Plenum Tug-of-War

With the -7 build in Michigan while Dolly and I are in Florida, a project for the winter was to fabricate a fiberglass plenum lid, the oil fill door and some HDPE firewall and baffle wire pass through. I brought engine measurements (32″plus by 18″plus) and the top Vans cowl with us.

The oil door was fun, really. First try was two layers of 6 oz cloth cast onto the cowl over clear packing tape and Mother’s Brazilian canauba auto wax. Two layers was too thin both in flexure and contour with the surrounding cowl surface. The second try at seven layers was stiff, but too thick. Like ‘Goldilocks and the Three Bears’ the third try at four layers was just right but will need some anti-flex reinforcing.

I purchased yards of cloth and West Systems epoxy at the new West Marine store located about a mile from here. It seems that from now on the WM stores will only carry smaller packages of cloth, not large rolls.

The outer surface of the RV-7 cowl received from Vans had pits reflecting the shape of the hexagonal cells in the sandwiched layer. After three thin screed layers of epoxy/microlite and two layers of rolled on clear epoxy the surface is ready for spray primer. Of course each layer was preceded by block sanding, but we don’t like to think about that.

After all that I felt ready to tackle casting the plenum lid on the inside of the upper cowl. Clear packing tape and auto wax were again used for mold release. Six pieces of 6oz cloth were cut oversize (I only used five), along with a layer of 2mm Soric core material.

Blue sharpie lines on the cowl marked where the composite layers were to be placed. A single large piece of nylon sail cloth peel ply was laid over the waxed release tape and the blue lines traced. Epoxy was poured over the first layer of glass, and a bit on the second glass layer. Air was worked out with a plastic spatula. The third glass layer also required some epoxy. Then the Soric was placed and a 3″ paint roller used to force contact and squeez excess epoxy to the edges. Corners of the Soric were lifted to verify epoxy was covering the bottom of this layer. The next two layers of glass and peel ply were applied in a similar manner.

The plenum lid easily popped from the mold after twelve hours. It was left for a day before our Tug-of-War and trimming loose cloth from the edges. The finish is beautiful. Weight at this point is 34.4oz. This is undoubtedly heavier than if the assembly had been vacuum bagged and resin infused. However, we can tolerate forward weight to offset the relatively light weight lithium battery and Catto prop.

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Lycoming IO-360 M1B 180hp Engine

August 3, 2016

Our engine was ordered after returning from Airventure ’16.  It was delivered to the Dalton Airport on the 18th.

I had expected a wooden crate.  Instead it was in a foam filled cardboard box strapped to a pallet.  The box was opened that day to check for any damage. The engine was in a large plastic bag that also held four silica desiccant pouches and a color changing humidity indicator card.  We did not open the big bag.  Apparently Lycoming squirts some foam into the cardboard box and lets it harden before setting the engine.  Then, the space around the big bag is filled with liquid foam and the box closed.  It was well protected.

October 20, 2016

 

 

 

 

 

 

 

 

 

 

 

 

The engine was picked by Dan Willoughby’s Engine hoist for unpacking.

It arrived with two Slick magnetos, a prop governor oil pump, and a horizontal oil filter mount.  Before mounting the engine to the airframe, these appliances were replaced with two electronic pMags and a 90deg. B&C oil filter mount.  The prop governor oil pump was removed to save weight as we will install our Catto fixed pitch prop.  I also installed a 40 amp backup alternator on the vacuum pump pad in the rear accessory case.  Dessicator plugs were installed in the top of each cylinder.  All changes were detail documented in the engine logbook.

Dan Willoughby and Mike Goulet helped with installing the bottom two engine mount bolts.

November 7, 2016
Weather was getting colder.  The project area was cleaned up, tools put away, and we prepared for our relocation to Florida for the winter.

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Baby Gets Legs

October 5, 2016

Please forgive the misleading headline of this post.  “Installing a motor mount and adding landing gear legs, wheels and brakes” just doesn’t work as a title.

Master and starter solenoids, the battery box and cabin heat valve were installed on the firewall. Then the motor mount was added.

Four ratchet straps were hung over a pole barn truss to lift the fuselage.

Notice the recessed cover had been riveted into the center of the firewall.

After a little excess powder coating was removed from the gear legs they slipped nicely into the mount tubes.  The retainer holes were reamed to 0.3115 inches for the close fit bolts which slid in with taps from a plastic hammer. Nuts were torqued to 190 in-lb, including 50 in-lb turning drag.

 

Beringer brake caliper mount holes were drilled to the axles and reamed to 0.3115″.  Hubs/tires were mounted with brake discs safetied on the hubs with 0.40″ wire.

Baby’s got legs!

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Gluing the Rear Window

October 3 to 27,   2016

There was almost as much masking, sanding and fitting of the rear window as for the tip-up canopy.  The rear window fits over the top of the roll bar and under the fuselage skin.  The sides and aft edge of the window are trimmed to about an inch beyond the edge of the skin.

The front edge of the window is cut and sanded to match the aft end of the closed canopy.  With the tip-up closed and the window removed, a fine line is drawn across the roll bar just behind the tip-up to guide glue application.

Gluing was done after moving the project to the Dalton Airport.  SIKA glue application was similar to that used for the tip-up canopy. The rear window was braced against the clecoed skin using thin battens and a board resting on the baggage compartment top longerons.

The rear skin was riveted, and the Inner and outer protective plastic film replaced with food wrap on the outside of the window.

This post is not meant to be a step by step guide as to gluing the window. Adjusting the window placement during gluing is difficult. There were many opening and closings of the tip-up during the process.

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Building the Tip-Up Canopy

July 12, 2016 through October 8, 2016
Vans calls constructing the canopy, whether tip-up or slider, one of the most challenging aspects of the build. Vans is always right.

Our “tipper” began with drilling the HDPE blocks that are bolted to the fuselage and serve as hinge supports for the front of the canopy.  These blocks support retractable pins that hold the front of the canopy in place.  The retraction mechanism is controlled by a tee handle that may be pulled to release the canopy.  Builders who plan on doing aerobatics while wearing parachutes will place the tee handle on the instrument panel.  Not having those aspirations, our handle is on the sub-panel where it is accessible on the ground by first opening the canopy.

Continue reading “Building the Tip-Up Canopy”

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Flush Canopy Latch Handles

August 7, 2016

The standard Vans RV Canopy Latch Handle protrudes from the fuselage out into the air stream.  I purchased a JDAir system that is flush to the fuselage, sitting in rectangular slots cut in the skin.  The mechanism consists of a latch that is pushed in to release a handle that pops out of the skin. The handle can then be pulled to open the canopy.

The handles are fitted and bolted to doublers that will later be riveted to the skin.  Then, a metal template is cut and fitted to the handles.  The template shown above best positions the slot pattern that is transferred to the skin.

The slots are cut, and the latch mechanism is bolted to the doublers and riveted to the skin.  The above photo shows the completed flush latch handles at a later stage of the build.

This last photo, taken from the JDAir website, shows the cockpit side of the handles.

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New Air Compressor

July 09, 2016

Dolly’s 20 gal compressor failed in July.  I replaced it with this oil-less 150 psi unit from Harbor Freight.  It works as advertised.  I learned however that a lower-pressure higher-volume pump might have been a better choice.  Our air tools don’t need pressures above 60 psi, and this pump can’t keep up with our die grinder or finger sander.  It also runs longer reaching it’s non-adjustable cutoff pressure of 150 psi.  Fortunately it fits under the weather cover built for it’s horizontal tank predecessor.

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Emergency Locator Transmitter

July 3, 2016

For the RV-7 we purchased an ACK-04 ELT.  It transmits on 406 as well as 121.5 MHz. and connects to Garmin G3X providing  NEMA 0183 GPS position data.  The installation manual requires the ELT be mounted parallel to the aircraft forward axis; and also recommends it be near the rear of the aircraft.  Unfortunately a rear mount would make the transmitter inaccessible to CFIT survivors.

ELT ON TUNNEL COVER

I have chosen to mount the ELT on the tunnel cover forward of the seats.  While this may increase the risk of ELT damage in a CFIT, an impact of that magnitude would likely eliminate survivors.

TUNNEL REINFORCEMENT

Another recommendation is that the mounting provide deflection stiffness so spatial movement is no more than 0.1 inch under a pressure of 100 pounds.  The pictured reinforcing channels do that.

ELT AND FUEL BOOST PUMP & FILTER

The electric fuel boost pump is mounted on a separate section of tunnel cover.  An additional cover over the pump & filter will separate them from the ELT.

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