SkiD_PL8 0 #26 May 25, 2005 QuoteQuoteI just visited that Wolfram website and couldn't help but laugh after reading about the nondimensionalization of the Navier-Stokes equations. So I took a few complicated words and slapped them together in a sentence. You bugger. I spent a half an hour trying to figure out what you thought you were talking about... Ok, that is incredibly funny. Way to go Jaap! Greenie in training. Share this post Link to post Share on other sites
Faber 0 #27 May 25, 2005 QuoteI doubt one would use a vented pilot chute on sub 200' freefalls. hmm you do i have freefalled 180ft whith a 46´vetnted pc serval times... i only once had a problem but that could also happen on a unvented. make a note that most vented pc´s are made bigger to still have the same surface as theyre named to... I also know of serval other guys jumping this way. I only used a 48´once(unvented) once that were a backup on a SL jump i choose not to freefall anyway... Stay safe Stefan Faber Share this post Link to post Share on other sites
pBASEtobe 0 #28 May 25, 2005 Quote Their argument was that the same amount of air would spill either though the vents or from underneath the skirt. I believe the statement is correct (drag is the same for all practical purposes) but the argumentation is flawed. ***Justs thinking off the top of my head. I haven't thought all this out but...*** Although you have to remember that the air spilling out the bottom of a non-vented PC and the same amount of air spilling out the top through a vent isn't necessarily the same. It takes energy to turn the air around 180 and spill it out the bottom whereas that energy isn't required when it goes out the top through the vent. I'm wondering if the time the air stays in the pilot chute longer (needing to turn around and spill out the bottom) or just the energy required to turn it around (opposite reaction being the topskin pushing on the air) creates more drag than a vented pilot chute. Ok I'm tired and I'm going to bed. Did any of that make sense? Share this post Link to post Share on other sites
pBASEtobe 0 #29 May 25, 2005 QuoteI doubt one would use a vented pilot chute on sub 200' freefalls. Quotei have freefalled 180ft whith a 46´vetnted pc serval times... Hmm..I stand corrected. Share this post Link to post Share on other sites Faber 0 #30 May 25, 2005 No worryes i think us in this part of the world might use smaller pc´s than you guys in the states.. I mean most arround here use the vented 42 as low as 230ft(what i have seen)on freefalls,and 46´even lower. However a 48´unvented is to preffere below 200ft but the vented can do the job aswell... but thats personal... Below 200ft you should do the chiken dance if it makes you feel better(qoute from Tom A if i rember correct).. Stay safe Stefan Faber Share this post Link to post Share on other sites wwarped 0 #31 May 25, 2005 Quote Although you have to remember that the air spilling out the bottom of a non-vented PC and the same amount of air spilling out the top through a vent isn't necessarily the same. It takes energy to turn the air around 180 and spill it out the bottom whereas that energy isn't required when it goes out the top through the vent. I'm wondering if the time the air stays in the pilot chute longer (needing to turn around and spill out the bottom) or just the energy required to turn it around (opposite reaction being the topskin pushing on the air) creates more drag than a vented pilot chute. BASE pilot chutes operate in a very turbulent environment. venting a pc correctly, this turbulence may be reduced. generally, the smoother the airflow, the easier it is to get air to actually perform usable work. i.e. the device becomes more efficient. so a vented pc might be able to generate the same forces as an unvented pc. much will depend on the design. DON'T PANIC The lies in learning how to throw yourself at the ground and miss. sloppy habits -> sloppy jumps -> injury or worse Share this post Link to post Share on other sites dmcoco84 5 #32 May 25, 2005 Yea...Good point. I could have sworn I was told that venting my 36 and 46 wasn't necessary. I tried to refer back to the email but I can't find it. I guess I'll just keep my mouth shut in the future. Share this post Link to post Share on other sites Prev 1 2 Next Page 2 of 2 0
Faber 0 #30 May 25, 2005 No worryes i think us in this part of the world might use smaller pc´s than you guys in the states.. I mean most arround here use the vented 42 as low as 230ft(what i have seen)on freefalls,and 46´even lower. However a 48´unvented is to preffere below 200ft but the vented can do the job aswell... but thats personal... Below 200ft you should do the chiken dance if it makes you feel better(qoute from Tom A if i rember correct).. Stay safe Stefan Faber Share this post Link to post Share on other sites
wwarped 0 #31 May 25, 2005 Quote Although you have to remember that the air spilling out the bottom of a non-vented PC and the same amount of air spilling out the top through a vent isn't necessarily the same. It takes energy to turn the air around 180 and spill it out the bottom whereas that energy isn't required when it goes out the top through the vent. I'm wondering if the time the air stays in the pilot chute longer (needing to turn around and spill out the bottom) or just the energy required to turn it around (opposite reaction being the topskin pushing on the air) creates more drag than a vented pilot chute. BASE pilot chutes operate in a very turbulent environment. venting a pc correctly, this turbulence may be reduced. generally, the smoother the airflow, the easier it is to get air to actually perform usable work. i.e. the device becomes more efficient. so a vented pc might be able to generate the same forces as an unvented pc. much will depend on the design. DON'T PANIC The lies in learning how to throw yourself at the ground and miss. sloppy habits -> sloppy jumps -> injury or worse Share this post Link to post Share on other sites
dmcoco84 5 #32 May 25, 2005 Yea...Good point. I could have sworn I was told that venting my 36 and 46 wasn't necessary. I tried to refer back to the email but I can't find it. I guess I'll just keep my mouth shut in the future. Share this post Link to post Share on other sites
