zerosystem Posted September 22, 2015 Share Posted September 22, 2015 (edited) I tried something different working on a C-2 Greyhound, using the biodegradeable paper BBs. You only need a small smear of CA and they will roll and stick into all the areas underneath pits and inbetween wheel wells and fuselage sides. Edited September 22, 2015 by zerosystem Link to comment Share on other sites More sharing options...
chuck540z3 Posted September 22, 2015 Author Share Posted September 22, 2015 Well boys, it's time to go to the lab and do a few experiments! Although it doesn't matter any more, I NEED to know if the GOOP adhesive just ate the plastic or it was the lack of ventilation that caused the problem. To test this, I just smeared a thick gob onto some Trumpeter plastic to see what happens in a few days. Stay tuned!The next thing I tested was to see if Tamiya Light Curing Putty (TLCP) might be my magic bullet, because I've always known it was a bit soft and might take a scriber or rivet tool without cracking.Here's the scrap plastic with a depression ground into it. Note the pin mark to the right.I then put a nice gob of TLCP on it as well.After sanding, it filled the depressions fairly well and took the scriber and rivet tool without chipping. Here it is with a dark wash to reveal any flaws. There is some leakage at the top where the needle hole made the putty pop away from the plastic, probably because it was so thin, while the bottom looks pretty good.Does anybody have some first hand experience using TLCP? It seems to work, but I'm worried about adhesion and noticeable margins to the putty. Link to comment Share on other sites More sharing options...
Mustang JBB Posted September 22, 2015 Share Posted September 22, 2015 Chuck, Bummer. Here is my suggestion. Drill out those holes and depressions with appropriately sized drill bits. Bits that are as large as the depressions. Allow the gun bay to ventilate for a week or so to prevent more from showing up, or even just getting worse. Get you some thick styrene sheet, or layers of sheets, or even solid styrene rod, and make wedges or cones that will fill the holes you drilled. Just make them thick enough to go deeper than the thickness of the original plastic, and slightly proud of the surface. Use liquid cement to fix the wedges in place and get a good weld. Let that dry for several days then sand to shape matching you contours. Now you have a completely plastic surface that should be easy to recribe. Touch up carefully with CA once your scribing is done. As a side note, I always use good old five minute epoxy for internal glueing of weights and spars. You do have to carefully prep and sand mating surface to give the epoxy something to bite, but there are no fumes or volitals, and epoxy does have a little flex. It can also be cleaned up with alcohol before it cures. Link to comment Share on other sites More sharing options...
Mustang JBB Posted September 22, 2015 Share Posted September 22, 2015 More notes... After drilling out the holes, use files to square them off. Some of those dressions are in trickiy spots so a small hole may be needed as as a starter, then enlarging with files to match the odd shape of the depression. I am not a fan of filling large gaps with any kind of putty. The only exception being Milliput if not much scribbing is to be done. When you have to replace detail, i always try to find a way to fill with plastic, like you did with the wing to boom gaps. Plastic does not shrink or crack, and sanding is easier. You don't have to worry about one material being harder to sand than the other like CA etc. Go easy with your liquid cement and you will not have anymore sinks and depressions. Milliput is great for attaching weights. Rough up the inside of the fuselage and your weights with coarse sand paper. Knead some milliput together, then coat your weights with the milliput. Press them into place and you are done. As long as the milliput has texture to grab, those weights will never break loose. And again, no fumes or volitals to deal with. Hapy modeling buddy. Link to comment Share on other sites More sharing options...
chuck540z3 Posted September 22, 2015 Author Share Posted September 22, 2015 More notes... After drilling out the holes, use files to square them off. Some of those dressions are in trickiy spots so a small hole may be needed as as a starter, then enlarging with files to match the odd shape of the depression. I am not a fan of filling large gaps with any kind of putty. The only exception being Milliput if not much scribbing is to be done. When you have to replace detail, i always try to find a way to fill with plastic, like you did with the wing to boom gaps. Plastic does not shrink or crack, and sanding is easier. You don't have to worry about one material being harder to sand than the other like CA etc. Go easy with your liquid cement and you will not have anymore sinks and depressions. Milliput is great for attaching weights. Rough up the inside of the fuselage and your weights with coarse sand paper. Knead some milliput together, then coat your weights with the milliput. Press them into place and you are done. As long as the milliput has texture to grab, those weights will never break loose. And again, no fumes or volitals to deal with. Hapy modeling buddy. Thank you sir. I like the drilled hole idea to let the gun cavity vent, no matter what I eventually use to fill the depressions. I just drilled 9 holes and as you'd expect, the plastic is very soft. I will likely have a bit more caving before this ordeal is over, so I won't even try to fill anything for about 2 weeks. When the plastic gets hard again, I think I'll be good to go. Meanwhile, I have other things to occupy my time with this build, so progress shouldn't be too impaired in the long run. Vandy 1 VX 4 1 Link to comment Share on other sites More sharing options...
Hubert Boillot Posted September 22, 2015 Share Posted September 22, 2015 Bummer, Chuck ... as the saying goes s... happens. It may also be that a large quantity of glue generates heat in setting (we often overlook the thermal reaction when these glues settle). We do not notice it in "open air" but in a closed environment, it shows ... As for suggestions, I have nothing more to add to all the advice above. Milliput, as other epoxy putties - or more so, I should say - is great, but will not take scribing well. Making a hole and filling it with card seems a great solution. Finally, I thought the depressions on the lower part of the fuselage looked like very convincing oil canning ... Hubert Link to comment Share on other sites More sharing options...
dodgem37 Posted September 22, 2015 Share Posted September 22, 2015 Toulene and plastic don't mix. Sincerely, Mark Link to comment Share on other sites More sharing options...
Mustang JBB Posted September 22, 2015 Share Posted September 22, 2015 Depending on how big the holes are that you drilled, i would try to find a way to encourage the ventilation. Maybe a small fan blowing across the model? I was thinking last night that even with holes, the air inside will be stagnant without some kind of push. Maybe even once a day blow out the air with your mouth. Just a thought. Link to comment Share on other sites More sharing options...
chuck540z3 Posted September 22, 2015 Author Share Posted September 22, 2015 Depending on how big the holes are that you drilled, i would try to find a way to encourage the ventilation. Maybe a small fan blowing across the model? I was thinking last night that even with holes, the air inside will be stagnant without some kind of push. Maybe even once a day blow out the air with your mouth. Just a thought. Thanks. A very minor update. Based upon your advice, I drilled holes in all the depressions last night (11 in all) to let the GOOP degas, if that is indeed what has caused this problem. When drilling the holes I was shocked at how soft the plastic was. It was sort of like drilling through hard cheese, it was that soft. Left overnight, the plastic is already getting quite hard, so I am now certain the solvents in the GOOP were trapped in the gun cavity, causing the melting of the plastic. Further, that piece of plastic above covered in GOOP is still rock hard and nothing is melting. It has only been overnight, but I'm now leaning towards thinking it will never deform as long as the GOOP is exposed to air circulation. This is why it worked on the wings with no problem, I think, but we'll see in a few days if this theory is correct. I know, I know, there's a bunch of you out there thinking, "why in hell did he use GOOP in the first place"?, because I would think the same thing. Well, I tested in on plastic before I used it on the wings and I had no problem with it whatsoever, which I suspect will happen again to the test piece. I think this experience is similar to spraying lacquer paint on a model. Left to air dry, it works great and the little bit of bite it creates in the plastic is a positive thing. If you stuck the model in a plastic bag right after painting, I think you'd have a melted mess in an hour. BTW, if my theory is correct, I will still use GOOP again. It is super strong, sticks to the plastic like crazy and is flexible. I don't know of anything else that would be better for adhering the chopsticks to the wings, although a flexible epoxy might be just as good. Cheers, Chuck ghatherly and Out2gtcha 2 Link to comment Share on other sites More sharing options...
alaninaustria Posted September 23, 2015 Share Posted September 23, 2015 Am very sad to see this happened to your build bro... you were making such great progress! Anyhow, I have faith that you will get it sorted! Cheers Alan Link to comment Share on other sites More sharing options...
LSP_Ron Posted September 23, 2015 Share Posted September 23, 2015 5 min Epoxy Link to comment Share on other sites More sharing options...
Out2gtcha Posted September 23, 2015 Share Posted September 23, 2015 (edited) Indeed VERY sad news to have this happen to such a great build! While it IS ever so slightly flexible (maybe "flexible" is not the right term for JB, but more maybe "not so brittle"), not near so as say GOOP, but more so than normal epoxy, I have had THE best luck with JB Weld for attaching wing spars and what-not. I have found it to be utterly bombproof when dry. Edited September 23, 2015 by Out2gtcha dmthamade 1 Link to comment Share on other sites More sharing options...
chuck540z3 Posted September 23, 2015 Author Share Posted September 23, 2015 Thanks for all the tips guys! Right now I've decided to go with Tamiya Light Curing Putty to fill the moon craters, as per my Post # 490 above. It's hard in only minutes, it scribes and rivets fairly well and it doesn't add more solvents to the plastic, like ordinary putty would. I'll let the plastic dry out some more for about a week, then I'll give it a try. Also, my little experiment with more GOOP on a test piece of plastic has confirmed that it doesn't attack the plastic if it is exposed to good air circulation. I don't need any more tips on what to use to secure the weights, because that's already behind me. I just wish I had used silicone instead! Out2gtcha and Mustang JBB 2 Link to comment Share on other sites More sharing options...
Out2gtcha Posted September 23, 2015 Share Posted September 23, 2015 (edited) I like to use silicone for weight attachment as well when using shot. Edited September 23, 2015 by Out2gtcha Link to comment Share on other sites More sharing options...
t.valdez Posted September 24, 2015 Share Posted September 24, 2015 PVA has no deleterious effect on plastic, holds firm, cleans with water. You could have packed enough lead (Pb) dove shot in the engine halves to provide sufficient counter weight for the P-38 as I did, provided you can find it. It was made illegal here in Texas and only steel shot is available. I bought a 5 lb. sack that I hope last me a lifetime. I know, water under the bridges that we burn before we come to them before we saddle our horses that we didn't lock in the barn before they got to the fork in the road. Link to comment Share on other sites More sharing options...
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