Adhesive Question?
 

Well, I thought I was in good shape when I bought my repair CA glue for repairs as needed. Was reading my Stinson manual and it said repairs can be made with CA, hot glue, Krazy glue, etc. Why do some planes REQUIRE the use of CA and not others? What is the differemce?

RE: Adhesive Question?
 

Also, Gorilla Glue sells a small applicator of what looks like the old classic Krazy Glue and it has worked well on the plastis pieces too. :-)

RE: Adhesive Question?
 

Some planes are made of materials that are not compatable with CA glue like foam planes..You would need to get a foam safe CA glue Some other materials dont glue well with CA's and somtimes Epoxys work better for strength like on firewalls...I think epoxys work better on foam too..I like to use CA for joints that are cracked loose but still together. It will wick in and glue it like no other glue , ( as long as it is CA safe joint ) I like it for balsa to balsa joints but not so much for hard wood joints...Ca's dont sand well so its better to avoid using them on areas where the joint will show like sheeting joints...Better to use Ambroid or ordinariy wood glue on these joints..I find if I use wood glue for sheating it works good if I dont let it set too long..I would suggest you get yourself an assortment of glues and try them all out..It wont take you long to find out what glues work best in each situation..Every body has there own way of doing things and you will find your own way as time goes on good luck Have fun...

RE: Adhesive Question?
 

Here is a list of adhesives and their applications:

<span style="color: rgb(0, 0, 255);">Thin CA</span> good for balsa to balsa, balsa to plywood, balsa to epoxy glass and balsa to fiber glass
not good for: foam , ply wood to ply wood, ply wood to hard wood, hard wood to hard wood, plastic to plastic or for high stess areas.

<span style="color: rgb(0, 0, 255);">Thick CA</span> Same as above, but used for more a gap filling or for more work time.


<span style="color: rgb(0, 0, 255);">Ambroid:</span> Good for most everything except foam, polyesters and epoxy glass. (We used this for everything before there was epoxy or CAs. )


<span style="color: rgb(0, 0, 255);">5-minute epoxy:</span> Good for Balsa to balsa, balsa to plywood, balsa to epoxy glass , plywood to plywood, plywood to hardwood, hardwood to hardwoood and foam.

Not good for: high stress joints, or use on fiber glass. (5 -min epoxy will not stick to polyester resins.)

<span style="color: rgb(0, 0, 255);">30- minute epoxy:</span> Same as 5 -min epoxy except best used on high stressed parts such as spars and motor mounts, joining foam wings and form stabs. (polyester resin will not cure over 30-minute epoxy)

<span style="color: rgb(0, 0, 255);">White wood glue:</span> Good for: Plywood to plywood, plywood to hardward, foams,
Not good for: laminating balsa to balsa, or laminating plywood to balsa, or anything to epoxy or fiber glass. (white glue is water soluble and will cause balsa to expand. Warping the lamination.

<span style="color: rgb(0, 0, 255);">Yellow wood glue: </span>Good for: everything white glue is good for, plus laminating, and joining wing skins. Not water soluble after it dries.

<span style="color: rgb(0, 0, 255);">Water base</span> contact cement works great for applying wing skins to foam. (if it is white, mix your favorite color of food coloring in it, to be able to see it on the foam and obtain an even coverage.

If you are building a plane that has a fiber glass (polyester resin) fuselage, you must use polyester resin to glue to it.
If you are building a plane that has a epoxy glass fuselage you can use 5-min or 30-min epoxy to glue to it.
If you are using thick CA (Gap filling) or thin CA and you need to kick it, baking soda works well.
If you are going to use polyester resin and glass cloth to wrap around a wing joint, seal the seam (joint) with 5-min epoxy. Polyester resin will not cure over 30 minute epoxy.

DO NOT use large amounts of 5-minute epoxy to join wing halves. The heat generated by the curing process will melt the foam.

There are some exceptions to the above schemes, but these are the general guide lines.

Frank

RE: Adhesive Question?
 

Frank, if the joint is prepared properly, an epoxy joint to a polyester fuse will bond better than a polyester resin will.......especially if a closed process was used. A polyester will bond well to polyester if an open molding process was used. Sand the area, clean it with acetone and bond away.

RE: Adhesive Question?
 

That's true, but NO OFFENSE TO ANYONE HERE, we are working with amatuers here. And the SAFEST route is to use polyester on polyester. And when dealing with a model airplane, where servo rails are glued to polyester fuselage, you really don't want to take the chance of that bond letting go in flight.

In a perfect world, and a controlled environment, you could use the epoxy to bond. but they are two different chemical compunds. Thankfully, most fuselages are constructed with epoxy glass these days, where as 20 years ago, polyester resin glass was widely used.

It's best to use like compounds with like compounds whenever possible.


Be safe, not sorry.

Frank

RE: Adhesive Question?
 

In my experience the safest bet is to use epoxy to bond to a polyester laminate. I did a heap of testing serveral years ago with many resins and found that epoxy sticks to cured polyester laminates better than polyester does. Here is a video clip from one of the test samples: Epoxy to Polyester Bond Strength. In the video you will see that the epoxy bonds to the polyester better than the co-cured polyester lamninate can hold together. The inter-laminar strength of the laminate that was cured together fails before the epoxy to polyester bond fails.

https://vimeo.com/42809730

I'm not trying to be confrontational. The polyester to polyester myth has been floating around for a long time.....especially on RC Universe.

RE: Adhesive Question?
 

Very interesting, however, I am still not convinced. The test did not differenciate if the epoxy was 5 min or 30 minute epoxy. Plus additives such as cavasil and cotton were added to the mix. Second neither break was actually shown in the video. Both broken pieces where glued, then broke. I didn't see the actually parting of the pieces.

How many amatuer modellers sand the surface with 80 grit sand paper, then clean the area with acetone before gluing.

How many of you new people ever thought about sanding with 80 grit or cleaning the area with acetone before glueing? If you have less than years experience, I would dare say that you hadn't even thought about sanding.

Where does glue get it's strenght? From being able to sink into the tiny imperfections of the two surfaces. That why sanding is used. Sanding causes small scratches in the surface, which allows the resins to "bite" into.

If you will notice, the plywood tabs only left wood at the edges, where the resins created a fillet. There was no wood remaining in the center of the tabs.

The glass cloth delaminated from the base and where the glue fillet was, it pulled the glass cloth away from the base where the glass cloth did not bond with the base plywood.

<span style="font-size: medium;">I will say this, epoxy will stick to polyester resin with the right preparation. Sanding and Cleaning. But just using 5 min epoxy alone, your are flirting with disaster. </span>

Frank

RE: Adhesive Question?
 

Polyester is actually a VERY POOR glue. It is CHEAP though. I have used it when appropriate. Wanna glass your cabinets for a durable finish? perfect choice. Wanna glass a boat, perfect choice. Wanna glass a deck so it doesn't rot, perfect choice. Want a structural strength part? Not good. It is also thick and will not wet out the glass cloth very well compared to a low viscosity laminating epoxy resin.

Unlike the word "epoxy", polyester resin is a VERY specific type of glue. Epoxy on the other hand is a very wide far reaching number of glues.

Everything labeled 5 min or 30min epoxy is garbage as well. But it is partially better than polyester resin. 30 min is better than 5.

You get what you pay for.

If the epoxy you are using costs less than $80/gallon in its bulk form it is probably pretty close to garbage. AKA what most people can routinely get their hands on. Likewise any epoxy that is a 1:1 mix ratio is also garbage. These 1:1 ratio epoxies are only made so dumb JOE six pack can easily use the product a not insignificant issue. To get the 1:1 ratio said epoxy is severely compromised in its adhesion bond strength, its tensile strength, its penetration of a surface(wetting) characteristics, and its flexibility.

Any epoxy worthy of the name epoxy, will have at least a 2:1 or greater mix ratio. Even 2:1 mix ratio epoxy is medium run of the mill stuff but it makes for easy mixing. Trying to measure out 2.35:1 or 17:1 is frankly impossible without a scale and a beaker. Typical 2:1 will be some of your readily available laminating epoxies sold by west system 3 and their ilk. Not bad. Good for most jobs. Go to places like Fiberlay.com composites northwest and TAP plastics. Buy a quart and a pint of the stuff respectively, or better yet a gallon and a half gallon and buy the pumps for exactly 1 plunge on the pump from each bucket equals exactly the correct ratio. The more esoteric epoxies while superior to basic 2:1 epoxy are harder for average Joe 6 pack to get their hands on and frankly not worth the hassle for RC airplanes. At least 2:1 epoxy doesn't cure to the substance of a wet noodle like typical 5min and 30 min garbage sold in Hobby shops. Or worse the stuff they sell in the hobby shops or magazines that is extremely brittle and shatters on the first landing.

99.99999% of RC folks will be more than happy with a standard room temp curing 2:1 ratio epoxy. If you want to use it as an engine mount around a jet turbine, well it won't work as its glass transition temperature is too low and one is forced to use an oven cured epoxy or thermalset plastic with fibers imbedded in it.

RE: Adhesive Question?
 

Well if you use polyester on polyester without sanding and cleaning it will still fall off unless you are extremely lucky.

Seems you got lucky and you used a high enough catalyst percentage to allow it to etch said polyester. If you had used very little... FAIL

You got lucky.

RE: Adhesive Question?
 

First off, the laminate bond to the 1/4" ply plate/base never failed in any test including the one in the video. There were 3 layers of 6 ounce glass used. The polyester joints never pulled glass from the laminate with them. The epoxy joints consistently forced a delaminating WITHIN the fiberglass/polyester laminate. I did show the actual breaking of the joint and the joint after breaking.

Not properly preparing any joint, regardless of the resin, is FLIRTINGWITHDISASTER. Every adhesive joint should be properly prepared before joining. Sanding the surfaces and cleaning should be common place even if CA is used. Amateur or not, this is how a good bond is created. If sanding is NOT performed the epoxy still bonds better than polyester but both are weaker. Often people use finishing resin when making polyester laminates. In this scenario the included wax floats to the surface and will mess up any bond. This wax must be removed with solvent and sanding to facilitate a decent bond.

The epoxy resin used in the test video was Adtech 820. I've performed the same test as I showed in the video with Great Planes 5 minute epoxy and the 5 minute epoxy created a better bond to the polyester laminate than the polyester resin. You need to add fillers to epoxy resin like Adtech 820 and polyester resin to prevent the resin from running out the joint. If no fillers (cab-o-sil for example) are used then the bond is much weaker. Making a bonding joint with polyester resin and no fillers and fiber reinforcments (cotton flock) performs much worse than the video demonstrated. The bonding properties of a non-reinforced polyester resin is so poor that dropping it will break the joint.

A bond will always fail at its weakest point. In the polyester to polyester bond you find that the polyester resin used to make the bond fails. Very little of the wood sticks to the bond because the resin is weaker than the birch plywood test tab. In the epoxy bond you see that glass from the laminate was stuck to the plywood test tab. In this scenario the weakness is NOT the epoxy or wood but rather the polyester resin that was used to make the cured glass laminate.

Polyester resin is simply a poor adhesive compare to epoxy. Epoxy sticks to polyester cured laminates better than polyester does.

I will strongly disagree that 2:1 or 1:1 epoxies perform poorly. Hysol 1:1 and 2:1 bonding epoxies are used to glue full scale aircraft components together. It's higher strain and elongation properties allow it to perform better than most laminating resins in a bonding situation. MGS 285 is a 2:1 mix, has a Tg over 200 degrees (when cured properly), and is certified for full-scale aircraft construction. Many higher performance full-scale gliders are constructed with it. It is simply the best performing resin that I have used. It performs better than Adtech 820 which mixes at 100:18. Adtech 820 is a good resin just not as good at MGS 285. I never use the mix ratio to determine a resin performance. The Hysol 1:1 bonding resins still perform better than these excellent laminating resins in bonding applications.

Also, the price of the resin isn't always a clue to the performace. USC 635 is $71 for a gallon and performs better than many $100/gallon resins. See my test results here. In fact, in high strain scenarios it beats the MGS at $230/gallon.

RE: Adhesive Question?
 

I said 2:1 or greater. =) I did state it a bit too emphatically now that I reread what I wrote. =)

Rule of thumbs are just that. Rules of thumbs. Hysol has been around forever. Still better out there, but when you only need "good enough", and there are MANY such applications, then "good enough" is good enough and no sense re inventing the wheel. $$$ trumps all in this case.

Most laminating resins, as you are probably aware, are called laminating resins because they wick(super low viscosity) through fiber and adhere to certain fibers in a superior fashion than a standard cheaper or more expensive structural epoxy. This is especially true of carbon fiber, kevlar, and UHDPE fibers. Glass, not so much. Laminating epoxies are not the end all be all. In fact they are all inferior to structural epoxies. Just an FYI in case you were not aware of this. Judging by your knowledge you probably know this, or should. A top of the line laminating resin will have a tensile yield of 8000psi or greater and a Tg of approx 300F when cured at this temperature of course can push 400F or greater, but generally get into super special resins(thermalset plastics) higher than this.

A quadrillion types of epoxies and glues out there. More than one way to slice a cat. I still have not found common epoxy sold in hobby shops/magazines to be even medium grade stuff. Then again, good enough is good enough. If on the other hand you are trying to build a speed racer out of CF...

RE: Adhesive Question?
 

I'd say more like several dozen which is quite a few actually.

Have you tried Flex Bond? It's a Gougeon Bros 1:1 product and I've found it works rather well for holding my club heads on the golf clubs. Using laminating epoxy for the same job caused premature failure. Laminating epoxy is not a good glue. Point is different products should be used for specific tasks

RE: Adhesive Question?
 

Epoxy laminating resin with fillers performs much better than 5-10-15-30 minute stuff that you get from hobby shops....at least in my testing it has perfromed better.

RE: Adhesive Question?
 

Yup Shock resistent epoxies are different... Sorta, not really. Basic chemical make-up helps. Rule of thumb is that the higher tensile strength said glue is the more brittle it is and the lower tensile strength it has the better it will be for shock resistance. Low tensile glues are all very cheap. Under 3000psi glues unless they are Very special applications for odd materials are very cheap. Likewise one can take a high tensile/high adhesive bond glue and add fillers and get the same or better results. Essentially it comes down to fillers. Get the ol' curves for filler and shock resistance verses adhesion bond strength of various materials verses tensile strength verses temperature. Such information is Very hard to get ones hands on. If you use Huge amounts of glue then yes, it is cheaper to buy cheaper lower tensile adhesives for certain applications. If one is a common RC modeler, then one does not use that much adhesives and one is better off buying a high quality product and using it for all applications, other than CA super fast glues. This way it covers all of their applications and needs.

Few dozen families of adhesives and basic chemical make up is what you meant I hope? In each family you can have everything from UV cured MAS to ultrasonic cured MAS or epoxy UV cured or phenolic or... The term "epoxy" itself isn't exactly an accurate descriptor.

Flex Bond. Everyone has a "Flex Bond" Its a PR sticker. Its not a base adhesive name brand as far as I know. Maybe when someone came up with it in 1950. "Whatever" that was. Hysol is a company that makes everything under the sun as well as their original product which is very cheap, but run of the mill stuff. As far as I know, there is no such thing as a Flex-Bond family/company of adhesives. I may not be old enough to know this specific information. Sorry don't get what you are getting at other than the Flex Bond you are describing seems to have excellent shock resistance for use on golf club heads.

RE: Adhesive Question?
 

I love it. Now I can watch epoxy debates just like the oil debates [8D]

In a major crash the only thing remaining on some of these planes will be the epoxy.

RE: Adhesive Question?
 

FWIW and I'm no expert, but I've been using System Three's T-88 for bonding.http://www.systemthree.com/store/pc/T-88-c27.htmIt is a structural adhesive not a laminating resin and it's mixed in a 1 to 1 ratio. I was looking for a good structual epoxy and went to the Aircraft Spruce and Specialty store and they recommeneded T-88 as the best.

From theSystem Three Website -
T-88 is a high-performance, non-brittle, two-part epoxy adhesive designed to give superior results under adverse conditions. The adhesive may be used without modifications in normally fitted joints, and will cure in any thickness without shrinkage. T-88 is clear amber and becomes virtually invisible when varnished. T-88 exhibits outstanding adhesion and permanence on a wide variety of materials, and is endorsed by leading designers, builders and organizations.

There's also a great read on epoxy for those who will invest the time to actually read it. It's also from the System Three website and is called The Epoxy Book. See attached pdf.

The most important thing to do when using epoxy on polyester is to remove any wax leftover from when the polyester cured and to sand the polyester area very well. This is a quote form page 4 of The Epoxy Book;

<font color="#231f20" size="2" face="OfficinaSans-Book"><font color="#231f20" size="2" face="OfficinaSans-Book"><font color="#231f20" size="2" face="OfficinaSans-Book"><p align="left">"Caution must be observed when using epoxy resins along with polyester resins . Observe the general rule that epoxy resins may be applied over cured polyesters that have been dewaxed and well sanded but polyesters should never be used over cured epoxy resins.

I will yeild to the experts at System Three before I'd listen to anyone here including myself, unless of course those claiming the epoxy information post credible links to verify what they claim.

One of the best features of T-88 is you can heat it up to 150 degrees F to increase the set timeto 30minutes without loosing structual integrity. I've been using this adhesive for the last 3 years and it works great on gluing wood to polyester laminates.</p></font></font></font>

RE: Adhesive Question?
 

What I thought too, since some of my filled laminating epoxy efforts held up well under stress. Firewalls and landing gear blocks come immediately to mind. So my first attempt at gluing the driver head on the shaft was with filled laminating epoxy. Lasted exactly 12 drives...on the 13th, the head flew further than the ball...LOL

BigFoot, never said that FlexBond was a class or family of epoxy glues. It is West Systems offering for "flexible" high strength epoxy glue

RE: Adhesive Question?
 

I'm in the middle of putting together an old jet kit & have now realised that its polyester resin glass fuse may need specific glues to work well..
How does the System Three's T-88 Epoxy work with Polyester? Seems to sound good on their spec sheet.. but in practice, anyone using it?

Thanks

RE: Adhesive Question?
 

reaaz,

The rule is you can put epoxy over polyester but not polyester over epoxy as the polyester will not cure next to the hardened epoxy.

That being said System Three's T-88, as far as I'm concerned, would be the perfect adhesive for your polyester jet. I have even used the T-88 as a laminating resin by heating it in a microwave for 7 or 8 seconds then pouring onto the fiberglass and spreading easily with a 1inch wide brush. When warm it's very thin and runny. Don't heat more than 5 or 10 grams at a time cause it will hardened very fast after heating it. I used this procedure to make a plug out ofpieces of an OK Models P-51 plastic cowling that got smashed flat.

Above all elseyou need to observe theserules for successful use of epoxy laminating resins and epoxy adhesives.

1. Use a scale to measure the weights. If the epoxy uses 2 parts resin to 1 part hardener the more accurate the mix the better the results
2. Mix thoroughly, first mix in one mixing container then tranfer those contentsto another containerto make sure the resin and hardener is completelymixed.
3. Never use the resin below the minimum temp. If the directions say do not use below 65 degees, don't try use it when room temp is 65 or below. Room temp needs to be above the minimum temp for the duration of the curing process. If the epoxy system you use has a 30 min cure time, theroom temp needs to be above the minimum for 30 minutes. If the epoxy system you use has a 4 hour cure time, theroom temp needs to be above the minimum for 4 hours.
4. If the resin is a milky color those are resin crystals and the resin needs to be heated to about 80 degrees so the crystals are back to a liquid state.
5. Carb-o-sil will not affect the strength of the bond but <font color="#231f20" size="2" face="OfficinaSans-Book"><font color="#231f20" size="2" face="OfficinaSans-Book"><font color="#231f20" size="2" face="OfficinaSans-Book">
Microballoons and microspheres will andshould not be used in adhesive formulations as they reduce tensile strength.
6. Most epoxy that is mixed correctly will be sandable the next day this includes T-88.

Read Section VII-D Bonding with Epoxy in the pdf attachment inpost 17above for more details.</font></font></font></p>

RE: Adhesive Question?
 

If you chose to mix by weight you typically cannot use the volume mix ratio since the density of the resin and the hardener are not the same.  Most resin manufacturers will give the volume ratio and weight ratio separately.

RE: Adhesive Question?
 

wyowindworks

Yes. You can get and use the wieght ratio's vs the volumn ratio's. My point was that the correct ratio should be used regardless of weight or volumn. You shouldn't try to eyeball how much you are going to use.

I find for me that using a jewelers scale when mixing small amounts works fine. It also is really hard to mix by volumn when you are using small amounts so using a jewelers scale has given me constant repeatable results. Generally when using epoxy adhesive resin vs epoxy laminting resin you will be mixing way smaller amounts. So agianwhat's most important isusing the correct ratioeither by volumn or weight..

T-88 uses a 100/83 Resin/Hardener weight ratio and a 100/100 ratio by volumn. As you say consult the TDS sheet of the product you're using.

Here's the TDS for T-88 for those interested.


</p>

RE: Adhesive Question?
 

One more thing as far as rules to observe.

7. When appling epoxy to polyester you need to sand the polyester very well for maximum adhesion.</p>

RE: Adhesive Question?
 

Guess what LOL, medium CA with no kicker layups works better, sticks better and holds up better on repairing fiberglass cowlings and wheel pants made from poly or epoxy. The only thing that is a must is your parts must be clean, oil free, and lightly abraded but that would be the case on any repair. All you need is a bottle of medium CA, a few tailored cut pieces of the fiberglass cloth of your choice, acetone, and a rag for keeping your fingers clean. Place a few drops of CA on the repair area, spread with finger tip, place first ply using finger tip and added CA for wet out, place second ply and so on, usually only 2 or 3 plies of 4-6 oz. in narrow strips over the damage area is more than enough, when your all done just spray one shot of kicker over the area and your ready to move on. For repairing holes just place masking tape on the outer mold line of the cowl/wheel pants and go for it. Anyway, don't take my word for it; spend a few minutes and try it out for yourself after a couple of times many will never go back to anything else. Just saying...

Bob

RE: Adhesive Question?
 

Bob,

Great tip for a fast put together.

Just so you know there is a differencebetween using CA and epoxy. I doubt I will convince you but using CA as a laminating resin in the way you suggest will work for small parts that do hot require structural strength. The problem with CA is when you spray it with kicker it becones very brittle. Letting the CA dry without the kicker would be only slightly better for structural strength.

For structural strength nothing beats epoxy other wiseCAwould be the goto glue for carbon fiber wings for the stealth figher and bomber instead of epoxy.