Epoxy or Thin CA?
 

What should be used to join the fiberglass strip over a wingjoint? Should I use alcohol-thinned epoxy, or thin CA? This is the 2" fiberglass strip joing the wings of a 4*60.

RE: Epoxy or Thin CA?
 

One word answer Epoxy

RE: Epoxy or Thin CA?
 

Thanks for such a quick reply. If epoxy, then should I use 30 min or 5 min?

RE: Epoxy or Thin CA?
 

Use the 30 min, 5 min will not give you enough working time.

RE: Epoxy or Thin CA?
 

Ideally, you would use laminating epoxy or finishing epoxy. The epoxy glues are not really intended for laminating fiberglass. The glue doesn't really set through if it's too thick, but the laminating stuff will. If you really want to use the glue, use the 30 min. The 5 min will be gelled long before you have it worked into the glass cloth properly.

A decent hobby shop will have laminating or finishing epoxy. If not, try a hardware store. I got some Bondo brand laminating epoxy at OSH once that works quite well. This epoxy will take several hours to cure, giving it time to soak into the wood, strongly bonding the glass and wood together.

RE: Epoxy or Thin CA?
 

Thined epoxy gets brittle , only use for fuel proffing. Use full strength and use a heat gun to flow out. Watch and do not over heat or it will bubble and be hard to finish.

RE: Epoxy or Thin CA?
 

2 hour epoxy is close to the laminating epoxy. (not exactly the same stuff, but same consistancy, and works better than 30 min for fiberglassing)

Slower cure epoxies are less tollerant of the mix being off a small amount. You must carefully measure 2hour epoxy in medicine cups, DO NOT COUNT DROPS! The drops for the 2 parts are not the same size! If yo are off just a little on the proportions, the epoxy will remain tacky for up to 5 days. If it stays tacky longer you have a problem. (it very hard to clean the unset epoxy out of the wood.)

It is very easy to use excess epoxy when fiberglassing. You apply the epoxy to the wood, then scrape it off with a credit card. then lay on the cloth. Then carefully rub the cloth down smooth (wear gloves...) Any place the cloth does not turn transparent you need a little more epoxy. (try to rub from a place that is transparent toward the white... THEN apply a tiny bit of epoxy if needed.)

Excess epoxy does not add strength, just weight.

RE: Epoxy or Thin CA?
 

Hate to be the odd man out here... but...

I've used CA occasionally on wing center section fiberglass and it's always been fine.
Also epoxy, thinned epoxy, and epoxy finishing resin. They all worked (e.g., never had a wing failure - of any kind - yet). Easier to get a smooooth finsh w/ the epoxy though.

I'd also think REAL hard about extending the center section reinforcement about 1" past the fuse sides; I beleve the points of max stress on a wing are at the juncture of the wing and fuse.

Best technique I've seen for doing a center section (this on a 2 meter plane) is to use about 3 layers of 2 ounce cloth, first 4"wide, second 6" wide, third 8" wide -- and a layer of 3/4 a little wider than that for a smooth finsh.
Apply all the layers at once - with finshing resin (Smooth n Easy or Z-poxy are both on the shop shelf), and smooth/ remove excess resin while wet - very little sanding needed before ironing on the covering.

Just my $.02

RE: Epoxy or Thin CA?
 

I also use Thin CA, just wear a mask or something, be careful with the fumes.

RE: Epoxy or Thin CA?
 

Use 30 minute or slower epoxy. Do not try to thin it, just heat it with your heat gun after applying the epoxy and it will flow out nicely. Next, wrap the entire area in Saran Wrap (a kitchen item) and smooth it down with your hands working out any wrinkles and feathering the edges. Let it cure and then peel off the Saran Wrap. The surface will be smooth as a baby's but and will require no sanding.

RE: Epoxy or Thin CA?
 

I like to use the 30 minute epoxy ,but I heat it up in the micro wave for about 15 sec's becomes thin as water--flows out nice ..Kicks off a litte quicker. Make sure you have all the necessary equipment ready.Wear gloves ,mask off the area not being treated..

RE: Epoxy or Thin CA?
 

For those of you heating your epoxy, be very careful you don't heat it up too much. The curing process of epoxy is exothermal, meaning it generates heat all by itself. We generally do not notice it because we typically only mix up small batches. We also spread it out soon after the epoxy is mixed, so the heat has plenty of surface area to dissipate.

However, I had once mixed up epoxy in a Kodak film canister 1/2 full, let it sit a few minutes while I prepare the balsa airframe, and to my surprise, saw smoke starting to come out of the film canister. I quickly held my breath and hauled the smoking epoxy outside the house. In less than 5 minutes, I watched the epoxy melt the canister into a puddle of goo.

Once cured, epoxy is fairly harmless, but the fumes from curing epoxy is hazardous. The smoke from burning epoxy, such as what I saw, is extremely toxic. I've since quit using film canisters. I now use these little clear plastic bowls from fruit jelly snacks. These are bowl shaped and so offer the epoxy much great surface area to dissipate heat. Heating the already spread out epoxy with a heat gun is okay, but if it is my lungs and those of my family, I wouldn't take the chance of heating epoxy in microwave, based on my experience.

Use the right tool for the job. If you're laminating with fiberglass, use finishing epoxy. Whatever you do, watch the temp on that epoxy cup!

RE: Epoxy or Thin CA?
 

I agree with Volfy. Be very careful mixing up anything like an oz or more of regular epoxy. The last thing you need in the middle of a glassing project is to look over and your epoxy is melting the container. If you need to mix a significant quantity, make sure you're using an epoxy made for that purpose.

On the subject of CA: I've tried this in the past, but found it didn't stick. I think the fiberglass sucks up all the CA (other than the stuff than immediately evaporates and goes into your lungs), and it just doesn't stick. If you're going to use CA, I highly recommend an experiment. Take a piece of fiberglass and some balsa sheeting, and try it out. In my experience, it was very easy to peel the fiberglass off the balsa. With epoxy, the wood, the glass, and the epoxy form a solid bond, and you get an incredibly strong and flexible composite sandwich.

I've never done it myself, but I've heard good things on RCU about using polyester resin (get it at Home Depot or a boat store). It's a lot cheaper than epoxy, and tough as nails.

Either way, Monokoting the joint is a hassle.

RE: Epoxy or Thin CA?
 

Another option (and you never hear of it...) Use silk and yellow glue instead of fiberglass and epoxy/resin.

I have done this on a few wings and it works GREAT. Silk is stronger than fiberglass of the same weight. (10 times the tensile strength of steel!)

On a Altech Tamecat (a specific instance where I dd it...) I applied 3 layers of 10 momme (a silk cloth weight... this is a medium silk scarf weight) silk. First layer 2 inch wide, 2nd 4 inch, 3rd 6 inch. and used yellow glue thinned 50-50 with water. The wing center joint is as strong as can be desired, and I saved weight vs one 3 inch wide strip of 2 oz fiberglass with epoxy.

I still have the wing... though it was severely damaged in a mid-air. Lost appx 6 inches off one wingtip, lost use of one aileron, safely landed the plane. (many many severe bounce landings using it as a trainer... had just about wore out the wingtips anyway) The center joint is still rock solid.

RE: Epoxy or Thin CA?
 

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RE: Epoxy or Thin CA?
 

And for teh baby butt finish: wrap the 30 minute (or longer) epoxy / fiberglass tape with a strip of saran wrap. Pull tight. Lwet cure. this should give you a super smooth finish..

Like, duh!! pull the wrinkles out, and get the saran wrap a smooth as possible!!

RE: Epoxy or Thin CA?
 

Now I am gonna go a 3rd direction. I have used with sucess god ole' yellow carpenter's glue. Worked well and no fumes no mixing and no problems getting enough working time. I just rubbed it into the weave and put some under and on top of the cloth. Carefully brushed away any excess. Worked for me.

Mark Shuman

RE: Epoxy or Thin CA?
 

BTW... the yellow glue ha NO problems with getting the covering to stick. Fiberglassed (epoxy or polyester) areas can be a real pain to get good adhesion of iron-on coverings.

RE: Epoxy or Thin CA?
 

Just use the thin ca, the tape is not that critical, as long as you got enough epoxy on the wing joiner.

RE: Epoxy or Thin CA?
 

Tell that to all the trainees that trusted wings without fiberglass taped center sections. (the ARF kit didn't SAY to put it on... so they didn't) All those pretty airplanes that decided to play LAWN DART when the wings folderd in a simple 1.5 g turn. (appx 10 deg bank angle... near 0 up elevator... and the planes had never been looped.)

Sorry... but I see a trainer without the reinforcement... I won't help fly it because I KNOW it will break.

RE: Epoxy or Thin CA?
 

Old School vs. New School.

I have used CA on many a wing center on some very high speed, high load airplanes. I have used this method on every GP Patriot I have built , a DP Edge, and both of my large CAPs.

CA is every bit as strong as Epoxy, it is MUCH lighter and far easier to lay up (seconds vs. 15 -45 minutes).

I have put these planes through things no other pilot would dream of (trying to break speed records in power dive conditions) and the wings held up flawlessly under many, many flights.

One of the patriots wings failed after 15 consecutive dives at near 150 MPH, it was not at the center section, but rather at the wingtip area.

CA works fine, and it is a LOT easier, faster and cleaner than epoxy.

DP

RE: Epoxy or Thin CA?
 

You'll note I didn't say NOT to use the CA. ;)

The problems with using the CA would come from technique, not that its a bad glue for the job. IT CAN work. You have to ensure FIRM contact of the cloth to the wood while the glue is applied, then you can get a good bond.

I think that the CA would be an expensive way to go compared to using 2 hr epoxy... but I avoid CA as much as possible so I haven't done much work with it and fibergalss cloth. The cost would be my main reason not to try it. (why use $4 to $8 an ounce glue when yuo can use $4 a quart glue and get the same final result?)

RE: Epoxy or Thin CA?
 

CA is expensive and it stinks! I love CA for what it's good for: general airframe construction. I tried CA once for FG wing center joint on a CG Eaglet. Now that 50" wing is not large at all, but the amount of CA used cost a lot more than any other glue. Plus the fumes just about brought me to tears, literally. Plus it was next to impossibly to sand CA after it cures. Plus CA doesn't have enough surface tension to "suck" the FG cloth flat to the balsa if there is any sort of curves at all. CA may bond instantly, but you can't really handle the wing till 1/2 hour later anyways.

Epoxy is no less "new school" than CA. The West Systems finishing epoxies I use have fairly sophisticated chemistries and offer several different hardeners fine-tuned to specific applications. The F3B competition sailplane pilots uses epoxy exclusively for their wing constructions. If you have the opportunity to see one of those works of art done with carbon fibre/kevlar and epoxy resin, I'm sure your opinion of epoxy will change.

CA is okay if you are using a narrow 1" wide FG tape. Anything more than that, it's a great tool for the wrong application.

RE: Epoxy or Thin CA?
 

I would never use CA for applying glass cloth. It DOES bring tears to my eyes, and it does cost a fortune. I have no control over where it goes and I think it is a sub-standard choice. Laminating resin is made to apply glass cloth - CA isn't. It's up to the individual, but personally, I think CA is a really poor choice.

RE: Epoxy or Thin CA?
 

You have me down to Epoxy or yellow, carpenters glue now. I would prefer the carpenters glue, but will that be a strong enough bond? What is the best way to apply it? Put the glue down first, then cloth, then more glue?
Thanks for all of the replies.