Next I was ready to drill the rivet holes into the bulkhead. Luckily the drill press was nice this go round (thanks to new drill bits I ordered)
Super happy with how everything lined up. No sloppy work here.
Next I did a little homework on which holes needed to be dimpled in the bulkhead. I see that from some build logs many have dimpled all the holes in the tie-down bar, which I suspect isn’t correct. Took me a little time but found out that the set of four holes towards the bottom aren’t dimpled/countersunk as they will be bolted later.
Here is everything sorted. Most holes are dimpled in the bulkhead, and just 4 holes are countersunk.
Fortunately my buddy Mike had a gift for me. Another....Yes Another one. 0.063x3/4x3/4 angle so I could resolve my dump edge distance issue that I had the other day. This time, I threw Van’s dimensions out and cut the piece 24.5” to fit it perfectly in the web.
Next I drew the radius of the flange on the angle and shaped the end of the angle. This allowed the maximum edge distance possible for all holes. I’m not going to run into this issue again...
Once I had the fitting of the new angle done. I clamped the F-729C angle on top and re-checked the top most rivet hole to ensure that I wasnt going to have edge distance issues on this one.
Tons of room!
I then drilled the new F-729B angle to the web.
I'm now ready to cleco everything together and check the alignment of the elevator bellcrank axis. From what I can tell (and its not easy to check things at this point) the holes only seem off about 1/16". Way better than my first attempt. However, I'm shy about drilling both those 1/4" holes right now because the alignment has much to do about the final positioning of the bulkhead. What I'm thinking of doing is avoiding drilling the 1/4" holes in the angles/webs until the Fuselage is more assembled (Just before I have to rivet in the F-728 assembly) My thinking is this scenario will help ensure that the axis bolt can be drilled perpendicular to building lines with certainty. I've been thinking pots on how I can do this and reached out on the forums to see if anyone else has done this.
I think I will end up making an oak drilling block/guide once I can ensure everything is square once the fuse is all cleco'd up. that's the best way I see to ensure it is drilled the best way possible
Next I cleco'd the assembly and match drilled the holes.
Once I had everything together. I noticed how the F-730 pate and the flanges on the webs seem to interfere with the one legged nutplates that get installed at a later time. It looks like the interference can make mounting the nutplates fairly difficult later, so I decided to make some relief cuts. On the left side, its just the flange that interferes with the nutplate. A round chainsaw file and some buffing with 3M made short work of this.
However the right side is a bit more problematic. I filed F-730 down for the nutplate, however it occured to me after that the lower most #40 hole is shifted to the right slighty preventing proper edge distance for a dimpled hole. Well there is some confusion as to what the correct edge distance is as I describe below. But the edge distance I have to work with is now 0.184". Worst case is that I re-make or reorder F-730 which is super simple to do. Another option if I can't use the hole is to make another #40 hole just below it with proper edge distance.
If I reference the MIL-R-47196A spec on Van's FAQ page, then I am all good as it states minimum edge distance is 0.154". However if I reference the original 1977 version then I have an edge distance issue at it states that the edge distance is actually 0.219". I'm a bit worried that maybe there was an error when they reproduced the MILSpec and mislabeled the "A & B" "C & D" measurements. I've reached out on the forums, but got little response. I'll see what Van's says.
Update: Vans says its all good and build on.
