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Author Topic: glue  (Read 817 times)

Offline Dan Berry

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glue
« on: January 12, 2018, 09:27:13 PM »
Well, I have a situation.

I glued the doublers on a Vector40 kit. I used my West Systems epoxy and it isn't working. Either the glue has gone bad or I mixed it wrong.
It is only mostly cured. The dross in the cup and on the brush are rubbery. I am less than excited about trying to separate the pieces and I think it would be easier to duplicate things.

The question is---- do I want 6lb wood for the 3/32 sides or maybe something a bit heftier?


Offline Motorman

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Re: glue
« Reply #1 on: January 12, 2018, 09:33:11 PM »
If you're willing to wait it may fully cure with more time.
There will be a sunny day and we will fly our airplanes.

Offline Dan Berry

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Re: glue
« Reply #2 on: January 12, 2018, 09:38:02 PM »
It has been five days.

Offline Mike Griffin

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Re: glue
« Reply #3 on: January 12, 2018, 10:41:07 PM »
Hi Dan

As far as the problem you have right now, you might try to use a heat gun and warm the glue up and see if you can separate the doublers from the balsa and that may or may not work.  At this point, it would not hurt to try.  If it doesn't then cut new pieces.

I have been using West Systems Epoxy for years (both fast and slow set) and have only had this problem once and it was because the mix wasn't right.  The metered pumps on the resin and hardener are metered to dispense the exact right amount of each to make the epoxy set up right.  I have found this to be critical when using this stuff.  I always do a squirt of each to eliminate the air in the pumps before i mix them together.  You may know all this already and just disregard if you do.

It is the best expoxy I have ever used but mixing ratios seem to be critical. 

Mike

Offline Matt Spencer

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Re: glue
« Reply #4 on: January 12, 2018, 11:07:16 PM »
If the sheds real cold , it may take forever to cure .

Was Told the west sysyems base was same as ayraldite , but with space fillers to make it lighter .

Ayraldite it is critical to mix say thee times over a 20 minute interval . at zero Deg. C , it can take 48 Hrs to fully kick off .

I think you should sit it in the sun for a few days .

( was at the lecture in 60s when agent instructed pater on this new fangled aryldite , was actually " must be mixed for thirty minutes before use "

Q. you dont have to mix it for thirty bl**dy minutes , do you

A No , but you should stir it two or three times , over that ( many minutes )

SO , if its COLDER ( Than 16 Deg , which was wot the AEROLITE required as minimum  ) it should be stirred ' in the pot ' of and on , for longer .

Of Course Heating in the pot , a jar in boiled water , gets it mixing & runney , quick . But itll kick off quick , so you need to be quick too , and prepared .
No time for hunting for ' now where did I  . . . ,  >:( :-[ LL~

Offline Dan Berry

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Re: glue
« Reply #5 on: January 13, 2018, 06:51:19 AM »
The room is heated. I'm reasonably certain that I got the mix wrong. I'll try the heat gun to separate them.
Yay.

Offline Gerald Arana

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Re: glue
« Reply #6 on: January 13, 2018, 08:58:30 AM »
The room is heated. I'm reasonably certain that I got the mix wrong. I'll try the heat gun to separate them.
Yay.

Dan,

I have taken fully cured epoxy/fiberglass off of balsa surfaces for repairs to my competition gliders. It should be a fairly easy fix for you.

And after I removed the FG, I kept the heat on and scraped the residule epoxy off the mating surfaces.

Let us know how it worked for you, Jerry

Offline frank williams

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Re: glue
« Reply #7 on: January 13, 2018, 09:31:06 AM »
Hi Dan
I had the same thing happen a couple of months ago.  I use West fast to fuel proof engine and tank compartments, not so much  for joining pieces.  I have never had a problem with curing before.  It always kicks off no matter the temperature.  I'm still not sure what I did, but it must have been an incorrect ratio that one time.  I generally weigh the ratios on a small gram scale so as not to have to waste a full pump of resin for a small job.  It never cured.  I finally wiped it off with acetone the best I could and coated it over with a fresh correct mix. Before the second coat I experimented and practiced several times to make sure that I could still get a good mix.  My fast hardener has long since turned a purple color but it still works well.  I think you could probably pull the parts apart, scrape and wipe with solvent and try again.
Frank

Offline john e. holliday

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Re: glue
« Reply #8 on: January 13, 2018, 10:17:16 AM »
A gentleman I used to fly with had problems with epoxy mixes not curing once in a while.  He would take the heat gun and start warming it up.   I even saw him put it in a closed car with windows rolled up sitting out in the bright sun light.   He stated the closed car in bright sun light worked much quicker even when temps were freezing. D>K
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Offline Dan Berry

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Re: glue
« Reply #9 on: January 13, 2018, 10:26:05 AM »
Hi Dan
I had the same thing happen a couple of months ago.  I use West fast to fuel proof engine and tank compartments, not so much  for joining pieces.  I have never had a problem with curing before.  It always kicks off no matter the temperature.  I'm still not sure what I did, but it must have been an incorrect ratio that one time.  I generally weigh the ratios on a small gram scale so as not to have to waste a full pump of resin for a small job.  It never cured.  I finally wiped it off with acetone the best I could and coated it over with a fresh correct mix. Before the second coat I experimented and practiced several times to make sure that I could still get a good mix.  My fast hardener has long since turned a purple color but it still works well.  I think you could probably pull the parts apart, scrape and wipe with solvent and try again.
Frank

The parts aren't gonna pull apart easily. The glue has cured to a state of elasticity. I'm gonna try to separate them.
I'm also thinking that I could plane and sand away the doublers and only need to replicate them.

Offline Target

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Re: glue
« Reply #10 on: January 13, 2018, 12:55:20 PM »
Hi Dan
I had the same thing happen a couple of months ago.  I use West fast to fuel proof engine and tank compartments, not so much  for joining pieces.  I have never had a problem with curing before.  It always kicks off no matter the temperature.  I'm still not sure what I did, but it must have been an incorrect ratio that one time.  I generally weigh the ratios on a small gram scale so as not to have to waste a full pump of resin for a small job.  It never cured.  I finally wiped it off with acetone the best I could and coated it over with a fresh correct mix. Before the second coat I experimented and practiced several times to make sure that I could still get a good mix.  My fast hardener has long since turned a purple color but it still works well.  I think you could probably pull the parts apart, scrape and wipe with solvent and try again.
Frank

Like Frank, I throw the pumps away. They let air into the glue while storing and even if you replace the can caps they are a mess to deal with.
With the $20 Harbor Freight gram scale (which comes in handy for lots of other things) I can mix batches as small as 7grams (5g resin + 2g hardener) and they always cure properly.
https://www.harborfreight.com/digital-scale-95364.html
While at Harbor Freight I buy the 6-pack of plastic squeeze bottles for condiments, the ones with the cone shaped nozzles and little red caps. I put resin in one bottle labled as such and slow hardener in the other, and fast hardener in the other. Works much better.
https://www.harborfreight.com/pack-of-3-8-oz-storage-bottles-with-twist-caps-66170.html
I also buy a stack of 300 or 500 Dixie cups from the CVS or Rite Aid for about $3 to mix in.

MGS epoxy is much more expensive, but WAY better than WS...It is almost like water when mixed. Not a big deal for regular gluing, but for fiberglassing it is much better it wets out the fabric better and you can always add colidal silica if you need it thicker.
http://www.aircraftspruce.com/catalog/cmpages/mgsresin.php?clickkey=127058

For bonding, WS's G-Flex is great. I use it for gluing servo trays into carbon RC Sailplanes and similar jobs. For control line, that is what I would use for laminating the doublers.
It takes a 1:1 ratio. It's pretty expensive per oz, but works great for bonding and is not brittle when cured.
http://www.aircraftspruce.com/catalog/cspages/gflex3.php?utm_source=bing&utm_medium=cpc&utm_campaign=CPCS%20-%20Shopping%20-%20NB%20-%20Desktop&utm_term=4580977758698486&utm_content=All%20Products

WS softens at about 140F, try the heat to get your parts apart Dan. Good luck, I hope you can get it fixed. Obviously a test batch is in order now after you get it back apart.

Electric blankets over the the glued parts is a good way to cure them after epoxy is applied.

Very Respectfully,
Target
Regards,
Chris
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Offline Fredvon4

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Re: glue
« Reply #11 on: January 13, 2018, 02:23:47 PM »
Long ago I worried that volume vs weight for mixes that were not 1:1 might be a problem

Had the pumps for west systems but so very rarely used them I was never confident that after 8 to 13 months of non use they would regulate properly

Being a ammunition reload guy I have a variety of good manual and electronic scales

The ratio math on most epoxies is easy to figure for good electronic scale

I have not had a glue failure to cure for many years now using mix by weight vs mix by volume

especially at the usually LOW volumes we mix for....

That all said...for perfect weight ratios YOU must know that part A is XX  weight per ML and Part B is XX weight per Ml and the ratio mix is 2:1 or whatever

some epoxies give you the ratios both by volume and weight....so just pay attention and ask Tim W or others here on how to convert,,,,Howard Rush probably has a comprehensive spread sheet for any Ratio that can be considered

Brett Buck can probably assist with Coriolis effect and relative humidity in a -10 vacuum at 35C as related to kick of of any common exothermic glues
"A good scare teaches more than good advice"

Fred von Gortler IV

Offline Target

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Re: glue
« Reply #12 on: January 13, 2018, 02:37:52 PM »
I agree with what you say above, Fred.
But, from my real world experience, with both MGS and WS that I have mixed down to 2-3g batches (with a 0.xxg scale) I haven't had a batch not cure yet.
Larger quantities should be MORE tolerant of a slight deviation as the percentage of error should be smaller.

So, that must mean that the density of the resin and hardener are very close, and in real world, close enough not to matter.

The pumps are a crude, crude, method of measuring in the first place, and they were not made for the smaller quantities that we want to use. How often do you need a whole pump of product?

You can use the pumps still if you want to weigh the product being dispensed. That is the only way I would trust it. But after doing it the way I have been, there is no going back for this guy. It works much better for me.

FYI, I flew yesterday. Wearing shorts! I had a great time.
I hope the rest of you all are staying warm.
We here had our mudslides and fires here though, and the smoke was BRUTAL last month, I am sure you all saw that in the news.
And, the traffic is ever-worsening....
Your TD parts have been utilized on one AP wasp so far. Thanks so much for that!!!
Regards,
Chris
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Offline Steve Helmick

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Re: glue
« Reply #13 on: January 13, 2018, 05:38:37 PM »
Warm up the parts but don't try to separate the laminations. I'd probably lay a piece of steel on the lams and heat that up with a torch or heat gun. I'd bet the glue will harden up just fine. If it doesn't, then you can punt. I might even consider calling up West Systems and ask what they'd suggest!  :-\ Steve
In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.

In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

"Be polite, be professional, but have a plan to kill everybody you meet." General Mattis.


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