News:


  • March 28, 2024, 06:09:03 AM

Login with username, password and session length

Author Topic: Fast vs slow drying epoxy  (Read 1363 times)

Offline kevin king

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1525
Fast vs slow drying epoxy
« on: January 24, 2022, 11:19:17 AM »
I notice the plans call out for slow drying epoxy on the nose of our planes, but i used 5 min epoxy. Is there any real difference, aside from dry time? just wondering.
Thanks

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Fast vs slow drying epoxy
« Reply #1 on: January 24, 2022, 11:50:55 AM »
I notice the plans call out for slow drying epoxy on the nose of our planes, but i used 5 min epoxy. Is there any real difference, aside from dry time? just wondering.
Thanks

It doesn't get much chance to penetrate the wood, and it gets brittle over time.  If you've already built the plane it's probably not worth the effort of tearing it apart and doing it over, though.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6823
Re: Fast vs slow drying epoxy
« Reply #2 on: January 24, 2022, 01:28:11 PM »
    I don't use anything faster than 30 minute, as it is often enough too fast! Like Tim mentioned, you need some time for the glue to penetrate. 5 minute epoxy working time is less than that because it starts the second that the two parts come in contact with each other. you can spend up to two minutes mixing thoroughly and then you are down to three! . Fifteen minute epoxy is almost as bad, and I generally just keep that around for repairs.  So I for the most part stick with 30 minute and one hour stuff.
  Type at you later,
   Dan McEntee
« Last Edit: January 25, 2022, 01:45:57 PM by Dan McEntee »
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Craig Beswick

  • 24 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 562
Re: Fast vs slow drying epoxy
« Reply #3 on: January 24, 2022, 02:13:07 PM »
There are YouTube videos comparing brands and drying times.

The most dramatic observation was the longer the drying time the better the glue joint. 30 minute was around 10 times stronger than 5 minute. From memory Original JB Weld beat them all.

Craig
AUS 87123
"The Ninja"

Offline Istvan Travnik

  • 24 supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 288
Re: Fast vs slow drying epoxy
« Reply #4 on: January 24, 2022, 02:19:13 PM »
We can afford a general rule on usual, clear epoxy glues: faster is weaker, slower is stronger.
In the most critical applications (e. g. engine mount, three bladed wooden props, etc. I use exclusively 24 hrs epoxy, heated a for some minutes with hairdryer for better penetration).

Offline kevin king

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1525
Re: Fast vs slow drying epoxy
« Reply #5 on: January 24, 2022, 03:27:17 PM »
Thanks for educating me guys. 👍

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 13716
Re: Fast vs slow drying epoxy
« Reply #6 on: January 25, 2022, 11:14:43 AM »
Sounds as if you got an answer, but, more or less like all "glue threads", while the information is probably correct, it doesn't make that much difference. People used to build entire airplanes with Duco Cement or Ambroid, many of which are still together and showed no real problems in use. 5-minute epoxy is tremendous overkill for gluing wood to wood, as long as it is mixed correctly and applied before it starts to set.  The fact that something else might be better is rather beside the point.

    There are a few cases where the glue characteristics matter, like sheeting foam wings, where you need a lot of working time. But it is almost never about how strong it is. Good technique is really important almost all the time, but the materials are generally far more than adequate.

    Brett

Offline Ken Culbertson

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6034
Re: Fast vs slow drying epoxy
« Reply #7 on: January 25, 2022, 11:47:34 AM »
Since going electric, I hardly use Epoxy anymore.  Titebond or White Gorilla is more than strong enough and it tastes much better when chewing it off your fingers.

Ken
AMA 15382
If it is not broke you are not trying hard enough.
USAF 1968-1974 TAC

Offline BillP

  • 21 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 513
Re: Fast vs slow drying epoxy
« Reply #8 on: January 25, 2022, 12:51:12 PM »
Sounds as if you got an answer, but, more or less like all "glue threads", while the information is probably correct, it doesn't make that much difference. People used to build entire airplanes with Duco Cement or Ambroid, many of which are still together and showed no real problems in use. 5-minute epoxy is tremendous overkill for gluing wood to wood, as long as it is mixed correctly and applied before it starts to set.  The fact that something else might be better is rather beside the point.

    There are a few cases where the glue characteristics matter, like sheeting foam wings, where you need a lot of working time. But it is almost never about how strong it is. Good technique is really important almost all the time, but the materials are generally far more than adequate.

    Brett

+1

Bill P.

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Fast vs slow drying epoxy
« Reply #9 on: January 25, 2022, 01:22:39 PM »
...  There are a few cases where the glue characteristics matter, like sheeting foam wings,...

I think I'd add gluing up anything with gaps, like repairs or gluing wings into profile fuselages (where I never seem to get the gap right -- if the incidence is right and the worst gap is 1/8" or less, I've learned to be happy) or gluing formers into a hand-carved depression.  For that sort of joint you want a glue that can fill a gap, be strong enough, and not be too heavy.  I tend to use Gorilla foaming glue or epoxy+microballoons in that case, depending on the strength needed from the joint.

And I like using Gorilla foaming glue to glue styrofoam stuff together, because it's about as strong as styrofoam.  I haven't done any studies on it, but foamed-up Gorilla glue isn't much less flexible than styrofoam, and I suspect it'll lead to fewer stress risers (and less weight) than epoxy.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Paul Smith

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 5793
Re: Fast vs slow drying epoxy
« Reply #10 on: January 26, 2022, 09:08:54 AM »
For filling gaps, 30-minute epoxy mixed with micro balloons from the boat store is great.   An empty quart container and full quart of micro balloons weighs the same.

I use a four-step process with the model positioned work with gravity of each of the four gaps.  A little batch epoxy mixed with micro balloons and warmed with the heat gun fills every void.

If you have serious gap you may need some masking tape on the back side.


Paul Smith

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Fast vs slow drying epoxy
« Reply #11 on: January 26, 2022, 11:20:07 AM »
... I use a four-step process with the model positioned work with gravity of each of the four gaps.  A little batch epoxy mixed with micro balloons and warmed with the heat gun fills every void....

Interesting -- I just push enough microballoons into it so that it stays where it's put ("thixotropic" if you want to be technical).  It sticks to balsa well enough to rip out the base material before it fails (so, plenty strong enough), and it's easier to sand than if you leave it a bit runny.

I haven't had wing & fuselage part ways yet.

Or I just use the pre-mixed blue stuff from Brodak's -- and again, wing & fuselage stay married.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6823
Re: Fast vs slow drying epoxy
« Reply #12 on: January 26, 2022, 11:30:19 AM »
Sounds as if you got an answer, but, more or less like all "glue threads", while the information is probably correct, it doesn't make that much difference. People used to build entire airplanes with Duco Cement or Ambroid, many of which are still together and showed no real problems in use. 5-minute epoxy is tremendous overkill for gluing wood to wood, as long as it is mixed correctly and applied before it starts to set.  The fact that something else might be better is rather beside the point.

    There are a few cases where the glue characteristics matter, like sheeting foam wings, where you need a lot of working time. But it is almost never about how strong it is. Good technique is really important almost all the time, but the materials are generally far more than adequate.

    Brett

     Working times is what I was trying to stress. The principle thing to to watch on any glue joint is parts fit up. If there are gaps and such it affects any glue joint. If the epoxy starts to kick and doesn't let the parts settle into their preferred position, that could be a problem. 5 minute is just too fast. nothing like getting things ready for making a joint, then remembering something you forgot or can't find, and the clock is ticking and the glue is getting thicker and thicker! Fifteen minute glue is actually still too fast for my tastes in this respect and by the time 10 minutes has ticked off from the time you started to mix, it's too thick to really use. I usually don't worry at all about strength, I worry about getting things in position properly.
   Type at you later,
    Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Fast vs slow drying epoxy
« Reply #13 on: January 26, 2022, 11:35:44 AM »
     Working times is what I was trying to stress. The principle thing to to watch on any glue joint is parts fit up. If there are gaps and such it affects any glue joint. If the epoxy starts to kick and doesn't let the parts settle into their preferred position, that could be a problem. 5 minute is just too fast. nothing like getting things ready for making a joint, then remembering something you forgot or can't find, and the clock is ticking and the glue is getting thicker and thicker! Fifteen minute glue is actually still too fast for my tastes in this respect and by the time 10 minutes has ticked off from the time you started to mix, it's too thick to really use. I usually don't worry at all about strength, I worry about getting things in position properly.
   Type at you later,
    Dan McEntee

If I'm going to use a fast glue then I will take the time to do as many dry fits as needed before I actually apply glue.

Which means that sometimes using "fast" glue isn't any faster than using "slow" glue -- this probably has something to do with why I throw away a lot of mostly full bottles of old CA...
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6823
Re: Fast vs slow drying epoxy
« Reply #14 on: January 26, 2022, 04:16:17 PM »
If I'm going to use a fast glue then I will take the time to do as many dry fits as needed before I actually apply glue.

Which means that sometimes using "fast" glue isn't any faster than using "slow" glue -- this probably has something to do with why I throw away a lot of mostly full bottles of old CA...

   Well, that's the point I'm trying to make, ANY glue joint should be as accurate as possible and fit as tight as possible. That is where the strength is in any glue joint. We are talking about epoxy specifically here, but I think it applies even to Elmer's white glue. If you are a newbie, and are assembling some parts for the engine crutch, and even with having everything you need at hand, but half way through the ten minute alignment job, your 5 minute epoxy that you mixed up because you thought that you could get it all assembled in time, gets about as thick as Play-Doh and the parts don't get put where they belong and parts are not square. That's the beginning of a potential engine run issue because the engine doesn't bolt bolt down flat.  Most warps and alignment issues guys have are because they rushed something or forced something into place to get it there before the 15 minute epoxy set up too thick, which in my experience is about 8 to 10 minutes after you brought the two parts together. You should take the time to do as many dry fits as needed to make it right no matter what glue you are using. The end result is always better. Filling gaps un-necessarily with glue just makes sanding more of a chore and adds excess weight.
   Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)


Advertise Here
Tags:
 


Advertise Here