JB Weld

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SacEsq

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Recently picked up some of this stuff to use on a 29mm motor retainer. LOVED IT!

Was wondering a couple things:

1. Good to use on a fiberglass build?

2. Is it available in larger quantity? All I could find was the small 1oz tubes :(

THANKS
 
No, don't try to fiberglass with it. You really want to thoroughly wet out the cloth and leave as little extra as possible. Thus, thinner epoxy is warranted.
 
I am sorry I was not clear. I meant should I use it to construct a fiberglass kit.
 
Yes, it will work just fine to glue a fiberglass kit. It really is just high temp epoxy. In my last build I used it for securing the centering rings to the motor tube as well as for the fin root onto the motor tube. It is indeed available in several sizes. I buy the "industrial" packages that contain 5oz resin and 5oz hardener. I normally pay around $12.00 for that size.
 
I am sorry I was not clear. I meant should I use it to construct a fiberglass kit.
My bad. JB has been cussed and discussed several times here. One example: https://www.rocketryforum.com/showthread.php?35965-Alternative-to-JB-Weld&highlight=JB+Weld It appears JB Weld is run-of-the-mill epoxy with additives and its main attribute is thermal conductivity. I personally would only use it on the motor tube joints but it should work fine for the entire build. I find it harder to work with than others.
 
Thanks for all the replies. With that in mind what would you all suggest for fillets etc on a fiberglass kit.
 
I am not the most experienced here, but...

My original technique was
1. Run some masking tape along the fin and the body leaving the fillet area exposed.
2. Dam the ends with tape or clay.
3. Drizzle 20min epoxy along the fillet.
4. When the epoxy is stiff but not fully set, remove the tape.

I now make an ugly fillet with 5 minute epoxy and then build the outer fillet with SuperFil epoxy clay. This is basically epoxy mixed with some sort of microballons. Very easy to work with, light and sandable. You can mix microballoons into your epoxy on your own.

The balloons don't add strength. For high performance apps, other fibers are better. I don't need them for what I do.
 
I agree with Dick... My fillets certainly aren't pretty but I use the method that Crazy Jim has shown here before.

1) Grab a piece of 1/2" pvc pipe and a magic marker. Color around the end of the PVC pretty heavy with the marker and run it down the fillet area. This will leave the marks for the outer edge of the fillet. You will likely have to repeat this process several times for each fin.

2) Place your masking tape along these marks as well as around the airframe in front of and behind each fin.

3) I use 30 minute Bob Smith epoxy mixed 50/50 by volume with microballoons. This makes it nice and thick to about the consistency of peanut butter.

4) Drizzle epoxy into the fillet area and then pull along the fillet with the 1/2" pvc.

5) Pull the tape and let it setup.
 
Good clarification James. If you use straight epoxy, gravity forms them. With balloons or clay, you need to form them. I somehow had missed the magic marker trick....have to try and remember that one.
 
What James said. For good, easy to shape fillets use an epoxy and mix some filler into it. Microballoons are one choice, available from most hobby shops. Chopped fiberglass is another, available from vendors of West Systems and other brands of industrial strength epoxy. Of the two, the epoxy/chopped FG mix is said to make for very strong fillets as well as adding a bit of strength to the fin. Microballoons displace a fair amount of epoxy and thus lower the density and the weight of the resulting mix, as well as making the cured fillets easy to sand. The MBs don't add as much strength and since they take the place of some of the resin, some feel that they make less robust fillets than just using straight epoxy. But I have used that combination several times (though not on a fiberglass rocket) and it seems to hold up well without adding a lot of weight to the rocket. If I was building an FG rocket I might go with the other option that I mentioned.
 
Hey Jason,

What fiberglass kit are you building or planning to build?
 
Jason, I use RC Country (Bob Smith) 15 minute epoxy mixed with micro balloons (also sold at RC Country).

As others have noted above, you lay down masking where you want the edges of the fillets. Squeegee the mixed epoxy into place. Use a popsicle stick or a plastic spoon to scoop the excess epoxy out. When the epoxy is no longer flowing, remove the masking tape.

Bear in mind that the microballoons or other additives will make the epoxy harder to sand. If your fillets don't turn out as smooth as you like, you can always use glazing putty (bondo, 3M, etc) to finish them.

Wild Child, eh? That's gonna be a quick one off the pad.
 
Wildman Wild Child

Cool little rocket!:D If you don't get any instructions with the kit, look up almost any of the numerous build threads posted by CJ(Blackjack2564) and he has the fin fillet 'process' fully explained. Follow that and you will have fillets to be proud of!:wink:
 
Since we are discussing the Wild Child ... what is the common build method, lug or rail buttons? Attachment of buttons? I am leaning toward buttons but tossing around some ideas for attachment.
 
Jason, I use RC Country (Bob Smith) 15 minute epoxy mixed with micro balloons (also sold at RC Country).

As others have noted above, you lay down masking where you want the edges of the fillets. Squeegee the mixed epoxy into place. Use a popsicle stick or a plastic spoon to scoop the excess epoxy out. When the epoxy is no longer flowing, remove the masking tape.

Bear in mind that the microballoons or other additives will make the epoxy harder to sand. If your fillets don't turn out as smooth as you like, you can always use glazing putty (bondo, 3M, etc) to finish them.

Wild Child, eh? That's gonna be a quick one off the pad.

Yeah ... don't blink!!! October cannot get here soon enough ... it has been a productive off season ;)
 
Since we are discussing the Wild Child ... what is the common build method, lug or rail buttons? Attachment of buttons? I am leaning toward buttons but tossing around some ideas for attachment.

I haven't built the WildChild but have built the Darkstar Mini (same rocket with different fins). I used buttons and am happy with the choice. As for attachment, both are within the MMT area. I drilled and tapped the body tube and threaded the screw into it with a little bit of thick CA in the hole. Required a pretty short machine screw but I don't recall the exact length.
 
Yeah ... don't blink!!! October cannot get here soon enough ... it has been a productive off season ;)
Given the weather patterns of late and the dryness of the fields, I'm thinking November is soonest we'll be launching anything in NorCal. If you plan on going to the TCC October Skies, you'll get your chance to launch.
 
Drive down any hick town USA(Canada for that matter) and look at the pre-80s Chev or Ford with the exhaust stacks commin` up the back of the box.You see those welds around the couplers and muff clamps.? That ain`t MIG or even stick......that`s JB Weld !

JB rulzs.....yeee hawwwwwww !

Paul T
 
Bear in mind that the microballoons or other additives will make the epoxy harder to sand.
Well, I don't know about other additives, but adding in microballoons makes the hardened epoxy easier to sand. I have used this mixture many, many times for fillets.
 
Well, I don't know about other additives, but adding in microballoons makes the hardened epoxy easier to sand. I have used this mixture many, many times for fillets.

I definitely prefer microballoons for fillets - unless I need strength. Mirco Balloons are wasy to sand. Fumed silica is another story.
 
Given the weather patterns of late and the dryness of the fields, I'm thinking November is soonest we'll be launching anything in NorCal. If you plan on going to the TCC October Skies, you'll get your chance to launch.

Unfortunately, I'm thinking November too. You going to October Skies, Kit?
 
My boys and I, and possibly my father, will be going.
 
Thanks for all the replies. With that in mind what would you all suggest for fillets etc on a fiberglass kit.

structural Aeropoxy and West Systems colloidal silica. Thicken until it looks like peanut butter and it will spread perfect. Taping off the areas around the fillets will make cleanup easy and after they cure they require very little or no sanding.
 
I saw some inconsistencies of opinion above and wanted to point out that there are a couple different flavors of what we call "Micro Balloons".

Both behave more or less the same way as far as making thin epoxy thicker but once they cure up they are two different critters.

The colloidal silica (the white stuff) cures up very strong but is also harder to sand.

The phenolic filler (the brown stuff) cures less strong but is much easier to sand/form.



Micro Balloonz Resized.jpg
 
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