Now for the fun part, I finally got started on the wings after all of the dinking around with finishing up the empennage. Lots of progress this week as I logged 19 hrs in the shop. I was gung ho to get drilling on these spars...but wow, it was a flashback to when I first started my empennage. I read the plans, looked at the drawings, read the plans again, looked at the drawings again and was paralyzed to finger the trigger on the drill to cut some metal!! haha! I literally spent at least a half hour looking everything over before drilling to make sure I wasnt making any mistakes. This, after I had already previewed the plans before the wings arrived so I was familiar with the task at hand. These wing spars are probably the single most expensive parts in the entire airframe....you do not want to screw these up! On top of the fact that these buggers, more than any other part on the entire airplane is literally what your ass is hangin on in flight. If my engine quits in flight, I have lots of options for a safe outcome. If my wing seperates in flight, the only option is to kiss your ass goodbye and wait for impact with ol' mother earth. Consequently, there should be a high degree of concentration to do a good job on these puppies...so all of this gave me pause. First order of businees is attaching all of the fuel tank attach nut plates. I think there are 64 #8 screws per tank? So if thats correct,128 nut plates, which means 3 machine countersink holes per nut plate. Even without the math (I'm too lazy), you should be getting the picture here....lots and lots of countersinking to be done. On top of the fact that the thru holes for the #8 screws is too big to hold the pilot on the #30 countersink. So what happens is the countersink tends to chatter because of the loose fit. Van's states this will happen and its ok, and really it would be for the design intent since the nut plate is the aligning feature. Although I certainly cant accept shoddy work like that on my plane. ;) So, reading through Dan Checkoway's site, he came up with a solution by adding a scrap piece of angle alum to act as a pilot hole. I didnt do it exactly like he did because I only did one hole at a time but it worked out good, just time consuming. The countersink for the #8 screws really is too deep for the 0.062" alum angle so it blows out the thru hole which makes it very difficult to keep the countersink nice and symmetric. Not a big deal because the thru hole isnt being used for alignment, so its just a cosmetic issue. I did my best to keep it looking nice, some of them came out obround but most of them came out real nice. I was happy with my efforts on this excercise. I also, because of my previous building experience did the bottom side first. That worked out good, as my first ones were the worst of the bunch...but nodody will every see them. By the time I got to the top side I had it dialed in nicely. The microstop really worked great. I set it up initially, tightened everything down and never had to readjust it! I had been told to be careful with this tool as it has a tendency to move..I kept checking, but 'no joy'. Very consistent depth on the countersinks if used properly.
An interesting label Van's puts on the spars telling you not to ream the holes for the close tolerance bolts that attach to the center section. They are tight...and are supposed to be for obvious reasons! You would think a builder would consider this, but ya just never know and its better to be safe and put a notice just in case. You certainly dont want your wing attach bolts shearing while pulling a 3g turn! That would make for a bad day!
Marking the wings so that I have the correct orientation, dont want to build these suckers upside down! They are almost symmetrical, very subtle differences to tell you whats up and down. I expect, after a while I will be very intimate as to which is which, but until then better to be safe than sorry.
My homemade depth guage tool. A #8 screw ground down so just the head is left. Then I super glued that to the end of allen wrench. Now I can check my countersink depth as I go. Now, keep in mind that the screw wont actually go in this countersunk hole, the dimpled tank skin will and the screw will go in the dimpled skin. But essentially the dimple is the same size as the screw head (I checked..its a smidge on the shallow side but I think it'll be ok for a nice tight fit) so this is what Van's says to use. Much like factory rivet heads, after drilling so many, after a while I could tell by the look if it was deep enough so I only check about every five.
And a shot of a test fit with screw and nut plate...looks good eh?
My added piece of angle alum for the pilot hole...I had this left over from my rudder excercise. In this photo, you can see I am using clamps...that didnt work too well as they tended to move around too much. I later switched to cleco-ing the angle in place...much better results.
And the finished goods...that looks purdy doesnt it?!
Looks like this was done on a CNC machine doesnt it? hehe
On a different note, this was my 'fathers day' present to myself. Yeah, yeah, not a father unless you count my pets but hey it was marked down fathers day weeked from $58 to $35 at Home Depot. Couldnt pass it up...and wow, it sure is nice to have to clean up all of the alum shavings from the countersinking.
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