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The Challenges of a Successful Rocket Flight

shred
If you are already pulling out your Elmer's glue, your 15 year old xacto knife, the left over can of lead enhanced spray paint, and your childhood underwear for homemade shockcords, you have come to the wrong place, Go away now!.

This is for people wanting to fly high and fast on composite hobby rocket motors. If your previous rocket building experience is from your childhood Estes days, then you will need to amend your construction techniques.
The first decision to be made is what diameter of engine to fly in the rocket. There are 18mm, 24mm, 29mm, 38mm, 54mm, 76mm, 98mm, 114mm, and I will stop at 152mm. These diameters are for the size of the rocket motors. 18mm is the diameter of the Estes A-C engines, 24mm is the diameter of the Estes D engine and so on. In most cases, the bigger the motor, the more powerful the engine. Most of us will start with 29mm-54mm motors. If possible, always assemble the rocket to take the biggest motor that will fit and use adapters to scale down to smaller motors. This opens up an entire range of flight potentials. Most manufactures of rocket kits will have engine suggestions.
post hole digger

Choosing the size of the motor at this stage can provide an indication of how strong to build the rocket. It is important to remember to build strong but light rockets. Replace the Elmer's with epoxy resin, replace the xacto with a Dremel, use quality paints and primers, and do not skimp on the shockcord. If the kit comes with a stretchy shockcord, make a sling shot out of it and give it to your kids. I failed my first level 1 attempt due to these stretchy underwear waistband shockcords.

Rocket speeds can range from a couple hundred miles an hour to in excess of Mach 2. Build the rocket appropriately with these speeds in mind. Most rocket kits are fine if the instructions are followed and the rocket constructed well. However, if you wish to push the envelope, plan now. Remember, everyone wants to go higher and faster after a few successful flights under their belt.

I tend to build my rockets strong. Extra fillets along the fins and epoxy fillets around the engine bulkheads. With Sweet Vengeance, I applied a layer of KEVLAR cloth followed by a layer of fiberglass over the body tube. I vacuum packed fiberglass over the aircraft quality birch fins, and epoxy fiber glassed all bulk heads. I applied a layer of fiberglass tape above the shoulder of the nose cone to provide extra thickness and faired everything using epoxy and micro balloons. I did this because I knew that one day I will fly Sweet Vengeance on a 76mm M class engine . . ., maybe.

If given the option, choose rail buttons over launch lugs. Rail buttons are cheap and easily available.    Rail buttons allow the use of a stiff launch rail that will keep the rocket straight and true during the critical liftoff phase. Launch lugs require rods that tend to sway in the slightest of breezes.

Common rocket materials are epoxy resins, aircraft quality plywood, fiberglass cloth of various weights, carbon fiber, aluminum, expanding foam, and plastic. Combine these with sensible construction skills and patience and your rocket will be well on its way for its first flight. Just because certain materials are not in your rocket kit, does not mean that it cannot be substituted or upgraded. The materials used in your rocket depend on you and your flight aspirations. If in doubt, build strong and fly high.

To finish or not to finish, that is the question of the day. After all the construction, take the extra time to sand, prime, sand, prime, sand and paint. A rocket with nice round edges and smooth surfaces will perform much better. Also, it will attract the attention of the lovely rocket groupies that frequent the launches.

Now we need for select our engine.


Counter

Too much motor for the rocket causing a shred and leading to a really spectacular flight. Not good!

Electronics failure due to motor nozzle failure allowed the rocket to ascend fast and descend even faster. You should never have to recovery your rocket with a shovel. Not good!

By Peter E. Abresch Jr.
Constucting Your Rocket
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