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General control line discussion => Open Forum => Topic started by: Andrew Tinsley on August 25, 2009, 01:35:23 PM

Title: Cyano Blues
Post by: Andrew Tinsley on August 25, 2009, 01:35:23 PM

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.
 

Title: Re: Cyano Blues
Post by: Randy Powell on August 25, 2009, 01:50:43 PM

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.

Title: Re: Cyano Blues
Post by: Ward Van Duzer on August 25, 2009, 01:52:07 PM

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

Title: Re: Cyano Blues
Post by: Andrew Tinsley on August 25, 2009, 02:29:02 PM

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.

Title: Re: Cyano Blues
Post by: phil c on August 25, 2009, 04:25:40 PM

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.

Title: Re: Cyano Blues
Post by: Bill Adair on August 31, 2009, 02:52:53 PM

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

 

Title: Re: Cyano Blues
Post by: Howard Rush on August 31, 2009, 09:13:36 PM

Cyano blues is redundant, isn't it?

Title: Re: Cyano Blues
Post by: Andrew Tinsley on September 02, 2009, 12:41:05 PM

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.