Mostly More Cowling – 10 hrs

Sunday July 14, 2013

Most of my time this weekend was spent working on the cowling but I also did a few other things just to keep things interesting. First I made labels for my annunciator panel lights. All I did was print out the labels on plain paper on my laser printer and cut them out to fit in the lights. When you pull the colored lens off each lamp there is a diffuser underneath. I put the label between the diffuser and the lens.

I also made a handle for the canopy release mechanism. The stock handle is long enough to extend out through the instrument panel. I cut it down so it just protrudes past the subpanel when the mechanism is in the latched state. I slotted the tube and drilled a hole for the link pin.

Here is the handle installed on the mechanism in the latched state. I will install the cotter pin later because I know I still need to remove the subpanel to cut a hole for the radio stack.

This view is from the aft side. That adel clamp is not installed yet but I marked the location for a hole and I will install a nutplate there when I pull out the subpanel.

I also started installing the VHF com antenna. Mine is a Comant CI-122 and I am installing it below the pilot’s seat in the most outboard bay. I made a doubler out of some .032 stock alclad including two angles to stiffen it up side to side.

I located it aft of the main spar and as far forward as I could to keep it as far from the ADSB antenna as I could. That put it right under the aileron control rod. I will probably have to install a 90 degree coax connector on the cable for the antenna to keep the cable away from the control rod. I still need to rivet the doubler in place.

But most of my time was spent on the cowling. I picked up some high-build primer at ACS on Saturday and sprayed the top cowling section. Boy it is nice to see the pepto pink disappear. I put on three light coats of primer. After it dried I sanded it out with 400 and 600 grit paper and it is nice and smooth. The oil door was sprayed separately.

The lower cowling still needs a lot of work on the exterior. It is covered with thousands of pits due to the honeycomb layup. So I started filling the pits with slightly thinned epoxy. I started with one coat squeegeed on with a single edge razor blade on the surfaces that are more or less horizontal in this view. It does no good to apply it to the vertical surfaces because it just runs out of the pits. When the first coat was cured about an hour or so and was stiff and sticky I brushed on a second heavier coat – hopefully enough to completely fill the pits. Now I will let it cure so I can sand it out to see if another coat is required.

Four Mini-Projects – 8 hrs

Saturday June 9, 2012

I think I finally decided what to do with the canopy release mechanism. I’m going to make a short handle that will extend just aft of the subpanel so I can release the pins when the canopy is tilted up. That will be useful during the remainder of the build phase and when I finally paint the airplane. It obviously won’t serve as an emergency canopy ejector but that’s OK by me. Seems like almost nobody installs this with the handle poking through the instrument panel.

So this morning I installed the crank arm on the mechanism. I aligned it so the arm was fully aft when the pins were retracted and drilled a hole large enough for a #8 screw. While I was at it I made some final modifications to make the mechanism work smoothly, trimming a little here and there to eliminate rubbing.

My friend Ron came by this morning and we worked on the doubler strips for the rear window screws. We unclecoed the top skin and laid it out on the bench and used it as a template to make strips out of .025 thick aluminum scrap left over from the wing walk doubler. Since there are 15 holes on each side of the fuselage I made three strips on each side that each cover 5 holes. It was helpful to have an extra set of hands to trim and match drill these pieces.

Another item on my list was to make bumper stops for the canopy frame to keep it from shifting too far forward under the influence of the lift struts. A very good set of instructs can be found at this site: http://rvbuildershotline.com/articles/2008/frame_brace/ so I will only summarize

Following those instructions I used a scrap piece of angle which I drilled to the longeron just ahead of the subpanel. You can see my rough-out sketch on the angle for the final shape.

I drilled a1/4 inch hole through the subpanel and the angle for a 1/4 inch carriage bolt that is 2-1/2 inches long. Then I cleaned up the shape of the bracket with the band saw, belt sander, and scotchbrite wheel.

Here is a view from the aft side showing the head of the carriage bolt which is dome shaped. I also made a mirror image copy of this for the right side. Now I just need to prime the brackets and rivet them on. I’ll set the fore/aft position of the stops later when I put the canopy frame back on.

Next up on the “to do” list is to install the canopy frame reinforcement kit. This requires a homemade tool to bend the edges of the lightening holes in the reinforcement plates. I used some hardwood scrap and made the tool you see below. The first one broke because the grain of the wood was running in the high stress direciont, so I made a second copy with the grain running parallel with the slot. That worked fine.

I removed the rough edges on the parts and created the raised inner lip on the lightening holes as you can see in this photo. It was easier than I expected, working in small steps to gradually increase the angle of the lip to about 20 degrees. This photo shows two of the three plates.

Drilled Canopy Frame Hinge Holes – 6 hrs

Saturday Apr 21, 2012

Oh canopy release mechanism, you have been more of a pain than I expected. I had to remake the links and now I learned that I should not have riveted the hat section to the subpanel until after installing the mechanism. Mounting it requires cutting a slot in the center rib for the link to pass through. There is not a dimension or note on the drawing telling me where to put said slot or how big to make it so I had to figure it out on the fly. First thing I did was mark the rib approximately where the center of the slot should be and I made a hole there just large enough for the link to pass through. That allowed me to place the bearing block where it needed to be and align it with the hat section with the links in line with the pin holes for the canopy hinges. Then I drilled through the #12 holes that mount the bearing block to the hat section.

The bigger challenge was installing the nut plates on the hat section. My options were to drill out all of the rivets that hold the hat section to the subpanel and install the nut plates conventionally, or use pop rivets to install the nut plates. I chose the pop rivet approach because I did not want to risk having oversize holes because universal head rivets are tough to drill out. But pop rivets are 1/8 inch versus the 3/32 holes in the nut plates so I had to enlarge those holes. I know that drilling out nut plates is difficult because the metal is very hard so I used a diamond bit on my dremel to enlarge the holes almost to 1/8 before final drilling with a #30 bit. That worked pretty well. Then I machine countersank the holes in the hat section and assembled it. Fortunately this assembly is not structurally critical so I am not worried about the pop rivets in the least. In hindsight I went back to my March 3^rd post to warn other builders to hold off riveting the hat section.

With that done I was able to gradually begin enlarging the slot through the center rib to allow the mechanism to rotate through the entire range to disengage the canopy hinge pins. It turns out the slot is bigger than I expected. And I had to make a notch in the hat section to permit the clevis pin on the left to rotate by without contacting. You can see the pop rivets in this photo.

Then I put the subpanel back in the fuselage to check that it all works. I don’t have a handle attached yet but it does work if I rotate the bellcrank.

Next I turned my attention back to fitting the canopy frame. I worked for a long time to get the fit of the canopy frame skin to the fuselage as good as I could, then it came down to just drilling the holes for the hinge goosenecks. Other builders have documented the setup very well so I’ll just pick up where I was ready to drill. I used a 12 inch long 1/4 inch drill that I already had from a prior project. I unclecoed the F-771 skin on one side then drilled through the hinge bearing a shallow hole. It’s hard to tell how deep to drill because you can’t see it well. As it turns out I could have drilled a little deeper. When I took the frame off the fuselage I finished drilling the holes to 1/4 using a hardwood block as a drill guide. Here is one side drilled.

Then I enlarged the holes to 3/8 using a new drill bit and pressed the brass bushing in.

Here is a shot with the frame remounted on the fuselage to confirm that it works as a hinge. It does.

Remade C-621 and C-622 Links – 2 hrs

Monday Apr 16, 2012

I was reading through another builders log last week and noticed he was remaking his C-621 and C-622 links because they were too short. His comment was he didn’t notice that the length dimension given on the drawing was from pin hole center to center, not the end to end dimension. I thought how glad I was I didn’t make that mistake, until I checked and sure enough I had done the same thing! Ouch. Both links are 1/2 inch too short. So I ordered two more tubes from Vans and tonight I remade the parts. Still a pain working with this 4130 steel. But if it is any consolation to me, the workmanship on the new ones is a little better than the old ones. This picture shows both sets, the old ones are primed, the new ones are bare 4130.

It was warm and dry tonight so I was able to clean an prime these parts with a can of SEM. Here is how they will be assembled.

I also removed the elevators tonight and put them back into storage. In doing so I took a picture of the trim tab clevis so I can reassemble it later with the same thread engagement to maintain the same trim tab alignment. This is so I can count the exposed threads.

I also took a photo of the little bracket that holds the trim cable under the cover. For the record, the nut was engaged 4 full turns. That is for my records also.

Finished Canopy Hinge Blocks and More – 7 hrs

Sunday Apr 8, 2012

This has been an unusual week. We had relatives in town from Wednesday evening through Saturday night so my work on this project was in little short sessions whenever it was convenient. So this post summarizes all the things I did since Monday April 2.

Tuesday Apr 3

On Tuesday I worked on the C-710 pushrod for the canopy release side handle. The rod must be cut to length, drilled out with a #3 bit and tapped to 1/4-28 on each end. The plans say to cut the length to fit at assembly but there is an overall length provided on the drawing so I cut it a little longer than the drawing. I can trim it a bit later if necessary. As shown below, I drilled the ends and tapped them for the rod ends.

Wednesday Apr 4

On Wednesday I started working on the links of the canopy release. These are a royal pain in the behind because they are steel and you have to drill holes on the ends for cotter pins and slot them for the release pins and release shaft. I drilled the cross holes with my drill press. I marked the locations and drilled with a #40 bit,then enlarged to #30, then #12. You have to be careful to make sure the two holes are parallel.

Here is a shot of the short link with the cross holes drilled.

Then came the trickier part which was cutting the slots. I used a reinforced cutting wheel on my dremel tool for the basic cut. The wheel is about .050 thick and the desired slot width was .060 so this required a steady hand. The first one took a while to cut as I did it very slowly. I finished the slot with a tiny file. More on this later.

Thursday Apr 5

Thursday night I had a little bit of time so I made the spacers for the elevator pushrod where it attaches to the elevator horns. You can see them installed in this shot.

I also took the vertical stabilizer off so I could prime the shims and parts that connect it to the fuselage.

I received the new C-617 UHMW bearing block in the mail today from Vans. The photo below shows the old scrap block beside the new block. It did not take long to transfer drill the two #10 holes from the scrap block. You can bet I was careful to not allow the drill bit to chew up the block the way I did last time. On the drill press I now apply smooth downward pressure while drilling through then shut off the drill before trying to back the drill out. That seems to work pretty well.

Saturday Apr 7

On Saturday I had the chance to finish installing the new C-617 block on the forward fuselage and drill the 1/4 inch hole for the canopy latch pin.

Because I have read much about the trials of fitting the canopy frame I decided to rivet the canopy frame skin onto the weldment and perform and check of the fit with the forward skin. The photo below shows what that looked like.

As expected I found that the skins would not meet leaving a gap of about 0.100 inch as you can see below. It looks like the shims between the C-617 and C-618 blocks is preventing the canopy frame from sliding forward any farther. Not surprising. So I will have to trim about .070 to .080 off those shims to get to the final position. The seal strips are also pretty close so I may need to trim those a bit also.

Sunday Apr 8

Back to work on the canopy release mechanism. I finished slotting the short link. It is 1/8 inch wide on the left for the hinge pin (bolt) and .060 on the right for the crank. Here I assembled the short link to see if it moved smoothly. It did after a little work with the jeweler’s file.

The rest of the time today was spent preparing and priming a batch of parts including the angle and plates for mounting the vertical stabilizer and parts of the canopy release mechanisms. I also primed and painted the F-704K upright cap strips.