Got out the old close quarter tool again from Cleaveland tools. If you have read any of my other posts about this tool, you know how much I cherish and utilize it to get into places that are just too small for conventional squeezers and dimple dies. I dimpled the two TE holes on the elevator tip using the back of a chair as a support for the elevator skin. Worked out quite well actually. It left both my hands free to focus on making the dimple, whereas previously I had to enlist the help of a friend to hold the skin for me.
Then I had to get creative. I needed to dimple 4 more holes deep inside the skin that attach the rear trim tab spar to the skin - two on the top and two on the bottom. The problem was that the stiffeners get in the way of trying to dimple these holes. I needed to find a way to elevate the tool enough to allow the skin to slide over the tool and sit flat over the top of it. I had a cedar 2x4 about 3.5 feet long in the garage that looked like it would work perfectly. Other builders that are obviously more intelligent than me have figured out that they needed to dimple these holes much earlier in the process. Oh, well, builds character I guess, if nothing else.
I removed the tool from the edge of the table, and re-attached it to the end of the 2x4. This elevated the tool enough to keep the flanges of the stiffeners from interfering with process to make the dimples as shown in the following sequence:
Here is the setup with the skin in postion over the tool ready to dimple the remaining spar attach holes:
and a shot from the side. Notice how the 2x4 slides nicely between the stiffeners, which allows the tool to be able to reach the holes and keeps the skin level over the tool:
This pic shows one of the two holes dimpled successfully. the ring around the dimple is normal. It is just slight impressions made by the edge of the dimple die on the alclad layer of aluminum that tell you that the die was seated over the hole correctly. It usually cleans up with Acetone or soap and water quite nicely:
and both holes dimpled:
Here is how I attached the tool to the 2x4. Again, I needed to elevate the skin somehow so that the skin would sit flat on the tool. Had I not done this, I would have had to force the skin down over the dimple die, putting pressure on the flanges of the stiffeners on either side of the hole, which might not have allowed a good dimple to form, and may have damaged the skin or the stiffeners in the process - not good. In actuality, a 2x2 would have been more than perfect for the job, but I used what I had in the shop at the time. As long as it slips in between the stiffeners on either side, it will work.
I quickly realized that I also needed to put the tool on one edge of the tool or the other of the 2x4. I had to move it to both sides of the 2x4 in order to allow it to reach all the holes on both sides of the skin. You can see the other mounting holes I drilled for the other positions that I used. The reason it has to be on one side or the other is to allow the die in the end of the tool to align with the holes that are closest to the stiffener flanges on either side of the hole.
And here is the entire setup. I just clamped the other end of the 2x4 to the table. I set the end of the tool from the edge of the table so that it would allow the front edges of the skin to lay down on the table to provide support and help level the skin out across the dimple die in the tool.
Here is the chair "tool." Hehe. Amazing what you can rig up if you put your mind to it. I used a blanket to keep the skin from getting marred up on the back of the chair. This ended up leveling the skin out just enough to keep it in proper position over the tool. In this situation I was attempting to dimple the last remaining nut plate rivet attachment holes with the 3/32 #40 dimple die. This did not work out as well as I had hoped, because the dimple has to go into the trim tab support bracket, which has very thick skin - much thicker than the elevator skin. The rivet gun just did not form the dimple very well, and I did not want to turn up the juice (air) on the gun as I did not want to damage the part. I have had quite enough of that over recent weeks as you well know.
Next is a close up of the not-quite-formed-yet dimple after attempting to form it on the tool. I had to revert to the C frame tool to resolve this. I could not get a squeezer into the access hole to get to this last set of nut plate holes. This was the only set of holes I could not get to with a squeezer. Lesson learned here is to attach the nut plates first, BEFORE attaching the support plate to the elevator skin. I still can't believe that Van's does not clearly explain this in the instructions. Enough ranting, I found a work around for the problem, so all is well. The hole in question is on the top of the pic.
Hmmm. I just realized I did not take pic of the C frame setup. So I will describe it here. Since the close quarter tool would not set the dimples very well, I removed the skin from the table, placed the C frame tool on the table, put the #40 dimple dies in the C Frame, with the male die sticking up as I usually do for the skins. I used the chair back to support the skin. I did NOT use the dimpling table - too much trouble to set it up for three lousy holes. Instead, I needed to slide the 2x4, long side up, under the skin near the edge of the table so that the skin would sit relatively flat over the dimple die in the C frame. The top skin was draped over the top of the ram after positioning the hole in the dimple die, so I held the top skin out of the way while I hammered the C Frame ram to create the dimples. I then needed to switch the dies from #40 to the #6 dimple dies for the hole in the middle that will accept the #6 screw.
Here is a blurry pic with all of the nut plate holes in the trim support bracket dimpled (finally!) The set of holes I dimpled with this technique are the ones in the top middle of the photo. The shiny spots around some of the holes are where the primer has sadly flaked off. I will touch up these areas later when I am in full primer mode for the rest of the parts. The flaking primer does not concern me much. Normally all the holes are drilled, deburred and dimpled prior to applying the primer, but in this case the dimpling was done after the primer was applied. All that banging and bending of metal can certainly take a toll on any surface coating. Just reprime it and no problems.
And here is a trial fit of the trim servo access cover plate with the screws inserted into the holes just to check for hole clearance and flushness of the screw heads inside the dimples in the cover, which are inserted into the dimples in the support bracket underneath. This should work out nice after the nut plates are riveted in place, which is my next challenge.
And lastly a blurry pic of the #6 dimple die in the C frame. I was trying to show the flat side of the male die that I grinded off so that it would clear the elevator skin that overlaps the trim support bracket. Hopefully you get the idea behind why I needed to do this by looking at the screw hole locations and edges of the cover plate in the pic above. There is not a lot of material sticking out from underneath the skin to hold all the nut plates, dimpled holes, and rivets in place. The dimple dies are just a bit wider than the amount of material sticking out, which is why I had to grind down one side of the dimple die. The flat spot is on the male die on the bottom, on the left side. I did not have to grind it down very much to clear the skin, but it still needed to be done.
I think I have resolved how I am going to set the rivets for the one nut pate that I cannot reach with the squeezer. I may use the C frame to set the two nut plate attach rivets. Sure wish I would have attached these confounded things before I attached the support bracket to the skin. Sorry, I said that already, didn't I?
I will have to get used to dealing with nut plates. they seem to require a lot of prep work, and that kind of sucks. When you start building the wings your very first step is to counterskink a million holes for the fuel tank attach brackets on the main wing spar. OK so maybe not a million holes, but you get the picture, right?
I then plan to use a ton of nut plates in the fuselage in the floor panels, as well as hinged access plates, so that I can gain access to critical areas of the plane without having to drill out rivets. This will add a lot of work to the fuselage build, but in the end it wil be worth it.
Some builders comment that it is easier and takes less time to drill out the rivets than to install nut plates and screws. What they don't understand is that if you are stuck in nowhere USA one day, without a rivet gun, compressor, drill, spare rivets, and a bucking bar, it is very difficult get into the critical area to troubleshoot the problem, and remove, replace, or repair a component, and then close the floor back up again, unless you have access plates or panel doors installed.
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