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1/32 ERA-3B Skywarrior - 3D printed / scratchbuilt


Starfighter

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A quick note on the appearnace of the flaws after 2 years of no signs whatsoever:  I know of Bonsai pots - some very expensive ones at that - where without any warning, and despite being used for more than a decade (so getting soaked with water on a daily bases, bonsai roots growing in the pot, hot sun in summer etc) small parts of the pot wal flew away with an explosive noise.  It took many years of fatigue in the baked clay to finally give way to the stresses created by an impurity in the clay.  Pot damaged beyond repair in many cases.

 

I suspect something similar happened: a tiny flaw inside the material causes stress, which in turn results in a crack that gradually grows until the remainig material in the component is no longer capable of withstanding these stresses - result: cracked component.

 

From a materials standpoint it would be interesting to cut the fracture further open and examine it under a powerful microscope...

Edited by Landrotten Highlander
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14 hours ago, Starfighter said:

I think the problem on the Skywarrior is not only down to the resin and curing but also to the fact that I had to heavily tweak the parts to get them into a more correct shape, so I guess it's a combination of several factors - tension inside the parts due to the way I had to handle them, the material possibly not being 100% cured and maybe a chemical reaction of the three different types of primers I have used. What I find quite astonishing is the fact that this has happened almost two years after the model was assembled and a year after the last coat of primer was applied. I've had the model in hand several times since then and the cracks only appeared a few days before my last post. Very strange... 

Ben, I feel your pain on this one mate.

 

I have had the same thing happen on my projects too...not all were printed parts either.  I also think part of the reason is that when we use different mediums, they seem to take their time to 'settle'.  Despite CA being stated as not shrinking, my experience is that it actually does.  When I need to build up multiple layers, I make sure each layer is fully dry, then I put accelerator on it just to be safe.  So far this seems to have stopped any issues, fingers crossed.  But some parts on my 24th Mossie which were extensively reworked are showing no signs of shrinking or cracking after 3-5 years (oh dear, has it been going that long!). 

 

Strangely enough on my Phantom last week a section of the spine 'blew out' all my filling with CA on the resin section!  Why???  I have sanded it all smooth and fixed everything now and it took ages.  I know in this area I have used, CA, JB Weld, and Mr Surfacer.  Maybe they all just needed time to settle and leech out all their chemicals to stabilize (at different rates).  In the past I have usually found addressing the situation once is enough to fix it permanently.   

 

Time and maybe trying to use one sort of primer is what I have found best.  I had lots of issues with a coupe of automotive primers in the past, they seem 'hot' and shrink a lot....well mine did anyway.  Dont use hi-build primers either, they seemed to make things worse for me. Which will be interesting for when it comes to finding something for this 32nd Orion

 

Sorry to ramble, but this is a subject that has always interested me and nothing scientific, just my experience. Dosent happen on all of my models either.   I am 99% sure after fixing it you will be fine.

 

Keep up the great work, she's an impressive beast!

 

Cheers Anthony

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You are our vanguard in this respect Ben, so where you lead today, others will follow tomorrow and learn from the lessons that you teach us all - great work and perseverance my friend, you certainly deserve accolades for your efforts - please stick with it.

 

Cheers

 

Derek

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11 hours ago, Anthony in NZ said:

Despite CA being stated as not shrinking, my experience is that it actually does.

 

Hi Anthony,

 

That is the reason I add talcum powder to my CA mix as a filler - it prevents shrinkage (and is so much easier to sand, dependent on how much you want to add).

 

Derek

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14 hours ago, Derek B said:

 

Hi Anthony,

 

That is the reason I add talcum powder to my CA mix as a filler - it prevents shrinkage (and is so much easier to sand, dependent on how much you want to add).

 

Derek

Adding talcum powder to CA is a VERY BAD idea. It may not show up right away but, down the line it will become very apparent, trust me, and the only way to get rid of the issue is to remove that area and start over.

Steve

Edited by A-10LOADER
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8 hours ago, A-10LOADER said:

Adding talcum powder to CA is a VERY BAD idea. It may not show up right away but, down the line it will become very apparent, trust me, and the only way to get rid of the issue is to remove that area and start over.

Steve

 

Sorry to hear that Steve - I have used this method as a filler for many applications for over 45 years now on many models and full kit master patterns for mould tooling without any issues or problems. What happens to it over time from your experience?

 

Derek

 

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10 hours ago, Derek B said:

 

Sorry to hear that Steve - I have used this method as a filler for many applications for over 45 years now on many models and full kit master patterns for mould tooling without any issues or problems. What happens to it over time from your experience?

 

Derek

 

Funny "spots" begin to develop that have a white powdery residue. Kind of like when concrete absorbs too much water, you get those white powdery spots on them.

Steve

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13 hours ago, A-10LOADER said:

Funny "spots" begin to develop that have a white powdery residue. Kind of like when concrete absorbs too much water, you get those white powdery spots on them.

Steve

 

Ah, yes. This can sometimes happen if the talcum powder is not quite thoroughly mixed with the CA properly (the use of old CA and slightly moist talcum powder may also exacerbate this problem).

Derek

Edited by Derek B
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