Upper Engine Cowling, Part 2

With the top and bottom halves of the cowling mostly completed and the NACA ramp temporarily installed, it was time for additional work on the upper cowl.  First up was the fabrication of the oil cooler inlet duct.  Although I did not take any initial or intermediate pictures of the mold-making process, what is documented is the "aftermath" of the removal of the mold from the fiberglass duct.  It is not a pretty sight.  Below are a few shots of the 3 inch diameter CAT hose that was hand-held into position in the lower cowling and then "strapped" with duct tape to hold its shape.  It took both sets of hands of me and my wife to complete that wrestling process which hopefully explains the lack of photographic evidence.

Even though the duct tape was thoroughly coated in paste wax, there was no easy coaxing of the hose from the curved, cured surface of the fiberglass duct.  As a result, the CAT hose had to be carefully destroyed by pulling the wiring reinforcement to free it from the fiberglass.  I guess it would be obvious to other clever folk that it was coming out no other way.

A shot of the finished duct and its semi-destroyed mold...and then a shot of the duct itself.

Alignment marks to show where the ellipse will be cut from the lower portion of the upper cowl.

A rough mockup and check of dimensions of the duct/oil cooler/cowl fitment.

A head-on shot of the assembly...and a few others.

Next, the ellipse (cylinder intersecting a plane for you math majors out there) was approximated and transferred to the cowl and then the cutting began.

A few shots of the duct work poking out of the upper cowl...

The trim line is marked on the duct, where it intersects the cowl.  Once it is temporarily glassed into the cowl, it will be trimmed and then the intersection filled and sanded to finish...I hope.

Viking Engine Safety Alert

From the Viking Aircraft Engines web portal, dated April 7, 2014:

Viking Safety alert
Take a look at your belt idler pulley.

• Remove the pulley after loosening the belt
• Be sure the bearing is Loc-Tited to the aluminum pulley 
• Do this by removing the snap ring to see if the bearing will move in /out
• If the bearing is solid AND you see traces of locktite around the edge, inspect every 100 hrs
• If loose, clean with acetone
• Apply green cylindrical retaining locktite to bore 
• Install bearing
• Wipe excess LocTite'
• install bearing
• Re install pulley as before
• Snug alternator belt and tighten alternator
  
  
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  After removing the idler pulley, I proceeded to examine the bearing/pulley assembly and found that no amount of hand pressure would move the bearing from the bore.  I called Jan and he advised to gently heat the bearing to less than 300 degrees and lightly tap on the bearing.  If it remained in the bore then the assembly is good to go.  If it came out, then application of the Loctite 680 would be in order.  The picture below shows the tools required for the procedure.
  
  
  
  
  After heating to "slightly too warm to leave your hand on", I gently tapped on the bearing with a plastic mallet and 25/32 socket and witnessed some movement.  A couple more taps and the bearing was in my hand.  I noticed that there seemed to be some residue from something that had been in the bore with the bearing.  It did not fully cover the circumference of the bearing, so I have to assume that if the residue is cured Loctite, that it did not fully work its way around the bearing.  Don't know if that is significant or not as the capillary action could probably yield any variety of flow patterns.  The shots below illustrates the residue on the bearing's outer surface.
  
  
  
  
  
  
  
  
  
  
  
  The Loctite 680 is on order and will be here by the weekend, so the re-installation will occur then.  More posted at that time.
  
  
  A few days later...
   
  LocTite 680 arrived and I began the process of reassembly of the idler pulley.
  
  
  
  
  A blurry shot of the cleaned bearing with a ring of 680 coated around the perimeter.
  
  
  
  
  Careful placement of the bearing in the bore, a couple of good wacks with the plastic mallet and the bearing was seated.  The c-ring pliers did the trick of securing the bearing into place.
  
  
  
  
  After the idler pulley was bolted back into place, the serpentine belt had to be tightened.  You cannot see it in any of my pictures, but before loosening anything, I marked a line with a Sharpie of the intersection of the alternator and engine brackets so I could return the system to its previous factory setting.  The shot below shows a custom tool I fabricated from an old garden implement, with a 5/16" steel shaft, which was the precise size required to leverage force on the alternator and engine brackets.  There is not much clearance, but it was enough.
  
  
  
  
  
  The final picture is just another side view showing the business end of the garden tool lever in position to tighten the alternator down.  I should also mention that there is a second bolt at the top of the alternator which acts as the pivot.
  
  
  
  
  
  I should be good to go now - Viking safety alert has been completed!

Upper Engine Cowling, Part 1

After getting the lower cowling established and installed to the firewall, it was time to assess the fitment of the upper cowling.  Below are a couple of pictures of the overlap between the halves.

First order of business is to establish a template for the cutline between the lower and upper cowl halves.  I used the green painters tape to establish a 1 inch boundary along the lower cowl.

Next, the upper cowl was lowered into place with the spinner template to hold a common position between the halves.

 

The green tape was also used as a marker for the upper firewall/cowl junction.

I never did get a picture of the second layer of green tape on the upper cowl overlaying the lower cowl's green tape.  With everything in place, it was time to begin marking the cutline along the second layer of green tape, which was projecting the edge of the lower cowl upon the upper cowl.  I used an Exacto knife held on its non-cutting edge to scribe a cutline in the upper cowl.

Next, I sprayed some black paint on to the cowl's scribe line to try to get some contrast to aid in seeing the precise location.  I had mixed results with this technique and eventually ended up just lightly scraping it off.  I just ran another length of tape along the scribe/cutline to visualize where to cut.

After making the cut with my ever faithful Dremel tool, I decided to begin drilling the hinge line to see how close I was able to mate the cowl to the upper firewall edge.  I actually was quite pleased with the result.  I had to just smooth out a few spots with a sanding block and it all came out pretty nice and tight to the edge.

More clecos as I move along the periphery drilling the two hinge lines.

All holes drilled and cleco'd.

Now it was time to cut and test fit the cowl halves with their respective hinges.  Below is a shot of the pilot side getting its hinge drilled and cleco'd into place.

Lots of holes and clecos!  I put a rivet in every "link" of the hinge line in all locations, especially as needed in the areas with a tighter radius.

A shot of the solid riveting of the hinge to the cowl.

 

Hinges in place on the lower cowl.

Hinge in place on the upper cowl/upper firewall.

An important shot follows.  The hinge pin that comes with the assembly is .089 inches in diameter.  Unfortunately, I have not been able to use that pin to mate the hinges that either attach the cowling to the upper firewall or the cowl halves to one another because of the severity of the curves.  The hinge pin will just not make the tight radius bends.  I resorted to ordering some smaller diameter piano wire (0.071 inches diameter) to join the cowl to the firewall and the cowling halves together.  The penalty one pays for such a "maneuver" is the resulting photo below.  You will readily note the 1/32 - 3/64 inch gaps that now appear with the sloppier fit between the hinge halves using the smaller diameter piano wire for the hinge pin.  I don't know if I will be able to overcome this unsightly limitation.  It will definitely require more work to see if there are any other options.  I am not a real happy camper.

The upper cowl half now gets its hinge drilled and cleco'd into place.

 

Rivet time!

Next up were the corners of the upper cowl where they meet with the lower cowl/spinner area.  This nasty vertical split line needs all the help one can muster to make it look like a tight joint.  I resorted to some backing plates with a Southco fastner (quarter turn) assembly riveted to the lower cowl.  Below is a shot of the blank, before riveting the Southco fastener.

Backing plate assembly riveted onto lower cowl to facilitate a tight joint with the upper cowl.

Backside of the backing plate with the business end of the Southco fastener "nutplate".  (I later ended up discarding the Southco fastener assembly in favor of a conventional nutplate and #8 machine screw).

The finished joint.

A relatively uneven split line...but it was the best I could manage.  I do not like this cowl with the vertical jog in the split line - a very poor design if I say so myself.  The next generation RV-12 cowl from Viking does away with this approach in favor of a more conventional "continuous" split line (although it is still not a straight line!).  I may want to pursue the second generation cowl at some other point in time, after I see one up close and personal.

Its a decent "5-foot" cowl job...I hope.

And another other "hindsight is 20/20" viewpoint.  The reveal of the prop extension is uneven from top to bottom by probably 1/8 inch.  I was so worried about the lack of any excess material on the lower cowl (I did not have any to trim off!) that I mounted it as it was cut from the factory to the firewall.  I should have probably trimmed off 1/8 inch or so, to allow the upper cowl to reach it evenly.  Or more precisely, I probably should have added another 1/8 to 1/4 inch to the backplate of the spinner (plywood) template, to push everything back toward the firewall.  As it stands, I have about 3/8 inch clearance between the cowl and the face of the prop extension as shown below.  This may prove to be a problem I had not anticipated....time will tell the tale.

The requisite "Jimmy Durante" nose shot.

Another backing plate assembly was needed at the firewall shelf and the upper cowl.  The picture below details my approach.  Again, a Southco fastener assembly was incorporated into the backing plate, which was later replace with a conventional nutplate and #8 machine screw.

Installation of the backing plate, pilot side of the firewall shelf.

 The next task was to incorporate the NACA inlet ramp into the upper cowl for air induction to the throttle body, with air filter.  Careful measurements were made multiple times both with the upper cowl on and then off.  Measure three times, check it twice, cut it once.

A close up of the cleco'd assembly on the top of the upper cowl.

The inlet ramp attached from the inside of the upper cowl.

Yet another glamor shot of the cowling...subconsciously hoping it will grow on me and I will like it better. Next up will be the struggle to concoct a duct from the upper cowl to the face of the oil cooler.