More Cowl Shaping

I didn’t end up with a lot of time yesterday to work on the airplane, but I did want to try to pursue some of the suggestions that I got from James on how to make the cylinder bumps more aerodynamic and smaller.

I got the dremmel out and removed parts of the wood splines that I had installed. The splines turned out to be defining the cylinder bumps much larger than they needed to be. I didn’t consider that the Berkut cowl that I was attempting to replicate wasn’t a singular spline from front of the cylinder bump to the aft end. There are actually “three curves” that are blended together, allowing the vertical profile to be much lower and sleeker. The splines really weren’t doing me any good anyways. Once the splines were removed, I was able to take about an inch or more off the top of the cylinder bump. The difference, when viewed from the front is pretty dramatic.

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Then, with the realization that I had to make “three curves” and blend them together, I started by making three flats. I made a horizontal flat over top of the cylinders, and sloped flats from the forward cylinder forward to the top of the strake and the aft cylinder to the air exit template. Then blended them together. In addition to making a much lower, sleeker top surface, this allowed me to have a much more gentle curve around the outboard side of the cylinders.

I broke through the foam in a few places, but those will be easily repaired. I have to optimize the cylinder clearances, and to do that I plan on making a few holes in to foam to check clearances. Once I am convinced I am at or as close to minimum clearance as I can be, I will fix the holes and proceed.

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Also note that the engine mount is sticking through the foam at this point. I decided to add a small blister to take care of the clearance there. Properly faired, I think I can make it look purposefull and not detract from aesthetics.

With the little time I had to work, I only got to rough out one side, but I am feeling better about this track, and think it is looking much nicer, and will be considerably less drag. Once I get home from this trip, hopefully I can get the other side roughed out and start working on the clearance checking.

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