Spill Holes

 The Thrifty Rocketeer blog continues...

Now, it seems that a tempest in a teapot has erupted recently over the topic of spill holes in parachutes.

Frankly, I'm not all that conversant with the topic, so I've been following the discussion casually, but a couple of the more recent bends in the more heated discussion have caught my attention.

Now, it's my understanding that parachutes operate by catching the air and inflating, resisting the spill of air over the edges, to slow the descent of the payload....whether that's a man, an elephant, a package, or a model rocket.

And if you want to accelerate the downward rate, a hole can be opened in the chute to increase the rate of air being spilled out of the canopy.  Usually, this is at a controlled rate, when this is a paratrooper or skilled parachutist coming down.

But I understand that model rocketeers may set the rate (or approximate it) to avoid chutes being caught in an updraft thermal, or prevent extreme drifting due to a crosswind.

I have only ever seen someone cut a moderately large circle in the center of the chute, making a permanent hole in a plastic mylar chute.  But I have heard of higher power rocketeers maintaining a nylon chute with a permanent hole in their kit bag to switch out on windy days, or when they want to bring it down in a smaller field.

But recently, someone spoke up that they have installed an array of spill holes (not large, but about 8) in a regular pattern in the plastic chute.  They claim that it works just fine, and that the holes are sufficient to perform the same function as a single large hole.

Their only difference is that they have utilized colored ring binders reinforcement rings to line each hole they have punched.  The color serves no useful purpose that I know of, but does draw attention to the fact that the canopy is perforated.

The photo of this sparked quite a little debate among rocketeers who insist that the original poster must have meant reinforcement rings for shroud lines, and not spill holes.  No, the original poster was quite adamant that he meant what he said.

I don't have a dog in this fight, as I have only ever seen reinforcement rings used on shroud lines for a plastic chute....and I've even laid in a box of extra rings to patch or reinforce those plastic chutes that I have made, as replacements for a melted chute (mores the pity!)

It would seem to me that the more holes punched in a canopy, the greater the risk of a rip or catastrophic error.... Hence, the use of reinforcement rings. But it also seems to me that the number of holes will sum the amount of air escaping and perform a similar function... although perhaps slower.  I really don't know.

One poster claims that this perforated chute technique is not new, but an old one that was shared back in the day via rocketry magazines or newsletters.  But I don't know.

Do you?

Have you ever used this method to bring your rockets down faster? Does it work?

The Thrifty Rocketeer wants to know...