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Gah!! Phantom seam...


ZachP319

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Ok so I have a particularly tough seam issue right now. It showed itself during my primer coat so I used superglue then sanded and polished and resorayer primer. It showed up again as I wood grained the fuselage - repeated steps above and then used putty as well. Finished wood graining. It looks great. Now the seam is back.

 

This is the Roden Albatros D III and I think the issue is that the seam is flexing somehow since the gluing surfaces are slight and the plastic soft. I coming to hate this kit but I like the subject.....

 

Any thoughts on how to deal with this? I don't want to knock down my nicely wood grained top fuselage decking until I think I have succesful plan..,,,

 

Zach

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Hmmm.

What i can tell you from experience is if you use styrene glue like tami's extra thin and you putty over it. Wait for the putty to dry and sand it, you might get a phantom seam after a day or two. From my understanding it is because the styrene glue is still 'drying'. What i do as of late is where I know there will be a seam i use extra runny CA to bond for example fuselage halves and then use CA and microbaloons to fill the seam and sand away. This way there is no waiting. Now in your case I'd probably try the CA again in a couple of days to let the glue cure and resand and repair the area and then the seam should not reappear. Hope that is of help

Karim

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Zach,

  From previous experience I can attest to the fact that Karim is correct. Too much Extra thin or any plastic glue causes excess plastic to melt more then necessary, and can take a very long time to really cure. Weeks or even months. So use as little as possible. You can always go back with a 2nd coat if needed.

 

Joel

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I may be wrong, but from what you've said, the joint is not stable and needs reinforcing to stop it moving..

 

With similar issues, I'd suggest gluing a backing plate behind the joint to stabilise it.

Once the joint is stable, a cyano surface fill/sand will result in a blemish free surface.

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A backing plate would do the trick but I am quite far along in assembly and painting this measure is likely a build killing step.

 

 

This is likely an issue with solvent as well since the seemmopeneded at one point and was re-glued...

 

Zach

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The solvent isn't the problem, so much as what it's been tasked to do. The issue traces back to the kit's design.

 

I had a similar problem with a Matchbox Victor, after I used Revell Contacta cement to secure the area aft of its then re-profiled canopy.

Despite being at the painting stage and worse, the canopy masking having been done, the central fuselage seam kept re-appearing and closer

examination revealed the area around it was also squishy. Now in my case I was able to drill ventilation holes in the upper surface to allow the solvent to dissipate which it did after about a week, leaving a very firm outer surface, and for confirmation I cemented a backing plate via the opened bomb bay. It then smoothed over as you'd expect. The moral being, if the kit designed bonding area is inadequate for the task required, the shortfall needs to be corrected by the builder.

 

Another solution might be to pour some liquid epoxy (I bought a two bottle pack from an RC model store some 10 years ago, and still have over half left. And it still works). Drill a hole to introduce it in such a way as to ensure that dripping or injecting it puddles it on your problem joint and it will hold the joint absolutely securely once cured, and the polystyrene solvents have completely evaporated..

Edited by Chek
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Good notes and thanks for everyone's comments.  I tend to use different glues and cements, incl Tamiya extra thin (which I love), and the full ranges of CA, as well as trusty old model master cement.  I'm not always thinking about how long it takes these to cure.

 

Thanks for the reminders!

 

Chris

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Stretched sprue, very thinly, soak it in CA glue for a sec and stuff it good into the seamline. If you do it, be very careful not to spread the glue over a much larger area. Wait it to dry well for maybe a week. Then sand it easily like a normal plastic piece.

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