Replacement Chute build

 The Thrifty Rocketeer blog continues....

So, it started as I was driving into work and spotted a flash of red in the median of the divided highway.

I craned my neck as I went past, and recognized it as a red plastic flag laying among the green grass in the median.

A new Lumber yard/hardware store has opened just recently, and I had been seeing a number of these red flags along the highway as I drove past... apparently being blown off from an extended load out of a pick-up truck leaving from the adjacent lumber yard.  The increase in wind and velocity had either worked it free, or ripped it off the stapple.

After a week of seeing this laying in the median, I decided it was time to do something about it. I would stop.

It was the hottest day of the summer, with heat index over 100 on the day I decided to stop.  So I pulled into the median and made a quick dash for the flag. I got back in and made sure the A/C was on full as I pulled out in traffic. Yes, I was right, it was printed with the name of the lumberyard, and the stapple had pulled out. But the plastic was thicker than I had expected.

The idea started in the back of my mind that I could convert this square of tougher plastic sheet into a spare parachute for a rocket yet to be built.  But how to convert from square to hexagon?

There are some rocketeers who claim that it makes no difference whether the chute is square or hex, but I'm thinking Hex is best.

I also need some additional ring reinforcement adhesive circles, so I stopped at HL and bought a pack of 500.  While I was there, just for fun, I compared the price of a 12" and 16" chute replacement from Estes. They were 2.49 and 2.99 respectively and completely finished, strung, cut and ready to attach.  Pretty hard to beat that.

But I also needed some thread or shroud lines for mine, so I cruised past the clearance shelves and found a package of bead string wound around a card. There were four different colors of 50 yards each. The clearance price was a buck so I went for it.

Then I started thinking about how to layout the hexagon on the square of plastic.  Now, there are two caveats that I have to have.

First, the corner of the square where the stapple pulled out, must be eliminated...that is, cut off, when the hex is laid out. I  don't want a weak spot in the chute.  Second, I want the majority of the store name to remain, and for the finished hex to be as equal as I can make it.

The actual measurements of the red square is 16" x 14 3/8"... not quite square but close.

So, I started with the assumption that two vertices would be halfway along the 14 3/8" sides. Assuming that I'm going to be cutting a right angle triangle off the four corners of the square, that would mean each angle of the triangle will have a 90 in the corner, and either a 30 or a 60 degree angle in the rest of the triangle.  To measure this, I take the 16" size and divide in half, leaving me 8" on a side for the hexagon. I subtract half of that 8" from both the left and right side of the remaining side, and mark either end, about eight inches away from each other.

I used a black Sharpe marker to mark these vertices and draw the lines connecting those points that I will cut along with a pair of very sharp scissors stollen/ borrowed from my wife's sewing table.  Now, while you can carefully and slowly close the scissors to cut along these lines, there's also a great trick you can try.  You don't want to close the scissors completely before beginning the next cut, cause the start and stop of the cuts can produce a "notch" where you course-correct to stay on the line.  To solve this, by carefully closing the  pair of scissors carefully, you can find a sweet spot where the scissors form a cutting V edge. By sliding the scissor forward WITHOUT ANY ADJUSTMENT OR CLOSING THEM, you can make a running slice along the line if you are very, very careful. 

Another more simple way to make this slice, is to take an Exacto hobby knife and ON A CUTTING BOARD, lay a metal edge ruler along the marked line to cut, and drag the knife along the metal rule to slice the plastic.  This works better once you've practiced it AND 

ARE SURE YOU ARE NOT SCORING YOUR TABLE TOP BENEATH THE PLASTIC!

Once cut and free, toss the four right angles of scrap plastic in the trash. (Or save them to make a red flag to attach to the end of your launch rod as a safety feature.)

With the red plastic hex laid flat with no wrinkles, you're ready to apply the adhesive circles. Peeling them off their sheet one at a time, you'll want to press them in each of the six corners of the hexagon. Make certain each part of your adhesive circle is completely on the plastic.

 Burnish the circle down flat with a fingernail so they adhere well.

Next, take either a sharp pencil or a large sewing needle and pierce through the center of each of the six circles, breaking the plastic, and leaving a small hole. You'll be threading each of your shroud lines through this hole, so make it as clean as you can, and preferably close to the inside edge of the paper ring if you like.  Tie each end of a shroud line through the hole and back on itself with an overhand knot. Twice.

If you're using a large sewing needle keep it half inserted through the plastic as you thread the eye with your shroud line.

You'll want three shroud lines, approximately two feet long.  The easy way to do this is to hold a one foot ruler in one hand, and pinch the end of your thread or cord under your thumb. Run the line down the ruler, around the far end, and back on the back side.  As you reach the end you are pinching, you have just measured off two feet. (You can cut it off now, and do this a total of three times. Or...) continue winding the line down and back again two more complete loops.  You can cut the line off now that you've measured off six feet, and by careful insertion of the blade under the end next to your pinched thumb, you can slice through the two loops at two feet from each end.  Three 2-foot shroud lines should fall away from the ruler.

Now, this has assumed that you're going to tie each end of each shroud line to adjacent vertices of the hexagon.  But there are other ways to do this too.

You could tie one length of 2 foot shroud line to any vertex and to the next vertex, forming a loop (as above). But in this version, skip the next vertex and tie a loop between the next two vertices. You're left with two loops, separated by an unused vertex between each.  

Now, you're going to need slightly more than 2 feet of shroud line to complete this third loop, because you are tying two vertices that are farther apart than the first two loops. This is important because when all three loops are gathered together to be attached to either the nosecone or a swivel, you want them all to hang to the same point.

(The original plan, with all three loops tied to adjacent vertices eliminates this problem, except that there is no way to make them all lay flat without tangling. Trust me, I've tried.)  The 2-and-1 plan allows the lines to lay flat when folded, but requires that third longer loop. Trial and error is your friend here.

Now, as hinted at above,  you may want to tie your parachute directly to the nosecone (probably via either the metal screw-eye into a balsa nose cone, or through the small plastic circle on the end of the blown plastic nosecone).  Another option is to attach a swivel, and clip this to the nosecone.

There are several different styles of swivels available, but each has its merits. The bigger the swivel, the heavier and the more weight, the lower your rocket will fly.  So, I recommend you keep your swivel light weight.  One set of swivels come from fishing tackle with a re-closable hook or loop on one end. Most rocketeers will opt for this... but note that when closed, this style swivel has a pair of sharp prongs that can catch a plastic sheet or line.

Another style is nothing more that  two small metal loops attached to a swivel, but no adjustable clasp. These have no sharp edges, but can be slightly more heavy. Find these in the fishing tackle section of your store.

Another option is to skip the swivel altogether, and just tie off to the nosecone.

Now, if you're an inexperienced newcomer, you may be wondering how to do this without tearing your lines free from the parachute and threading them through the loop BEFORE you tie the second end to the chute.  The answer is so simple!

Gather all three ends of the loops together after you've folded your chute together. All three should end pretty dang close to each other. By pinching the loops together, you can feed all three of the loop ends through the eye of your circle at once.  Pulling a short length of these three loops out the other side, you can then feed either the nosecone OR the chute through the three loops at once.  Tighten the loops back down onto the circle as the lines tighten onto themselves.

For added security, you can add a small drop of wood glue or CA/Superglue to each knot around the parachute. It will keep them from unraveling. Make certain they dry before packing your chute away..

Now that I have covered all this in detail, the more experienced rocketeer has bailed long ago.  But this entry has been for the newbie, the novice rocketeer OR one who has never considered making their own chutes.  On smaller Estes low power rockets, it may be much faster and easier just to buy one or two of the pre-made chutes and be done with it.  Every rocketeer needs at least one spare chute in their range box.  Larger rockets will probably require a nylon or larger chute, and there are ways to cope with this too.  See my other entries on umbrella conversions to chutes.

I'm going to stop now, cause the next topic is to attach the shock cord to your rocket and nosecone, and there's such controversy over which is best, that

I think I'll quit while I am ahead. 

This has been the Thrifty Rocketeer asking, "How many chutes can YOU make out of a thick garbage bag?"