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More Baffle Seals – 6 hrs

April 6, 2013 Leave a comment

Saturday April 6, 2013

Some of the seal pieces turned out to be pretty odd shapes. This is one example. I’m glad I mocked this up in paper templates before cutting away on the rubber sheet. You could waste a lot of rubber sheet experimenting to get a good fit.

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My friend Scott came over to lend a hand this morning. We finished up all the rubber seals around the ring gear section.

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Here is a dumb picture of me. Scott insisted that I don’t have enough pictures of myself working in the airplane in the blog.

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Here is some detail of the rubber strip segments cut to fit around the inlet ducts. This was the hardest area to get a good fit.

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Here is another view of the left inlet duct. Notice how the strips overlap.

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And this is the right side…

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And the right inlet duct near the ring gear…

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We also worked on installing the control cable for the AFP fuel injection purge valve. I bought a 60 inch long cable from McFarlane for this. It runs from the valve through a hole in the baffle on the left rear side.

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I made a special bracket to anchor the cable to the crankcase using some existing hardware. I wrapped silicon tape around the cable to allow it to be securely gripped by an adel clamp.

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The cable exists the baffle through a snap bushing and then passes through the firewall through a stainless steel eyeball.

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From there it is a direct run to the panel. The purge valve control is just to the right of the mixture knob. The control is a push to unlock cable so you have to deliberately push the button to move the control. Sixty inches was just barely enough. Two more inches would have been good but the standard sizes are in one foot increments and 72 inches would have been much too long.

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Riveted Cowl Hinges – 8.5 hrs

February 24, 2013 Leave a comment

Sunday Feb 24, 2013

It took more time than I expected this weekend but I finally bonded and riveted all the hinges onto the cowl. This included machine countersinking all the holes on the outside of the fiberglass cowl for the rivet heads. This is a bit tricky since the surfaces are curved and the radii change so I checked the depth of every countersink. That took hours. I also sanded the mating surfaces on the cowl and scuffed up the mating surfaces on the hinges with coarse sand paper to give the epoxy something to bite into. And before applying the epoxy I cleaned all surfaces with acetone. Applying the epoxy was challenging. Too much and it squeezes out into the spaces between hinge eyes; too little and the bond is weaker. I completed the lower cowl on Saturday and the upper cowl on Sunday. The only clecos that remain are for the oil access door.

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Here is a closeup of the flush rivet heads on the outside surface of the upper cowl. I used flocked cotton fiber in the epoxy to give it more strength and to add viscosity. I put clecos in every other hole first, then riveted the remaining open holes. Next I removed the clecos and finished riveting the rest of the holes.

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I was out in Corona flying on Saturday and stopped by Aircraft Spruce to pick up some supplies including some all metal lock nuts I needed for the control cable brackets.  I took the FI servo off the sump and installed those nuts so this is good to go now. I also picked up some 1/2 inch fire sleeve. I used a short piece of that to cover the mixture cable where it is closest to the left exhaust pipe/heat muff. It just covers the non-articulating part of the cable as well as the rubber boots that keep out moisture. You can see it in the view below.

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You can see it better in this view taken directly below the engine looking up. This also gives a better representation of how far away the cable is from the exhaust. I secured it with a high-temp zip tie near the mounting bracket. The other end is completely free.

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Categories: Control Cables, Cowling

Cowl, Oil Door, Exhaust, etc. – 9 hrs

February 17, 2013 Leave a comment

Sunday Feb 17, 2013

It’s been a very busy weekend. I didn’t have as much time as I wanted to work on the airplane because I had to replace and paint some base molding that was damaged by a water leak recently but I got quite a bit done anyway. First, I trimmed and sanded out the epoxy and microlight filler layups I placed a few days ago in the outer nostrils of the air intakes to make flanges. As you can see it turned out pretty well. Not ready for paint but good for a first cut. The rest is just making it prettier.

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I also sanded the epoxy layer I added to the inside of the oil door. This is ready to prime and seal, then I will rivet in the latches.

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Another recent mini-project has been the lower cowl brace which I primed and assembled yesterday. Here are the parts ready for installation.

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I called Clint at Vetterman Exhaust last week and asked him about the unused heat muff in the exhaust system. Since I plan to use only one heat muff the other will not have forced air. I read somewhere that if left uncooled it will get very hot and could damage the cowl. Clint recommended three options; 1) duct air to the muff to cool it, 2) take the outer shell off the muff to allow air flow around the muffler, or 3) replace the muff with a bent sheet of aluminum alclad that wraps only half way around the muffler. I chose option 3 as you see in the photo below. With half the shell open the muffler should not overheat and the aluminum shell will act as a thermal shield to protect the mixture cable which is right behind it.

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Installing the lower cowl brace was a pain in the neck but as you can see in this picture I got it in. I also bent and fitted the final hinge wires for the lower hinges. These wires have long “handle” extensions that overlap the center brace and then poke through holes in the lower brace to retain them. You can see them if you look carefully on either side of the brace. Something else I did was rivet the cowl hinges to the sides and bottom of the fuselage.

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With the lower cowl and cowl brace installed I was ready to finalize the positions of the exhaust pipes. As you can see above, the pipes come fairly close to the cowl, engine mount tubes, and the edge of the fuselage. Each exhaust pipe has a slip joint right in front of the muffler that allows the aft section of the pipe to be rotated to “aim” the joggle for best fit and clearance. I tweaked the pipe alignment about as much as I could and when I thought I could get it no better I decided it was time to lock it down. The aft section of each pipe is locked to the front section with a split collar with  1/4 inch diameter internal pin. You have to drill a 1/4 inch hole through the joint for the pin and then clamp it together with an AN3 bolts and lock nut. I mustered my courage and drilled. In this next photo you can see the clamp installed one of the slip joints.

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The next few photos are just to illustrate the exhaust pipe supports and clearances to various critical components like control cables and fuel lines. It is hard to see in two dimensional pictures but everything seems to have reasonable clearances. The forward supports for the exhaust pipes connect to engine sump bolts. There is also a horizontal support that ties the two pipes together.

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In this view you can see the right side.

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I recently ordered a longer fuel line (part number VA-139) because the “standard” one that came with the kit would not reach to the AFP fuel servo inlet. As it is, the VA-139 is just barely long enough.

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This photo gives you an idea how much clearance the throttle cable has to the engine mount and exhaust. I also ordered a 46.5 inch long throttle cable from Vans because the standard 44.5 inch cable was a little tighter than I liked under the panel. The 46.5 inch cable allows for a more slack routing.

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This photo gives a good view of the mixture cable and it’s clearance from the exhaust. I may put a fire sleeve around the mixture cable to further protect the rubber seals from the heat.

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Back on the cowl I drilled holes in the hinges for bonding. These holes will improve the strength of the bond according to Vans. I used a 3/16 drill because the 1/4 inch holes recommended in the plans looked too big to me. Since the extra holes are called “optional” in the plans I figure I have some latitude here.

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Finally, I started work on hinge pin covers for the horizontal cowl hinges. I sketched six round patches on a piece of 8 oz Rutan cloth. These sketches are about 2.5 inches in diameter which will give some margin for 2-inch cover plates.

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I placed this between two pieces of plastic drop cloth, poured in some epoxy, and rolled it out to make prepreg cloth. After I cut the round patterns out with a roller knife I applied packing tape over the hinge pin access area and laid up three layers of prepreg on each side. I will let this cure to make stock for 2-inch access covers.

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Completed Control Cables (I think) – 4.5 hrs

December 29, 2012 Leave a comment

Saturday Dec 29, 2012

I continued to make incremental progress today on the firewall forward tasks. I needed to install the second firewall penetration so I knocked that out. I hate drilling the stainless steel firewall because it is tough on drills but it must be done. I start by drilling a 1/8 inch center hole that I enlarge with a 1/4 inch cobalt drill. Then I used a unibit to enlarge it further to 7/16. The shaft of the hydraulic punch is just under 7/16 so I set that up with a 1-1/8 inch punch and it does the rest of the job. Here you can see the punch head installed just before I pumped it up to cut a nice clean hole. Actually I leaves a slight ridge on the inboard side of the firewall but that cleans up pretty easily.

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Here is the pass-through fully installed on the pilot’s side. Ready to receive wires!

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Next I made a new control cable bracket for the fixed pitch configuration (no blue knob) and match drilled holes to attach it to the bottom lip of the panel. It is clecoed on for now.  I will install nut plates later. I replaced the temporary bracket I had been using to lay out the cable runs and routed the throttle and mixture cables to the servo.

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I think I am done with this task now so I applied blue locktite to the screws that hold the servo adapter plate to the sump and torqued them. Then I mounted the servo and installed the lock nuts and torqued those also. I could not get a crows foot on the nuts so I used my fish scale to apply 120 in-lbs of torque using a 5 inch radius arm on the wrench. That is, I applied 24 lbs of force x 5 inches = 120 in-lbs. I installed the mixture cable with all the hardware including the rubber seals which I had removed for all the routing activity over the last few days. Here is a “final” view of the mixture side.

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And here is a “final” view of the throttle side. My only reservation now is the exhaust system and the hangers that will be used to support it. I just hope they don’t interfere with the cables and brackets I worked so hard to fine tune. I expect the exhaust to be delivered any time now since I ordered it a month ago from Larry Vetterman. I hope I don’t get surprised.

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Throttle and Mixture Cables – 5 hrs

December 27, 2012 Leave a comment

Thursday Dec 27, 2012

Before describing the main accomplishments for today I want to start by showing one of my Christmas presents – a set of rudder pedal extensions from JD AirParts. These are not necessary accessories but I think they look good and will be functional. Here are the two extensions; nicely machined and anodized aluminum.

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They were installed in no time requiring only a hex wrench to attach them to the pilot’s rudder pedals.

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The bigger accomplishment today was completing the routing of the throttle and mixture cables from the panel to the FI servo, including locating the firewall penetration for the mixture cable. I started by making a temporary hanger for the control knobs. It is temporary because I wanted a way to lay out the cables so I could upgrade later to a constant speed prop so I laid out the spacing based on three controls with the prop control in the middle. The actual hanger will only have the throttle and mixture holes so they will move closer together. I used .025 aluminum sheet to make this hanger because I had some on hand. It should actually be .040 or thicker for the real thing.

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Now for a description of the routing. Looking under the panel you can see that the throttle cable runs down under the rudder pedal bars to the penetration near the fuel line fitting. This cable is 44.5 inches long – probably adequate but I may exchange it for a slightly longer one. I think a couple of inches longer might be better. The mixture cable routes over to the firewall recess where I mounted an eyeball penetration on the left side near the bottom of the sloping surface.

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The throttle cable exits the firewall next to the nose gear mount and is almost a straight shot right to the FI servo. To gain extra clearance between the cable and the engine mount tube I tilted the gold bracket inboard about 5 degrees from the “stock” AFP design. I had to drill an extra hole in the AFP-provided part to do this.

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Here is a closeup of the throttle arm. Note it is mounted in the hole with a smaller radius from the pivot point. This is necessary because the control cable does not have enough travel to accommodate the larger arm radius.  This view is in the WOT position.

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This view is in the idle position. The geometry of the cable and the joints all look good.

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This next view is looking back along the path of the control cable. You can see the spacer between the spherical bearing and the control arm (which is 35/64 long) and the clearance between the cable and the engine mount.

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The mixture cable exists the firewall in the recess and turns down along the oil breather tube where I will secure it with standoffs later.

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The mixture cable then turns forward to the bracket I made to mount to the gold AFP bracket. I tilted this AFP bracket inboard a little also by drilling a new hole in the AFP bracket at the angle that gave about the same clearance at both engine mount tubes that the cable passes. This bracket is clecoed on right now but I plan to drill it out for AN3 bolts.

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Again, a closeup in the full rich position.

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And here it is in the idle cut-off position. I am happy with the geometry here also. both cables operate smoothly.

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And here is the view from the front looking down the cable. The spacer on this side is 3/8 inch long which seems to be about optimal.

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Last but not least, I removed the plug in the #3 cylinder and installed the manifold pressure fitting and hose. This hose will be routed to the manifold pressure sensor and the two P-Mags. I also installed the oil filler tube although I have not torqued or safety wired it yet. I want to make sure there is no need to remove it for access before I take that step.

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