dave_anderson

My Feedback: (47)

I have built several 40-60 size kits and have always used the standard CA. I am about to start a 1/4 scale Cap 232 and I'm looking for advice on glue. Is CA up to the stress of bigger models (160FX powered). What about carpenter's wood glue or white glue? Anyone who has experience with 1/4 scale kit building, please pass some advice. Thanks!
Dave

3D_CAP232

Hi,
I did some strength tests at university a couple of years back between cyno, 30 min epoxy and white glue.
We glued samples of balsa together and measured how much force it took to break them apart.
We found that white glue was the best followed by cyno then epoxy last!!...and how many of you hold the firewall in with epoxy?
What was happening (not all epoxies will be the same, depending on viscosities) is that epoxy only rests on the surface and can't 'wick' into the wood BUT white wood glue does as does cyno as is evident with the way they broke.

Thats the theory, in practise everyone i know builds the majority with white wood glue. My cap (30%) went together with Cyno (except firewall which is white wood glue with fiberglass matt round the outside glued on with white wood glue) and is imensly strong..i think this is down to the design more than the glue though as you build it fully then add glue in the joints!

I've heard one report that white wood glue is affected by the heat...in England we don't get much of that so i couldn't comment.

Have fun

Giant Scale

I use a several different types of adhesives when I build my big planes. Elmers probond carpenters and poly urethane glue, west system epoxy, thick and medium CA. For sheeting balsa to foam I like probond poly urethane or epoxy. For gluing LE or TE balsa to foam I like carpenters glue. Plywood to plywood or balsa to plywood I like epoxy or carpenters glue. Plywood to foam I like poly urethane or epoxy.For fiberglass or carbon fiber I like to use epoxy. For bonding small parts I like thick or medium CA. I try to avoid CA if I can since I don't like the fumes. Alot has to do with personal preference. If I could use only one glue I'd go with the probond polyurethane. This is probably the most versatile of all the glues since it will bond virtually everything.

F4u5

My Feedback: (81)

I question the results of the Epoxy test. What brand was used? I use T-88 Epoxy which is an epoxy used in the full scale homebuilt world. It takes 12 hours to cure and really soaks into the wood. The tech sheet states that it has a lap joint tensile strength of 2800 psi with substrate failure. This means the wood broke and not the glue joint itself. Now granted, not everyone uses T-88 (but I recommend it strongly). . But, 30 minute epoxy would have to stand up stronger than CA on most wood types. It may, however, vary on wood types. I know you dont want to use thin CA on lite or aircraft ply unless you really soak it with glue. The this will soak in to ply likke a sponge. Medium CA is minimum required here. I would agree that a good wood glue (Elmers Pro-Bond carpenter glue for exterior use) is probably the best overall in general use (I use it for attaching wing panels with spar joiners). If you want an indestructible epoxy, pick up some T-88 from Aircraft Spruce and Specialty via mail order. Just my experience.

raistlin12

My Feedback: (1)

There was a formal study done at a university, the results of which were posted on "another" rc board. If the adhesives are used according the manufacturers directions (heat, humidity, clamping, etc.) it was found that when using epoxy, white glue, alipahtic glue, or CA, the wood broke before the adhesive failed, in ALL cases. Consequently, it becomes a matter of "taste" and ease of use. Personally, I wouldn't rely on "Elmer" to fuelproof my firewall joint, hence I use alipahtic wood glue to hold it in place, and epoxy around all the mating surfaces to fuelproof the glue joint. Then use an epoxy-based paint, or butyrate dope, to fuelproof the firwall, itself.

Jim Messer

My Feedback: (2)

I build all giant scale airplanes - gasoline powered. I like Elmers outside carpenters yellow glue, and that is used for 99% of my joints. I use some med. CA for quick placing of parts, but always back it up with Elmers.

dave_anderson

My Feedback: (47)

So, does it help to use CA to join the parts, then put a bead of white or carpenter's glue around the outside of the joint? Does a bead of glue make it that much stronger?

Thanks a million for all the help. I just started using RC Universe and I am amazed how much advice is out there!

Jim Messer

My Feedback: (2)

I don't know if it helps a lot, but it certainly doesn't hurt. I fillet weld with glue - all around every joint. I design my structures to be strong - yet light.

3D_CAP232

Hi,
The type of epoxy i used was Devcon, the specimens were clamped up...what i found is it broke where the glue met the wood where all the other specimens broke the wood. The only difference was the amount of force to break the joint where we found epoxy to be dissapointing.
I'm only offering these as what we found and are not 100% conclusive as we didnt get a chance to try out other glues or different techniques in applying the glues.

However it is known that plywood will have some light oil on the exterior when you get it and the resin in the plywood (i.e. woods natural resin) will make it difficult to absorb epoxy. I've seen this mentioned in a couple of kits.

Do you have this link to these tests as i'm genuinley intrested...always willing to learn (thats why RCU exists isnt it?).

Thanks and happy flying

EJB

I have tried just about evrything out there.I have had more than one firewall come loose using different brands of epoxy.IMO,Probond works the best for the firewall-landing gear area.I use CA every where else...it's the strongest & lightest.One drop of CA will do what it takes a big glob of white or yellow glue....& I've had that stuff fail too.

JWilliams

My Feedback: (6)

Dave (mcp130) may I suggest Cyberbond. They have a glue out called flex that is a rubber ca and it is amazing. Sean McMurtry's 2002 TOC plane was glue together with that glue and if it can withstand that blender he did on Thursdays freestyle it will hold your 160 size plane. Jeff W.

EJB

Yes, Cyberbond is good stuff....pro builders use it.Mike McConville's plane was also built with it.
BTW,I forgot to mention that I DO use white glue for foam to balsa.

JWilliams

My Feedback: (6)

EJB, you are correct that one of the planes Mike flew was built entirely with Cyberbond. I supply Cyberbond to the guy that built that plane as well as McMurtry's builder. Jeff W. ([email protected] for more info.)
For foam to balsa there are many things a person could use, however some are better than others. I recommend Cyberfoam (a polyurethane glue) or the cyberbond finish resin which is what McConnville and McMurtry's airplane wing/surfaces were glued with. Both of these adhesives are excellent for foam to balsa and have been proven. Thanks.

Newflee

I use CA exclusively with exception of laminations on big birds. Any joint that has been glued is there for good as far as my testing and experience. That being said I must say that I only scratch build and make sure that all joints are perfect and snug in all three dimensions. I can't speak for kit fit, and I imagine quality varies.
Any glue merely becomes a bridge between the parts being joined. If the bridge is too large, you are depending on it rather than the wood. In that case you might as well get into composite construction.
On the subject of epoxy. Price and quality do go hand in hand. I use West system epoxies and find them without fault. Any exopy available in less than a quart or with working times of less than 2 hours are convenient but substandard unless your making Christmas decorations.

Joe C

My Feedback: (23)

Aero poxy from BVM Jets

JohnW

My Feedback: (6)

My understanding on why epoxy is used for items such as fire walls was that it was not a brittle as other glues, such a CA. Under prolonged exposure to vibration (i.e., engine) it was less likely to fail. Anyone know if there is any truth to that?

Newflee

Hey monkey, that's true .
Use epoxy on extreme lams.
Bye the way , have you ever met a person that lost it over a loose joint.
Come to think of it , wheres mine?

ps. You guys wouldn't beleive how long this took me to type.

flytime56

As monkey said, which is true, epoxy is not a hard substance, and you can tell that when trying to sand the stuff. it's like a rubber, that is excellent with vibration, if using a gas engine, a good long curing epoxy should be used. 5 min. epoxy is only good for fuelproffing and nothing more, the longer setting time the better, for large aircraft, we use some epoxy that sets in 24 hours for laminating composits to metal, great stuff.

wood glues are used on the real planes, and the glue joint is stronger then the wood itself. the most important part, the joint has to be very tight so that the pores in the wood are mating with one another, all the glue does it set itself into the pores and harden. if your mating surface is not tight, then it will fail. putting glue beside a glue joint will do nothing but add dead weight. i have made ribs on reald wood planes, and you can stand in the middle of it and it will not break, these are how strong the glue joints are.

one thing that you should avoid as much as possible is not to sand the two parts being put together, but to cut them. the saw dust goes into the pores and will reduce the total strength of the joint. in real wood planes, if they see you doing that, they sure let you know, then you have to redo it again.

i myself love to use ca on planes since the glue is lighter then wood glue.

it all depends on prefrences and how much patience you have to wait for the glue to harden.

happy building,

Geoff