[NRVR-Members] L3 Build Techniques

Peter Cadra pcadra at yahoo.com
Sat Nov 26 17:13:07 CST 2016

Threaded rods have practical use but are not the end all. As Bob wrote, use top shelf epoxy like West Systems and prep the surfaces for a good grab. I have been using extra pieces of coupler  rings with excellent success for smaller builds, but in my BFR and other L3 builds, I use a long double coupler from the top centering ring with 1.5x the airframe diameter exposed from the top of the booster airframe. You can secure the coupler a bit more with screws if so desired.
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  On Sat, Nov 26, 2016 at 8:25 AM, Bob Schoner<bob.schoner at gmail.com> wrote:   I am not a fan of using threaded rods through centering rings. Unnecessary extra weight and questionable added value. I have never seen a rocket fail in a way that threaded rods would have helped. Proper surface prep with 40 grit sand paper, good epoxy (not 5 minute hobby store stuff) is more than enough. If you want more centering ring security at the top glue a 3" section of coupler and fiberglass it to the recovery centering ring. 

If the right materials and techniques are used I don't feel TR adds anything but extra weight. That is just one opinion. Let's hear some more. 


Congrats on your Black Friday score!
On Sat, Nov 26, 2016 at 1:14 AM Thomas Tweeks Weeks <tom at theweeks.org> wrote:

Hey all..


So I'm finally going L3... (partially thanks to Black Friday). I'll leave what I'm building a surprise.. All I'll say it that I chose a 75mmt kit that will let me cert L3, but also adapt down to 54mm and fly this bird at our monthly launches too.


That aside, I did want to get some of your (current L3s) suggestions and lessons learned from your L3 builds (and other large project).


There's one interesting TRA guy I've been following on Fbook who's got some pretty cool fincan construction and build ideas.. thought some of you might want to check them out and comment. I'm all ears on your big suggestions and lessons learned. Check it out:



He uses an interesting three thread-stock rods to pass the recovery forces down through the forward centring ring down to the lower CR too (or thrust plate if you have one). Pretty cool.


But if you look at his pictures, he also perforates his forward CR a total of five times.. something that makes me nervous. Especially all the force on just one side of the MMT's CR. Seems more risky.


I was actually thinking about doing something similar but using a two super long thread-stock rods and U-bending them form U bolts (four rods) that run the length of the entire MMT.


See crude diagram:



Thoughts? Ideas?


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