Jonsmann 0 #1 May 30, 2009 Can anyone tell me any significant reason not to have vent holes in a ZP canopy? Like for example 1 sq inch holes at the trailing edge of the 3 center cells? It sure would make packing easier. I see absolutely no reason why such holes shouldn't be there! Inflation pressure is virtually the same as without the holes, and the holes cannot cause flow separation at the top skin as for F111 canopies. Am I missing something? Jacques Quote Share this post Link to post Share on other sites
DrewEckhardt 0 #2 May 31, 2009 Just wait until you get 500-1000 jumps on the canopy. The stitching holes will open up so it's easier to get the air out and the surface coating will wear down so the fabric stays put almost like F111. Quote Share this post Link to post Share on other sites
captain_stan 0 #3 May 31, 2009 Quote Am I missing something? Yeah. Quote the holes cannot cause flow separation Any air that leaks out through any part of the cells must be replaced by more air coming in the nose vents. As more air than "normal" must enter the vents, that leaves less air to flow over the top and bottom skin to create lift. You are free to experiment with your canopy by cutting holes in it. Can I watch? If it's a big enough canopy, then maybe you can still land it alright. You or the manufacturer could develop some valves that you could open during packing and close for flight, but the market of people who DON'T KNOW HOW TO PACK ZP is very small so there is not much demand. I reccommend learning how to pack or buying an F-111 canopy. Quote Share this post Link to post Share on other sites
airtwardo 6 #4 May 31, 2009 Quote Can anyone tell me any significant reason not to have vent holes in a ZP canopy? It would let all the magic escape! ~ If you choke a Smurf, what color does it turn? ~ Quote Share this post Link to post Share on other sites
RiggerLee 61 #5 May 31, 2009 When **** ****** now a well known rigger from Texas got his first saber he was so frustraed trying to pack the slippery greasey thing that he resorted to trying to perferate the tail of the canopy by sewing back and forth just in front of the tail seam with his sewing machine and a dry neadle. We still make fun of him for it. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites
phoenixlpr 0 #6 May 31, 2009 QuoteCan anyone tell me any significant reason not to have vent holes in a ZP canopy? Like for example 1 sq inch holes at the trailing edge of the 3 center cells? It sure would make packing easier. Your canopy is flying as long cells are pressurized. So your newly modified canopy would easier collapse in turbulence. Is this you really want? If I were you I'd rather learn how to pack. Quote Share this post Link to post Share on other sites
captain_stan 0 #7 May 31, 2009 QuoteI see absolutely no reason why such holes shouldn't be there!Oh yeah, one other thing: The engineers who designed your canopy didn't intend for air to be leaking out while you are snivelling at line-stretch waiting for it to inflate. Any such alteration may change the opening characteristics. Let us know how that works out. Quote Share this post Link to post Share on other sites
JohnRich 4 #8 May 31, 2009 QuoteCan anyone tell me any significant reason not to have vent holes in a ZP canopy? Like for example 1 sq inch holes at the trailing edge of the 3 center cells? It sure would make packing easier. Ease of packing is what it's all about, so by all means, try your design change and see what happens. Some people here even encourage others to experiment with such things, because unless you make mistakes, you don't learn anything. So educate yourself. Punch those holes, and report back with the results. You may just be on to the greatest design improvement since the 3-ring system. Quote Share this post Link to post Share on other sites
Jonsmann 0 #9 May 31, 2009 Hi Lee So what happened? Did it fly terrible afterwards? If it did I suppose I got my answer except no explanation. If it did work I don't see any reason to make fun of him. If it didn't make the canopy pack easier and there was no adverse effects, I suppose he didn't make enough holes to find out! Jacques Quote Share this post Link to post Share on other sites
PeteS 0 #10 May 31, 2009 Zippers my friend, zippers... Quote Share this post Link to post Share on other sites
popsjumper 2 #11 May 31, 2009 Quote Quote Can anyone tell me any significant reason not to have vent holes in a ZP canopy? It would let all the magic escape! Yeah, but wouldn't it get more forward drive? L's, T's, what?My reality and yours are quite different. I think we're all Bozos on this bus. Falcon5232, SCS8170, SCSA353, POPS9398, DS239 Quote Share this post Link to post Share on other sites
airtwardo 6 #12 May 31, 2009 Quote Quote Quote Can anyone tell me any significant reason not to have vent holes in a ZP canopy? It would let all the magic escape! Yeah, but wouldn't it get more forward drive? L's, T's, what? Pffft...Doghouse youngster DOGHOUSE. ~ If you choke a Smurf, what color does it turn? ~ Quote Share this post Link to post Share on other sites
VectorBoy 0 #13 June 1, 2009 Do CRW with it. In no time you will have all kinds of small perferations in it. Quote Share this post Link to post Share on other sites
GLIDEANGLE 1 #14 June 1, 2009 One way to get air out of a ZP canopy: 1. Lay it out on it's side as if you were going to side pack it. 2. Most air should come out easily. Any remaining you can put to the nose. 3. PRO pack it on the floor. (Do NOT put it over your shoulder). Detailed instructions for this process can be found in the FAA Parachute Rigger Handbook pp: 5-33 through 5-38. This description is in the context of packing a reserve, but you can readily see that you can adapt this to pro-pack a main on the floor. This handbook can be found for free at: http://www.faa.gov/library/manuals/aircraft/media/FAA-H-8083-17.pdfThe choices we make have consequences, for us & for others! Quote Share this post Link to post Share on other sites
funfall 0 #15 June 1, 2009 QuoteOne way to get air out of a ZP canopy: 1. Lay it out on it's side as if you were going to side pack it. 2. Most air should come out easily. Any remaining you can put to the nose. 3. PRO pack it on the floor. (Do NOT put it over your shoulder). Detailed instructions for this process can be found in the FAA ....... Interesting, but does this actually save time? If not, what's the advantage? And would it take more floor space? Thanks. Quote Share this post Link to post Share on other sites
councilman24 36 #16 June 1, 2009 No it doesn't save time. Just an answer to the guy whining about packing his main. I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites
popsjumper 2 #17 June 1, 2009 QuotePffft...Doghouse youngster DOGHOUSE. Bang! Ya' got me Marshall Dillon...ya' got me. XX(My reality and yours are quite different. I think we're all Bozos on this bus. Falcon5232, SCS8170, SCSA353, POPS9398, DS239 Quote Share this post Link to post Share on other sites
erdnarob 1 #18 June 2, 2009 It seems for me that you want to solve a problem by creating a new one. Everybody get mad at the very begining when packing a brand new ZP canopy. Ask an instructor or a rigger to give you some packing lessons. This past winter I gave a packing course requiring 10 packings under my supervision. I can tell you that after the course, all of my students were able to pack a ZP canopy. My approach is the following: when the roll or sausage is made on the floor, stay laying on your canopy and fold it in three parts when still laid on it. It is possible by backing up just the length of one fold at a time. That way it is easier to control the volume since your chest apply a constant pressure of the folded canopy. That method was shown to me at Rantoul by a guy from Boston. Since I use that method, I am not anymore frutrated.Learn from others mistakes, you will never live long enough to make them all. Quote Share this post Link to post Share on other sites
Jonsmann 0 #19 June 2, 2009 Just to save the time of all those people who don't seem to actually read what I ask. I do know how to pack, quite well if I may say so. The thing is that I'm an engineer and I just hate when something is done just out of convention rather than because there is a good reason for it. Oh and for those who just think it is a stupid question, please understand that I do know aerodynamics and I still don't see a reason why such vent holes shouldn't be there. Quote Share this post Link to post Share on other sites
captain_stan 0 #20 June 2, 2009 QuoteI do know how to pack, quite well if I may say so.What I'm getting from this thread is that most of the rest of us who also know how to pack don't seem to dread it enough to be willing to accept any trade-off involved in trying to make it easier. So if you're gonna cut holes, it will only be a marketable idea if (1) no performance is lost (2) it's cost effective (3) It doesn't create more work. I saw a guy use a vacuum cleaner to suck the air out of a ZP canopy. It seemed like a birlliant idea to me, but not worth the effort in dragging the vacuum cleaner around the DZ. QuoteThe thing is that I'm an engineer and I just hate when something is done just out of conventionWhen I think about the ram-air canopy, the slider, ZP fabric, micro lines, eliptical canopies, cross-braced canopies, RDS, slinks, etc., I can't agree that the parachute industry is limited by convention. PD responded to that issue by developing the Silhouette. QuoteI do know aerodynamics and I still don't see a reason why such vent holes shouldn't be there.Then it's time to put your hot-knife where your mouth is. If you want to be the next Jalbert, you're gonna have to get your hands dirty. As skeptical as we might seem, I think your audience will be facinated to know the results; I know I will be. Quote Share this post Link to post Share on other sites
JohnRich 4 #21 June 2, 2009 QuoteSo if you're gonna cut holes, it will only be a marketable idea if (1) no performance is lost (2) it's cost effective (3) It doesn't create more work. Add: "(4) It's safe." Actually, that should be #1. In the sky, with air escaping out the rear vent holes, it seems that this will reduce the air pressure inside the cells. And with that, the canopy might be more likely to collapse in turbulence. I'll let Jonsmann try it first. I'll watch. Quote Share this post Link to post Share on other sites
captain_stan 0 #22 June 2, 2009 QuoteAdd: "(4) It's safe." Actually, that should be #1. It is #1. Safety is a component of performance. If it opens consistently well, flies well in turbulence, responds well to control input, lands softly, etc., we'd say it performs well. OTOH, if it isn't safe to fly, we'd say that's not very good performance. Quote Share this post Link to post Share on other sites
Jonsmann 0 #23 June 2, 2009 Quote Then it's time to put your hot-knife where your mouth is. I like that! Point taken! I suppose I was hoping there was someone out there who could provide me a satisfactory answer so I can put my mind to rest. Quote Share this post Link to post Share on other sites
JerryBaumchen 1,046 #24 June 2, 2009 Hi Jonsmann, I'm an engineer also. And a very curious one! I say go for it. But remember that you're experimenting and if the results are very bad you may just lose the value of the canopy. Ted Strong once said that we know very little about these canopies. In his opinion, the control system was really nothing more than wing-warping; which is how the Wright Bros controlled their first aircraft. I know of no current aircraft design that uses wing-warping. We have a long way to go. If you do cut the holes, please keep everyone posted. In fact, some packing/test jump comments by you & others would make a fantastic article. Best of luck, JerryBaumchen Quote Share this post Link to post Share on other sites
billeisele 122 #25 June 2, 2009 Jerry - weren't the first cross ports thought to be "crazy"? If my memory is correct: my standard Cloud worked great without them (so what if you had to hold brakes to inflate the end cells) but then the Cruiselite had them so we used a coffee can for a template and hot knifed some holes, only one time we screwed up and put one in the top skin Give one city to the thugs so they can all live together. I vote for Chicago where they have strict gun laws. Quote Share this post Link to post Share on other sites
