Question about canopy construction

[ECVZZ 0]

What's the difference in construction and/or materials between a main, and a reserve? I know that a reserve has to be TSO'd, and a main doesn't, but aside from that?

Could a reserve be jumped as a main? If so, could one reasonably expect the same type of wear, at the same number of jumps as a comparable main (same material, etc...).

Just curious. These are the kind of thoughts on a bored field mechanics mind on those long drives between jobs.

Greg

[AndyMan 7]

Quote

What's the difference in construction and/or materials between a main, and a reserve? I know that a reserve has to be TSO'd, and a main doesn't, but aside from that?

1) Zero Perosity Fabric vs. F-111 (0-3 cubic feet per minute) fabric is the biggest difference.

2) Reserves are 7 cells while most mains are 9 cells.

3) Perfectly rectangular reservers while mains frequently have varying degrees of "taper" or "elpitical".

Can a reserve be used as a main? depends on the reserve, but generally yes. For years, the Raven was popular as both a main and reserve, but now is only used as a reserve.

A reserve being used as a main will age at the same rate as a F-111 main, which is faster then z-po. Reserves are sometimes used as mains for long after their worn out as reserves. Not common, but it is done.

The biggest problem with using a reserve as a main is that many of them don't have a bridle attachment point.

_Am

__

You put the fun in "funnel" - craichead.

[riggerrob 643]

Sewing techniques are the same for mains and reserves.
However (with the exception of Spectra suspension lines) reserve design hasn't changed significantly since the mid-1980s.
The only recent advance in reserve technology has been is span-wise bottom skin reinforcing. Oh, wait a minute, I saw span-wise bottom skin reinforcing tapes on a 19
By the mid-1980s they had worked all the bugs out of rectangular, 7-cell, medium aspect ratio, F-111 canopies. At that point they pretty much froze the design of reserves. Almost all reserves are still built of the same 0-3 cfm fabric used in the 1980s. Only Precision has tried building Raven -MZ reserves out of ZP fabric. Raven-MZs have not sold very well because only a few riggers have the patience to pack them.
A reserve would last the same number of jumps as an F-111 main: about 700.

[billvon 3,096]

A few notes:

>1) Zero Perosity Fabric vs. F-111 (0-3 cubic feet per minute) fabric is
> the biggest difference.

F-111 is a trade name that no one uses any more; it's become a term like 'xerox.' This comes up because the modern fabrics used in reserves (like ExactaChute) do not behave like F-111. This is why the old argument "Does F-111 rip like ZP?" is hard to answer accurately; no one uses F-111, and the type of fabric used is critical in answering that question.

>2) Reserves are 7 cells while most mains are 9 cells.

Several larger reserves are 9 cell.

>The biggest problem with using a reserve as a main is that many of
> them don't have a bridle attachment point.

Super Ravens continue to come with a bridle attachement standard, and PD demos reserves with bridle attachements. These are a great way to see how your reserve will fly - it's better to learn under ideal conditions than when you have to land your tiny reserve that you've never jumped before in a backyard.

[MrHixxx 0]

I just thought I would add this info PD gave me for an earlier post. The actual materials they speak of are Soarcoat (ZP) and Exactachute (F-111). I do not recommend ZP reserves for this reason... Packing should really not be that big an issue if you are using weights and clamps...

-Jon


Why don't we use ZP fabric in our reserves?

First, the tear strengths listed in the specs are very misleading, for
two reasons. The tear strength is measured at a specific tearing speed,
measured as a certain distance per unit of time. When you tear things
relatively slowly, the tear strengths are quite high. However, when you
increase the speed of the tearing motion, the actual forces required to
keep the tearing motion progressing actually go down. The tear spec is
measured at a standard 12 inches per minute, a rate at which the ZP
fabric looks superior to the standard fabric. However, this tear speed is
not very realistic compared to the way a canopy would really tear.

Because of this, we have created our own testing machinery that can
measure tear strengths at up to 150" per SECOND. When you measure the tear
strength at a high tearing speed more like what would happen in
reality, the tear strengths go way down, to the 3 to 7 pound range. The
standard fabric actually has a higher tear strength at these speeds than the
ZP fabric torn at the same speed.

So to cut it short, the tear strength of the ZP fabric is lower than
that for the F-111 style fabric when the tear speeds are up where things
would be in an actual failure mode.

When a ZP canopy fails, it is typically pretty catastrophic, with tears
going every which way in unusual patterns. On F-111 type canopies, the
damage is typically more localized.

Other reasons to not use the fabric? The benefit of ZP fabric is
partially the fact that is stays low porosity. If that is an issue on your
reserve, you are using it way too much. Another benefit is the presumed
aerodynamic advantage. In reality, the aerodynamic performance is due
to other aerodynamic issues such as better airfoils, aspect ratios,
trim, etc. These items aren't suitable for reserve designs, due to opening
issues. When you use good reserve aerodynamics, but throw the ZP fabric
in there, you don't really get an improvement in landing performance.
An example of this can be seen by comparing the ZP lightning crew canopy
to a ZP Spectre. The two canopies are designed to do separate things.
The Lightning lands well for a CRW canopy, but is relatively tricky to
land compared to the Spectre, even though both canopies have ZP fabric.