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Continued to Fill and Sand the Canopy Fairing – 4 hrs

June 19, 2013 Leave a comment

Wednesday June 19, 2013

After the epoxy on the canopy fairing had cured for a day I block sanded what I could and sanded the rest with paper wrapped around a piece of pipe insulating foam which is about 2-1/2 inches diameter. If you click the picture below you can see a few low spots but overall it is getting there.

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That was followed by two more applications of epoxy with Microlight filler locally in the low spots. The second application was without black pigment since none of it was in the area where it could show through from the inside of the canopy. After this is sanded out I will probably put the forward skin on and check the lay of the two surfaces against each other to see if any additional fill is needed in that area. If it looks and feels smooth to the touch I will spray on some gray primer to get a better look at the surface because it is hard to judge in black with all the blotchiness.

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Categories: Canopy, Finishing Kit

Bonded Rear Window – 8 hrs

December 8, 2012 Leave a comment

Saturday Dec 8, 2012

I have decided to include a Trutrak Gemini PFD in my panel as a back-up instrument for altitude, airspeed, attitude and heading. It is a relatively low cost, compact instrument that gives me a completely independent source of primary flight data. But that means I need to route pitot and static air lines to the front of the fuselage. It was easy to add a Tee in the pitot line as it comes into the fuselage at the wing and route the green pitot line forward. The white static line comes from behind the baggage compartment so I need to run it under the seats. I added a Tee in the line as it goes to the Dynon ADAHRS. You can see it here along the main longeron. The new line is going down toward the bottom skin behind the baggage bulkhead.

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Looking lower down in the fuselage you can see that I drilled a hole in the lower rib and installed a snap bushing so the static line can pass over to the right side of the fuselage and enter the conduit under the copilot’s seat.

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When the line exits the conduit under the copilot it passes through another snap bushing and jogs back toward the centerline where one of the two standard snap bushings allows it to pass through the main spar to the center console. That gets it to the forward part of the cabin. I’ll worry about the routing from there to the Gemini later.

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After that I was basically satisfied that I had completed enough of the aft fuselage work that I could permanently install the rear window. It will be harder to get access to that area with the window in but my Sikaflex bonding supplies are ending their shelf life so I need to bond the window in soon or spend another $150 or so for fresh materials later. I decided to bond it now.

I spent some time finishing up the masking to protect the adjacent surfaces from the primer and to give me clean lines on the bonded fillets. I applied two layers of electrical tape for bonded edges; the first layer to be removed after priming and the second layer to be removed after forming fillets. My process here is a hybrid using Sikaflex along the top of the roll bar and using screws along the edge of the top skin. The screws give me comfort that the window is secure regardless of the strength of the bond and the Sikaflex gives me a nice finished look along the canopy seam with a black stripe that hides the roll bar. However to seal the window along the stop skin I am using Alex Plus caulk which was recommended on the EAA web site for sealing around antennas. I was originally going to use silicone but even minute traces of silicone can cause problems with paint adhesion later on. The siliconized caulk is rated to last 35 years and will not interfere with the adhesion of paint to the skin.

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In the photo below you can see the masking of the window itself. The masking along the far edge is for the Sikaflex. The masking around the remaining perimeter is for the black primer I am applying around the edge to give a nice finished look. The black will extend ¼ inch past the edge of the skin much like the black perimeter band you see on auto glass. This is just for aesthetics.

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Here it is after the activator and primer were applied. It is very easy to leave streaks in the primer that can be seen from the outside of the window so you have to be careful to coat it smoothly and check for visible defects with a bright light on the back side. I took my time checking and touching up to make sure I could not see flaws from the outside. From this point I have 24 hours to get this bonded in place before the primer “expires”.

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I allowed the primer to set up for about a hour (10 minutes is minimum according to Sika) then I placed the window on the fuselage about 2 inches forward of the final position. This gave me access to apply a thin layer of Alex Plus caulk to the edge that mates to the top skin. The caulk goes on white but cures clear so it won’t be obvious. Then I just slid the window into place and clecoed it to the skin with the reinforcement doubler strips on the inside. Going around the perimeter I replaced the clecos with the screws and washers but I used free-running nuts to just snug up the window while the caulk cures. I don’t want to squeeze all the caulk out but I do want a nice thin layer.

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With the rear window attached by 30 screws (15 on each side) to the top skin, there was a gap between the window and the roll bar of about 0.25 inch across the top, decreasing to zero along the sides to where the lower forward corners touched the roll bar. This is how I had shimmed it when I drilled the holes for the screws so the bond gap was basically locked it. The only variability was due to the flexibility of the Plexiglas so to get the front and rear canopy surfaces as flush as I could I put a strap around the fuselage and used a few wood shims in places where the rear window was slightly higher than the front canopy. This was really not necessary but I was just trying to tweak it as well as could. I closed the front canopy to check the fit before applying the bond material.

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When I was satisfied with the fit I injected a bead of Sikaflex into the gap between the rear window and the roll bar trying to get about ¼ to ½ inch penetration. I did not want to push in too much for fear of oozing out the back side.  Once I got the gap filled I used popsicle sticks and my finger to smooth out the bead and make a fillet. Here is a close up after pulling off the masking tape.

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Here is a wider view. Now I just have to let this set up overnight then I will inject a bead of Sikaflex on the aft side of the roll bar along the window gap.

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Categories: Rear Window

Canopy Prep – 2 hrs

October 21, 2012 Leave a comment

Sunday Oct 21, 2012

Today I spent some time planning out the build process for the near future. It is quite a dilemma trying to determine the best order to do things in this phase. I decided that I needed to adjust the clearance between the front and rear canopy sections. It is currently about .020 or less but I know that more gap is needed to prevent the two pieces from binding when the temperatures go up. The plans say .032 is the recommended gap and others on the forum have said it may need more. So I set about to adjust it to about .032 for now. I can always increase it later if necessary.

It took about 5 or 6 iterations of sanding and checking to get the gap right. Here is a photo looking down the seam across the top of the canopy. I think it looks really cool.

My plan is to install the Dynon ADAHRS in the aft fuselage and then SikaFlex the rear window. The ADAHRS will be easier to install without the rear window in place.

I also need to mount the ANL current limiter I bought from B&C Specialty. This is basically a high current (60 A) fuse. But I also need to mount an ammeter shunt in this area and I’m not sure exactly where to place each one so for now I bent one end of a copper bar and drilled a hole for the starter contactor terminal but I will wait to locate the currently limiter holes until I get the shunt which comes in the engine sensor kit from Dynon. I will order that tomorrow. Here is the copper bar yet to be cut to length with the current limiter base just stuck against the firewall but not drilled.

Canopy Follow-up – 3 hrs

July 8, 2012 Leave a comment

Sunday July 8, 2012

Today I had my first chance to open the canopy and see how the bonding turned out. There were a few surprises. The SikaFlex had set up pretty well so I removed the entire canopy and put it on the bench upside down to get better access to inspect it. Unfortunately, as I was removing the frame I got a nice kink in the front edge of the C-702 skin as it caught on the aft edge of the forward fuselage skin so now I’ll have to repair that.

The biggest bonding issue I found was SikaFlex on the aft overhang surface of the canopy on the right side. This apparently happened as the canopy was being placed onto the frame. It must have come down into contact with the Sika bead while shifted too far forward. This area does not show externally but you can see it when you raise the canopy. I was worried that I would not be able to remove the material because this surface is primed with Sika 209 D and the 295 UV adhesive sticks to it like crazy.

I had some single edge razor blades so I tried shaving the material off in thin layers. To my relief the worked quite well and I worked it down until only a trace of adhesive was left on the surface. I did not want to go too far for fear of scratching the surface underneath which would be visible from the outside. You actually have to look closely to see the leftover material now. Since its all black, it only looks like a slight change in the glossiness of the surface.

The beam of Sikaflex did not fill the entire gap between the bow frame and the canopy except for one area about 2 inches long. that’s good because now I can fill the void with fresh Sika and fillet it in for a solid continuous bond over the entire 3/4 inch width of the bow frame. so that is what I did. I masked the area and injected SikaFlex 295 UV in the void areas and used my finger with a nitrile glove to smooth out the fillet. When I removed the making I had a clean fill. I forgot to take a picture so I will drop that in the post later.

Categories: Canopy, Finishing Kit

Canopy Bonded – 7.5 hrs

July 8, 2012 Leave a comment

Saturday July 7, 2012

Well the bonding of the canopy is done. It was a long time getting to this point. What I thought would take a couple of hours to complete actually took about five hours, not including cleanup. Fortunately I had Scott as a helper. It really is a two-man job and I wouldn’t attempt this solo. As we got into action it always seemed like the clock was running so I didn’t take as many pictures as I expected so I will fill in the gaps by laying out step by step what we did. By the way, the steps were all planned in advance. I would not go into this trying to figure it out as you go.

  1. Pre-clean bonding surfaces of bow frame, canopy frame, and side skirts with IPA
  2. Pretreat canopy and frame parts with Sika Activator 205 using a clean lint free rag. Change rag frequently. Use wipe on/wipe off method.
  3. Wait 10-120 minutes
  4. Apply thin, continuous coat of Sika Primer 206 G+P to the canopy bow frame, side rails, side skirts, and C-702 skin using a clean brush or felt pad
  5. Remove masking tape along the inside boundary of the glare shield
  6. Apply thin, continuous coat of Sika Primer 209 D to the canopy using a clean brush or felt pad
  7. Remove outer layers of masking tape (2 layers used, one for primer and one for bonding)
  8. Wait 10 minutes minimum (up to 24 hrs) for primer to dry

Here is what the canopy frame looked like at this point. Notice the clamps on the bow frame to hold it in alignment for bonding.

The primer is very glossy and you can’t tell by sight when it is dry. I tried to put it on thin but it flashes off very fast so if you don’t get a good coat on in one pass the second pass leaves a rough surface as the fresh primer interacts with the first coat.

Here you can see the primer applied to the outside surface along the front edge of the canopy. This is both for bonding to the SikaFlex and also to provide a black border so the fiberglass blend will not be visible from inside the cabin. There is also primer along both sides, inside and outside under the side skirts.

The aft end of the canopy got a wide band of primer. This covers the bond area and the part that overhangs the roll bar for a nice professional black-out look. We tried to make sure there are no voids or brush marks along here that might show through the other side. No primer on the outside in this area.

About 15 minutes after finishing application of primer we started applying SikaFlex as follows:

  1. Apply Sika 295 UV to the bow frame and along side rails
  2. Carefully install canopy and align to rear window with .025 shims
  3. Install clips to secure front edge with pop rivets
  4. Apply Sika 295 UV to the side skirts and install with clecos
  5. Fill exterior gaps with Sika 295UV if required
  6. Clean up exterior fillets with Sika Slick
  7. Apply a bead of Sika 295 UV along the front edge and finish fillet with Sika Slick
  8. Remove rear window without disturbing the canopy
  9. Get inside and fill gaps with Sika 295 UV
  10. Install #6 screws in side skirts with free-running nuts snug
  11. Clean up interior fillets with Sika Slick
  12. Get out and reinstall rear window and verify alignment of the gap and flush edges

Here is the first photo with the canopy installed. The black band looks great and the fit to the rear window is nice, although with .025 shims I expect to sand a little off the canopy edge later to get the necessary gap of about .060 for operation and avoid binding on hot days.

Here it is with everything in place. Nothing to do now but wait for it to cure up so I can open it and check out the areas that are hidden. That’s when I plan to fill any voids.

Categories: Canopy, Finishing Kit

Machined Countersinks in Rear Window – 1.0 hr

July 5, 2012 Leave a comment

Thursday July 5, 2012

Tonight I used the countersink cage to machine countersinks for #6 screws in the rear window holes along the edge of the top skin. Then I used the 5/32 plexiglass drill bit to enlarge all the holes. This is so there will be a little extra gap between the screws threads and the plexiglass.

Then I set up the DRDT-2 and dimpled all the holes in the top skin for those #6 screws.

Masking and Polishing Canopy – 1.5 hrs

July 2, 2012 Leave a comment

Monday July 2, 2012

I am getting very close to ready to bond the canopy to the frame with SikaFlex 295UV. Tonight I was putting the final touches on the canopy itself. I did the final polish on the edges of the plexiglass using 220 and 400 grit sandpaper. The surfaces are quite smooth now and I think that should be more than adequate to prevent crack formation. I still need to check all the countersinks with a magnifying glass to see if any additional polishing is required there. I also buffed the inside surfaces of the canopy where SikaFlex will be applied.

Categories: Canopy, Finishing Kit