Rookie HPR mistakes

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Arpak

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Make a decent, thorough checklist and use it diligently. That way you won't look back at your rocket as you walk away from the pad and just happen to notice a bright red Remove Before Flight tag waving at you.
First flight after my L1, sure felt like I had egg on my face after that.
 

John Kemker

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doing all the prep, following the list, having a successful cert flight & many other flights.. Mighty proud & mighty happy!

But, feeling a little woozy on the way home.. and haven't pee'd since before you left..

Keep yourself hydrated! use sunscreen! wear a hat!
The Scene: NARAM 33
The Actors: Me, lots of LPR rockets, an Aerotech Arreaux and motors
The Weather: overcast

Drove to Chicago from Atlanta, stopping in Bowling Green, KY and staying the night with my maternal Grandmother. Flew rockets, visited vendors, bought my first HPR kit (NCR Phantom 4000) and reloadable casings. Spent the day out on the range having a blast (pun INTENDED). Stayed at a friend's house near the Hines VAMC. Woke up the next morning with a BAD case of sunburn. Who'd a-thunk that an overcast day would give you one of the worst sunburns you've ever had?

Drove back to Atlanta, staying at Grandma's house on the way back. That fall, went back to Bowling Green for her funeral. I was the last one in my immediate family to see her in person.

Dr. Wogz ain't jokin' folks: Wear sunscreen, even if it's cloudy!
 

ChicagoDave

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  • Forgetting to hook up the harness in the booster section and having to figure out some way to reach down a 3" diameter body tube. (Hint: Use a dowel, or have really long, skinny arms!)
  • Failing to add that little metal washer to the ejection well of a Aerotech DMS motor. (The ejection will go off, but blow out the back of the motor...leaving you to wonder what the heck you did wrong)
  • Pinching the O-ring on the forward seal disk of an Aerotech J570. (Quite entertaining, but not a good way to keep your rocket in one piece.)
  • Leaving your Jolly Logic Chute Release off after you tested it. (Only to remember as the rocket falls without the chute opening.)
  • Launching with your GPS receiver, only to find you are tracking your CAR and not your ROCKET. (Always verify that your distance to the rocket is increasing as you walk away, and you're tracking the pad, not your car or your house!!)
  • Forgetting to put on sunscreen in February when flying in a snow-covered field.
  • Forgetting to check the expiration date of the sunscreen you did put on in July. (Put on, but with no effect).
 

Bat-mite

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Who'd a-thunk that an overcast day would give you one of the worst sunburns you've ever had?
Actually, you don't feel the heat as much, so you don't realize you are burning. Very common to get burned on cloudy days.
 

kenstarr

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This is super awesome! I've had rocketry on the back burner for a few years and I'm headed to LDRS this year. I'm definitely going to get some checklist action going!
 

chilled

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Launching with your GPS receiver, only to find you are tracking your CAR and not your ROCKET. (Always verify that your distance to the rocket is increasing as you walk away, and you're tracking the pad, not your car or your house!!)
I'd add my own similar funny story to this:

- Forgetting to confirm your tracker receiver channel and ending up tracking someone else's rocket! As it turns out, I must have bumped the tracker channel on my Wildman tracker. Turned it on and started tracking. After a long walk, realized I had found someone else's rocket! Switched the channel and started over. luckily mine was not far off.
 

Michael L

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  • Forgetting to hook up the harness in the booster section and having to figure out some way to reach down a 3" diameter body tube. (Hint: Use a dowel, or have really long, skinny arms!)
I forgot to drill the hole and insert the eyebolt and kevlar in my LOC Graduator. 65mm ID. They make really long drill bits and I 3D printed a widget to hold the eyE of the bolt as I guided it down to the hole. Thankfully I caught the mistake before the aft bulkhead was epoxied in
 
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ChicagoDave

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I'd add my own similar funny story to this:

- Forgetting to confirm your tracker receiver channel and ending up tracking someone else's rocket! As it turns out, I must have bumped the tracker channel on my Wildman tracker. Turned it on and started tracking. After a long walk, realized I had found someone else's rocket! Switched the channel and started over. luckily mine was not far off.
Oh man.

Speaking of tracking... this was not me (for once) but one of the college teams.

Always verify you are tracking your rocket on the pad. The team verified the tracker on the prep table, but forgot to actually put the tracker in the rocket..... so they tracked the table after the launch. 😑
 

FlyBy01

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@FlyBy01 I think Plugger is referring to that fact some people think JB weld is the gods of glue, and will use it on their whole model.. Like, everything! including generous fillets!!
How would that differ from using 15 minute epoxy? I personally try to use Rocket Poxy on everything and Bob Smith 30 minute where I would have trouble getting Rocket Poxy.
 

Scott_650

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I think JB Weld is heavy from having metal in it.
It’s also kinda pricy compared to the BSI stuff.
Not to go too deep in the weeds on a glue tangent but JBW does have metal in the resin so it’s heavy (and pricey per unit) so using it to build your entire rocket would be a less than optimal choice. But it’s worked well for me to build motor adapters and attach screw on retainers.
 

mtnmanak

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Not to go too deep in the weeds on a glue tangent but JBW does have metal in the resin so it’s heavy (and pricey per unit) so using it to build your entire rocket would be a less than optimal choice. But it’s worked well for me to build motor adapters and attach screw on retainers.
@FlyBy01 I think Plugger is referring to that fact some people think JB weld is the gods of glue, and will use it on their whole model.. Like, everything! including generous fillets!!
Yeah, don't want to derail the thread with another glue thread, but I do use JB Weld for fillets on minimum diameter rockets. Those fillets can get super hot since the motor case is basically in contact with the root of the fin through the airframe. One of the reasons I build minimum diameter rockets is to use those awesome moon burners, which can burn for quite some time and really fry the fin can. Other than that, agree that JB weld is best left to bonding metal to your rocket.
 
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plugger

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Yeah, don't want to derail the thread with another glue thread, but I do use JB Weld for fillets on minimum diameter rockets. Those fillets can get super hot since the motor case is basically in contact with the root of the fin through the airframe. One of the reasons I build minimum diameter rockets is to use those awesome moon burners, which can burn for quite some time and really fry the fin can. Other than that, agree that JB weld is best left to bonding metal to your rocket.
If heating from the motor casing was an issue then one would expect your airframe to soften and fail before the fillets. It's also made with epoxy and is in direct contact with the casing.
 

John Kemker

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  • Failing to add that little metal washer to the ejection well of a Aerotech DMS motor. (The ejection will go off, but blow out the back of the motor...leaving you to wonder what the heck you did wrong)
  • Pinching the O-ring on the forward seal disk of an Aerotech J570. (Quite entertaining, but not a good way to keep your rocket in one piece.)
These are just two of the reasons I prefer snap-ring motors over screw-closure reloadables. However, that said, you do you. Just my preferences.
 

RobertH3

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JB Weld on min dia (and on rockets you are going to launch on a Metalstorm) = great idea. Metalstorm casings get hot enough to laminate the label into the MMT tube so they're sure as heck hot enough to soften normal epoxy. Added to the book

Cheers / Robert
 

mtnmanak

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If heating from the motor casing was an issue then one would expect your airframe to soften and fail before the fillets. It's also made with epoxy and is in direct contact with the casing.
At the end of the day, it is the same reason we use it on the retainers. Heat. Pretty much any epoxy will give you enough hold to keep the retainer on the rocket if it is cold, but JB Weld retains its hold even when it gets very hot.

Same principle for surface mounted fins on a minimum diameter rocket. The heat may not be high enough to go over the Fiberglass' Tg temperature, but it could get high enough to soften the epoxy on the fin mount and cause the fin to pop off. Combine that with the fact that I (and most people, it seems) like to fly their minimum diameter rockets at extreme speeds (Mach 2 or 3+), and JB Weld again seems to be the natural choice.

It is more of a "why not?" thing. If you have JB Weld and you are making a minimum diameter rocket and you know it is going to get hot, why not use an adhesive you know works well in extreme heat and is really thick, which makes excellent fillets? If you are building a rocket that cost hundreds of dollars, are you really going to skimp on the fillets?
 

chilled

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Oh man.

Speaking of tracking... this was not me (for once) but one of the college teams.

Always verify you are tracking your rocket on the pad. The team verified the tracker on the prep table, but forgot to actually put the tracker in the rocket..... so they tracked the table after the launch. 😑
Ouch.. For added comfort these days, if there is room, I always fly with a Featherweight GPS and then just throw the Wildman tracker in anyways.
 

kenstarr

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Just had a thought. It didn't hurt too bad.... I was thinking about how many times experience and confidence get someone into trouble, and our previous checklist comments. Look into the book 'Checklist Manifesto' by Atul Gawande. I haven't read it but I remember talking about it at work. Aircraft pilots use checklists. Why hasn't the medical profession? Here's an article about it
https://www.npr.org/templates/story/story.php?storyId=122226184
-Ken
 

FlyBy01

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Just had a thought. It didn't hurt too bad.... I was thinking about how many times experience and confidence get someone into trouble, and our previous checklist comments. Look into the book 'Checklist Manifesto' by Atul Gawande. I haven't read it but I remember talking about it at work. Aircraft pilots use checklists. Why hasn't the medical profession? Here's an article about it
https://www.npr.org/templates/story/story.php?storyId=122226184
-Ken
Yes, as a professional pilot we are required by policy and law to use a checklist. I will be developing several for my needs and most of the folks in my club use one.
 

Neutron95

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Not using shear pins. I was using cable cutter dual deploy, and it separated somewhere around Mach 1.
20210611_123140.jpg
 

plugger

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At the end of the day, it is the same reason we use it on the retainers. Heat. Pretty much any epoxy will give you enough hold to keep the retainer on the rocket if it is cold, but JB Weld retains its hold even when it gets very hot.
I disagree. In my opinion most people use it on retainers because they're metal and JB Weld is an high temp epoxy system designed for bonding metal. I've stopped using JB Weld for affixing motor retainers and instead now use a standard structural epoxy and they don't fall off mid flight/post motor burn. NFPA 1125 states motor casings can't exceed 225 deg C (+/- 5 C), which a good epoxy system can easily withstand.

Same principle for surface mounted fins on a minimum diameter rocket. The heat may not be high enough to go over the Fiberglass' Tg temperature, but it could get high enough to soften the epoxy on the fin mount and cause the fin to pop off. Combine that with the fact that I (and most people, it seems) like to fly their minimum diameter rockets at extreme speeds (Mach 2 or 3+), and JB Weld again seems to be the natural choice.
Mach 2+ flights incur heating (primarily) on the nose cone and the leading and trailing edges of the fins. In comparison, the fin fillet does not see anywhere near the aerodynamic heating effects. And once again, if motor casing heating was an issue for a composite airframe it would soften the airframe/motor mount first, not the fillets on the other side (and therefore insulated from) the motor casing. Also, most people that I know that fly MD and are looking to hit extreme speeds don't use a motor retainer full stop as the retainer 'step' induces unwanted drag. Better to use an internal motor retention system that doesn't induce drag.

It is more of a "why not?" thing. If you have JB Weld and you are making a minimum diameter rocket and you know it is going to get hot, why not use an adhesive you know works well in extreme heat and is really thick, which makes excellent fillets? If you are building a rocket that cost hundreds of dollars, are you really going to skimp on the fillets?
Because it's not necessary or fit for purpose. It has a specific use case, bonding metal; beyond that there are better systems out there (ProLine 5400 and EpiGlue come to mind) for fin fillets.
 

mtnmanak

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I disagree. In my opinion most people use it on retainers because they're metal and JB Weld is an high temp epoxy system designed for bonding metal. I've stopped using JB Weld for affixing motor retainers and instead now use a standard structural epoxy and they don't fall off mid flight/post motor burn. NFPA 1125 states motor casings can't exceed 225 deg C (+/- 5 C), which a good epoxy system can easily withstand.



Mach 2+ flights incur heating (primarily) on the nose cone and the leading and trailing edges of the fins. In comparison, the fin fillet does not see anywhere near the aerodynamic heating effects. And once again, if motor casing heating was an issue for a composite airframe it would soften the airframe/motor mount first, not the fillets on the other side (and therefore insulated from) the motor casing. Also, most people that I know that fly MD and are looking to hit extreme speeds don't use a motor retainer full stop as the retainer 'step' induces unwanted drag. Better to use an internal motor retention system that doesn't induce drag.



Because it's not necessary or fit for purpose. It has a specific use case, bonding metal; beyond that there are better systems out there (ProLine 5400 and EpiGlue come to mind) for fin fillets.
Well, you do you.
 

OverTheTop

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I agree that JB has its uses, but it is used where other epoxies would be a better choice in a lot of cases. Plugger's post is quite valid IMHO.

I have used it in fewer and fewer situations in HPR as I evolve as a rocketeer.

My daughter has a pie warmer at the bakery she works at that needs some JB for a repair this week ;).
 

mtnmanak

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I agree that JB has its uses, but it is used where other epoxies would be a better choice in a lot of cases. Plugger's post is quite valid IMHO.
Absolutely valid. Everyone has their own techniques. I like to use JB Weld for fillets on minimum diameter rockets and he doesn't. Neither is "wrong" and many techniques work in this hobby. He'll do him, and I'll do me and we will all fly happily together.

Maybe that is the appropriate connection to this thread - everyone has a technique and many will work. Do what works for you.
 

Steve Shannon

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I disagree. In my opinion most people use it on retainers because they're metal and JB Weld is an high temp epoxy system designed for bonding metal. I've stopped using JB Weld for affixing motor retainers and instead now use a standard structural epoxy and they don't fall off mid flight/post motor burn. NFPA 1125 states motor casings can't exceed 225 deg C (+/- 5 C), which a good epoxy system can easily withstand.
Snip
I snipped much of your post because I agreed wholeheartedly. I just wanted to add that the method for measuring external case temperature during certification involves multiple data averaged which in practice could result in temperatures at the nozzle exceeding 225° C, especially on end burner configurations. For that reason I will continue to use JB Weld on my retainers. Perhaps it’s a false sense of security, but I’ll take anything I can get this year. 🚀
 
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