Thanks to many fine folks on this forum, a couple of books about HPR, and the 'University of
YouTube'... I've finally gathered enough information to feel confident in starting my first high power build. Not everything that I do will be as per the kit instructions. I typically approach '
instructions' as a basic guideline, to be used for
reference only, then I proceed to figure out better ways to get things done while also hoping to improve upon the finished results. I usually spend more time 'thinking things out', examining multiple approaches to doing things and trying to foresee pitfalls and/or flaws in my logic than I actually spend building. This project is no different! Should any of you folks find flaws in my way of thinking, my methods, etc., PLEASE chime in and give me your '
two cents worth'! I welcome ALL advice and suggestions! I'm sure that there are still MANY things that I have not considered, at this point. Things that I do not yet know to expect that could possibly bite me later on down the road. "Enough 'blurbage'; Here we go!"
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I wasn't real happy with the single 'open' eyebolt that came with my kit, for two reasons. 1) A hard deployment would put a lot of stress on one small area of the forward centering ring which could possibly cause the plywood ring to crack/fail. There's also the possibility that the open ring could actually open up and cause a failure. I chucked the eyebolt and replaced it with 'two' 'U-Bolts', with backing plates, thus creating a much larger footprint to distribute any stress loads over a much greater area. Not trusting standard nuts/washers to remain secure... I used lock washers 'AND' nylon lock nuts on the bottom side of the forward centering ring and just a nut and washer on top. The threads are all coated with super glue and once I am happy/ready to make the centering rings disappear down inside the booster section, the hardware will be encapsulated in epoxy.
This is the dry fitted motor mount assembly;
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Forward Centering Ring;
The backplates for the u-bolts were a bit too large, so I had to grind them to fit the outside of the motor tube and also fit inside of the main body. No biggie. "Dremel!"
The u-bolts are 1/4" diameter. That's probably overkill, but Home Depot didn't have anything smaller. "
There goes a few feet in altitude!" LOL, but hey. This is for certification. I don't mind 'low and slow'!
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Aft Centering Ring;
I installed 6-32 blind nuts for positive motor retention. That's probably overkill, too, but once again. #6 was the smallest that Home Depot carried.
That extra small hole you see is simply a vent, for equilibrium, to prevent the sealed portion of this rocket from pressurizing on its way up.
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The motor mount tube, itself, has been thoroughly sanded to remove that slick skin and make for a better epoxy joint when I glue everything up. I've also coated both ends, inside and out, with super glue to strengthen the edges/ends of the tube.
My current thought of assembly is to initially leave 'both' centering rings loose on the motor tube, secured by tape only. Insert assembly, to its proper location in the booster, then epoxy the root of the fins to the motor mount tube. Once the epoxy has cured, remove one centering ring at a time and add epoxy/fiberglass cloth reinforcement to the fins, motor tube and inside of the booster tube. This should be 'great' insurance in keeping the fins on during launch/touchdown. Leaving both centering rings loose will allow me to more easily reach both the upper and the lower fins, for reinforcement, on this split fin design. "There goes '
ANOTHER' few feet in altitude! :smile: Once everything is cured, I'll epoxy the two centering rings in place, add small decorative fillets to the outside joints of the fins/body tube and move on from there. Stay tuned for part three... Installing the motor mount!