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Is JB Weld an acceptable construction epoxy for FG to FG joints? I have G5000 for fillets, but I am trying to decide what the best epoxy is for the assembly.
Thanks!
Thanks!
JB weld for FG assembly?
- Thread starter bclark989
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If you don't mind paying the exorbitant price, then it's fine. JB Weld is $5.67 per ounce, whereas RocketPoxy is $1.09 per ounce (before shipping). Why not just use the RocketPoxy? I only use JB Weld for the retainer.
Make sure you wash the surfaces with soap and water, rinse thoroughly, rough up the surface with 60-grit sandpaper, then use acetone or isopropyl alcohol to clean away the dust.
Make sure you wash the surfaces with soap and water, rinse thoroughly, rough up the surface with 60-grit sandpaper, then use acetone or isopropyl alcohol to clean away the dust.
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Keisling, thanks. That's what i was thinking.
Bat-mite, I suppose the main reason would be that I'm going to use so little of it. One package of JB Weld will probably build the whole rocket. I'll need an ounce or two to do fillets, but I'll be doing those with the G5000. To me its not worth the hassle to go through an online vendor, pay for shipping, etc, just to save $5.
Bat-mite, I suppose the main reason would be that I'm going to use so little of it. One package of JB Weld will probably build the whole rocket. I'll need an ounce or two to do fillets, but I'll be doing those with the G5000. To me its not worth the hassle to go through an online vendor, pay for shipping, etc, just to save $5.
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FWIW, JB Weld is a good grade of epoxy with calcium carbonate and powdered iron (or steel; I forget which) added.
Gerald
Gerald
G5000 is RocketPoxy. You already have some, apparently. I'm confused....
You can always buy some hobby epoxy in the small bottles. 4.5 or 9 oz. Pretty reasonable price. Probaby get several builds out of the bottled. I use JB Weld mainly on the motor retainer.
cavecentral
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You can find larger tubes of jb weld on ebay. Cheaper per ounce than the little ones.
isn't JB weld much heavier then BSI epoxy per the same volume? I am just guessing but it seems heavier
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I buy JB 10oz tubes on Ebay for around $1.30/oz including shipping. I use JB for fillets and motor mounts on all of my larger rockets (N motor being the largest). It works well and if I need it to flow a little better I use a heat gun for about 10 seconds. I use Aeropoxy light for fillets on smaller rockets. It's very easy to sand and slightly thicker consistency than JB but not as strong.
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Actually JBWeld isn't really that strong. IIRC, it is about 40% the strength of the strongest stuff. But it is reasonably resistant to cracking and seems to adhere fairly well. Those are two common failure modes for bulk epoxy. It also has reasonable tolerance for a bit of mild heating. So being weaker is not usually a big deal.
Gerald
Gerald
Spit. Spit on your finger as you pull the fillet.
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Water in epoxy is a negative. 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.
You can research epoxy strength if you want. You don't need me to do it for you! But, since you didn't research it, here is one quick link: https://www.rocketryforum.com/threads/epoxy-comparisons-and-technical-data-sheets.138953/
An epoxy system I often recommend considering: https://www.cstsales.com/mgs_epoxy.html This has some of the best properties for a room temp cure epoxy system, and properties are improved by appropriate post-cure heat treatment cycle. But it is not a high temp system, such as those produced by Cotronics, or such as JBWeld. MGS is used for commercial plane manufacturing. Another similar product is System 2000.
Note MGS, and System 2000, are unfilled epoxy systems. If you want it thicker (as in, more like JBWeld), you add your own fillers. That can include such materials as calcium carbonate and iron powder such as with JB Weld (IIRC), various fiber additives to make it an FRP, metallic additives, ceramic microfiber additives, and various other solids. You can tailor the properties a fair bit that way. But what you can't do is magically improve the Tg (glass transition temperature). If your temperature hits Tg, then your rigid epoxy turns into something more like a stiff taffy or a pitch. It will permanently deform under pressure. That is not usually a good thing...
JBWeld is good if you need so-so mechanical properties, along with fairly good operational temperature tolerance, ready availability, low flow, and acceptible price.
Gerald
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.
You can research epoxy strength if you want. You don't need me to do it for you! But, since you didn't research it, here is one quick link: https://www.rocketryforum.com/threads/epoxy-comparisons-and-technical-data-sheets.138953/
An epoxy system I often recommend considering: https://www.cstsales.com/mgs_epoxy.html This has some of the best properties for a room temp cure epoxy system, and properties are improved by appropriate post-cure heat treatment cycle. But it is not a high temp system, such as those produced by Cotronics, or such as JBWeld. MGS is used for commercial plane manufacturing. Another similar product is System 2000.
Note MGS, and System 2000, are unfilled epoxy systems. If you want it thicker (as in, more like JBWeld), you add your own fillers. That can include such materials as calcium carbonate and iron powder such as with JB Weld (IIRC), various fiber additives to make it an FRP, metallic additives, ceramic microfiber additives, and various other solids. You can tailor the properties a fair bit that way. But what you can't do is magically improve the Tg (glass transition temperature). If your temperature hits Tg, then your rigid epoxy turns into something more like a stiff taffy or a pitch. It will permanently deform under pressure. That is not usually a good thing...
JBWeld is good if you need so-so mechanical properties, along with fairly good operational temperature tolerance, ready availability, low flow, and acceptible price.
Gerald
Use disposable latex gloves. It makes smoothing out fillets easy.
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
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
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
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Use nitrile -- a person can become allergic to latex through repeat exposure -- no more Band-Aids.
Been doing it that way for 50 years. You also are suppose to use a non toxic willow tree for roasting marsh mellows in the state of CA.
o1d_dude
'I battle gravity'
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.
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.
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OMG! Obviously you don't know the dangers of salicylic acid which lurks in the willow tree.
Now that is a great idea! Thanks.
The real question then becomes...Can you turn out a decent looking Rose petal?
If that acid is good enough for the North American Spotted Ferret Bat, then it's good enough for me!
Off Grid Gecko
Well-Known Member
Toxicity is a matter of dosage. The same plant can be a medicine or a poison, depending on dosage. ~Paracelsus
Just chiming in that JBWeld is quickly becoming my favorite epoxy for doing fillets. It wipes on pretty smooth and washes off my fingers with dish soap really easily.
I personally don't wear gloves when using epoxy, but I never encourage anyone else to do what I do. I have a different view of reality than most and deal with toxic and allergenic substances on a daily basis. I eat ragweed and can't set foot in my pole barn without becoming exposed to poison ivy.
Just chiming in that JBWeld is quickly becoming my favorite epoxy for doing fillets. It wipes on pretty smooth and washes off my fingers with dish soap really easily.
I personally don't wear gloves when using epoxy, but I never encourage anyone else to do what I do. I have a different view of reality than most and deal with toxic and allergenic substances on a daily basis. I eat ragweed and can't set foot in my pole barn without becoming exposed to poison ivy.
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.
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Plus 1 on the fondant tools. Same trick as the sharpie on pvc, scribble a bunch of sharpie on the fondant ball and mark the fin/bt intersection, mask and fill. I use RocketPoxy but any decent epoxy should work well for fillets. Alcohol for epoxy, water for TNQ if you need it. Nicer fillets than I used to make.
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FYI that is what I laminated the leading edges of my Nike Apache composite fins with. Fiberglass cloth with JB Weld as the matrix in the composite.
Here is a pic of the edges before final paint and flight.
Flight speed was M2.14.
Here is a pic of the edges before final paint and flight.
Flight speed was M2.14.
@OverTheTop Are you familiar with the location & history of the Keweenaw Range? The Keweenaw Peninsula is a finger sticking out into Lake Superior. My Great Grandparents on my Mom's side of the family were Finnish immigrants who settled there. Since it is surrounded by water on 3 sides it gets a huge amount of Lake Effect Snow. The average snowfall is 220 inches each year! It's a beautiful area.
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