Canopy Part 2 ...
This is the Sikaflex glue I got fom a local distributor:
Sika Cleaner 205
Sikaflex 295 UV
Sika primers for different materials to be bonded
The Sika primer 209 N is used on plexi.
The Sika primer 206 G+P is a more universal primer for paints, composites, aluminum and steel.
|Bernard came over to give me a hand and add some suggestions during the process.|
First the area to be glued needs some light scuffing with Scotchbrite and then thoroughly cleaned with Sika Cleaner 205. After cleaning wait 10 minutes before priming.
You can look up all technical data on the Sika product line via their website.
|Then the Sika primer 209 N is applied with a small brush. It starts to dry pretty quickly. You have to respect about 30 minutes drying time before applying the glue.|
|Bernard applied the 206 G+P primer while I was priming the plexi.|
|When everything was ready to glue the canopy to the frame, the spacers were put into place.|
|Canopy was fitted and clamped for the last time.|
|We applied glue from the top and from the bottom to get a nice bead of glue between the frame tubing and the plexi. Excess glue was removed using a popstacle stick cut into shape. After curing (about 2 days for 6mm of glue thickness at 23°C) the spacers and clamps will be removed and we will finish everything with a final coat of glue, just for the aesthetics.|
|A more closer look on the structural gluing.|
Afterwards we went to Bernards' shop, less than two miles away, to glue his canopy fairing on his RV-7A.
|Bernard is doing a great job on his project and hopes to be flying by the end of 2010.|
|He made this nice custom centerconsole, housing throttle quadrant, Andair fuel selector, and several indicator lights. It will be covered in nice leather.|
|Excess glue is removed using a squeege or sortoff, finally the tape is removed.|
I've had the first structural glue drying for a about four days, just to be sure everything cured 100%. Then I cleaned and applied primer again on all surfaces to be finished, just to 'reactivate' the cured glue. All edges were finished with glue and a small sqeege. After about one hour I removed the tape.
This is the result, not 100% perfect in all areas but I'm very pleased with the result! Once the skirts are installed I will spray paint the interior. A good feature of Sikaflex is that it can be painted.
|A more closer view on the fillet.|
|Time to fit the skirts. The skirts will be glued as well. I spent some time thinking about how to keep them close and tight to the canopy/frame assembly. I found there was no way around using clecos. So I made a small "pilot drill / frame centering" tool. The wood block touches the edge of the frame tubing. Tubing is 5/8" diameter and 1/2" on the aft part of the frame. The pilot hole was positioned so that the drill bit will center exactly on the tubing. I first drilled the plexi with #30 plexidrill till it touched the metal (#30 was the plexi drill size I had available, #40 would have worked as well). I drilled holes every 4" starting at the frame bow. Then I carefully drilled the tubing using a regular #30 drill bit. This method proved to work very well.|
|I taped some tape strips above the drilled holes, drew a centerline and marked at 4" above the hole. This way, when the skirt is positioned and taped in place I can relocate the already excisting hole in the canopy.|
|I started with the righthand skirt and fortunately the fit was pretty good. Altough Vans tells you to trim about 1/4" outside the scribe line, I initially left most of the fiberglass. It leaves a bit more room for finding the right fit all along the canopy. Then I timmed in a couple of iterations. After I got the best fit possible I taped it in place and drilled the first hole.|
|From there on I drilled the aft portion, one hole at a time and clecoed as I got going.|
|This show the hole finding method in more detail. It's very accurate if you measure carefully.|
|Then the front portion was drilled. I will drill some similar hole in the lower frame tube. Spacers will not be needed since the Sikaflex will take care of this.|
|The fit came out really well, altough the skirt will need some final trimming and sanding of the edges. I hope the left skirt will fit as good as this one.|
|The aft area came out pretty good as well.|
|The left skirt did not fit as well as the right one, but after some time I got it pretty good. It will need some fiberglass work though.|
|The aft area did not follow the fuselage skin quite well. Gap is up to 3/16" so I'll see what to do with this.|
|A more closer look at the excessive gap.|
|Both skirts are fitted and drilled. I drilled #40 on the bottom. I trimmed the top of the skirt so as to come equal with the glue area on the canopy. The front is trimmed equal to the plexi and will be covered by the windshield fairing when the canopy is closed. This will be the final shape of the skirts.|
|This shows the joint of the two skirt halfs.|
|Both halfs will be joined with a fiberglass/epoxy lay-up. Some flox (mixture of chopped fibers and epoxy) will be used to seal the gap between the skirt and the slider.|
|A view on the right aft part of the skirt. The gap is significantly less than on the left side, but can be improved.|
|The next day I had a look again at the gap on the left skirt. I was not really happy with the fit and I found this could be improved. So I unclecoed the aft 1/3th part and tried to re-fit the skirt. I pulled it tight against the fuselage and canopy. Now that it was trimmed to final shape I had a better view. Fit came out almost perfect, so I decided to simply relocate the aft two or three holes in the skirt to match again the existing holes in the canopy. Some of the other, more forward holes were simply elongated to match up. The gap is virtually gone, minor imperfections will be filled with flox.|
|I was able to improve the right skirt as well in a similar way. The skirts were trimmed again on the canopy side since they moved up like 1/4". This saved me a lot of fiberglass work though (I even thought about cutting it up), only minor filling needed. You know, sometimes you need to leave it alone for a while to get better insights.|
|Here you can see some of the redrilled holes.|
|Time to join the two halfs together. I first put a thick markerline around the skirt edges, removed the skirts and then taped everything off. The markerline shows through the tape (not visible in the picture). I then applied a couple of layers of release wax.|
|I apllied some flox, about 1/8" thick, in the markerline area and built up some flox around the slider rail. I then clecoed the skirts in place.|
|I applied three layers of fiberglass (200gr/m²), starting with about 4", then 6" and then 9" width. I ended with a layer of peelply to absorb excessive epoxy and give it a nice finish. This will be left to cure for about 24 hours.|
Progress on the canopy skirt was slow. It needed lots of filling, sanding, primering, and then again filling,.... Well you get the point, it took about three of these itterations to come to a smooth finish. But I'm very pleased with all the work done, it was worth it.
You may also notice the thickening of the edges on the inside all around the skirt. This is were the flox, with one layer of glass over it, was applied to nicely conform to the fuselage. This way it will be fully closed with virtually no gaps. After painting I will put a 1/2" wide UMH tape along the inner edge were it touches the fuselage skin. It will act as a seal but also will prevent from scratching the paint.
|Rear view of the skirt. Note the nice transition over the rear slider track.|
|The skirt was then positioned onto the canopy frame so I could mark all the areas which will be glued. I also taped off all the areas which should remain free of glue.|
Ready for glueing... Finally we get to see some light at the end of the 'Canopy-tunnel'.