JB weld for FG assembly?

[Off Grid Gecko]

JB can be used for fillets and smooths out ok from what I remember. I generally use West Systems these days for fillets, filled with Q-cell microballoons. Much lighter than JB. They sand a LOT easier too.

One of the reasons I like it is for the easy sanding, so the West Systems stuff must be some kinda Heaven. I'll likely order some of their goop when I start my L2 build, as everyone seems to like them. Pretty fairly priced too, I assume. The microballoons also, one day I will need to give them a try. I'm not sure why I'm timid about ordering glue, cause I can find none of this stuff local, but one of these days. Can epoxy ship USPS?

 

[Philip Tiberius D.]

For fillets, I remember Crazy Jim recommended pvc sprinkler pipe of appropriate diameter and wet in alcohol.

His other trick was to wipe the sides of the pipe tool with felt tip marker and drag it along the fin where you want the fillet. The marker ink will transfer to the body tube and you lay down the edge of the tape along that line.

Been using Jim's tips for years. He's a pretty clever country boy.

You can achieve the same thing with a pencil and paper... scribble a fairly dark area the length of your fin root, lay the paper scribble side down and drag whatever you use to produce fillets along the back of the paper. It will leave markings on the fin/body you can tape off.

 

[Greg Furtman]

One of the reasons I like it is for the easy sanding, so the West Systems stuff must be some kinda Heaven. I'll likely order some of their goop when I start my L2 build, as everyone seems to like them. Pretty fairly priced too, I assume. The microballoons also, one day I will need to give them a try. I'm not sure why I'm timid about ordering glue, cause I can find none of this stuff local, but one of these days. Can epoxy ship USPS?

@Off Grid Gecko You'll like it. I've been using WEST System products for over 30 years. It isn't exactly inexpensive but it always give good results and it has a very long shelf life. 105 Resin, 205 Fast Hardener, mini pumps to make your life easier, and 407 Low-Density Microballoon Filler.

https://www.amazon.com/System-Epoxy...y&qid=1593264488&sprefix=WEST+,aps,212&sr=8-6

https://www.amazon.com/WEST-System-...eywords=west+system+407&qid=1593264831&sr=8-1

 

[beeblebrox]

Personally I don't like JB Weld, but, If you insist on using alot of it, the big tubes'll save you about 40% of your dough...https://www.amazon.com/J-B-Weld-828...sr_1_4?keywords=jb+weld&qid=1578919848&sr=8-4

I have just tried this stuff...It's extremely strong. $25/8oz
https://www.systemthree.com/products/silvertip-metlweld-metal-bonding-epoxy

 

[OverTheTop]

@OverTheTop Are you familiar with the location & history of the Keweenaw Range?

I have seen some pics of the area and it does look like a pretty spot. Traveled quite a bit in USA and Canada but never made it there yet. I have read about the Keweenaw Range history, even through a local government archive somewhere.

 

[Chad]

Definitely gloves. I always wear gloves when working with any epoxies ... 5mil nitrile gloves are about $0.05 each and in my opinion well worth mitigating the risk of developing a sensitivity to epoxy.

As for smoothing / shaping fillets ... I picked this up from a post here on TRF a couple years ago. Cake decorating tools! I mask my lines, fill, and pull the fillet with these. One pass to shape and then dip the ball in denatured alcohol and one more pass to smooth. Works like a charm! I use for wood glue also, but no alcohol dip there...

https://smile.amazon.com/dp/B0771DY1LK/ref=cm_sw_r_cp_apa_i_opghEb4KESGXN

this is a great find, fillets are my least favorite part of a build. I use the pvc tube method which works fine but gets awkward because you have to keep it at the right angle. The fondant tools don't have the right dimensions for a build coming up for me but i found you can order delrin/nylon balls of various diameters pretty cheaply. I'm thinking of getting some, drilling a hole, and gluing in a dowel.

edit: if anyone has a way to make perfectly repeatable fillet tips i'm all ears. it bugs the hell out of me to have fillets of different shapes.
/sorry for the threadjack

 

[David Schwantz]

The best way I have ever done it is with my finger. Index finger just wiped over a bead of glue. After you have done if enough you can get pretty good at how big of a bead to lay down first. The angle you hold your finger at will control fillet size. Also, bigger finger makes bigger fillet. No need to tape and very little sanding is needed. In the matter of a minute I can have the fillets facing each other on fins done. Best glue for me is Hysol 9462. Will not run or drip.

 

[lakeroadster]

FG? What are you referring to? Rocketry Glossary

Update: Fiberglass

 

[Off Grid Gecko]

this is a great find, fillets are my least favorite part of a build. I use the pvc tube method which works fine but gets awkward because you have to keep it at the right angle. The fondant tools don't have the right dimensions for a build coming up for me but i found you can order delrin/nylon balls of various diameters pretty cheaply. I'm thinking of getting some, drilling a hole, and gluing in a dowel.

edit: if anyone has a way to make perfectly repeatable fillet tips i'm all ears. it bugs the hell out of me to have fillets of different shapes.
/sorry for the threadjack

If there is a feed store or tractor store near you and you haven't already, you might want to check that out. They typically have a long hardware aisle with just about every widget you could hope for. Lots of derlin parts (screws, nuts, odd shapes), funiture fasteners like you typically only see when you buy a cabinet or something, tiny hinges, weird rails, little hooks and clips, lengths of steel braided line, just like..everything. Saves on shipping and it's a good place to shop for ideas. My local one has everything needed to make rail buttons and I plan on taking my new buttons down there at some point and stocking up, because they are super cheap.

 

[GlueckAuf]

Epoxy, uncured, on your hands is a negative also as it is toxic. You should not be making any physical contact with it.

Epoxy is an allergin. You do not want to become allergic to it! Exposure to uncured epoxy triggers the allergy. The more exposure, the more likely you are to get the allergy. Some epoxy systems are also much more likely to give you the allergy quickly, than others. But in general, eliminate physical contact with uncured epoxy. Treat it like a poison. It IS poisonous, but it is also an allergin.

If that caution applies to J-B Weld, it's sure odd in the age of the liability lottery that J-B Weld's new TV commercials show a user spreading the stuff on with his thumb!



Good skies,

GlueckAuf

 

[Off Grid Gecko]

Allergies are tricky things. Saw a sheep go into shock the other day and die within minutes. The farmer I was working with said that she had epinepherine but has never had to use it in 30 years of giving that treatment to her flock and thus stopped bringing it out to the corral. That said, we will have the epi pen from now on when we go out to give them their wormer.
In all cases, allergies are an overresponse from the immune system. It's not as simple as "the more you are exposed, the more likely the reaction." It varies from person to person and allergen to allergen. People say that poison ivy gets worse the more you are around it. I'm around it almost daily because of my lifestyle and location, and actually it doesn't bother me near as much anymore as it did when I first arrived here, though I still get rashes from nasty exposures, like when the ground is wet.
I also eat a lot of herbs and garlic (clove a day or more at the moment), I eat unwashed berries and eggs, and other things like that. The more I do, the less sick I seem to get. Can't recall the last time I had a cold, though I did get tick fever a couple years ago. Now I have the antibodies to fight off that little monster of a disease. (Nearly killed me)

 

[dhbarr]

If that caution applies to J-B Weld, it's sure odd in the age of the liability lottery that J-B Weld's new TV commercials show a user spreading the stuff on with his thumb!

View attachment 423909

Middle frame looks like one of their wood repair putties.

 

[Handeman]

I also eat a lot of herbs and garlic (clove a day or more at the moment), I eat unwashed berries and eggs, and other things like that. The more I do, the less sick I seem to get. Can't recall the last time I had a cold...

I'm a huge believer that your immune system is like a muscle. The more it works the stronger it gets. My wife is a school nurse and is exposed to everything the kids pass around every year. Neither one of us have had more than the sniffles a time or two for years.

I think the whole hand sanitizers all the time and hand washing, and germophobiac attitude is doing more harm than good, especially for kids, because it lets the immune system atrophy.

Then came COVID... New game, new rules.

 

[Off Grid Gecko]

I'm a huge believer that your immune system is like a muscle. The more it works the stronger it gets. My wife is a school nurse and is exposed to everything the kids pass around every year. Neither one of us have had more than the sniffles a time or two for years.

I think the whole hand sanitizers all the time and hand washing, and germophobiac attitude is doing more harm than good, especially for kids, because it lets the immune system atrophy.

Then came COVID... New game, new rules.

Same game technically, it's an H#N# virus like the rest of them (comparable to spanish flu, bird flu, swine flu, etc. with the same mortality rate), has some hard-hitting symptoms (like some of the rest of them), but it's unchecked because it's new and started to spread really rapidly before anyone could make a flu shot for it.
Totally agree on the rest. I avidly avoid hand sanitizer because it kills gut flora, which I try to cultivate where I am at this point in life. I'm a few miles out from the nearest black-top road and spend nearly all of my time outside. The little bugs (bacteria and such) that inhabit the wild foods I eat have done nothing but make me feel tons healthier. I even stopped needing to get up in the night (something the older crowd will understand). Kind of sold myself on it after that. My stomach will kill practically anything that threatens me these days.

 

[Handeman]

Same game technically, it's an H#N# virus like the rest of them (comparable to spanish flu, bird flu, swine flu, etc. with the same mortality rate), has some hard-hitting symptoms (like some of the rest of them), but it's unchecked because it's new and started to spread really rapidly before anyone could make a flu shot for it.
Totally agree on the rest. I avidly avoid hand sanitizer because it kills gut flora, which I try to cultivate where I am at this point in life. I'm a few miles out from the nearest black-top road and spend nearly all of my time outside. The little bugs (bacteria and such) that inhabit the wild foods I eat have done nothing but make me feel tons healthier. I even stopped needing to get up in the night (something the older crowd will understand). Kind of sold myself on it after that. My stomach will kill practically anything that threatens me these days.

Actually it's not the same game. The flu virus kill about 30,000 a year in the US. Corona-virus has killed over 135,000 in about 4-5 months, and that's with closing schools, shutting down everything and social distancing. It would probably be 10 times worse than that if we let it go like we do the flu every year.



I know from early fatality rates in Europe last March I predicted about 8 million deaths in the US. I'm glad I under estimated, at least I hope I have. We'll see if they open schools this fall. I may not be too far off.

 

[Off Grid Gecko]

Actually it's not the same game. The flu virus kill about 30,000 a year in the US. Corona-virus has killed over 135,000 in about 4-5 months, and that's with closing schools, shutting down everything and social distancing. It would probably be 10 times worse than that if we let it go like we do the flu every year.

View attachment 424525

I know from early fatality rates in Europe last March I predicted about 8 million deaths in the US. I'm glad I under estimated, at least I hope I have. We'll see if they open schools this fall. I may not be too far off.

I think we're talking a little apples and oranges, I was referring to lethality on a case by case basis. Something like 1 in 3 contracted cases of bird flu resulted in fatality. There were nearly 20,000 deaths from swine flu from what I can gather with a quick Google search, and Spanish Influenza killed 50 million worldwide with over 375,000 in the US according to the CDC. According to Google, the current US total is around 138,000 out of over 3,000,000 infected. About a 3% kill rate vs number infected, which could have been much, much worse. A 30% kill rate like bird flu, had it spread as fast would have us at over a million dead just in the US.
Don't get me wrong, I'm not trying to downplay the virus, that's a lot of deaths. I was simply referring to the lethality of a single infection, not the grand total. COVID is severe (much like Spanish Flu) in that it infected so many so fast. Let's just hope we don't top that virus's numbers by staying safe. It's definitely something to be mindful about.

We actually had a really bad virus sweep through the county I'm in that killed several people (my town teeters over 100 population) after the first cases but before everyone started testing and social distancing. Lots of tourists pass through, and some out here suspect that we may have actually got the infection early, because to my knowledge there isn't a single reported case here despite all the visitors from out of town and out of state. Even right next door in the next town there are cases, but not in our little spot. It's eerie.

 

[gldknght]

isn't JB weld much heavier then BSI epoxy per the same volume? I am just guessing but it seems heavier

Yes, because of the powdered metal additive.
Jb Weld is extreme overkill in any use for rocketry except attachment of metal parts, i.e. the metal motor retainers. Why in the world would you want to add weight to the bottom of your rocket? Normal epoxy is plenty strong for most applications.

 

[Off Grid Gecko]

Yes, because of the powdered metal additive.
Jb Weld is extreme overkill in any use for rocketry except attachment of metal parts, i.e. the metal motor retainers. Why in the world would you want to add weight to the bottom of your rocket? Normal epoxy is plenty strong for most applications.

Yes but it smooths in there so nicely, lol.
My fillets are pretty small. If I was doing a 1/2" radius then yes, it would be way too much, but that's probably way too much with anything.
Can't speak for the others, it simply worked well for me. Going to recheck the way I used to do things. Is normal Bondo (2-part pink stuff) heavier than epoxy? An outer fillet doesn't need to be incredible strength, especially TTW where it's secured on the inside with epoxy and there's more under the fillet where it attaches to the body, yet many people seem to hate Bondo with a passion when it comes to rockets. Works just fine on race cars.

 

[gldknght]

Yes but it smooths in there so nicely, lol.
My fillets are pretty small. If I was doing a 1/2" radius then yes, it would be way too much, but that's probably way too much with anything.
Can't speak for the others, it simply worked well for me. Going to recheck the way I used to do things. Is normal Bondo (2-part pink stuff) heavier than epoxy? An outer fillet doesn't need to be incredible strength, especially TTW where it's secured on the inside with epoxy and there's more under the fillet where it attaches to the body, yet many people seem to hate Bondo with a passion when it comes to rockets. Works just fine on race cars.

Just because it's easy to use, does not mean it's a good idea. Why add any extra weight to the tail when you do not need it? I think the same about bondo, as in "not needed for fillets". Why complicate things? Epoxy fillets are just as easy.

 

[rocketman4h]

I don't think Bondo wasn't made to go past mach 1. we use it at work to make fixtures for small parts... it seams to chip easy... never saw epoxy of any kind chip... bubbles in the layup may cause a crack to form but not chip. #thinkabouttheCD

 

[afadeev]

I avidly avoid hand sanitizer because it kills gut flora, which I try to cultivate where I am at this point in life. [...]My stomach will kill practically anything that threatens me these days.

This got me intrigued - what flora, exactly, are you cultivating on your hands (the area that would normally be exposed to hand sanitizer) ?
Or did you entertain the thought of ingesting hand sanitizer, per certain federal politician's recommendation?
How exactly does hand sanitizer effect your gut flora?

Is normal Bondo (2-part pink stuff) heavier than epoxy?

Bondo is lighter than epoxy w/o fillers.
It is also fairly brittle.

An outer fillet doesn't need to be incredible strength, especially TTW where it's secured on the inside with epoxy and there's more under the fillet where it attaches to the body, yet many people seem to hate Bondo with a passion when it comes to rockets. Works just fine on race cars.

Many use bondo in rocketry, just not for structural reinforcement. Bondo works great as a spiral filler for paper tubes.

Cars don't routinely bounce off the ground at 20+m/s during landings, or bounce in the trunks during transportation.
So the comparison is a bit of a stretch.

 

[Off Grid Gecko]

This got me intrigued - what flora, exactly, are you cultivating on your hands (the area that would normally be exposed to hand sanitizer) ?
Or did you entertain the thought of ingesting hand sanitizer, per certain federal politician's recommendation?
How exactly does hand sanitizer effect your gut flora?



Bondo is lighter than epoxy w/o fillers.
It is also fairly brittle.



Many use bondo in rocketry, just not for structural reinforcement. Bondo works great as a spiral filler for paper tubes.

Cars don't routinely bounce off the ground at 20+m/s during landings, or bounce in the trunks during transportation.
So the comparison is a bit of a stretch.

Sanitizer goes on hands, hands go on food, food goes down the tube with trace amounts of an ingredient that acts as a broad-spectrum poison against bacteria, even the ones that live in your gut and help you digest food. Alcohol-based sanitizer contained denaturing agents which are directly poisonous to human beings and just about everything else (It ain't Everclear) Alcohol, depending on concentration also selectively chooses its victims in the microscopic world. Acetobacter loves getting wasted, but a high enough concentration will kill it.
There are volumes of data freely available on the immune system online, and I've already done enough derailing to this thread. If you are truly interested, there are scatterings of journal articles, clinical reports, theories, and of course the usual internet BS available on the subject, all with different opinions on the specifics.
Suffice to say, when I see someone slathering their hands with sanitizer prior to diving into a McSandwich, that makes me more nervous than the germs they are trying to kill. I like talking about this stuff, but this isn't really the place. I think I sufficiently answered your query on my reasoning, and the above is just that, my opinion based on my own research and understanding and direct experience.

On with the show.

I've used Bondo and I kinda like it for ease of use and light weight. There are several products that contain additions or different formulations that I think would be just fine in rocketry, but I don't have much direct experience with them. Would kinda like to try kitty hair and see how it holds up.

In any case, I use bondo for finishing and filling, not as a structural element. And with TTW fins I'd hardly consider fillets a structural element. The attachy parts are down below.

 

[John Kemker]

Someone please correct me if I'm wrong, but isn't Bondo basically a polyester resin? Catalyzes with MEK, if I remember correctly. That would explain it's "chipping" and brittleness, would it not?

 

[Off Grid Gecko]

Someone please correct me if I'm wrong, but isn't Bondo basically a polyester resin? Catalyzes with MEK, if I remember correctly. That would explain it's "chipping" and brittleness, would it not?

This is my understanding that it is a polyester resin. I don't know much else about it except from using it.