Originally Posted by
sensei
I must agree a thin viscosity epoxy laminating resin would have been a great choice in this application.
Now I have a question for you Zor, you posted: CA has its use for tacking and is easy to take apart (weak joints) and also useful for ARF / RTF models. If CA is good for ARFs and RTF models generally manufactured from the same materials as found in our scratch built or kit built models then why would it not be a suitable adhesive for a complete scratch or kit built model of the same type of materials found in ARFs and RTFs? I only ask because I have been using thin and medium CA almost exclusively for the last 20 + years building entire wooden model airframes, and I have never experienced a model's glue joints coming apart in flight. Could you please elaborate on your statement?
Thanks in advance,
Bob
Hi Bob,
When fitting pieces to be glued and being as accurate as we can so the angles match (90 degrees or any angle) and putting the faces to be glued together there is contact at only a few places (often only one place) so some air space has to be filled by glue that has residual solids.
I experimented depositing some supposed to be the thick variety (crack filling) CA on a clean smooth metal surface where I think there is no penetration in the metal. I wanted to see what happens to the CA as it cures. How much change in volume occurs. What was left was very minimal. It appears to me that 80% to 90% of the volume is gone.
The CA being so fluid spreads out and penetrates any porous material. Whatever is left after curing may reinforce that material but does not contribute to a joint to another piece.
Manufacturers benefit by CA reducing considerably the production time (labor cost). That is good for them but not for us in terms of reducing damages in a bad landing. They are also concerned about replacement revenue. The model does not necessarily fail (break) in flight but does on a bad landing. Like I read before on a posting ... the fellow wanted to recover his ARF model and found out that the covering was the main thing holding the frame together.
A few words about clamping.
When applying the glue and clamping immediatly most of the glue is squeezed out of the surface being glued. Double gluing to create fillets does not only increase the binding area (up to five times) but also provides properly shaped binding surfaces. The clamping does not force the glue penetration; it pushes the glue out of the joint. The clamping main purpose is to prevent relative motions of the pieces while the glue cures. Relative motions might develop a gap between the surfaces being glued.
It is often advantageous to avoid clamping so the glue is not squeezed out. The pieces can be kept in position with simply pining with Tpins or any suitable pins. An example of such a case is when butting to sheets together lengthwise and it is not practical to clamp. I apply wood glue (Titebond, SigMent) for 3 or 4 inches separated by about a half inch. I put a drop of CA (tacking) in that half inch and gently press by hand the sheets against each other for a minute. If using pins then the glue can be continuous of course.
Above is my outlook on gluing and the use of CA. I hope it answers your question.
Zor