The Long EZ Build: Prep for top skin glassing and hinge inserts

Some prep work was required before I could glass the canard's top spar cap and skin. Funny, the plans don't really mention this step - just a friendly reminder as to why things take so much longer than originally planned.

I started out by sanding the trailing edge straight as an arrow.

I verified straightness by pulling a tight string. I learned that a good way to do this is to not have the string touch the material you are testing for straightness. Instead, you want to place it about 1/16" or 1/8" offset and check that the spacing is consistent along the entire span. Otherwise, if the string touches the material and your material happens to be convex, it will appear to be straight when in fact it is not.

I then cut 6 jigs using scrap 1" melamine board I had leftover. I had to incorporate an "L" design since the pipe I am using to stabilize the trailing edge is only 1" diameter...

Here I am test fitting all the jigs.. notice the pipe running along the trailing edge..

I then used my digital level (a.k.a, my old iPhone) to measure twist... this is the left outboard tip...

And the right outboard tip.. a difference of 0.1 degree... not bad! The middle was also checked.

After I was happy with the leveling, I used bondo to hold the pipe to the trailing edge.. and blobs to hold the jigs onto the canard's bottom surface and pipe..

Here is a better shot showing the trailing edge of the canard... notice the blob of bondo holding the pipe to the canard...

After the Bondo was fully cured, I began to cut all the hot glue gun blobs that were holding the canard to the jig below...

A few minutes later, the entire canard, pipe and new jig assembly was off the old jig...

I then removed the old jigs, flipped the canard over and placed it onto the 2x4 extensions on the bench...

A lot of work was ahead of me. I had to clean up the micro that had dripped way back when I bonded the tip ends to the canard, I had to remove the gray tape that protected the leading edge while glassing the bottom skin, the shear web needed some sanding and the 'fish tail' trailing edge needed trimming...

Oh, and the shear web edges needed cleaning up too!

I removed the duct tape from the leading edge, and began trimming the trialing edge...

Hiding under the trailing edge was the peel ply that the plans had instructed us to install prior to glassing the bottom skin...

In my mind, I was expecting to use a blade to get a little bit of the peel ply and then simply peel it off in one smooth pull. Buahahahahaha!!! There was NOTHING simple about this process. It took me about an hour just to get an inch!!

Looking downstream, I thought, "there has GOT to be a better way!"

I wish I could tell you that I found a better way - but unfortunately, after trying 2134598723459812 different things, I found a sharp spatula to be the best way... slow? Yes. But at least it got the job done.

One inch at a time, I slowly hacked away that nasty peel ply! I'm not sure why it was so difficult to pull the peel ply. Perhaps it was because the peel ply got covered in micro slurry when the foam was prepped for the bottom skin.

With that completed, I moved on to cleaning up the leading edge. I sanded the glass to minimize the lip thickness as indicated in the plans. This makes sure that the overlap of the top skin onto the bottom skin is nice and smooth, without a jagged step.

Then it was time to clean up the shear web edges. This was leftover masking tape that was used to protest the foam while glassing the shear web.

Then I had to clean up excess micro that had run off onto the shear web when I had bonded the leading edge onto the shear web a while back.

Ok then, shear web looking good!

Now I had to install the high density foam inserts. These are required in order to bond the elevator hinge brackets later on. I ordered some H100 PVC Divinycell foam 1" x 6" x 10" and used the contour checker as my template...

The plans say they should be about 2.7" long... so I made a mark 2.7" from the trailing edge...

And traced out as many as I could fit onto the 6"x10" foam panel... I was able to trace out 11.. but I only needed 7 - always good to have extras just in case...

Using my band saw, I cut them out and sanded the round curves smooth...

I then measured and marked the 7 buttline locations of all inserts... the plans show where they need to go.

Using my dremel, I began milling away...

I used a metal file to help me square the corners...

And to scrape the bottom glass clean...

Taaa-daaaa! One down... 6 to go!

About an hour later, I had all 7 inserts in place...

To bond the inserts in place, I slurried all the surfaces and pooled some into the pocket...

I also micro'd the piece...

And inserted it into its happy home...

The next day, I sanded the inserts flush with the rest of the airfoil shape...

As I started to think I was just about finished with the top skin prep work, my attention was drawn to the trailing edge...

Removing that trailing edge peel ply had me remove more trailing edge foam than I would have liked... notice the size of the groove here!

As I was removing the foam to get all the peel ply off, I remember thinking I was going to use micro to fill this void... but there was no way I was going to use that much micro, full span! Plus, look at the shape. Notice how it will require an 'S' curve in order for the top skin to make a good glass-to-glass bond with the bottom skin trailing edge. Even if I were to use dry micro, I would have to go back and sand all this micro off the trailing edge to get to the glass.

Liquid foam anybody? At this point I was a bit frustrated... I was already a few weeks behind schedule and the thought of having to stand down was a bit irritating. But I told those voices in my head to shut up and do it right! So I placed an order for X-30 liquid foam and waited anxiously for it to arrive.

If you have never used X30 liquid foam before, it is really easy to use! Here is a link explaining how it works and a useful how-to video: X30 link.

Before getting started, I used tape to protect the trailing edge glass.

I then mixed up some X30 liquid foam and poured it into the trailing edge groove. It expands 30 times its original volume, so a little goes a long way! Also, the expansion takes less than 3 minutes, so I made sure to mix small amounts at a time.. probably took me 4 pours to complete the whole span of the trailing edge.

This stuff is amazing! And it cures fast! In 15 minutes, everything was cured and ready to carve.

I used a knife to get rid of the bulky stuff first...

I then switched to sanding it by hand...

Wow! I'm sure glad I went down this path instead of trying to fill that huge groove with micro! The trailing edge was now fully restored to its true airfoil shape!

Here's the proof!

Ok, now to get that clean glass-to-glass bond... I removed the tape, and vuala!

The CP's state that a minimum of 0.45" glass-to-glass is required on the canard's trailing edge. Since this is the absolute minimum, I wanted to make sure I had 0.6". So I built a special tool out of a popsicle stick..