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For what it's worth, I'm planning on using the semi-stowless bag with a Dacron-lined canopy and none of my research raised any red flags. See my thread on the topic here.

While we're at it, what's the term for the altitude below which you would go straight for the reserve rather than your main (loss of altitude awareness, emergency exit from the airplane, etc.)? The actual altitude probably depends on how long your main takes to open and the maximum altitude at which your AAD may fire. I don't remember a specific recommendation for this in the SIM. What's your personal threshold?

"predetermined altitude" in Section 5: 4: You should decide upon and take the appropriate actions by a predetermined altitude: a. Students and A-license holders: 2,500 feet. b. B-D license holders: 1,800 feet.

That doesn't have all the slides. The rest is posted here: http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=3131726#3131726

Finally some numbers!

So when you do a pull test on the ground the pilot chute is accelerated to 120 mph by the spring?

Could we all agree on a common definition of "drag," preferably one that is used in physics? The one from Wikipedia seems like a good starting point: "forces acting opposite to the relative motion of any object moving with respect to a surrounding fluid." Is the pilot chute moving with respect to the air? Then it is experiencing drag. But without tension from the bridle, the speed is quickly reduced from 120 mph to almost zero. The time this takes is a function of the force and mass, with the added caveat that the drag force is continuously decreasing together with the speed. The same is true for the stick on the water. The stick is initially moving with respect to the water and drag is what "decelerates" it to match the flow velocity. In order to have drag, you must have a relative velocity through the surrounding fluid, nothing else (assuming non-zero density, cross section area, and drag coefficient).

You can find this out yourself with a couple of SensorTags for a cost of two jumps. I'm not sure how you would go about packing a parachute with those on the inside, or how to attach them without damaging the fabric. Maybe we could get some CRW guys to throw these sensors into an inflated canopy

Thanks, John! I actually watched your PIA presentation on this very topic. As an aside, I would say that you can approximate air as an incompressible fluid at the airspeeds that we're talking about, which is why I've never had to calculate the equivalent airspeed in a Cessna. However, it is not correct to say that air is an incompressible fluid, which implies that this holds true for all airspeeds and conditions. The main thing that was of interest to me is your assertion that pressure inside of a canopy is ambient. What I wanted to ask you was whether this claim was ever measured with pressure sensors located inside the canopy? Before we get to canopies, what is the pressure inside of a pitot tube on an airplane? The pitot tube measures static + dynamic pressure, or stagnation pressure as it is commonly called: https://en.wikipedia.org/wiki/Stagnation_point https://en.wikipedia.org/wiki/Pitot_tube There is no airflow through the pitot tube (not counting the drain hole, which isn't required), yet the pressure inside is certainly not ambient. You need the static port to subtract the ambient pressure in order for the airspeed indicator to show dynamic pressure. How is this situation different from a canopy? You've got a stagnation point at the nose and it is that pressure that I would expect to find inside all of the cells, just like in a pitot tube. The lower pressure outside of the cells due to Bernoulli plays a role in keeping the canopy inflated, but I'm not convinced that it's the whole story. Do you have any data that shows otherwise?

Negative, Ghost Rider! But your questioning did get me to try to get a definitive answer. Check out NACA (predecessor to NASA) Report 420 from 1933 on airspeed measurement. It's out on the web. Relevant excerpts are in the attachment. It notes that an anemometer will read true airspeed and not indicated airspeed, which is why it is not particularly suitable for aircraft speed measurement. (This is for normal style anemometers which attempt to have a bearing of negligible friction. If it were a wind turbine with torque resistance, then it would act more like a set of airfoils and vary measured speed with air density -- showing IAS.) This is a subtle thing about anemometer airspeed measurement which isn't obvious at first glance! Interesting... I'm not one to argue with NACA, but this paper seems to disagree: http://www.mdpi.com/1996-1073/5/3/683/pdf Intuitively, what would you expect to happen if you placed a vane anemometer into a full or partial vacuum and moved it in a circle at 10 mph? In a full vacuum, it should read zero. There is nothing to move the propeller. In a partial vacuum, it should read something above zero, but not the full 10 mph because the pressure acting on the propeller is less than it would be in the standard atmosphere. I guess we'll find out when I do the measurements. I might try it this weekend if it doesn't get too cold or windy for a high-pull.

Cool! I guess my next project should be to build a full face helmet with an array of sensors and a projected HUD inside the visor. I guess Google Glass would work as well No, I expect to get the same raw readings at any altitude (the only caveat is that the meter may be doing some correction for the temperature, I'll have to look into that). It's dynamic pressure that is causing the propeller to spin, which is the same thing measured by the pitot-static system on an airplane. At high altitude, the air molecules will be moving faster through the probe (TAS), but there will be fewer of them because of lower density, so the propeller will spin at the same RPM, giving the same airspeed reading. Good to know, thanks!

I got my hands on a vane anemometer (General DAF4207SD) that I'd like to use under the canopy to measure airspeed in various configurations. The fastest sampling rate is 1 second, which might be a bit low for recording the dynamic events, but perfectly sufficient for steady flight. If anyone here has some first-hand experience with doing this type of data collection, I'd welcome any tips, especially on the best place and method for mounting it. I'm primarily interested in figuring out the true airspeed for full glide, different brake and rear riser positions, and possibly front riser input. The anemometer gives me indicated airspeed and temperature, which can be converted to true airspeed along the glide path as long as I have the local pressure setting from the AWOS. I also have an AltiTrack that records my rate of descent, so I could even account for that to get the true horizontal speed. Unfortunately, I don't have the docking station for it, but I'll ask around my DZ to see if someone else may have one. From what I understand, the JumpTrack software only supports XP. Does anyone know of any alternatives? Thoughts? Suggestions?

http://www.vigil.aero/wp-content/uploads/Introduction-email-Vigil-2+-001.jpg

I sent this question to Sandy Grillet and he forwarded it to a couple of people at UPT. According to the UPT tour rep (Greg Rau?), the semi-stowless bag and Dacron lines combination should work fine. Scott Roberts, the designer of the bag, said that "the bigger bulk makes it a bit harder to pack, but there is not a friction issue in my experience." Based on that, I'm going with the semi-stowless bag for my rig. Expecting it to arrive in January, so that's when I'll know for sure whether I made the right decision

What main and reserve are you using with the V353? Were you getting hard openings initially? How did you know that the lines are coming out in clumps?

I received one reply by PM. Reposting it here for anyone else who may be interested in this: Still looking for more feedback.

Sorry for bringing up an old thread, but I'd like to know if anything has changed as far as slider grommets melting SLinks is concerned? I'm planning on getting a Spectre 230 with Dacron lines, PD SLinks (probably reserve), and Type 8 risers. This thread is the first one I've seen that indicates a potential problem with this combination.

How are you going to arrange that? Browse a bit dz.com and you'll see images and videos of pilotchute in tow on those this-small-camera-mount-will-break-before-anything-bad-can-happen setups. - Petri Are there any photos or videos of a pilot chute in tow being fixed by a helmet cutaway? The ones that I've seen were all solved by manually untangling the bridle. Genuinely curious, because my understanding was that the cutaway is for the case where you've got a main line wrapped around the camera. Would the pilot chute actually generate enough force to pull the helmet off, especially if your head is not in line with the airflow?

Isn't that a bad thing? I'm still more than 100 jumps away from bringing a camera along, but when I do, I would rather have the camera break off when a force above a certain threshold is applied to the mount. That seems like a safer alternative than a cutaway for the whole helmet, especially for someone like me who wears glasses with a fairly strong prescription. I have the Rev2 and absolutely love it, but I got rid of the cutaway handle and just routed the yellow cable under the pads where it can't get snagged on anything. I'll have to figure out some other solution when its time to put a camera on it.

Does anyone have experience with this combination? I'm planning on getting the Vector 3 V358 for a Spectre 230, which is the largest size that is available with a semi-stowless d-bag. My concern is whether the extra bulk and higher friction of Dacron lines may present a problem for packing, deployment, or line wear. I will send this question to UPT as well, but I'd like to know if anyone here has some first-hand experience to share.

Optimum has higher maximum weight limits for all sizes. I'm about to order the 235, having also looked at Nano and Smart reserves. Not that I would expect any of these to fail, but it's nice to know that the your reserve is rated for an extra 40 lbs instead of 10.

You can figure out just how much slack there was in the pin tape by aligning the tip of the pin with the hole, where it would have been to initiate the puncture. From the 3rd and 4th attachments, you can estimate that the bridle was able to travel ~1cm before the pin tape was under tension. It is very easy to introduce this slack if you tuck the top part of the bridle before the bottom part. I always tuck the bottom first, making sure that the pin tape is under tension. This makes it impossible for the bridle laying on top of the pin to move while the pin remains stationary. Even so, I think switching to bottom routing is probably a better idea and will do that from now on.

That's what I plan on getting. There is a photo of the magnetic covers on the last page of: http://www.flyaerodyne.com/download/AERODYNE_NEWSLETTER02_nxgn.pdf I think the Vector magnetic riser covers are a bit better because the inner flap is in the shape of a trapezoid, so it's not just the magnets that are holding the flap in place. I think the early design used rectangular tabs that sometimes opened during FF.

I might try that the next time I fly the Pilot, but the demo has been sent back already and I'm pretty much set on the Spectre. Are there any good reasons against it? The only one that I can think of is that it consistently took 1,000 ft to open. I would be happier if the snivel was just a tiny bit shorter, perhaps as on the Strom. Don't like Storm's steeper glide though

If you already have a container, then sure. However, renting for 30+ weeks @ $100/day or $30/jump is a bit expensive. If I could find a used or stock Vector of the right size, I would probably get it. Also, just to nitpick, being the first to come up with an idea doesn't necessarily mean that your implementation of that idea will be perfect. I imagine that most manufacturers look at UPT designs and try to develop their own small improvements. Aerodyne's miniforce rings are just one example, although in my case I'm going with standard rings and risers.