Center section spar install

I waited until both my wings were completed before installing the spar. Also, I had to wait until my engine mount arrived since the engine mount bolts on to the aluminum extrusions that mount the spar to the fuselage. The problem was that there are various engine mounts depending on the engine model... and since I am far away from purchasing my engine, I decided to go with the most common - dynafocal type 1 - for a Lycoming O-320/360.

Any who, back to the spar install. I started out by cutting the fuselage sides...

Swiss cheese!

Since I had already installed my firewall, I had to slide the spar through...

Notice how I had to cut about an inch off the top of the rear pax seat.. this will later be patched. Pay no attention to the weird firewall outline shape... I had purposely left the firewall 2" bigger than it needs to be so I can trim it down to size when it comes time to do the canopy.

Woooo-hoooo!!!

Here's a better shot of the the firewall that will be trimmed down sometime in the future...

I then focused my attention to cutting out the "L" shaped holes to pass the aluminum extrusions. Here's the top left...

Bottom left...

I drilled the corners...

I then used the multitool to cut the "L" out...

Presto!

I then cleaned around the holes... I used metal files and sand paper..

It was now time to level and shim the spar. First I made sure the airplane was level (both roll and pitch). I then clamped levels to the wing attach pucks...

I then shimmed the spar level...

I clamped a straight square tube to the F28 bulkhead and measured the distance from it to the spar outboard tips... this helped me shim the spar's "yaw" to make sure it will be parallel with the canard and perpendicular to the fuselage.

After making sure the spar was properly leveled, correct pitch and yaw, it was time to lock it in place. This is done by applying 4" 2-ply BID tape all around the outside, where the spar and fuselage mate.

I prepped the surfaces...

Painted plain epoxy...

And applied the 2 ply BID tape to the outside surfaces...



I then spent a few days making the aluminum extrusions. I should note that I used 1.5"x1" "L" extrusions (an increase of 0.5" in the vertical web). The plans say to go with 1"x1" but since I plan on installing a heavier engine, the extrusions need a little bit more meat. Also, disregard the MS21042-L nut... that's just what I had laying around at the time. I later replaced them with standard MS21042.

The left side of the spar sits up onto the longeron...

On the right side, there was a gap since I had to level the spar..

I cut a filler piece out of spruce, and floxed it in just prior to installing the 10-ply pads...

I then made the spruce wedges. These align the aluminum extrusions parallel (since the longerons taper in towards the firewall).



I didn't take pictures of the process since there was a lot going on... but to install the top aluminum extrusions, I cut a piece of 2x1 to press the extrusions out. Under the extrusions, I floxed the spruce wedges in place, applied the first 2 plies of BID that go over the longerons, followed by 8 plies of BID (10 total). I then placed weights on top of the 2x1 to press the extrusions down.

On the backside, I cut another 2x1 to the same size as my engine mount.

I could have used the engine mount to clamp everything in place, but I found this was easier to handle...

After cure, I removed the 2x1's and trimmed everything up...

Top view showing how the spruce wedge aligns the extrusion parallel with fuselage centerline.

I then drilled the extrusions per plans...

Made sure the holes went through the hard-points embedded inside the spar...

Here is Haley (USF mechanical engineering graduate) helping me with the build.. I recently contacted USF and asked if any of their students would be interested in joining the airplane build.. they are amazing.. very motivated and smart individuals looking to get experience with anything aerospace!

Installing the bolts...

The horizontal bolts are a bit tricky and required the use of a flexible drill extension...

Since the drill can't get into the tight space..

I then cut out a section of the fiberglass...

Removed the foam and cleaned it up for the washer and nut...

For the bottom extrusions, I clamped the engine mount on...

This allowed me to install the bottom extrusions exactly where they needed to be...

Prepped the areas for bonding..

I then cut the spruce wedges to size... notice how I made sure the wedges created the perfect spacing to place the extrusion right over the hard point embedded inside the spar...

Here I am dry fitting  everything with the 10 ply BID pad....

I cut a 2x1 piece to hold the extrusions out towards the wedges...

With everything prepped, it was go time!

Started out by filling all the voids with flox...

I then floxed in the wedges and applied the 10 ply BID pads... the first 2 plies were a bit bigger and extended fwd covering the entire wedge. I then brought the aluminum extrusion in from the rear of the firewwall and clamped it to the engine mount to hold it in place...

I repeated this for the other side and then placed a stool under the "hell hole"... I cut another two 2x1 pieces to force the extrusions up...

Here is a shot of the two 2x1 pieces holding the horizontal 2x1 piece up, forcing the extrusions up.. the horizontal 2x1 also forces the extrusions out.

After cure, I removed the 2x1's and cleaned everything up...

Drilled out all the holes...

And installed the bolts. Notice how I had to trim some of the 1.5" extrusions since the landing gear bracket is in the way.

And there you have it! The center section spar is officially installed!

I should note that I added a top piece to the bottom extrusions (aft of the firewall) to make up for the fact that CS73 is not needed (since my master cylinders are located in the front of the airplane). While studying the plans on page 15-2, I questioned whether CS73 not only acts as an anchor point for rear mounted brake cylinders, but also helps strengthen the aluminum extrusion where the engine mount bolts onto. So even though I do not need CS73, I still want to have that portion of it there.

I took this picture before installing the aft bolts... but here is a good top view...

Next up, installing the wings onto the spar!