38-31: Canopy Fibreglass Fairing - Round 4 - Initial Sanding to Shape / Refining the Edge with Micro

First up - peeling off the Peel Ply

Sanding (the start of a journey)

Once the peel ply was off, the surface left was ready to sand. There was no need to wash off any amine blush etc, as this was all taken care of with the peel ply. The plans have you use a large wooden sanding block, with a 4" radius on the end. I was given one of these made by a builder whom i purchased tools from initially. It had been sitting waiting for it's time in the sun - but i found that it was way too wide - it was sanding well onto the top tape, and i was concerned with going through to the canopy. Instead, i made up a cork sanding block with a 4" radius - this worked a lot better. 

This was the finish after the peel ply was removed.

I was given this block by the seller of a tool kit i purchased when i initially started.

4" radius

The block was just too wide - it was really sanding into the tapes, and i was concerned i would have a brain fart and sand through to the canopy.

This cork block was made up instead. This worked a lot better for me.

The centre curved area was sanded down until the block was touching the entire curved surface and the first layer of tape was exposed at it's edge along the top. I found that the curved block worked well for almost all of the surface, and i was able to twist it as i got to the corners, where the curve transitioned to flat on the sides. All the shape sanding was done dry, using 40 grit. I added a piece of white tape, over the original tape layers to provide a little bit more protection as i sanded closer to the finished contour.

The sanding motion which worked for me, can be illustrated in the video below:

The sides were sanded using the flat side of the same block. This was the surface once sanding to shape was complete:

Sanding was done with the curved block, until i could just see the edge of the top layer of tape being exposed.

This is the flat side of the canopy fairing where it will transition into the canopy sides.

The fairing came out to a nice 4" radius at least!

The shape is complete, with the tape edge exposed at the top. The white tape was laid over the top edge, to protect it against inadvertent extra sanding.

This is the side curve where it begins to transition to flat.

Sanding Oopsie...

When sanding, the idea is that you stop when you get down to the black surface. In practice, this was harder than it sounded! On the left side of the canopy, I thought the shape was looking very good, then noticed a small irregularity in the look of the fibreglass. Looking closely, i realised i had sanded right through the fibreglass to the canopy itself. This was obvious when you looked inside. 

If you look carefully here, you can see where i sanded through the fibreglass and exposed some of the canopy. 

It is a lot more obvious from the inside!

In addition to sanding through to the canopy, i noticed that the edge of the fairing was not very nice. When doing the initial tinted cloth layup, this cloth was pushed up against the tape. Unfortunately it didn't look very good. 

This is what the edge of the fairing looked like. 

Fixing the Oopsie!

The great thing about fibreglass, is it is so easily repaired! The repair in this case, was a small bit of fibreglass tinted black applied to the surface. In addition, i removed all the tape and applied 3 additional layers of tape approximately 1/32" away from the original edge of the fairing. This exposed a little more of the canopy glass, which was now unscuffed, so this was rescuffed using 80 grit and scotchbrite and cleaned. The top layer of tape was then removed, leaving 2 layers of fresh tape for the next step.

Fortunately, i keep good notes, so write down the exact percentage of pigment i used to dye my resin. I was able to mix up some more dyed resin, then wet out a small patch of fibreglass sandwich, in the same manner i did at the start. I painted some dyed resin over the whole fairing. The fibreglass patch was then applied to cover the area where i had sanded through. 

The remaining resin was mixed with microballons to a thick consistency, and was applied along the whole fairing. The aim of this was to give a much better edge to the fairing, cover the transition of the fibreglass patch to the rest of the fairing, as well as fill any exposed voids or pinholes. 

The original tape was removed, and a new tape laid down about 1/32 away from the original fairing, to try and give a better edge.

This was the paper template for the fibreglass patch.

Black resin was brushed onto the whole surface before the patch went on.

The sandwich was applied, then the whole fairing was coated in a dyed microbaloon mix.

Next up is to let this cure, and sand most of it off. Repeat - ad infinitum.