evh

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Posts posted by evh

  1. On 2/9/2021 at 1:47 PM, Kenzdik96 said:

    ... things like front and rear riser flight, as well as harness input are almost impossible to learn on such canopies at such wingloadings as the forces required to use the risers are insanely high, and harness response is non-existent....

    Really? I have no problem harness turning a nav 240, rear riser pressure is even lighter than my crossfire. 

    Front risers? Yeah there I agree, forget about those. But there's no need for those at 45 jumps. At those numbers you better work on survival skills like flat turns and avoiding traffic with your rears.

     

     

     

  2. If you really want to fix hard openings, the solution that makes the most sense to me is to control the slider speed.

    I'm convinced that a really hard opening is impossible if the slider goes down at a slow, controlled speed. If you can find a way to make it go down in a very controlled way, lets say constant speed in 3 seconds, I think you may have fixed the problem. 

    In the current design, the slider is kept at the top end of the lines by air resistence, while it wants to come down due to the canopy wanting to spread out. Friction between the grommets and the lines also helps to keep the slider up, and once it starts moving, slows it down a bit.

    This is a very delicate balance, especially since friction is super unpredictable and changes depending on linetype, wear, dirt, and probably temperature, humidity etc. Once the balance dictates that the slider goes down, this happens at an almost uncontrolled speed since the friction is nearly independent on the speed of the gommets over the line So what happens, once the slider starts moving it moves without much control of its speed. Designers can offcourse affect the velocity at which the slider starts moving; controlling the speed is almost impossible. 

    So what we need, is a reliable  way to dampen the slider speed. Dry friction is not the perfect solution (altough very simple and cheap) because it is almost independent of speed; what we need is that the amount of friction depends on the velocity at which the slider moves over the lines. No friction at 0 speed, a lot of friction at high speed. This way you could make sure that the slider ALWAYS takes around 3 seconds to come down, at a constant speed. Problem solved! In theory at least... 

     

     

     

  3. · Edited by evh

    I think it happens a lot, I've known a lot of guys who were very active and made a lot of jumps in a short time, only to suddenly disappear and never be seen again at a dropzone. Others keep on going year after year.

    Me, I quickly stopped doing tandemvideo when someday I felt relieved that jumping was cancelled for the day due to the weather. It started to feel like a job, and I already have one of those! Went back to jumping just for the fun of it, and never regretted it. Maybe someday I'll change my mind again, maybe not. 

    • Like 2

  4. · Edited by evh

    On 6/6/2020 at 4:43 PM, kallend said:

    It takes 3 times before some people comprehend what they read.  Any teacher will tell you that.

    So maybe you should read Baksteen's posts two more times then ;-)

    He has a valid point.

     

    Roughly measured in Google Maps, border to border Sweden - Iceland : 1300 km

    Countries within that radius include:

    - Belgium

    - UK

    - Italy

     

  5. · Edited by evh

    43 minutes ago, sundevil777 said:

     I am quite  skeptical that a few inches would be enough to matter much.

     

    I agree. I tried doing the math, and fail to see how this solution would work. It sounds nice, as a concept, but there is no way I can make it work on paper. On a climbing harness this solution makes sense; a rope stretches maybe half a meter, adding 20 cm to that helps. But unlike a climbing rope that is anchored into a mountain, a canopy moves with the skydiver and simply excerts a force through the lines, which mainly depends on air speed. Unlike a climbing rope, the force is independent on distance travelled; it just depends on the speed.

    A canopy opening at  7G has a "braking distance"  of about 26 meters (thats ~86 ft, ouch!) , adding a few inches to that is insignificant. Or is this too much of a simplification? If so, how should you calculate this?

     

     

     

  6. Who says coal is dead? It isn't and it won't be as long as a few rich russians are making a lot of money (while other russians are dying beacuse of it, but who cares, right, MAGA fuck yeah!)

    And if you don't like the black snow, you can aways paint it white....  brilliant solution!!

    https://www.themoscowtimes.com/2018/12/19/russian-authorities-cover-snow-white-paint-hide-sings-pollution-a63892

    https://www.businessinsider.nl/snow-turns-back-siberia-russia-pollution-2019-2/

     

  8. 6 hours ago, skybytch said:

    Don't let anyone tell you that your landing issues are because you are female.  That's total bullshit.  Your landing issues are because no one has taught you how to time when to flare and how to flare correctly.  My best advice regarding improving your landings is to take a canopy control course ASAP.  

     This.

    14 hours ago, Crescentia said:

    Like a lot of other beginner-women I have problems to see, when it is the right moment to flare (I learned 2-stage-flare: half and than full) - especially in no wind conditution.

    We ALL have had that problem. Boys are just better at acting like it didn't hurt  ;-)

     

    • Like 4

  13. 14 hours ago, sundevil777 said:

    Why is a carbon fiber shell critical to you?

    Probably because carbonfibre is ridiculusly strong for its weight. So for the same strenght you get a lighter helmet, or for the same weight you can get a much stronger helmet.

    I'm not entirely sure that this translates to better protection tough, since strength is just one of the many material parameters that affect impact resistance.

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  15. "However, if you reversed the set-up and had the quick ejector strap attached to the plane, and attached it to somewhere on the harness, say the articulated hip ring, that might be more efficient"

    If by "quick ejector" you mean a large version of an RSL snap, than that's exactly what I see in a lot of planes in Europe (mostly C208's). And it works very well, without the need to modify a harness. I don't know the legal implications, but apparently it's not a problem here.  Getting such seatbelts in our C182 on the other hand appears to be a big problem to the authorities, unfortunately.

     

    • Like 1

  17. Thanks OP for reaching out and asking this great question!

    You already got a lot of good advice, but I have one more thing to add. So far most advise focussus on the low altitude part, where we are flying under our parachutes, but I have also seen gliders above 3000 ft, where we are still in freefall.

    From the altitude we jump at, it is very hard to spot a low flying glider. It is impossible to see if they are flying at 3000 ft or at 100 ft. And once we are in freefall, it only gets worse. Besides that, a glider can cover a lot of distance in the roughly 60 seconds that we are falling, so even if we saw it but it seemed at a safe distance when we jumped, this can change quickly.

    You should expect people free falling at 3000 ft a lot, sometimes a bit lower and in some rare cases even as low as 1000 ft (in case of some emergencies). During this time we can not avoid traffic. So make sure you know where the skydivers are falling and make sure the skydivers know where you are flying. Not just the pattern, but also the area where you go looking for thermals (if that is close to the airport).  And remember, our exit point changes through the day if the wind changes.

    That being said, as long as everyone involved makes an effort to understand and avoid each other , this can certainly be done in a safe way. As always, comminucation is key.

     

     

  18. On 4/1/2020 at 5:14 PM, wolfriverjoe said:

    Not the best thing in the world for nylon, but it's an option.
     

    That is perhaps a but understated. UV is very bad for nylon.

    It would not be surprised if it ruined your gear in no-time.

     

  19. 1 hour ago, Baksteen said:

     

    . I've been using the even more cheapo foam plugs since then - and they also work just fine even though I did not take them into freefall yet.

    I use the super cheap ones as well, mainly because I KNOW I will loose those expensive ones within a day :-)

    Works perfectly for me, but then again it seems that some people's ears are more sensitive for pressure changes than mine.

    The only real downside for me  is that they make it a bit harder to communicate before boarding. The custom made earplugs are probably better in that respect.

    • Like 1

  23. · Edited by evh

    At my dropzone we use the direct-bag system. The staticline has a flex pin connected to it, which goes through the closing loop to lock the container. A flex pin is basically a piece of steel cable, covered in a layer of plastic (so basically a steel wire inside of a plastic hose). 

    A few years ago (I think in Poland?)  there were some incidents with tandem gear, where the plastic coating around a flex pin failed. The plastic was partially stripped from the steel, and the whole mess was blocked inside the closing loop, obviously keeping the container closed. This did not end well.

    So it seems quite possible to me that a failed flexpin could cause a student in tow, altough I do not know of any cases where this actaully happened. Maybe the closingloop would break in this scenario? I'm not sure. 

    This potential problem is why we check the flexpin for damage  during a gear check, just before boarding.

  24. A black dot on your goggles or visor works perfectly well for anything from tandems to bigways.

    I really do not understand the reason for ringsights. All I hear is "if you are a professional, you should have one". I could be wrong, but so far I have not heard of any real benefits.