Builds Rockets for NASA
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- Aug 27, 2011
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I'd say one of the most common is mis-application of materials. It can go both ways, but I think most often for people new to HPR is to over-build.
For example, it is very easy to read over some of the great build threads of big, fast, giant-motor projects and go down the rabbit hole that your first HPR needs to be built with 3 layers of 10oz fiberglass tip to tip, when in reality, most L1 rockets are fine with just cardboard and wood glue.
I definitely overbuilt my L2 cert rocket to insure there would be no construction issues with firing a J500, but other than that I agree with everything you said. It's very easy to get overly conservative at the cost of considerable loss of performance.
Just curious how you could arrive at the pad without the motor installed ?Once I have had my rocket on the rail before I realized I didn't have a motor in it.
Check rail buttons to ensure they are firmly attached...check again. Had one pull off while removing a rocket so I could install the motor that I had forgot at my pit area.
If there's no motor installed, I doubt it poses much of a safety hazard.Just curious how you could arrive at the pad without the motor installed ?
RSO should catch this = as they are REQUIRED to check motor retention, meaning they should note the empty hole ?
"rookie RSO " mistake ?
It may have been 2.5lb, but yes it's built like a tank. My design philosophy thus far is that the main chute's purpose is to serve as a curtosey to whatever the rocket land on.Scrapmaster ............ was that 14" or 14'
It just seems; a 14 inch Chute is to small to safely land 3 pounds !!
Calculator puts it at like 37.29 mph ground impact !! Good Job on the Build then !!!
I am currently trying to figure out the drouge for my LvL2 Model............
When you ask about 'construction', that can be construed as either materials or methods. Others have mentioned materials, so I'll mention methods. Based on my personal observations and experience, if you are going above Mach and want top performance:I have a question.
What type of construction is required to handle transonic flight?
I know how to do the calcs, but materials numbers are hard to find.
So, I'm asking what works reliably?
I use rocketpoxy for fillets and I pull the tape off 10 to 15 minutes after I apply the rocketpoxy. At that point it will flow enough to eliminate ridges from the tape line but thick enough not to flow where I don’t want it.Putting tape down on both side of your wing fillet??? Now you have a ridge of epoxy to sand down or fill. If you sand it you just divot out the body tube and wing. Mounting your engine tube flush with ether centering ring top or bottom. Effectively eliminating one glue joint from the engine mount to the ring and eliminating the possibility of adding a motor retainer.
Even had you looked at the thrust curve, how would you have known that it would shred? is there a rule of thumb to follow?My biggest mistake was not looking at the thrust curve for an H115 when I attempted my L1 certification. I lost the NCR Big Brute (built with epoxy) I had built for that attempt an hour before and switched to a MDRM I built with wood glue and had launched on an F50. The fins shredded on the way up in a spectacular fashion. We thought the motor had CATOed because we thought we saw flames as it flew apart, but the motor was intact. View attachment 467652View attachment 467653View attachment 467650View attachment 467651
Is that so or is that the mistake?Weld is only for bonding metal components. Use it for that, and don't use it for anything else.
JB Weld is a company that produces about 70 different adhesive products. They make 6 or 7 different epoxy puttys. They also make dozens of types of "liquid" 2-part epoxies, various silicone and RTV products, tire patches, copper gasket paste, thread-locker, and so on.My rookie mistake was that I expected JB Weld is the same as I remember from years ago. The JB weld I remember was a putty, not a paste. Am I right on this or has my memory did a mash-up again?