes BASE jumping on long dleay jumps, and we even pack our PCs really well.


(how many words did i misspell there?)