The final stretch and shrink

With the plexiglass canopy parts mostly under control, I’ve moved back to finishing the canopy frame and skins.

Final-drilling the rear canopy frame

First off, I finished match-drilling the rear canopy frame. Nothing too difficult here.

Rear canopy frame riveted together

I pulled the frame off the fuselage then deburred, countersunk, primed and riveted everything together. Then, I started on the canopy lift strut attach brackets.

Tapping the forward strut attach points

The forward attach points require a lot of tweaking and fitting to fit inside the forward canopy frame. Once match-drilled, they’re tapped to accommodate #10 screws that keep them in place on the frame, and also for the large “knob” that provides an attachment point for the lift struts.

Quality Chinese taps

This quality Vermont American tap failed on its second use. I did a little research on where VA’s tools are made, and it seems like their name should really be Vermont Chinese, or Guangdong German, or something that more accurately depicts where the company really resides.

Not that I mind buying cheap Chinese shit tools…I go straight to Harbor Freight when I need a tool that I’m gonna intentionally tear up or modify, only has to last for a few uses, or most importantly, is something that my life won’t depend on.

Rich's lift strut attach points

I’ve been waiting a long time to use these custom-machined canopy strut mounts from Rich Mileika at Machine, Inc. Not only did they save a lot of fabricating time, they look really cool too.

Locating the right position for these mounts was the easy part; getting them screwed into place was harder.  Once the mounts were match-drilled to the canopy rails for #10 screws, I had to get up, under and behind the canopy rails to get the locknuts in place.

Lift struts installed

I didn’t have any wrenches that would get into this spot, so I improvised…I took a cheap 11/32″ socket, hammered it onto a piece of 1/4″ aluminum fuel tubing, and bent the tube such that I could get the socket around the canopy rail. As ugly as it is, it worked like a champ. After I used it to get the mounts installed, I pulled the socket off and reattached it with JB Weld – probably won’t be the last time I’ll need to use this device.

Struts mounted

Here’s the canopy frame with the lift struts attached. Cool.

Canopy with lift struts

I put the canopy back on the frame…it’s time to start fitting the side skirts.

Canopy ready for skirt installation

The challenge here is getting the skirts clamped in place. Some builders have made some really spiffy clamps out of aluminum C-channel to slip under the skins and hold them in place, but I didn’t have the patience to do that.

Double-sided tape for skirts

Instead, I just used some 3M two-sided tape to hold the skirts in the correct position until I could raise the canopy and clamp them with regular Pony clamps.  In the pic above you can see that I’ve already laid out and pre-drilled the side skirt rivet holes.

Skirts taped in place

Lookin’ good prior to drilling…

Skirts drilled to canopy

And after several minutes sitting inside the closed canopy (cool!) with an air drill, the side skirts were match-drilled to the frame. Not much left at this point except to countersink the frame holes and debur/dimple the skirts.

One of the things I wasn’t too happy about was the fit of the forward canopy skin to the forward fuselage skin – they just didn’t quite line up.

Metal shrinker in use

As I tend to do, I threw money at the problem. I made a trip to Harbor Freight and bought a metal shrinking/stretching tool set. After practicing on some scrap sheet metal, I used the metal shrinker on the leading edge of the canopy skin.

Forward canopy skin fitted

The results were better than I expected…the metal shrinker really closed up some of the gaps between the canopy skin and forward fuse. Unfortunately, I didn’t get a picture of the fit with the canopy installed, so you’ll just have to trust me.

One slight downside to the metal shrinker is that it leaves small toothmarks on the metal when it’s used – but a scotchbrite pad on the die grinder made quick work of them.

Canopy brace

Like most tip-up builders, I chose to install the optional canopy reinforcement kit. Otherwise the canopy frame is pretty floppy even when the canopy bubble is installed. There are a lot of holes and slots that need deburring, fortunately there really isn’t much more of this to do on the project.

The plans call for the three large lightening holes to be “flanged”, or have the edges of the holes bent slightly to make the metal stiffer. There are lots of way to do this, and I chose the old-fashioned way – a piece of delrin with a slot cut into it, which is used to bend the edge as it’s slid around the inside of the hole.

More flanges bent

It’s a pain, because several passes are required to get a good bend – but in the end, the flanges came out great.

Canopy stiffeners match-drilled

Here are the stiffeners drilled to the canopy frame.

Clips partially drilled to canopy frame

There are small tabs to be fitted and drilled to the stiffeners…not hard to do.

Both holes drilled in clips

…and they’re done.

frame ready for deburring and priming

At long last, it’s time to prime the canopy skins and stiffeners, and rivet them to the frame.

Primed canopy frame parts

Blecch…priming. I’m glad there isn’t much more to do.

Primed canopy frame

Priming the canopy frame was a pain, but hanging it from the engine stand made things easier.

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The canopy skin doesn’t fit particularly well on the frame, so I used an epoxy and flox mixture to fill gaps between the skin and frame. Once it cured, Bob DiMeo and I riveted the skins on. The epoxy/flox mixture worked pretty well – there aren’t the dimples in the canopy skin that I’ve seen on other projects.

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More riveting fun, this time after several pop rivets have been pulled. The pop riveter takes some manual effort to use, and my forearms are aching.

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Unfortunately I neglected to take any pictures while I painted the canopy frame interior with   JetFlex WR. This took a long time…I did a lot of repainting to get a good finish, and it was a real pain.

After the JetFlex dried, I masked off the glareshield for surface prep, priming and painting.

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I used a good flat black automotive enamel to paint the glareshied, and it came out very nicely.

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I installed the canopy strut pivots…kinda satisfying to do something so simple.

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Here’s a bit of visual progress…the painted canopy frame with the canopy installed. Very cool!

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Another picture? Sure, why not…

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The last bit of work was installing the aft canopy latches.

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I don’t have much to add to the instructions, except that I had to do some improvising to keep the latch fingers clamped in place while I match-drilled them. A piece of spruce filled the bill.

I also clamped and drilled the upper canopy safety latch block to the canopy frame. Unfortunately, I forgot to take any pictures so you’ll have to use your imagination. I deviated from the plans a little and installed a spring beneath the washer and cotter pin that hold the handle in place. Once the block wears a bit and the handle turns more freely, the spring will pull the handle tight against the frame and keep it from inadvertently rotating to the close position, with the unfortunate effect of locking the canopy from the inside. It’s happened to other builders, and I’d like to avoid all the gyrations they had to endure to get the handle unlatched.

Installing the canopy release pivot

Most tip-up builders don’t go to the trouble of installing the canopy emergency release because (a) no one has ever bailed out of an RV-7, and (b) the release handle takes up valuable real estate on the instrument panel.

I’ve been debating the merits of installing the release for a few years, and finally came to the conclusion that I’d rather have it and not need it rather than the other way around. I also want to keep the instrument panel relatively simple, and keeping space for the release handle forced me to do that.

The first step was to drill the release pivot block to the hat section on the subpanel.

Cutting the hat

With the holes drilled, I installed nutplates to accommodate the attach bolts.

Canopy latch temp fitted

In this picture the pivot block and actuator arm are in place and attached to the canopy hinge pins with steel rods. Actually, the left rod isn’t connected to the actuator because the rod was slightly short even though it was fabricated according to the plans. So…I got to fabricate another one that was 1/16″ shorter.

There’s not much to add about fabricating the steel parts, except that the slots in each steel rod that accommodate the actuator and pins are most easily cut with a Dremel tool with a cutoff wheel. Some work with files will still be required, but the Dremel will get 95 percent of the cutting done.

The release mechanism is on the shelf now, and will be reinstalled right before I’m ready to rivet the front fuselage skin in place.

 

Rear Window

It’s December 29 and I’m finally getting a chance to complete this post on finishing the rear window. So for all you Mighty RV fans out there (I think we’re now up to three), here’s a narrative on trimming, fitting, marking and drilling the final part of the canopy.

Vans’ instructions call for rough-marking the rear canopy trim line before cutting the canopy into forward and rear sections. For some reason I didn’t do that, so with the forward canopy separated and placed in approximately the right position, I laid the rear canopy over the fuse and marked a “do not cut” line around the fuselage skin edge.  Yeah, I went over the top with reminders about where not to cut…

Rear window marked for cutting

I then did a rough estimate of a “cut here” line based on the no-cut line. I don’t recall the distance, but it was generous – I took off just enough so that the canopy would fit under the skin.

Rear window cut line taped

Here’s the first cut line marked with masking tape. I like that Scotch yellow-green masking tape…it just looks more “aerospace-y.”

Rear window trimmed and temp fitted

I got the first trim cut just about right; the rear canopy seats nicely around the skin edge, and there’s enough overlap of the roll-bar to make it easy to final-trim the forward cut line that abuts the front canopy.

The only thing you can’t see in the above picture are the bits I had to cut out of the forward lower corners of the rear canopy so they’d fit around the roll-bar attach fittings.

Rear cabin skin screw line layout

One final task before drilling to the skin and rollbar – marking hole locations for the screws that attach the fuse skins to the canopy. I borrowed a trick from Mike Bullock and used a piece of masking tape to lay out hole spacing. I laid a piece tape parallel to the skin edge at the correct edge distance and marked the location of the first and last screw holes.

Read the plans carefully here, because Vans doesn’t explicitly call out the edge distance – it’s inferred from one of the cross-sections depicted in the plans.

Rear window screw locations laid out

With the first and last hole marked, I pulled the tape off, measured the distance between the first and last holes, and did a little airplane builder math to mark the rest of the screw hole locations. After that it was an easy matter to put the tape back on the fuse and mark the holes for drilling.

One side note – regular masking tape is kinda stretchy for laying out hole spacing, so I used some 3M plastic fine-line auto painters tape I had laying around from a previous project.  This stuff worked great – it was easy to get the holes spaced perfectly because the plastic tape didn’t stretch much at all.

Laying out screw holes on the roll bar was easy – all I had to do was match the locations of the holes I’d already drilled for the front canopy.

Rear window drilled 1

I bribed Ellen with the promise of a nice dinner at our favorite Mexican restaurant if she’d come up to the hangar and help drill the rear canopy, which she graciously agreed to do.

This was a piece of cake compared to the front canopy but there are a couple of tips that help improve the drilling process. First, it’s a good idea to pre-drill the fuselage skin holes with a small drill bit without the rear canopy in place; the small holes help center the tip of the 1/8″ plexiglass drill bit when match-drilling through the canopy.

And second, be careful to not drill through the rollbar with the plexi bit – this would enlarge the holes past the size necessary for a #6 tap. Use the pre-drilled holes on the rollbar to locate the holes, then drill  them with the plexi bit just deep enough to break through the opposite side of the canopy, then enlarge later to full size when the canopy is off the frame.

Rear window drilled 2

And here’s the final product after match-drilling. I still have to trim the forward edge to match the “big cut” line, polish the canopy edges, countersink the screw holes and drill them to final size, but everything looks good for now.

I won’t trim the forward edge until I get the front canopy back on the frame with the lift struts installed S.me builders say that the struts push the whole frame aft, so I don’t want to do any edge trimming until the canopy is sitting in it’s worst-case position with respect to the gap between halves.

P.S. – If I haven’t mentioned it recently, I think I’m one of the luckiest builders – and really, one of the luckiest men – I know to have a wife and partner like Ellen. She’s learned to be an ace riveter, encouraged me to keep going when I’ve wanted to quit, and helped me keep perspective on the truly important stuff – and I don’t mean the airplane.

Thanks, sweetie…

Drilling the canopy

I’ve been busy over the last couple of weeks on consulting projects so I haven’t had the time to work on the airplane until this weekend. On Friday I finished adjusting the forward canopy skin to accommodate the canopy itself.

Frame drilled for canopy

Look at the little piece of green duct tape in the lower left corner of the picture above…that arrow-shaped opening is the final result of trimming the “fingers” in the skin so that the canopy sides transition smoothly to the side rails.

Canopy skin finger trimming

I spent the better part of the day laying out and pre-drilling holes that will eventually accommodate #6 screws that attach the canopy to the frame. After that Ellen and I put the canopy back on the frame, then taped and clamped it in place for drilling.

FAA proof photo 1

Here’s a pic for the Friendly Aviation Administration to show once again that yes, I’m actually building this thing…

FAA proof photo 2

Starting at the top of the canopy bow, we drilled #30 holes through the plexiglass into the frame using an Avery plexiglass bit.  We anchored the canopy down on one side and then the other by drilling and clecoing holes 6″-8″ apart, then went back and drilled the rest of the holes.

Canopy drilled to frame

This is a Big Deal…there are only a few minor adjustments left on the side skins, and I still need to trim the rear of the canopy to it’s final cut line, but those are small tasks that I can finish in a day.

Baby steps toward the Big Cut

Cutting the canopy isn’t something to rush. I read and re-read Vans’ instructions, and researched other builders’ websites, to get a good idea of how to trim the canopy without damaging it. A replacement canopy is more than $1000, so cracks are something to be avoided.

I started this part of the project a few weeks later than I wanted to…my hope was to get the canopy cut and installed in August while the temperatures are still warm enough to not keep the hangar heat turned up. Fortunately, September has been fairly warm so not too much hangar heating has been required.

Prepping the OR for surgery

I set up everything needed to start trimming.  Per the instructions, I first cut off the portions the canopy where it was clamped in place for molding.  The back of the canopy was the first to go…

The first canopy cut

…and trimming turned out to be a little easier than I thought, but some care is required to get close to the cut line marked by the tape.

Plexiglass snow

The cutoff wheel creates a lot of plexiglass “snow” particles as it works, except that this snow can be uncomfortably hot when it hits your skin. I didn’t want any of that crap in my eyes or up my nose, so I wore safety glasses and a respirator…

Even two pairs of glasses weren't enough to protect my eyes I continued the process around the sides and front.  It was a little difficult to tell where the cut lines should be, especially on the sides.

Prepping to cut the front of the canopy

With the clamp marks trimmed off, I marked a centerline on the canopy per Vans’ instructions. This is a little tough to do as it’s hard to accurately place a tape measure around the canopy.  I wound up using a piece of string pulled tight from side to side…mark  the string where it lies on the edges, then double it back on itself and you have the centerline – sort of. I don’t think it was very precise, but it also seems to be close enough.

The canopy on the fuse for the first time

There are a couple of tabs on the front canopy frame that overlap the side rails. The instructions require that the tabs and side rails be adjusted to match the curve of the canopy’s front edge, then drilled and riveted. There’s not a lot of guidance here, and it’s hard to see through the protective plastic sheeting on the canopy to tell how the curve should lie. So…I took my best shot.

Adjusting the canopy rail bends - holes countersunk And then riveted the tabs…

Canopy rail fitted and riveted on the right side

…and everything looks good for now.

Canopy marked for cutting

I’m reasonably happy with the canopy fit, so I started marking the line across the rollbar where the canopy will be cut into forward and rear sections. This process is not-really-affectionately known to builders as making The Big Cut.

Canopy forward edge

I worked on the front edges a bit to get them to lay down a little more accurately on the front canopy skin, but from what I’ve seen on other builders’ websites, you can do all the work on this area you want but once the canopy is drilled in place, some gaps will open up.  So I’m going to get it close and not worry about it.

Canopy in place for cutting

I hoisted the canopy onto the sawhorses and plywood, and used some long 2x4s to move it off the work surface They also gave me something to clamp some smaller pieces of 2x4s as side supports that keep the canopy from spreading as I cut it.

As other builders have also done, I laid several pieces of masking tape along each side of the cut line to help guide the cutoff wheel. I was skeptical that this would work, but it did and very well too.

I took a few deep breaths, and started cutting…

Starting the Big Cut

…and the process went very well. I used tongue depressors to keep the canopy separated  as I worked my way along the cut line.

The Big Cut is complete

And here’s the completed cut…what a relief to have this done.

Forward half of canopy on the frame

It’s a lot easier to move the canopy on and off the fuselage. I’ll be doing a lot of that as I finish fitting it to the frame and then drilling the attach holes.

A riveted frame

Got just enough time in the hangar tonight to rivet the canopy frame together and put it back on the fuselage. I left the primer to dry for a couple of days, and the Nason etching primer I used was tough as nails!

Frame riveted before installationFrame rivets

There’s an small and easily fixable mistake in this pic. Can you spot it?

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And now it’s time to start trimming the canopy…yikes!

More fun fitting the canopy frame

More fun with the canopy this week as I spent several hours adjusting the fit of these parts that form the rear canopy frame.

The distortion caused by both the flanges and L-shaped bend in each frame half takes some work to make them fit adequately. The instructions tell builders to flute these parts to remove the distortion, but at least one of mine was just about right out of the box and really didn’t need fluting. The other one doesn’t fit quite as well, but I’m resisting the urge to flute it because (a) the fit isn’t that bad and (b) I tried fluting a spare frame part I had and it was a PITA.

In this picture the frame halves are not perfect, but they’re getting close to being good enough.

Rear canopy frame

The side rails were an easier fit, because Van’s had already done all the bending and metal shrinking needed to make the side rail curve fit the longeron bends I worked so hard to perfect several years ago.

Canopy side rails

The side rail flanges don’t quite conform to the aft frame parts, but I think they’ll pull into shape pretty well when they’re drilled and clecoed.

Side rail to canopy bow fitI still have some parts to fit to the frame, so stand by for more words and pictures.

Canopy splice platesLaying out the side rail and rear canopy bow splice plates. Note that the side rail doublers at the bottom have one hole that isn’t marked to be drilled – that’s because Van’s conveniently forgot to mention in their plans that there’s already a hole through the canopy frame in this area, and if you drill the hole in the splice plate it won’t line up with the frame hole.

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Ok, so I said I wasn’t going to flute the rear frame – but I did, and it actually came out pretty well. Here’s the side rails and rear frame clamped into position.

Fitting the side rails

The little cheapo Harbor Freight clamps are holding on some strips of 0.032″ scrap that simulate the canopy side skins. The side rail is correctly placed when the bits of scrap lie flush with the side of the fuselage.

Side rails drilled to F-631s

Sharp-eyed RV builders will see that I’ve inserted a shim between the side rail welded angle and the F-631 rear frame half.  The fit wasn’t quite what I wanted, so when in doubt – shim it out. After that I couldn’t think of a good reason not to drill everything, so I did.

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These plates splice the side rails to the forward canopy frame, and drilling them was a bit of a pain. It’s vital to uncleco and peel back the forward canopy skin, as nine of the ten holes in this part don’t go through that skin and drilling through it would be uncool.  You’ll see one hole (bottom row, second from the right) that doesn’t quite line up. That hole *does* go through the skin and frame, and once the other holes were done I back-drilled this one using the forward frame as a guide.

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And here’s everything drilled and clamped to make an almost-complete canopy frame. As my friend Jim would say, this is one of those moments of Big Visual Progress. They kinda sneak up on you after a lot of tedious fitting and drilling, then suddenly everything comes together…et voilà, it looks like a real airplane part.

I hated to take everything apart, but there are a couple of small parts left to fabricate and fit to the frame.

Wedges

Look carefully in the pic above, just under the two leftmost copper clecoes, and you’ll see a thin aluminum wedge filling the gap between the side rail splice plate and forward canopy frame flange. Scroll back a couple of pictures and you’ll see the unfilled gap.

I had to make two of those – one on each side of the canopy – and each one took about an hour of cutting, sanding, filing and fitting.  What fun…but now I can take the frame apart  and debur, countersink and prime everything before riveting. And that, in turn, means it’ll soon be time to work on the plexiglass canopy itself.