dgw

10 hours ago, gowlerk said:

The UK is getting to be quite the nanny state.

You can have trigger locks on fuel pumps in the UK, but only if the fuelling is done by an attendant. 
 

Nearly all fuel stations are self service these days however. 

7 hours ago, jumpsracer said:

I'm jumping a PD demo Stilleto. Are there any special packing tips for it?

Pack it normally. I’ve pro packed and ‘psycho’ packed them.

Pay very close attention to a flat stable deployment.  I don’t have a lot of experience on Stilettos, but the only opening problem was an own goal, deploying on the hill on a hop’n’pop whilst not quite square to the relative wind. On my Safire2 or Sabre2 it wouldn’t have been a problem. On the Stiletto, it was an immediate and serious problem. 

Yes.

 

click the black circle or star to the left of the thread title - that takes you to the first unread post. 

Problem solved. 

1 hour ago, gowlerk said:

And he has no political power. He can't even vote.

He can dissolve parliament at any time he chooses. 
 

https://en.wikipedia.org/wiki/Dissolution_of_the_Parliament_of_the_United_Kingdom

10 minutes ago, kallend said:

She admits taking banned drugs into Russia.  How stupid can you be?

"American WNBA star Brittney Griner pleaded guilty to carrying cannabis oil on the second day of her closely watched trial in Russia".

Do you think that she should lie? To a Court? 

3 hours ago, olofscience said:

War is a negative-sum game. The winner also loses.

I think that is right. I think a lot of historic wars (in Ireland) were about having a war to lose the least amount of resource, knowing that sooner or later a war was going to happen. No nukes, of course. 

18 minutes ago, winsor said:

I thought gay Catholic men were called "Priests."

Shameful comment. 

3 hours ago, skyderrill66 said:

You obviously have a bone to pick with aerodyne

I have no dog in this fight at all. If the bone is real however, I say pick all the meat off it and fully expose the bone.

It seems to me that this issue could be tested by any competent rigger with access to similar harness-container / parachute combinations. 

I don’t think this website caries the weight it once did in informing people by skilled, knowledgable, and esteemed peers. I do think, however, that Aerodyne should answer this challenge for the purposes of both finding the issue (whatever it is) in the complainant’s video and, assuming the bone is clean, protecting their reputation. 

25 minutes ago, olofscience said:

Very informative link! Following their sources actually leads to a NASA design:

https://ntrs.nasa.gov/citations/19730010159

Edit: it seems rock climbers already have something that we could theoretically repurpose:

Yes. That is what I thought Coolbeans more or less had in mind. I noted your comment responding to me but I couldn’t reply earlier. My thoughts were that, for this sort of idea, more thread  / stitches = less riser stretch over a bit longer time than in a normal deployment. That was it. The injury risk is not just acceleration related, but duration related. 

Here is a study on fall arrest harnesses / acceleration / impulse published by the UK Government’s Health and Safety Laboratory. I think it touches on your idea, and might help.

https://www.hse.gov.uk/research/hsl_pdf/2003/hsl03-09.pdf

On 6/2/2020 at 9:55 AM, CoolBeans said:

I've been thinking of simple riser design to absorb some of the hard opening energy. In a similar way that crumple zones work in the car. Those zones could be for example: 7G, 7.5G, 8G, 8.5G, 9G, 9.5G, 10G etc. Below is my simple prototype, in real world, using modern technology, those zones could be integrated into the riser (webbing) itself. I believe professional name for that is tear webbing or shock absorbing webbing.

Disadvantages?

• crumple zones could break unevenly which would result in uneven lengths of risers
• crumple zones could break when not desired, for example during high performance low turn
• after hard opening crumple zones would leave jumper with extra long risers which, depending on design, might not be landable anymore and may require cutaway
• crumple zones will have tolerance that will change over time; ones that initially were designed to tear at 7G after years may tear at 6G which could happen unexpectedly during high performance maneuver
• in order to operate properly, those risers would have to be rated for very limited body weights, e.g. 150-155 lbs only
• torn risers would have to be replaced which is extra cost for jumper

Advantages

• crumple zones should not affect base riser strength
• crumple zones would absorb some of the hard opening energy
• risers with crumple zones should be very similar to regular risers and wouldn't require any other equipment modifications
• risers with crumple zones should behave exactly like regular risers in < 7G conditions; no extra flex should be observed
• risers with crumple zones could potentially be beneficial in fast spinning malfunctions as they would lengthen the risers making the spin slower

What do you think? I think some other industries already use similar approach, e.g. Petzl ASAP`SORBER https://www.petzl.com/US/en/Professional/Mobile-fall-arresters/ASAP-SORBER

_________
Assumptions

• hard opening that would require extra shock absorption is above 7G
• any regular canopy maneuvers are below 6G
• crumple zones should preferably be numerous and short, as short as possible ; that way if 1 zone tears at undesired moment, it shouldn't cause too much damage

You might want to have a look at some of the injury tolerance research. It might help with understanding the relevance of the opening deceleration and impulse to risk of injury. 
 

https://humanresearchroadmap.nasa.gov/evidence/reports/Occupant Protection.pdf

Here’s an extract setting out some relationships between deceleration, impulse, and injury:

 

On 6/18/2020 at 8:28 PM, olofscience said:

Someone posted something similar earlier this thread, but I thought it was still viable until I did some calculations.

Assuming that freefall speed is 120 mph (54 m/s), and canopy speed is 14 m/s (30 mph - still pretty fast), if the opening takes 1 second (pretty hard opening) you'll get about 4 Gs.

That doesn't sound very high until you realise the upright position is quite bad for this kind of acceleration.

Let's assume it's even worse, say your canopy opens in 0.5 s, giving an 8G acceleration.

If we were to completely absorb 0.5 seconds with an elastic stretching to bring it back to 4 G's, you'll need 10 metres of stretching since you're trying to get rid of 40 m/s (from 54 to 14 m/s).

Even if you're just trying to mitigate the very worst case, say 0.25-second opening which causes 16 G's, you'll need 5 metres of stretching to bring it down to 8 G's.

If your risers are stiffer and don't stretch 5 metres, they won't relieve the acceleration anyway. It would be like trying to use water to break a terminal freefall - it will feel hard as concrete when you get a hard opening.

So as much as I wanted this elastic stretching idea to work, unfortunately it probably won't. However, what might work is if the risers break completely at a certain load - if the RSL or a MARD is connected, then the reserve might give you a second chance of not opening so hard.

 

I might have missed the point entirely here, but it seems to me that Mr Beans had an idea that ‘fall arrest’ type risers might ameliorate opening acceleration, not by stretching of the risers, but by failure of the thread in the stitching in the sewn parallel ‘accordion’ of webbing. So, I don’t think his idea needs metres of webbing, but it might need meters of thread. 
$0.02 

1 hour ago, olofscience said:

How about some magnets to hold the slider corners against the start of the line groups until the canopy inflates more? It could help solve sliders coming down too fast. Would also keep the canopy size constrained to the sliders until inflation overcomes the magnets.

Just throwing some thinking out there...

I expect that they would all just coalesce into one group of magnets in the pack job. That might hinder the slider opening correctly, and therefore hinder proper opening. 
My $0.02

Two minor things.

Clicking on a fully open thread does not open the thread, it just reloads the sub forum.

When one opens a thread with new posts, the first new posters name is off the top of the screen. One has to scroll the screen down to see who the poster is (if one doesn’t recognise the posters avatar) and then read the contribution.

This is what it looks like on a random pick:

It’s a minor thing but it niggles me a little. 

I echo the thanks offered above for the effort put into this site improvement. 

13 hours ago, 20kN said:

I'd say more like for all skydivers, except possibly CReW Dogs. There seems to be a mentality that newer jumpers should have an RSL, but once you know what you're doing then you dont need one anymore. Of course you are free to do as you feel is best, but most of the actual fatalities I know about where an RSL would likely have saved the jumper's life involved a very experienced skydiver and not a newbie.

This is what Dan BC has to say on the topic: http://danbrodsky-chenfeld.com/blog/2013/06/27/safety-tips-for-skydiving-and-life-as-well/

Agreed. I am very much pro RSL / MARD. However, people should arrive at their own informed view. My issue in that regard was that the coach was promoting the no-RSL rig as superior equipment, without at least covering the pros of RSL / MARD rigs. 

 

3 hours ago, shorehambeach said:

 

Another great thing to do it get on a canopy course. Money well spent.

 

Blue Skies. 

They can be money well spent, but I sound a note of caution.

I have attended on two occasions such courses in the UK by a known outfit. On one occasion, the advice for getting back from a long spot with a tail wind was to make oneself as large as possible so that the tail wind would push one more efficiently through the air. I challenged this and eventually prevailed, but only temporarily - by the next day, he had thought about it further and reverted to his former understanding. That advice has also been given by a well known diminutive  coach, I am reliably informed by a former team mate.

Secondly, attendees at the second course were encouraged to use ‘clean equipment’, by which he meant rigs with no RSL or MARD for reasons of getting stable etc, without at least acknowledging the potential pros and cons of both philosophies.  For newer skydivers, this is poor practice. 

Caveat emptor, and those that fly with them. 

1 hour ago, skydiverek said:

I agree, same here. Loads forever !

 

I note the same. I’ve used the site on desktop, mobile phone and tablet since the inception of the new site. All devices are fewer than 24 months old and are up to date on operating systems.

On the iPad, and the windows computer, each time I click on a link, the secure site padlock disappears, there then follows a pause of a few or up to twenty seconds, and the ‘secure’ padlock reappears. As soon as the padlock appears, service is normally quick. 

I also miss the ‘how many new posts’ red number. That was the most useful part of the old presentation format in my opinion / usage.

Many thanks for the effort put in to this. 

I have a V348 with a Smart 150 and a V348 with a PD160.

The Smart is a much more comfortable / smaller fit than the PD160.

The attached is from the PD Horizon manual.

I'll leave the physics to Yuri.

I think the physics of what you say is difficult to refute. I agree with the idea. Safe implementation might be a practical issue, but implementation of the 'standard' method is also potentially a practical problem.

Out of curiosity, I downloaded a PD reserve manual to see what the practice is on (a) reserve parachute. It's a TR-375, which was just the first manual that I happened upon.

The attached photograph shows the slider packing method to be ES

LeeroyJenkins

***Given that lots of malfunctions are low speed reserve deployments, it is still a valid concern
And certainly an expectation that the pilot chute is going to extract the reserve bag. And in a timely fashion.

Not bashing on the Wings container, I have pilot chute in tow on reserves before, on tandems, on my own gear, and I do not actually give a shit what the excuse is, the gear did not do its job. Seconds matter. altitude matters. Too many dead skydivers here to be making excuses.

Nothing pisses me off more when you take a concern to a manufacturer, (more and more with documented video) and you still (decades later) get to hear similar excuses for why shit does not work.

The gear is supposed to work. We demand it. Especially in urgent situations

Wings listened and they changed the reserve PC design.

What about all of the legacy equipment? 6 years of new pilotchute does not cover off a large fleet of 6+ year old Wings containers in the field.

Deimian

I jump a vector. My flaps overlap way more than that. It looks to me like the loop is way too long. Have you checked with your rigger?

His side flaps look pretty similar to the manual image to me. (I am not a rigger.)

It doesn't have to be. You can use the 'alternative' method and have the kill line window visible.

obelixtim

Jury has failed to reach a verdict and has been discharged. It sounds like there were some shenanigans in the jury room.

Quote

Emile Cilliers will face a retrial after the jury was dismissed on Thursday, a day after the judge warned its members against bullying between them.

This is all very strange, but obviously the prosecution didn't do enough to convince the jury of his guilt, certainly not enough to get a majority decision.

Here's an article from The Times of 24 November. It sets it out reasonably clearly, in my opinion.