Then it was time to add fiberglass to the transitions between the skirt and the canopy. I used two layers of fiberglass. First a 2 inch layer, and then a 3inch later to make for gentle transitions.I used the same technique as before however this time at the advice of Mike I put a skim coat of epoxy on the skirt/ canopy before laying the glass. This should help ensure proper adhesion.
Here are a few photos of the results of the applied glass.
I used 4 separate strips. One across the back. One on each side, and one on the front. The front required a few cuts to go around the strong curve.
After the fiberglass cured, it was time to turn my attention to making everything flush and smooth. The exterior is very important as the eventual base clear coat will show any flaws. The interior of the canopy will have a semi-gloss / flattened or even flat paint that is more forgiving to flaws.
I started by doing a skim coat of micro with a hotel key card to fill voids along the edges of the fiberglass and at the transition points.
Of course this was followed by lots of sanding.
At this point I decided to try a new technique. Brushing on the epoxy had worked very well previously, so I figured why not try brushing on micro? Yes its thicker, but if you mix it right you can get the right amount of flow. I brushed the micro on everywhere to get a very even coat.
Here you can see it the next day. A few runs here and there, but pretty good.
As I sanded it I found that I am a huge fan of the brushing on micro technique. Here’s why. By using a mix with a little more flow, and brushing it everywhere it does some degree of self leveling. Perhaps more importantly since the micro is covering everything, when you sand, you are sanding something of the same density. Its easy to run into problems when you have something hard, say flox, on something softer, say micro. In this example, micro will sand way easier and its difficult to get a flat smooth transition as the micro sands away so much easier and quicker than the flox. By brushing on the micro everywhere you get great coverage, some self-leveling / hole filling. The results on the first run were fantastic.
I repeated the process of applying micro with a brush a couple more times. Each time I used less micro in the mixture (less viscous – more runny) to fine tune the transitions.
On the last application I applied micro by brush to the entire exterior of the skirt from top to bottom and then sanded. The results are spectacular. I’m extremely happy with the exterior of the canopy.
This of course brings me to the interior of the canopy which was a bit of a nightmare. I made two mistakes here that compounded one another and added a non-trivial amount of work. I place the tape too close to the skirt – basically exactly in line with it, and I did a poor job of cleaning the adhesive fillets on the inside. As a result the tape was very very difficult to remove in some places. I spent hours picking, pulling, sanding, and finagling the interior fillet to get in clean. I highly recommend you leave about 1/8″ between the skirt and your canopy tape. I would also use three layers. Two layers of electrical tape for sanding, and one layer of painters tape. Remove the painters tape immediately upon application of the adhesive to make cleaner lines.
After cleaning up the tape and interior, I repaired the fillet with a two step process. One I put a flox fillet all the way around. I followed this up with sanding, and an application of micro for the small flaws.
The pictures don’t do it much justice.
While these things were curing I worked on the instrument panel cover. I filleted the inside of the canopy transition arms (for lack of a better term).
I set everything in place after the fillets were dry and began marking for final drilling of the arms as well as creating a new transition filler on the right side. I found the hinge was a bit longer than I needed so I shortened that appropriately. The right arm holds the hinge pin in place.
Here you can see there is a slight gap between the arms and the canopy rails. I could fill this with flox, but I think I will likely use weather stripping. I don’t plan to prime or paint this part until after the plane is flying, so I can make adjustments to airflow and water sealing with better experience and actual testing.
I also trimmed the length (ironic since I previously added length) of the right arm. I had little choice due to the position of the aft screw.
I then taped everything up to add more flox to the fill the large gap that is present on the forward side of the canopy skirt area (by virtue of the hinge and geometry this gap is unavoidable)
At the same time I added more micro to the skirt interior.
Here is the right gap filled with flox.
Here it is after the flox cured and I removed the canopy.
I did a lot of sanding and clean up to this, but failed to take a final photo.