Lower Engine Cowling, Part 3 - SURGERY!

What happens when you order avionics and you have from 1 to 3 weeks on your hands?  You get creative.  I have been tempted for a while now to rid the lower cowl of the "lower shelf" that was a fairly unflattering attribute of this first generation Viking RV-12 cowl.  Add to that Jan Eggenfellner's assertion that you can increase the speed of your RV if you remove it....so I did.

  And I removed some more!  I am going to get a more traditional look from the lower cowl and completely eliminate the remnant of the lower shelf.

Okay, so now there's a gaping hole in the bottom of the lower cowl - now what?  Install some foam, sand to the desired shape and glass it in.

A nicer, cleaner profile results from the surgery.  What remains to be seen is if my new section of cowling will blend in nicely with the existing configuration.

A better shot of the profile revealing the extent of the section to be replaced and incorporated with the original.

Went to Michaels Aviation Store (hobby and crafts, actually) and purchased some manly "floral foam" and went to work cutting the shape on the bandsaw and then "foaming" it into place as shown below.

Here is the bottom exterior shot where the new glass will be laid up.  I have no real idea what I am up against.  It seems too flat, so I will probably try adding another layer to add some curvature to it...but first, there is a lot of sanding to do.  More later.

After some time sanding the floral foam to the desire shape, I then laid a generous coating of carnuba-based automotive wax to the "mold".   A little time to cure and then the layup of 2 layers of glass cloth, followed by the peel ply and we'll see what happens.

The peel ply does its thing, leaving a pretty nice surface to finish off.

The resulting final shape of the lower cowl is now to my liking.  Flight testing the capability of the engine cooling will be required to know how much of the exit ramp to trim off.  Until then, I am pronouncing the lower cowl done!

Upper Engine Cowling, Part 4

Another upper cowl task was the installation of an oil access door.  The first order of business was to spec the location of the door, which I did with pencil marks and a long, 90 degree square ruler.  Measure 3 times, check twice, cut once.  Also shown in this photo is the original Van's oil access door hinge which I eventually discarded as I could not make it work to my satisfaction.

Below is the picture of the resulting cut in the cowl.  It appears to be a carbon fiber looking door, but you are seeing through to the workbench which is covered with my protective cloth (which is a non-slip rug pad).

Time to prepare the cowl to act as a mold for the access door, so I inserted the fiberglass blank that I cut out from the cowl and duct taped it into place (outside and inside) and then coated with a generous amount of automotive paste wax.

Laid up 5 layers of glass (about 1-2 too many) over the cowl mold.

Applied a final layer of peel ply to kill off as many of the pin holes as possible.

Dry and ready to peel off.

Next was the process of creating a backing plate that would also accommodate the latches for the access door.  Thin sheet 6061-T6 aluminum was used for this.

   Once cleco'd into place the hinge and door were fitted into place.

More cleco's and final fit of the door assembly.

Finally, the latch fittings were sized and riveted into place.

It works nicely and gives sufficient access to the oil tank dipstick and other engine compartment necessities.

Last shot...

Another Brief Return to the Firewall Forward

As with the brief return to the fuselage work (autopilot pitch servo), I also took the opportunity of some slack time, to mock up and finish installing the oil breather assembly.

I ordered a different K&N air filter that would yield more surface area as well as provide a larger entry point for the attachment of the 1 inch oil breather hose that is routed from the oil tank and then to a breather cap.

Shown below are pictures of the modified K&N air filter that was drilled out to accomodate the oil breather line.

I affixed a hose clamp on the inside termination of the hose residing in the filter body.

I used a tight fitting washer bonded to the filter with some Permatex Right Stuff gasket making compound, followed with another hose clamp.

The two shots below show the installation of the breather assembly on the engine.

Another brief task involved the installation of the radiator shroud.  First task was to give adequate clearance between the shroud and the cowling.  After a trial fit, the two areas that were closest to interfering were marked and sanded as shown below.

Next, it was time to bond the shroud in place with the prescribed Permatex product, The Right Stuff.  A healthy bead was laid around four sides and clamped into place.  Done in an hour.

Brief Return to the Fuselage (Autopilot Servo Install)

As I had some down time between engine cowl fiberglass layups, I returned briefly to the fuselage for the purpose of installing the autopilot's pitch trim servo.

The first photo details the initial installation of the pitch servo motor by bolting it down with 4 AN-3 bolts to the seat bottom rib/doubler.

Next, the pushrod was attached at one end to the servo's arm, with the other end being attached to a tab on the joystick's torque tube assembly.

Finally, the wires were connected to the ship's wiring harness and tie wrapped neatly together as detailed in the final two pictures below.

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.