Center Section Spar: Part II

With the aft face shear web layup cured, it was time for spar caps. (Yay. Spar caps.)

Some surplus plywood was cut down to strips to shore up the free standing side of the spar cap and help create a trough.

See. It's a trough. A very intimidating trough that we filled with resin and glass fibers.

Ced took the time to measure and trim all the plies of glass we were to layup. I almost wish he had not simply because it was a visual representation of all the work we were about to do.

Despite the pile of dry fibers staring us down, we began work.

I'll spare you the details. Just imagine us mixing a lot of resin and wetting out fibers.

Once complete we did a bit of a happy dance and fell over from exhaustion.

But not before documenting the leftover strings from the glass tape.

Once that spar cap cured, we flipped the spar box over and began the process again.

After that layup cured, the ends were trimmed. Check out those thick spar caps!

The forward face corners were rounded in preparation of receiving a shear web layup.

Bits of spruce were spliced into the spar box for the shoulder harness mount points.

But before we could get to the forward face shear web layup, we had to put yet another four plies of UNI on the aft face.

Composite work knows no fashion rules.

Once that layup cured it was time for hardpoint reinforcements.

The aluminum plates were prepped and floxed in place.

Three plies of UNI were placed. . .

and a final swath of BID laid over the whole thing.

With all of those bits in place, the box was flipped over to expose the forward face, which we cut big access holes in.

Two plies of BID was placed over the whole thing followed by a layer of peel ply.

Once that layup cured, the end bulkheads received a layer of BID, which was trimmed after cure.

Access holes were drilled in the ends and the whole spar was pegged as complete.

The next steps with this structure will be the install, but there is quite a bit of work on the fuselage before we mount this beast.

Center Section Spar: Part I

While working on the nose of the Cozy last summer, we also built the center section box spar. The plans describe this structure as "the heart of your wing," so a lot of care was taken while putting it together.

To start out, a jig must be built. Ced had his NC machine cut out all the pieces of the jig, because, well, why not?

With all the pieces free of the MDF sheet, they were assembled with bondo.

This was the first labor-intensive step to a very, very long process, so bear with me.

PVC foam is laid down on the bottom of the template to form the aft face of the spar box.

The "sides" were created from urethane foam. . .

and temporary jigging was set in place to hold the free standing side in place. . .

while the urethane foam was bonded to the PVC foam.

Once the micro cured, the bulkhead positions were laid out.

With locations marked, one ply of BID was laid up in the interior of the box.

Micro slurry applied.

BID portion in place.

Once the interior BID layup cured, the bulkheads were installed.

Aluminum hardpoints were manufactured and installed with several plies of BID tape.

Here's an image to get a feel for the small working space of these layups. They were a little tedious.

Once all of those layups cured, the box could be removed from the jig and shown off.

This image lets you get a feel for the length of the spar. Oi.

The BID surpassing the edges of the foam was trimmed and the top surface was prepped for closeout. Also, holes were punched through the bulkheads to allow airflow.

Panels of PVC foam were glassed on one side ahead of time for the closeout.

Micro was piped along the forward face of the box. . .

and the panels were laid down in sections.

Once the forward face panels cured, the whole thing was flipped over to prepare the sides for hardpoints and spar caps.

Around this point Ced's parents had come to visit. This was great news for us because we took full advantage of the extra help. I also think it was good to share some of the steps it takes to build an airplane. It is a laborious task which is difficult to fully describe with just words and photos. (This might be turning into a plug for recruiting more help. *ahem*)

Ced and his dad, Mr. T, spent some time sanding down the urethane sides to create troughs for spar caps.

Once one trough was sanded down, the whole thing was flipped over and the sanding process started on the other side.

With the troughs carved it was time to install a few more aluminum hardpoints.

While Ced rounded the edges of the PVC foam, Mr. T worked on rounding edges of each of the aluminum bits.

With everything fit checked, the aluminum tabs were floxed into placed.

Now it was time for the aft face shear web layup.

The entire length of the spar was covered in a micro slurry to fill the foam pores.

Ced and I demonstrated applying the first section of the first ply of UNI. . .

and Ced and Mr. T finished laying down the rest of the UNI (four layers across the whole spar). It was nice having the help because this large layup went a bit quicker than expected.

Inspection!

A final layer of peel ply and the first shear web of the spar was complete.

Whoo!