Fitting the F-902 Bulkheads - 6 hours

Started the morning with drilling the bottom of the F-684 gussets.

Next step I drilled the #19 holes for the nutplates.

Now that I have everything fitted up. I double checked my edge distance on the lower engine mounting brackets and I have about 0.240" edge distance so well within min. requirements.


Next I fitted up the F-902 bulkheads and then I noticed that the F-713 Auxillary longerons do not sit nicely in the cutouts of the F-902 bulkheads. Its like the longerons are too low...




I cleco'd on the F-7101 gear attach web and that too needs to be trimmed along the top in order to sit correctly. I'm really scratching my head on this one. After a bit, It finally dawned on me what I had done... The instructions on page 8-8 have you "draw lengthwise centerlines on Auxiliary Longerons F-713-L&R...". I assumed they meant the backside of the longeron and I drew a line perfectly down the center. It now occurs to me that if I had drawn the centerline based off the inside face(s) of the angle and drilled according to that dimension then I would have the correct fit as the longeron would be offset the 1/16" from where I currently have it placed.

Makes so much more sense now. That's why I was having such edge distance issues on the F-684 gussets, they were being placed 1/16" too high.

What happens if I trim the bulkheads and gear attach web to accommodate the lower longeron where I drilled it?. I did some checking on this. I am going to run into an edge distance issue on the F-796B-L/R tank attach angles.






If I follow the plans, then edge distance for the AN3 bolt is ok (No room for error though). However if I maintain the longeron where I have it...the edge distance is blown. I did up a test piece to see how much material I had to work and its just not enough.

I called Van's and the advice was if I already had it riveted in, then I'd just have to go with it. But since everything is just cleco'd the best option is to redo the F-713 longerons. Crappy, but it is the right thing to do. Order was placed for new parts...we will come back to this another day.

In the meantime...I checked the fit between the F-902 bulkhead and the F-7101 gear attach web and I do have a bit of a gap. Seems this is fairly common among the various builders websites so I too will be making a space for both the Left and Right sides out of 0.063" material.
 

Worked on the F-684 gussets - 10 hours

Spent the entire day working on the F-684 gussets. Ughhh these were not easy to work with! 

Things started off all right with making the gusset, however I didn't pay enough attention to where the 1/8" dia holes are to be drilled. I soon figured out that I drilled them in the wrong location and I was going to have edge distance issues on the firewall angle. Crap. 

Well...I have one sq ft of 0.063" material so I can easily make new gussets. But I decided that I was going to make a paper template first to double check all fit before I fabricated new pieces.  I drew up a template on autoCAD and clamped/cleco'd it to the assembly. 


After making a few slight adjustments to help with increasing edge distances. I cut out my new gussets.
 

It was an immense amount of work, but I am pleased with how they turned out. 

Installing the F-717 longerons to the Engine Brackets - 9 hours

Installing the F-717 longerons has been weighing heavy on my mind for some time now. Reading other build sites has noted that the edge distance at this location can be quite tight, and sometimes non existent if you follow the drawings.

Being mindful of this, I used a small piece of scrap aluminum angle to start measuring things out. Using an edge distance of 1.5 times the bolt diameter gave me a minimum edge distance of 0.28125" and marking the line on the angle at 0.500" (as per the drawings) leaves a scenario where theoretically it will work, but there is just no room for error, and for a guy doing this by hand in a garage. Its not great.




So taking the advice from other build logs, I moved the center-line of the bolts 1/16" inboard. The dimension is then 7/16" (0.4375") rather than the specified 0.500". This will allow me to have a larger margin of safety on the edge distance of about 0.373". Of course I called Van's before tech support closed, just to double check if they had concerns with my logic and the advice for me was build on.


Now its time to do the actual drilling. I started by marking out the lines and using a punch to set the center point of each hole.

Next step I drilled all of the holes to #40 so I can get a good look at the center lines drawn out on the mounting brackets below.

I then started drilling each hole to #40 and inserting a cleco. Then I started working my way up in drill sizes. #30, #25 #21 and finally ended with a 3/16" reamer for the AN3 bolt. Im really pleased with how it turned out. 



By the end of the evening, I had just enough gas left to finally complete the cutouts for the F-717 longerons. I hesitated to do these right at the beginning as I did fear I would mess up the longeron drilling. And who wants to keep cutting down multiple angles...not me.

Cut and Fit the F-717 Longerons - 3 hours

I need to cut the F-717 longerons. I cut the angle just a tad bit longer than the plans indicated.

I started to scallop the angle around the engine mount brackets in effort to maximize edge distances. I managed to get the scallops and fit really tight, but I am contemplating backing these off at some point just to alleviate some pressure points along the welds. just by the continued fitting of the angle, marks are beginning to show on the highpoints of the welds.


I noticed as well that the longerons interfere with the F-713 longerons. I too will have to trim the corners of the F-717 just like everyone else does in the build logs.

Finished the F-719 Stiffeners - 3 hours

I didn’t exactly sleep that well. I was thinking about how on earth I was going to trill the holes for the F-719B clips. I thought about removing the skins to try and drill, but I feared that it could make things move a bit too much. Well I finally decided to clamp the clips to the firewall and carefully remove the firewall.



I then was able to clearly mark the angle/position of the clips.

I removed the clip and then draw a line to where the hole needs to be drilled in the firewall angle according to the plans. I could then re-position the clips and clamp then in the correct spot and drill the needed holes. I was sweating bullets but it worked out really well.



Next I took the direction from other build logs and I clamped the clips to the F-719 stiffeners. I then unclecoed the skins just enough to allow me to use a very long #30 drill bit to drill the next couple holes.


Many hours spend to do a very small task. But I couldn’t be more happy with the results.

I’m now a bit concerned on how best to do the F-717 lower longeron. Reading the other blogs I see that this is another source of brain damage for some. Let’s see what I can figure out.

Finished the F-713 Longeron and started F-719 Stiffener - 8 hours

Feeling confident to proceed. I first put a twist in the longerons to ensure proper fit. Next I started to drill the F-713 Longeron to the lower engine bracket/weldment. I started by just using the drill bit to make the initial mark into the steel bracket.

I could then remove the whole firewall and then get a good look at how my edge distances were going to end up. A tedious process but I can make absolute sure the the holes were going to be correct.




Once I had the first (and most critical hole dialed in) I then finished drilling it. Using the palm drill I’m able to adjust slightly where I want the hole to be.Then I re assembled and then drilled the rest of the holes in place. I’m extremely happy how these turned out.


Next I started by fabricating the F-719B Angle clips. I drilled the holes first to ensure proper edge distances, however I didn’t realize that most people don’t drill the holes yet due to difficulties on how to drill these to the firewall. Oh well....let see how this goes.

Took me a while to shape them cause they heat up so quick on the sanding station.

I then started on the F-719 stiffeners. I wanted to trim the aft end to the F-704 center section similar to the F-713 Longeron but I managed to figure it out. In the end I don’t think it’s necessary but I want to do it. I left the stiffener long and just scalloped the forward end to fit the firewall. Again not necessary but its just an extra step I don’t mind taking


Can you tell Mike Patey is inspiring me to work on the little details!

Next step is the tough part....how on earth am I going to drill the F-719B clips to the stiffeners..I’m going to have to think on this a bit.

Finished the left gear leg and fitted the F-713 longerons - 8 hours

Nice big day working in the garage on the plane! I haven't had a long build session like this in some time. I am starting some holidays so hopefully I am productive over the next week.

Now that I have confidence from the right gear leg installation, I was then able to transfer all of that over to the left side and I then made short work of cutting the left gear leg cutout. I'm really pleased with the fit. I decided that I will cut the holes for the brake lines through the bottom skin at a later time. The holes do not seem to line up perfectly with the holes in the gear leg weldments so I will take a look at that before I drill.




I started next on the F-713 longerons. I drew a line down the middle of the flanges.

UPDATE - The instructions indicate "Draw lengthwise centerlines on Auxilary Longerons F-713-R&L" (See 8-8) however I have learned the hard way that the centerline needs to be drawn according to the inside face of the longeron, not the backside of the longeron. This will become very apperant when you fit the F-902 bulkhead and the F-7101 gear attach web. The longeron is obviously 1/16" too low for correct fit. See my blog entry August 2, 2020 for detailed info.


I trimmed/angled the edges of the longerons to mat against the F-704 center section and I also did the same for the end that mats against the firewall. Why not get everything sitting nice and tight?  I then began drilling the longerons to the side skin.


Again, a very slow and tedious process as I really am concerned with the edge distances in this area. Especially where the longeron meets the lower engine mount bracket.  I used a pen to mark the holes from the side skin to the engine bracket. Then I marked out the minimum edge distances. As you can see, there is not much room for error here. It will work, but I am going to have to be very careful of the placement of these holes before I drill.