EchoJuliet
Member
Let me be the first to put out a request for a 5'4", 125 lb. flexible mechanic to work this SB for me. LOL
Are you required to re-weigh the aircraft if you close it back up with a small person in the tailcone?
I guess it's a good thing I haven't attached the tail cone yet. I have the finished tail cone sitting on a stand in my garage. However, I think I might be less likely to cause any damage by putting some padding on the floor and then performing the service bulletin with the tail cone to the floor. Any thoughts?
I guess it's a good thing I haven't attached the tail cone yet. I have the finished tail cone sitting on a stand in my garage. However, I think I might be less likely to cause any damage by putting some padding on the floor and then performing the service bulletin with the tail cone to the floor. Any thoughts?
Almost seems like a doubler plate could be added on outside of skin similar to triangle plates on bottom of aircraft near wing center section. Crack appears to be in the skin and not the bulkhead. Otherwise, I have to find a 10 year-old kid to crawl into tail cone...
I wonder how hard it would be to support the tailcone vertically and stand inside to do the work?
I wonder how hard it would be to support the tailcone vertically and stand inside to do the work?
That's an interesting idea, Turner. The ceiling is too low to try this in my garage, but maybe the tail cone could be moved outside on a day when there isn't any wind!
i would like to know a lot more about the failure and why the other bulkheads won't follow . from what i read so far i think i would use the gusset vans is supplying and use it for a model to make brackets for the other bulkheads. crawling back there once more is bad enough.
That's an interesting idea, Turner. The ceiling is too low to try this in my garage, but maybe the tail cone could be moved outside on a day when there isn't any wind!
I’m with you Jim. Why not just put three doublers on from the outside and be done with it, cracks evident or not.
I'm with Steve and Jim. I wish Van's would re-think this repair/SB. I am not an engineer but the "clips" do not look robust enough and I suspect cracks will form even with the clips installed. I'm in favor of the external doublers cracks or not.
I wonder how hard it would be to support the tailcone vertically and stand inside to do the work?
5' 10" and 134 pounds. A walking broomstick, but it comes in handy now and then.
My entire USAF career working on SR-71s and RF-4Cs was a clamor of "Go get Gamble - that little &^%$ can fit anywhere!"
mike, i spent a week back there last fall, i am 70. lots of padding on the skin so the plywood kind of floats on the padding and doesn't really bear weight on the bulkheads. a led light for little heat and a forced fresh air supply back to where you are working. make sure the tail is solidly in place or you will be standing on your head, trapped. i was surprised that my cell phone worked fine in there. also, a layer of cardboard on top of everything so you can slide easily.
i know one afternoon i made 20 trips into the tail then back to the workbench.
once you get set up it wasn't bad but setup was time consuming. once the tank and everything is out of the way you and a helper [inside the tailcone] could knock it out in a day. someone has to be on the outside drilling rivets , right?
mike, i spent a week back there last fall, i am 70. lots of padding on the skin so the plywood kind of floats on the padding and doesn't really bear weight on the bulkheads. a led light for little heat and a forced fresh air supply back to where you are working. make sure the tail is solidly in place or you will be standing on your head, trapped. i was surprised that my cell phone worked fine in there. also, a layer of cardboard on top of everything so you can slide easily.
i know one afternoon i made 20 trips into the tail then back to the workbench.
once you get set up it wasn't bad but setup was time consuming. once the tank and everything is out of the way you and a helper [inside the tailcone] could knock it out in a day. someone has to be on the outside drilling rivets , right?
We can assume that Vans have done their analysis on the effectiveness of the clips, and personally I would prefer to install those than have to install and paint an external doubler, which by itself might not be enough to fix the problem. If it was, Vans may have gone that route as they did with the wing skin doublers. Without more information, we're just guessing.
I'm not a structures engineer, and I didn't stay at a Holiday Inn Express last night
That being said, I believe the cracks are caused by vibration and movement of the bulkhead, leading to the skin flexing - hence causing the fatigue cracks. An external gusset would transfer loading, but would probably just move the cracking to another location. It seems the clips are designed to support the bulkhead and reduce/eliminate the relative movement to the skin.
Bob,
Thanks for the encouragement and your suggestions. I guess the rivets on the bottom skins could be drilled out before crawling into the tail cone, drilling out the rivets on the bulkheads seems to be more problematic. I think I would definitely want someone on the outside to insert clecos and pull the rivets on the bottom skins after riveting the stiffeners to the bulkheads. This might eliminate multiple trips into the tailcone.
At least that's what I'm thinking right now.
Not a Boeing engineer but as Greg Hughes said, the issue is the lack of continuity of the bottom J stiffener either side of the bulkheads which interrupts the load path and also creates a sudden change in stfffness locally which allows flexing of the skin and leads to fatigue cracking. There are cutouts in the bulkhead in other locations to allow the stiffeners to pass through, but not on the bottom skin.First to admit I don't know much about building experimental planes that get riveted together out of aluminum, but it seems to me, within weight considerations... would additional stringers/ribs have decreased the level of risk of cracks being developed, in addition to the clips, in the original cone design?
Just trying to visualize and learn here... maybe some Boeing or Lockheed engineers can share some valuable experience in aircraft design and construction techniques, especially in faster planes that are fully pressurized to fly above 18,000 ft.
Not a Boeing engineer but as Greg Hughes said, the issue is the lack of continuity of the bottom J stiffener either side of the bulkheads which interrupts the load path and also creates a sudden change in stfffness locally which allows flexing of the skin and leads to fatigue cracking. There are cutouts in the bulkhead in other locations to allow the stiffeners to pass through, but not on the bottom skin.
When I start my CI in the next few weeks, I'll stuff my 6' tall, 130 pound, 18 year old bore scope into the tailcone and with his help, we'll git'r done!
Careful, people might start asking if they can borrow your tools! Heck, there're a lot of RV-12s in the Pacific Northwest. If the borescope can drive a car, it might even find a way to make some money having done the inspection and installation once already, hah.
Maybe Vans could post the size of the plywood needed to be placed in the tail one for this service bulletin
.Then we can have that ready when we start not have to run home to cut those pieces