Fiberglass or carbon fiber? Nah. I'm thinking pants.

Discussion in 'Techniques' started by ebruce1361, Mar 5, 2020.

Help Support The Rocketry Forum by donating:

  1. Mar 17, 2020 #91

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    That makes sense with the JB Weld piece, but I measured out the Harbor Freight Epoxy by weight and that piece was made over a week ago, so my guess is either it needs some thermal curing (not sure about this), I didn't mix it well (quite possible), or the epoxy isn't very high quality (almost a certainty).

    I have a number of leads on better epoxy, and I might just go to Goodwill to pick up a toaster oven to play with heat curing.
     
  2. Mar 17, 2020 #92

    ThreeJsDad

    ThreeJsDad

    ThreeJsDad

    Well-Known Member

    Joined:
    Nov 26, 2009
    Messages:
    607
    Likes Received:
    204
    Gender:
    Male
    Location:
    Greensboro, NC
    Try to find an EZ bake oven, I used a giant version of an EZ bake for years. Since it was in the garage I used 80w bulbs in the winter time and 60w bulbs in the summer months. You may not be able to set a toaster over low enough. I would stay under 180deg. I cure in my kitchen oven at 150deg all the time with smaller parts like MMT's.

    You could put a light bulb in a foam cooler and you have a simple little curing oven.
     
  3. Mar 17, 2020 #93

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    I was actually thinking about using an EZ bake oven, but I thought it might not be hot enough. But if I need to hit around 150⁰F, then a foam cooler, some aluminum foil, and a lightbulb will work just fine!

    Suppose I were to make a set of three 3"² fins to be cured in such an oven. How long should I cure them for, and would I need to suspend them somehow or just lay them down on the bottom?
     
  4. Mar 18, 2020 #94

    manixFan

    manixFan

    manixFan

    Not a rocket scientist

    Joined:
    Feb 15, 2009
    Messages:
    1,507
    Likes Received:
    529
    Gender:
    Male
    Location:
    TX
    I’ve sanded a lot of fins with composite layups. I’ve never had a problem with epoxy gumming up or chasing my tail. I’ve used orbital sanders on composite fins with no issues. However I do wet sand as much as possible, mostly because it’s easier to control the dust. Maybe it gums up if it’s not mixed right or it’s a different kind of epoxy. I’ve also sanded a lot of JB Weld and the biggest issue there is it’s so hard it does not sand well at all.

    Let us know how it turns out,


    Tony
     
    ebruce1361 likes this.
  5. Mar 18, 2020 #95

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    While the JB Weld was permitted to cure for four days before sanding, it is possible that it needs even more time to fully cure. On top of that, I didn't actually measure the portions by weight, so it's quite possible that my ratio isn't perfect. One thing I did notice about both pieces is that the denim fabric itself seemed to be the thing that was disintegrating on the sander. With the rough shaping I already have, I might try smoothing the edge with a finer grit paper by hand. It might just be that my belt sander is too coarse with its current belt.
     
  6. Mar 18, 2020 #96

    ThreeJsDad

    ThreeJsDad

    ThreeJsDad

    Well-Known Member

    Joined:
    Nov 26, 2009
    Messages:
    607
    Likes Received:
    204
    Gender:
    Male
    Location:
    Greensboro, NC
    If you can get your cure temp to 150deg 24hrs should be fine. You want even heat so if you can prop them against each other or stand them up on edge in some way that would be fine. My tubes lay flat but I have a fan moving the air around inside the oven.
     
    ebruce1361 likes this.
  7. Mar 18, 2020 #97

    ThreeJsDad

    ThreeJsDad

    ThreeJsDad

    Well-Known Member

    Joined:
    Nov 26, 2009
    Messages:
    607
    Likes Received:
    204
    Gender:
    Male
    Location:
    Greensboro, NC
    I have lost track of how many fuselages and wings I have sanded and with no issues just as you point out. I was simply saying that if that starts to happen due to a poor cure or maybe the wrong type of resin it wont just stop. It may go away if the item is left alone to finish curing, however if the mix was off it may never go away.
     
  8. Mar 18, 2020 #98

    ThreeJsDad

    ThreeJsDad

    ThreeJsDad

    Well-Known Member

    Joined:
    Nov 26, 2009
    Messages:
    607
    Likes Received:
    204
    Gender:
    Male
    Location:
    Greensboro, NC
    I was wondering if the denim was the real issue. If the fabric was not fully saturated you get this effect. The denim will not sand as cleanly if the epoxy/resin did not full saturate it. The viscosity of the epoxy is one of the things I look for in a lay-up resin. The one I recommended to you is about like milk once mixed. It wets out very easily which is a big help since all of this is basically on the clock.
     
    ebruce1361 likes this.
  9. Mar 18, 2020 #99

    Greg Furtman

    Greg Furtman

    Greg Furtman

    Forum Supporter TRF Supporter

    Joined:
    Nov 10, 2018
    Messages:
    681
    Likes Received:
    273
    Gender:
    Male
    Location:
    Webster, Wisconsin
    In the video the denim did not look fully saturated to me.
     
    ebruce1361 likes this.
  10. Mar 18, 2020 #100

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    @ThreeJsDad
    I'll do some follow-up tests with trying to get better saturation of the denim. I honestly didn't expect fantastic results from the JB Weld, but I still have yet to try thinning it with acetone. As for the clear epoxy, I'll try thinning that as well, but I also wonder if evacuating the air would help. I have most of the parts I need for a home-made vacuum chamber, I just haven't built it as yet. I know epoxies are frequently evacuated to to get the air out from the mixing process, and I can imagine there are tiny pockets of air between the denim fibers. If I were to thin the epoxy with acetone and thoroughly soak the denim and then vacuum the air out, I'll bet that would give me better saturation and therefore a stronger matrix.
     
  11. Mar 18, 2020 #101

    Greg Furtman

    Greg Furtman

    Greg Furtman

    Forum Supporter TRF Supporter

    Joined:
    Nov 10, 2018
    Messages:
    681
    Likes Received:
    273
    Gender:
    Male
    Location:
    Webster, Wisconsin
  12. Mar 18, 2020 #102

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    $20 for six ounces isn't bad at all! That's two ounces less than the "big" bottles of Loctite epoxy, but not that much more expensive. For doing a few fins, that would hold out just fine, but not so much for bigger parts. Luckily, the seller has the same stuff in 12, 24, 48, and 96 ounce sets as well.
     
  13. Mar 18, 2020 #103

    Greg Furtman

    Greg Furtman

    Greg Furtman

    Forum Supporter TRF Supporter

    Joined:
    Nov 10, 2018
    Messages:
    681
    Likes Received:
    273
    Gender:
    Male
    Location:
    Webster, Wisconsin
    @ebruce1361 My upcoming carbon fiber project is to build a truss tube Dobsonian mount for an 18" mirror I'm making for myself. The Pyrex mirror weighs 28# so I want to keep the weight of the mount as light as I can for transporting it.Here's a link to a scope a fellow in Germany made.

    http://www.stathis-firstlight.de/atm/ernst_carbon.htm
     
    ebruce1361 likes this.
  14. Mar 18, 2020 #104

    ThreeJsDad

    ThreeJsDad

    ThreeJsDad

    Well-Known Member

    Joined:
    Nov 26, 2009
    Messages:
    607
    Likes Received:
    204
    Gender:
    Male
    Location:
    Greensboro, NC
    I get concerned when ordering from a shop that is repackaging and wont share information like mixed viscosity. This is what I have used for the last 15 years, I use the 2050 with the slow hardener. I have never gotten a bad batch and they have always had the tech support I needed. My only issue if this can really be an issue is the hardener will form some nasty crusty stuff on the outside of my small bottles I use for dispensing it. I pour from the large bottle to small bottles for easy dispensing because I use a scale. It is so thin I can do a 40" by 2.5" tube with about 70 grams.

    https://www.resinresearch.net/composite-pro-system
     
    ebruce1361 likes this.
  15. Mar 18, 2020 #105

    ThreeJsDad

    ThreeJsDad

    ThreeJsDad

    Well-Known Member

    Joined:
    Nov 26, 2009
    Messages:
    607
    Likes Received:
    204
    Gender:
    Male
    Location:
    Greensboro, NC

    If you wet out your parts really good with a roller and then put them in a vacuum bag between some thin mylars you can omit the who step of vacuuming the epoxy. Vacuuming the epoxy is nice when pouring parts or pouring molds. If you don't have any mylar you can use write and wipe poster board from Hobby Lobby. Put your pieces between the shiny sheets, put plastic drop cloth over this, a layer of paper towels top and bottom and put it in a vacuum bag. The paper towels allows the air to be removed from the entire surface. If you use the food save bags you can omit the paper towel.
     
    ebruce1361 likes this.
  16. Mar 18, 2020 #106

    heada

    heada

    heada

    Well-Known Member

    Joined:
    Jan 18, 2009
    Messages:
    2,815
    Likes Received:
    279
    Gender:
    Male
    Location:
    Indianapolis, Indiana
    Clear packing tape (polyethylene tape) also works well as a release.
     
    ebruce1361 likes this.
  17. Mar 18, 2020 #107

    ThreeJsDad

    ThreeJsDad

    ThreeJsDad

    Well-Known Member

    Joined:
    Nov 26, 2009
    Messages:
    607
    Likes Received:
    204
    Gender:
    Male
    Location:
    Greensboro, NC
    You could do that and apply it to a stiff surface like poster board.
     
    ebruce1361 likes this.
  18. Mar 19, 2020 #108

    Greg Furtman

    Greg Furtman

    Greg Furtman

    Forum Supporter TRF Supporter

    Joined:
    Nov 10, 2018
    Messages:
    681
    Likes Received:
    273
    Gender:
    Male
    Location:
    Webster, Wisconsin
    On the eBay site for the epoxy I suggested it has this.
    Resin Hardener Typical Physical Properties:
    All-purpose system. Use with fiberglass and carbon fiber hand lay-up systems, marine, adhesives, coatings, vacuum bagging, casting, and electronic encapsulation.
    Viscosity cps at 25C 1600
    Mix by Volume 2 to 1
    Tensile Strength 9,800
    Tensile Modulus 405,000
    Flexural Strength 14,800
    Flexural Modulus 480,000
    HDT 122F
    Compression. Yield 15,400
    Elongation % 3.8

    Does that help with the viscosity question?
     
    ebruce1361 likes this.
  19. Mar 20, 2020 #109

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    I'm sure most of you are aware of my build in progress, A Wee Dram.
    https://www.rocketryforum.com/threads/care-for-some-scotch.157850/

    Well, I had a bit of cross-pollination of information and observation between my projects last night that applies to my journey with learning the ways of epoxy. Since this rocket is made with tubes that are wrapped with a paper label, I had to make slots in the label that would allow glue to contact the fin root as well as the actual tube. Additionally, I cut notches in these slots to accommodate four tabs on each fin so that I had more surface area for glue to contact both the fin and tube. (Although this is technically a through-the-wall fin design, the tabs do not extend all the way to the motor mount because this is a four-motor cluster with three fins and I didn't fee like doing THAT much math)

    20200315_212658.jpg
    20200315_212705.jpg

    So, what does all this have to do with my epoxy/denim experiments? Well, I had the opportunity to finally combine epoxy with acetone and get a feel for how well it works. After the initial silicone based glue cured on the fins, I was left with a bunch of little gaps between the body and fin roots due to minor imperfections and inconsistencies in the slots I made (this was expected). So, to fill those gaps and to act as fillets, I wanted to use some epoxy, but I wanted to use only a TINY (about 1/16" wide) amount to keep from messing up the appearance of the body or fins. To do that, I decided to use a syringe with a thin applicator tip to apply the epoxy with pinpoint precision, but the epoxy was too thick to work in the tip. So, I added a splash of acetone (I didn't weigh the parts exactly, but I would guess a rough 1:1:0.5 ratio of the halves of the epoxy plus acetone by weight) and loaded up a second syringe. This time, the mix came out easily with a runny consistency like cheap pancake syrup, and flowed easily into millimeter-wide gaps.

    20200319_230839.jpg

    But here's the real kicker: I used Loctite 5 minute epoxy for this, and that time estimate is pretty accurate. However, adding the acetone almost DOUBLED the working time! After five or so minutes, the epoxy was about the consistency of freshly mixed epoxy and still could be easily spread around. After a good ten minutes or more, it was starting to stiffen up. By the time I had cleaned up my supplies and put the rocket up to cure overnight, it had been close to 45 minutes and the fins still had a bit of a wiggle to them. I was worried that I had made a mix that wouldn't truly harden, but as of this morning, the wiggle was gone.

    SO.

    I was initially hesitant to try the Loctite 5 minute epoxy for the denim composite experiments because I didn't think I would have enough time to saturate each piece before It began to cure, but by thinning it with acetone, it not only becomes more liquidy, but allows for more working time! I still need to get some non-absorbent paper plates (although now i am contemplating metal pie plates since I mixed last night's epoxy for the fins in a metal cap from another scotch tube) in order to prevent the acetone from being absorbed before it can properly mix with the epoxy, but aside from that, these results are very interesting and encouraging! I might even try the same thing with the JB Weld since I first read about the acetone trick from their website. More fun to follow!
     
    Greg Furtman likes this.
  20. Mar 23, 2020 #110

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    Making experiment piece #3! This time with acetone!

     
  21. Mar 26, 2020 at 2:01 PM #111

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    Opening of experiment piece #3!



    So, this turned out a lot different than I expected. It would seem that despite the acetone making the epoxy mixture thinner, it also weakened the mixture, making it flexible. This was unexpected since the acetone additive in the Loctite 5 minute epoxy extended the working time but still set up rigid on my fin fillets. As a wise man once said,
    Geralt_Hmm_Banner.jpg

    As coincidence would have it, this post was made yesterday and included some useful information:
    https://www.rocketryforum.com/threads/most-asked-glue-questions.158497/#post-1979941

    Specifically, acetone is mentioned as an additive that does indeed thin epoxies, "but is more likely to change the cured properties of the epoxy". Luckily, I have some denatured alcohol as well, and that seems to be a superior recommendation. I guess the bad press I heard on using alcohol referred to rubbing alcohol since that can have up to 40% water in it. So, I'll be pressing on with an experiment using the denatured alcohol as a thinning additive. I will continue to use the same cheap Harbor Freight epoxy so as to keep the additive the only variable, but I may do a comparison with JB Weld also using the acetone and denatured alcohol. Remember, I first read about using acetone from the JB Weld website in the first place, so maybe acetone works better with that kind of epoxy and not so much with clear epoxies. Having said that, I have no idea why the fillets on my fins did okay with acetone added. I don't imagine there is much of a formula difference between Loctite and the knockoff Harbor Freight stuff. Maybe I should try to scrounge up MSDS sheets for both and compare them.

    In the endeavor of science, there's no such thing as bad results! Just unexpected results that give good data on how NOT to do it.
     
  22. Mar 27, 2020 at 2:04 PM #112

    John Kemker

    John Kemker

    John Kemker

    Forum Supporter TRF Supporter

    Joined:
    Aug 25, 2019
    Messages:
    613
    Likes Received:
    232
    Gender:
    Male
    Just out of curiosity, have you tried using an epoxy designed for lamination, like West Systems or Aeropoxy? You might not need to thin in order to get the viscosity you want.
     
    ebruce1361 likes this.
  23. Mar 27, 2020 at 2:37 PM #113

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    Thus far, I have not. The only epoxies I have used in these experiments thus far are Harbor Freight Quick Drying (they claim 5 minutes, but it behaves more like a 15 minute) and regular JB Weld. What I'm going for in these experiments is seeing what the limits and possibilities of cheaper, more readily available materials are. Like, can a rocket be built in the style of fiberglass or carbon fiber construction, but from pants and adhesives bought at Walmart for less than $100? Weird experiment, I know, but I like weird challenges. As for the Aeropoxy, I might just get some for other, more traditional builds, but also to make a comparison piece with the denim to serve as an "ideal" piece.
     
  24. Mar 27, 2020 at 3:04 PM #114

    boatgeek

    boatgeek

    boatgeek

    Well-Known Member

    Joined:
    Dec 27, 2014
    Messages:
    2,194
    Likes Received:
    646
    You might check unit prices as well. You can pick up a quart of laminating epoxy resin plus hardener from either West Systems or System 3 (my personal favorite) for $75-80 on Amazon. That will get you through at least a couple of rockets. With jeans from the thrift store, you could totally hit $100 per rocket. It's a little more up front, but probably worth it in the long run, especially if you want to do other fiberglassing work.
     
    ebruce1361 likes this.
  25. Mar 27, 2020 at 4:01 PM #115

    ebruce1361

    ebruce1361

    ebruce1361

    The man with the plan. And some duct tape.

    Joined:
    May 14, 2018
    Messages:
    333
    Likes Received:
    136
    Location:
    Pinellas County, Florida
    @boatgeek That's not a bad idea. I do plan on playing with fiberglass kits here eventually (I was literally just looking at the BT60 kits from Mach One)
     

Share This Page

Group Builder