Sunday, February 5, 2017

Ch 9.5: MLG / Fuselage Intersection Fairing

Now that the MLG fairing is done, there needs to be an intersection fairing that makes a smooth transition between the fuselage and the MLG.  The key here is that it has to allow for movement between the two.  With weight on the gear and on landings, the gear strut will flex up so the fairing has to allow that without breaking anything.

I really liked Wayne Hick's solution.  See his instructions here for details.  I will only summarize my attempt at it below.

 For starters, I crafted the fuselage side of the fairing out of left over 3/8" PVC foam.  This will form the curvature to the fuselage.  I used the large end of the Eureka CNC MLG fairing I had trimmed off as the template for the airfoil shape.  In the pic, you can see the before and after shaping the contour.

I glued the top side of the fuselage faring to the fuselage using scrap pieces of 3/8" foam to ensure the necessary clearance between the fairing and the MLG.  Afterward, glue the bottom portion to the underside including the MLG cover.  Don't worry, this will become a permanent part of the cover but it will stoll be removable when done.

Now I used other scrap Last-A-Foam approximately 2" wide to serve as the transition from the fuselage-side fairing to the MLG fairing.

I glued it to the MLG fairing butted up against the fuselage-side fairing.  I used expansion foam to fill in the gaps and began sanding to match the fuselage fairing and gently fair it into the MLG fairing.

Here you can see the both starboard (left pic) and port (right pic) from the nose looking back after being sanded to shape.  I'm not sure how I did it but I seemed to be able to shape them almost identical without the use of any templates.

Not shown (sorry) is the shaping of the back edges curving into the fuselage.  See pics below after glassing.

Once I was happy with the shape, I glassed the bottom of each fairing with 2xBID.  I wrapped the leading edge up past the center point and left an overhang at the back supported with card stock.

Here you can see the back edge after glassing the bottom and some trimming and sanding to blend into the existing MLG fairing.  Once I had it the way I liked it, I used a piece of card stock to form a template so I could get the other side to match.

I removed foam from the aft edge and used micro to fill the wedge where the top glass would meet the back edge.  It worked pretty well.

After all the glassing was done, I used an xacto saw and a Dremel with a small saw to carefully cut along line separating the PVC foam from the white Last-A-Foam.  I used a sharpie to help mark it.

After cutting the fairing loose from the fuselage, I used folded over sand paper to clean up the cut line for a nice look.  I also removed the gear and painted the exposed foam inside the fairing with micro to protect against water intrusion.  I also wanted to ensure water could not get trapped anywhere in the gap so the smooth micro finish helps ensure the water drains out the bottom cut line.

MLG Cover on the bottom with
Intersection Fairing mods
I uncovered a problem after separating the MLG cover on the bottom.  I found that I would need to make a few adjustments to accommodate where the corner screws landed for my cover.  I didn't see that coming.  I couldn't move the fasteners without causing a conflict with getting the gear in and out when needed.  So I made adjustments to the intersection fairing on the bottom.  I think it turned out fine.

Main Gear Fairings & MLG Cover Complete!