Cowling Finishing and Battery Cables – 5 hrs

Sunday June 30, 2013

Finishing the cowling is a big job. I need to get the interior of the lower cowling sealed and install heat shielding material so I finished the initial interior sanding this weekend and applied a coat of epoxy mixed with a little acetone to thin it. Then I set that aside to set up.

I received a set of battery cables that I ordered from B&C Specialty last week. These are 4 AWG cables made from welding cable so they are relatively flexible. The first one goes from the battery positive terminal to the main contactor.

The second goes from the battery negative terminal to the firewall ground tab bolt. It is black so it is a little hard to see in this photo. I also installed a 2 AWG braided cable for the ground tab to the engine crankcase. There is also a longer 4 AWG cable that goes from the starter contactor to the starter but I forgot to take a picture of it.

A lot more time was spent repairing a water leak in front of my house. I finally dug down through the roots to the main water line and replaced one joint that was leaking and one valve. I think this is finally done. Hallelujah!

On Sunday the epoxy inside the lower cowling was cured so I sanded the surface lightly and sprayed on a light coat of Ekopoxy. This is a base coat for a coat of gloss white paint that I plan to apply before installing the heat shield material.

I also sanded and applied a fill coat of epoxy to the central region of the outside of the top cowling. This is to fill in the visible pits and cavities present in the fiberglass surface. It looks like more than one coat will be required.

Finished Canopy Fairing – 9 hrs

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.

Continued to Fill and Sand the Canopy Fairing – 4 hrs

Wednesday June 19, 2013

After the epoxy on the canopy fairing had cured for a day I block sanded what I could and sanded the rest with paper wrapped around a piece of pipe insulating foam which is about 2-1/2 inches diameter. If you click the picture below you can see a few low spots but overall it is getting there.

That was followed by two more applications of epoxy with Microlight filler locally in the low spots. The second application was without black pigment since none of it was in the area where it could show through from the inside of the canopy. After this is sanded out I will probably put the forward skin on and check the lay of the two surfaces against each other to see if any additional fill is needed in that area. If it looks and feels smooth to the touch I will spray on some gray primer to get a better look at the surface because it is hard to judge in black with all the blotchiness.

Started Laying Up Canopy Fairing – 8 hrs

Sunday June 16, 2013

This is the first of a series of posts on the layup of the fiberglass fairing on the front of the canopy. I have put this job off for too long because fiberglass work is messy and tedious. I really need to get it done however so I decided to make a go of it starting this weekend. I picked up tips on Bruce Swayze’s web site. Bruce did a nice job of documenting the process step by step. I started by preping the surface of the canopy and frame. I used 70 grit sand paper to rough up the surfaces and I cleaned the aluminum with acetone. I am using 7781 glass cloth from ACS for this job. I need long strips so I laid out a couple of strips of plastic sheet about 3 feet long and marked 0.5 and 0.75 inch wide strips.

I mixed up some epoxy with black pigment from ACS, poured it on the cloth between the sheets and rolled it out to impregnate the cloth. I used a rotary fabric cutter to cut the cloth and plastic sheets into the aforementioned strips.

I used .020 pipe tape to mask off the upper edge of of the fairing line on the canopy. Because the pipe tape is black I also put down a layer of blue masking tape on top so I would be able to see the edge better when laying down the cloth since the epoxy is also black.

I peeled the plastic off and laid the strips down on the canopy/frame joint starting with the 0.5 inch strips first. It took two 30 inch long strips to cover the seam from end to end with a slight overlap. I used a craft brush to stipple the glass cloth down on the surface and get it aligned where I wanted it. This view shows the layup after two layers. I’m glad I only mixed up epoxy for two layers at first because the epoxy was starting to get stiff by the time I got two layers down.

Several hours later I had eight layers down made of progressively wider cloth up to 2 inches. For the top layer I laid up the edge of the cloth flush to the edge of the blue masking tape line. Then I put down strips of peel ply to minimize sanding later. That also allowed me to roll out the layup with my rolling wheel to help push out bubbles. Getting to this point took about four hours. I spent the rest of the day working on a leaking water pipe in the front yard.

By Sunday morning the epoxy was well set and pretty hard so I took off the peel ply. I was happy to see that the layup looks pretty good for a first step. At least to my eye it does. But a lot of sanding is still required.

It took about 2 hours to sand it out and it revealed some high a low spots but nothing excessive for the initial layup. It makes a lot of dust fast so I ran my vaccuum with a HEPA filter a lot.

Here is a closeup view of the fairing blend from the canopy to the forward skin after I removed the blue tape. I did that because I need to get this sanded down to no more than the thickness of the pipe tape because I don’t want the fiberglass edge to be too thick. There are some voids along the seam but that is unavoidable. The best you can do is minimize it. I will fill these voids with another mix of blackened epoxy.

So I mixed up a squirt of epoxy with black pigment and applied some along the seam with a squeegee to fill those voids. Then I took the remaining black epoxy and added some micro to thicken it up and applied it in the low spots of the layup and along the surface of the aluminum. This will fill all rivet heads and let me sand the entire forward frame to a smooth contour (I hope). I now will let this set and begin sanding again tomorrow.

I also received my PC680 battery from Battery Mart this week so I installed that in the battery box on the firewall.

Finished Hinge Pin Covers – 4 hrs

Sunday June 9, 2013

I have been using the brass pins that came with the horizontal hinges in the cowl since I installed the hinges months ago. The plans say to replace them with stainless steel pin wire included in the finishing kit so I worked on that Saturday. Bending this wire such that it looks good is not that easy so I have been putting it off. I started by forming a 180 degree bend at the end of the wire. The radius is just large enough for my finger to fit into the loop. I used the shank of a 3/8 inch socket wrench handle to bend the curve. Then I bent it slightly further to maybe 220 degrees . I laid the loop against the side of the cowl to make sure it fit within the tear drop opening and I marked it for another tight bend right where it enters the first hinge eyelet. That was about a half inch from the start of the loop. I put the wire in a vise and bent it there to make a shape like a question mark. Finally I bent it slightly out of the plane of the question mark so it leans out of the opening as you see below (click it for a bigger image). This makes it easier to insert and remove.

Then the trick is to rotate it 180 degrees in the hinge so the loop leans into the opening and is just flush with the cover. It tuns easily so installation and removal is a cinch. The stainless steel pin seems to go into the hinges a little easier than the brass did so that is nice also. I trimmed the other end of the pin wire to be just flush with the last hing eyelet.

I shaped the other hinge pin the same way and I put both covers on and used a little epoxy/micro filler to smooth out the surfaces on and around the covers and fill flaws. After sand this looks pretty good and I can declare this mini-project done.

This morning early I installed a couple of nut plates on the right subpanel rib of the forward fuselage for the manifold pressure sensor. With the nut plates installed I mounted the manifold pressure sensor for good and put a piece of safety wire on the plastic tube fitting.

Progress on Cowl Hinge Pin Covers – 2 hrs

Thursday June 6, 2012

The cowl need a couple of nut plates for each of the hinge pin covers and the fiberglass needs to be cut away enough for the hing pins to tuck inside. I want a small loop on the end of the pin so there is something to grab to make removal easy without pliers so I cut this tear drop opening on the right side. Then I drilled holes for two #6 nut plates and installed those.

I match drilled the cover and countersank the holes for flat head screws. I put the cover back on to check the fit with 6-lobe torque screws. I also sanded the cover to make sure the surface was flush with the cowl all the way around. I am liking this well enough that I will do the other side the same way.

Cutting Hole for Cowl Hinge Pin Cover – 3 hrs

Sunday June 2, 2013

I am finally getting around to making some custom hinge pin covers for the horizontal cowling hinges. I’ve seen these done in many designs, some very fancy, but I decided to keep them simple. A while back I laid up some fiberglass patches over the area of the cowling where the covers will be installed. They were laid up over packing tape so they popped right off and gave me a thin patch of fiberglass with the same contour as the cowling in that area. Today I cut those patches into 2 inch diameter circles which will become the pin covers. I also cut 2 inch diameter holes in the cowling directly adjacent to ends on the hinges for the cover plates.

Here is one of the cover plate plugs placed into the hole in the cowling. I put packing tape on the back side and waxed the edges before putting it in and then taped over it. The cover is brown because my Stewart Systems epoxy was getting old and has a tendency to turn brown over time. It does not affect the strength.

Here is how the cover looks from the inside. This is now the mold for an internal fiberglass lay up which will hold the nut plates for the cover.

I mixed up a thick batch of epoxy with flocked cotton and applied it over the covers as shown below. This will cure overnight then I will remove the covers and cut the new fiberglass layup along the hinge line to release the upper cowling from the lower cowling. Then I will put a couple of layers of fiberglass cloth over the area to add strength. More to come.

 

Update: After the epoxy cured I cut a line along the hinge axis to separate the top and bottom cowling sections. I sanded the interior surface to get it mostly flat and then laid up a couple of layers of glass cloth on the inside to add strength to the flox. When that cured I enlarged the notch for the hinge pin to exit and then put it back together for a check of the fit.

I also modified the air intake seal this weekend. I did not want to use rivets to hold the rubber seal on so I made five U-shaped aluminum channels from .032 stock and bonded them to the surface of the air intake. Then I cut rectangular holes in the seal material coinciding with the channels. When I installed the rubber seal the channels lock the seal in place so it can’t slide around on the air intake flange. Then I secured it with a zip tie that lays in the channels so it is locked in position also. Now the air intake inside surface is perfectly clean for smooth airflow, and the seal is easily replaced for maintenance.