Sunday, January 22, 2017

Ch 9.5: Gear Strut Fairings

Pick'in up Some Knots

Top View of Eureka CNC Fairings
Side View of
Eureka CNC Fairings
Although the MLG strut has an airfoil shape to it, it's formed in way that puts it out of alignment with the air stream when it's in cruise.  That creates unnecessary drag which reduces speed and fuel efficiency.  Several builders (Wayne Hicks, Kevin Walsh, and others) have formed fairings over the strut to realign the aerodynamic shape which reduces drag and increases speed. Kevin and Wayne did it slightly different but the result is very similar.  Kevin worked to have his made available through Eureka CNC.  These are what I used.

The fairings come in two long straight pieces that won't bend around the curvature of the strut so you have to cut it into pieces.  I cut it into 8 pieces, larger widths toward the top and thinner widths where the strut curves sharper.  I positioned the top piece about 3/8" gap from the fuselage side and went down to about the top of the brake heat shield.  I'm assuming that some of this will end up being trimmed off when the wheel pants are built and installed.

Test Fitting
Then I tested the fit by taping the pieces on each leg.  I numbered each one to ensure I put them on in the proper order.  Note that the closer to the bottom you get, the foam get's very thin and hard to keep from breaking.

Vacuum Bagging
To the left is my poor man's vacuum bagging technique with a small shop vac.  It worked well enough to keep the pieces all together and aligned while they cured.

To the right...taken after the foam has been micro'd and glassed with 2xBID. Notice the white trailing edge.  I glassed the bottom side first and then removed foam from about a 1/4" or so on the top at the trailing edge, filled the gap with micro, and glassed 2xBID on top.  This gave it a nice solid sharp edge that should be able to survive a minor hit without permanent damage.

The bottom was trimmed off to be level while sitting on the ground.  Next there needs to be a fairing built for the intersection of the MLG fairing and the fuselage side.

Onward, cab

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