Finished the F-704 Center Section - 3 hours

Small day today just finishing up the center section and getting it ready to put away. I decided not to grind down the F-704 center section sides for the wiring holes and instead opted to grind down the plastic bushing instead just as the instructions state. They actually turned out extremely well.



I then ran over to home depot and picked up some 2x2 oak blocks to make my center section spacers. I little bit of set up on the table say with some scrap wood and I dialed in the proper width of 1.438"




Once that was done I needed to open up the holes for the spacer bolts in the aft F-704E center section. I found it odd that the back section holes were a smaller size than the forward section.



Done and ready to store until I install on the forward fuselage.

Riveted the F-704 center section - 6 hours

I started the day riveting on the nut plates to the F-782B and F-783B supports. I used the NAS1097 rivets as the supports are thin material. I also installed the nut plates on the F-704M stiffeners however I used the AN426AD3 rivets on those as the material is much thicker.

Next I began to rivet the supports on the center section. I haven't bucked rivets with a bar in quite some time so I was a tad nervous about this.

I used a 2x4 clamped to the workbench as a bar support. The rivets turned out extremely well, and I soon regained my confidence with bucking.



All done the supports.

Next I needed to rivet the center section sides. I was concerned about the side moving with riveting so I greased up all 4 close tolerance bolts and inserted them into the center section. I then cleco'd all the holes and then began to squeeze the rivets.

After a few, I just found squeezing them a pain, so I opted back to the gun and bar. The riveting went extremely well and quick. Drilled out only 2 rivets I think. I have to say I am beginning to really love bucking (Thanks to the endless bucking of the wing skins....a person gets really good at it).

Center section riveting all done.

Worked on the F-782A & F-783B brackets - 4.5 hours

I started late in the day but managed to get a decent amount of work done on the center section. I started off with completing the nutplates on the top of the center section. I used NAS1097 rivets for these.

Next, I opened up all the holes for the fuel lines and brake lines.

I then broke the edges, scrubbed with scotchbrite, degrease, MEK and primed.

As I was waiting for the primer to dry, I made the F-904J spacers. They come pre-cut to nearly the perfect size back in the wing kit. Fortunately I had labelled their use previously and they were easy to dig out. I had chucked them in the drill press and polished them to proper size.

Easy peasy.

Assembled control sticks and fabricated F-704M stiffner - 5 hours

Now that the touch-up paint is dry I assembled the control sticks. I used my Aeroshell 22 synthetic grease on the bushings/control pivots. Movement is excellent.


Next step that the plans have you do is install the nutplates on the top of the center section. I have opted long ago the clean and prime all of the nutplates. Yes, this is a tedious task, but its what I have chosen based on my reading. I cleaned and primed 20 K1000-08 nut plates. While the primer was drying, I decided to fabricate the F-704M stiffeners. I cut the angles to approximate size and then ground the edges to exactly 4 5/8". This is fairly critical as they stiffeners sit very tight in the center section as I have found. 

I then marked center lines on the pieces so I could line up the holes. I then used masking tape on the center section to ensure that the stiffener would be centered in the web.

Next I had lined everything up and clamped the pieces to the web. I then carefully drilled a pilot hole in the bottom most piece. I disassembled the piece and checked my pilot hole for correct dimensions and then fished drilling on the drill press. Then I reassembled so I could match drill the other holes.

I repeated the process for the top most hole, checking again for correct dimensions and alignment. Drilling again on the drill press before re-assembly.

All the rest of the holes were drilled on the drill press.

Probably the most time consuming process but it is perfect. Next step I fitted the F-782B & 783B pieces and match drilled to the center section.
 
I then completed the nutplate holes on the F-704M stiffeners.



 

Removing stickers from powder coat pieces

So here is a neat trick. I always hated the paper stickers that Vans puts on the pieces as they never peel off nicely, When they are placed on bare aluminum parts its no big deal as Acetone and MEK take the stickers off. However this doesn't work on the powder coated parts as both Acetone and MEK seem to soften or dull the power coat finish. I think MEK would take off the coating completely if you rubbed hard enough.

I ended up using a damp rag and that easily removes the top paper layer of the sticker.




But what is left is the annoying part. The adhesive layer.

Take a different cloth and spray a bit of WD-40 and then wipe, and the Adhesive layer comes off in an instant. Better yet there is no dulling the powder coat finish.

More control mount and control stick work - 6 hours

Managed a pretty decent day in the garage. I was dreading cleaning up the cuts made in the control stick mounts. Basically the only way I could see doing it was to use good 'ol files. I clamped the pieces to the table and went to work. I was expecting it to take a long time since the aluminum was thick, but it goes extremely fast. I had everything done in just over a half of an hour. I took a little extra time to make sure that both pieces were equal and then I polished them.

I then fit the control stick cross member WD-610 to the mounts and found the correct combination of washers.






Next step that I wanted to do was fit all of the control stick pieces. This turned out to take a considerable amount of time and effort. All of the control pieces need a bit of work at the pivot point locations. The brass bushings do not fit nicely inside the control pivot points. They all need to be reamed. As well, the AN4-27 bolts do not fit nicely inside the bushings so the inside of the bushings need reamed as well. As it turns out, I don't have the proper sized reamers for this job. So I went old school on the task. Fortunately I have a good selection of drill bits and an endless supply of adhesive back sandpaper. I wrapped a small piece of 600 grit paper around a slightly smaller drill bit and used that to polish the inside of the control stick pivots.
 
 Working the pieces back and forth, stopping to check fit and redo many times till I was happy with the fit of the bushings and confirmed there was no binding. Next was to do the same to the bushings to allow good fitment of the AN4-27 bolts. Fortunately this process is quicker on brass than it is with steel.

After that The pieces are ready to assemble into the yokes of the WD-610 cross member. The plans have you grind the ends of the stick pivots and the bushings to allow a slip fit into WD-610. Using the exact same method used for the aileron pivots I trimmed down the bushing to the proper size. Again very tedious and time consuming work. In the end I had everything trimmed for a perfect fit an virtually zero play in the controls. Everything fits extremely well and no binding. I wanted to protect the exposed steel on the ends that were trimmed so I touched up with automotive touch-up paint that I have that is almost the same color as the Vans powder coating.


I want to be sure that I do not wreck the finish so I will give the paint 24 hours to dry before I assemble the sticks. Since I have a little time left, I moved on to countersinking the center section for the nut plates.
 
I had a difficult decision to make. The plans call for AD3-3.5 rivets to secure the nut plates however I have always been leery about countersinking too much. I'm terrified that I will go to far and end up having a "knife edged" hole that everyone wants to avoid. After much reading and discussing the matter with my buddy mike who is an experienced AME and builder. I've decided to use NAS1097 AD3 rivets on all the nut plates that are secured to thin aluminum. Anything thicker than 0.060" I will use the standard AD3 rivets.  

Drilled the control mounts - 5 hours

Next step was to "fabricate" the F-633 control mounts. I had to laugh because they are already fabricated, you just need to drill a few holes and lighten them up. I drilled the uppermost hole(s) to the dimension shown. The plans have you drill the hole to 3/16" dia, which is not enough for an AN3 bolt, very close, but not enough. So I polished the hole with the dremel and 800 grit sandpaper until I could press fit the bolt in.

Next step I bolted the control mount to the center section and carefully squared the mount with the center section using a big square. I checked this with a few different squares and few different ways. then I clamped the piece, re-checked square.

I then flipped the center section over and lightly back drilled the hole with a #12 bit to start a shallow pilot. I then removed the mount and set it up in the drill press and finished drilling the hole with the 3/16" bit. The result is a tight hole, but is perfect in fit and location with zero play.

Next the plans give you the option to cut down the angle for optional weight savings. Everyone seems to do this step on their build logs. So I figure why not.  I marked out the dimensions, and drilled the radius holes. Then I began to wonder, just how much weight savings is there? I should have weighed the piece before I drilled. But this will give you an idea of how little weight there is in those pieces. I suspect you save about 50 grams total. Haha, what a bunch of work for 50 grams. (I know is about the sum of all parts...but I just had to laugh)



Next step is to fit the control sticks at this point. I dug out the pieces and tried to fit the co-pilots control stick WD-611 & F-669 and it just wouldn't slip in. I see that I have some powder coating over-spray as well as a bump internally caused from the welding of the bracket on the outside.
 
In fact the overall fitment of the bushings, etc in the pieces is a bit poor and I will need to polish/ream so that nothing binds. This will take a little time. For the WD-611 piece, I softened the powder coating with MEK and then used some sand paper to take down the paint. I used the dremel to take down the weld bump and them polished the inside with 3m scotchbrite on the dremel. The fit is now great. I move onto the bushings tomorrow.   

Finished match drilling center section - 2 hours

It was a pretty quiet and small day. I managed to finish match drilling the #30 holes on the F-704A/B/C/D pieces on the drill press. Also countersunk the F-704G vertical bars. Then family came over so I couldn’t hide in the garage.   
 
 
One item that was bugging me was that when fitting the close tolerance bolts, one side of the section was a bit more troublesome and some of the anodizing has rubbed off inside the hole. The other sets did not look like this one. Due to the critical nature of this area, I was concerned that this could be an issue.

I had emailed Vans, and they indicated that rubbing off the anodizing was inevitable due to how tight those bolts are, but not to worry. Apply some grease to the area on final assembly and that will protect the finish.