Installed Red Cube – 2 hrs

Thursday May 30, 2013

After some consideration about where to mount the “Red Cube” fuel flow sensor I decided to contact Don Rivera and Airflow Performance for a recommendation. He sent me a few photos showing the sensor mounted on the engine mount near the right lower Lord isolator. That looks like it will work with my set up so I made an aluminum plate and attached it to the engine mount tubes with two adel clamps. In order to give the fuel line more clearance to the engine mount gusset I made a spacer from 3/4 inch thick HFMW to go under the Red Cube. This photo shows the spacer and the steel AN fittings I installed in the Red Cube.

Here is the Red Cube installed on the plate which bridges across two engine mount tubes. Now I can measure the length of the fuel lines that go between the AFP servo and the Red Cube, and the Red Cube to the fuel spider and get those on order.

Making the FAB Intake Seal

Monday May 27, 2013

Making the rubber seal that couples the filtered air box to the cowl intake is tricky business. The shape of the FAB opening is such that the seal must be tapered toward the front so a straight strip of seal material does not fit well. I needed to determine a good shape for the seal strip that fits my air box so I made a paper template first. It took several iterations but I got to a shape that lays down against the side walls and overlaps the air box by 0.7 inch. I am using a 0.4 inch gap between the air box and the cowl intake and another 0.7 inch overlap with the cowl intake for a total span of 1.8 inches. Here is the paper template taped in place.

The shape turned out to be an arc which is not a big surprise. Ignore that little chamfer in the upper left corner. That was a mistake.

I could not use the stock rubber strip from Vans because it is a straight strip, 1.8 inches wide, not a arc. I order a 12 x 12 piece of .062 thick Nitrile rubber from McMaster-Carr as a replacement. I cut the arc strip using my paper template and taped it into the air box for a trial fit. It looks like it will make a good seal if I make some RTV fillets in the top corners.

I put the cowl on to see how it looks from the outside where the cowl intake will mate to it. I debated attaching the seal to the air box but that had two major drawbacks. First it would leave the seal hanging out on the air box when taking the cowl off which will make it harder to clear the cowl. Also, it would put the unattached edge of the seal strip upstream in the air flow so it could curl up and block the air flow (not good). So the seal will be securely attached to the air intake and the internal pressure will force the seal against the internal walls of the air box for a good seal.

The next step was to make the seal fit to the air intake. I don’t have pictures of the process but I can say that it took several iterations of trimming, shaping, and laying on more fiberglass to get the seal to fit well. The original tunnel I made using the Vans process did not fit well so I cut off the last 0.7 inch and formed a new one. And I contoured it internally to provide a smooth tunnel for the air flow while externally it is shaped to sit flush to mate flush to the conical shape of the seal. Here is the modified air intake with a new seal strip I cut with some tabs that I will explain later.

This is how the seal strip fits onto the air intake. I drilled for rivets but I am thinking about other ways to attach this that don’t require rivet heads inside the tunnel.

Cowling Air Scoop Mod – 8 hrs

Saturday May 18, 2013

I have been debating with myself for weeks whether to make a modification to to the cowl air intake that I think will make installing the lower cowl more easy. Today I decided to go for it. I was remembering something Dan Horton wrote on the online forums about fiberglass work. In essence he said the nice thing about fiberglass is if you make a mistake, you can just do it again. You can pretty much patch up any thing you don’t like. So I concluded if this doesn’t work out, I can just patch it up like it was before and you won’t see the difference (after paint).

So I survey out the nose of the air intake, measuring and making marks for a cut line. I added a piece of electrical tape around the snout so I could visually confirm that the cut line looked good.

Then I began cutting with a thin cut-off wheel on my dremel tool. Ouch, it reminds me of circumcision for some reason.

The cut was fairly clean but I sanded the edge of the snout piece to become the finished edge of the removable snout. I also sanded the cowl edge but that will be filled in later with micro to give a clean finished joint. This photo shows the interior of the snout piece. I line it with packing tape for the next step which is to mold a flange on the cowl piece to mount the snout with nutplates.

Here is the tricky part. To align the two pieces I used a few dabs of hot glue in the joint. Remember, the cut-off wheel took out some material so I don’t want the two pieces to be in direct contact. I want the gap to match the material removed as close as possible. I use shims initially to account for the material removed but I took those out after I got the snout tacked in place.

Then I flipped it over and laid in three layers of fiberglass cloth across the joint. this will be my flange that will hold the nutplates for the snout.

About five hours later the epoxy was set (it was warm today) and I pulled the snout off. I had to cut the hot glue out and the snout was held pretty tight by the packing tape, but once it started to peel off the snout came right off. I trimmed the upper edge with the cut-off wheel to leave a  5/8 inch wide flange and I sanded it all to clean it up. This is looking promising.

I put the snout back on and applied a little micro along the joint to fill in the gap and after that set up I sanded it out and now the joint is looking pretty clean. Here it is with the snout just sitting in place. The fit is very good because the flange was molded to the interior contours of the snout.

I marked the snout for six screws and drilled #40 holes for now. These will be #6-32 flat head screws later.

So after the first day on this mini-project I have the snout cut and fit to the cowl with its mating flange molded.

Here you can see how it clears relative to the air seal tunnel.

And with it installed the joint is almost invisible from more than 10 feet away. The joint will get wider later when the cowl is painted but it is good to start with a clean fit.

The next step is to install the nutplates and screws to hold this together. First I drilled the holes out to #27 for #6 screws. I don’t want the nutplates to pull out so I made some backing strips out of .032 aluminum stock, .50 wide by 1.0 long to reinforce the fiberglass.  I located the reinforcement strips behind the cowl holes with some #6 screws and free running nuts and epoxied them in place. I’ll let this cure up then install the nutplates on them.

Update 5/20/2013 – Tonight I cleaned up the excess epoxy on the aluminum backing strips and installed five nutplates on the cowl flange.

Then I secured the snout with 6 lobe flat head screws I purchased from Micro Fasteners. I hate phillips head screws because they strip so easily. The lobe drive screw heads are much less prone to strip.

This mod turned out better than I had hoped. I’m glad I did it now. I think this part is ready for primer.

Manifold Pressure Lines – 6 hrs

Thursday May 16, 2013

The PMags each have a pressure port that needs to be connected to the engine manifold pressure line. I had installed the hose from the engine to the firewall recently but I had not yet hooked up the manifold pressure sensor or the PMags. The PMags came with a piece of black silicone tubing that fits the PMag port so I installed that with a T (McMaster-Carr part number 53055K171) and routed it along the engine mount with adel clamps to the pass-thru port on the right as you can see below.

 

Once through the firewall I installed another T to split off to the Dynon manifold pressure sensor and the firewall fitting from the engine. The fitting at the firewall has a small orifice and the clear plastic line there is quite small to help smooth out pressure pulses in the line. The adapter to connect black PMag tube to the larger clear tube that came with the manifold pressure sensor is McMaster-Carr part number 53055K127.

 

On other fronts I drilled the two rails for the VPX box to the ribs in the forward fuselage. Clecos installed for now.

 

I also installed adel clamps to hold the oil breather tube securely above the exhaust pipe.

 

While I was having fun I installed the cylinder head temperature probes into the ports on the engine. I used a little anti-seize compound on the threads.

 

And finally I installed the fuel pump drip line according to the instructions.

Attached Alternate Air Door – 2 hrs

Sunday May 12, 2013 (Mother’s Day)

I mostly took a break today from the build because it is Mother’s Day but I did do one thing and that was to install the alternate air door on the filtered air box and attached the cable. To make sure I had the right location for the Adel clamp on the air box I first finished the routing of the cable along side the mixture cable. I used zip ties to lace them together along the firewall. Then the point on the FAB for the Adel clamp became clear. I installed a #10-32 nut plate inside the air box. To cut the cable I pulled the wire back out about 18 inches then cut the outer sheath using a dremel with a cut-off wheel. Then I pushed the wire back through, wrapped it around the screw three times and trimmed off the excess length. When I operated the door from the cockpit I was pleased to find that it opens smoothly and it even closed properly when I push the knob back in, something that it is not guaranteed to do. In most cases they say you have to remove to cowl to reset the door.

Various Tasks – 5 hrs

Saturday May 11, 2013

Today I worked on a variety of small projects, trying to wrap up loose ends. My first activity was to make some custom parts for the P-Mag blast tubes. I saw a thread on VAF about how to route and secure blast tubes from the engine baffles to the P-Mags. An interesting idea was to wrap safety wire around the P-Mag body and route it though the blast tube into the engine baffle compartment. That keeps the tube pointed right at the point of the P-Mag where the wire wraps. I gave it a try and it worked well but there was nothing to attach the safety wire to in the baffle compartment. So I designed some interesting little parts to secure the wires to. They are made of two round pieces of .025 aluminum with a 1-inch hole in the center. Two of these pieces are riveted together on one side and the other sides are bent outward to make a little bridge that goes over the blast tube hole without blocking it significantly. Here is one during a check of the fit over the blast tube.

I made two of these parts, one for each P-Mag blast tube. I primed them and painted them red to match my baffles. I also primed and painted the alternate air control bracket while I was doing paint.

So here is the right blast tube with the safety wire wrapped around the P-Mag and routed through the blast tube.

I put the new bridge part on, pulled the safety wire tight, and wrapped the it around the bridge. That all there is to it. The parts is not riveted to the baffle or attached in any way. The tension in the safety wire keeps it tight against the baffle.

Next I  riveted the alternate air control knob bracket to the forward bulkhead and re-installed the control cable. I put a short piece of edge grommet material on the bracket in case I have a tendency to hit it with my leg.

This picture shows that I also finish primed the fiberglass air box, painted it and the top cover, and riveted the subassembly together. Black goes with the AFP servo.

Here is the filtered air box installed on the servo. This is almost done. I just need to attach the alternate air cable and finish the rubber seal strips on the front opening.

Last but not least I drilled a hole and installed the manifold pressure line in the firewall. I used two Adel clamps to hold the line to the engine mount.

Installing Alternate Air Control Cable – 2.5 hrs

Tuesday May 7, 2013

I started out to install the control cable for the alternate air door on the FAB. The obvious question was how to route the cable and where to mount the knob. I don’t really want this control to be accessible to the right seat passenger because the cowl has to be removed to reset the door if the knob is pulled. If the alternate air door needs to be opened, the pilot should be the one to do it. So I decided to put the knob under the subpanel on the left. It can be easily reached by the pilot but is not anywhere close to the cabin heat knob which looks almost identical.

The cable routing is trickier. I could not find any information on the forums for my configuration so I had to figure this out myself. After considerable head scratching I decided to route it through the firewall recess directly above my mixture cable. Then the cable turns downward along side the mixture cable and then turns forward to the bottom of the air box. Once I settled on that I became concerned that it might interfere with the VPX-Pro control box so I had to temporarily mount that to check for interference. The photo below shows the VPX on two .063 angles approximately 19-5/8 long. This is just held to the ribs by cleco clamps right now but it gave me enough confidence to proceed with the cable installation.

I made a small bracket out of .040 aluminum to mount the knob to the left bulkhead just beneath the cool air vent scat tube. Then I punched a hole in the firewall recess directly above the location where the mixture cable feedthru was placed. Installed there an eyeball feedthru with a .188 diameter hole which fits the alternate air cable perfectly. In this photo you can see how the cable routes in an S bend above the rudder pedals.

Here is a view from above after I added a couple of zip ties to hold the cable down below where the VP-X will mount. The bends are gentle and the cable knob moves freely. This routing is good with the stock 6 foot long cable.

Molded FAB Intake – 6 hrs

Sunday May 5, 2013

The filtered air box connects to the air intake scoop with a fiberglass tunnel that is custom molded. I started by installing the FAB to the fuel servo and making sure that the front opening was pointed directly at the air scoop by looking in from the front. Then I removed the lower cowling and filed a slight taper to the scoop opening where the fiberglass will overlap. This is to give the fiberglass a surface to bond to without reducing the inside diameter of the scoop.

Then I fit the foam block into and against the opening from the inside of the cowl. This required me to carve away the corners of the block and taper the front edges a bit to get it flush with the inside surface of the cowl. After confirming it was flush I bonded it in with four big globs of bondo which cures up in only 30 minutes.

Then I put the lower cowl back onto the fuselage and began cutting out the tunnel. I started by drilling a 1-inch hole with a hole saw. Then I used a hack saw blade and a file with a curved face to carve out the foam back to the inlet of the air box.

It was pretty easy to carve the foam and get the shape to blend from the oval opening at the front to the more rectangular shape at the rear. The file was better for the finish work.

This is how the carved out tunnel looks from the inside. There is a slight taper as the opening gets larger as it goes aft.

I mixed up some epoxy and laid three layers of 8 oz glass around the inside of the tunnel. I wet the fiberglass between two sheets of plastic drop-cloth film and rolled it out to remove excess epoxy and that allowed me to put the layers down smoothly on the foam which was first wet with a thin layer of epoxy to help the glass stick. Then I put down peel ply to smooth it out and help minimize sanding later. I did not use a balloon as described in the plans.

Late in the day I pulled off the peel ply and sanded the inlet area a little. It looks pretty good. I still need to paint on a layer of epoxy to fill the weave but it looks very promising so far.

I chipped away the foam block and the bondo globs and sanded the outside of the tunnel to get the last of the foam off. This looks like some kind of weird fish orifice. Its not shown here but I also applied two more layers of fiberglass around the outside of the tunnel at the fillet with the cowl as recommended in the instructions to strengthen that joint.

I also worked on  installing the alternate air door on the bottom of the FAB. First I sanded the fiberglass shell because I found lots of cracks in the surface of the primer. I don’t know why that happened but I sure didn’t want to paint over that so now the box looks kind of ugly. Regardless, I drilled a 2-11/16 hole in the bottom of the box for the alternate air door bezel. The blue tape is the direction I plan to run the cable which is what I used to orient the bezel. You can also see the two 1/8 inch holes I drilled for drainage; one inside the filter and one outside the filter.

After match drilling the holes I put in machine countersinks for the rivets. I bent the little tab on the bezel which acts as a catch and a stop for the door. I mixed up some ProSeal and riveted the bezel to the box with ProSeal in the joint. THe I temporarily installed the door with the supplied hardware. Now the ProSeal needs 3-5 days to cure before I paint this thing.

Installed Nutplates for Access Covers – 1.5 hrs

Wednesday May 1, 2013

I am still waiting for the ProSeal to set up in the filtered Air Box top mount so I worked on installing nutplates for the aft fuselage access plates where the elevator linkage is located. Here is a tip: Install the nutplates before you rivet the skins onto the fuselage bulkheads. I cannot get my squeezer yoke into the opening to dimple or set the rivets. If I had a small yoke it might work but mine is 3 inches and it is too large. I needed to dimple for #6 screws so I rigged up a dimpler from a small C-clamp in a pinch. I drilled #12 holes in two small aluminum blocks and glued them to the jaws of a C-clamp. The blocks hold the dimple dies.

I used that tool to dimple the #6 screw holes and the #30 rivet holes as well (with the #30 dimple dies of course). It worked like a charm and is much easier on the hand than the pop rivet dimple die method.

Here is a closeup showing the dimples. Looks good. After that I riveted in the nutplates using my rivet gun with a flush set and bucking bar. Covers are now installed.