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This is the procedure to place weight in the nose of your rocket. You can use #6 lead shot purchased at hunting stores, like Bass Pro Shops, but BB's will work. First use your hobby knife, or saw, to enlarge the opening at the bottom of the nosecone. Tape a small piece of sandpaper to a dowel and sand the inside of the nose where the glue will be. Next measure out the desired weight of lead shot in a cup. You can use a postage scale, or similar, for measurements. Place equal amounts of 20 minute Finish or 2 hour epoxy in cups. Combine all the cups contents and stir vigourously for one minute. Pour the mixture into the nose cone and brace, point down, for 24 hours. This is a common procedure and should produce excellent results.
Submitted by Doyle Tatum
I designed a 4" diameter scale Phoenix Missile. When running it through RockSim, I noticed that my stability margins were all over the place, depending on which motor I wanted to fly, because the fwd fins affect my CP, and my CG shifts wildly because of the short length of the rocket. I recall thinking that it seemed illogical to have to add as much as 11lbs of nose weight for an Aerotech K-700, and I could fly it without the weight on a J-90. So to acommodate all of the motors I thought that I would want to fly, I decided to resolve the issue of nose weight by making my nose weight adjustable.
On this particular rocket, I had the advantage of designing and building all of the parts myself because it is all composite carbon fiber and fiberglass. That stated, don't let your parts limit what you do with them - there's always a way. My nose cone was made from a female two-part mold, and so it was hollow. I figured that with the addition of sort of a motor mount assembly inside of the nose cone, I could make the parts that I would need to be able to hold a piece of allthread with weights attached to it. I designed the nose weight tube to be 54mm, just like the motor mount for another reason as well - I wanted to be able to fly an L-730 in it, and in addition to extending the motor into the nose cone (no nose weight required for that sim) I had to extend the airframe by an inch to make it fit. But I figured that by using a slimline threaded retainer (the same used for motor retention), I could turn a wooden 'puck' out of Red Oak (a dense hardwood that I happened to have access to) that could be inserted into the nose cone's weight tube, and locked down by the retainer. A piece of allthread bolted to that would hold the weights, which could add and remove as needed.
The next problem was to find weights of an appropriate size that I could add and remove. My Dad suggested that I help him dispose of some lead weights that he had in the back of a cabinet in his garage, so I took two pieces of 3/4" MDF, drilled the right size hole in it in a couple of places, and backed it with a third. I soaked the wood with water to prevent it from catching on fire, and I lined all of the holes with aluminum foil. Using a smelting pot that my Dad had, I melted the lead down, and filled the 'die' up with the molten lead and let it cool. Use caution, and your own discretion when handling lead in general, much less molten lead. It's hot, and it can burn you, and it's not all that good for you to ingest, inhale the fumes, or have it come in contact with your skin. You've been warned. Once cooled, I drilled a hole in the center of each of the 'Ding Dongs' (that's exactly what they look like!) so they can be mounted on the allthread of the nose weight puck.
When all was said and done, I made seven weights, each about 1.5lbs (more or less, they were molten metal) so I can add as much as 10.5 lbs to One Butt-Ugly Phoenix so I can acommodate just about any motor that I want to fly it on, and get my CG to match my CP for any given flight. One additional benefit that I didn't initially realize, is that I can keep all of the weights at the fwd end of the allthread, providing the greatest impact on my CG with the least amount of weight.
One final thought, my nose cone, with it's tube, and motor retainer might weigh half a pound once I paint it. It's very light, and very strong. I made a decided effort to attach the weights to my recovery train, rather than attach my nose cone to the recovery train. If by chance, something happens, I can rebuild any one component, but I do NOT want to be known as the guy that had 11lbs of lead fall from 8000'.
Submitted By Tim Scott |
