- Joined
- Jan 27, 2009
- Messages
- 4,498
- Reaction score
- 2,975
After flying my Jupiter C, Hellfire and TitanII/Dyanasoar, I think I have the lightweight foam structure concept undersood, and have confidence they will last more than a few flights. It was really fun flying these large rockets on small motors. I decided to apply it to another model that typically weighs a lot and needs lots of nose weight, lets see how it turns out. I'm thinking this will end up at 3.75-4.5 pounds, be 8" in diameter and about 80" long. Will have an altimeter bay and use the stuffer tube to route the deployment wires up into the parachute bay. Will only need a 48" chute. I'm basing this on my foam 5.25" version that weighs 20 oz rtf as I know the CG location and that it flies straight. Simulation shows an I-200 to 1000 feet.
I calculated the top tapered cone section of a pershing 1A would have a 4" base and 11" length if I used a body diameter of around 8 inches. So, that's the diameter of the parachute cup at the top that I'm using a 12" pml section for. I got a good deal on some sunward bt-56 tubes so I assembled those with couplers to make the stuffer tube/spine.
I found a craft cone at a store that had the right proportions, cut it to length, added a foam tip and and ran a carbon 3/16" rod down the middle to take landing loads and attach it to the base plate. I added a 1/8" base plate with a doubled 4" pml coupler to make the shoulder and added an eye bolt. the styrfoam is porous and rough so I covered it in a layer of 2mm depron, sanded and then covered it with monokote self adhesive trim in black for protection and the cone is ready to go. I'll add the red/orange afterward as an extra layer. This is the piece that will eject and pull the 48" chute out.
I made the fins from doubled 6mm depron with carbon strips on the leading and trailing edges for landing protection/stiffness and the lower fin has a carbon rod spar to the tip, again to help with landing loads.
I'm using a spreadsheet to track estimated(based on density of parts) total weight, and then putting in actual weights as I get them. So far tracking ok.
Also interesting to see what the costs wind up being to compared to highpower components...
Foam cost ~$35
Tubes and couplers $30
PML Tubing $10(got a $10 discount)
retainer $27
plywood $20
Hardware $7
Carbon fiber $22
I already have a chute, kevlar line, altimeter and nomex that can be swapped from another model.
Frank
View attachment Pershing8foam.ork
I calculated the top tapered cone section of a pershing 1A would have a 4" base and 11" length if I used a body diameter of around 8 inches. So, that's the diameter of the parachute cup at the top that I'm using a 12" pml section for. I got a good deal on some sunward bt-56 tubes so I assembled those with couplers to make the stuffer tube/spine.
I found a craft cone at a store that had the right proportions, cut it to length, added a foam tip and and ran a carbon 3/16" rod down the middle to take landing loads and attach it to the base plate. I added a 1/8" base plate with a doubled 4" pml coupler to make the shoulder and added an eye bolt. the styrfoam is porous and rough so I covered it in a layer of 2mm depron, sanded and then covered it with monokote self adhesive trim in black for protection and the cone is ready to go. I'll add the red/orange afterward as an extra layer. This is the piece that will eject and pull the 48" chute out.
I made the fins from doubled 6mm depron with carbon strips on the leading and trailing edges for landing protection/stiffness and the lower fin has a carbon rod spar to the tip, again to help with landing loads.
I'm using a spreadsheet to track estimated(based on density of parts) total weight, and then putting in actual weights as I get them. So far tracking ok.
Also interesting to see what the costs wind up being to compared to highpower components...
Foam cost ~$35
Tubes and couplers $30
PML Tubing $10(got a $10 discount)
retainer $27
plywood $20
Hardware $7
Carbon fiber $22
I already have a chute, kevlar line, altimeter and nomex that can be swapped from another model.
Frank
View attachment Pershing8foam.ork
Last edited: