Fiberglass cowl mock up

I just completed the lay up and fitting of the fiberglass mock up cowls, spinner and spinner backing plate. I decided to make some scrap fiberglass parts first so I could set the final trim lines and locate the attach fasteners. I used fiberglass because i could see thru it and measure from the edge of the mating structure underneath the cowl. The final parts will be 2 ply's of 7 oz Graphite cloth. I don't want to scrap those parts!! the material is $32/yd compared to $4.90/yd for glass.

scrap parts

As you can see from this picture.The cowling is translucent and the sub structure was visible. All in all the cowling fit very well. Even so, I will still not drill mating holes in the lower graphite cowl. I will match drill those holes from the upper cowl. The cowl will be fastened with countersunk screws into a nut plate riveted to the lower cowl.

view looking aft

this is a good view of the asymmetrical cowling. i chose to do this because I will flow the air over the single cylinder. The inlet will have some foam blocks added to the inlet lip that will act as a flow diffuser.  The idea is to slow the air down before it turns the corner. Heat added when it flows across the head will recover the pressure loss. its very critical that this cowl be fully sealed. a series of aluminum and silicon baffle plates need to be fabricates. as does an aluminum heat shield for the exhaust. The next step will be to cut out the out let around the tuned pipe.

another view without the spinner

The cowl will be pretty light. The final parts should weigh in at just over a pound.

graphite backing plate

This is the graphite spinner backing plate. although I only used 3 ply's of 7 oz graphite, it is half the weight of the 7 ply fiberglass mock up, yet it is at least 10 times stiffer. I will wet sand the resin line that is visible. this is the joint between the two mold half's. I will chuck this part in my lathe in the 3 jaw chuck to register the center, This will be a check to see if I located the center true enough in the mold.


On another unrelated note, I am now back in Design at my company Triumph/Vought. I am working on a manned/unmanned program based on the Berkut Home built. We are designing a larger version. I had the pleasure last week of meeting Dave Ronnenberg, the designer and builder of the Berkut. I was invited late this week to come out to Santa Monica and fly the Berkut by Dave. I'm sure we will also talk about some structural issues!!!I leave tomorrow morning for Santa Monica via San Diego. My friend Mike and Neal La France are going to pick me up at the Santa Monica airport in a Luscombe Sedan  and fly us back to Gillespie field in San Diego. Neal and Mike are old friends from my early Wichita days. its been years since I have seen them.