Simple question about CA glue...

How about the long term strength after several years of going thru the 4 seasons(if you have them). I bought a partially built large kit and some of the joints gave away while handling it. I couldnt see any dried glue on the joints but it was glued. I would estimate at least

10 years old.

The Natural Philos>

The one difference I see with the CA type glues, (aside from the health issues) is the thin verity seems to give a brittle glue joint when used in small butt type joints. Such as thin ribs and sheeting or formers and fuse sides. There is almost no glue at the joint. IMO, thin CA soaks in to much and the joint becomes susceptible to vibration and torsional failures. I build with SIG Bond (wood glue) and use CA at times, usually to tack down a section. The trouble with thin CA is most builders are not critical about their building and the joints they are about to glue, they just simply hit it with glue. With "fussy" ends to the wood or joints that are not a nice 90* butt joint, but sanded at an angle, many times it`s not the glue used, it`s the joint. The wood needs to also touch completly throughout the joint, not just a "section" of it. Preparation guys, preparation. Another factor is the density of the wood at the joint and the type of wood. I have never had much luck with thin CA and a plywood firewall, have you? Do a little home experiment, take different types of wood (and density`s) and glue up a few different joints with glues you have in your shop. Also do some sloppy workmanship and see what seems to break easier. Load on the glue and see if it makes a difference or not. I would be willing to bet the trouble experienced lies in wood types and workmanship more then the glue used itself. rick markel

My Model Aircraft Home Page

My oldest still active model is a Wild Thing 40, built 100% with CA in early

1992 -- It's survived two mid-airs, numerous 'arrivals' (verses landings), and is still going strong -- and I might add with the original engine; an Enya .46 4-c. Oh yes, it also was the first kit with CA-type hinges -- still intact as well. Some covering got brittle and was replaced, but no structural defects discovered.

What type of glue are you referring to? I have several old models around that are just as strong as new. All built with CA.

My point exactly. If you can't make a good joint, you can't expect any glue to work properly. Ine thing about CA, if it fills the gap it is stronger than just about anything else. Wood glues (the yellow variety) are very brittle and get worse with age if the joint isn't tight as well.

jim breeyear wrote in news:cpk62a$67i0$ snipped-for-privacy@swen.emba.uvm.edu:

Unfortunately, the mortality rate of my airplanes is not high enough for me to have a lot of 10+ year survivors. Still, I have a few pieces from back then, including a wing that dates back to Feb '88 and is still going strong. It was built exclusively with CA. The covering is getting kind of shaggy . . . (Black Baron film). And I think I still have 1 or 2 planes from 1991, including a glider wing that a flew a few weeks ago.

We don't actually have seasons where I live, though - don't have any data on whether extreme cold/dry cycles would make things worse.

Now, I've had problems with doped tissue - after about 10 years, it seems to get very, very brittle. And I got to handle half of a 50-year-old old- timer, and the wood itself had dried out so badly that it was completely useless.

snipped-for-privacy@aol.com (Aileron37) wrote in news: snipped-for-privacy@mb-m23.aol.com:

Yeah. I use med/thick CA for most things anymore. Thin for hinges, of course, or for repairing cracks or hardening TEs, but that's about it.

Also, I find that I use less glue with the medium because I have so much better control of where it's going - the thin stuff seems to wick away so quickly that most of it doesn't go where I want it.

I build with SIG Bond (wood glue)

Scary thought! If you kept pouring glue into the joint, I guess . . . maybe . . . yech

Agree. Good workmanship with mediocre glue will beat mediocre workmanship with good glue any day.

aileron37 wrote > I have never had much luck with thin CA and a plywood firewall, have

Mark Miller wrote >Scary thought! If you kept pouring glue into the joint, I guess . . .

Just for the record, I have never used CA for a firewall. My point was, I have seen more then a few try it, even on larger aircraft. Makes you think. rick markel

My Model Aircraft Home Page

That does not make me think. it makes me cringe.

I have raced several warbirds with YS 91 engines (running 50% nitro) with the firewalls, and everything else, glued with CA. Like I said previously, if the joint is properly made, just about any glue will work. ALL of them are stronger than the wood.

-- Paul McIntosh

"Six_O'Clock_High"

Cringe away. I've used CA on a giant Stinger, two 1/4 scale Dr.1's, and everything else I've ever flown. Never had a structural failure.

What's REALLY scary is the guys using 5 minute epoxy on firewalls. Dr.1 Driver "There's a Hun in the sun!"

And you've likely used some extra bracing like tri-stock or the firewall was interlocked with the fuse. Which I believe is proper with any type of adhesive. I wouldn't trust a firewall with only a simple butt joint with any type of glue. The joint design is very important.

John VB

You are quite correct. Either the plans called for tri stock or I added it. I will also use 1/8" dowel through the fuselage sides into the firewall edge. Sometimes I will make a rabbet joint between the fuselage sides and firewall.

ANY glued joint must also be mechanically sound. Trusting the glue alone to hold a joint is asking for a failure. Look at how quality furniture and musical instruments are put together.

However, in the case of CA, the wicking properties help make a sound mechanical joint as the glue is pulled into the grain. Dr.1 Driver "There's a Hun in the sun!"

"There's a Hun in the sun!"

Can you elaborate a bit on that - I thought epoxy was OK for obtaining high strength bonds

David

Dr1Driver wrote:

There's one thing bothering me about this praise of CA adhesives.

I remember someone trying to promote a "de-activator" to de-bond accidental CA joints e.g. fingers stuck together.

The sales rep bonded a friend's finger and thumb together - they were quite well stuck. Before the deactivator could be applied my friend simply gave a quick shock to the joint by knocking a ball point pen between his finger and thumb and the two sprang apart - much to the surprise of the "expert".

After that demonstration I have only used CA for quick, temporary field repairs so as to be able to keep flying, and only then for lightly stressed parts.

Malcolm

The epoxy needs to penetrate the wood to do any good. Otherwise the only 'strength' is that of the epoxy itself.

Gluing your fingers together is a hit or miss proposition. I have had times where the CA would not bond my skin and other times I had to soak in debonder for minutes (not good gor you!). Also, most CAs will peel off your skin in an hour or two as the natura oils cause it to lose bond.