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My 4" scratchbuilt pershing 1A flew pretty well, and was a testbed for building a 7.5" version. I gave up after a year of trying to get a true pershing cone from PR, and finally settled for one of their 5:1 conicals from wildman. For $110 or so it was a very nice cone. I decided it would be better to have a large pershing with an incorrect nose cone than not have a pershing at all, and I wasn't motivated to build one from scratch. A 5:1 conical is the right length, just tapers too much for the first part. This build will be very simple, nothing fancy, just to show what you can do easily to get a nice looking rocket without having to do a bunch of scratch building. I'm using 7.5" upscaled vinyl from Mark at stickershock.
I'll attach my open rocket file showing dimensions and construction along with current weight estimates and flight simulations on 38/54mm motors. The current weight will be around 18 pounds to get the required CG. Currently the cone is around 5# and has 2.5# of balast and I'm estimating I will need around 10 oz more but am waiting for the booster parts to do final balancing.
With that much balast and as pointy a cone as it is, it wouldn't last long on landing, so I cut off the first 5", drilled it out to 3/8" and inserted a piece of 3/8" allthread with a nut and washer at the base after filling with lead. I then re-profiled the tip so that the landing force will be on the allthread. I then epoxied the allthread and tip back onto the nose cone and filled the remaining balast.
When the forward bulkhead is installed it will tighten onto the allthread and the allthread and washer/nut will take the brunt of the recovery strain instead of the bulkhead/cone joint.
I'm intending on using a zipperless construction where the two separate chutes for booster and cone section are in the forward section and the bottom has the coupler installed.
Here are a few photos of the cone construction so far.
Frank
I'll attach my open rocket file showing dimensions and construction along with current weight estimates and flight simulations on 38/54mm motors. The current weight will be around 18 pounds to get the required CG. Currently the cone is around 5# and has 2.5# of balast and I'm estimating I will need around 10 oz more but am waiting for the booster parts to do final balancing.
With that much balast and as pointy a cone as it is, it wouldn't last long on landing, so I cut off the first 5", drilled it out to 3/8" and inserted a piece of 3/8" allthread with a nut and washer at the base after filling with lead. I then re-profiled the tip so that the landing force will be on the allthread. I then epoxied the allthread and tip back onto the nose cone and filled the remaining balast.
When the forward bulkhead is installed it will tighten onto the allthread and the allthread and washer/nut will take the brunt of the recovery strain instead of the bulkhead/cone joint.
I'm intending on using a zipperless construction where the two separate chutes for booster and cone section are in the forward section and the bottom has the coupler installed.
Here are a few photos of the cone construction so far.
Frank
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