I'm thinking about building instead of ARFing it this time around for my second plane. I've been reading some build threads and all but here's my question. I've seen people using different glues for different purposes which caught me a little by surprise actually. Not that different glues don't have a different purpose but for example, why does everyone seem to use CA for wing ribs. I would have thought epoxy(being as strong a bond as it is) would be a select choice for that. In fact, I would have thought that if anything, you could use epoxy everywhere on the plane because of it's bonding strength.

If not, why and what do you use for what parts of the plane?

One of the reasons why you don't use epoxy except where it's absolutely needed for strength is because it's heavy compared to other adhesives. Many use CA for a large portion of their building. And I used to use CA's for my building but about 8 years ago I switched to Elmer's Carpenter's Glue, and I won't go back to the CA's. I feel that my building has improved since I've switched because I have more time to get a joint positioned correctly before the glue sets and you don't get those hard knots in the wood that are impossible to sand. Also I didn't like the reaction my body has to the CA fumes. Many call it a CA allergy, but after I've talked to a few doctors and a couple of chemists I find that it's not an allergy but a simple chemical reaction in your body. The CA fumes react with the moisture in your nose, throat, and lungs to produce some very bad reactions. Over time these reactions can become worse with repeated exposure. I've seen people that can hardly breath for 3 days after using it. I wanted to avoid that from happening before it got to that point. So..... here's what I use for my building.
[ul][*] Elmer's Carpenter's Glue - This is my main adhesive. I use it for the majority of building with balsa and wood to wood contact. For ply's and harder woods I will use epoxy[*] 5 minute epoxy - I do have this around but I very rarerly use it. I will usually use 30 minute, but I have the 5 minute around for quick uses that aren't in critical areas of the plane.[*] 30 minute epoxy - I use this for critical stress areas on the plane such as wing joints, firewall attachments, horizontal and vertical stabilizer, securing hinge points, and other high stress critical areas.[*] CA's - Yes, I know I said I didn't use these but that's not entirely true. I still use them for a couple of things. I keep thin CA around for hardening threads cut into wood for such things as wing bolts. I may also use it to help hold large constructions together while the Elmer's sets. I will put a couple of small drops on the wood to hold it all together while the wood glue dries. I also do reviews for RCU and I use the proper thickness CA adhesive that is called for in the instructions. I do this because we try to do review planes as the instructions call for. I do have medium and thick CA around but don't use them much. Especially the thick, too many people try to use thick CA to fill up gaps in wood joints but this can be bad, it can lead to a false sense of security because the joint will be weak. Nothing beats wood to wood contact in a joint.[*] Formula 560 - This is a canopy adhesive and that's exactly what I use it for, for attaching the canopy to the fuselage[*] Gorilla Glue - I don't use this glue too much because of the way it expands while setting up. This can be bad if you don't have the area secured properly because it can push the parts out of position before it dries. But I've found that it does have several really good uses, one especially good is if you have areas that need to be filled and secured. You can apply the glue and a little water and the glue will expand out into the area you want to fill.[*] Thread locks - Self-explanatory. I use thread lock to keep nuts and screws in place. Always use blue thread lock so you can remove the nut or screw later. Never ever use red thread lock because it's permenant, you won't get your nut or screw off ever again.[*] 3M 77 spray adhesive - This is some great stuff that has lots of uses in our hobby. One that comes to mind right off the bat is when doing cockpits. You can use this spray adhesive to hold items like printed instrument panels in place.
[/ul]

Well, that's about all I can think of right now.

Ken

Epoxy is heavy. Balsa is weak. CA is fast. Some glues sand well.

What I use:

Basic building I use wood glue. This includes wing ribs, stab, fin, most of the fuselage including the formers.
On difficult situations where I need a quick set I will use mostly thin CA but occassionally I will use medium. This includes formers, some ribs, and sheeting that needs to be set quickly (but then I go back and reglue the whole thing with wood glue).
I will not use anything but 30-minute epoxy on such areas such as firewall, landing gear blocks, attaching stab and fin to the fuselage, joining the wing halves together and fireproofing the fueltank area and firewall (thinned with denatured alcohol for the fuelproofing).
I use clear fingernail polish for sealing graphics and for help in sealing the covering in hard-to-hold areas such as trailing edges, wing saddle area, engine compartment and landing gear area.

That happens to me. I hardly ever use CA.

I wish my CA reaction only lasted 3 days.

My building is mostly with Elmers Carpenters glue, including wing ribs and spars. Its far stronger than the balsa anyway. I use 30 minute epoxy for firewalls and landing gear blocks, and pin them inplace where possible. I use gorilla glue to glue in weights inside the fuselage, particularly tail weight if necessary. I like the way a small amount can be used to essentially encase the weight in foam inside the fuselage. Also works well for wing tip weights. I also use gorilla glue for hinges and pins where the expansion is desirable. I don't waste time with 5 minute epoxy. For fiberglassing and fuel proofing, I use the 20 minute finishing epoxy. It also works very well for giving a high gloss finish to painted plastic and fiberglass parts (cowls and wheel pants).

I'll use Foam Safe CA for thread hardening and some quick repairs. So far the foam safe CA hasn't induced the CA reaction.

Brad

As others have pointed out, epoxy is heavier than other glues. It is very strong though and used for critical joints such as tail sections, landing gear blocks, joining wings and firewalls. It also works great on materials such as plywood, plastic, etc. where some glues may not do as well. For things like wing ribs, it is overkill. Yes it is strong but both CA and regular wood glue are stronger than the wood pieces being joined if done properly; they are more than adequate. It would also be a pain to constantly have to mix new epoxy. Once you make a batch, the clock is ticking. It will start to cure and harden in the cup before you know it.

I am finishing building my first kit, second plane and have used mainly CA. I do not mind the smell of it and have never gotten any reactions from it, but I feel that it has really sped up the build time of the plane. I used wood glue and epoxy for some of the stuff, but I am so excited about getting this bird into the air, I do not think I could wait for wood glue to dry if I used it on everything.

That being said, I try not to use the CA kicker very much because it allows the CA time to soak into the wood and make a really strong bond. I have been using thin CA to hold the peices in place, and then medium to really hold them together.

Thanks a lot for the info. I always wondered about the different options. Actually, carpenter's glue works for me. I think I prefer the idea of using it. How long does it take to set on average? Couple hours? Overnight?

Carpenter's glue will be set in about 20-30 minutes, but will take 24 hours to be fully cured. You can remove and handle the parts after it's set

Ken

I use TiteBond II and it says to clamp for 30 minutes but not to stress the joints for 24 hrs.
When building, I plan the build so that I can continue on another section while the one I just worked on is drying.

As was mentioned, I use 30 minute epoxy for high-stressed areas like the gear and wing mounts and the firewall/engine mount too.

I only use CA for CA hinges or when I have no other option. I ventilate my work area and wear a mask when I do. My chest hurt for a day once after using CA and I didn't know why until I read about it here on RCU.

Allfat, do yourself a favor and protect yourself now before you fall victim to it too. Please ventilate and/or wear a mask just in case. You may never experience the symptoms that others have but if you do you'll wish you had heeded my advice.

There are some important differences in glues/adhesives to be considered when using them! Surely not only safety issues, but understanding how your choice in adhesive works or bonds.


When using adhesives like carpenters glue there are shrinkages in the joint areas. This is because carpenter type glues have a carrier that must evaporate (water) in order for the glue to dry. The amount of shrinkage depends upon the percentage of solids in the product (the material left behind that forms the joint), most carpenter glues are around 50% solids, making shrinkage around half. The same also true with solvent type adhesives like contact cement, where the solvent flashes off.

What does this mean to us as modelers or woodworkers? It means that when gluing we must firmly clamp or position the materials being glued otherwise because of the shrinkage we will have a poor glue joint. In woodshop years ago many of us made laminated wood bowls turned on wood lathes. The layers of the laminated wood had to be very firmly clamped together to insure good joints, otherwise the bowl once chucked up the lathe would have a chance of failure.

Then there are epoxies which are a 100% solid adhesive. What you see is what you get! Epoxies cure by chemical reaction or cross linking. There is no solvent or water carrier that leaves the adhesive when curing. Which means that there is no shrinkage in the glue joint which allows for a low pressure bonding system. Epoxies are great gap fillers especially in the paste forms. High strength, no shrinkage, water and fuel proof, highly chemical resistant, bonds most any type of material. Probably the best adhesive for bonding dis-similar materials.

There are a great number of adhesives available to us today. All have their place and use from kid's paste glue to the more exotic types. Its realizing and knowing when, where, why, and how to properly to use each type of glue/adhesive is most important.

Food for thought!

Just to expand slightly on what RCKen said earlier about Gorilla glue.
They make a polyurethane glue which Ken was talking about which isn't that good for general building IMO but they also now have a wood glue which I understand is quite good, like TiteBond II or Elmers.

Epoxy is indeed very strong but also very heavy. Frankly, it makes little sense to have a bond stronger than the surrounding wood. I use it primarily in two areas - the engine firewall and the wing center joint. Everything else I can either use aliphatic resin (the yellow TiteBond or Elmer's glue) or CA adhesive.

One additional disadvantage of the CA glues is you can make a permanent mistake in a hurry!

I have used the gorilla glue that is new. I like it because it does not dry yellow. I can't use CA but I like to use transparent and some of the other glues turn yellow and don't look good. It also is a quick grab

Interesting notes here about CA, and the bodies reactions. Fortunately I havent used it often enough YET to suffer this.

However; and it may just be me; interestingly enough, I do have a reaction to the smell of Epoxy. It doesnt give me respiratory issues, but it makes me sick to my stomach. For a couple of hours after Ive used it I feel off...

Fortunately, there are better glues for most of our applications so I dont have to use epoxy much in my repairs.

You also have to keep in mind that, not only is epoxy extremely heavy compared to CA, but the bond is only as strong as the material. Wing ribs are generally made from especially thin balsa. By itself, it is quite weak. It'll break just as easy by itself regardless of the strength of the glue. So if epoxy offers no benefit in an area, why pay the weight penalty?

Use epoxy where it absolutely cannot come apart AND there's no other structure to help the bond. Wing joiners, tail feathers to the fuse, wing mounting plates, firewall, etc.

interlocking parts make themselves strong through the design... all you have to do is keep them together... CA! wing ribs, fuselage, built-up tail feathers, etc.

Thanks for the advice. And for the record, I do work in a ventilated area and try not to directly breath in the CA fumes. It does not really bother me, but I do take precautions because I know it has potential.

Amen on the advice. I have tried all kind of resprirators and none of them work ( some of them very expensive ones also). I only need to smell the fumes and then I can't breath for 2 days. SO I don't use it, or have my wife do the CA hinges for me while I leave the room for a hour or so. I use epoxy and the new gorilla glue with good success. I also use the pace hinge glue for my other hinges that are not CA

Gene,
there's a unique idea. Is this so you can blame her if the plane crashes!!!!

j/k or course!!!!

Ken

Ah!!!! you found my secret. I never crash that it was my fault.

Adding wood glue on top of a CA glue joint does not add much, if any, strength.
Wood glue needs to be inside the joint, and needs to soak into the wood, to create a strong bond.

Carrell,
Very good point. And it does justice to mention that this true for most adhesives. Epoxy, wood glue, and most others all need to work into the pores of the wood in order to set properly and give a good strong joint. One the pours of the wood have been filled with anything it will be next to impossible to get a good joint. All of these adhesives need to be applied to good clean wood.

Ken