An "R"-powered rocket build

Discussion in 'High Power Rocketry (HPR)' started by Rail Dawg, Nov 30, 2018.

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  1. Jul 8, 2019 #2041

    Theory

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    Just got back to this thread.

    FWIW I would strongly recommend nylon over Kevlar for the recovery system. If you want to exploit the flame resistance of Kevlar then use it for the 15-20’ closest to the chargers (what I do on my builds).

    The stretch in nylon, however minimal, will pay large dividends when recovering a 300+ pound bird. Especially if the charges do not separate the rocket at the ideal time.

    ...and +1 for the “Kate” system
     
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  2. Jul 8, 2019 #2042

    Rail Dawg

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    Ok guys lots of great responses here on both the recovery harness and the use of Kate!

    I’ll put the Big Red Bee GPS tracker in the Avionics Bay so the rocket can be tracked. Miss Kate in the nosecone will be fine. Am glad to hear so many positive responses about that system.

    Let me think about the use of nylon. What’s the breaking strength of 1/2” of nylon? Need to look that up. The entire recovery system currently has a breaking strength over 10,000 lbs. Would like to keep that number for safety reasons.

    As always the responses are appreciated. The collective is ALWAYS wiser than the individual.

    Thanks guys!

    Chuck C.
     
  3. Jul 8, 2019 #2043

    boatgeek

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    A couple of directions you could go with this. The first is tow straps as mentioned up above. The second is nylon lifting slings (eg here). Flipping down their site shows an 8" 1-ply or a 2" 4-ply sling meeting your 10k lbs rated strength, but you may want to look at what factor of safety they're using. You could probably size by breaking strength (rated strength x factor of safety) to match whatever other weakest link you have in your system. A quick trip to Google says that the factor of safety on webbing lifting slings is 7:1, so you could go down to ~1500-2000 lbs rated strength and still retain the 10K breaking strength. I would definitely want to see the factor of safety from the same manufacturer as the sling to make sure that they are on the same page you are about the strength. I would also buy from a reputable domestic company like Crosby--I've seen a few too many failures of imported parts that had faked certifications.
     
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  4. Jul 8, 2019 #2044

    Theory

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    Chuck, when I say nylon for a project like this I mean 1” nylon.
     
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  5. Jul 8, 2019 #2045

    Ez2cDave

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    Chuck,

    1/2" Nylon is a "NO-GO" . . . Here is some basic info ( note the variations, even at the same widths, caused by thickness ).

    https://www.theecwcorp.com/nylon-webbing.html#1


    ALSO, do some research on FLAT vs. TUBULAR webbing, in terms of strength and other characteristics !
    ( Pay SPECIAL ATTENTION to THICKNESS ).

    https://www.countrybrookdesign.com/blog/why-climbers-use-tubular-webbing-instead-of-flat


    Dave F.

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  6. Jul 8, 2019 #2046

    Rail Dawg

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    As much as I like the elasticity of nylon Kevlar is still my choice.

    By reefing the lines with things like rubber bands and masking tape a lot of shock can be taken out of the system.

    Like with so many things with our rockets there’s more than one way to skin a cat. Some decisions are easier than others.

    Going to go with the strength and fire-proofness of Kevlar. Your inputs on nylon are noted and appreciated.

    Chuck C.
     
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  7. Jul 8, 2019 #2047

    Ez2cDave

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    Attached Files:

  8. Jul 8, 2019 #2048

    VernK

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    Kate is very rugged but still not tough enough to survive a ballistic impact at over 900 feet/sec! The flight hardware did not survive that impact. However, it transmitted data right up until the moment of impact and the receiver on the ground did the voice synthesis and was speaking out the telemetry data after impact. On the other hand, Kate has been known to survive supersonic shreds and liftoff cato's.
     
    Last edited: Jul 8, 2019
  9. Jul 9, 2019 #2049

    Rail Dawg

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    Well Vern I appreciate the chance to have Kate aboard our big rocket!

    Is all you need is a 54mm tube in the nosecone? How long should it be? If anything else is needed just let us know and we’ll make it happen. Judging from your earlier post the setup for launch is quite easy.

    Thanks!

    Chuck C.
     
  10. Jul 9, 2019 #2050

    Rail Dawg

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    Picked up a new General 30 qt commercial mixer and a great bench scale good to 30,000 grams with .1 gram accuracy.

    Also got a nice 2-stage vacuum pump and thick plexiglass plate along with all the fittings to degas propellant.

    Going to pour another Q motor so we can test the first one. Also one and possibly two R motors. Would like to test an R if time allows.

    Nice to have the ability to make motors right in the rocket shed. If anyone lives locally to Houston it’s an open invite. Be careful though as you’ll probably be put to work lol.

    Many thanks to those that have spent the last few months teaching how to make the bigger motors. There are some tricks but if done correctly some great motors can be safely made.

    Exciting time to be in rocketry isn’t it?

    Chuck C.
     
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  11. Jul 9, 2019 #2051

    hobie1dog

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    Cool stuff, can you post a few pictures while making them just to give a quick tutorial for those that will never reach this level of rocketry?
    Thanks,
    Marty
     
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  12. Jul 9, 2019 #2052

    Rail Dawg

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    You bet Marty!

    Chuck C.
     
  13. Jul 9, 2019 #2053

    Nytrunner

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    Within the limits allowable without veering into research-restricted territory of course.
     
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  14. Jul 9, 2019 #2054

    Rob702Martinez

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    If you have time make a thread in the Restricted forum as I'd really like to see it too.
     
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  15. Jul 9, 2019 #2055

    Rail Dawg

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    Absolutely. Just an idea of how we do it.

    No specifics.

    Always a good idea to err on the side of caution.

    Thanks!

    Chuck C.
     
  16. Jul 9, 2019 #2056

    Motocrossman24

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    Check out Mac performances website, they have simple nosecone bays designed for the kate system...at the lest you could inspire your design for them, but if you appreciate the design, consider dropping them an email and seeing how you could incorporate their bay in your nosecone
     
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  17. Jul 9, 2019 #2057

    Ez2cDave

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    Chuck,

    Step #1 - No Smoking !

    Step #2 - See Step #1 !

    LOL !

    Dave F.

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  18. Jul 9, 2019 #2058

    VernK

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    Scroll down about halfway on this page: https://www.multitronix.com/transmitter.html
    It will show the dimensions of the Kate transmitter and a recommended mounting scheme.

    A 54mm tube is usually run right down the middle of the nosecone. It is pushed into the inside tip of the nosecone as far as it will go and then secured at the bottom by a bulkhead across the aft end of the nosecone. A short length of 54mm coupler tube should then be inserted above the transmitter to bias the transmitter back away from the tip. If the tip is metal then it would be good to bias it back at least 3-4 inches from the metal. Another 54mm coupler is then cut to length as needed to rest against the aft bulkhead and yet push the transmitter as far forward as it will go. The Kate transmitter is 11.8" long so of course the overall tube length needs to be at least that. Usually the tube is much longer than that and the coupler tubes are sized to perfectly fit the transmitter between them. The transmitter has two centering rings on it that are 4.55" apart. That is the gap size you need between the two coupler tubes that will perfectly capture the transmitter between them. I usually just cut the lower coupler tube to length in the field with a Kate transmitter installed so that it works out perfectly.

    Clear as mud?
     
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  19. Jul 9, 2019 #2059

    Rail Dawg

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    We'll make that work.

    Thanks Vern!

    Chuck C.
     
  20. Jul 9, 2019 #2060

    Rail Dawg

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    I'm having some trouble with getting a revised Q motor into Open Rocket. Had the Burnsim file and converted it to an .eng file no problem.

    Put the .eng file into the "Thrust Curves" folder using the guidelines from this website:
    http://wiki.openrocket.info/FAQ#How_do_I_add_motors_to_the_database.3F

    Other motor files I've added before are in OpenRocket but this latest Q doesn't want to work. Is it how I name the file perhaps? I do leave the .eng part of the file name alone. If any of you have a secret-decoder-ring trick to getting a motor to show up let me know. It's appreciated.

    Chuck C.
     
  21. Jul 9, 2019 #2061

    neil_w

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    Can you post the file? If not publicly, then send it to me in a PM and I'll see if I can sort it out.
     
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  22. Jul 9, 2019 #2062

    Rail Dawg

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    Check your PM. Thanks Neil.

    Chuck
     
  23. Jul 9, 2019 #2063

    FredA

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    Chuck - what bench scale did you buy and where did you get it?
    30kG is a pretty spiffy scale.
     
  24. Jul 10, 2019 #2064

    Rail Dawg

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    Hi Fred it wasn't easy choosing the right scale I just knew it needed to handle some pretty serious weight but be accurate to .1g So after doing as much homework as reasonably possible settled on this one:

    https://www.ebay.com/itm/HIGH-CAPACITY-LARGE-14x12-DIGITAL-BALANCE-SCALE-30000-x-0-1-GRAM-COUNTING-BENCH/173447219088?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

    Looks like it will satisfy our needs moving forward. Not sure about the quality of "T-Scale" products but we'll find out soon enough lol.

    Chuck C.


    Propellant Scale.jpg
     
  25. Jul 10, 2019 #2065

    FredA

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    Thank Chuck - looks to be a good choice on paper - may it serve you well!
     
  26. Jul 11, 2019 #2066

    TonyL

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    Chuck,
    Sewn-loop cords are only as good as the stitching [as I have found out]. A feature of tubular braid cord is that it can be doubled over and threaded through itself [like Chinese finger cuffs] to provide a knot-less, stitch-less loop. I have done this successfully with kevlar. It is not that hard to make a hollow threading needle to do the job.

    Stitched loops can be fine, but if it is not on a lifting sling with cert tags, one might want to test it to be certain it is a good design.

    I am interested in what you think of your scale. I have a lab grade Ohaus 22kg that I bought for the same reasons, but I never use it. My 8kg Ohaus is my workhorse. I find that a scale appropriate to the size of the individual measurements seems to work best.

    br/

    Tony
     
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  27. Jul 12, 2019 #2067

    Rail Dawg

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    Thanks for this info Tony.

    Good stuff. Things are coming together nicely. Have thankfully had a couple full days to devote to the rocket.

    The Q motor casing is being shipped to my house shortly with the R casing being built as we speak.

    Both should fit into the rocket nicely!

    I’ll post some more pics soon of the recovery system.

    Chuck C.
     
  28. Jul 12, 2019 #2068

    troj

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    It's called a finger trap and it's very common in professional parachute rigging.

    Someone posted a video on how to do it.

    -Kevin
     
  29. Jul 12, 2019 #2069

    Rail Dawg

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    Tony and Kevin I have never seen the “finger trap” trick for making loops in tubular Kevlar.

    That is awesome!

    Chuck C.
     
  30. Jul 12, 2019 #2070

    Ez2cDave

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    The "finger trap" method has been used in hollow Dacron fishing lines since, at least, the 1960's ( or earlier ).



    Dave F.

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