Cowl Surgery Commences

Today was day one of cowl surgery. I started by making a template for the cowl air outlet. I made it out of 3/4 pressboard. It took a bit to figure out the shape I wanted to end up with and verify it closely matched the pre-fab cowl exit area and width. One thing I did was offset the center circle downward slightly. I did this to compensate for engine sag after the dynafocal bushing set in as well as engine sag during g-loading.

Once it was cut out and sanded to shape, I match drilled the template to fit the SAE 2 prop flange on the end of my Saber prop extension. I modeled the shape and rounded ends after the Berkut cowl as I think it looks nice, and James has his going pretty fast with good cooling.

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This photo makes the template look big, but that is due to optical illusion from where I took the photo. The ends of the template are actually inboard of the cylinder rocker covers slightly.

After getting the template mounted on the prop extension, I aligned the pre-fab cowl to the fuselage centerline and starter ring gear centerline. I added a 1/2 inch spacer to the top of the ring gear to ensure I would have proper clearance.

Once these things were aligned, I took everything off to bag the engine. I simply took garbage bags and plastic grocery bags and wrapped the engine and accessories to protect them from any pour foam, epoxy, and dust that could get into the engine or components. 

Next I took out the plans and used the plans method of temporarily mounting the cowl. Evenly spaced fasteners were placed around the firewall and wood blocks were match drilled to these holes. Then these blocks were bondoed to the firewall creating a rigid way of mounting the cowl. 

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Next was the committal step in the cowl surgery. I marked the areas over the cylinders to be cut away, got out the die grinder with a cut off wheel, and removed that which I didn’t want. Of course I did have to call in a consult to get a concurring opinion. I believe these cowls are kevlar as evidenced by the yellow color. When you are grinding on this stuff, it stinks.

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The cowl looks…. better already…. or I am crazy.

Hopefully tomorrow I can get the flanges temporarily mounted to the spar and wing as well as get a start on adding foam over the cylinder areas to prep for shaping. I haven’t decided just how to do it yet, but that is part of the fun of it, right? I said right? We will see. 

 

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