CA vs Titebond and other yellow or white glues

[aeajr]

My question is around which makes a stronger, more resilient joints, particularly in winch launched sailplanes using built up structures from balsa and plywood?

CA is very convenient, but it seems to be very rigid. It also seems to make the wood around it hard and brittle, most particularly the thin CA.

Is that a valid observation?

I am doing some wing repairs and have noticed that yellow glue, particularly Titebond II, seems to be very strong but remains somewhat flexible. I am thinking that this will "give" better with the wood and be less likely to break away, or make the wood brittle around the glue joint.

I am not building contest ships here. I am looking more for the ability to handle moderate winch launches and less than perfect landings.


Any opinions on this?

[Dave Robelen]

Hi.
That question is not that simple for me. I have never found a "one size fit's all" glue. For basic structure and framing I have very good results with medium CA. The penetration is just about right for balsa joints such as a rib to spar, etc. Thin CA can be pretty frustrating to use in the structure of an R/C model. As you point out, it "wicks" into the surrounding wood, making things brittle, and often bonding the builder to the structure. I use this for platic flexible hinges, and glueing firewalls in fuel models. In a plywood-balsa joint, this is the strongest of the bunch.
Titebond II or Elmers Carpenter glue is really helpful in installing sheeting where the drying time allows more opportunity to get the sheet in place and clamped. The aliphatic glues are resilient and tough, but will fail sooner in an edge joint. Make a couple of sample joints with Titebond II, and a couple with medium CA. Start breaking them and you will see a difference. The aliphatic glues are a bit "rubbery", and therefore tough to sand flush. A thin layer of thin CA over a Titebond sem will be a big help in the sanding process.
Have fun, Dave