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Which Epoxy?

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Old 07-14-2012, 06:19 AM
  #1
mark IX
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Default Which Epoxy?

Hi Guys, do any of you know what would be a good epoxy to glue hardwood or balsa to a fiberglass cowl? More specifically, I am building Brian Taylor Spitfire Mk IX and when gluing the cowl to the balsa fuse I accidently banged the assembly and much to my surprise the (Bob Smith Industries) 5 minute poxy did not hold. [] It seems to be too brittle when cured. Any Ideas what would be a better epoxy for this application?

Thanx, Mark
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Old 07-14-2012, 06:34 AM
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Default RE: Which Epoxy?

I've always used the pacer zpoxy and it works rather well for most things that i do. It's avalible in both 5 min and 30 min variety's. Hope this helps

JM
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Old 07-14-2012, 06:49 AM
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Default RE: Which Epoxy?

In general, the longer the cure time, the stronger the epoxy. Epoxy gets its strength from the length of the molecular chains that form as it cures; the slower the cure the longer the lengths thus stronger.
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Old 07-14-2012, 09:16 AM
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Default RE: Which Epoxy?


Quote:
ORIGINAL: mark IX

Hi Guys, do any of you know what would be a good epoxy to glue hardwood or balsa to a fiberglass cowl? More specifically, I am building Brian Taylor Spitfire Mk IX and when gluing the cowl to the balsa fuse I accidently banged the assembly and much to my surprise the (Bob Smith Industries) 5 minute poxy did not hold. [] It seems to be too brittle when cured. Any Ideas what would be a better epoxy for this application?

Thanx, Mark
How much surface prep did you do?.. I have short-cutted before and did not scuff an area well enough in preparation for the epoxy and parts and ended up having the same thing happen.. It could have been a bad mix of epoxy, poor preparation, or a combination of the two I would think. If I am not off base here, I beleive that fiberglass parts will often times have some kind of breaking agent on the inside still from when the part was molded. That can play a part in the insufficient bond between parts if it is not thoroughly removed and the area scuffed up.

Also, Iuse the epoxy that one can get from an Ace Hardware or equivalent and have had no problems unless it was my fault, namely poor preparation. I use the 30-min for high load areas and 5-min for things that won't stay put with CA but do not bear much stress like a flying surface or firewall does.. 5-min for fuel proofing as well..

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Old 07-14-2012, 09:32 AM
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Default RE: Which Epoxy?

Epoxy will not stick to fiber glass / polyester. Unless you really scuff the area up and make it very rough for the slow curing epoxy to bite into.

Otherwise, polyester resin will need to be used. It sticks to itself better than anything else.

Frank
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Old 07-14-2012, 10:39 AM
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Default RE: Which Epoxy?


Quote:
ORIGINAL: Mk23socom


Quote:
ORIGINAL: mark IX

Hi Guys, do any of you know what would be a good epoxy to glue hardwood or balsa to a fiberglass cowl? More specifically, I am building Brian Taylor Spitfire Mk IX and when gluing the cowl to the balsa fuse I accidently banged the assembly and much to my surprise the (Bob Smith Industries) 5 minute poxy did not hold. [] It seems to be too brittle when cured. Any Ideas what would be a better epoxy for this application?

Thanx, Mark
How much surface prep did you do?.. I have short-cutted before and did not scuff an area well enough in preparation for the epoxy and parts and ended up having the same thing happen.. It could have been a bad mix of epoxy, poor preparation, or a combination of the two I would think. If I am not off base here, I beleive that fiberglass parts will often times have some kind of breaking agent on the inside still from when the part was molded. That can play a part in the insufficient bond between parts if it is not thoroughly removed and the area scuffed up.

Also, Iuse the epoxy that one can get from an Ace Hardware or equivalent and have had no problems unless it was my fault, namely poor preparation. I use the 30-min for high load areas and 5-min for things that won't stay put with CA but do not bear much stress like a flying surface or firewall does.. 5-min for fuel proofing as well..


I agree that prep is key followed by the quality of epoxy. IMO any of the 1:1 hobby epoies are junk and should not be used. When I bond to a fiberglass fuse the formers NEVER come loose. I first sand the area really well with 150 grit. Dust off and clean well with acetone. Allow the acetone to flash off for 1/2 our or so. Mix up some laminating resin. West systems is pretty much the most readily available but there are several good brands available. A great place to look is Aircraft Spruce and Specialty or ACP. Z- Poxy would be a last resort for me. Mix some milled fibers and cab o sil in with the epoxy to make a paste. With a sheet of paper you can make a cone ( think cake decorating here ). Put the slurry of epoxy in the cone and apply the slurry to the edge of the former. Place the former in it's location. Now wait until the epoxy has set just enough so that it wont move as you do the next step. You want the epoxy to be a bit green ( semi cured ) so that you will get a molecular bond during the next step. Mix up another batch of laminating resin and split it in two cups. In one cup mix up another slurry of milled fibers and cab o sil. Take another cone and make a 1/8 fillet at the corner of the former and glass. Smooth out with your gloved finger. Take a strip of 1" 4 oz cloth and cover the blended corner with it and brush on some strait resin. After 24 hr cure at 70 degrees or better, that former will be there forever.

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Old 07-14-2012, 11:51 AM
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Default RE: Which Epoxy?

I use either or both hysol 6942 or gorilla glue,it take a little longer to cure but when it does its there for good.
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Old 07-14-2012, 06:23 PM
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Default RE: Which Epoxy?

I agree with the hysol and gorilla glue, better than any epoxy. Also there is goop. That stuff holds to anything and super strong. I use that for bulk heads to glass with out the prepping you have to do with epoxy and you not going to pull them out ever.
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Old 07-15-2012, 06:55 AM
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Default RE: Which Epoxy?

I agree with Speedracerntrixie.
If you are gluing anything structural or important, use ONLY laminating epoxy and use it correctly. This is more work than just slapping some glue on it and sticking it together, but the results are well worth the trouble. Surface prep really is the key. I use West 105 with slow hardener. It takes a while, but I never want to worry about a failure when I am abusing one of my planes. I usually make firewall or landing gear block installations the last thing I do on a build day, and the glue will be dry the next day.

Bottom line, you can not take shortcuts with structural bonds and expect things to stay together.

Good luck
Scott
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Old 07-15-2012, 08:03 AM
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Default RE: Which Epoxy?

Hi!
I'm too building the Bryan Taylor Mk 9, 84" Spit but I haven't seen anything about glueing the cowl to the balsa fuselage?? I think Brian ment them to be screwed on.
I wouldn't use 5-30min glue epoxy for anything on that plane. Much better to use laminating epoxy (24 or 30 hours) as this is much more stronger and harder (easier to sand) than ordinary glue epoxy.
West Systems work ok but there are better epoxies out there of you search the web.I use this epoxy when making both molds and covering balsa wings and fuselages. Made a new Spitfire Mk 9 cowl which is much lighter than the stock polyester glass fiber mat cowl.

http://www.emc-vega.de/en/composite-materials/epoxy
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Old 07-15-2012, 09:28 AM
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Default RE: Which Epoxy?

Guys, thanks for the all of the responses. I know about properly prepping the fglas, but the cowl is already rough and textured on the inside, I thought that would be good enough. Gonna try the the Gorilla glue or Goop....................I'll let you know.......

Thanx, Mark
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Old 07-15-2012, 11:50 AM
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Default RE: Which Epoxy?

Hi!
Gorilla glue (Polyurethan) is not suitable for that!
And the texture on back of the cowl isn't good enough for glue to stick well on. Ther is ax residue left over from the molding. You have to sand the surface to make glue stick well to it.
But why glue it on???
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Old 07-15-2012, 12:09 PM
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Default RE: Which Epoxy?

Maybe he is referring to a hard wood ring that attaches to the cowl on the inside so that it could be screwed on to the fuse. Some designers use that method because you see no screws around the cowl on the outside. Some times a pain to set up right but looks good. Also gorilla glue does work. I have done it on a glo H9 T6 and a diesel CMP P47. Both cowls the gorilla held fast even with all the oil in the cowl. Of course the tabs were done when new before the oil splatter.
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Old 07-15-2012, 12:51 PM
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Default RE: Which Epoxy?


Quote:
ORIGINAL: mark IX

Guys, thanks for the all of the responses. I know about properly prepping the fglas, but the cowl is already rough and textured on the inside, I thought that would be good enough. Gonna try the the Gorilla glue or Goop....................I'll let you know.......

Thanx, Mark
Mark is is rough but that is just the texture of the cloth. It is not a good surface to bond onto. The most obvious is that resins contain solvents that will come to the surface during cure. This will leave a thin film that will inhibit bonding. The sanding will create a multitude of fine scratches and open pores to get a good mechanical bond, the acetone will wash away any contaminates. Do not skip the prep process as it will just lead to failed joints later. I would also reccomend against using anything but epoxy and the process I have discribed earlier. Having a bad landing is bad enough but when it leads to having something pop loose because of a poor bond during building will cost you much more time to repair then it will to do it correctly now. Especially if the area has been subject to fuel residue. Please consider what I am saying, Not only do I use these methods on my models but I am a composites tech by trade.

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Old 07-15-2012, 05:47 PM
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Default RE: Which Epoxy?


Quote:
ORIGINAL: speedracerntrixie


Quote:
ORIGINAL: mark IX

Guys, thanks for the all of the responses. I know about properly prepping the fglas, but the cowl is already rough and textured on the inside, I thought that would be good enough. Gonna try the the Gorilla glue or Goop....................I'll let you know.......

Thanx, Mark
Mark is is rough but that is just the texture of the cloth. It is not a good surface to bond onto. The most obvious is that resins contain solvents that will come to the surface during cure. This will leave a thin film that will inhibit bonding. The sanding will create a multitude of fine scratches and open pores to get a good mechanical bond, the acetone will wash away any contaminates. Do not skip the prep process as it will just lead to failed joints later. I would also reccomend against using anything but epoxy and the process I have discribed earlier. Having a bad landing is bad enough but when it leads to having something pop loose because of a poor bond during building will cost you much more time to repair then it will to do it correctly now. Especially if the area has been subject to fuel residue. Please consider what I am saying, Not only do I use these methods on my models but I am a composites tech by trade.

What he says Prep is the key to success. Water wash, Acetone wash, sand, acetone wash again.

But do not use polyester [ it is well established that polyester resin does not bond well to cured grp ] or gorilla glue. Epoxy only.
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Old 07-17-2012, 12:08 PM
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Default RE: Which Epoxy?

Ok, I tried the Gorilla glue with a piece of scrap w/o any prep. It looks like to joint is holding pretty good, much better than the 5 min epoxy. I noticed the Gorilla glue did not dry brittle but remained rubbery. Is this normal? Next I will try GOOP.

Thanx, Mark
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Old 07-17-2012, 04:00 PM
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Default RE: Which Epoxy?

Which one did you use? The white or brown? If it is soft it may not have cured fully yet. The brown one takes longer to dry but I think is stronger than the white one. The brown I use for fire walls and landing gear blocks. And did you clamp the parts together? With gorilla glue you should because the expansion will move the part. To get nice solid bonding clamp when using either goop or gorilla glues. More so the Gorilla glue unless the part is wedged in and will not move.
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Old 07-17-2012, 06:20 PM
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Default RE: Which Epoxy?

I used the white version. And yes I clamped it together. I'm waiting for the Goop (purple tube, dries clear) to cure overnight.

Thanx, Mark
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Old 07-18-2012, 06:32 AM
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Default RE: Which Epoxy?

The brown and white Gorilla glues DO NOT DRY, they cure; a chemical process where the H2O in the atmosphere or on the object being glued combines with the products in the glue forming a new compound.
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Old 07-23-2012, 08:57 AM
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Default RE: Which Epoxy?

Looks like the Goop is the stronger bond w/o any prep any. I am going to try the prep outlined above with the 5 minute epoxy again to see what difference it makes. Stay tuned.........

mark
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Old 07-23-2012, 01:54 PM
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Default RE: Which Epoxy?


Quote:
ORIGINAL: countilaw

Epoxy will not stick to fiber glass / polyester. Unless you really scuff the area up and make it very rough for the slow curing epoxy to bite into.

Otherwise, polyester resin will need to be used. It sticks to itself better than anything else.

Frank

Wyowindworks posted a video of just the opposite and it's been my experience epoxy bonds better to polyester than polyester does.

Ken
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Old 07-23-2012, 03:56 PM
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Quote:
ORIGINAL: mark IX

Looks like the Goop is the stronger bond w/o any prep any. I am going to try the prep outlined above with the 5 minute epoxy again to see what difference it makes. Stay tuned.........

mark

Why not try quality epoxy on the prepped surface? 5 minute epoxy is like putting Pep Boys tires on Dale Jr's car to prove that Jimmy Johnson is faster.

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