This section contains information about parachutes and mechanisms to deploy them.
Look in the sub-directories under CHUTES for more information.
The UFO Parachute Toy – Any Useful Ideas From It?
Back in the 60’s I had a yellow toy UFO that used a parachute. It was about 4 inches in diameter and was shaped like a fat flying saucer, made of heavy rubbery soft plastic. It was molded in one piece and opened like a clam shell into halves joined by a hinge strip . The two halves sealed together around the rim.
The bottom was round but the top had a small round raised area in the center. There was a small hole in the center of the top. Inside the top was a short threaded neck around that hole. A small plastic cap screwed onto those threads to regulate air flow through that hole. The parachute attached to a ring molded into the inside of the saucer. The idea was to pack the chute small enough to fit inside, squeeze the bottom of the saucer to force out the air and then hold your finger over the air hole until you threw the thing as high as you could.
When enough air had sucked back into the saucer the halves separated and the chute tumbled out. That is if you had set the regulator cap right to time it and you had made a good throw.
I wonder if such a method could be used to time chute deployment in a water rocket? Squeeze the air out of something and cap the hole. At launch the hole would be uncapped and that container would start expanding until it triggered the release of the chute.
Maybe a spring inside of a cylinder with a movable piston at one end. Compress the spring with the piston to force the air out of a small hole in the opposite end of the cylinder. Plug the air hole and the piston keeps the spring compressed. Open the air hole and the spring begins to slowly move the piston back out to activate the release mechanism. I’m looking at a large empty syringe that was used to refill printer ink cartridges. It might have possibilities if the piston seal would keep working smoothly and reliably.
Making a pattern
If you want to make parachutes that perform consistently and look better, you should make a pattern. I prefer a piece of heavy cardboard from an appliance carton but a piece of poster board should work fine. If you only need a small parachute, look under a large frozen pizza for a round piece of cardboard ready to use.
You need to be able to draw an accurate circle with an exact center point. If you can find a large beam compass, it will make great patterns. It has a point at one end of a bar, with a movable pencil holder on the bar that can be locked down at the desired radius. It should be easy to make one. Take a piece of wood, drill a hole for a point ( small sharp nail ) near one end and drill a hole to fit a pencil at a distance from the point to match the radius of each circle that you want to draw.
Once you have the circle drawn on cardboard, cut it out with a sharp utility knife. Use scissors if using poster board. If your board is too small for the circle that you need, try a semi-circle. Use a straightedge to draw a line through the center point and cut out the half pattern. Divide it into sections as described below, then either make a duplicate of it to complete the circle or carefully reposition it after you have traced half the circle and continue tracing the other half onto the plastic material.
Draw a straight pencil line through the center point and both sides of the circle. Emphasize the line where it crosses the circle with a fine tip marker. Then draw a line through the center perpendicular to that one to divide the circle into equal quarters. Accuracy matters. Use a square if you can, but a new sheet of paper is probably square enough to use.
If the circle is smaller, then it will be divided into eight sections. If it is larger, divide it into twelve sections. Drafting triangles come in handy here. They were used in olden days before computers, when draftsmen used pencils and paper to draw their plans. One triangle has a 90° angle and two 45° angles, it’s used for the eight sections. The other triangle has 90°, 30° and 60° angles and is used for twelve sections.
For eight sections, use the 45° angle to divide each quarter of the circle in half. For twelve, use the 30° angle to divide them into thirds, using the 60° to verify accuracy. Use the angle and a long straightedge to draw pencil lines through the center point. Measure between the 8 or 12 points around the circle, they should all be the same distance apart. Make final adjustments if necessary, then use a fine tip marker to darken the lines at the edge of the circle. Make a tiny hole at the circle’s center point just big enough for the marker’s tip.
marking the pattern onto the plastic material
Smooth out the plastic on a table. Position the pattern, marked side up, on the plastic where there will be the least waste. Carefully trace a thin line around the circle. Mark the section lines outside the circle, then make a dot at the center hole. Remove the pattern and then extend the section marks slightly inside the drawn circle. Obviously these marks will be where you attach the parachute lines. Carefully cut out the circle around the outside edge of the marked line.
attaching the reinforcement rings
If you are using a plastic “party” table-cloth material, my personal favorite, and one side has a cloth-like texture, turn the smooth side up for applying the stickers. This will be the outside surface of the finished parachute. Vinyl reinforcement rings, the type used for strengthening holes punched in binder paper, can peel off of plastic easily. Printer labels stick very well to plastic, almost irremovable without tearing the plastic. The rings do, however, stick very well to the paper surface of the printer labels. So, I cut circles that are somewhat larger than the rings out of printer labels and apply them first.
Center one of the label circles at each of the 8 or 12 divider marks. Leave just a little space from the edge of the plastic so that the label does not extend past the edge and stick to anything else. Center a reinforcing ring on each of the labels and press them down firmly. If you are making a very large parachute or think it will need to take a lot of stress, apply reinforcement to the back side as well. Make a tiny hole at the center of each ring for attaching the lines.
using the right lines
Try to avoid using ordinary cotton or twisted types of strings. They are more likely to get fuzzy and frayed with use, and some can even change length if you get water on them. They are also easier to snag on rough parts of the rocket.
The best lines to use are braided nylon, such as braided fishing line and some other very thin types of cord. They are smoother and made to be wound up tightly over and over again without much fraying or tangling. Fishing line obviously has no problem with water contact. Unfortunately other braided lines seem to be much harder to find anymore compared to cheaper twisted lines.
cutting the lines to the right length
You will want to cut half as many pieces of line as you have made reinforced rings on the plastic. Opposite ends of each piece will be tied through adjacent rings. Lines should be cut to at least double the diameter of the plastic circle, plus several inches extra for tying two knots. Cut all the lines to the same length and try to tie the knots the same.
tying the right knots
You should learn to tie the right knots for attaching the lines to the plastic parachute material. You definitely don’t want the knots to loosen and have to tie them again every launch or risk a parachute failure. Neither do you want the knot to keep drawing up tighter until it cuts through the plastic. You want the loop tied through the material to remain the same once it is tied so that all your lines stay equal. You should learn how to tie something like a Bowline or Figure Eight Follow-Through knot for making the loops.
Tie the lines to adjacent rings so that you have long loops around the perimeter of your plastic circle. Take each line, even it up to find its middle and tie a two inch loop at the middle. Gather up half the adjacent lines, even up the loops and make a loose knot just above the loops to join them together. Repeat with the other lines. Make sure there are no tangles and bring the two sets of loops together. Another loose knot is tied to join them. If you divide a large parachute into 12 or 16 sections, you can gather the loops into equal thirds or fourths to make untangling easier. Tie a strong shock cord through these loops for attaching to a rocket.
I usually slip an inch long piece of small plastic drinking straw over the loops and past the knots, it seems to help keep the lines straight when folding the parachute and wrapping the lines around it. Normally I slide it all the way up the lines to the plastic to help gather the plastic together for folding. When the parachute pops open, the straw slides down the lines to the bottom. This causes a slight delay in the opening of the parachute because it can’t pop fully open instantly. Sometimes this is desirable to reduce the impact of opening on the parachute material if it is deployed when the rocket is going faster than expected. Research the term “reefing” for parachutes for more information.
A fishing swivel should be connected between the parachute and the rocket to minimize twisting. Get a size large enough to make it easy to work with. Mine have a clip like a safety pin at one end. Either attach a swivel to each parachute that you make and clip any one of them to a rocket, or attach a swivel to each rocket that you build and clip any parachute on as you need it.