Coldfire Recovery System

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Click on any photo below to see a larger image of it.

Kevlar cloth is used to protect the Coldfire recovery system from the heat and flame produced by the black powder ejection charges. Various shapes were cut from a bolt of 8 oz cloth. The cloth is from Thermostatic Industries, Inc. Their part number for it is 8K-60. It was $100 for 3 yards x 60 inches (45 sq ft). To cut Kevlar cloth I use some special shears that look like scissors. They are available from CST for $17.95. (Part number E814.) They work really well!

This photo shows how I used a metal pin, a string and a Sharpie pen to mark the cloth in a large circle.

Three different shaped pieces are used in Coldfire. The large rectangular piece is for protecting the parachute. The large circular piece is for protecting the tubular nylon harness. The small rectangular piece with the corners cut off is used to over wrap the ejection charge holders. It takes the brunt of the blast from the ejection charges and makes the other two protectors last longer (more flights). The small piece doesn't last as many flights but is more easily replaced.

The outside edges of all of the heat shields were sewn with an overcastting stitch that prevents the raw edge of the cloth from fraying. This is done with Kevlar thread from McMaster-Carr. The part number was 8800K81. It is trade size 69, 0.014" diameter, 375 yard/spool for $13.50.

Tubular Kevlar webbing 1/2" wide is available from Giant Leap Rocketry for about $1.25 per foot. This is used as the "anchor" for the recovery harness. It does not require any additional protection from the heat and flame of the ejection charge. It connects to the U-bolt on the altimeter bay right next to where the ejection charges are mounted.

A water knot is tied into each end of the tubular Kevlar. Step 1 is shown here.

Step 2.

Step 3 just involves pulling it all snug.

Some West System epoxy will be brushed onto the loose ends to keep the tubular Kevlar from fraying. Once the epoxy has cured those ends can be squared-up by cutting right through the epoxy section.

Coldfire uses 1" wide tubular nylon (TN) for the main parachute harnesses. (Or what is sometimes called the "shock cord".) It can be obtained at places like REI Inc.

Just like the tubular Kevlar a water knot is tied into each end of the TN as shown here. The photo shows the knot just before it should be pulled snug. No epoxy is needed to prevent the free end from fraying. The free end can be simply melted shut with the heat from a stick match.

Three triangular shaped quick links are used to connect various elements of the recovery harness to the parachute and to the U-bolts in Coldfire. One of the quick links is shown here as compared to a US quarter. They are 3/16" material diameter made from type 316 stainless steel (part number 3709T32) from McMaster-Carr.

The parachute selected for Coldfire is a 72" TAC-1 available from Giant Leap Rocketry. This chute will support 15 lbs at 17 fps and it weighs 18 oz.

This parachute comes with a swivel attached. I cut it off and don't use it. I personally prefer to eliminate the swivel in order to eliminate any possibility it might fail (come apart.) I have not seen any issues with lines getting tangled without the swivel. It seems like an unnecessary risk to me.

The photo above shows all of the Coldfire recovery "laundry" connected together and laid out on a table. The TAC-1 parachute is the blue item. When it is packed for flight the chute will get wrapped "burrito" style in the square piece of yellow Kevlar cloth. The red material is the 1" wide tubular nylon (TN). Coldfire uses about 25 feet of it. The TN is protected by a 30" length of Kevlar protector sleeve available from Giant Leap Rocketry. The protector sleeve spans the open section between the chute in the square piece of Kevlar cloth and the TN in the circular piece of Kelvar cloth. The TN connects to the 1/2" wide tubular Kevlar anchor strap. The anchor strap passes through a small slot in the circular flame shield.

Three triangular quick links can be spotted in the photo above if you look closely. (Click on the image to see a larger size.) One quick link connects the parachute to the TN. This same one is also used to connect to the U-bolt on the booster section . A second quick link connects the TN to the Kevlar anchor strap. The third one is used to connect the other end of the Kevlar anchor strap to the U-bolt on the altimeter bay where the ejection charges are mounted.