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 beburring wheels.  When I was deburring, it ground down these deburring wheels like wood on a lathe.  They eventually got the firewall deburred, 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, deburred, and countersunk.  I am still not complete, I still need to dimple the firewall.