A little priming of firewall parts and I am ready to rivet the firewall together.  Them Hyloft racks also come in handy for hanging parts to dry....

Van's instructions basically say rivet firewall components together.  Not a lot of detail....  After looking at other builders web sites, the method pretty much used is to lay the firewall down on a bunch of blocks and put your back rivet plate on top of other blocks and back rivet everything together.  For the edge stiffeners, you can get a squeezer in and do those.  They were no brainers.  Anyway, I had a couple of problems with riveting the firewall:

• Most of the rivet callouts appears to be 1/2 to 1 length short of what they should be.  This was somewhat frustrating in that when I used the size that Van's called out, the shop heads turned out really short.  When I bumped the rivets up one size, I got the right sized shop heads, but I ended up having to drill several rivets out as they would tend to bend over.  I ended up drilling out more rivets on the firewall than I have probably drilled out on the whole rest of the plane.  I ended up getting nice looking rivets, but it was a long painful process.
• It is very difficult to get the firewall to lay down flat on the back rivet plate.  Because of that, I had several rivets set high and had to be drilled out.  Good thing about these, they drill out pretty easy...

 

I bucked a couple of rivets on the engine mount brackets and the challenge I had here is that there is really no good way to hold the firewall while you do this.  The best thing I found was to put blocks on both sides of the firewall and then clamp the blocks down to the table.  It didn't totally immobilize the firewall, but it held it well enough I could buck a couple of the hard to get at rivets.

The reason that I bucked a couple of the engine mount rivets was that it was next to impossible to get at them with a rivet gun and it was also impossible to get the firewall to lay flat against the back rivet plate.  What are the other options???

Anyway, I bucked the two rivets on the lower left of this mount.  I am really happy with the shop heads on all of my engine mounts.  I used rivets that were 1 size larger than Van's calls out and all of my shop heads look great.

When I got to the F601J  angles, the rivets along the inside angle are impossible to back rivet because you can't get your rivet gun in along the angle and you can't buck the rivets because you just end up disfiguring the shop heads and gouging the inside radius of the F601J angle.  What I ended up doing here is setting the firewall on the back rivet plate and taking the shaft out of my C-frame dimpler, installing a flat rivet set and striking the C-frame shaft with a hammer to set the shop head.  It actually only took 3 or 4 blows with a hammer to form the shop heads.  Considering the rivets set on the inside radius of the F601J angle, they turned out pretty well.  They are not great, but they are good....

Anyway, the firewall is done.  For a structure that looks like it would be easy to rivet, it was sure time consuming and I ended up drilling out a ton of rivets in order to get them right.

I started day 3 of my weekend drilling the F-601J angles to the firewall.  Of course being attentive to the print (DWG-19) or so I thought, and Van's instructions it states that you will have to radius the angle (in two places) in order for the 601J to fit properly.  The highlighted one below is my instruction of interest.  Read on...

After radiusing the F-601J angle, I clamped it up against the F-601M-1 (firewall bottom stiffener) and the F-601N (center stiffener) in order to match drill the holes.  Now a couple of things here that I was attentive to.

• The F-601M-1 stiffener (bottom stiffener) is thicker than the F-601N stiffeners.  Therefore, if you just clamp the F-601J angle to the stiffeners, it is possible to clamp it at a slight angle which could result in some funky holes through the thick F-601J angle.
• When you assemble this group of parts for final installation, there are two gussets that sit underneath the F-601J angles.  Since there was no way to hold alignment of those gussets while drilling the F-601J angles, I removed them (to be all drilled together later).
• In order to properly align the F-601J angle to the center stiffener (F-601N), I placed the F-601G gusset underneath the F-601J angle (just far enough to rest the F-601J angle on and accessible enough that I could pull it back out after clamping the F601J angle with the C-clamp). 

Pretty happy with the look and feel of the angles (until later) read on.

Everything sat just as I had planned.

I drilled just enough holes to hold the F-601J angles with clecoes, then I removed the clamps.  I then re-assembled with F-601J with the two gussets in place and clecoed.  With the three holes drilled as shown, it was enough holes to hold the gussets and angle in place so that I could finish drilling.

A picture of the F-601H gusset in place.  I am pretty amazed (at times) how accurate Van's parts can be.  You can see how well everything lines up.

The F-601G gusset in place.  Like I said, until you get some holes drilled in the F-601J angles, it would be almost impossible to keep the gussets accurately lined up during the drilling process.

Okay, here is where I got that sinking feeling.  If you read on the DWG-19 below, you can see that it says to leave a 3/32" gap between the top face of the F-601M stiffener and bottom of the F-601J angle.  If you do not radius the bottom of the F-601J angle, I will bet that will be pretty darn close to that 3/32".  Van's instructions just state to "use the dimension given on DWG 19 for vertical alignment."  I guess that I could also argue, in Van's defense, that the print area highlighted at the top of this page is not actually a dimension.  It would have been nice, however, if those two instructions could have been in the same location on the print.

So, the question is, what was Van's true intention here?

I looked forward in the fuselage (DWG-23) to see if this 3/32" will be a problem later on, I cannot see conflicts, but I am going to ask around.

UPDATE (11/20/07):  I did some asking around about the F601J angles.  I was correct in that the only thing that these angles connect to in the mid fuselage is the floor stiffeners (F-772B).  What I was told is that it is important for the F601J angles to lay flat on the firewall (which means that it is important to properly radius the back side of the F601J angles to fit inside the F-601M-1 (bottom firewall stiffener).

The next two pictures are from flying RV-7's.  It is hard to tell, however, it looks like the F-601J angles are radiused up against the F-601M stiffener.

When I zoom in on this picture of this guys installation, it sure looks like the F-601J angle sits on the F-601M stiffener too.

Moving on, I went to debur the stainless steel firewall.  The firewall is pretty rough on leather gloves and 3M de-burring wheels.  When I was deburring, it ground down these deburring wheels like wood on a lathe.  They eventually got the firewall de-burred, but that stainless is hard to debur.

During countersinking of the firewall stiffeners, some of them (F-601D and F-601N) were thin enough that the countersink pilot doesn't have enough material to hold the cutter.  As in the wings, I drilled and clecoed a scrap piece of aluminum to hold the countersink cutter.  Worked great, as usual.

After 10 hours, I had everything drilled, de-burred, and countersunk.  I am still not complete, I still need to dimple the firewall.

I am not completely done with my wings yet as I still need to drill the flap hinge to the wing, but even with that yet to be done, I decided to start working on the fuselage.  It is ABOUT TIME!!!!!  It felt good to start working on something different...

First thing that Van's calls out making is the F-601J-L (-R) angles. DWG 19 states to make the angles out of AA6-187x2x2 1/2.  After digging out the fuselage parts, I found the angle stock.  This is some thick stuff>>  Translation>>>  The band saw ain't going to cut this worth a crap.

After cutting the angles to length, I clamped them together.  One of my developing pet peeves is that when I have to fabricate two identical components, I have a hard time making them look identical.  So to solve that, I clamped the two angles together.  I broke out the Vixen file to dress up the edges.  As expected, the band saw somewhat mangled the edge being cut.  I used the vixen file to straighten and dress up the edges.  After some significant filing, the angles started looking pretty good.

I used  two clamps to hold the angles together.  When filing, I secured the angles in the bench vice.

After 20 minutes of filing, this one edge started looking really good...

After over an hour of filing, I was getting close.

OKAY, when starting the firewall, Van's makes mention that the stainless steel firewall can be very sharp.  I am slow to learn.... Within 10 minutes, I was lining up parts on the firewall and couldn't figure out where all this "red" stuff was coming  from.  Sure enough, a quick scan of my hands and I had sliced my finger open.  It wasn't like a paper cut in that when you get a paper cut, it hurts.  Slicing my finger on the stainless firewall, I didn't even feel it when it happened.

For those unfortunate bleeding incidents (especially on your hands), having a bottle of New Skin around is very helpful.  It is a flexible bandage which worked great at preventing me from re-opening my new injury.

The rest of the day while handling the firewall, I religiously kept my mechanics gloves on.  The firewall is so sharp, I could see slivers of leather throughout the day as the firewall was doing its best to cut through my gloves.

Alright, after recovering my minor trauma injury, I moved on to fabricating Brake Plate (F-601TD). This is only needed for the tail dragger flavor of the RV-7...  I cut the brake plate to dimensions as called out in DWG-19 from .063 2024-T3 Alclad.  Next thing was to figure out how to align the reinforcement plate to be centered over the pre-punched holes in the firewall.

I basically drew vertical and horizontal lines extending from the center rivet holes.

I also drew horizontal and vertical center lines on the brake plate.  I then overlaid the two sets of center lines and clamped into place.

I bought these large vise grip clamps and they worked great to hold the brake plate into position.  Once I got it locked down and verified that everything was lined up, I flipped the firewall over and drilled through the pre-punched holes in the firewall, clecoing as I went.

The larger holes are drilled out to 7/16".  I used a well Boelube’d unibit to drill these holes to size.

Everything looks well centered and squared up.  Good thing, I would hate to have to replace the firewall due to a boo boo.

Next I fabricated the F-601E-1 stiffener using angle stock from AA6-063x3/4x3/4.  This was pretty straight forward.  I can't figure out why Van's didn't have this angle pre-cut and pre-punched like all the other angles on the firewall.

Next task was to fabricate the F-601P spacers which go under the upper engine mounts and above the F-601D stiffeners.

Once I got the spacers prepped to my satisfaction, I clamped them in place using the vice grip clamp I used earlier, flipped the firewall over and drilling through the pre-punched holes in the firewall.

The spacers just fit in there perfectly. 

After about 10 hours of fabricating and drilling, this is what I have to show for it.

I wonder if I will ever finish this project???