60cm (24″) Water Rocket Parachute

Now that the nosecone is built it is time to make a parachute. One of the things I am quickly liking in this hobby is that you build just about everything yourself from scratch. This is something Im not used to in IT where just about everything is off the shelf.

I decided after doing some research that a ripstop nylon parachute was the way to go. Using this material increases longevity and with water rockets I don’t need to be concerned about it being melted by an ejection charge. I also decided on a 60cm diameter chute, this would be big enough for the next few generations of wrockets then for sustainers when I get to two stage designs.

The ripstop nylon I purchased from Spotlight. This is one of the big material supply type stores in Australia, but you will be able to find it in any good/large material shop. I did look for about 15 minutes through all the rolls of material but gave up and went and asked one of the lovely shop assistants who took me straight too it. BTW the shop assistants were very helpful so don’t be afraid to ask. I decided on luminous yellow, (I have read since that darker colours are better .. oh well we will see how visible it is) and it came in a 1.43m wide length, I purchased 1m (1.0 x 1.43) for about $8 and some 25mm red (1″) binding for $2.50.

I got two pens and tied them 30cm apart then used them to draw a pretty good circle. I used some trusty cans of tomatoes to hold the material tight.

31cm radius circle on the ripstop nylon

31cm radius circle on the ripstop nylon

I then used the tip of a soldering iron to cut out the ripstop nylon. I used this method as it melts or seals the nylon, when you cut it with scissors it tends to fray. The cutting / melting went OK, I was too worried about melting the tablecloth.

Cutting the ripstop nylon with the soldering iron

Cutting the ripstop nylon with the soldering iron

I then measured using a can of beans and cut out the centre hold. I wanted the centre hole to ensure that the parachute worked to slow the descent, but not too well that it carries the wrocket into the trees.

Measuring the centre hole

Measuring the centre hole

Here is the nylon cut out, the centre hole has a radius of about 4cm (1 3/4″). The centre is pretty much in the middle, just the angle I took the shot at makes it look off centre

cut out nylon showing dimensions

cut out nylon showing dimensions

Next step was to mark the positions for the 8 tie lines. To do this, fold it in half, then half again, then half again. Each time press down to make a crease in the nylon and when you unfold it you will have the exact locations, I marked these spots around the circumference.

Tie line locations marked

Tie line locations marked

Next I sewed the hem of the parachute over about 0.75cm, this was just to strengthen the nylon at the tie locations. I hand sewed it first, this took about 2 hours, (ok so my sewing is not the best but the backstitch from my high school home economics days did come in useful … )

Hemmed edges with red

Hemmed edges with red

The shot above also shows the yellow better (it is very bright).  After my 2 hours of hand sewing I decided that the sewing machine would be faster to master than hand sewing on the tie location binding pieces, so my wife set it up for me and off I went. I decided to do another stitch around the edge. I used (for those interested) a double stitch on the machine, it basically sews the stitch twice. I then went about sewing a 4cm piece of binding (4.0cm x 2.5cm) over the locations where the tie lines would be located.

Its not easy to sew and take pictures :)

Its not easy to sew and take pictures :)

Do this for the 8 locations over the top of the places you marked above and you get the photo below. I did also sew around the inner circle, whether this was needed or not I dont know, but I had the machine out and was feeling confident :)

Parachute with bindings and eyelet holes

Parachute with bindings and eyelet holes

The sewing machine has some cool (I don’t believe I just said that) stitches to do eyelets, so I used a 5mm hole  with a 7mm hole around it. Straight through the middle of the binding. This gives the hole the tie line goes through extra reinforcement. You could also use small metal eyelets for this.

close up of binding and eyelet for tie line attachment

close up of binding and eyelet for tie line attachment

To get a nice even hole and to seal the nylon I got out my trusty soldering iron again and used it to poke approx a 4mm hole straight through the middle of the eyelet. This method worked very well and left me with neat holes in the binding and nylon underneath. Be careful don’t touch the rest of the parachute it melts very easily.

binding with neat hole for tie line

binding with neat hole for tie line

Next I measured the tie lines and cut them. I cut 4 lines; each was 2.2 x diameter of the parachute, in my case 1.32m (52″). I tied them through the eyelet then to the opposite eyelet so that each line made up 2 tie lines. When all four where done I gathered the lines in the middle and tied them off so that they made a nice loop.

Parachute with tie lines

Parachute with tie lines

Next I needed a shock cord for the parachute. This absorbs some of the force on the line (and hopefully stopping it form breaking) while the parachute is opening. I used some elastic that I found (pinched) from the sewing kit. This piece was probably 25cm (10″) long but stretched out to 55cm (21″) at full stretch so it should be ok. I folded the ends over and sewed across them to make a nice loop in the ends. Again my sewing is not the prettiest but it is strong at both ends.

Elastic with ends turned over and sewed

Elastic with ends turned over and sewed

Again I used the double stitch. Next I added a loop of tie line through the eye of the elastic and a keyring ring through the other (I didnt have 2 keyring rings .. I will replace the tieline loop with a keyring ring) to attach it to the rest of the parachute. Here is a pic of it assembled. Its 105cm (41″) from the top of the parachute to the rocket attachment ring.

Finished Parachute

Finished Parachute

Here is a pic of the rocket attachment ring on the end of the parachute, attached to the line from the rocket. The line uses a barrel swivel with a snap lock (from any good fishing tackle store). This hopefully will let the rocket spin without tangling the tie lines and it also makes it easy to attach and detach the parachute (I saw this idea on another website …. very clever).

Attachment point to the rocket

Attachment point to the rocket

I will probably need a second attachment line to the rocket in case one breaks. I did a few indoor tests and it was opening and filling out fine. I also attached my 1 bottle rocket and threw it off the back balcony (its about 5m to the ground .. good test facility) and it was opening from being fully packed just before hitting the ground. When I tested it with the tielines already out it opened in about 2m and flew to the ground nicely.

Testing

Testing

Here is a pic of it folded up in the rocket nosecone

Parachute inside nosecone

Parachute inside nosecone

and lastly a video of it being thrown out of the nosecone using the timer and the door. I previously had some sponge behind the deployment plate however the nosecone was deforming when the door was shut which stopped the timer, so I took out the extra sponge, it fitted better and the timer worked again. Here is a video of the parachute being pushed out of the nosecone.

Only thing left to do now is build the new wrocket based on the 1.25L bottles, attach the nosecone and give it a proper test.

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This entry was posted on Monday, August 18th, 2008 at 8:34 am and is filed under Development. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

 
 

3 Responses to “60cm (24″) Water Rocket Parachute”

  1. ishra 123567gre Says:

    i like it

  2. scuffed bumper Says:

    scuffed bumper…

    […]HHWRSA » Blog Archive » 60cm (24″) Water Rocket Parachute[…]…

  3. Joe Says:

    Excellent posting. Thanks for taking the time to show the closeup photos. I like the sewing part. Looks like I’m going to learn some new skills. Did you use a Tomy timer? Where can I find them?
    Thanks.
    Joe.