Archive for the ‘Engine Baffles’ Category

Finished Canopy Fairing – 9 hrs

June 23, 2013 Leave a comment

Sunday June 23, 2013

Continuing work on the canopy windscreen fairing I masked off the entire area and sprayed a light coat of gray primer on the surface to get a better look at the smoothness and overall shape. The blotchiness of the raw surface is just too hard to judge so I have been going by the feel of  my hands more than by sight. The primer showed a few minor defects including scratches, pin holes where the fiberglass fabric was exposed, and a few small divots – but not bad for this stage. However, the pipe tape is still in place and it is thicker than I want the final windscreen edge to be.


So I sanded the primer off completely and removed the pipe tape masking the windscreen. This gives a preview of the final edge although it is thicker than the final edge.


I put down a single layer of 3M electrical tape as a new mask line for the final edge thickness. I filled the defects I found with the primer and smoothed it out with another round of sanding. I carefully sanded the windscreen edge until it was just about flush with the new tape surface. It seems thin but that is the recommended final edge thickness, blending almost to nothing. Now here is my biggest mistake on this fiberglass work. At this stage the instructions said to brush on a heavy coat of epoxy so I did. That turned out to be a bad idea because it just does not go on uniformly at all. The surface was very irregular when it cured and I had to sand virtually all of it off to get back to a smooth surface. What a waste if time and effort. To make things worse, a bit of the epoxy got under the front lip and stuck it to the fuselage frame so when I raised the canopy it bent the lip, ruining my nice finished surface. So I had to straighten it and apply another layer of epoxy and filler to fix it. Not a disaster but I big pain to be sure. In this photo you can see the new filler along the front edge.


So after final sanding with 220 grit I decided I would try the primer again. If there are new defects this will expose them. I used a high build primer I picked up at Aircraft Spruce in a rattle can. Here is how it looked after spraying. To my relief there were no new defects other than a few tiny pin holes which the primer mostly filled.


After a few hours of drying time I sanded the surface lightly with 400 grit paper to remove the roughness and pulled off the masking for the final time. I am not great with fiberglass work but I am definitely happy with this result. It looks very nice. Even my wife, the unofficial quality inspector, said it looks good.


Here is an attempt at a close up that shows the final edge.


I was lucky to get this done this weekend because I continued to spend hours digging for a water leak in the front yard. I found one and fixed it, but there is apparently another because the hole is not drying up. What a pain. More digging to follow.


But I also succeeded in putting a coat of primer on the inside of the upper cowl.


And I tied off two of the four lower baffle flaps on the engine with the little wire retainers I copied from VAF. I tried three time to thread the rods provided in the kit for this but finally gave up and went with the safety wire method. Two more to go.


Various Tasks – 5 hrs

May 11, 2013 Leave a comment

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.


Finished Riveting Engine Baffles – 6 hrs

April 21, 2013 Leave a comment

Sunday April 21, 2013

There were lots of chores needing attention around the house this weekend so I only had time to do a few things on the airplane. At least I finished riveting all the rubber seal strips to the engine baffles with a little RTV on the surfaces to seal up air leaks. I’m glad to have this done. My hands are sore from squeezing all the pop rivets.


This view shows the aft side of the spinner area.


I also did some more trimming of the filtered air box top. It is now a little over 2 inches from the front edge to the inside edge of the inlet. That should be enough that the cowl can drop straight down without hitting the top cover. I am mentally struggling with how much gap to put between the air box and the inlet scoop. I am concerned about making the gap too small because of the threads I have read about FAB top plate cracking, perhaps caused by forces put on the FAB at engine startup due to relative motion between the FAB and the cowl. But a large gap may be harder to seal effectively. I also want to make the cowl as easy to install as possible and the FAB seal can be a major factor in that. I had a few questions I posted on the VAF forums so I am waiting to see what responses I get before proceeding.


I also sanded the exterior of the top cowl this weekend in preparation for applying a seal coat of thinned epoxy. No pictures of that.

Installed Alternator Blast Tube – 1.5 hrs

April 17, 2013 Leave a comment

Wednesday April 17, 2013

Monday night I painted the blast tube duct for the alternator with some glossy high temperature rattle can paint. That was dry tonight so I riveted it to the alternator aft cover and installed the corrugated blast tube.


I re-installed the cover onto the alternator and routed the other end of the blast tube to the hole in the inlet ramp. Notice that the tube routes downward through a 180 degree bend and back up to the duct that directs the air into the cover and directly onto the cooling fins of the voltage regulator. This 180 bend is my trick to keep rain water out of the alternator. I drilled a small #40 hole at the low point of the bend in the corrugated tube. It will leak a little bit of air there but any rain water that gets into the blast tube from prop wash will collect at the low point and be ejected by this drain hole. It won’t prevent moist saturated air from entering the alternator but I have not heard of that being a problem.


Now I have two more blast tubes to figure out how to route; one for each P-Mag.

Cowling and Alternator Blast Tube – 5 hrs

April 13, 2013 Leave a comment

Saturday April 13, 2013

The cowl surfaces are rather porous in the stock condition so the plans recommend that the surfaces be sealed with a thin layer of epoxy. But because the surface has tiny holes that the epoxy will not flow into naturally the epoxy should be thinned with acetone at about a 1 to 1 ratio. This morning I sanded the interior surface of the upper cowl and brushed on a thin layer as prescribed. The acetone slows down the curing process so it will sit a few days before I sand off the gloss in preparation for a coat of primer.


The instructions for the Plane Power alternator call for a blast tube to direct cooling air into the back opening of the alternator case. I did some research on this in the forums to determine how to mount the blast tube. The alternator is near the front of the engine so the standard place for the tube is in the right inlet ramp just behind the cowl nostril. I saw various ways of attaching the blast tube to the alternator, none of which I really liked. I also read of cases of alternator failure in rain conditions which is more likely to occur with the blast tube so near the air inlet of the cowl. So I decided to try to come up with a better way of mounting the blast tube to the alternator and reduce the risk of water blowing into the alternator case. I don’t know for sure that the water is a problem for the alternator but it seems like it can’t be a good thing.

To attach the blast tube to the alternator I designed a duct that I will rivet directly alternator rear cover. I removed the cover and built a mockup using  file folder paper. Then I made it from two pieces of .025 aluminum sheet epoxied and riveted together, mounting directly over the air inlets of the alternator. Here it is clecoed to the alternator rear cover with a blast tube installed.


Here is a side view showing how it is mounted to the cover. Air comes through the blast tube, turns 90 degrees and enters the alternator cover, exhausting out through the vents further forward on the alternator.


From the inside of the cover you can see the two square holes where the air will enter. I will give the epoxy a couple of days to fully cure then I will prime the duct and rivet it to the cover.


I will show you how I plan to address the water problem when I install this to the alternator.

Painted Engine Baffles – 6 hrs

April 11, 2013 Leave a comment

Thursday April 11, 2013

I decided to paint my engine baffles this week. The alodine finish was OK but the parts lacked the finishing touch I was hoping for so I picked up several cans of  Ford red high-temp engine paint at the auto parts store. Now the baffles have a definite visual punch. I tried to find a gold color that would match the engine crankcase but had no luck. So I went with the strong statement of contrasting red. The color matches the ignition wires nicely. Compare this photo to the pre-painted photo on April 6th.


This view is from the oil cooler side. It looks kinda stunning.


And for good measure here is another shot from the right rear quarter.


Finished Fitting Seals – 4 hrs

April 7, 2013 Leave a comment

Sunday April 7, 2013

I continued working on the baffle seals today finally getting to the cowl-mounted seal strips that seal up the gaps between the cowl and the inlet ramps. You start by sanding the inside surface of the cowl to get a smooth surface for the seal. Then I bent a 1/2 wide aluminum strip to match the inside profile of the inlets. Here is a view of the right inlet. The strips have to be fairly thick because they are only attached along the flat portion of the cowl. The stiffness of the aluminum strip provides pressure to hold the seal in place as it wraps around the curved portion of the cowl. I trimmed the left end of the strip after I took this picture.


As before I made a paper mockup of the seal to get a close approximation of the final shape for the rubber material. Here is the left seal after cutting the material, match drilling the aluminum strip to the cowl and the rubber seal and putting it back on the airplane for inspection. It seems to seal fit pretty well and I expect it to seat even better after a few hours of flight time.


Here is a view of the interface with the baffle seals on the inboard side around the ring gear.


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.


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


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.


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.


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


And this is the right side…


And the right inlet duct near the ring gear…


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.


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.


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


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.


Making Baffle Seals – 5 hrs

April 4, 2013 Leave a comment

Thursday Apr 4, 2013

Tonight I finished cutting and fitting the rubber seal strips along the side baffles for the engine. The brown paper templates are gradually going away.


Inlet Ducts and Baffle Seals – 9 hrs

March 31, 2013 Leave a comment

Sunday Mar 31, 2013

The post covers work done the week of March 25th through March 31.

I mixed a batch of epoxy and microlight and applied a layer to the inlet ducts to smooth out the surfaces of the layups provide a smooth transition for the engine baffles. After sanding the microlight the surface is looking pretty good.


While the cowling was off I took the opportunity to safety wire the upper alternator bracket bolts.


With the inlet ducts in shape I could now finish trimming the forward engine baffles on the sides and adjacent to the ring gear. I was surprised how much I had to trim off and it took quite a few iterations to get it done because the visibility to the baffles is so poor in these areas. But after several hours of work on Friday and Saturday I got the baffles trimmed to a gap of 0.5 inch as best I could tell and then started on making templates for the rubber seal material. There is virtually no guidance for how to do this in the plans so I browsed the forums and other web sites to get some ideas. Here is my first attempt using brown wrapping paper for the templates.


This side view of the forward baffle shows the swooping line I trimmed to match the inlet duct.


The rear rubber seals seem pretty straightforward so I cut the first piece and attached it with clamps to check the fit.


Since that looked good I cut the other rear rubber strip and then laid out rivet holes and drilled #40 using clecos for now. Two pieces done and many to more to go.


Categories: Cowling, Engine Baffles