[rec.skydiving] slow openings

bchurch@oucsace.cs.OHIOU.EDU (Bob Church) (11/28/90)

I'm considering getting a new main sometime in the near future and
need some input on a possible problem. Canopies are getting larger
and larger. This can be very good, especially for those of us who
could stand to lose a few ( ok, a lot of ) pounds. However, what
about opening problems. Theoretically a larger canopy increases
the chances of a slow opening and snivels. I was wondering if those
of you who have gone to larger canopies have noticed problems. I'd 
like to find an optimum point between soft landings and clean 
openings.


Thanks,
bob church
bchurch.oucsace.cs.ohiou.edu

ryoder@en.ecn.purdue.edu (Robert W Yoder) (11/29/90)

In article <2638@oucsace.cs.OHIOU.EDU>, bchurch@oucsace.cs.OHIOU.EDU (Bob Church) writes:
> I'm considering getting a new main sometime in the near future and
> need some input on a possible problem. Canopies are getting larger
> and larger. This can be very good, especially for those of us who
> could stand to lose a few ( ok, a lot of ) pounds. However, what
> about opening problems. Theoretically a larger canopy increases
> the chances of a slow opening and snivels. I was wondering if those
> of you who have gone to larger canopies have noticed problems. I'd 
> like to find an optimum point between soft landings and clean 
> openings.

I disagree on the premise that larger canopies have inherently slower openings.
This may be true for round canopies, since the canopy slows its own opening,
but not for reefed ram-airs.

The opening speed of a square is a function of the inflation forces of the
canopy versus the retarding forces of the reefing system.
The opening characteristics of a ram-air canopy can be easily adjusted by
simply changing the dimensions or porosity of the slider.
If you change all of the linear dimensions of a canopy design by an identical
amount, you will have an identically proportioned canopy, which will have
an identical relationship between opening forces and reefing forces.

Even if you do find yourself with a canopy that opens too slowly, all you
need to do is vent the slider.  With F-111, this is frequently necessary as
the canopy aquires a lot of jumps.

-- 
Robert Yoder  306 Hawkins Graduate House, West Lafayette, IN 47906 (317)495-6845
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