In order to joint the two F-631A's together, the C-704's drill pattern needed to be backdrilled to a temporary drill guide (left). This is because the C-704 sits on the inside of the channel with no way to backdrill the F-631A. Since 1/2 of the C-704 is drilled to one of the channels, there are enough holes to drill the other side when it is mounted in the fuselage.
I should of done this a while ago, but I drilled the C-704 to one side of the F-631A.
I then took out the C-704 from the inside of the channel and clecoed on my template.
I clamped the hell of of the channel and the canopy. Amazingly this brought everything together.
I stole this idea from another builders website - put a 25 pound weight on top of the canopy to hole everything down tight. I thought it was a good idea at first, but I don't think I am going to use it anymore. I am worried when I drill the sides the canopy will be in a compressed state that could cause cracking later on when the weight is removed.
Here was the real key for my F-631A to sit nice and flush with the inside of the canopy - to have a clamp hole together the rollbar, channel and canopy.
I drilled the F-631A to the side frame with one cleco for now. BTW, I got inside the fuse to do all of this. Van's tells you to get this all setup and carefully remove the canopy and drill, but why not just get in? It wont get any better than this!
Here are where the two F-631A's come together. I will use the template to backdrill the other side.
Done and done, well, except for the top two holes, the canopy interfered.
And finally I drilled the rest of the holes to the side rails.
I did some final fit testing of the canopy. For some reason, between the arrows, the canopy wasn't sitting flush with this area. I needed to bent the top of the side rail inboard for the two to sit flush with each other.
Next I marked out where the screw holes will go. I am using 3" spacing, as opposed to the 2.5" Van's recommends, to avoid conflicts with the rivets on the rollbar.
On the top I am using a tighter 1.5" spacing for the top two screws.
Next I put the C-704 in. I drilled the holes I couldn't get in the fuselage.
Also I noticed this close hole interference between the bottom of the F-631A and the WD-725 side rails. I am not too concerned because the F-631A is sandwiched between the WD-725 and WD-622 latch lug.
Last Modified: July 12, 2021