There are a number of things a rocket builder can do to insure reliable recovery operation.  As we all know, there is no foolproof method to this part of a rocket’s journey.  I suspect you already practice a few of these methods and the rest are here to help with other problems that you might not have discovered yet.

What Size Do I Need?

One of the most common problems for scratch builders is deciding what size the parachute should be for what they have built. The decision should be made taking several things into account.

How much does the rocket weigh?  This will be the first consideration.  There are many programs and charts to help you pick a chute size based on weight.  You could even compare your rocket's weight to that of some of the popular kit rockets and make a guess based on what gets sent with kit rockets.  A word of caution though, as most kits come with a parachute you will wish was one size larger.  Keep that in mind.

What do you plan to land the rocket on?  Grass can absorb a lot of energy compared to the packed dirt on a dry playa.  You may want to choose a parachute one or two sizes larger for hard landing sites.

Overall construction and design can influence you decision as well.  If you have built one really tough rocket and you don’t want to chase it 2 miles, well, put a smaller chute on it.  You can bring down a 12 lb. rocket on a 60” chute if it is built tough.  Short rockets tend to take rough landings better than long rockets, too.

A final word on this subject:  There is NO substitute for the opinions of other members in your club who fly high power rockets at the same location as you do.  Their guidance is worth more than any chart or program I could post on this site.  If you don't have immediate access to a knowledgeable club, or an online chat group, e-mail me for an opinion.  rage@rocketrage.com

Canopy Design

There are many canopy designs to choose from and several factors will influence you decision on which is right for your rocket.  The most common parachute design is a flat sheet circular or octagonal shape.  These chutes are popular because they are usually less expensive than other designs.  They are much easier to make since there are no seams in the fabric.  Many kits include parachutes of this style, however, I often find that the attachment of the cords is less than adequate.

The “X” form parachutes are made from 5 squares or two long rectangles of fabric but do not offer near the economy in terms of CD to weight ratio.  Some people like the looks of an X form parachute in flight.  I would only recommend these for people who want to try to make their own parachute and need a simple design.  The diameter of an X form will often be 40% larger than it’s circular counterpart to carry the same load.

The most economical parachute in terms of CD to weight ratio is the semi-ellipsoidal.  This parachute is shaped like the top of a squashed ball or the upper half of an oval.  It offers the best for those looking for a way to cut some weight and not compromise performance.  These parachutes often have 12 or more panels.  You won’t find many of these offered in the current market because of the labor needed to assemble them. And the only improvement you can make over that is what we have done to the Quantum chutes.

The hemispherical parachute offers very good CD and is also a good choice for performance.  There are only a few suppliers for this design.

There are a number of other designs that are geared more towards indestructibility rather than economy.  These parachutes often have significantly more weight but are much more forgiving of those bad estimates on delay choice or unusual flight patterns.  Three or four heavy tubular straps or paracord sewn all the way over the canopy replace the traditional six to twelve shroud lines. When electronics were hard to find and too expensive for the average rocket freak these made more sense.  Now our rockets are smarter...and so are our recovery systems.

Whatever canopy design you choose, the length of the shroud lines of any chute should be between 1 and 2.5 times the diameter of the canopy.  The longer cords allow the canopy to open just a little more for improved CD.  Some cordage is heavy and may justify getting a larger canopy instead of longer cords.

Construction Quality

The quality of your chute is in the seams and the attachment of the cordage.  On a good quality chute the only thing that can fail is the fabric.  A parachute with a blown panel can still bring your rocket back in good condition.  If your chute looses more than one shroud line, you will be doing some repairs.  Check over the seams and look very closely at the shroud line attachment.  If it looks like your shroud lines are held on with a few threads that happen to hit the cord as the machine passed over, you have a chute that will allow for no errors.  No, you can't epoxy them on better.  You can add some sewing to reinforce the attachment.  It doesn't require a rocket scientist to do a better job.   Next time, buy a better chute.  Kit chutes are often "from the lowest bidder" as they say.

Balance the Parachute

Before you fly the chute make sure it is balanced.  First, measure the lines to make sure that each one is just about exactly the same length from the edge of the canopy to the attachment point at the bottom.  Your chute should be balanced to keep it from spilling out one side more than the other.  If it does, it will chase it’s self around in a circle instead of flying smoothly, or it will thrust in one direction causing more lateral travel than what you were planning.  On a parachute of 36” or less you should have less than 1” difference.  If the cords are a little stretchy, it will be a little more forgiving.

If a cord is too long, tie off a small loop to make it the same length as the others.  Tape or put shrink tube over the knot so it can’t snag on anything.

If a cord is too short, well, you have a problem there and I don’t know of any good fixes for that except replacing the line or sending the chute back to the manufacturer.

Another way to balance the chute is to line up all the cords at the edge of the canopy and the pull the cords tight at the attachment end and tie them all together in knot leaving a small loop at the bottom for attachment.  Make sure the knot is tight and nothing can snag on it.  Again, if you have some large shrink tube, this is a great place to use it.

Now your chute is ready to fly.

Put baby powder in the airframe where you plan for the chute to slide out.  Baby powder is the best “cheap” dry lubricant you can get.  Be generous.

Fold Your Chute

There are several right ways to fold or roll a parachute.  Your particular situation will determine which is right for each rocket.  I would recommend that you lay the chute down and fold it over three or four times until you have a pie slice shape.  Then place the cords folded over once on the chute with 4” hanging over the edge of the canopy.  Then “Z” fold the canopy three or four times.  Finish by rolling the wad in either direction so it fits the space you plan to put it in.  Most importantly, experiment with several folds until you feel comfortable with your pack.

What Am I Trying To Do?

You want the parachute to slide out of the airframe, unfold, and open as gradually as possible.  This will prevent stressing whatever the weakest link in the chain happens to be.  Chutes that snap open transfer a lot of energy directly to the attachment points through the whole recovery system.  Avoid that if you can.  The desirable sequence would be like this:

The chute is pushed or pulled out by the ejection charge.

The cords extend to full length as the canopy starts to unfold.

Finally, the canopy inflates gently.

You want the cords at full length before the canopy has a chance to inflate to prevent inversion or tangling.

If your chute has a spill hole I would recommend sewing in some netting to cover the hole.  Any netting will do.  The object here is simple.  After you see a nose cone bounce back and shoot through the spill hole you’ll change your mind about the value of the spill hole.

Don’t let that happen to you.

What Is The Big Deal About A Spill Hole?

The spill hole serves to even out the flow of air spilling out around the edge of the canopy.  If the lines on your chute are not all the same lengths, this will make up for some of the difference.  If your chute is balanced properly, there is no need for a spill hole.  Chutes that quiver, wobble, or oscillate are not properly balanced or are carrying a load greater than what the design will permit.  You may notice that some chutes open and close slightly on the way down.  This is normal.  It has to do with the relationship between the size of the chute and the weight it is carrying.  The parachute is inflating and then puffing out the excess air as it descends.  This is not a compromise of performance.  If you don’t like it get the next size larger parachute.

Things to Watch Out For

Check over every part of your recovery system.  One of the most common problems I see is a shroud line getting caught on something.  Make sure that you have taped or put shrink tube over all knots and don’t let any loose ends hang out.  Make sure that your hardware won’t be a source of a snag.  Check over your airframe, fins, launch lugs, and motor retention system.  Look for anything that could be a source of snagging.  A high-speed deployment can send your parachute and cords sliding back over your airframe and fins.  If you are using wood fins make sure that the edges are sealed with epoxy.  The cordage will peel that plywood like a banana at anything over 50 mph.

Always inspect each part of your recovery system before each flight.  Look over the parachute for tears or shroud lines that are coming loose.  Have your parachute repaired by someone who is qualified to do this kind of work.  If you think your sewing skills are up to it, give it a shot.  Use polyester or nylon thread.

Don’t put epoxy on it.

Protect that Parachute

Be sure to give you chute adequate protection from the ejection charge.  Adding baffles, a deployment bag, a piston, wadding, or a Nomex cloth can do this.  If you do use something disposable, make sure it is environmentally friendly.  I use the starch based packing peanuts for my 3” and larger airframes.

Keep your eyes on the market.  There are a number of new products under development that will make traditional recovery rather boring.

Be safe.

Test it on the ground.

Thanks