The temperature in the garage, even with a fan blowing directly on me, has definitely reached the ‘too hot for airplane work’ level!  However, I took some time off from work and figured I better work on the plane at least a little bit.  So, I spent an hour deburring and dimpling a few of the center fuselage parts.  I only made it through the center section bulkheads and two of the seat ribs before deciding to quit since I was spending more time wiping sweat off the parts than actually working on them.  There’s still a lot of work to be done on the center fuselage before riveting can begin.

I didn’t have much time to work on the plane today, but my goal was to get the center fuselage ready for final prep and disassembled.  The only thing I had left to do on the structure was to countersink four holes on the bottom skin/forward center section.  The plans are very clear that this is to be done while the bottom skin is attached to the forward center section, but to get to this area, I would need to flip the structure over.  So, I got Amber to help for a couple of minutes.

Once the assembly was flipped, it took me a bit of time to figure out exactly which four holes get countersunk.  After counting holes on the plans over and over, I finally decided it was the 11th and 19th hole from each side on the forward most row that attaches the bottom skin to the forward half of the center section.  Once identified, it was easy to countersink the holes since I always have one countersink cage set up with a #40 countersink bit.

It’s a little difficult to see in this picture, but the hole in the middle is countersunk. Four holes on the forward row have to be countersunk…it’s the 11th and 19th hole from both sides.

After countersinking, I removed the bottom skin, and then had Amber help me flip the structure over one more time.  Once flipped right side up again, I marked the location of all the seat and baggage ribs so that I can return them to the same place during final assembly.  Then, everything came apart.  The fun part, initial assembly, is now finished, and the least fun part, final prep, is about to start.  To make matters worse, there are a lot of parts that need a lot of final prep on the center fuselage.

The center fuselage structure is now disassembled. It’s going to take a while to get all of this deburred, dimpled, etc.

In my last post, I stated that my work sessions would probably become more infrequent due to the summer heat.  Of course, a couple of days later, the temperature plummets to a chilly 75F.  Perfect for working in the garage!

Today, I resumed where I left off on the aileron trim bracket.  All I had done thus far was to cut the bracket to the width specified in the plans.  With the bracket trimmed, I located the correct seat floor panel and used the holes in the panel to match-drill mounting holes in the bracket.  It is important that you use the floor, not the ribs, because the location of the holes in the floor panel are fixed.  The tops of the seat ribs can flex, so the positioning may not be exact.

The trim bracket is matched drilled to the seat floor since the spacing here is correct. The spacing on the rib flanges will be slightly off due to bowing of the ribs.

Once the first two holes were drilled in the trim bracket, I was ready to attach the bracket to the seat ribs.  However, I first had to remove two nutplates from the ribs.  I installed these when called for in the plans, but, since the aileron trim plans are separate from the main plans, I didn’t realize they weren’t needed.  With the nutplates out, I clecoed the bracket to the ribs, and then measured, marked and drilled, two additional mounting holes through the ribs and bracket.

I had to remove a couple of seat rib nutplates, and then continue fitting the trim bracket to the seat ribs.

Next, I trimmed and drilled the plastic block that holds the trim weldment.  Two holes have to be drilled for bolts/screws, a notch must be cut for cotter pin installation, and one edge has to be chamfered to allow the block to nest against the bracket’s flange.

The trim weldment block gets modified with a couple of holes, a notch, and a chamfered edge.

Another picture of the weldment block sitting in the in the trim bracket.

Once the block was modified, I used the holes in the block to match-drill the block to the bracket.

The trim weldment block is match drilled to the bracket and temporarily held in place with bolts.

Then, with the block in place, I was able to locate and drill the rivet holes for attaching nutplates to the bracket.

At this stage, the bracket was ready except for final prep, so I dimpled, countersunk, and primed as needed.

As my primer dried on the bracket, I started working on modifying the trim weldment.  The long arm of the weldment has to be bent approximately 10 degrees, and the tube section has to be cut down so that it goes through the plastic block far enough to insert a cotter pin, but not so far that it hits the aluminum bracket.

The trim weldment tube has to be shortened, and the long arm has to be bent slightly.

The trim weldment and block temporarily assembled.

Once the weldment was finished and the primer had dried, I started final assembly.  Right now, the weldment seems tight in the block.  I can rotate without too much exertion, but I don’t know if the trim servo will be able to  move it.  However, this is as far as I’m going to go on this right now since the control sticks really need to be rigged before I install the servo and remaining trim hardware.

The trim bracket fully assembled.

While many builders look forward to the warmer Summer weather for working on their airplane projects, it is the opposite for me in South Texas.    The daily high temperature has consistently been hitting the low 90s, and we’ve already had one day the hit 100.  Needless to say, the warm weather is not conducive to working in the garage!  With this in mind, it has been a couple of weeks since I last worked on the plane, and my work sessions will likely remain infrequent until the Fall.

I managed to sweat over the plane (literally) for a couple of hours today.  My goal was to get the crotch strap brackets fitted to the seat ribs.  The crotch strap brackets consist of two aluminum parts that are attached between two seat ribs.  The tang of the crotch strap is wedged between, and bolted to, these two pieces.  I figured now would be the time to get this done since the center fuselage is sitting on a table and the ribs are easily accessible.

Working on the left side first, I marked the location for the forward bracket.  Because of the limited access, and having multiple flanges in the way, figuring a way to clamp the bracket in place wasn’t easy.  Fortunately, the brackets are wedge in so tightly between the ribs that clamping isn’t really necessary for the first couple of holes.  Once I was happy with the location, I used by angle drill attachment to match-drill the bracket to the seat rib.

Trying to fit the first bracket in place was challenging. Holding it in placed for drilling was just as difficult.

The forward side of the forward bracket. It wasn’t simple, but I got it drilled with my angle drill.

After the forward bracket was drilled, I repeated the process for the aft bracket.  Since I’m planning on using Crow harnesses, I just used the 1/8″ spacing called for in the plans (the plans are for Van’s harnesses, but the tang on the Crow’s are the same width).  If you are reading this and planning to use Hooker Harnesses, I believe you have to adjust the width between the two brackets.  To make sure the spacing was correct, I used a couple of pieces of 1/8″ thick scrap between the two brackets and clamped everything together.

I used a couple of pieces 1/8″ thick aluminum scrap as spacers while I drilled the aft bracket to the ribs.

Once both sides of the bracket were drilled to the seat ribs, I temporarily installed the floor panel using a few screws.  I then used the holes in the floor panel to match-drill the holes for the upper flanges on the brackets.  The whole process was then repeated on the right side.

Once drilled to the ribs, I installed the floor and used it to match drill the crotch bracket flanges. The camera makes the brackets look crooked in the opening…they’re not.

Both crotch strap brackets drilled to seat ribs!

Finally, I started working on the aileron trim bracket.  I got as far as cutting the bracket to the correct length before deciding to go inside and cool off.  The rest of the aileron trim install looks relatively straight-forward.

Back to work on the center fuselage skeleton today….

The first thing I did was fit and drill the F-623A attach straps.  These are a little more awkward to drill then I thought they would be mainly due to their small size.  I had to clamp them in place and then drill from below.  I started with the right forward strap, and managed to screw it up…twice!  The first one moved as I was drilling, leaving to little edge distance.  I remade it and tried again.  The second one wasn’t positioned correctly right from the start, and I knew I wouldn’t have enough edge distance as soon as I drilled the first hole.  The third time was the charm.  I remade the strap once again, positioned and drilled it, and called it good.  This first strap was the only one that gave me issues.  All of the others went on fine, and my modified rear straps were perfect.

The F-623A forward attach straps were trickier than I thought they would be to install. I had to remake this one twice before getting one with proper edge distance.

My "revised" F-623A aft attach straps worked well, and I should have descent edge distance on the aft hole when it is drilled.

Next, I finished drilling the remaining center section holes to full size.  The only holes that hadn’t been drilled yet were the holes connecting the ribs to the bulkheads.

With all the holes drilled, it was finally time to re-mate the halves of the F-704 bulkhead.   Using the spacers I made earlier, I lined up the halves and inserted a few bolts.  I then clecoed the bottom edge of the forward F-704 to the bottom skin.  The holes were all in perfect alignment, which is always a pleasant surprise!

Next, I clecoed on the F-704H side doublers.  Again, the fit was perfect, so I guess my earlier work on the F-704 bulkhead was acceptable.

After installing the front half of the F-704 bulkhead, the F-704H side doubles were clecoed. The fit was great!

Last, I final-drilled all the holes in the F-704 bulkhead, F-704H side doublers, and the center section bottom skin.

The complete center section skeleton. I was surprised how well the F-704 halves went back together!

At this point, the plans say to take everything apart for deburring/dimpling, but I think I’ll try to install the crotch strap brackets now while access to the seat ribs is less limited.  The plans never really say when to install the crotch strap brackets, so I hope my time is OK.

For some reason, I was motivated to work on the plane after work today.  With only a couple of hours available, I figured I would have enough time to finish the F-623 corner ribs.

As with some other parts in the kit, the F-623 corner ribs are a relic from another kit.  In this case, the RV-6.  They are not pre-punched, they aren’t the right size and need to be trimmed, and the instructions/plans are very vague!  To me, it seems that these ribs could have easily been redesigned, but I guess it’s just one of those areas where the builder has to “fabricate.”

To trim the ribs to size, I simply laid them in position and marked where to trim.  I then cut the ends of the ribs off with my bandsaw.  Quite a bit has to be trimmed.  I removed about 3/4″ from the forward end and 1/2″ from the aft.

Once trimmed, I did a little fluting and straightening, and then clamped the rib to the bottom skin.  Once positioned, I then back-drilled the rib using the holes in the bottom skin as a guide.

After trimming the ends of the rib, I clamped it in place and match-drilled the holes through the skin.

The corner ribs are relics from the RV-6 kits, and quite a bit needs to be trimmed off each end. This picture shows the forward ends...one trimmed, one not.

Trimming the aft end.

The F-623 corner ribs clecoed in place.

After both ribs were drilled, I worked on making the four, F-623A attach straps.  These small strips of aluminum link the corner ribs to the rest of the center fuselage skeleton.  After finding a piece of .032 aluminum sheet, I measured out and cut the straps per plans.  However, after checking the straps on the ribs, I knew that some modifications would need to be made.

Like many other builders, I found that the aft attach strap was too narrow on the aft end, and proper edge distance on the aft-most hole would be nearly impossible to achieve.  In an attempt to make it a little better, I remade the aft straps with the aft end a little wider.  In addition to this, the forward straps will probably need to be narrowed down a bit.

Four attach straps are fabricated for the corner rib. I ended up widening the aft portion of the aft straps from the dimensions in the plans to give more edge distance. The bottom part on the right is per plans, while the two above it are widened.

The first thing I did today was recruit Amber to help me flip the center fuselage skeleton over and help lower the sawhorses holding my table top.  The center fuselage skeleton isn’t that heavy, but it is awkward due to the size, and it is wobbly without the skin attached to hold things tight.  Within a couple of minutes, we had the skeleton flipped and the table lowered to a height that would make working on the bottom skin more manageable.  Another 6 inches lower would have been nice, but the sawhorses were as low as they would go.

The center section skeleton is flipped upside-down in order to cleco on the bottom skin.

Another view of the bottom of the center section skeleton.

Next, I dug out the center fuselage bottom skin.  I have the remaining fuselage skins laying on the garage floor under the fuselage parts crate and the wing cradle.  Wouldn’t you know it, the skin I needed today was on the very bottom.  Once the skin was out, I tossed it on top of the center fuselage skeleton and started clecoing.  I clecoed every other hole in the structure because I wanted to make sure everything was tight for drilling.  For the most part, this was easy, but there were some alignment issues along the F-705 bulkhead.  However, nothing an awl couldn’t fix!

Once clecoed, I drilled most of the holes in the bottom skin to full size.  This took quite a bit of time since there were a lot of clecoes to move around.

The center section bottom skin clecoed and drilled.

After final drilling the areas of the bottom skin that could be final drilled now, I recruited Amber to, once again, help me flip the structure back over.  I wanted to start working on the F-623 corner ribs, but I was a bit confused on how to fit them.  The plans are very vague here as well.  Time for some research.

The center section back in its upright position. Now I have to fit the corner ribs.

A front view of the center section.

Before calling it a day, I decided to draw center-lines on the bottom flanges of the F-715 seat ribs and clamp them to the center fuselage structure.  These ribs are not pre-punched, and they won’t get drilled until a bit later.  They’ll also need some creative fluting since they are actually curved in the final structure instead of straight like the other seat ribs.

I decided to center-line the bottom flange of the F-715 ribs now...they won't be drilled for a while though.

Generally, I follow the plans fairly close, but the next step gave me some pause.  The instructions said to run an 8-32 tap through nutplates on seat ribs so that the screws holding on the floor panels would be easier to install.  Normally, running a tap through a nutplate would be a bad idea.  The whole point of a nutplate is to be tight, in order to lock in the screw.  However, I guess it isn’t a big deal if the floor screws come a little loose on occasion.  Not wanting to doubt Van’s wisdom, I went to Home Depot to get an 8-32 tap, and then ran it through all the nutplates in the tops of the seat ribs.

Per the plans, I ran an 8-32 tap through the nutplates in the seat ribs. Normally, I wouldn't do this, but it isn't a big deal if the screws holding the seat floor in place come a little loose.

Next, I decided to tackle the remainder of the center fuselage rib deburring that needed to be done.  All I had left were the two F-715 seat ribs, as well as all six of the baggage area ribs.  Between the two Scotchbrite wheels and some emery cloth, edge deburring has become a fairly quick process for me.

With the edge deburring done on all of the ribs, I started assembling the center fuselage skeleton.  First, the seat ribs were clecoed to the aft side of the aft half of the F-704 center section bulkhead.  Once these ribs were clecoed, I realized that my workbench was not going to be a good place for assembling the rest of the center fuselage.  Some garage re-organization would have to be next on my to-do list.

After clecoing the seat ribs to the aft half of the F-704 bulkhead, I realized I was going to need a bigger table. Time to rearrange the garage again!

I had to move the aft fuselage off of the sawhorses to the garage floor.  Fortunately, the aft fuselage is much lighter than it looks, so I could move this to the floor myself.  With my sawhorses freed-up, I reinstalled the table top I had made for them.  Presto-chango…I now had a nice, big table for assembling the center fuselage!

With the center fuselage now in a more workable position, I added the F-705 bulkhead to the aft end of the seat ribs.  Then, the baggage ribs were clecoed in place.  Finally, I inserted the F-916C spacers, which I had made days ago, into the proper locations.

Next up, the center section floor has to be clecoed to the skeleton.  However, I’m first going to need help flipping over the center fuselage skeleton and lowering the sawhorses to set the table at a more workable height.

The center fuselage skeleton clecoed together for the first time. This view is forward looking aft.

Center fuselage skeleton...aft looking forward.

Center fuselage skeleton side view.

This work session started with riveting together the F-716B assemblies.  Once the F-716Bs were riveted, I used some #8 screws to attach them back onto the seat ribs.

The completed F-716B assemblies.

A completed F-716B assembly installed on the seat rib.

With the seat rib modifications complete, I went back to riveting the aft fuselage.  There were several points where I wanted to call it a day, but I stuck to it and finally finished.  As usual, the aft-most section gave me the most problems.  Bucking bar access was challenging at times, and I had to drill out and replace a few rivets.  Now, the aft fuselage is riveted up to the level of the upper J-channel.  The upper portion of the aft fuselage will remain unriveted for a while so that the skin can be pulled back far enough to allow the longerons to be inserted.

The riveting on the aft fuse is done (for now). The instructions say to only rivet up to the top j-channel, so that's what I did.

The aft-most section of the aft fuselage. Despite my battles with this section, it came together nicely!

Technically, this is aft fuselage riveting day 7, but I spent more time working on the seat ribs than I did riveting the aft fuselage.  As far as my riveting progress goes, both sides of the aft fuselage are complete to the F-710 bulkhead.  All that remains are the rivets in the F-779 bottom skin and the side skin to F-711/712 bulkhead rivets.

After doing some riveting, I went back to work on the seat ribs.  I still had a little deburring/prep work to do, so I completed that first.  There are a lot of notes on the plans that tell you what needs to be done, while the instructions just say to prep two ribs this way, two that way, etc.  So, careful attention has to be paid to the plans (as always).  Among the things that had to be done were enlarging a tooling hole on each rib to 5/8″ for a snap bushing and final drilling platenut attachment points.

Once the prep work was done, I riveted the platenuts to all of the ribs.  I also primed the parts for the F-716B rib access assemblies, so these still need to have the platenuts riveted on and the assemblies riveted together.  I may or may not prime the entire seat ribs as well.  However, I haven’t made that decision yet, as I’ll wait until they are closer to final assembly before priming.

All the nutplates are installed in the seat ribs, and I also enlarged one tooling hole on each rib for a snap bushing.

I decided to prime the seat rib access plates...I'll probably prime the ribs too, since they aren't alclad.