Installing ANL Current Limiter and Shunt – 3 hrs

Tuesday Oct 30, 2012

This mini-project is to mount the ANR current limiter and ammeter shunt to the firewall. The ANL current limiter is recommended by Bob Nuckoll’s book “The Aeroelectric Connection” and I ordered it from B&C Specialty Products. The ammeter shunt came with the Dynon engine sensor kit. I laid out the parts on the firewall in a configuration that is conducive to wiring and works with the stiffener rib structure on the other side of the firewall. The shunt is wider than the current limiter so I put it beneath the current limiter base and aligned one of its mounting holes with the center of the stiffener rib and half way between two existing rivets. The current limiter base is placed such that it is in line with the terminal on the starter contactor and the left ANL post is directly above the left terminal of the current limiter. I marked the screw locations on the firewall and drilled the holes for #10 screws. The screws did not come with the electrical parts but I decided to use socket head cap screws for the shunt and I found some stainless steel 82 degree flathead screws at the hardware store that should be fine for the current limiter. Here is a photo of the parts temporarily mounted to confirm the locations.

Then I made a .062 doubler plate to go on the aft side of the firewall to back up the three holes that are not through the rib. This doubler will also support nut plates. I added a couple extra #40 holes for additional rivets in the corners. In this photo it is placed on the front of the firewall for drilling but will be installed on the far side.

Then I cut pieces of copper bar to electrically connect the starter contactor to the current limiter and shunt in series. This is basically how it will look when installed. The lower right terminal of the shunt will be connected to the alternator so this is the electrical path for current to flow from the alternator to the battery and main power bus. But I still have to prime the doubler and install it on the firewall with the nutplates before final installation.

Installed OAT Probe – 3 hrs

Sunday Oct 28, 2012

Today I installed the outside air temperature (OAT) probe in the aft fuselage. I chose to install the probe beneath the horizontal stabilizer on the right side where it will be out of the sun, in the air stream, and relatively safe from harm. The is one of the two most common locations, the other being under the wing, but I chose this location because I didn’t want to add another connector at the wing root. I drilled a 3/8 inch hole through the skin about 2.5 inches below the aft deck. The probe comes with the Dynon ADAHRS module and it just slips into the hole from the outside with a nylon nut and washer on the inside to secure it.

I ran the wires through the conduit on the right side to the bulkhead just behind the ADAHRS. The wires exit the conduit there and are routed along the edge of the bulkhead similar to how the static air lines are routed further back. At the top the wires branch off to the back of the ADAHRS where the connector is located. I put a glob of clear silicone sealant on the wires where they exit the conduit to prevent chaffing. It can be easily removed if necessary for maintenance.

In the tail cone the wires are routed from the probe right into the conduit with a tie base used to secure it. Very simple and quite clean.

Installed Dynon ADAHRS – 6 hrs

Saturday Oct 27, 2012

A bunch of goodies arrived in the mail on Thursday including a Dynon ADAHRS module, an engine sensor kit, and a 20 foot network cable. I ordered the ADAHRS so I could get it installed before permanently bonding the rear window in place with SikaFlex. I ordered the engine sensors because I need to start installing those before hanging the engine.

 

The ADAHRs module is surprisingly small and light. I installed the pneumatic fittings from the SafeAir1 kit.

 

Today I installed and aligned the ADAHRS module on the bracket I built and installed behind the F-706 bulkhead. Right now I am wishing I had done this before riveting the top forward skin because getting back here to do this now is a pain in the … just about everywhere. But I got it installed with brass screws, washers, and nuts I picked up at True Value Hardware. I also installed three nutplates for Adel clamps for the cable and that was even more difficult in this confined space. I had to do the work laying on my back on a piece of plywood laid across the bulkheads. I still need to provide a means to secure the cable coming down the center rib.

 

I then installed and routed the pitot and AOA tubes to the ADAHRS and secured those temporarily with zip ties to the center rib.

 

At the bottom I was concerned about the lines interfering with the elevator bellcrank so I designed and fabricated a simple bracket to go over the bellcrank to which I can attach the plastic lines. It is made from .025 alcad and is very light but stiff. I will pop rivet this in place after I prime it. It allows the plastic lines to run with a smooth bend to the entry of the conduit under the pilot’s seat.

 

While I was there I installed all the bolts and washers for the bellcrank and servo linkage, hopefully for the last time. I had to make a homemade washer holder to install one in the lower position on the bellcrank. Here is my impromptu tool.

Repacked Wheel Bearings – 1.5 hrs

Wednesday Oct 24, 2012

I originally hand packed the main landing gear tapered roller bearings with grease  but I had lingering concerns that they may not be fully packed. After all, I’m not an experienced packer. So I ordered this Lisle bearing packer from Amazon for about $10. A good investment in my book. I also ordered a grease gun which I need to fill the nose gear swivel bearing anyway. I could have bought a grease gun at Home Depot for $15 but the one I bought is way better quality for $18.

The packing process is simple. You sandwich the bearing between the upper and lower cones and then pump grease into the bearing through the center screw with a zerk fitting attached.  When you see the grease oozing out between the rollers the bearing is packed.

I also decided to modify the right F-745 rib of the front fuselage structure to permit the installation of a second 10-inch Skyview display. So I cut the rib at the front surface of the sub-panel and touched up the edge with paint. When I clecoed the rib back into the fuselage it made it symmetric with the left side. So later I will make angles to mount the remaining aft sections of the two F-745 ribs to the subpanel closer to the centerline between the Skyview and the radio stack.

Canopy Prep – 2 hrs

Sunday Oct 21, 2012

Today I spent some time planning out the build process for the near future. It is quite a dilemma trying to determine the best order to do things in this phase. I decided that I needed to adjust the clearance between the front and rear canopy sections. It is currently about .020 or less but I know that more gap is needed to prevent the two pieces from binding when the temperatures go up. The plans say .032 is the recommended gap and others on the forum have said it may need more. So I set about to adjust it to about .032 for now. I can always increase it later if necessary.

It took about 5 or 6 iterations of sanding and checking to get the gap right. Here is a photo looking down the seam across the top of the canopy. I think it looks really cool.

My plan is to install the Dynon ADAHRS in the aft fuselage and then SikaFlex the rear window. The ADAHRS will be easier to install without the rear window in place.

I also need to mount the ANL current limiter I bought from B&C Specialty. This is basically a high current (60 A) fuse. But I also need to mount an ammeter shunt in this area and I’m not sure exactly where to place each one so for now I bent one end of a copper bar and drilled a hole for the starter contactor terminal but I will wait to locate the currently limiter holes until I get the shunt which comes in the engine sensor kit from Dynon. I will order that tomorrow. Here is the copper bar yet to be cut to length with the current limiter base just stuck against the firewall but not drilled.

Finished Riveting Top Fuselage Skin – 3 hrs

Saturday Oct 20, 2012

Working solo today I finished riveting the top forward skin on the fuselage. The rivets I shot were the vertical column on the left over the top and the horizontal row illustrated below by the red arrows.

The three forward-most rivets on each side are pulled Cherrymax rivets because there is no way to get behind there to buck solid rivets.

I also installed the brake line fittings on the calipers using some Loctite 567 sealant on the threads.

Air Vent Mounts – 4 hrs

Friday Oct 19, 2012

My next mini project is making and installing the air vents in the cabin. I bought the small Steinair vents a while back but have not gotten around to installing them. So now is the time.

I looked at how some other builders had mounted them to get a general idea of the parts I needed to make then I made a cardboard template for the main faceplate. That let me get the shape refined before I cut metal. I made the faceplates out of .032 Alclad sheet and the two angles are 3/4 x 3/4 x .032. Unfortunately I found that the ring nuts on the vents require a minimum panel thickness of about .065 so I had to make two spacers to thicken the grip. Here are all the parts for the installation. I drilled the angles to the faceplates first, then drilled the angles to the side skin of the fuselage with the parts in place.

 

Here is how the mounts are assembled. The spacers fit under the ring nuts of the vents.

 

This is how they will look installed. The angles will be riveted to the side skin and the faceplate is held to the instrument panel with one screw.

 

I still need to prime the parts and paint. Then I can rivet it all together and install the SCAT tubes to the NACA inlets.

Installed Nose Wheel – 1 hr

Tuesday Oct 16, 2012

You may have noticed in my last post that the nose wheel was missing. That is because I decided to send it out to Anti Splat Aero in San Bernardino for a wheel bearing mod. The stock bearing setup has been widely discussed on the Vans Air Force forums and some of the shortcomings of the high rotational drag and the effects it has on wheel shimmy. The drag is partly because of the bearing seals and partly because there is no rigid axle, only an axle bolt that passes through the wheel. The bearing preload is dependent on how much torque you put on the axle bolt.

I also learned that the tires are often out of balance and out of round which also contributes to shimmy. The Anti Splat Aero mod replaces the tapered roller bearings with a pair of sealed ball bearings and a rigid axle spacer that allows you to torque down the axle bolt fully without changing the bearing preload, and the bearings are supposedly lubricated for life. Anti Splat Aero also dynamically balances the tire on the wheel and shaves off the outer surface on a lathe to true up the tire relative to the rotation axis. Both of these should make the tire roll much smoother on the tarmac.

You can do you own research but I decided it was worth $250 plus shipping to get this mod done now. I just don’t want to deal with shimmy during flight test. Here is a photo of the wheel as it came back from Anti Splat Aero (by the way they turned it around in one day so my wheel was gone less than a week including shipping time). The spacers were also modified to fit the new bearings.

I checked the torque on the wheel nuts, set the time pressure at about 35 psi and installed in the wheel fork.

Then I installed the gear leg into the fork and just made the nut snug. I need to get a grease gun to pack the swivel bearing and then set the preload to the proper level per the instructions before drilling the axle for the cotter pin.

Nose Gear Work and Fuselage Skin Riveting – 6.5 Hrs

Sunday Oct 14, 2012

Here is a summary of the weekends work activities. I started with the U-630-1 front wheel fork. This part needed some deburring and scuffing to prepare it for painting. I also masked off the threaded holes and the bearing hole to keep the paint out of there.

Since I was getting ready to shoot primer I prepared the U-713C brackets which are used to mount the wheel pant. This required a modification to cut the wide slot down the middle of each part. In addition I deburred and scuffed the U-810-L and -R, and the U808 (2 ea) which are brackets for the main gear wheel pants.

I fired up the pant gun and sprayed a good coat of Ekoprime on the surfaces. Here are the parts after they had dried for an hour or so.

 

Later I picked up a can of Rustoleum high performance white enamel to paint the front gear fork. This part will be exposed to the elements and if I don’t install the wheel pants before first flight will be visible for a while so I wanted to paint it to match the gear strut, more or less. The Rustoleum fit the bill because I did not want to spend a load of cash on getting it powder coated. Here is a shot of the fork after painting. I left this to dry over Saturday night.

 

Sunday morning I assembled the fork and U-713C brackets along with the axle bolt and the two screws that are used as rotational stops just to make sure everything fits together OK.

 

The canopy latch fingers are alloy steel so I painted them with Jetflex to match the interior paint. Those dried over night also and I installed them with the lock nuts this afternoon. I 

 

Later Scott came over and we did some riveting on the top fuselage skin. I need to get this section done in order to complete the installation of the rear window. The down side is now it will be harder to work in the aft fuselage cone because I will have to crawl inside for everything like installing the ADAHRS. Oh well, the price of progress. We riveted everything up to the F-706 bulkhead which I can probably finish solo.

Safety Latch, Part 3 – 1 hr

Tuesday Oct 9, 2012

To complete the safety latch installation I made two strips of 1/8 inch thick UHMW plastic, 3/4 wide. One is 6 inches long and the other is 2-5/8 long. I laid out four holes on the longer strip and drilled #40 pilot holes. Then I aligned that strip to the center of the roll bar with the front edge flush to the face of the roll bar and match drilled holes in the roll bar. In the photo below that part is clecoed in place.

I enlarged the holes in the roll bar to #29 which is the tap drill size for a #8-32 thread. I tapped the holes in the roll bar next and enlarged the holes in the UHMW to #19 which is the clearance hole size for the screws. I also match drilled two holes through the short UHMW srtip using the longer strip as a guide. With my countersink cutter I countersank two holes on the long strip (right side) and the two holes in the short strip for flush flat head screws.

Here is how they are installed (below). I used four #8 screws from the finishing kit which I’ll have to replace. The short strip overlaps the long strip providing a bumper stop for the latch handle.

Here is how it works. With the canopy closed and the latch handle unlocked the canopy is free to open. The spring in the handle provides a little friction between the handle shaft and the UHMW block that helps resist any tendency for the handle to rotate by itself. That is a nice added benefit of this design.

If the handle were to rotate by itself with the canopy closed (such as while moving the airplane with a tow bar) the edge of the handle will bump against the edge of the longer UHMW strip preventing it from going under the roll bar. This avoids a very awkward problem of a locked canopy with no one inside. The photo below shows the latch handle in that position. I verified that the canopy opens and the handle doesn’t catch on the roll bar because the front edge of the UHMW is flush with the roll bar.

To latch the handle for real you simple pull down slightly (.16 inch) and rotate it to the fully locked position. The handle slides under the long UHMW strip and bumps up against the edge of the short strip which lets you know without looking that it is all the way home. Ready to fly! Plus the UHMW strips prevent the paint from getting scatched up on the bottom of the roll bar.

As far as I am concerned this solution looks nice, feels solid, and fixes a nasty flaw in the stock design. I credit Dave B. on Vans Air Force for the basic idea which he posted in 2007. I modified the approach with a stiffer spring partially counterbored into the UHMW block and I added the bumper stop. If you like it, of course you should feel free to copy the design.