0
base698

Skyhook

Recommended Posts

jumpsalot-2

Was it a left hand toss ? Where was it stowed ?



Seems I remember hearing about an Aussie system years ago that utilized a pull out pin reserve pilot chute set up with the pud on the left shoulder. Was that real or was I just a noob being fed a line of bonfire bs?
Chuck Akers
D-10855
Houston, TX

Share this post


Link to post
Share on other sites
In the late 70's Sandy R and Jim T built double throw out rigs with the worlds first curved pin and first BOC and TOC pouches. The rig had $40 worth of material minimal hardware and harness and container weighed around 2lbs. Reserve could be deployed with either hand and complicated 3-rings were not used, although they were a good application to parachutes. An Australian saw the rig that Sandy had and went wild. Shortly after, the Australian poor quality rigs were produced that did not resemble ours that much. As far as an AAD, that was not an issue then. Seems that with a little thought, that could be figured out.

Share this post


Link to post
Share on other sites
billbooth

The burble behind a fully inflated wing suit is gigantic. I'm sure you've seen the video of an entire deploying main canopy, at line stretch, literally sucked back all the way to the jumper. Wingsuits were tried in the 30's and 50's, but almost everyone died. The reason was everyone was jumping spring loaded pilot chutes. It wasn't until the introduction of the hand deployed pilot chute, that modern wing suiting became possible.

So, in answer to your question: Deploying a spring loaded pilot chute of any description, behind a wing suit, in certain flight modes, is very likely to produce a terrible pilot chute hesitation. If you're depending on an AAD set at normal settings (below 1,000 ft.), you're probably going to die if you ever need it. The Skyhook has nothing to do with it.

PS. I've often thought that what wingsuiters really need is a rig with a hand deploy reserve. You couldn't have an AAD, but for the above stated reason, even if an AAD fires at its set altitude, you do not have a not very good chance of an "in-time" deployment anyway.



Bill,

I'm not sure if anyone has brought this up yet (and if it has someone feel free to quote the reply)

The 5 ft red lanyard is designed to disconnect at 10 lbs of force, correct?

Independent testing of your RPCs has shown that it takes 40-50 mph of laminar flow to generate said 10 lbs of force.

What chance does that RPC have with a burble in the equation considering an unconscious wingsuitter has been shown (in previous incidents) to fly at as low as 45 miles an hour vertical prior to any burble lessening the pull on the RPC? Have you considered that?

Given that, is the skyhook a bad idea with a wingsuit? Would an alternate, easier-to-detach MARD and perhaps higher drag RPC be a better gear combination?

(Full disclosure: I don't own a Vector, but my wife does. It doesn't have a skyhook due to the concerns mentioned above.)

Thanks
-Lyosha

Share this post


Link to post
Share on other sites
The force required to break the red rigger seal thread is closer to 5 lbs. This amount is necessary for any MARD system, because without it, the system would prematurely release all the time, especially in the large burble behind a wing suit. I tried pin and loop MARDs first (over 30 years ago), but abandoned them because of the premature release problem.

Also remember that during a breakaway, the MARD pulls on the plot chute as well as the bag. The unique 5-1 lever action of the Skyhook keeps the system together when the pilot chute is below the bag (after a breakaway), with a force equal to five times the weight of the free bag and canopy. Pin and loop systems have no such provision. Also, all other MARDs lack the Collins' lanyard, which in my opinion, makes them unsafe to use.

Remember, the Skyhook has be installed on over 30,000 rigs over the last 17 years. To say that any other MARD works better might be a bit premature, don't ya' think?

Share this post


Link to post
Share on other sites
Hi Bill,

Quote

The force required to break the red rigger seal thread is closer to 5 lbs.



Back in '08 I did some testing with two turns of red rigger's thread and the results were:

High: 26 lbs
Low: 23 lbs
Average: 24 lbs

It was not the most scientific test that I have ever completed but it gave the info that I wanted.

Jerry Baumchen

Share this post


Link to post
Share on other sites
JerryBaumchen

Hi Bill,

Quote

The force required to break the red rigger seal thread is closer to 5 lbs.



Back in '08 I did some testing with two turns of red rigger's thread and the results were:

High: 26 lbs
Low: 23 lbs

Average: 24 lbs

It was not the most scientific test that I have ever completed but it gave the info that I wanted.


Jerry;

If that were true, it means that the same red seal thread would add an average of 24 lbs. to every reserve pull and all ripcords would fail the required 22 lb. test.

Bill

Jerry Baumchen

Share this post


Link to post
Share on other sites
Hang on.
Jerry mentioned 2 turns, not the normal 1 turn either on a Skyhook or reserve seal.
So if it is about 5 lb thread (at least), then when it is in a loop one will expect 10 lbs (at least) too.

[Edited a couple hours later: forces depend on the geometry too for the Skyhook, where the angle of the thread will change depending on the slack in it.]

So the numbers don't sound totally out of place.

For a reserve seal, it is normally slack so the reserve pin is already moving when the seal thread "is hit". Bill Booth I'm sure you mentioned such stuff before -- you get some momentum going with your fist on the handle so it becomes easier than the static pull numbers would suggest.
Also, nobody tests reserves with seal thread do they?

Just dashing this off quickly; I'll let others debate pull test standards.

Share this post


Link to post
Share on other sites
Bill,

Thank you for your reply. I very much agree with many things that you have said, and am a fan of your work and containers (I did buy my wife a Vector after all...). I also appreciate that your containers have a Collins lanyard - even in rigs that have an RSL. I'm very much on board with that. I have a friend who had one riser disconnect that's lucky he could dig out the remaining cables in time.

Lets pretend other containers don't exist in the world for a moment - because while I understand that you run a business in which you try to prove that your product is superior to others on the market, my interest as a consumer is to maximize my personal safety.

While it is a strong point that the skyhook has been installed in 30,000 rigs over 17 years, "modern" "large" wingsuits have only taken off a year to two years or so - sometime around the time Squirrel came out with the Freak. When I started wingsuitting there were maybe two people to a dropzone that wore the big suits - now it seems every person with 20 jumps on an i-bird and 10 more in a rented R-bird has a squirrel freak on order. So while the Skyhook has been thoroughly vetted in the environment it has been vetted in, your quote about skydivers finding new ways to break themselves appears to have been prophetic yet again. It seems the environment changed. At least partially.

In the paper that I found that measures RPC pull force has the vector version pretty much flatlined until 40-50 mph laminar, at which point it starts to climb. I think it's a reasonable assumption that the current iteration of Vector RPC would never reach the drag required to break that string when trailing behind a wingsuit - considering there is concrete evidence of someone descending at 45 mph until impact.

Given that, would you redesign/modify your current system in any way for the purpose of wingsuiting? Do you still think the advantages of having a skyhook outweigh the potential complications? Would you change anything about the current reserve/MARD system to make it better compatible with wingsuiting?

I understand these are pointed questions, and apologize and thank you in advance.

Share this post


Link to post
Share on other sites
pchapman


For a reserve seal, it is normally slack so the reserve pin is already moving when the seal thread "is hit". Bill Booth I'm sure you mentioned such stuff before -- you get some momentum going with your fist on the handle so it becomes easier than the static pull numbers would suggest.



This explains this in a very clear manner (static vs dynamic pull, break force required):

https://www.youtube.com/watch?v=6q5TZgvIz14


.

Share this post


Link to post
Share on other sites
Of course I know, and have written about, measuring pull forces applied at different velocities for years. My reply was a purposefully simplistic reply to a simplistic remark. In real life things are much more complex.

Everything I have designed in my life was the result of seeing a problem I thought needed solving...and a lot of these problems resulted from jumpers "pushing the envelope", just as wingsuiters are now doing. It is very possible that wingsuiters need gear that is specially designed for them. Problem is, I'm not a wingsuiter, and therefore do not experience these problems personally. All I know is what I see in videos, so I do need input from them about what they perceive their problems to be, just as I am getting here. I will schedule some tests to see if your assumptions have merit.

Share this post


Link to post
Share on other sites
billbooth

***Hi Bill,

Quote

The force required to break the red rigger seal thread is closer to 5 lbs.



Back in '08 I did some testing with two turns of red rigger's thread and the results were:

High: 26 lbs
Low: 23 lbs

Average: 24 lbs

It was not the most scientific test that I have ever completed but it gave the info that I wanted.



Jerry;

If that were true, it means that the same red seal thread would add an average of 24 lbs. to every reserve pull and all ripcords would fail the required 22 lb. test.

Bill

I'm repacking my reserve and decided to measure the Skyhook disconnect force myself. It took 4.7 lbs to extract the green and red lanyards from their respective pockets. The disconnect force, measured three times, was 12.0, 12.5, and 11.3 lbs. I made these measurements by pulling straight up with a peak-hold digital gauge attached to a slip knot in the bridle. 24 lbs for two passes of the seal thread seems reasonable to me.

Share this post


Link to post
Share on other sites
As in most other cases, the speed at which the force is applied can make a big difference. When the force is applied rather quickly, like with an inflating pilot chute, the force required to break the thread is more like 4 lbs. When measured with our dynamic tester with a sampling rate of 50 htz. I agree the force reads higher when applied very slowly with a fish scale. The same relationship exists when measuring ripcord pull forces. As I've said before, a MARD must have some "hold together" force or it will release prematurely during spinning malfunctions.

Share this post


Link to post
Share on other sites
billbooth

Of course I know, and have written about, measuring pull forces applied at different velocities for years. My reply was a purposefully simplistic reply to a simplistic remark. In real life things are much more complex.

Everything I have designed in my life was the result of seeing a problem I thought needed solving...and a lot of these problems resulted from jumpers "pushing the envelope", just as wingsuiters are now doing. It is very possible that wingsuiters need gear that is specially designed for them. Problem is, I'm not a wingsuiter, and therefore do not experience these problems personally. All I know is what I see in videos, so I do need input from them about what they perceive their problems to be, just as I am getting here. I will schedule some tests to see if your assumptions have merit.



Bill,

Have you had the opportunity to test my hypothesis?

Share this post


Link to post
Share on other sites
lyosha



In the paper that I found that measures RPC pull force has the vector version pretty much flatlined until 40-50 mph laminar, at which point it starts to climb. I think it's a reasonable assumption that the current iteration of Vector RPC would never reach the drag required to break that string when trailing behind a wingsuit - considering there is concrete evidence of someone descending at 45 mph until impact.



At the same time though, if the RPC is unable to break the 10 lb thread seal, then it also is unlikely to produce enough force to deploy the reserve. Remember, the RPC needs to lift its own weight, the bridle, the weight of the reserve parachute, the freebag and then on top of that, the added weight of releasing the locking stows. That easily exceeds 10 lbs.

Where is the evidence of someone descending at 45 MPH until impact? I would be interested in seeing it.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

0