Forums: Skydiving: Gear and Rigging:
Round Parachute Reserve Question

 


shibu  (C 42074)

Sep 27, 2012, 11:05 AM
Post #1 of 24 (4007 views)
Shortcut
Round Parachute Reserve Question Can't Post

Just curious why the front mounted reserve parachutes appear to be so much smaller than the mains. I understand why the mains are so big now that I have seen them packed (on video) but how can the reserve fit into such a small package? Are they just smaller?


ctrph8  (D License)

Sep 27, 2012, 11:16 AM
Post #2 of 24 (3985 views)
Shortcut
Re: [shibu] Round Parachute Reserve Question [In reply to] Can't Post

Chest mount reserves can be smaller but can also be as big or bigger. There really isn't much to a chest mounted reserve container. It is 4 flaps, a deployment system which might or might not have a pilot chute, a canopy and some risers. They are not trying to make it comfortable or flat against your back. A back style parachute also has the harness, a cutaway system, the deployment system, padding (maybe) and is usually meant to be wide and flat for comfort. There is a lot of other stuff in there besides canopy which makes it look big as compared to a chest mount.


In reply to:
Just curious why the front mounted reserve parachutes appear to be so much smaller than the mains. I understand why the mains are so big now that I have seen them packed (on video) but how can the reserve fit into such a small package? Are they just smaller?


airtwardo  (D License)

Sep 27, 2012, 11:50 AM
Post #3 of 24 (3951 views)
Shortcut
Re: [ctrph8] Round Parachute Reserve Question [In reply to] Can't Post

There is/was also a sleeve or bag on the main which increased the volume considerably.

The heavy cotton sleeve on my Pap was as big 'pack volume wise' as the canopy it held...


pchapman  (D 1014)

Sep 27, 2012, 12:13 PM
Post #4 of 24 (3936 views)
Shortcut
Re: [shibu] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
Just curious why the front mounted reserve parachutes appear to be so much smaller than the mains.

Typical skydiving round canopies of the late 60's and early 70's had a sleeve, which added a LOT of bulk, and many were of a more complex design then the reserve and were bulkier for that reason.

In the era before custom civilian rigs, military bailout rigs were often converted for skydiving use.

So the military backpack might have, for example, contained a 26' Navy conical, and was relatively thin. The canopy was exactly the same as might have been used in a civilian jumper's belly reserve. So the canopy bulk would be the same, although what it would "appear" to be would depend on whether you thought the spread out but thin backpack seemed "bigger" than a lumpy belly mount or the reverse.

But for the civilian skydiver putting a ParaCommander or similar canopy in the backpack, the sides would be extended a few inches with sewn-in additions, to fit the bulk of the canopy & sleeve. (Rigs that were made for civilians later, could of course be sewn the right size from the start.)

The ParaCommander has something like 24 different holes and slots in it, which means a lot of extra tapes supporting the edges of holes. I'm not sure, but I'm guessing that added a fair bit to the bulk.

But the big thing is the sleeve. That's a heavy cotton "sock" that slides over the canopy from end to end -- so it is going to be 12 ft long or so. Instead of folding the canopy and then putting it into a bag as we now do, the canopy went in, then it was folded. To prevent nylon on nylon burns, the sleeve was cotton, and usually quite heavy.

Have you ever seen one of the big, baggy, cotton freefly jumpsuits from the early days of the discipline, say the mid 1990s? Stuff that in your rig, and that's roughly how bulky a sleeve is.

Reserves were much simpler in design, maybe with 3 open vents or meshed panels at the back for forward speed. And they didn't use a sleeve to slow the deployment. (Later ones would use a diaper that just wrapped the mouth of the round canopy until the lines were stretched out.)

Another factor is that the main container had to be sized for quick packing in the field, while the reserve container could be super tight with the rigger sweating over it for a while!

Old timers will know more, but I think that is a reasonable explanation why the "typical" skydiving rig with a belly mount reserve seemed to have so much bigger a main container.


HHypoxic

Sep 27, 2012, 12:43 PM
Post #5 of 24 (3912 views)
Shortcut
Re: [pchapman] Round Parachute Reserve Question [In reply to] Can't Post

Typical skydiving round canopies of the late 60's and early 70's had a sleeve, which added a LOT of bulk, and many were of a more complex design then the reserve and were bulkier for that reason.
_________________________________________________


I can't resist! http://www.youtube.com/watch?v=RH9kaxWQjfA


JerryBaumchen  (D 1543)

Sep 27, 2012, 4:28 PM
Post #6 of 24 (3846 views)
Shortcut
Re: [pchapman] Round Parachute Reserve Question [In reply to] Can't Post

Hi Peter,

Quote:
But for the civilian skydiver putting a ParaCommander or similar canopy in the backpack, the sides would be extended a few inches with sewn-in additions, to fit the bulk of the canopy & sleeve.

Adding extensions was only for the wussies.

Real men grunted those puppies closed every time.

Cool

Or should I make that: Pirate

JerryBaumchen


Skydivesg  (D 10938)

Sep 28, 2012, 9:33 AM
Post #7 of 24 (3749 views)
Shortcut
Re: [HHypoxic] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
Typical skydiving round canopies of the late 60's and early 70's had a sleeve, which added a LOT of bulk, and many were of a more complex design then the reserve and were bulkier for that reason.
_________________________________________________


I can't resist! http://www.youtube.com/watch?v=RH9kaxWQjfA

Good one........ oh... was there a parachute in that clip?

.


likestojump  (D License)

Sep 28, 2012, 9:43 AM
Post #8 of 24 (3746 views)
Shortcut
Re: [Skydivesg] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
In reply to:
Typical skydiving round canopies of the late 60's and early 70's had a sleeve, which added a LOT of bulk, and many were of a more complex design then the reserve and were bulkier for that reason.
_________________________________________________


I can't resist! http://www.youtube.com/watch?v=RH9kaxWQjfA

Good one........ oh... was there a parachute in that clip?

.

I believe it's a Security Crossbow piggyback :)


shibu  (C 42074)

Sep 29, 2012, 4:25 AM
Post #9 of 24 (3689 views)
Shortcut
Re: [ctrph8] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
Chest mount reserves can be smaller but can also be as big or bigger. There really isn't much to a chest mounted reserve container. It is 4 flaps, a deployment system which might or might not have a pilot chute, a canopy and some risers. They are not trying to make it comfortable or flat against your back. A back style parachute also has the harness, a cutaway system, the deployment system, padding (maybe) and is usually meant to be wide and flat for comfort. There is a lot of other stuff in there besides canopy which makes it look big as compared to a chest mount.


In reply to:
Just curious why the front mounted reserve parachutes appear to be so much smaller than the mains. I understand why the mains are so big now that I have seen them packed (on video) but how can the reserve fit into such a small package? Are they just smaller?

Never thought of that. Thanks.


shibu  (C 42074)

Sep 29, 2012, 4:26 AM
Post #10 of 24 (3688 views)
Shortcut
Re: [airtwardo] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
There is/was also a sleeve or bag on the main which increased the volume considerably.

The heavy cotton sleeve on my Pap was as big 'pack volume wise' as the canopy it held...

Never would have guessed that the sleeve added so much bulk.

Thanks Airtwardo.... but what... no sarcasm in this post?


shibu  (C 42074)

Sep 29, 2012, 4:28 AM
Post #11 of 24 (3687 views)
Shortcut
Re: [pchapman] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
In reply to:
Just curious why the front mounted reserve parachutes appear to be so much smaller than the mains.

Typical skydiving round canopies of the late 60's and early 70's had a sleeve, which added a LOT of bulk, and many were of a more complex design then the reserve and were bulkier for that reason.

In the era before custom civilian rigs, military bailout rigs were often converted for skydiving use.

So the military backpack might have, for example, contained a 26' Navy conical, and was relatively thin. The canopy was exactly the same as might have been used in a civilian jumper's belly reserve. So the canopy bulk would be the same, although what it would "appear" to be would depend on whether you thought the spread out but thin backpack seemed "bigger" than a lumpy belly mount or the reverse.

But for the civilian skydiver putting a ParaCommander or similar canopy in the backpack, the sides would be extended a few inches with sewn-in additions, to fit the bulk of the canopy & sleeve. (Rigs that were made for civilians later, could of course be sewn the right size from the start.)

The ParaCommander has something like 24 different holes and slots in it, which means a lot of extra tapes supporting the edges of holes. I'm not sure, but I'm guessing that added a fair bit to the bulk.

But the big thing is the sleeve. That's a heavy cotton "sock" that slides over the canopy from end to end -- so it is going to be 12 ft long or so. Instead of folding the canopy and then putting it into a bag as we now do, the canopy went in, then it was folded. To prevent nylon on nylon burns, the sleeve was cotton, and usually quite heavy.

Have you ever seen one of the big, baggy, cotton freefly jumpsuits from the early days of the discipline, say the mid 1990s? Stuff that in your rig, and that's roughly how bulky a sleeve is.

Reserves were much simpler in design, maybe with 3 open vents or meshed panels at the back for forward speed. And they didn't use a sleeve to slow the deployment. (Later ones would use a diaper that just wrapped the mouth of the round canopy until the lines were stretched out.)

Another factor is that the main container had to be sized for quick packing in the field, while the reserve container could be super tight with the rigger sweating over it for a while!

Old timers will know more, but I think that is a reasonable explanation why the "typical" skydiving rig with a belly mount reserve seemed to have so much bigger a main container.

Never realized how much went into the rounds. I guess I always thought of them as relatively simple systems compared to ram airs.


shibu  (C 42074)

Sep 29, 2012, 4:29 AM
Post #12 of 24 (3686 views)
Shortcut
Re: [HHypoxic] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
Typical skydiving round canopies of the late 60's and early 70's had a sleeve, which added a LOT of bulk, and many were of a more complex design then the reserve and were bulkier for that reason.
_________________________________________________


I can't resist! http://www.youtube.com/watch?v=RH9kaxWQjfA


Now I want to jump a round. Cool


airtwardo  (D License)

Sep 29, 2012, 4:54 AM
Post #13 of 24 (3683 views)
Shortcut
Re: [shibu] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
In reply to:
There is/was also a sleeve or bag on the main which increased the volume considerably.

The heavy cotton sleeve on my Pap was as big 'pack volume wise' as the canopy it held...

Never would have guessed that the sleeve added so much bulk.

Thanks Airtwardo.... but what... no sarcasm in this post?

Who ME...sarcastic?? NEVER! Sly


erdnarob  (D 364)

Sep 30, 2012, 12:57 PM
Post #14 of 24 (3614 views)
Shortcut
Re: [shibu] Round Parachute Reserve Question [In reply to] Can't Post

I have jumped a StratoCloud in 1976 or 1977. The parachute(with lines) weight was 17 pounds. Now, the same size of parachute weight is about 8 pounds. The miracle was that the manufacturers got a better knowledge of the parachute and parachute components and have been reinforcing them only at the right places. They also are using now better and lighter fabric which were not available years ago. I suggest you to have a look at PORCHER fabric manufacturer's web site. They have a video showing the complexity of fabric manufacturing. PORCHER is the manufacturer of fabric for Hot Air Balloon, paraglider, parachute, powered parachute ...etc. Porcher is one of the most important manufacturer in the world for that kind of fabric. There is a good chance that the fabric of your parachute is made by them. Reserves on the other hand were army or navy surplus and built way smaller than the main. I started jumping a paratrooper T-10 of 35 feet nominal diameter while my reserve (mounted on belly) was a 24 feet. Quite a difference. But we didn't have anything else at the time.Blush


erdnarob  (D 364)

Sep 30, 2012, 1:00 PM
Post #15 of 24 (3613 views)
Shortcut
Re: [airtwardo] Round Parachute Reserve Question [In reply to] Can't Post

I forgot to mention the bulk of the sleeve and the tubular 550 lines with 7 stands inside. Plus the sleeve retainer line, the tubular bridle and bulky connector links as well.Unsure


shibu  (C 42074)

Oct 1, 2012, 10:53 AM
Post #16 of 24 (3557 views)
Shortcut
Re: [erdnarob] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
I have jumped a StratoCloud in 1976 or 1977. The parachute(with lines) weight was 17 pounds. Now, the same size of parachute weight is about 8 pounds. The miracle was that the manufacturers got a better knowledge of the parachute and parachute components and have been reinforcing them only at the right places. They also are using now better and lighter fabric which were not available years ago. I suggest you to have a look at PORCHER fabric manufacturer's web site. They have a video showing the complexity of fabric manufacturing. PORCHER is the manufacturer of fabric for Hot Air Balloon, paraglider, parachute, powered parachute ...etc. Porcher is one of the most important manufacturer in the world for that kind of fabric. There is a good chance that the fabric of your parachute is made by them. Reserves on the other hand were army or navy surplus and built way smaller than the main. I started jumping a paratrooper T-10 of 35 feet nominal diameter while my reserve (mounted on belly) was a 24 feet. Quite a difference. But we didn't have anything else at the time.Blush

I forgot to mention the bulk of the sleeve and the tubular 550 lines with 7 stands inside. Plus the sleeve retainer line, the tubular bridle and bulky connector links as well.

Well that explains it.

24 feet nominal diameter? What is that a measure of? The diameter of the bottom of the round when inflated? I thought they were much bigger.


mark  (D 6108)

Oct 1, 2012, 12:13 PM
Post #17 of 24 (3531 views)
Shortcut
Re: [shibu] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
24 feet nominal diameter? What is that a measure of? The diameter of the bottom of the round when inflated? I thought they were much bigger.

It's 24' diameter if you laid it out flat. Projected/open diameter is less. OTOH, the original intent was to be in addition to, not instead of, the main.

Mark


pchapman  (D 1014)

Oct 1, 2012, 2:18 PM
Post #18 of 24 (3511 views)
Shortcut
Re: [shibu] Round Parachute Reserve Question [In reply to] Can't Post

Erdnarob mentioned the great weight of early square mains. The same applied to some of the rounds. For the popular ParaCommander, there were various ways to lighten it. One guide to ParaCommanders gave you ways to reduce the weight of the canopy about 5 lbs, by shortening lines, removing some heavy tapes, etc.

If you did that today with a main, you might be staring at a set of links...


Periapt  (D 3017)

Oct 3, 2012, 10:23 PM
Post #19 of 24 (3407 views)
Shortcut
Re: [likestojump] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
In reply to:
In reply to:
Typical skydiving round canopies of the late 60's and early 70's had a sleeve, which added a LOT of bulk, and many were of a more complex design then the reserve and were bulkier for that reason.
_________________________________________________


I can't resist! http://www.youtube.com/watch?v=RH9kaxWQjfA

Good one........ oh... was there a parachute in that clip?

.

I believe it's a Security Crossbow piggyback :)

With a flat circular canopy and a T-U cut in it, or possibly it's a LoPo manufactured with the mod.

Nice demo of packing a round, but I guess they don't make packers like they used to...(Sigh!)


Sincy78  (D 7363)

Oct 4, 2012, 8:21 AM
Post #20 of 24 (3344 views)
Shortcut
Re: [mark] Round Parachute Reserve Question [In reply to] Can't Post

24' is a reference diameter. If you measured the total area of a gore, including cut-outs (vent etc.) and then multiplied that area by the number of gores, it gives you a reference area. The diameter of a round parachute is the theoretical diameter of a circle that has the reference area calculated. You cannot measure a conical parachute by laying it out flat, because by definition it is a cone, and will not lay flat. If anyone is interested in more details on this and many more subjects on parachute design, I'll post a link to a downloadable version of the 1978 Air Force Handbook. It's a big file though.


ripcord4  (D 2238)

Oct 4, 2012, 9:34 AM
Post #21 of 24 (3334 views)
Shortcut
Re: [Sincy78] Round Parachute Reserve Question [In reply to] Can't Post

I'd be interested in that USAF link...thanks!


pchapman  (D 1014)

Oct 4, 2012, 11:43 AM
Post #22 of 24 (3318 views)
Shortcut
Re: [ripcord4] Round Parachute Reserve Question [In reply to] Can't Post

I bet it is the "Recovery Systems Design Guide" from the then Irvin company, for the Air Force.
Google AFFDL-TR-78-151


Sincy78  (D 7363)

Oct 4, 2012, 4:45 PM
Post #23 of 24 (3283 views)
Shortcut
Re: [pchapman] Round Parachute Reserve Question [In reply to] Can't Post

You're correct, to save you from searching here's where a copy can be downloaded.
http://www.airborne-sys.com/pages/view/publications
It's the bottom publication, it is a big file and takes a while to download so be patient.


riggerrob  (D 14840)

Oct 7, 2012, 9:51 AM
Post #24 of 24 (3145 views)
Shortcut
Re: [shibu] Round Parachute Reserve Question [In reply to] Can't Post

In reply to:
... 24 feet nominal diameter? What is that a measure of? The diameter of the bottom of the round when inflated? I thought they were much bigger.

.........................................................................

There are several different methods for measuring round canopies.
When measuring a 24 foot flat (e.g. T-10R: popular reserve for military static-line paratroopers), you simply lay a tape measure along a radial seam (from the center to the periphery/skirt/circumference.

If you want to know how many square feet of fabric, multiply the diameter (squared) by 3.142.

That method also works on the USAF 28 foot diameter, C-9 canopy found in many military-surplus pilot emergency parachutes.

HOWEVER, that method only works on canopies that can be laid flat on the floor.

All more recently-designed round canopies are some variation on conical. Conical canopies started with a flat, circualr canopy missing a few gores ... Then they started building more complex cones (e.g. tri-conical, curved aero-conicals, etc.).
For example, the popular US Navy 26 foot conical started with a 26 foot diameter (measured along a radial seam) flat circular canopy missing four gores. A USN 26' conical cannot be laid flat, but it opens better, packs smaller. swings less, etc.
Most civilian 26' LOPO canopies (Guardian, NAA, Pioneer, Security, Strong, and the early National 2' Lopos) are minor variations on the old USN pattern.

To compare conical canopies, you need some other measurement method.
For example, to compare fabric areas, measure the radius (along a radial seam), then measure the gore width, multiply to find the area of each gore, than multiple by the number of gores to find the total fabric area of the canopy (e.g. National Aerostar round reserve).

The challenge is that round canopy manufacturers never agreed on one method for measuring canopies, with some measuring fabric area, some measuring projected diameter, some measuring inflated diameter, etc.
The heighth of foolishness is calling a windsock a "16 foot diameter round canopy!"
Hah!
Hah!



Forums : Skydiving : Gear and Rigging

 


Search for (options)