Happy Labor Day!! The weather has finally broken in Texas, Today is a beautiful day and the first time in 2 months that I can work in the shop with my shirt on!! You guys have no idea how uncomfortable you can get after sanding fiberglass or welding all day with no t shirt on!!! I have been using this 3 day week end to good advantage. I started on the cowl cooling baffles. This is an extremely critical portion of this design. I have learned the hard way about the importance of engine cooling. In an effort to save as much weight as possible I removed all of the engine driven fan blower and shrouding on my old Kawasaki 440 engine I was using on My Wren. I knew I needed to correctly duct the inlet air across the cylinder, but I completely neglected controlling the total air flow. Air is lazy, it seeks the path of least resistance, and usually that is anywhere but the air passage between the cooling fins, I initially thought I could fabricate a Styrofoam mock up of a duct and then cover it with one layer of graphite cloth. MEK would make short work of the core after the Graphite cured, but I found that in building the duct, the volume had to first decrease then increase to the final volume. This would choke the flow. The idea is to slow the flow before it passes thru the cooling fins, but not restrict it. i tried a few different ideas but finally settled on a scheme where the cowl was divided in half before the engine. The only path for the inlet air will then be the passages around the Cooling fins.
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Baffle Supports |
I started the construction by removing the carburetor. I used two aluminum angles and picked p the 4 screws that attach the reed valve body. The next step was to fabricate an aluminum baffle that attached to these angles and spanned from the upper cowl to the lower cowl and from the firewall to the front edge of both cowls. This was a tedious effort. I started by cutting a sheet of .020 aluminum oversize.
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beginning of the Baffle |
I kept trial fitting the lower cowl until I had a 1/2" gap between the baffle and the lower cowl and fire wall. All along the periphery of this baffle an angle will be added to attach a 2" wide silicon Cowl baffle strip.
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Baffle with cut out |
after the divider was built , I fabricated a split aluminum duct that shrouds the cooling fins. Once sealed up the air has no place to go except across the fins. I had to trim back the upper Left corner to clear the upper cowl.
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Trimmed duct |
After the duct was trimmed I fabricated a 1/2" wide curved flange that will attach the Silicon Baffle.
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Baffle flange attached |
I am now waiting for my next order from Aircraft spruce to arrive with the Baffle and a pre-drilled retainer strip.
I believe that i am dealing with the two most efficient companies in the world when I order from Aircraft spruce and its shipped by UPS. They are a very well oils close meshed team. I can order something on a Monday and I will be installing it the following Thursday.
Once I got as far as I could with the baffles I started installing the adjustable rudder Pedals. During the construction I realized that I didn't need to use 3/8 4130 tubing for the cable guides, 1/4" Copper tubing worked fine. i was able to force 3/16 Nylon hydraulic tubing through the center after I bent them. These will act as strain reliefs and cable guides.
Rudder Pedals being trial fitted