Multi - Opinions?

[keely]

I am curious to hear opinions from experienced jumpers about the multi - reasons for having it or reasons for not having it. I have seen video of a very MINOR malfunction that APPEARED to be caused by the multi (let me stress that I do not know for sure the multi was the cause), and I would like to know if anyone else has ever had a problem associated with the multi? Also I am not completely clear on reasons for using the multi, so if anyone would care to share their opinions on this I'd love to hear it...

Thanks! :-)
Keely Mires

[imported_Tom Aiello]

Here's my experience on the multi--you decide if my thoughts are worthwhile:

I made the decision to purchase a multi-equipped BASE canopy (my first) when I had one BASE jump. I made the decision based on photos shown to me by Nick at BR (I bet BR still has the photos, if you ask them).

I subsequently made around two hundred jumps on my multi-equipped canopy. I then purchased another (non-multi) canopy, and made around a hundred on each of the two.

So, to date, my thoughts are based on around 300 multi jumps, and around 100 non-multi jumps.

Here are my thoughts:

I do think the multi has some value in maintaining the pack job's shape while it travels to line stretch. This ought to improve the opening characteristics with regard to heading and opening speed. This improvement ought to be especially noticeable at high airspeeds (so the multi ought to be more useful the closer you get to terminal). However, opening characteristics are more critical at low airspeeds.

I have not personally observed a noticeable difference in openings with or without the multi at low (slider down) airspeeds (the majority of my jumps). Aside from a few incidentals (I can feel the way the canopy flies differently with a very large PC, for example, as the multi appears to minimize "anchor distortion"), I have been unable to make a definitive determination on the issue.

In other words, I can't really tell the difference.

While the theory is sound, and I am very interested in what the next generation of multi's bring us, I don't thing it is worth the extra $150 at this point.

--Tom Aiello
tbaiello@ucdavis.edu

[feral]

Just to let the base jumping public know a certian tall ozzie does not use the multi ..Why i here you ask....because it add's time to his pack job ...Next time you pack or watch someone pack with a multi take time to see how long you spend on the multi....big Di{khead he is Ha Ha Ha


bsbd feral

[Dwain]

It is generally presumed in parachuting that a neater pack job has a lower chance of malfunction than a messy pack job. This one of the reasons that reserve pack jobs are so neat compared to main pack jobs in skydiving.

Avoiding deployment malfunction is our number one focus with a single parachute system in BASE. Heading performance is our number two focus. In BASE a symmetrical pack job and symmetrical extraction often defines heading more than neatness.

Now if the general assumption of the effect of pack job neatness on malfunction rate is true, one could further ascertain that the neatness of the material folding comes into effect at the point of line stretch - not how the material sits in the container.

There is no doubt that a freepacked multi-equipped canopy reaches line stretch in a closer configuration to how you packed it (i.e. a neater configuration) than a freepacked single-bridle attachment canopy. There are countless photos and video to support this.

Based on the assumption that a neater pack job has a lower chance of malfunction than a messy pack job we can subsequently hypothesize that a multi-equipped canopy will have a lower malfunction rate (ignoring the potential variable that the added complexity of a multi can in itself induce a malfunction - something that has not been proved or disproved at this stage and is an entire separate topic in itself).

So the logic is as follows:
Multi = neater pack job on line stretch.
Neater pack job = lower malfunction rate.
Therefore it is hypothesized that:
Multi = lower malfunction rate.

Now the question follows: Does the existing data support this hypothesis?

Basically we don't have sufficient data to test it. If the serious malfunction rate of a correctly configured, packed and deployed single-bridle-attachment BASE canopy is for example; one in 8,000 and with the multi it is one in 11,000 then we currently have insufficient data to make any conclusions. Comparing several hundred jumps is like examining a drop and making statements about the ocean.
(Note that we won't have sufficient data until people start electronically logging their jumps in a detailed format and pooling this data in one central place (names and locations removed of course). Once we have a data pool of say 50,000 BASE jumps then some very interesting statistical analysis can be done. The truth is out there - its just spread out amongst everyone's log books).

We can however relate our experiences of the multi in regards to the effect it has on other things (things which are secondary to its primary purpose which is to reduce the malfunction rate). The only difference I personally feel is on terminal deployments of freepacked canopies (note the use of the word personal: personal = subjective = not much value should be assigned to it). Basically I have found I get more consistent deployments at terminal in regards to altitude used with multi equipped canopies. This is only really noticeable when I smoke it into the dirt. Other people have stated they don't notice a difference at terminal. I personally do and therefore prefer to have a multi equipped canopy when dumping near or at terminal (but it's a nice-to-have not a must-have for me).

So the question is; For general BASE jumping, is jumping a multi equipped canopy safer than using a single bridle attachment point canopy (and therefore worth the extra $150 and added complexity)? No one can say for sure at this stage, we can just hypothesis.
Are the secondary effects alone worth the multi? Perhaps – depends on the individual.

Note: In this discussion I was just referring to F1-11 (0-3 cfm) canopies. It is pretty well established that in regards to entire ZP top skin BASE canopies, the single bridle attachment has a much poorer heading rate than the multi (believed in part due to the substantial effect of ZP on center cell stripping).

[Karin]

Hey there Keely,

Dontcha just love techie-talk? I thought I'd give my two cents cuz you're a beginning female jumper that asks important questions, and I like that in you.

I have 3 canopies with multi's and one canopy that does not, and to be perfectly honest, I really do wish that I had a multi on all of them.

When faced with my initial decision on whether or not to order a multi, I opted to do without because I instinctively felt that it added some degree of complexity to the system. But soon after, I ordered an additional canopy with the multi added, and after watching countless videos/photos of pack extractions on both multi & non-multi equipped canopies, I began to cringe every time I saw the extreme CC strip & subsequent slump on my non-multi canopy. The multi extractions are quite nice right out of the container, appearing as though the pack job is being lifted out with the same shape integrity of how it was initially placed in the tray.

And don't get me wrong - the non-multi canopy is great for the most part, in that it functions the way it should - there is no difference in the deployment process staging, the headings are fair and I have had no problems/mals to speak of because of the single-bridle-attachment. For me, liking the multi is very much a matter of feeling comfortable with and believing in the concept/idea of a particular feature and its intended benefit. And of course, it's a given that there is a never-ending list of ever-present variables in each and every jump situation that must be taken into consideration (gear size/age/condition, packing, site & weather particulars, body position, PC size/delay etc.) that can all affect one's opening.

The packing thing is a non-issue as far as I'm concerned. It takes 2 extra seconds to close the sheath and 2 more seconds to stow the multi on closing. If you're concerned about the sheath restricting the multi, it is not a grave concern for me personally based on my experience with them so far - I've observed that the sheaths often stay partially closed (on the section furthest from the attachment point) on many of my openings, and it does not affect or deform my openings.

I have consistently jumped with the sheath closed on jumps as low as 157 ft. static-lines and any/all freefalls. BUT if I were intending to FF something lower than say, 200 ft., I'd personally probably prefer to keep the sheath open, snake the multi outside of the closing bands and take whatever other nasty-low precautions on might take, just to be on the "safe" side (which may or may not be more mental comfort stuff). Also to mention, I generally always use the closing bands built into the containers (unless there are none), and I only place a small small small bite of multi into each band, only enough to keep it neatly contained, and usually using only 2 of the provided stows.

If you'd like, I can e-mail (or show you when I see you) some photos of my multi vs. non-multi extractions. Or I'm sure that Anne has some cool & groovy footage lying around, which may be easier since she's you're roomie! You're definately lucky to have her knowledge handy and she can be quite objective with all of the pros/cons of gear.

OK, now when are we gonna go play? :D

BS&BBBBD

[d-dog]

I can add no technical data to those put forth by Tom, Dwain, and Karin. However, I can second a comment Karin has made.

For me, the multi makes logical sense. A more organized pack job on line stretch/extraction seems less likely to mal, and less likely to open off-heading. Perhaps there is as much intuition as logic going on, but in either case it "feels" like a multi setup could give a fractional improvement in both of these highly-important variables.

The downside of the multi that I can see is an additional variable that could go wrong during deployment, i.e. a multi-specific tangle or mal. I can't see, again just logically, how the stowed multi is inherently more likely to tangle than the bridle itself. Again, just gut sense and experience in packing 20+ multi canopies which I've jumped.

Thus, jumping a multi makes me FEEL a little bit safer, like I rounded one more figure up in my favor. This in turn makes me a bit more confident on exit point, and a tad bit more calm in mid-jump. I believe this little extra bit of confidence helps my jumping to be sharper and more "on point." Ergo, irrespective of the multi's actual statistical improvement of my extractions and heading performance (or lack thereof), I jump better (and this safer) with that little extra confidence. I feel this overcomes any potential downside risk in multi-specific mals.

In other words, placebo or not I think the multi helps my jumping and thus I prefer to jump a multi.

Karin makes good points about super low jumps, and I too would not fasten velcro on a sub-200 freefall. I have made many 300-ish multi jumps and never noticed any hesitation at this height that I could pin onto the multi. Now, PC hesitations are a whole diffferent matter right Dwain ;-0

I've also see the topmost velcro sheath closing segment stay closed on my multi canopy after jumping on several occasions, and Karin has noticed. In fact, I once packed up from a jump only to notice that the top THREE velcro sections were still closed post-jump. What the he11's up with that? I wrote it off to gremlins and just tried to forget I saw it, as it doesn't make logical sense that this could be the case post-jump. Then again, maybe I was just suffering from sleep deprivation or something from climbing local towers too many times at 1am.

Now, if only those bastards in Amsterdam hadn't stolen my multi-equipped Fox then I'd be in good shape. Grrrrr.

Peace,

D-d0g
ddog@wrinko.com

[Nick]

Going back in history is one way to understand the Multi and how it came about.

It's the story of reefing . . .

When round parachutes are being used for skydiving they were freepacked at first, and this worked well because a round parachute has one common center point (it's apex) and thus gets pulled to line stretch pretty much the way you packed it.

The problem that remained is line-overs (partial inversions) caused by something called secondary opening shock. (The apex rebounds down to the skirt, or bottom of the canopy and sometimes goes right on thru the lines). If it turns completely inside out, you were lucky and could land it. You just looked funny coming down with your bridle and pilot chute hanging down above your head inside the canopy.

The cure for these inversions was to slow down the inflation speed in order to prevent the rebound from being so severe. The answer was reefing.

First they tried a LOPD (Line-Over Prevention Device). This was a loop and pin affair that prevented the canopy from catching air before the completion of line stretch. It was a tad scary, and didn't always work correctly.

Then they came up with the sleeve. The sleeve covered the entire round parachute and would not come off until line stretch. Jumpers of the day (mid-60s) staged a minor revolt when USPA (then called PCA) said sleeves were now mandatory at certain drop zones and competitions.

The sleeve soon became the norm and evolved into another device called a POD which was half sleeve and half bag. Around this time an assortment of other devices became available like the free pack strap (death strap) and various other methods of "almost" freepacking. Finally the present day deployment bag is perfected.

A few jumpers don't like bags at all and just freepacked. While the opening shocks were bad, the canopies held up to this kind of abuse because the average skydiving square of the mid 70s was very over built compared to today's mains. (If you didn't get a 1000 jumps from your $600 Strato Cloud you were on the phone bitching to Para-Flite about it).

In BASE jumping up until the early 1980s we are using the same gear at the Flatiron building that we used at the drop zone. However, because we were closer to the ground, we gave up opening comfort for opening speed and off came the deployment bags and off came the sliders.

Now we're back to having line overs again.

Rather than add another layer of reefing to what we were trying to make as simple as possible, someone came up with the line-over prevention modification. This fix carried BASE jumping for many years, but it was a continual battle teaching newbies to use it and even those who had it sometimes couldn't manage to use it correctly.

Enter the tailgate and the multi.

I'll spare you the story of center cell stripping (it's long and elsewhere on this board) but the multi is simply a way to get your square to full line stretch without the center cell being pulled from the center of the pack job. The tailgate prevents tail flutter which is the begining of square line-over.

Are these the best ways?

Like the sleeve, pods and bags that came before these have major advantages and some minor disadvantages. However, the fact you don't hear about people spiraling into the ground, as much as we used to, testifies to the fact that we are getting better at this thing slowly but surely.

Nick ;-)
BASE 194