Baffles #6

Time: 10 Hours

Now that I have all the fitting done with the forward ramps I could rivet most of the parts except the areas that tie the ramps to the side baffles. I was able to get most of the rivets with the pneumatic squeezer but had to get the rivet gun and bucking bar out to finish the rest.

The next task was to create the tie rods that close up the bottom of the cylinder baffles. These rods are made out of a stainless steel rod and have to be bent/threaded. The plans give you an initial bend angle to start. I measured and cut the length to start for the inboard ones. I made the bends and tweeted them to get spacing I needed. The idea is the bends will give the rod clearance over the other parts that lie at the bottom of the cylinders.

Once I was happy with the bends I grabbed my tap set and threaded the ends for a nut and washer.

I moved on to the outboard rods which are a little longer and need a second bend as these need to clear one of the oil return lines.

This what they look like installed. You can see that the rods pull the curved sections together and making a seal around the cylinder fins.

Before moving on to more baffle work I wanted to put on a layer of epoxy/filler on the snorkel so I can start the work of smoothing the surface. I also set a mixture of epoxy/filler/flox under the alternate air door so it sits flush.

Now back to the baffles and the start of the big top cuts. The idea is that you need to cut the tops of the baffles al the way around so that there is a gap between 3/8″ and 1/2″. This is easier said than done but just takes time. I realized that the support bracket in the left aft baffle was way to high based on how I installed it. So I removed the rivets and will make a new one later once I get the tops cut. With that part removed I put the top cowl on to see the areas that were touching on the aft and aft side baffles. I started with making small 1/4″ cuts off the top until I could get the cowl on with around an inch gap in the back.

Looking in through the gap on the aft edge looking forward you can see how the baffles look as they touch the inside of the cowl.

Now I had a manageable shape and had some areas touching and others not. To get an accurate scribe of the inside surface of the cowl you can use the “paper clip” method. The idea is that you install the clips along the edge of the baffle. Then install the upper cowl and as you press down on the cowl it pushes the clips down. Then you can measure down from the top of the clips, in my case I started with a 1/4″ measurement, and make a mark. You then connect all the marks to give you a line that matches the underside of the cowl.

I did this around five times slowly removing material. The hard part is after I measure I have to remove each of the baffles so that I can remove the material then put them back in place which takes a lot of time and effort. As the cowl “drops” on the aft end the shape changes slightly so I made smaller cuts to account for this. Here is a line of clips from left to right and how they ended after the cowl was put on. You can see a lot of them are pushed flush and a few have a little space left on them.

With the last cut I have a pretty even gap around 1/8″ all the way around the aft and aft side baffles with the upper cowl in its final place and the SkyBolts secured. So I will do the paper clips one more time and measure down 3/8″ to get the final gap. Before I could do the last cut I needed to figure out what I was going to do for the left side bracing. This creates a straight line across for the baffle seal fabric where the oil cooler bumps out. I had revealed that I riveted it on way too early and it was positioned too high. I decided to fabricate my own and make it fit as I needed it. I wanted to make sure I planned for the heater scat tube as this was the area I would install it since my oil cooler is now on the right side. So I started off with some card stock paper and made a template. After a couple of tweaks and measurements I transferred it to some sheet stock to start the fabrication process. I needed to have several bends as this area needs to be sealed up to keep the positive pressure in the engine area. Once I had the shape built I laid out rivet holes and match drilled it to the baffles. The lower flange was laid out with the scat tube pick up as a drill guide.

I was very happy with how it turned out and it should serve its purpose. With that part made I could use the paper clips across the entire aft baffle to make the final cut. I marked the outline of the scat tube pickup and drilled to make the opening.

In the last photo you can see the upper left corner of the brace I fabricated I now have a notch. That’s because I really carefully laid out the five rivet holes in it prior to getting the final cut done on the top of all the aft baffles. That ended up putting the upper most rivet hole way to close to the edge…dummy! So I just clipped it out and that’s that! It will be covered up by the fabric seal anyways but it’s that kinda of thing that is tough when fabricating parts is the forward thinking and the way forward thinking. From here I moved onto to forward side baffles. The process is the same, measure, mark, trim and repeat. I ended up with a nice 3/8″ gap all the way around.

Next up will be the forward baffles and there complex cuts.

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