Eriselle
Member
Hi VAF,
I did something stupid.
I have this RV-12 legacy SLSA, and I've been dealing with the avionics bay cover for a couple months now. My post history has a couple mentions of this, but the tl;dr is that the F-1240 avionics bay cover was bonded to the avionics bay. I had to do some heavy work on the avionics, so I had to remove the cover, and now I've been trying to put it back on. I removed all of the sealant, redid the fuel tank sealant without binding it to the cover, and have attempted no kidding six times now to get the RTV right and I just keep having problems with it.
Too little RTV to make a continuous seal, too much that it creates an airtight seal around a pocket of RTV that never cures because it has no exposure to air, I didn't align the F-1240 cover well and it smeared the bead before I got the cover in the right place... you name it, I've goofed it up. RTV is challenging to do well.
Part of the problem here is that the Vans instructions call for just one bead along the F-1201A Firewall Upper assembly, but the manufacturer had gone much further than that and created one continuous seal all the way along the top of the avionics bay side ribs (F-1202H-L/R) as well. Being SLSA, modifications aren't allowed, and that creates a confusing regulatory situation, because there are arguments for whether you must follow the KAI versus follow what the manufacturer did. Some of the attempts went poorly specifically because of the deviations that the manufacturer did. For example, the issue with some of the RTV never curing because it is sealed in too well between the two mating surfaces? No problem if you build the plane and never take the cover off, and it has years to cure. But for me, now, trying to create this seal as a gasket without waiting years to check on it, putting that much RTV material down just isn't working. Following the directions would not have resulted in this issue.
But yesterday, I came up with a brand new way to screw it up, and this one was the worst of all. It turns out that if you put RTV on too thick, it can apparently resist squishing enough to stretch the sheet metal skin. I did not notice that the F-1240 skin was bowing outward between the screws fastening the skin down. This resulted in some horrifying damage when I reattached the canopy and opened it. There is a small section of each side of F-1240 along the F-1202-H-L/R ribs that is JUST BARELY skimmed by a bit of the canopy near the hinge bolts when opening the canopy. But if the sides of F-1240 are sticking out even the tiniest bit, the canopy near the hinge can catch this edge and tragically bend it upward, and that's exactly what happened. This also trashed the paint on the inside edge of the canopy hinge arms that snagged the edge of the metal.
I kind of unbent the skin, but it's pretty bumpy in that area, and definitely not going to make a good sealing surface for a redo of the RTV. I'd like to salvage this piece if possible. I'm not sure how, but I'm thinking maybe find someone with an English wheel who could maybe help me smooth it out? Any advice is appreciated. Vans Store doesn't have this part for sale. Not sure if one can call Vans and order replacement parts this significant. Any experience with that would be appreciated.
A couple of pictures of the KAI with some markup are attached for illustration. The red line along the top of F-1201A is where Vans says to put the bead of RTV. The green, purple, and red combined is where the manufacturer had put RTV. What I attempted today that ended in this tragedy was just the red that Vans calls for plus the green bead. The second image depicts where on the skin the damage occurred.
I did something stupid.
I have this RV-12 legacy SLSA, and I've been dealing with the avionics bay cover for a couple months now. My post history has a couple mentions of this, but the tl;dr is that the F-1240 avionics bay cover was bonded to the avionics bay. I had to do some heavy work on the avionics, so I had to remove the cover, and now I've been trying to put it back on. I removed all of the sealant, redid the fuel tank sealant without binding it to the cover, and have attempted no kidding six times now to get the RTV right and I just keep having problems with it.
Too little RTV to make a continuous seal, too much that it creates an airtight seal around a pocket of RTV that never cures because it has no exposure to air, I didn't align the F-1240 cover well and it smeared the bead before I got the cover in the right place... you name it, I've goofed it up. RTV is challenging to do well.
Part of the problem here is that the Vans instructions call for just one bead along the F-1201A Firewall Upper assembly, but the manufacturer had gone much further than that and created one continuous seal all the way along the top of the avionics bay side ribs (F-1202H-L/R) as well. Being SLSA, modifications aren't allowed, and that creates a confusing regulatory situation, because there are arguments for whether you must follow the KAI versus follow what the manufacturer did. Some of the attempts went poorly specifically because of the deviations that the manufacturer did. For example, the issue with some of the RTV never curing because it is sealed in too well between the two mating surfaces? No problem if you build the plane and never take the cover off, and it has years to cure. But for me, now, trying to create this seal as a gasket without waiting years to check on it, putting that much RTV material down just isn't working. Following the directions would not have resulted in this issue.
But yesterday, I came up with a brand new way to screw it up, and this one was the worst of all. It turns out that if you put RTV on too thick, it can apparently resist squishing enough to stretch the sheet metal skin. I did not notice that the F-1240 skin was bowing outward between the screws fastening the skin down. This resulted in some horrifying damage when I reattached the canopy and opened it. There is a small section of each side of F-1240 along the F-1202-H-L/R ribs that is JUST BARELY skimmed by a bit of the canopy near the hinge bolts when opening the canopy. But if the sides of F-1240 are sticking out even the tiniest bit, the canopy near the hinge can catch this edge and tragically bend it upward, and that's exactly what happened. This also trashed the paint on the inside edge of the canopy hinge arms that snagged the edge of the metal.
I kind of unbent the skin, but it's pretty bumpy in that area, and definitely not going to make a good sealing surface for a redo of the RTV. I'd like to salvage this piece if possible. I'm not sure how, but I'm thinking maybe find someone with an English wheel who could maybe help me smooth it out? Any advice is appreciated. Vans Store doesn't have this part for sale. Not sure if one can call Vans and order replacement parts this significant. Any experience with that would be appreciated.
A couple of pictures of the KAI with some markup are attached for illustration. The red line along the top of F-1201A is where Vans says to put the bead of RTV. The green, purple, and red combined is where the manufacturer had put RTV. What I attempted today that ended in this tragedy was just the red that Vans calls for plus the green bead. The second image depicts where on the skin the damage occurred.
