flion
Well Known Member
That picture brings up a question. I cannot think why one would drill and countersink holes with the blue plastic still attached to the piece. That plastic came off as soon as possible for me. Once you find your first sign of corrosion underneath some of that plastic you will understand why.
I didn't want to hijack the thread about countersinking that this came from. I've seen this topic come up from time to time and I wanted to comment. 23 years building on two projects and I've never seen corrosion under the plastic. Not to say it doesn't happen but... the plastic is over aluminum cladding, so why would it corrode? Something like dissimilar metals or a reaction to the adhesive? I'm guessing what people are seeing as surface corrosion is actually the adhesive getting old but, again, I could be wrong.
However, to answer why you'd want to drill and countersink with the plastic on (or dimple, etc.) is to preserve the cladding. The plastic helps prevent the ribs from scoring inside the leading edges of the skins, for instance, during assembly. If you are going to prime, no big deal, but even then I didn't see any reason to risk gouging the cladding if I can avoid it.
I worried that maybe the thickness of the plastic would cause a fit problem but the only place I have found that to be true were the spacers for my fuselage spar parts on the RV-10; it took that many layers of plastic to make a difference. But since the finish on the spacers didn't matter, I stripped them no problem. For the rest of the aircraft, one or two layers of plastic has not affected the fit at the final step when it was removed.
The other problem people have had is removing the stuff after it gets old. I've not had any problem with the blue or clear plastic (haven't seen clear since the RV-6A wings, around 1997). My -10 kit arrived in 2009 and I'm still having no problem; all it takes is some heat and the parts are dust and scratch free after having been protected by the plastic. I've seen the white plastic on someone else's project and it truly was a PITA; not sure what I'd advise there.
I mentioned dimpling with the plastic and I've had two issues there, both easily solved. First is that some parts with gather chips under the plastic from drilling and you definitely don't want to dimple over those chips. When this happens, the chips are between the surfaces so the underlying rib gets the plastic stripped before using a squeezer to dimple; I can easily keep the dies from scratching the cladding here. For the skin, I strip the inner surface to remove the chips but leave the outer plastic on to keep the male die from scratching as I move the skin in the C-frame tool. Removing the inner plastic also prevents the dies from cutting the plastic and leaving little dimple-sized circles of plastic on the skin when the plastic is removed. I've never seen this cutting happen on the male die side.
I'm not advocating leaving the plastic on, though it's what I do. I suspect this is like the primer wars; everyone has an opinion and yet whatever path is followed the plane will still fly. I just wanted to answer the implied question posed in the quoted post.