Cyano Blues

[Andrew Tinsley]

Hello Everyone,

  I purchased a 1/4 scale Tiger Moth kit a few years ago (R/C, SHAME!). The original purchaser had made a start on the fuselage and it all looked good. Yesterday I got the fuselage down from storage with a view to finishing it off. While getting it on to workbench, I heard a few clicks! Puzzled, I started looking at the fuselage, it was made up of longitudinal stringers, with diagonal bracing in between. As I looked, one of the diagonals fell out!!
  Closer examination showed that many of the diagonal butt joints had failed. I knew that cyano can produce very brittle joints, but this was ridiculous! I much prefer using super aliphatic glue, the stuff I use is sandable and gives very secure butt joints.
  Question.........If cyano goes brittle after a few years, why on earth is it the adhesive of choice amongst many modellers? Or is it just cheap cyano that was used on this model? Would I be safe in re gluing the joints with super aliphatic or would I be wiser to cut new timber and do the whole lot again? I am suspicious of mixing adhesives, presumably the cyano would have sealed the balsa and not let the aliphatic get into the surface layers of the wood.

Thanks in advance,

Andrew Tinsley.
 

[Randy Powell]

Andrew,

The only concern I have is that in a butt joint using CA, it creates a stress riser. So if sufficient tension is brought to bear, the joint doesn't fail, but the wood around the joint tends to separate. So you end up with a chunk of wood with a little CA knob on the end. I've had this happen and am much more careful about how I structure such joints now.

[Ward Van Duzer]

Andrew,

Look for my post on "WHICH ADHESIVE (GLUE) TO USE AND WHERE OR NOT" Reply # 6

Is there some easier way to direct someone to a previously posted subject?


Ward

[Andrew Tinsley]

Thanks Randy and Ward,

  Yes Randy, that is exactly what has happened! Ward, I found your thesis on adhesives (an excellent one that I recommend to anyone!). The noise you describe when twisting a C/A assembled wing, sounds familiar!
  I would never use C/A in the application that the previous owner of the kit, has done! Question now is do I scrap the dodgy fuselage and start again, or is there any way that I can reglue the failed joints?

Thanks again guys,

Andrew.

[phil c]

re-glue all the joints with epoxy.  The CyA has probably filled the grain and wood-friendly glues like Elmer's may take weeks to dry with no place for the moisture to go.

[Bill Adair]

Andrew,

Yes, CA is very brittle. I never use it to attach flying surfaces, unless triangle stock is used to beef up all the joints.

I much prefer Epoxy for attaching stabs, fins, and wings.

Bill

 

[Howard Rush]

Cyano blues is redundant, isn't it?

[Andrew Tinsley]

Hi Howard!
               Your comment above had me laughing! I was a physicist by profession and latterly specialised in optical thin films. A lot of them were colour filters and yes grammatically speaking cyano blues is definitely an example of redundancy!

Regards, chuckle!

Andrew.