Gas Strut Mounts – 1.5 hrs

Thursday May 31, 2012

The gas strut mounts are another one of those items shown on the drawings but the written instructions don’t even mention them. I followed the drawing and what I could learn from others on the web. I placed the C-725 block 3/8 inch forward of the C-613 splice plate but that made it overlap one of the rivet holes for the C-702 skin so I moved the block forward about 1/8 inch to clear the rivet head. With the block held firmly in place I drilled through the WD-716 canopy frame and C-702 skin using the C-725 as a guide.

Next I dimpled the holes in the C-702 skin. Under that, the WD-716 needs to be machine countersunk but the drawing warns that these countersinks will go through the material. So I made a couple of little sacrificial plates to back up the WD-716 and help keep the counter sink centered on the hole. You can see one of those in this picture.

The countersinks turned out fine with this method.

Then I removed the C-725 blocks and tapped the holes. The upper and lower holes are 8-32 and the center hole is .312-18 thread.

Then I put it back together to check out the fit. It looks good from the outside. These screws will end up being glassed over after the canopy is bonded.

On the inside it looks good too. You can see the rivet hole I dodged just aft of the C-725 block.

Side Skirt Shims – 1.5 hrs

Monday May 28, 2012

The combined weight of the two shim strips I mounted to the canopy side rails is .45 lbs so I decided to reduce weight a little by drilling 3/4 inch holes between the rivet holes. This reduced the total weight by .10 lb so it was worth the time to me. You can see the left side shim in this photo. As usual, click the photo to enlarge.

Side Skirts and Rear Window Trim – 4 hrs

Sunday May 27, 2012

The side skirts hold the canopy to the Wd-725 weldments on each side of the fuselage. Since I am bonding with Sika Flex I needed to add some space for the bond material between the skirt and the weldment. For this I used some .063 thick alcad strip as a spacer. Aligning this strip is a little tricky because it is only 1.25 inch wide (that’s what Vans had as a standard material) and the rivet hole pattern could easily get too near the edge so I was very careful setting this up. First I taped the shim strip to the side of the Wd-725 to get the position right relative to the joggle.

Then I placed the skirt strip against the shim with the lower edge flush to the longeron. I slide the skirt over just enough to see the shim strip and marked the vertical position on the end of the strip.

After marking both ends I drew straight lines connecting these marks to define the outline of the strip under the skirt. From that I marked off lines for the holes 3/16 inch inboard from the edge lines and place hole centers on spacing of 1.45 inches. I then drilled pilot holes in the skirt on this hole pattern using a #40 drill.

Then I placed the skirt back on the longeron and flush with the edge o the C-702 skin and match drilled all the holes through the shim strip and the Wd-725. Of course I repeated this process on the other side of the fuselage. Oh, and the edge distance turned out fine on the shim strips.

Next I removed the parts to deburr the holes and clean up chips. While the forward canopy was off, I marked the rear window along the mid plane of the roll bar for a trim cut. This is to get the edge parallel to the centerline on the roll bar. It was warm today so I could do a trim cut without using the heat gun. As a result the front edge of the rear window now aligns very nicely with the roll bar.

Aft Window Trimming, Rudder Cable Fairings – 6 hrs

Saturday, May 26, 2012

Over the last few days I have only had a few opportunities to get into the garage and work on the project. In those days I have made just a couple of minor tweaks to the front curve of the canopy to improve the fit. Now it is just about as good as it going to get up there and so I decided to go ahead and trim the sides to the final line which is just above the joggle on the side skirts. So with the canopy in place and aligned as well as I could get it this morning I marked the lines along the sides for the cut. The trim along the straight lines took just a few minutes, then I sanded the edges to prevent cracks. I put the canopy back on to check the results and now only the aft edge is left to trim to the final line.

Denise and I went flying this morning so after we got back I went back to work on the aft window. Ron, a friend came by and gave me a hand with this today. I had marked the “do not cut” line along the profile of the aft top skin so I marked a line 1.25 inches aft of that and that is where we cut. That allowed us to insert the rear window under the skin and do a check of the fit. Well, almost. We found that the top center of the plexi bumped into the reinforcement plate on the top channel where it connects to the top skin. So it took another trim of about a ½ inch in that local area to get the window to slide in all the way. Here is a shot of the window clamped in place. Not a bad fit.

Then we found that the lower forward corners interfered with the angles that hold the cabin frame to the longerons  so we had to make another trim on those corners to get the canopy to lay down flush on the frame. When that was done, a could not resist putting the forward canopy on also to see how the two pieces fit together. Now I’m getting excited because even though the gap between the two pieces still needs to be adjusted the two pieces look like they form a continuous smooth surface from front to back. No step or apparent change in angle at the parting line.

Before Ron took off, we also cut out and drilled the little rudder cable fairings I bought from Avery. These just look a little nicer than the plastic tubes sticking out of the side of the fuselage.

Ordered Engine, More Canopy Tweaks – 1.5 hr

Tuesday May 22, 2012

A momentous milestone today. I ordered the engine – the single most expensive piece of this machine. Everybody has their own perspective on this but for me the options for suppliers came down to Superior, Mattituck, and Aero Sport Power. Superior has the best price but the warranty clock starts at delivery versus from first start up. Since it could be a year + before first engine start I could be out of warranty before it flies. Mattituck has a great product but they just announced that they are going out of the experimental engine business at the end of the month. What a shame. That leaves Aero Sport which also has a great reputation and a loyal following. They could give me exactly the specs that I wanted and have held their prices steady for the past year or more which I appreciate. So they got my business with a $3000 deposit. This thing is a lot of money, so I hope it turns out to be a good choice.

Here are the engine specifications:

1. IO-360-B1B, 8.5:1 compression ratio, 180 HP (will run on premium auto gas without ethanol)
2. Superior components with roller lifters
3. Port and flow matched cylinders (for smoother operation and better leaning)
4. Dynafocal 1 mounting
5. Set up for fixed pitch use initially with easy conversion to constant speed in the future ($200 in parts required)
6. Vertical air induction
7. Airflow Performance Fuel Injection (AFP 8000014 kit)
8. Dual P-Mags with automotive spark plugs
9. 18 mm plug threads with 14 mm adapters for automotive spark plugs (like to maintain the option to use aviation plugs in the future).
10. Dynamically balanced

This is a TMX IO-360 but mine should look a lot like it with the main color gold and black cylinders and valve covers.

Delivery will be around mid July. I could have had it shipped by the end of June but I told them not to hurry. I won’t be ready to hang it for a while anyway.

Tonight I made a few more tweak cuts on the canopy around the front end to make it sit more flush on the C-702 skin and to make the bow more symmetrical. Here is one way I checked the curvature across the front. I marked off equal distance marks from centerline then compared the radial distance down a line from a common point up the canopy centerline.

The gaps up front are just under 1/16 inch without shims. Getting very close now.

Fitting the Canopy to the C-702 Ears – 2.5 hrs

Monday May 21, 2012

To get the canopy to fit the C-702 skin at the “ears” you have to enlarge the slots where the plexiglass transitions from outside the skin to inside along the side rails. Every builder seems to do this differently. Some even cut off the ears. I’m not going there yet but the plans are totally silent on what to do here. So I started with a modest enlargement of the notches. First I sketched the shape I wanted on the skin.

Then I cut the material out with my dremel and smoothed the edges with sandpaper. The right side looks virtually identical. We will see if this is enough later.

At times like this I miss the parts of this project that are clearly defined; cut to this dimension, drill hole here, rivet this. This canopy work is slow going because its all trim to fit. If I was more brave I could probably get this done a lot faster but I don’t want to trim too much so I inch up on the final shape a little bit at a time. When I first put the canopy on behind the C-702 ears the front edge was lifted up at least 1/4 inch above the skin all across. I made several trim cuts to raise the sides in the area of the ears to get the canopy to settle back down. This was time consuming of course since I had to mark the canopy, remove it, make the cut, sand the cut edges, clean up the mess, then reinstall the canopy and check the fit. After numerous iterations I now have the front edge with a 1/16 gap to the skin which I set using a couple of shims. I am thinking about leaving a small gap there because I am going to use Sika Flex and it needs a small gap for good strength.

You can see one of the 1/16 shims in this view. The fit is actually pretty close to where I want it to be. I think there might be one more small trim on each side to finish the fit on the front, then I will check the sides to see if a final trim is required there. The right side is fitting better now. I think it’s going to be OK in spite of the distortion in shape I saw on that side earlier.

Speaking of Sika Flex, my order of materials arrived so I am stocked for the bonding. I got two tubes of Sika Flex 295UV bond, a can of 205 activator/cleaner, a can of 209D primer for the plexiglass, and a can of 206G+P primer for the aluminum. Altogether this stuff ran me about $200, so it not trivial.

Completed the Big Cut! – 8 hrs

Saturday May 19, 2012

Really big day for the RV-7A! When I got started this morning I didn’t realize I was this close to the big event. It kinda sneaked up on me. But I am getting ahead of myself. When I left off last time I was trimming the front of the canopy. The sides and aft end only had the clamping marks removed. The canopy was sitting up about 3/4 inch above the roll bar due to the aft end sitting on the skin. I wanted a better fit than that so I could get an accurate mark for the big cut so I decided I needed to make two more trim cuts, on one the front and one on the aft end. The plans say to cleco on the top skin to mark the profile of the rear window. But I already had it on, so I took it off and put it back on over the canopy. I’m not sure that is what the instructions meant but it worked well enough to easily draw the curve of the aft skin on the plexi.

Here you can see the curve marked “Do not cut” is the profile of the skin. The parallel curve is 1.75 inches beyond the skin line so I should be way safe if I keep my trims outside of that.

I trimmed about an inch off the aft end and about 1/4 inch on the front. After those trim cuts the canopy came down almost flush against the roll bar. Since I plan to use Sika Flex to bond the canopy to the frame and the Sika needs at least 1/8 inch gap for the bond I taped six 1/8 inch rubber washers on the roll bar to act as shims. The canopy was sitting directly on several of those but there was still about 1/4 inch gap at the top center. OK, so I will have to live with that. It should not keep me from marking a accurate line for the big cut. So I checked to make sure the canopy was aligned then I taped down the sides to get them as flush as I could. The right side still takes more force to push it down flush but at least it is better than before. With everything in its ultimate place I marked the big cut line on the canopy making little dashes every 1.5 inches or so by visually aligning it to the center mark on the roll bar. Then I took blue masking tape and ran three layers along the forward side of the mark for the cut.

With that marked I pulled the canopy off the fuselage and put it back on the cutting table. This time I blocked it up on cross beams so I could get the cutting tool down to the lower edge of the canopy for the cut. I nailed blocks to the cross beams to keep the forward section from expanding and I put tape across the lower edge of the aft section for the same reason.

Then with my helper, Jennifer, I made the big cut. It was 71 degrees in the garage at the time so I used my hot air gun to warm the plexi for a while just to make sure it was beyond the brittle range. I used a tent like before but I did not take another picture of that. I took my time and cut the line in about 15 minutes. I stopped every 8 inches or so to tape up the gap behind the cut point to give it support. I would not call this an non event, but there were no surprises or issues. I am so happy that is done!

After sanding the edges to remove sharp edges and cutting marks I put the forward canopy on for a fit check. Wow, now the plexi fits right down flush against all the rubber spacer washers as I had hoped. The cut line is right on the money along the top and about 1/32 forward of the line at the lower edges – about what I expected based on what others have seen. That will get corrected when I do the final trim for the operating gap of about 1/16 inch.

Here you can see a close up of one of the rubber hose washers giving me a 1/8 inch gap for bonding. Sorry it’s kinda hidden by the blue tape.

Then I marked the sides for another trim cut. The side have to be cut to fit within the joggle on the side skirts.

After the side trim I put it back on the fuselage for another fit check. It’s getting closer each time. Next I suspect I will be doing battle with the “ears” on the C-702 skin. But that is it for today – a good day, but I am ready for a break.

Trimmed Canopy Front – 1.5 hrs

Thursday May 17, 2012

I trimmed a bit more off the front edge of the canopy tonight, all the way across. I am inching up on the point where the plexiglass turns from horizontal to sloped at the front center point and trying to get the front sides closer to the final line where they blend into the front edge and can go under the ears of the canopy frame skin. After the cut it sits better than expected for this stage. It is flush along the 10 and 2 oclock positions.

This is the right front side.

In the front center there is about 1/16 gap which is reasonable given that I still need to trim more off the front sides. More to come.

Finished Rough Trim Cuts – 2 hrs

Tuesday May 15, 2012

I finished the initial edge trimming on the canopy tonight removing the left and front edges using the same process as before. After I sanded the edges and cleaned up the mess I placed it on the fuselage with some help from my wife and daughter.

The gap between the canopy and the roll bar is about 1 inch so there is still a good bit of trimming to do but at least now I can gauge about how much to remove on the edges. The front needs about another inch removed on center but this sides are good for now until the ends are trimmed and I and see how much the side drop overall.

One area that concerns me is the right side. The left side fits great for this stage but there is a distortion in the plexiglass that causes the canopy to bow out along the right side. This next photo shows the left side along the canopy frame from below looking up. The edge fits nicely against the skin with minimal gap. I see no problems getting a good fit on this side. A light pressure is all it takes to press the canopy edge up against the side rail.

This photo shows a similar view on the right side. The edge bows out away from the skin about 1 to 1.5 inch and it takes about 5 lbs of force to press the skin up against the side rail. It may be a real challenge to get this to fit well. I need to make inquiries on this to see if this is unusual. More to come.

Update: I posted a question on the VAF forums about the distortion and the feedback I received from other builders was essentially don’t panic, keep trimming and it will get better. I hope they are right. I plan to continue along these lines and see.

First Trim Cuts on Canopy – 2 hrs

Monday May 14, 2012

Tonight after work was the big event of making the first trim cuts on the canopy. I set up the canopy on a piece of the finishing kit shipping crate I had saved for such an occasion. It is 4 feet wide by 5 feet long and the canopy fits perfectly between the 1 x 2 strips mounted on the sides. I supported the canopy with some boxes to lift the right edge up a few inches to allow me to cut that edge.

It was 70 – 75 degrees F in the garage already at 7 PM but I put my hot air gun under the canopy and ran it on low for an hour to warm the canopy even more. I put the gun well away from the surface because I did not want to risk burning the plexiglass.

To heat it more uniformly I hung a plastic drop cloth over the canopy so the warm air filled it like a tent. The hot air spilled out along the gap on the sides mainly which helped heat the edge where I was going to cut first.

My first cut along the right edge took about 20 minutes as I was going slow and putting tape across the cut every 10 inches or so to support the edge. But I made it to the end without any crack incidents. I used 60 grit sandpaper to knock the roughness off the edge first, then switched to 120 grit to smooth it further. I have 220 grit also but have not used that yet. After cutting the right edge I cut the aft mold marks off as well, repeating the sanding treatment afterward.

This is the tool I used. It is an electric cut-off tool from Harbor Freight. My die grinder and air compressor just don’t have the stamina to get through this. My only regret about the HF tool is it is a bit bulky and kinda heavy. I may try using my palm drill after reading that some builders recommend that.

Overall, my first experience with cutting the canopy was not too bad. The cutting plexiglass has a strong, nasty odor and the chips got all over me and the floor nearby making a big mess, but the cutting went pretty well. The cut edges even look pretty good for a first try. Still, I hope to get better at cutting a straight line before the Big Cut.