Inside Cowl

Time: 4 Hours

I started the process of sealing up the inside of the engine cowl. You do this for a couple reasons. First is to keep oil and other fluids from soaking into the cowl and the honey comb interior. The other is so it can be painted, although this isn’t required, as it will help down the road to identify any leaks. Most paint theirs with a light color like white to make the leaks easier to see. Another reason to smooth the lower cowl inside is so that the adhesive backed aluminum heat shield material will adhere better. So to start this long process I worked on the tube that will direct the hidden oil door retention pin. Ok so that may be confusing. So let me explain, I’m using the hidden hinge from Cleaveland Tool on my oil door. This makes a nice clean look without and visible hinge. To latch the door down you can do many different things but I decided to use hinge and it’s pin to secure the door. When the pin is in place the door is secure and cannot accidentally open if the door flex’s under pressure. So how to pull the pin when the cowl is in place and the door is secured. I decided to make the pin extra long and access it from the inside of the baggage compartment. The idea will be to open the baggage door, pull the pin just enough for the door to open. To close the door I would hold the door flush and push the pin into the hinge. But trying to aim the pin several inches to the first hinge eyelet with seeing it would be very difficult. So I decided to secure a aluminum guide tube to the inside of the cowl. I fluted the opening a little so that the short distance the pin will have to go and the flute helping direct the pin into the opening will make it easy. I used the pin to keep the tube aligned and some washers for the correct height. I then laid up two layers of fiberglass over the top of the tube and let that cure to give it a secure hold. After that I used Super Fill to give it a good shape and sanded it to look nice. I’ll work on the pin later but for this part it looks good and hopefully works ok. I then filled and sanded any big imperfections in the cowl surface before sealing it. The process of sealing for me is just using epoxy without any fillers and thinning it slightly with acetone. Then I brushed it on the entire surface with a cheap brush. Then with a old hotel key, the credit card looking ones, I scraped all the extra epoxy off. This forced the epoxy into all the tiny pin holes and voids. Then after that cured I did a light sanding with my maroon 3M pads to knock down the high spots. I cleaned up the entire surface again and repeated the process. I think I will repeat the process one more time then primer and paint. For now I’m thinking an aluminum color high heat engine paint but not sure yet. While this one cures I started the filling process on the lower cowl. I gave it a good sanding to get rid of a bunch of imperfections from the manufacturing process. I’m going to spend more time on the lower cowl as it will be seen more especially if I have it judged at AirVenture some day. When people are looking at the engine the lower cowl is really visible. I will keep working on it but for now I need to get all this dust off me.

More Baffle Work

Time: 6 Hours

I spent some time in the hangar yesterday and today trying to finish up the baffles. I worked all the airseals around the front baffles and got them to sit almost perfectly. I had to trim the upper air ramps a little to make it happen. I’m pretty happy with they way they seal and fit but I’m hoping they lay down after they are used on the warm engine aa they make it a little difficult to put the top cowl on due to their stiffness. So the next baffle task was to drill for three cooling blast tubes. These tubes will direct air to areas that need cooling. That’s for me are the two P-mags and the alternator. So I laid out where I wanted them and drilled a pilot hole followed a 5/8″ hole using the step bit. I used adel clamps to secure the ends and direct them to the P-mags. I ran out of the tubing and had to order more from Vans. I did drill the hole in the right side forward baffle for the alternator blast tube. I put in a small piece of tube in to check the fit. Two more holes I need to drill for are for the spark plug wires. I’m using a special pass thru clamp from Aircraft Spruce that holds the wires firmly as they pass thru the baffles. The shape looks like a number eight. I was almost sure I was finished with drilling on the baffles when I realized I had forgot the blast tube for the engine driven fuel pump. I had bought and installed the ShowPlanes cooling shroud that uses a 1″ blast tube. So I ordered a 1″ duct flange, some ducting and clamps from Aircraft Spruce and will drill for that when they arrive next week. I had one other task I wanted to get done and that was to plug the two holes on the aft side baffles. These holes are for a socket extension so you can get the spark plug in (I think). Either way they need to be sealed. So I made a cover using some sheet aluminum shaped into a circle and epoxied a spaced onto it to account for the angle that splits the hole. I also cut a couple of sheet for the opposite side. These two pieces will be screwed together and sandwich the baffle sealing the hole. So that’s where I stopped for the day after cleaning up the shop. I’ll get back at it next week after the parts arrive. Now to decide to paint or not paint the baffles!

Baffle Seal Work

Time: 4 Hours

I got to spend a few hours in the hangar today to work on the baffle seals. Before I started on that task I painted the snorkel and the fiberglass oil cooler plenum. I found a spray paint that is very close to the metallic silver on the engine. I really like how this paint turned out and look forward to seeing them on the engine. So now the baffle seals and new silicone material I got form Aircraft Spruce. I made a couple of templates for the aft section and sides to use to cut the silicone. Over a couple of hours I put on/took off the pieces and trimmed them as I went. It took several iterations to get them the way I wanted. I bought a leather hole punch that makes quick work of the attachment holes. I decided that I wanted to use screws vs rivets as the plans called for. I chose to do this so I could easily replace the seals in the future. So I’m happy so far and still have the forward seals to finish. The seals make putting the upper engine cowl on a little difficult as they have now formed to the final shape. I’m holding that will get easier as time goes on.