What's the problem with JB KwikWeld?

[billdz]

Just curious, the instructions for the AeroPack 75mm retainer say to secure the retainer to the motor mount with JB Weld. However, they also say specifically only to use "standard cure" JB Weld, "Do not use fast cure." What's the problem with the fast cure JB KwikWeld, isn't it the same bond, just a faster cure?

 

[Titan II]

Let Google be your friend....there is a significant difference.

JB Weld
Properties (lbs/psi)
Tensile Strength: 3960
Adhesion: 1800
Flex Strength: 7320
Tensile Lap Shear: 1040
Shrinkage: 0.0%
Resistant to 500º F

JB Kwik
Properties (lbs/psi)
Tensile Strength: 2100
Adhesion: 1800
Flex Strength: 7320
Tensile Lap Shear: 1040
Shrinkage: 0.0%
Resistant to 300º F

 

[rharshberger]

The most important difference as far as we are concerned for motor retention is the temperature, iirc the the quick version can soften and fail during the flight.

 

[CORZERO]

I use Aeropoxy on all my retainers. Never had a problem. Paper, blue tube, fiberglass, no issues up through L motors. Another one of those myths, the "heat" issue, I believe.

 

[dhbarr]

I use Aeropoxy on all my retainers. Never had a problem. Paper, blue tube, fiberglass, no issues up through L motors. Another one of those myths, the "heat" issue, I believe.

NFPA 1125 7.4.1
A solid*propellant rocket motor shall be*designed*and*constructed*so that the*
temperature*of the*external surface*of the*rocket motor casing*and*fittings, if any, shall not*
exceed*200°C (392°F) during*or after*operation.

That's a pretty tremendous Tg/Tm. PTM&W ES6296 is a high temp, with Tg between 119C and 143C. JBW on the other hand makes a claim for continuous operation at 260C.

 

[CORZERO]

NFPA 1125 7.4.1
A solid*propellant rocket motor shall be*designed*and*constructed*so that the*
temperature*of the*external surface*of the*rocket motor casing*and*fittings, if any, shall not*
exceed*200°C (392°F) during*or after*operation.

That's a pretty tremendous Tg/Tm. PTM&W ES6296 is a high temp, with Tg between 119C and 143C. JBW on the other hand makes a claim for continuous operation at 260C.

Cool. So I guess it's a good thing I don't glue my retainers directly to my motor casings.

 

[dhbarr]

Cool. So I guess it's a good thing I don't glue my retainers directly to my motor casings.

Didn't realize you were wrapping your motors in insulation, my mistake. :-D

 

[rharshberger]

I use Aeropoxy on all my retainers. Never had a problem. Paper, blue tube, fiberglass, no issues up through L motors. Another one of those myths, the "heat" issue, I believe.

NAR standards (I believe they are NFPA standards) require that the motor not reach more than 200C (392F) during the firing process, a motor (most likely a long burn type) could possibly approach that temp (392F) possibly leading to epoxy failure, with the regular JB Weld the epoxy has a temp resistance of 108F above that, whereas the Kwik version would potentially fail at 300F or 92F below the max allowed by the motor certs. While not likely, there is a reason Aeropoxy recommends JB Weld.

Aeropoxy, West, and US composites iirc don't list temp resistance on their data sheets, the below link is one for a thread I put together for epoxy comparisons.

https://www.rocketryforum.com/showthread.php?138953-Epoxy-Comparisons-and-Technical-Data-Sheets

 

[CORZERO]

Didn't realize you were wrapping your motors in insulation, my mistake. :-D

I'm surprised an amateur professional such as yourself doesn't consider fiberglass, paper, phenolic and other motor mount materials as insulation...

 

[billdz]

Thanks for the replies. As Titan II says, a significant difference indeed.

 

[jyawn]

Heat failure is not a myth. A few years ago I observed an L2 launch with an odd failure. The Aeropack retainer had come off the rocket upon landing. Funny... shouldn't it have come off at ejection? Driving home, I reviewed the scene, and recalled that the glue used to secure the retainer was CLEAR. Clearly not JB Weld. Theory now is that it took a little time for the heat to migrate to the retainer. Flyer was irate, claiming that it had been a successful flight up until that point, but the prefect stood his ground, maintaining that the motor had to be retained for the full flight, including landing. When I started using AeroPack retainers, I was curious as to why the manufacturer was adamant about using JB Weld. I think it would be good if they explained it, rather than just saying "you have to..." Smart people want to know why.

 

[llickteig1]

I use Aeropoxy on all my retainers. Never had a problem. Paper, blue tube, fiberglass, no issues up through L motors. Another one of those myths, the "heat" issue, I believe.

No.

Another example of why the *opinions* on this forum are just that. I have personally witnessed the failure of the bond between Aeropack and motor tube with a West Systems bond.

The manufacturer says use JBWeld - saving a few cents by using regular epoxy or JBKwik is out and out stupidity.

 

[OregonBAR]

billdz - thanks for the post, as I hadn't realized there was actually two different types of JB Weld. Upon checking my supplies, I do in fact have the Kwik type... Since I'm planning my next project with a long-burn motor, it's a good thing to know. Thanks again for posting!

 

[cavecentral]

I've used JBW and JBQ. JBQ only on 2-3 of them. I never knew there was a difference other than timing. Good to know. Luckily, I bought only 1 tube of JBQ.

 

[ksaves2]

Ummmmmmm. "In a pinch", if one has some Cotronics 4525 or 4525IP already mixed up for something else, it likely could be used without issue!! https://www.cotronics.com/catalog/05 4525 4525IP.pdf
:wink::lol: Errrrr, J&B from Walmart though is a heck of a lot cheaper though. Kurt

 

[DeepOvertone]

I wanted to give you guys a video to watch. Beyond the heat resistance, the difference in strength is pretty eye opening as well. https://youtu.be/XObmZIbHOzY


Sent from my iPhone using Rocketry Forum

 

[BalDave2]

Heat failure is not a myth. A few years ago I observed an L2 launch with an odd failure. The Aeropack retainer had come off the rocket upon landing. Funny... shouldn't it have come off at ejection? Driving home, I reviewed the scene, and recalled that the glue used to secure the retainer was CLEAR. Clearly not JB Weld. Theory now is that it took a little time for the heat to migrate to the retainer. Flyer was irate, claiming that it had been a successful flight up until that point, but the prefect stood his ground, maintaining that the motor had to be retained for the full flight, including landing. When I started using AeroPack retainers, I was curious as to why the manufacturer was adamant about using JB Weld. I think it would be good if they explained it, rather than just saying "you have to..." Smart people want to know why.

No.

Another example of why the *opinions* on this forum are just that. I have personally witnessed the failure of the bond between Aeropack and motor tube with a West Systems bond.

The manufacturer says use JBWeld - saving a few cents by using regular epoxy or JBKwik is out and out stupidity.

Interesting we don't see the same failure with gluing the fin to the MMT using West Systems, U.S. Composites, etc.

 

[rharshberger]

Interesting we don't see the same failure with gluing the fin to the MMT using West Systems, U.S. Composites, etc.

I am guessing two things here, A) the mmt does act as additional insulation, and B) the retainer is in direct proximity to the hottest part of the motor- the nozzle.

 

[billdz]

The KwikWeld package says "World's Strongest Bond". Guess that's a bit of deceptive advertising.

 

[CORZERO]

No.

Another example of why the *opinions* on this forum are just that. I have personally witnessed the failure of the bond between Aeropack and motor tube with a West Systems bond.

The manufacturer says use JBWeld - saving a few cents by using regular epoxy or JBKwik is out and out stupidity.

Not an argument.

My post was not an opinion, but rather anecdotal evidence. Check your definitions before casting pejoratives. I'll just leave that mess of a response of yours at that.

 

[OregonBAR]

The KwikWeld package says "World's Strongest Bond". Guess that's a bit of deceptive advertising.

:rofl:

 

[samb]

FOOD FIGHT !!! ... oops, I mean ..... GLUE THREAD !!!

FWIW, I follow the manufacturers instructions just because they said so.

 

[cbrarick]

Gotta use super titebond. It enjoys a post cure heat cycle.

Man I love these glue threads :>

 

[solid_fuel]

Elmers white glue on everything!

 

[G_T]

One should make sure that the sarcasm comes through correctly in threads like this. Someone might actually believe what is posted... No, white glues and yellow glues are completely unsuitable. Most epoxy choices that you might have around are completely unsuitable. Superglues are extremely unsuitable. Polyurethane glue might be fine as it can take a high temp if it is the right type. Cotronics is probably fine as well. But JB Weld is readily available and works for the job.

The temperature that a motor mount can be exposed to in some cases is far beyond the values mentioned here so far. If the diameter of the motor and the diameter of the rocket are the wrong mix, then a vortex can form at the base of the rocket pulling some of the hot gasses up around the bottom of the rocket in a vortex of sorts. I've had a layer of epoxy coated and painted (high temp paint at that) plywood burned right off the bottom with an 88mm EX N motor in about 3.5 seconds. Retention was not one of these mounts, thankfully. Funny, a 114mm EX O with about a 4.5 second burn in the same rocket with very similar propellant only left a layer of soot. When you get a vortex, it can really cook the back end of the rocket in a hurry.

Gerald

 

[Lugnut56]

Has anybody ever performed a stationary burn and checked the MM temp with an infrared thermometer? I realize the air flow won't be identical to an actual flight, but it should be fairly close.

 

[blackjack2564]

Not a stationary burn, but actual flight.
I had temp strips at both ends of motor 98mm N-1000. 17sec burn.
6in rocket, 98mm motor mount.

After flight they had registered 188c [370f] at the top & 202c [395f] at the nozzle end.
It took over hour to locate the 18,000ft+ flight. The motor and Aero-Pac were still so hot, it was very uncomfortable to unscrew & remove. The mm & airframe acted as insulators, after motor removal, it was cool to touch by time we got back to camp 15-20 min.
The heat was at the limit of the case rating, no discoloration shown in anodizing.
Of course 98 & most 75 motor retainers are bolt on due to this.

On smaller motors 38-54mm.... heat should only be a serious issue on long burns,/ due to heat soak.
With EX motors, all bets are off.

As Gerald mentions, there are cases where base drag/vortex's can cause heat damage and heat soak. I find it on 4in rockets with 54mm mounts and 3in rockets with 38 mounts. Probably [don't know for sure] from the smoke/delay grain burns which can be 10-17 seconds long, more so than motor burn time.
This heat from delay grain burn is often overlooked, but there. To exacerbate the issue, if rear CR is recessed in airframe 3/4to 1 inch that heat get sucked up into that recess and things get REALLY hot. In my case burning paint off & even a layer or 2 of the G-10 ring.
There is no one size fits all, in rocketry.
One forgets that the liner is burnt, no longer giving much insulation to case, from the fire/heat of burning smoke/delay grain.
As time went on, [for me] I put an extra CR aft & flush with rear of airframe which helps a great deal. I also smear/coat that CR with JB.

Now all flights, [other than small motor 38mm sport] are done with plugged closure & no delay/smoke grains.
Problem solved.................

Having been flying high power now for many years [15], I have seen problems mention with retainers coming loose. Things like this always bite you in the a$$, when you least suspect them & rocketry in general is best served, by following directions, if for no other reason than safety. It only takes one screw up to ruin it for everybody & I don't want to be THAT guy..JB for me.

Yes, one can get away with using normal epoxies some of the time, BUT that one time when you least expect it...you will get bit! After all it's only a rocket...what can go wrong? LOL:smile:

 

[billdz]

I put an extra CR aft & flush with rear of airframe which helps a great deal. I also smear/coat that CR with JB.

Yes, JB on the aft CR. The instructions say to use JB Weld for the retainer. I was wondering whether the aft CR also could benefit from JB.

 

[jsdemar]

Oh, a glue thread!

One more vote for JBWeld. The aluminum thrust ring on my P10,000 6" motor was glued directly to the motor. 6-sec burn and it lifted the 200# 2-stage stack.
https://photos.app.goo.gl/c4fRlc5aIf8JiIFB2

I have anecdotal evidence that masking tape will work just as well. ;-)