Let's learn from our mistakes.

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ActingLikeAKid

Well-Known Member
It would be awesome if this thread got stickied, because I think - with participation - this could be REALLY useful. Here's my idea. Reply to this thread with your moments of 'THIS HAS ALL GONE HORRIBLY WRONG'. Whether it was forgetting to arm electronics, forgetting an o-ring, a paint mishap or just plain "well, that's not gone well"...

Let's post our worst moments. We've all had them. And as long as the wounds aren't too raw, I think that this is a huge educational opportunity, particularly for beginners; that's why I'm putting it here. Because I think that this would be immensely useful for a beginner browsing the forum, so they can say "Oh, wow. I never thought about _____, but now I'll never do that!"

-What happened
-Why it happened
-How (if) you recovered from the problem
-How (if) the problem could be prevented in the future.

(and mods - if this is has a better home in a different forum, feel free to shunt it wherever it belongs)

Because we've all been here:

ActingLikeAKid

Well-Known Member
And in the spirit of sharing, I'll start. A couple of nights ago I had two problems with my Wildman Punisher build:
https://www.rocketryforum.com/showt...-Punisher-quot-LDRS-Special-quot-Novice-Build

The first was because I got epoxy around the bottoms of the fins. This is the second time I've done this. New plan: When building a rocket with TTW (through-the-wall) fins, it's a common trick to leave off the rear CR (Centering Ring) so that you can put in internal fillets (glue to bond the root of the fin to the motor mount and the inside of the body tube). When the glue has cured, you can slide on the rear CR. Unless you were a little sloppy with the glue. If that's the case, even a millimeter-thick glob of epoxy will prevent the CR from seating properly. Solution: When you're doing internal fillets, wrap the bottom of the inside of the body tube and the bottom of the motor mount (just below where the fins touch) with masking tape. Then you can peel the tape off and not have this problem. Second problem is in a new post...

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TopRamen

SA-5
Mine was like three years ago on my first TLP Kit.
I attempted to install the baffle. I did it with Titebond II, and even though I got the TBII where it needed to go, or so I thought, I managed to have it bind up early, leaving like 4.5" for recovery gear.
I ended up eventually chopping the rocket up into it's sub-components, and will rebuild it properly someday.
I enjoy sharing my mistakes. It gives me the chance to teach something useful.

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Cabernut

Well-Known Member
Double check the orientation of BP motors while setting up for staging. in fact, double-check everything.

I taped the sustainer on backwards - probably because I was in a rush to get back to the pad before it went 'hot'

Ended in a powered lawn-dart. Thankfully only a motor mount needs repair.

Well, I'll never do THAT again!

ActingLikeAKid

Well-Known Member
...and this one was a doozy. I installed my Aeropack motor retainer ... backwards.

Making matters worse, I let the JBWeld epoxy cure overnight, so it was on there SOLIDLY.
After making some plaintive cries for help, several people suggested using heat to break the bond. But I don't have a blowtorch or a heat gun (one day. When I have a proper workshop. And a table saw and a router and...where was I? Oh. Right. So I needed to heat up the retainer to break the epoxy.

Glass-top stove works great for that. Cranked it up to high. Wrapped the bottom of the rocket in foil to protect it as much as possible. Rested the retainer on the burner for 10 seconds....pulled with pliers....20 seconds...pulled with pliers...30.....and we are back to square 1:

Some more suggestions from TRF got this back on track.

First, shockingly, JBWeld - the stuff that will hold together a cracked valve cover - can be dissolved with regular white vinegar. I soaked the bottom of the rocket in that for about 3 hours and that was enough to soften the epoxy on the MMT (motor mount) and the crud inside the retainer to the point that I could scrape away most of it with a popsicle stick.

Then it was time to clean up the motor mount with a Dremel -- even with the epoxy gone, it was still too thick for the retainer to fit on. This was part of the problem -- the side of the retainer with the threads is designed for the motor collar to slip inside, so it's a little bigger. The side meant to go on the rocket is smaller and has small ridges to help facilitate the bond. So after about 10 minutes of VERY careful dremel-ing, it looked like this:

and I wiped off the dust and

The retainer fit on the right way.

So here's what I learned from that:

-JBWeld can be broken with heat
-Listen to that voice that says "You're tired. Stop." I was about to turn it in for the night and thought "I'm so frustrated about this centering ring not fitting. I'll just slap on the motor retainer and that'll be a nice way to have something go right before I wrap it up". Part of me said "Just call it a night". I pushed it, and I paid for pushing it.
-Dremels are awesome.

ActingLikeAKid

Well-Known Member
Mine was like three years ago on my first TLP Kit.
I attempted to install the baffle. I did it with Titebond II, and even though I got the TBII where it needed to go, or so I thought, I managed to have it bind up early, leaving like 4.5" for recovery gear.
I ended up eventually chopping the rocket up into it's sub-components, and will rebuild it properly someday.
I enjoy sharing my mistakes. It gives me the chance to teach something useful.
Yeah, I was REALLY glad when I posted about what to use for the coupler on my PSII kits and everyone said "just plain old Elmers" - on a subsequent build (not a PSII kit) I saw JUST HOW FAST TBII binds. Great if you want something to stay in place quick, but if you don't......ouch

ActingLikeAKid

Well-Known Member
Double check the orientation of BP motors while setting up for staging. in fact, double-check everything.

I taped the sustainer on backwards - probably because I was in a rush to get back to the pad before it went 'hot'

Ended in a powered lawn-dart. Thankfully only a motor mount needs repair.

Well, I'll never do THAT again!
"This end should point toward the ground if you want to go to space"
https://xkcd.com/1133/

K'Tesh

OpenRocket Chuck Norris
TRF Supporter
A smart person learns from their mistakes... A REALLY smart person learns from other's mistakes.

TopRamen

SA-5
Yeah, I was REALLY glad when I posted about what to use for the coupler on my PSII kits and everyone said "just plain old Elmers" - on a subsequent build (not a PSII kit) I saw JUST HOW FAST TBII binds. Great if you want something to stay in place quick, but if you don't......ouch

When you start glassing, you will learn to make less mistakes.
You will still make them, but you will learn to share them frequently enough to make sure folks respect your effort!
Fragile parts are easy to make mistakes with.
Everything is so much more precise with composites. When was the last time you fitted plain balsa fins to an unfitted pre-cut tube and realized that you've already damaged your fragile kit parts?
Likely more recently than you'de like to admit. Don't worry, me too.
Then I discovered glassing and my constant use of a digital caliper.
I was just given a small battery operated scale by Cavecentral, so I can now do tenths of a Gram measurements!!!!
My sims can be accurate to a tenth of a Gram!!! I've never had such precision!!!
My Dreams and Nightmares are about to become very vivid indeed!!!
My whole Mind will require re-coding!
Durable, composite parts are hard to mess up, no pun intended.

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cavecentral

Well-Known Member
Some of this last year's building mishaps:

Building a RW Stinger (6" dia FWFG kit) I did the fins and internal fillets to find out after the thing is pretty much solid, that a fin tipped over to the side nearly an inch. I'm guessing it will spin or wiggle a bit when it flies. A lot of dremel work to try removing it, so I decided to leave it alone unless flights are bad enough to force me to fix it.

Second is a 3" WM Punisher. I made the normal ebay with a switch band in the middle of the coupler. Kit uses DD with the nosecone holding the chute and the eBay's coupler is the nosecone shoulder. There is an inch too much space that I need to fill with another switch band to close the gap since the coupler does not slide as far into the nose as it would a body tube.

dhbarr

Amateur Professional
On my first duration flight I went for "more is better" for everything. Went up on a b6-4, out came the 12" chute, and 3 mins later it was still drifting when it went over the treeline.

TL;DR: size your chutes, more is not better

El Phantasmo

Well-Known Member
Use the appropriate glue/adhesive, in the appropriate amount, within appropriate working times and leave for appropriate drying times.

Wood fins attached to cardboard tubes with plastic cement break off easily during landing and general handling. When I first started, I decided a tube of Testors plastic cement could do everything. Why not... it turned hard and was clear.

Appropriate amount.
This is especially important on plastic parts with solvent based adhesives.

Appropriate working time.
Sometimes you have to let the adhesive sit a little on part(s) before bonding, so it's not slick and runny when you put the parts together. Otherwise, you have extra paint prep work ahead of you. I'm looking at you, epoxy, on my "Lance Beta."

Appropriate dry/cure/set time.
Let the adhesive and parts set for the suggested amount of time before handling and stressing. I had a fin I thought was set (surface mount to the body tube), when I rolled the tube to place the second fin of 3, the first fin sagged. It didn't happen right away and it wasn't too bad, so I left it.

SCrocketfan

Well-Known Member
Three particular cases I've had (one actually didn't have any problems but was quite the lesson):

-Keep an eye on motor deploy charges/charge sizes, and look at redundancy or electronic deployment. I had a 3" fiberglass rocket (motor deploy only) lawn dart and wasn't able to find it despite hours of searching, likely either a delay failure (CTI Smoky Sam, and it was a very hot day) or somehow the component fit jammed something.

-If flying friction fit dual deploy, make sure the nose cone is well fit/taped! I once flew 4" cardboard Frenzy with friction fit/tape and the apogee event shook the nose cone loose-not enough to pull the main out though. Main charge fired... since the nose cone was off the chute didn't deploy. Thank goodness for redundant charges, the 2 gram backup chance was luckily enough to finish deploying the main. The same rocket now has shear pins and has deployed much more reliably.

I've also had good success with main deploy held in place with pieces of tape across the connection (cardboard coupler, cardboard payload+booster), but lots of tape is key.

-Also, don't rely on tape alone for non-tethered components. I had a modified LOC Vulcanite release it's payload of two water bottles (H waterloft competition) due to friction fitting the nose cone, so when you can use pins or rivets to secure components, definitely do!

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d11rok

Well-Known Member
I had a recent experience that will instill in me the patience of going through builds, regardless of how simple they are or how many you've done.

I picked up an E2x Estes heatseeker for my dad to build when he visited. I as well as my fiance were helping him with different bits of the rocket at the same time. The engine mount was fascinating and new to me, so I told my fiance to help dad glue the fins on, as they didn't appear to be TTW, but did have a small amount protrude through the body tube. Indeed, the instructions were on the table, but should I have to read through them first? Absolutely not, I says...I says...

I finally got the motor mount skeleton figured out (it is really fascinating , and is neat to look at if unfamiliar...almost comes built with fin dams). The fins on the body tube were nice and aligned. Dad completed the motor mount tube, and as I tried to install it, noted that the aforementioned fins tabs were indeed supposed to be installed into the noted fin dams made of plastic. Those fins were very much so glued in at this point. This build was doomed...an e2x build, for that matter! Bah!

The fix: I scalloped the aft body tube with 6 longitudinal cuts, creating 3 "fin tabs". The were abducted away enough to allow the motor mount to be shoved in correct position, with the fins now snapping into their place nicely. The rest of the build went OK, and the cuts were filled CA. I have yet to fly it, but it does look salvaged!

Morals of the story: read ALL instructions for EACH kit, regardless of its skill level or repetition. Do not rush any kit build, have fun and take your time, double checking instructions all along the way. Do not take for granted the simplicity of a kit...ever!

May you have a rocket hobby career full of errors, as those errors are how learning is achieved. However, stay away from the preventable ones as will be listed in this thread!

MaxQ

Tripoli 2747
Motors with snap rings...like Loki and Kosdon - so very simple.
You'd really have to be dumb to not assemble them correctly.
Except when you are in a hurry and someone is waiting on you to drag race.

I was in that situation...my opponent shall go unnamed. He posts here.

I did not listen for the "snap" of the ring and merely assumed it was properly seated...it was not.

The only thing worse than losing a drag race by having your rocket still sitting on the pad after his has taken off, is watching the roman candle display, shooting all the grains out the top.
Loki...makes a very pretty red.

JERRYR708

Well-Known Member
I papered all of my balsa fins, sanded all the edges of the excess paper off after drying over night. I started to apply CY glue along ALL edges of the fins. I wasn't supposed to CY glue the root edges because the Titebond II wood glue won't bond well to the CY glue for a strong adhesion.
I had to sand away the dried CY glue from all the fin root edges. I will pay more attention next time to prevent it from happening again. Easy fix though.

ActingLikeAKid

Well-Known Member
Painting:
Never use lacquer over enamel. Never use lacquer over enamel. NEVER use lacquer over enamel. And read and respect the drying times. Those are in good conditions. If it says "Dries to handle in 2-3 hours", you might get away in 90 minutes if it's 90F and dry and sunny.
Enamels generally say "Recoat within 60 minutes or after 48 hours" (or some variant on those times). RESPECT THOSE TIMES. I put some Appliance Epoxy paint on a rocket (my first time with it, it worked GREAT and produced a durable coat, so I tried it on another rocket. The first coat was a little light, so I gave it some more a few hours later. It was terrible. The paint peeled and flaked. But not all of it. And of course, Appliance Epoxy is meant to be super-durable, so sanding it off was really really difficult. I thought I'd try speeding the cure by putting it in a low oven - I'd heard somewhere that would work. NEVER DO THAT. The rocket was basically a loss. I let everything dry for a week, sprayed it with a different color, and let my kids play with it as a toy.
As for lacquer and enamel: Here's a weird mnemonic- The enamel goes on top - like the enamel on your tooth. Don't put lacquer on your teeth. Lacquer over enamel - I had a Photon Probe painted a beautiful white with Rusto enamel. I thought a section of purple with Testors One-Coat Purplicious would look great. It would. It did. Until the paint started bubbling and peeling and cracking. Lacquer thinner eats into enamel and the whole thing is a mess. The only thing to do is wipe/scrape/sand until you're down to a bare surface. Then wash it with lacquer thinner and prime it with a lacquer-based primer and THEN you should be OK.

As a rule, if you want to play with different paints, grab something made of the material you're painting and copy each step of your paint job. This also helps make sure that the paint's cured and is ready for another coat. So you want to do a red and silver paint job on a cardboard rocket? Cool. Sand a cereal box. Prime it with the rocket. Paint the box red with the rocket. Mask off some of the box and hit it with silver. Each step, make sure it looks OK on the cereal box before you do it on the rocket.

neil_w

Ennui poster child
TRF Supporter
Appropriate dry/cure/set time.
Let the adhesive and parts set for the suggested amount of time before handling and stressing. I had a fin I thought was set (surface mount to the body tube), when I rolled the tube to place the second fin of 3, the first fin sagged. It didn't happen right away and it wasn't too bad, so I left it.
In a similar vein, someone else recounted (not too long ago) returning to find a motor mount that had shifted while the epoxy was curing. I think I would invent several new expletives if that happened to me. Make sure assemblies are in a stable position and configuration while glue is drying or curing.

My own completely insignificant but nonetheless most embarrassing mistake was when I was prepping my Solar Warrior for my first launch as a BAR, and in my excitement completely forgot to hook up the clips to the igniter. So when it came my turn and the LCO called out "no continuity", I realized what I had (not) done and wanted to crawl into a hole.

Bat-mite

Rocketeer in MD
Two bad ones. I bought and built a Wild Man 2.6" Dark Star because I wanted to break Mach. The rocket was on sale for $99, but after all the "extras" it came to about$300.

Like an idiot, and for reasons that I really can't explain, I didn't ground test my charges. I also didn't use Duracells, since I honestly didn't know about the welded internal connectors.

So I launched it on a J1500 VMAC to over 8000 feet, did not get full ejection, and watched it lawn dart. It was completely destroyed. I hadn't even taken a picture of it. And although I know it went over Mach 1, I can't prove it. Lost the electronics in the crash.

My second worst mistake was losing this beautiful rocket because I was impulsive and wanted to launch it on an L935 even though the ground winds were around 15 mph. Turns out the winds aloft were more like 60 mph. But I launched it to over 9000 feet, and it went out of range of my GPS, and I never found it.

In all, I guess you could say I threw away nearly $1000 on those two losses. ActingLikeAKid Well-Known Member Two bad ones. I bought and built a Wild Man 2.6" Dark Star because I wanted to break Mach. The rocket was on sale for$99, but after all the "extras" it came to about $300. Like an idiot, and for reasons that I really can't explain, I didn't ground test my charges. I also didn't use Duracells, since I honestly didn't know about the welded internal connectors. So I launched it on a J1500 VMAC to over 8000 feet, did not get full ejection, and watched it lawn dart. It was completely destroyed. I hadn't even taken a picture of it. And although I know it went over Mach 1, I can't prove it. Lost the electronics in the crash. My second worst mistake was losing this beautiful rocket because I was impulsive and wanted to launch it on an L935 even though the ground winds were around 15 mph. Turns out the winds aloft were more like 60 mph. But I launched it to over 9000 feet, and it went out of range of my GPS, and I never found it. View attachment 293636 In all, I guess you could say I threw away nearly$1000 on those two losses.
Ouch.
One of the things I'm learning (and have not learned yet; see above re: JBWeld awfulness) is that when I have two voices in my head discussing rocketry, and one says "c'mon, GO FOR IT!!!" ....
LISTEN TO THE OTHER ONE.

Bat-mite

Rocketeer in MD
Ouch.
One of the things I'm learning (and have not learned yet; see above re: JBWeld awfulness) is that when I have two voices in my head discussing rocketry, and one says "c'mon, GO FOR IT!!!" ....
LISTEN TO THE OTHER ONE.
Trouble is ... that's what both of my voices say. :y:

dk54321

Active Member
If your rocket has an elastic shock cord, and you tie it to the nosecone, then add a drop of glue to the knot to keep it from coming untied, DON'T use CA. CA weakens or dissolves elastic, but holds it together long enough for you to finish building, prepping, and launching your rocket, waiting until ejection to fail.

jeff_j_black

Well-Known Member
Aerotech delay charges aren't interchangeable even if they physically fit! I used a 9 second delay from an 24/40 F39 motor in a 24/60 case with an F35 charge. Obviously I was hoping to get a 9 second delay out of the deal. Actually got a lot less of a delay and a zipper all the way down to the fin can. Don't assume that a delay can be used in a motor other that the ones it was intended for.

kcobbva

Mine was putting the fins on my Level-2. Thought they were tacked well on the MMT, and then pulled the fin guide and began the outer fillets (WAY TOO SOON). Walked back in an hour later and found the fins had drooped! PTL I was able to get them BACK into alignment and hadn't glued the rear CR in place yet; otherwise I would have been done. It's so easy to get excited building and wanting to go go go. I got caught up in that and almost bit me in the ....

Nathan

☢
TRF Supporter
Here's one from the Super DX3 that I recently painted. Before you decide that you have sprayed enough coats, take the rocket out in the sun and inspect it carefully. After spraying clear coat on my DX3 I realized that the color coat was uneven in some spots. Now I have to sand the clear coat and then spray another color coat.

ksaves2

Trouble is ... that's what both of my voices say. :y:
You forgot to take your meds that day then! :eyepop: Kurt

rstaff3

Oddroc-eteer
By far my worst case involved not connecting all the recovery components AND not listening to my wife (which is always a bad thing).

My RocketMan Freedom to Fly came with a very short harness. Evidently he thinks shorter is better vs the uber long ones that seem to be in style. I had decided to add a longer section. I was prepping the altimeter and connecting everything together. In front of me was a bunch of parts that had to be hooked together. As I started, she asked, "should that be hooked up"? Well, I was looking a few loose items and responded, "yes." I proceeded and her attention moved either to a conversation, the rocket dog, or whatever. I stuffed it all in and flew it. Unfortunately, she was talking about another connection that I overlooked. The phenolic tube shattered and was replaced to good old cardboard.

Checkists are good. Especially for us old people.

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ActingLikeAKid

Well-Known Member
If you have a chute release, bring the provided rubber bands when you launch. If you don't, a tied band wrapped in electrical tape MAY work. It did for me.

Well-Known Member
Walks up to pad. Tries to connect igniter.
"Hmm... this will probably work better if there's a motor inside."
Walks away from pad. But at least it's a safer stupid mistake than someone who brought a model to me while I was on RSO duty.
"What's the recovery device?"
"Parachute."
"Is it in there?"
"I think so."
"Let's have a look... OK, bring it back when the parachute is in there."

I once built a very short, fat rocket with a single launch lug somewhere near the CG, except for being 1 fat body tube's radius out from the centre. The rocket tried to take the launch pad with it, failed because the pad was pegged down, bound to the launch rod due to friction caused by the thrust being so far from the rod, eventually staggered off the pad, tipped over, and headed towards me. I had just enough time to consider the possibility of being the UK's first person to be injured by his own model rocket before the thing whizzed past.
Hint: on a short, fat rocket, have a couple of lugs spaced well apart.

There's a reason my launch controller key is tied to the launch rod cap. It means I can't launch a rocket with the cap still on the rod. Some other people who don't tie their keys to their launch rod caps haven't always been so fortunate.

jpbell

Well-Known Member
I forgot to put a launch lug on a rocket and didn't realize it until I got ready to launch it for its maiden voyage...not a deal break by any means but a huge disappointment when I realized it...