This is a guide on how to construct a five engine rocket out of parts laying around your house. This rocket should cost next to nothing besides the engines to launch it. The construction took about four hours to do with limited tools.
For this rocket I used the following parts:
-Some thin craft plywood
-Two cardboard tubes one slightly smaller than the other
-A mailing tube cap
-A plastic bag (preferably a Target bag)
-Three roughly two foot stands of kite string
-A two foot stand of elastic
-Two small pieces of thin cardboard
-Some electrical tape and glue
The tools I used for this project was limited since I was at college when I built it. So my tools I used were:
-A drawing compass
-Scissors -A clamp
-A dremel with sanding drums, cutting wheel, and drill bit attachments.
Step 1: Getting Started
The first step in construction is to select your tube for your rocket. Once you have this measure the inner diameter of the tube. Now use the drawing compass to make tthree identical circles the size of the inner diameter of your tube.
Now you will need to decide what size engine you want to use and how many you want to use. For this rocket I choose to use a A10-3T engines. for this arrangement I chose an X formation. You can choose to arrange your engines in other positions, but they need to be equally spaced for the weight of the rocket. Once you decide on the engines sketch them on to one of the circles you have drawn.
Step 2: Cutting Out the Engine Mounts
Now that you have your three circles traced out you now need to start to cut them out. First cut the three main circles out. Keep close to the line but don't cut to much, since the fitting of these pieces needs to be tight. Once you have these pieces cut out test them in your main rocket tube to ensure a tight fit. Now take all three circles and clamp them together, place the circle with the engine placements so you can see it. Then make pilot holes in the center of all the engine placement location. Then remove one of the circles that does not have your engine sketch on it and reclamp the other two. Now use a drill bit the size of the engine you are using to drill out the holes. For the third circle do the same but use a bit 1-2mm smaller. Unclamp the two circles. Take one of them and trace the diameter of the smaller tube onto it and cut to size. I find its easiest just to use a sanding wheel to do this step with a sanding wheel. Then check to see if it fits into the smaller tube.
Step 3: Assemble the Engine Block
To assemble the engine block take the small tube and make it 2/3 to 3/4 as long as the engines you will be using. Then coat the inside of the tube at one end with glue, be generous with the glue here since the forces on this part are great. Then insert the circle that fits in this tube and make it flush with the end of the tube. Now take the circle with the smaller holes drilled onto it and glue it to the top of the circle already inserted in the tube. Ensure that the holes in the two pieces are lined up. Take the final circle and glue it to the other end of the tube aligning the holes with the other two circles (a trick to get the top and bottom aligned is to use an engine or two to test alignment).
Step 4: Engine Block Insertion
Once the glue is dried on the engine block take your large tube and place a generous amount of glue on the inside of it. The area the glue covers should be as long as the engine block is. The take the engine block and slide it in flush with the bottom of the main tube and let dry.
Step 5: Fin Creation
While the main tube is drying you can start to work on the fins. I choose to use four fins because of the diameter of the rocket but three fins or more would work as well. I used some pre-maid fins for this rocket that were from an old rocket kit. Making from scratch is not that difficult though. First make a paper template of what the fin you want should look like. Then use your template to trace the number of fins you want. Now cut your fins out and you could be done, but to get a better look for the fins clamp them all together and sand them to be all the same.
Step 6: Attaching the Fins
Once you have the fins cut out you will need to attach them to the large tube. For the first fin put a generous amount of glue on the outside of the tube as shown in the picture. Then place it on the rocket. Make sure the fin is as close to straight with the main tube as possible. I just eyeball it and am able to do this fine. Then allow glue to dry. For the next fin if your using four fins you can use a book for proper alignment of the 90-degree angle or as I did just eyeball it. Attachment of the rest of the fins is the same as the first judge placement, apply glue, attach fin, position fin, and let dry.
Step 7: Shock Cord Attachment
Take the cap and make a hole just large enough for a piece of elastic to be pushed though and trim off the pull handle on the cap (I did this later but it easier to do it now). Take one of the small strips of cardboard and apply glue to the length of the strip. Now place your elastic on the glue as seen in the picture. Then fold the cardboard over the elastic (best to fold it twice) and let dry (may have to clamp depending on the cardboard used). The end result should look something like the picture. Take the other end of the elastic and place it through the hole made in the cap. Repeat the cardboard attachment process for the other en of the elastic. Now pull the elastic on the top side of the cap down until the you can place the cardboard on the cap. Apply a generous amount of glue to the top of the cap and place the cardboard in it.
Step 8: Nose Cone
The nose cone of the rocket should ideally be something pointy, but something round will do the same job (but does not go as high when launched). For the cone I cut the top part of a tennis ball off and glued it to the top of the cap. TO measure the size needed I placed the cap to the tennis ball and traced a circle.
Step 9: Recovery System
For rockets that are light this step is easy attach a foot and a half long ribbon to the middle of the shock cord and your done. This rocket is to heavy for that so a parachute is needed. First take a plastic bag (I like Target bags the best) and cut it in half. Then sketch out a hexagon onto the bag the sides should be around five inches. Now cut it out. On the corners of the chute take a piece of electrical tape and place it on one side and fold it over. Next make some small holes in the tape just big enough to put some kite string through. Take your kite string and cut it to about a foot and a half to two foot length, you will need three pieces at the same length. Take the string and tie it to the chute with the two ends of the strings attached to corners that are next to each other. To finish the parachute pick the chute up by grabbing the center of all the strings and the top center of the chute pull away from each other and spin one end.
Step 10: Attaching the Recovery System
Take the parachute and place it mid ways on the elastic. I looped the parachute through its bottom end and then tied a knot on the elastic to ensure the parachute does not move. Take the large tube and place a generous amount of glue about an inch or two inside the tube then take the end of the elastic that has just the cardboard attached and place it in the glue.
Step 11: Attach the Guide Tube
Now take the straw and cut a piece about one and half to two in length. Then apply glue to the outside of the rocket the length of the straw. Set the straw in the glue so that it runs parallel with the main tube. Once the glue is dried you have a rocket ready to launch. You may apply paint if wanted to make it more stylish. This is my first instructable and hopefully this helps with making rocketry a little more affordable and creative.