Why do Tandems have 9-Cell reserves?

[nigelh 0]

Quick question,
Tried Google and searching here first but nothing came up.

Does anyone know why Tandem reserves are 9 cell and not 7 cell?

Looking for genuine answers, not "I think....." ;-)

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Team Dirty Sanchez #232

[LeeroyJenkins 2]

Distributes the shock more on opening.

[ChrisHoward 8]

9 cells support the weight better than 7 cell canopies of the same size (due to increased structure) giving them better flight performance and flare power.
Also a number of popular tandem reserves were at one point a tandem main before being designated as only a reserve.

[justme12001 0]

Also not all sport reserves are 7 cell (or didn't use to be, not sure about now). I know of at least one reserve that is a 9 cell. The Falcon could be used as a main or a reserve.

[riggerrob 598]

Tandem reserves have 9 cells because they are so big, but fabric only comes in bolts 72” wide.
Also the higher aspect ratio (span / chord) improves glide and flare.
I am so old that I jumped jumped Pioneer Hi-Lifter 370, Parachutes de France Galaxy, PD 360, Strong 425, etc. when they were fashionable as mains. All those canopies were also available as tandem reserves.

[Westerly 61]

riggerrob

Also the higher aspect ratio (span / chord) improves glide and flare.

Sure, but at the cost of opening reliability which is not something you want to trade off in a reserve. I could be wrong, but it's been my understanding that opening reliability is linked to aspect ratio. The lower the aspect ratio, the more likely the canopy will open correctly, fly straight in line twists, ect (all other metrics like WL and size considered equal).

[riggerrob 598]

Westerly

***
Also the higher aspect ratio (span / chord) improves glide and flare.

Sure, but at the cost of opening reliability which is not something you want to trade off in a reserve. I could be wrong, but it's been my understanding that opening reliability is linked to aspect ratio. The lower the aspect ratio, the more likely the canopy will open correctly, fly straight in line twists, ect (all other metrics like WL and size considered equal).

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True!
Aspect ratio does affect opening reliability, but it is less of a problem on untapered canopies. The vast majority of civilian reserves are rectangular making them turn slower ......

During my 30 or so reserve rides, my worst nuisance was line twists.

The only time I opened a 5-cell reserve, it was so unstable in roll that I barely turned it enough to face into the wind. I only flared 3/4 and slid out the landing on the snow.

[fanya 3]

Because you eventually have to land them.

[skytribe 16]

Quote

Sure, but at the cost of opening reliability which is not something you want to trade off in a reserve. I could be wrong, but it's been my understanding that opening reliability is linked to aspect ratio. The lower the aspect ratio, the more likely the canopy will open correctly, fly straight in line twists, ect (all other metrics like WL and size considered equal)

But I still have to land with a passenger somewhere. And I'd rather have something that will improve my glide and flare for a good landing where I want to be than have a crappy landing in an unfamiliar landing place because I couldnt glide to the landing area.

The reserve ride openings I've had with a tandem have been pretty good. But then Again I do take my time packing the reserves.

[Westerly 61]

skytribe

Quote

Sure, but at the cost of opening reliability which is not something you want to trade off in a reserve. I could be wrong, but it's been my understanding that opening reliability is linked to aspect ratio. The lower the aspect ratio, the more likely the canopy will open correctly, fly straight in line twists, ect (all other metrics like WL and size considered equal)

But I still have to land with a passenger somewhere. And I'd rather have something that will improve my glide and flare for a good landing where I want to be than have a crappy landing in an unfamiliar landing place because I couldnt glide to the landing area.

Except that is not what the trade-off is. The trade-off is having good glide or good opening reliability. The goal of a reserve should be to get a good parachute over your head no matter what the cost or trade-off is.

[DougH 270]

How many tandem reserve openings have you had?

"The restraining order says you're only allowed to touch me in freefall"
=P

[ChrisD2.0 2]

Because it turned out to be more economical for the manufacturers to keep a unified design throughout the whole process from inception to this current day.

Brett Bickford Did Not Commit Suicide.

He is the victim of ignorance and faulty gear. AND as in the movie: "12 Angry Men," of an ignorant and callous jury.

[wolfriverjoe 1,445]

Westerly

Except that is not what the trade-off is. The trade-off is having good glide or good opening reliability. The goal of a reserve should be to get a good parachute over your head no matter what the cost or trade-off is.

Can you point to any issues with Tandem reserve reliability?

Can you show any incidents where a tandem reserve didn't open properly (when the TI executed EPs correctly)?

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

[billvon 2,675]

Quote

Tandem reserves have 9 cells because they are so big, but fabric only comes in bolts 72” wide.
Also the higher aspect ratio (span / chord) improves glide and flare.

It is also worth noting that some of the early Strong tandem canopies (the 520) were 11 cell, I believe.

[skydiverek 60]

wolfriverjoe

***
Except that is not what the trade-off is. The trade-off is having good glide or good opening reliability. The goal of a reserve should be to get a good parachute over your head no matter what the cost or trade-off is.

Can you point to any issues with Tandem reserve reliability?

Can you show any incidents where a tandem reserve didn't open properly (when the TI executed EPs correctly)?

Here is one:
https://www.youtube.com/watch?v=hg5EoCDwhnk


.

[Rover 9]

skydiverek

******
Except that is not what the trade-off is. The trade-off is having good glide or good opening reliability. The goal of a reserve should be to get a good parachute over your head no matter what the cost or trade-off is.

Can you point to any issues with Tandem reserve reliability?

Can you show any incidents where a tandem reserve didn't open properly (when the TI executed EPs correctly)?

Here is one:
https://www.youtube.com/watch?v=hg5EoCDwhnk


.



The recent tandem fatality in Queenstown New Zealand where the passenger drowned in a lake involved a malfunctioning reserve.

2 wrongs don't make a right - but 3 lefts do.

[riggerrob 598]

billvon

Quote

Tandem reserves have 9 cells because they are so big, but fabric only comes in bolts 72” wide.
Also the higher aspect ratio (span / chord) improves glide and flare.

It is also worth noting that some of the early Strong tandem canopies (the 520) were 11 cell, I believe.

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Yes.
I made a bunch of jumps on Strong 520 mains. They had 11 cells and were all made of F-111 fabric. The sad part is that their sliders looked the same size as 425s.
Only the very best packers could make them open softly and reliably.
I have suffered tension knots and torn a few Strong 520 canopies. One had a hole big enough to drive a bus through beside a hole only big enough to drive a van through! These holes were through both the bottom skin and top skin!