Construction Information
Safety During Construction
Always dry fit parts before applying epoxy, and sand if necessary so that they fit properly.
When sliding circular parts together, hold them so that the epoxy forms a fillet and doesn’t pool or drip off. The required orientation is usually vertical.
If you slide two parts together, the epoxy will always be pushed forward off of the part on which the epoxy was applied. e.g, if you are epoxying a coupler to the inside of a body tube, the excess epoxy will be on the inside of the body tube if you apply the epoxy to the inside of the body tube, and on the outside of the body tube if you apply the epoxy to the outside of the coupler.
Twisting circular parts while pushing them together will spread the epoxy more evenly in the joint.
There is a student-written TLDR talking about hints when following the instruction. It was written for the MiniDX3, but it still largely applies to the other Level 1 rockets.
There is a detailed student-written blog on putting the rocket together. It was written primarily for the MiniDX3, but it still largely applies to the other Level 1 rockets.
For more information about safety precautions, visit DOFPro Rocketry Safety
Construction Hints
Aerotech Arreaux Construction
- It’s worth buying an extra-length motor-mount tubes when attempting the level 1 certification. A length of at least 15” will work for Aerotech 29/180 or shorter motors. You’ll need to fiberglass your rocket to fly motors with more than 180 Ns of impulse. You will need a length of at least 16¼” for the H115DM-14A, the H182R-14A, the H135W-14A, and the H195NT-14A, and a length of at least 19¾” for the I205W-14A. For the extra-length motor mount tube, you can either order the replacement motor mount tube from Aerotech, or eRockets.
- You won’t need the 24 mm motor adaptor and don’t need to construct it. Most of the parts are no longer in the kit.
- You need to attach the included motor retainer instead of the Motor Hook, Thrust Ring, and Thrust Ring Flange. These changes are detailed in the Arreaux Motor Retainer Upgrade Notice. Attaching the motor retainer should be done AFTER the rest of the rocket construction is completed (after Step 1 of the FINAL ASSEMBLY AND FINISHING in the instructions), otherewise it will block the application of the cyannoacrylate to the fin roots and the aft Centering Ring. Use JB Weld to attach it. The details are in the Aerotech 29 mm Motor Retainer Instructions (all on the Aerotech website http://www.aerotech-rocketry.com/resources.aspx?id=4 near the bottom of the page).
- Use tapped holes and threaded #6 nylon screws to secure the nosecone to the payload section. Two is the minimum, three is recommended, four is allowed. Friction fitting with tape isn’t sufficient.
- It’s often useful to be able to replace either the body or the payload/nosecone. The recessed screw eye on the payload section makes it difficult. You may want to make an extension out of 1/8” rope and a quik-link and attache the shock cord to the quik-link.
- Make sure you can dry-fit the fins BEFORE you CA them in place. You may need to sand down the ridges a little to be able to snap the fins into place.
LOC Precision Vulcanite
The build instructions for Labs 4 and 5 already incorporate most of the hints below. 1. Be sure to roughen all surfaces to be epoxied, with 60, 80, or 100 grit sandpaper before you glue so that the epoxy adheres better. 2. Get an Aero Pack RA 38mm L motor retainer. 3. Sand the bottom 3/8” of the motor mount tube until the motor retainer slides on easily. 4. Replace the elastic shock cord in the kit with 12 ft to 15 ft of either tubular/strap nylon or tubular/strap Kevlar, such as PML STRP-0.375, eRockets ER9044, Wildman KEVLAR1/4”, or Madcow SC_FLT_38_RED. 5. Use either the PML mounting style or the Modified PML mounting style for the shock cord. For the PML style, follow steps 1 & 2 in the Phobos Instructions. You’ll have to machine or file a notch in one of the centering rings to accomodate the shock cord. The centering ring on the other end (held in place with tape), must be at least 3/8” from the end of the motor mount tube and preferably 1/2” to accomodate the motor retainer. When assembled, the motor mount will protrude from the end of the rocket a bit. The modified PML style is similar, but instead of epoxying the shock cord axially to the motor mount, it is tied radially around the motor mount tube and included in the epoxy fillet between the motor mount tube and the centering ring. Step 2 of the Madcow Batray instructions show the tying technique, but has the notch on the outside of the centering ring instead of on the inside where it belongs. 6. If you want streamlined fins, round the leading edge, and taper the trailing edge. Leave the inside and outside edges square. 7. Consider laser-cutting a pair of fin guides to ensure the fins are perpendicular to the body tube. 8. Use the PML technique to attach the fins as shown in Step 4 of the Phobos Instructions. When you finally epoxy in the bottom centering ring, push it flush up against the fins. 9. When prepping the Payload Bay, consider finding a screw eye that attaches with a nut and washer rather than just a wood-screw end. 10. When you epoxy in the coupler tube bulkhead, recess it at least 1/8” so that you can put a decent fillet between the bulkhead and the coupler tube on the outside. DO NOT make the bulkhead flush with the end of the coupler tube. The LOC instructions say to, but they are seriously wrong and you may lose your payload section when the recovery charge goes off. 11. Secure the nose cone to the payload section with three countersunk #4 flat head screws. You can use the pan head screws but they don’t sit as flush. 12. If you are planning on Level 2 (J) flights, either replace or supplement the launch lugs with rail guides, either PML LRL-10-2 or Acme 54mm. 13. Secure the motor retainer with JB Weld.
Folding a parachute
The goals in folding a parachute are the following:
- Protect the parachute from the hot gases and ash generated when the ejection charge goes off. Plastic-film chutes can form a tangled messy wad if contacted by the hot gases and ash. Nylon chutes can end up full of holes and function improperly.
- Keep the shroud lines from tangling during deployment.
- Ensure that the parachute slides easily into and out of the body tube, so it will deploy properly.
- Ensure that the parachute canopy inflates fully after ejection.
Begin by stretching the parachute out by two opposing shroud lines to form a half circle (or half hexagon or half octagon, depending on how the chute is cut).
The illustrated chute is for the Vulcanite. It has eight shroud lines. In this case we fold the two outermost lines to meet in the center with the center shroud line. For a hexagonal (six shroud line) chute like for the miniDX3, you would fold so that the shroud lines meet the opposing shroud lines to form a triangle.
If necessary For an eight shroud line chute it’s necessary to fold the chute in half again to form a triangle. For a six shroud line chute, the first two folds of the 1/2 chute should have formed a triangle and the third fold is unnecessary.
We are going to fold the shroud lines inside the chute to reduce the chances that they will tangle or get snagged on something during ejection. Place the shroud lined on top of the chute as shown.
Then fold the triangle over the lines by bringing the two sets of shroud-line attachments together to form a thin right triangle. Then fold the long tip of the triangle down to the base (where the shock cord meets the shroud lines, and fold the remaining triangle tip over to form a rectangle as shown).
Beginning at the top of the rectangle (the side furthest from the shock cord), roll the chute tightly into a cylinder as shown.
Place the chute in the center of the Chute Protector with the two parts of the shock cord going to your left, as shown.
Take the lower corner of the chute protector and wrap it around and tuck it under the chute, like starting to roll a burrito, as shown.
Fold the two horizontal corners of the chute protector into the middle of the chute protector, just like you were rolling a burrito. The one shock cord will pass through the hole in the chute protector, and the other one will be routed approximately as shown.
Now finish rolling up the chute inside the chute protector, like you were finishing a burrito or a spring roll. Try to ensure that none of the parachute is exposed outside of the chute protector. Any that is exposed is guaranteed to have a hole burned through it from the hot ejection gases and ash.
Again, to offer maximum protection to the chute, orient it so the end without the shock cords will enter the body tube first, and the end with the shock cords faces the nose cone or payload section.
First place all of the shock cord that is below the parachute into the body tube with as few tangles and twists as possible. Then slide the parachute into the body tube. If you’ve folded and rolled it correctly, it should slide into the body tube with very little effort. Slide it in as far as your finger will pushe it, and then place the remaining shock cord on top of it, and place the payload section or nose cone on top of the body tube.
While I have found the illustrated method to be completely reliable, there are alternate methods for folding a parachute. Here are some of the alternates. - YA Method - Apogee Components - Apogee Components II - Queensland Rocketry - Rocketman - Fruity Chutes Iris.