December 2011 Archives

I started working on the wingtip lights tonight.  I'm going to fabricate a reflective backing for both sides of the recess, so I was fairly generous with the cutout so that I can easily position the light.  I'll trim the backing to tightly follow the lights.  I don't want to determine the final position until the nav/strobe light is attached and the lens cover is trimmed so that I can make sure there is no interference.  This is approximately where the light will end up though.  The is substantially farther forward than the stock lights which should provide better lighting directly in front of the plane.  The stock light position puts the bulbs a good 4" farther aft which causes the side of the recess to shade the area directly in front of the plane.

Once I have the lens trimmed, it looks like I can probably push the light even farther forward.  I'm going to try and get it within about 1/4" of the lens.  Since the light runs really cool, I don't have to worry about overheating the lens on the ground.  In flight, there's obviously enough airflow that I wouldn't have to worry about heat anyway.

I adjusted the lens until it looked like it would precisely follow the curvature of the outer edge of the wingtip and then taped it down.  I used some masking tape to mark the cut line.  The lens will pull back farther after it's cut, so this will just be a preliminary cut line.

I played with some tin snips along the edge, and they made perfect cuts without any hint of cracking the plastic, so I used them to cut out the lens.  This was far better than using the cutoff wheel since I could basically trim right to the line and then touch up the edge with some sandpaper to remove any microscopic burrs that could create stress risers and lead to cracks down the road.

With one edge of the lens aligned with the flange around the recess, it looks like I'll need to trim about 1/8" off of the other edge to allow it to drop behind the lip.

My Nav/Strobe Lights arrived from Aircraft Spruce today.  I used the adaptor plate and gasket and installed them to the landing/taxi light housing.  I hooked them up to the plane to verify everything works properly.  Holy shit these things are bright.  You can't be looking anywhere near these things when the strobes go off; it is blinding.

Next up, I drilled the rudder bottom fairing and installed a couple of 4-40 nylock nuts.

I anchored the nuts using a couple of screws and some safety wire.

I then mixed up some 5 minute epoxy with flox and covered the nuts to anchor them inside the fairing.  After the flox cured, I removed the screws and temporarily installed the tail light to ensure the nuts were secure.

Finally, I took one of the lights and installed a waterproof molex connector so that all of the connections can be made at once when installing the wingtip.  I was only able to do this on one of the lights before running out of steam.

More Work on the Oil Door

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I drilled some extra holes in the hinges and then mixed up some epoxy and flox.  I glued and then riveted the hinge on with some soft rivets. 

Next, I cut holes for a couple of hartwell latches.  These are perfectly flush with the surface of the oil door and hold it really tight.  These needed to be mounted in this orientation because of the curvature of the oil door.

I installed a connector on the tail light along with a piece of heat shrink over the wires.  Once the rudder is installed permanently, I'll install this on the bottom fairing and hook it up.

I decided to make a little progress on the oil door tonight.  I fabricated a spacer out of 0.063" aluminum to pull the oil door in tighter at the hinge line.

You can see at the hinge line that the door in nice and tight.  Without that spacer, the flexibility of the door and the force of the hinge spring was causing the door to bow out just slightly here.

I mixed up some epoxy/flox and riveted on the oil door latches.  I then placed a couple of layers of 8 oz cloth with a 1/8" fiber core for stiffness.  This will substantially stiffen the oil door to prevent it from bowing out in flight.  To ensure an even tighter seal, I've slightly flattened the oil door (that's what the blue tape is doing).  This will ensure that when the bottom is latched, the middle of the door will be tightly pressed against the cowl.

I also put a couple of layers of fiberglass over the side of the hinge bonded to the cowl.  The top layer you see in both layups is peel-ply to wick away excess resin.

I took off the peel-ply and cleaned up the fiberglass a bit.  I'll need to do a bit more work to clean this up, but it made a big difference in the door stiffness already.

I picked up some two-part expanding polyurethane foam at TAP Plastics and poured some in a box that looked about the right size to form the oil cooler plenum.  This needs 24 hours to cure before I can start shaping it.  I fully expect that this first piece will be practice, and I'll have to make another plug before I can layup the fiberglass over it.

I installed the fittings in the oil cooler tonight.  The top fitting is a standard AN822-8 elbow, but the bottom fitting is an AN826-8 tee with the pipe thread on the run.  You can also see that I trimmed part of the oil cooler flange to provide a little more clearance with the firewall.

Here's a better shot of the tee fitting.  The blue tape covers the flare port that will connect to one of the oil cooler lines to the engine.  The other flare port has an AN929-8D cap that can be removed during oil changes to drain the oil from the cooler and lines.  Without this, at least a quart of oil would remain in the cooler and lines during an oil change.

I fabricated three spacers that will used when installing the oil cooler.

They will fit between the flanges (along with some washers) to allow the mounting bolts to support both the front and back sides of the oil cooler.

I fabricated a small oil cooler support plate and painted it (I'll show a picture tomorrow).  While waiting for the paint to dry, I decided to install the fuel overflow tubing.  I used a piece of 1/4" ID Tygon tubing to run from the AN842-4D fitting on the fuel pump down to a piece of 1/4" tubing on the firewall.

The tubing is held on to the fitting with a piece of safety wire that is double wrapped around the tubing.

At the bottom end, I bent a short piece of 1/4" soft aluminum tubing so that it cleared the engine mount tube and poked through a 1/4" hole I drilled through the firewall flange and hinge.  I slipped a short piece of Tygon tubing over the aluminum tubing and zip-tied it to the engine mount.  I then used some safety wire to attach the Tygon tubing from the fuel pump to the other end of the aluminum tubing.

Drilled Wings for Wingtips

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I'm going to be using hinges to attach my wingtips.  This necessitates drilling additional holes in the end of the wing so that the hinges are attached with rivets spaced more closely together.  Most of the holes already pushed in the end of the wing skins were about 2.5" apart, so I used a rivet spacer to drill additional holes between the prepunched holes.  The hinges need to be spaced back a bit to account for the thickness of the fiberglass tips.  I'm going to use 2 layers of 0.025" alclad, so I laid out and started cutting the strips.  This was brutal on my hands though, so I didn't get through all of them tonight.

Worked on Oil Cooler Plenum

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I riveted the additional bracket onto the oil cooler and reattached it to the engine mount.

There will be one more adel clamp and bolt when the oil cooler is installed for good.  This is just installed temporarily so that I can fabricate the plenum.

I cut down the foam block a bit more and then determined where the butterfly valve would need to be positioned.

Afterward, I did some further shaping of the foam to define the final shape of the plenum.

Here's a better shot.  The bevel cut on the left edge allows the plenum to clear the engine mount tube.  I'll probably tuck a small foam wedge there so that the plenum extends under the engine mount tube to allow air to flow through the entire oil cooler.

I trimmed the edges of the large aluminum area washers that surround the vent tube ports on the side of the fuselage.  I then primed and installed them

Finally, I covered the oil cooler plenum and butterfly valve with packing tape so that I can layup some fiberglass over it.  Because of the compound curves of the mold, I had to use a number of narrow strips to avoid wrinkles.

Glassed Oil Cooler Plenum

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I hot-glued the form down to a couple of spacer blocks and then glassed the plenum.  I used about four layers of glass, but I only have 3oz glass on hand.  I'll probably need to add quite a few more layers (or step up to some 9oz cloth) to make this stiff enough.  The outside is covered with peel-ply which should leave a finish ready to bond additional layers to.

I finally riveted on the flap hinge.  This has been on my to do list for weeks now, but the wings are mostly stored under a tarp beside my house, so I have to pull them around to the driveway every time I want to work on them.

I also made a little more progress on the hinges that will be used to attach the wing tips.  I taped a couple of the spacers to the hinge and them clamped it to the wing skin.

After drilling, deburring, dimpling, and countersinking, I riveted it on.  Notice that the wing side of the hinge starts with an eyelet at the trailing edge.  This is so that the hinge pin can be pre-loaded on the wing so that it's ready to go when the wingtip is set in place.

I also pulled the oil cooler plenum out of the mold (well, mostly pulled the mold out of the oil cooler plenum) and then test fit it.  It looks like it fits pretty well, but I'll have to do a little adjustment.  As I suspected, it's also way to flimsy right now due to the lightweight cloth I had on hand.  I have some 9oz cloth on order.  A few more plys of that should stiffen this up nicely.

Here's a shot down the inside.  With the butterfly valve open, the air will have a nice clean shot at the oil cooler fins.

With the final location of the oil cooler and ducting determined, I could finish wiring the EGT and CHT probes.  I decided to run the wires inside of the oil cooler ducting since they could be better supported by the engine mount.  I trimmed the wires to length and added knife connectors.  These are covered by the heat shrink in the lower left.  The wires are secured in a couple of spots along the engine mount with adel clamps along with the ignition sensor, fuel flow, ammeter shunt and starter contactor sense wires.

Where the wires exit the lower adel clamp, the EGT/CHT wires turn left and follow the lower ignition wires.  The ignition sensor wire follows the starter wire forward and the other sense wires follow the starter wire aft.  Now that the final position of these wires has been determined, I can finally hook up the other ends to the various devices.

I fabricated several 26AWG fusible links for the sense wires connected to the starter contactor and alternator shunt.  Here's the one for the starter contactor.

This attaches to the right post on the starter contactor so that the VP-X knows when the starter is engaged.  You can see the two additional fusible links below the starter contactor.  These connect to the shunt.

Here's where these fusible links attach to the shunt.  Before connecting these wires to the shunt, I attached the battery charger to the alternator side of the shunt to determine the correct orientation.  Attaching the two sense wires to the wrong sides of the shunt would result in a negative current indication from the alternator.  If I didn't determine the correct orientation now and got it backward, it would require reversing the sense wires at the EMS end which would be challenging once for the forward fuselage skin is riveted on.

I finished up the fuel flow sensor wiring run by crimping knife connectors on the wires from the EMS and attaching them to the wires from the FT-60 (red cube).  I covered each of the knife connectors and the whole bundle of connectors with some heat shrink tubing and secured the wires with some Tefzel zip-ties.

The bundle of ignition, EGT and CHT wires running aft from the #4 cylinder weren't well supported.  I riveted a K2000-3 nutplate to the side baffle and used a two-wire adel clamp to secure the bundle to the baffles.  This prevents these wires from flexing down and contacting the #4 exhaust pipe (or flexing up and contacting the baffles under negative G conditions).  Other than hooking up the starter wire just before first engine start and the coax wires to the electronic ignition coils, I believe all of the firewall forward wiring is complete.  Other than final hookups of wing and empennage components (lights, roll servo, OAT probe, etc.), I believe all of the firewall aft wiring is complete as well.

Continued Trimming Baffles

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No pictures today, but I resumed trimming the baffles.  This was an iterative process that involved using paper clips along the top edge.  They're pushed down when the top cowl is installed.  You can then measure down from the top of the paper clip a bit to determine where to cut.  The plans specify to trim the baffles to clear the top cowl by 3/8"-1/2".  Since I'm installing a plenum, I went to 1/2" since the plenum with stick up 1/8" or so.

Finished Trimming Baffles

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I finished trimming the baffles to clear the top cowl by 1/2".  I'll still probably have to trim them a little more to follow the shape of the plenum since I'm fabricating that on a mold that I didn't make.

Afterward, I fabricated a couple of these little clips that keep the forward and aft cylinder baffles tight together while still allowing them to move independently.

My engine uses cylinders from ECI that have tapered barrel fins.  This saves between 5-6 lbs of weight, but complicates the baffle installation.  The premade baffles are designed for non-tapered barrel fins, so they have to be modified to seal properly.  ECI provides a template for building a filler piece to close off the tapered end and to fill the wedge shaped gap along the bottom.  I didn't like their template for a couple of reasons, so I decided to just make my own.  First up, I used some safety wire to pull the inner baffles tight against the cylinder barrels without twisting them.

I then used a piece of manila file folder to trace the shape of the inner edge of the baffles.

After adding some ears and cutting it out, here's the template for the #2 cylinder.  I then repeated the process for the other three cylinders.

After transferring the templates to some 0.032" 2024-T3 aluminum sheet, I cut them out.  Here's the #4 cylinder filler piece clecoed in place.

You can see that the ears are bent around the outside edge of the baffles.

Where the baffles end, a tapered shim needs to be fabricated so that the baffles seal tight against the fins.  This forces all of the cooling air to go between the fins instead of around them.

This shim will be riveted to the flange on the end of the curved portion of the baffles.

I left the new piece long while fitting it.  I'll trim it off flush with the existing flange now that the holes are drilled and it's position is fixed.

Here's what it looks like with everything riveted together.

From the other side, you can see the ears of the side piece and the rivet that ties it to the tapered shim.

The modifications for cylinders 1-3 are pretty much the same.  The modification for cylinder #4 is quite a bit different.  It wraps much farther around the cylinder and the width of this side piece gets larger near the top.  I trimmed it to roughly follow the ear that rests above one of the cylinder mounting nuts.  All of the gaps will be filled with high-temp RTV silicone.

This picture gives you an ideal how the shim follows the taper of the barrel fins.

Here's the completed #2 cylinder baffle mod.  I still have the #1 and #3 cylinders to do, but that will have to wait until tomorrow.

My hopefully final hose order arrived from Bonaco today.  First up is the upper hose to the oil cooler.  This comes straight off the back of the engine above the left mag.  I'll add a couple of adel clamps to tie the oil hose to the breather tube.  This will keep the hose from rubbing against the breather tube as well as stabilize the breather tube a bit better.

That hose runs just inside the forward engine mount tubes and connects to the upper oil cooler port.  I'll add another adel clamp here to secure the oil hose to the engine mount.

The lower oil cooler hose routes around the back of the oil cooler and then connects to the 45º angle fitting above the propeller governor.  I'll cut a relief in the oil cooler flange to keep this from abrading against the hose.  I may also add an adel clap to tie the hose to the firewall.

I also replaced the fuel pressure hose with one that has a 90º end on it to better clear the oil cooler.  I'll also have to trim the oil cooler flange here to clear the hose.

After installing the hoses, I finished up the baffle mods.  Here's the modification for the #1 cylinder.

And here's the mod for the #3 cylinder.  Overall, these really weren't that bad to make.  I probably spent 6-8 hours total fabricating and installing these.  I'd definitely recommend ditching the plans from ECI and just making your own templates.  You'll have to do that anyway for cylinder #4, and it's pretty quick to just do it all the way around.  I also highly recommend making them in two pieces and riveting them together with the single rivet in the corner.  This is much easier than trying to get all of the angles exactly right with the single piece that ECI specifies.

Put Together "The List"

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I spent some time over the last couple of days putting together a list of all of the work necessary to complete the plane.  The current estimate is approximately 460 hours of work, but that includes work that many builders save until after first flight such as gear leg fairings and wheel pants.  I'm sure there are some missing items, so the list will likely get longer, but I think the estimates are fairly conservative.  At my current work level, that's still over 6 months of time before first flight though.  I plan on doing my transition training with Mike Seager in OR as close as possible to first flight.  He's booked up about 3 months in advance, but it doesn't look like I need to schedule with him just yet.

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This page is an archive of entries from December 2011 listed from newest to oldest.

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