Upper Engine Cowling, Part 3

The next step in the oil cooler duct installation was to install it into the cowl.  Before attaching the duct to the cowl, its precise orientation with the oil cooler had to be insured.  As shown below, the oil cooler duct was temporarily glassed onto the exterior of the cowl, with its terminus mated to the oil cooler inlet.

Once the duct was fixed at the cowl exit, the cowl could be removed for the permanent installation with resin, flox and glass.  The picture below shows the flox fillet around the base of the cowl/duct intersection.

Next, a couple layers of glass with resin were smoothly applied over the wet flox mixture and allowed to cure overnight.

The results were impressive.  Hard as a rock, yet pretty light.

The next upper cowl task was to create a small fiberglass "hood" or optimizer for the NACA inlet ramp, used to increase its effectiveness.  A small quantity of soft, children's modeling clay was hand formed into the aft end of the inlet ramp into a shape that resembled what I was after.

 

Next, a couple layers of glass were carefully laid up on the waxed clay shape.  This process was concluded with a layer of peel-ply, that was wetted out and squeeged away leaving a smooth surface.

Later, the peel ply comes off, leaving a fairly smooth finish, requiring a minimum of filling and sanding.

 The next photo shows the raw and unfinished product, complete with excess, unused cloth.

Views of the profile of the hood or inlet optimizer.

A few shots of the trimmed and cleaned up inlet optimizer.

After the oil cooler duct was dried, the exterior was cleaned up with some vigorous sanding followed up with some epoxy resin and micro balloons to fill in the blemishes.

It was now time to mount the optimizer onto the upper cowl's inlet ramp.  Cleco into place and then enlarge and countersink for riveted attachment in addition to an epoxy/micro mixture.

Finally, it was time for an overall check of cowl fitment and clearance with the oil cooler duct permanently in place.  This check was to be made with the prop hub, spinner back plate and spinner cone installed.  I was pretty nervous, as I was unsure that I had clearance for everything to fit.

The Warp Drive prop hub is bolted (2 of 6 bolts) to the 2 inch Viking prop extension, followed by the UHS fiberglass spinner's backplate...and finally the spinner cone as shown in the photos below.

I breathed a sigh of relief after the spinner cone was in place and revealed adequate (almost too much) clearance between the cowl and the trailing edge of the spinner cone.