Need help figuring out why my 1:100 Saturn V launch was a catastrophic failure

Discussion in 'Low Power Rocketry (LPR)' started by Darren Nolan, Feb 10, 2020.

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  1. Feb 12, 2020 #31

    neil_w

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    I’m not saying you’re wrong, but this is a skill level 5 kit we’re talking about here.
     
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  2. Feb 12, 2020 #32

    3stoogesrocketry

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    Exactly my point . Why would they design a skill level 5 rocket that needs to be lifted 20cm off the blast deflector to fly? They could have easily enlarged the fins 10% and had the motor at the back where it belongs , not 1 caliber up inside the airframe.
     
  3. Feb 12, 2020 #33

    Nytrunner

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    Then it wouldn't look like a scale Sat5
     
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  4. Feb 12, 2020 #34

    Brian H.

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    As far as Estes customer service is concerned, I had an E9 Cato in a Mega Mosquito. I wanted to simply report the Cato with no expectations, explaining that the 5 year old motor was second hand and had no idea about prior handling or storage. They sent me replacement motors and my choice of replacement kit due to the Mega Mosquito being out of stock.

    I will recommend Estes to anyone for low power rocketry.
     
  5. Feb 12, 2020 #35

    Brian H.

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    As a side note, also being in customer service, if we had a giant warning on everything deemed critical, the entire instructions would be a giant warning.
     
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  6. Feb 12, 2020 #36

    KilroySmith

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    I felt bad when I contacted Estes. Messed up the big sticker on a Mega Der Red Max, and contacted them to see if I could buy a new one. My understanding on the phone was that, no problem, I'd get a new one in the mail. I assumed that "new one" meant a new sticker sheet; instead a brand new MDRM box showed up on my doorstep. One of the kids in the Rocket Club I was helping with got to build that one; boy was he happy.
     
  7. Feb 12, 2020 #37

    cerving

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    Yeah, Estes customer service is pretty darn good. Had an E12 cato and destroy a Vagabond a few years back, they told me that they couldn't send me the motors because of shipping regulations, but they happily replaced the Vagabond AND gave me a second rocket equal to the price of the motors. No complaints here.
     
  8. Feb 12, 2020 #38

    samb

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    In the title of this thread the OP asked for help determining why his launch failed. Based on his description and the video I provided an answer. Any model will experience some degree of Bernoulli lock if the motor is sitting on the blast deflector at ignition. That’s effectively what happened here IMO. The Estes 1/100 Saturn V has had that recessed motor mount for 30 years ? 40 ? Time for a redesign ? IDK
     
  9. Feb 12, 2020 #39

    SammyD

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    Truth dat! On a side not, and in NO way aimed at the OP as he realizes his mistake, I sometimes I think we should take ALL warnings off everything and let natural selection take its course... :-\
     
  10. Feb 12, 2020 #40

    ebruce1361

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    My two cents worth: The 1/100 Saturn V is WOEFULLY underpowered on single E12s or even E15s. When I built mine, I modified the motor mount to be a cluster of five D12s. I had the opportunity to essentially do a side-by-side comparison the day I launched mine with another modeler who built his stock. His wobbled and struggled to get altitude whereas mine had solid thrust and went straight up. Unfortunately, my complicated motor arrangement led to a mixup that resulted in the motor tubes being damaged and a premature deployment, but that's another issue altogether. (If you want to read the details, I made this thread about it: https://www.rocketryforum.com/threads/estes-1969-saturn-v-a-cautionary-tale.156916/ )
    Anyway, I'm sorry to hear your rocket suffered such damage @Darren Nolan. No matter how experienced we modelers are, there's always something we've never seen before that can destroy a rocket. I'll be honest, I knew about the problem of motors being inserted too far into a body tube causing a loss of thrust due to the exhaust gasses not being permitted to expand properly (Krushnic Effect), but I had never heard of Bernoulli Lock until this post. Here's hoping you can salvage quite a bit and rebuild. If you do decide to rebuild, may I suggest considering clustering or switching to a 29mm mount so you can get some better thrust and stability.
     
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  11. Feb 12, 2020 #41

    Bat-mite

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    I find that with a lot of bigger Estes kits, they don't really fly well on BP motors. Need more thrust. I flew mine with an At E20 successfully.
     
  12. Feb 12, 2020 #42

    new2hpr

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    Maybe the customer service question should spin off to a separate discussion, since OP got his answer as to what likely happened.
    In support of JumpJet, however, companies with excellent customer service can be abused. If Estes can afford to do this, great, but it just results in potentially higher prices for the rest of us, to compensate. Costco used to have an EXTREMELY liberal return policy. We had a friend of ours (no longer a friend) who bought a TV, used it for over 2 years, then returned it for full refund as she didn't want it. Costco didn't even blink or ask questions, just gave the refund. Not much later, they made their policy much tighter, though still reasonable and better than most.

    I think OP did the right thing to contact Estes to report the missing statement on his instructions, and I don't think he's expecting compensation for his loss. It wouldn't surprise me for Estes to do so, though. We might think "hey, why don't they just give him the parts needed to rebuild, and a new motor", but it's far cheaper and easier logistically to send him a new kit and have a happy customer who will keep spending his money with them.

    -Ken
     
  13. Feb 12, 2020 #43

    rcktnut

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    I've never built one, but looked at the directions for the mmt. From what I see the mmt is inserted into the body tube that far to accommodate the display nozzles and would of course also allow for better CP/CG relationship. Does bringing the mmt further aft make the rocket unstable? I would think that the BT on its own without more protection would be toast after a few launches due to the Krushnic Effect.
     
  14. Feb 12, 2020 #44

    neil_w

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    There is a lot of egregious abuse of Costco's return policy. I don't know how people live with themselves.
     
  15. Feb 12, 2020 #45

    ebruce1361

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    Yes, the motor mount is designed like that to accommodate the display nozzles, but I feel like the display nozzles could easily be redesigned to attach to motor mount in that are much further back. I will say that the Krushnic Effect doesn't seem to be too big of a problem because of the cuts made between the fairings, but the CG would move aft if the mounts were moved, necessitating more nose weight.
     
  16. Feb 12, 2020 #46

    kuririn

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    I believe the reason the motor mount is recessed like that is so that the display nozzles will fit correctly.
    Might also help to push the CG forward.
    Estes has done their due diligence in posting a warning to elevate the model at launch off the deflector pad.
    It is incumbent on the consumer to read all instructions and adhere to them.
     
  17. Feb 12, 2020 #47

    kuririn

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    +1. I saw a talk show a few years ago where some kids were bragging about how they would buy an expensive outfit, wear it to a special event like a prom, then return it to the store the next day for a refund.
    Locally some people would stock up on cases of bottled water when there was a threat of a hurricane. When the threat passed they would return the cases to the store for a refund. ALL the stores here have since amended that to no returns on bottled water.
    Some people's children. Tsk.
     
  18. Feb 12, 2020 #48

    SecondRow

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    Krushnic is not an issue because the motor mount is not recessed more than 1 caliber. The issue is Bernoulli lock. But get the rocket off the pad and it won’t be a problem.

    Built to spec, the Estes Saturn V flies just fine on the recommended motors. I’ve flown mine on E12s, E15/E20s and E30s with no problems.
     
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  19. Feb 12, 2020 #49

    Greg Furtman

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    I had to look up the Krushnic Effect. Here's a short video that explains it very well.
     
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  20. Feb 12, 2020 #50

    AfterBurners

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    If you built it accordingly to the kit instructions I would contact ESTES and see if they can explain it to you. Ihave no idea why your rocket launched the way it did. It looks like you followed the instructions.
     

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