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Electrical Planning – 9 hrs

August 25, 2013 1 comment

Sunday Aug 25, 2013

Most of my time this weekend was again spent on electrical planning. I now have 20 separate schematics for the different major subsystems of the airplane such as main power backbone, ignition, VP-X wiring, transponder, autopilot, etc. It was just way too confusing to try to put those all on one schematic so I did it in modules. They are pretty close to done now. I am just cross checking everything and looking for errors. From that I compiled a list of materials I need such as wire, connectors, switches, and terminals. I was stunned when I added it all up and it came to almost $500 worth of new materials? The RG-400 coax and connectors alone total over $80.

After almost a full day of this I was aching to make something with my hands so I took a break from the electrical planning and worked on a couple of small hardware projects. One thing on my to-do list has been to install a quick release detent catch on the copilot control stick. A lot of builders do this for the wife so the stick can be removed for more comfort on long cross country runs. I bought the detent spring from McMaster Carr (P/N 92988A650). In fact I had to buy a bag of five so I have four left over and will gladly mail one to anyone who needs one. All it takes is a 1/4 inch hole drilled through the stick tube and receiver fitting. The detent spring just pops in. I put some heat shrink tubing on the spring before installing it to prevent chaffing on the electrical wires that will run through the tube for the copilot radio button. This view shows the detent spring installed in the tube.

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And this photo shows the tube inserted and the detent snapped into place. It is quite solid.

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I also fabbed a shield for the canopy release switch. I was worried that the microswitch could get damaged by a passenger getting in or out because it was somewhat exposed at the passenger’s right shoulder and that little lever on the switch is quite delicate. The cover is .032 alclad aluminum and it is attached by the same two screws that hold the switch plate to the latch. This photo shows it installed with the seat back pulled forward.

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You can see in this next photo with the seat back in the normal position and the latch open that the switch would be more exposed without the cover. No doubt it will be even better with the seat cushions installed.

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I also mounted the prop (maybe for the final time) and installed the spinner with my newly custom made gap fillers. You can see how nicely they fit in this view. Yes, you can only see one because the other two are on the far side but they all look virtually identical.

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Categories: Canopy Latch Fingers, Prop

Fitting the Latch Fingers – 8 hrs

October 6, 2012 Leave a comment

Saturday Oct 6, 2012

I decided that the next task I would tackle is fitting the fingers (or lugs) for the canopy latch. I was a bit concerned about these because there is no easy way to clamp them in place to verify alignment before drilling and I saw many opportunities to encounter expensive and time consuming problems. Even the plans acknowledge there is potential for error here by tell you to drill the hole to #30 first to allow room for “cheating” the hole centers when enlarging to #12 for the AN3 screws. Having found no good procedure on the forums I came upon the idea of making a dummy lung from wood, fitting that to get lateral alignment and then transferring the hole. At least that would reduce the number of variables to just the up-down alignment to get the hook preload on the lug just right. Here you can see one of the two wood mockups I made. It has a centerline down the middle which I aligned to the hook. Using this tool I found that the holes needed to be shifted slightly to the inboard side on the pilot-side lug to be aligned with the hook on center. The passenger side lug holes were basically right on the centerline.

Then I removed the wood mockups and put the actual lugs in place with the canopy down flush. I had to hold the lug with one hand putting the roller up against the latch hook to get the right up/down position and mark the holes with the other hand through the pre-drilled holes in the canopy frame. Those marks only indicate the hole position along the length of the lug; I transferred the marks from the wood mockups for the side to side locations of the holes. Then I drilled the top hole in each lug to #30 using the center marks and clecoed each lug to the frame at the top hole. That let me check the fit and alignment with the canopy and latch hooks. The fit was a little tight on the pilot side and a little loose on the passenger side so I used a Dremel tool to elongate the #30 holes in the lugs just slightly to balance the fits. I adjusted the lugs side to side to make sure the hooks were in the center of the lug catch and remarked the position of the lower holes in the lugs through the pre-drilled frame holes. I removed the lugs again and drilled the lower holes on the drill press to #30. Here is the pilot side re-installed with clecos.

Then I removed the lugs and drilled the upper holes in the lugs and frame to #12 for the AN3 bolt. I put them back on with the AN3 bolts in the upper holes and tightened them down to hold the lugs for match drilling of the lower holes. Here is the passenger side after match drilling and installing both bolts. After this the fit with the latch hooks was just a little tight on both sides. I biased them that way because I knew I could file just a bit off the latch hooks to fine tune the fit and so that is what I did a little later.

But first I needed to finish installing the latch handle parts. I was not happy with the fit of these parts because the mechanism had a scratchy feel as I rotated it and I was sure something was scrapping. The tell-tell marks on the lever indicated that it was rubbing against the skin at the slots so I used a jewelers file to widen the slots just a bit to make sure they were slightly wider than the gap between the two angles holding the lever. After about 15 minutes of filing and smoothing the edges the mechanism was running smoothly with no scrapping. It really helped when I snugged up the nuts on the pivot bolts for the lever to eliminate the sloppiness in the joint with the angles. Next I riveted the angles to the inside of the fuselage.

I also riveted the two brackets on the bulkhead below the roll bar for the latch linkage. I’m glad these side panels are all painted now so I could do this. I made a “final” adjustment on the length of the linkage rod and installed all the nuts and cotter pins except the one for the latch catch at the forward end because that needs to go on after the channel covers are installed on the F-704 bulkhead.

I installed an edge grip seal along the bottom of the side skirts of the canopy frame (McMaster-Carr part number 1120A812) as a weather strip. It fits nicely along the whole length except at the aft end (shown below) and at the doubler plate on the side skirt.

At those locations I put a self-adhesive foam bulb seal to close up the gap (see below). At the aft end I used two pieces of McMaster-Carr P/N 93085K67 to seal the gap. Along the doubler I used McMaster-Carr P/N 93085K11.

These seals must be compressed slightly to seal the gap so it takes a little force to pull the canopy down the last 1/8 inch or so. I filed the latch hooks just a tad to where they don’t bind without the seals installed. With the seals in place you can feel a little resistance as the hooks pull the canopy down to the latched position and the latch lever goes over center. I like the action a lot. It has a nice smooth quality feel to it with just enough resistance to give confidence that everything is latched.