MaverickLV
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Ok, well, I have had this idea for awhile but never thought to ask anyone else about it. Knowing my luck with "new" ideas (if this even is new) there is probably some giant flaw somewhere but I'll give it a shot anyway.
Anyway, after inserting some nose weight in my dad's 1/4 patriot from PML and running the rocksim again for it, this time with a lower altitude because of the added weight, I had an idea:
What if a design could be made to turn a small rocket that was relatively inexpensive into a very versatile bird that could handle very large motors without being lost? In essence I wanted to be able to take a 4" kit, make some mods, and be able to fly it on an h242 to 1000' or, if dad was going for his level two cert., put a J350 in it and still have it go to only 1500'. Therefore eliminating the need for a large field, large rocket with dual deployment (expensive) or low winds/high enough cloud cover (cooperative weather).
So, here is the basic design for the bird. Start with a 4" diameter kit that is 5-6' long. For this example lets just say it is a 1/4 scale patriot from PML with a 38mm MMT. The kit is about 57" long and has a 12" payload section.
Then, you make the modifications: Pick four pieces of 1/2" or 3/4" PVC tubing or even copper plumbing tubing about 8-10" long from the hardware store. Drill holes in the CR's for two of these tubes to go through. So it would kinda look like a three-a-breast cluster. Cap the forward ends of the tubes and glue them, as well as the MMT, in place in the CR's. Continue the rest of the fin can assembly with the fins, etc. Make sure they are really on there and if necessary 'glass them. Now, with the CR's and tubes all glued in place, put either male or female threaded closure onto the end which sticks out the aft CR. This way, you should be able to drop something in the two pieces of PVC and then close them off so that they form two small cylindrical compartments that are tightly sealed.
Then you need to make modifications to the payload bay. First glue everything together like you would and then get two extra bulkheads and drill two holes in them just like in the fin can (except no MMT). Epoxy them in place but this time seal the end of the tube which will face aft and put the threaded closures on the forward facing ends. Attach the NC with plastic rivets so it can be removed.
Now, before your flight, run Rocksim with the motor you are going to use, lets say a J350 and keep adding weight, using a "MASS OBJECT", to the point you want to have the CG at until the altitude is where you want it. Lets say 2000'
Now figure out the weight you added to get it to that point and measure out that much weight in lead shot. Place the lead shot in the two sets of tubes alternating how much goes in the fin can set and how much goes in the payload set so that the CG is where you want it. Then insert some Styrofoam to keep the shot from moving around at all, it must be very tight. packing Styrofoam with one end sealed w/ epoxy to keep shot from creeping down through the foam, would be good. Then seal the tubes with the closures.
Voila!
A very heavy rocket, but small and inexpensive, capable of flights on anything from an H123 to a K700 (54mm MMT) all to the same altitude if wished. Just a little change of weight!
So, what do ya think, is this possible?
Wow, that was a mouthful, if anyone gets confused or needs better explanation please tell me and I'll try to explain it better.
Dave
Anyway, after inserting some nose weight in my dad's 1/4 patriot from PML and running the rocksim again for it, this time with a lower altitude because of the added weight, I had an idea:
What if a design could be made to turn a small rocket that was relatively inexpensive into a very versatile bird that could handle very large motors without being lost? In essence I wanted to be able to take a 4" kit, make some mods, and be able to fly it on an h242 to 1000' or, if dad was going for his level two cert., put a J350 in it and still have it go to only 1500'. Therefore eliminating the need for a large field, large rocket with dual deployment (expensive) or low winds/high enough cloud cover (cooperative weather).
So, here is the basic design for the bird. Start with a 4" diameter kit that is 5-6' long. For this example lets just say it is a 1/4 scale patriot from PML with a 38mm MMT. The kit is about 57" long and has a 12" payload section.
Then, you make the modifications: Pick four pieces of 1/2" or 3/4" PVC tubing or even copper plumbing tubing about 8-10" long from the hardware store. Drill holes in the CR's for two of these tubes to go through. So it would kinda look like a three-a-breast cluster. Cap the forward ends of the tubes and glue them, as well as the MMT, in place in the CR's. Continue the rest of the fin can assembly with the fins, etc. Make sure they are really on there and if necessary 'glass them. Now, with the CR's and tubes all glued in place, put either male or female threaded closure onto the end which sticks out the aft CR. This way, you should be able to drop something in the two pieces of PVC and then close them off so that they form two small cylindrical compartments that are tightly sealed.
Then you need to make modifications to the payload bay. First glue everything together like you would and then get two extra bulkheads and drill two holes in them just like in the fin can (except no MMT). Epoxy them in place but this time seal the end of the tube which will face aft and put the threaded closures on the forward facing ends. Attach the NC with plastic rivets so it can be removed.
Now, before your flight, run Rocksim with the motor you are going to use, lets say a J350 and keep adding weight, using a "MASS OBJECT", to the point you want to have the CG at until the altitude is where you want it. Lets say 2000'
Now figure out the weight you added to get it to that point and measure out that much weight in lead shot. Place the lead shot in the two sets of tubes alternating how much goes in the fin can set and how much goes in the payload set so that the CG is where you want it. Then insert some Styrofoam to keep the shot from moving around at all, it must be very tight. packing Styrofoam with one end sealed w/ epoxy to keep shot from creeping down through the foam, would be good. Then seal the tubes with the closures.
Voila!
A very heavy rocket, but small and inexpensive, capable of flights on anything from an H123 to a K700 (54mm MMT) all to the same altitude if wished. Just a little change of weight!
So, what do ya think, is this possible?
Wow, that was a mouthful, if anyone gets confused or needs better explanation please tell me and I'll try to explain it better.
Dave