Airflow Systems

From RV10 Community Wiki
Jump to navigation Jump to search
Engine modifications
  • send the stock flywheel in for adding the serpentine grooves. Consider sending it away for anodizing afterwards.
  • install 4 Lycoming P/N 38-14 studs in engine block below governor
  • mount B&C LX60 60A alternator using bracket FK5402-4 on right side of engine (compressor goes on left side)
  • use Sky-Tec 149NL starter
  • route governor over the top of the engine using Vans bracket VA-153-PC
Governor
  • The governor control cable needs to be routed across the top of the engine. The manual states "Reroute the prop governor control cable over the top of the engine utilizing the Van’s Aircraft bracket, part no. VA-153-PA or VA-183-PC (depending on your need). Note in the photos that the bracket may require modification to clear the pushrod tube." Neither of those parts are in the Vans store. The part is now called VA-153-PC.
Outlets
  • The Airflow AC comes with a replacement for the top part of the baggage compartment bulkhead close-out. It is a flat part and has cut-outs for the air intake and cut-outs for two cold air output vents.
    With this setup, it becomes optional to feed an overhead panel with cold air but there are two more 2 inch outlets at the evaporator to feed an overhead panel. Note: The instructions still show a central single large outlet and a corrugated part but the kit contains a flat bulkhead close-out and two 2 inch outlets for the overhead console.

    Note: if you install the BRS parachute, two brackets block the area in the bulkhead for feeding air into the overhead console. So either just go with the two close-out vents or feed the air into the overhead console from the side / holes in the bulkhead more towards the sides.
Scoop / Condenser Mounting
  • Finding the center line of the scoop: one way of doing it: put the scoop on a wooden board, 16 inches wide with a marked centerline. Put the scoop on the board and check equal distance to the board edge at symmetrical points. Transfer the center line onto the flanges on both ends. Painters tape might be necessary as blank label to be able to see pen marks drawn on it rather than drawing directly on the slippery surface of the scoop.
  • Finding the center line on the bottom skin: running a cord from mid firewall to the tail tie down isn't really giving you good center line location precision where you need it. Rather the cord is merely a secondary tool to proof that a specific rivet is indeed on the centerline, or that the center line is indeed running between two specific rivets near where the scoop starts and ends.
  • The finish kit comes with spherical magnets (HW-00011) which can also be used here to place the holes around the scoop circumference where they don't interfere with ribs or other structures. The following pictures are just an example of a magnet pair being placed between two nutserts.

  • The Airflow scoop has a planar top flange for attachment to the bottom skin, however, the RV-10's bottom skin has a 2 degree bend around the middle of the scoop (at the rear wing spar).

    A good way to reshape the scoop is to heat up the scoop to around 133F and then jam high density foam into the groove above the inlet opening and continuing with additional foam in same groove around the sides to the bend point. This pushes the flange up in the forward section to better mimic the bottom skin 2º bend


  • Follow the manual and use only tiny amounts of Loctite 262 around the bottom end of the rivnut before inserting. The substance is etching and will eat away primer on touch. It will only harden in gaps under pressure. Excessive Loctite will never harden and should be wiped away. Loctite cannot be used to create a fillet.
  • You need a nutsert tool to place the nuts into the bottom skin, e.g. this tool (similar to a manual pop rivet puller) or this tool (twist type) with this adapter 8-32.
    If you have a hydraulic knockout punch tool e.g. this one from Amazon, you can make an adapter for pulling rivnuts by taking a 2 inch piece of a 3/4 steel rod, cutting a 3/4-16 male thread onto one end and an 8-32 female thread onto the other. Use several strong fender washers and two small washers to support the nutsert towards the punch tool or make a washer from 0.3 inch steel. Use a stainless steel 8-32 set screw as bolt. It takes some 6 full pump strokes to set the supplied nuts. Additional rivet nuts can be ordered from Aircraft Spruce.



  • The holes in the scoop need to be countersunk for Tinnerman washers. A great tool is Countersink 100º, No Nipple, 11.5mm dia., LC5 from Permagrit (they ship directly from England).
  • The manual has one drawing which shows the doublers are to be used for the condenser holes. The kit includes one set of doublers. Consider cloning the doublers and using them on the firewall and the condenser holes. The holes in the doublers are a bit too small for the 90 degree fittings when used for the condenser, so widen them accordingly. The doublers can be riveted to the inside of the bottom skin using 4 AN470 4-4 rivets:
  • In order to mark the two holes for the condenser fittings one needs to make a template. A good way is to first make very large holes roughly where they need to be, then pass the fittings through those holes (make sure they are perpendicular to the condenser), then take additional snippets that have half-hole cutouts at their edges and tape them to the template so the half-holes touch the fitting.
  • The manual doesn't state where left and right is on the master hose plan. Make your own drawing based on where you route the hoses. Keep in mind that the smaller port of the condenser is the output back to the dryer. The larger one is the input from the compressor.
  • Check the 90-degree fittings before attaching to the condenser as there might be white powder / residue inside from the soldering process. Can be removed with a round brush and blown out with clean compressed air.
Painting
  • Consider priming and top-coating the fuselage bottom skin that is underneath the scoop (primer alone is porous and not suited for wet areas).
  • The scoop needs to be painted before mounting it finally.
    • Rough up the gelcoat and fiberglass with sandpaper (150-400 grit).
    • Smoothen the seams between the different parts of the scoop.
    • Fill pin holes and rough areas with epoxy filler. Suitable filler is TotalFair. You can smoothen the surface and transition edges with a wrinkle-free glove finger wetted with 70% isopropyl alcohol. After curing, the filler can be trimmed using a flex shaft with a conical grinder, e.g. this grinder.
    • Consider creating a smooth transition between the entry opening and the inside walls using the filler.
    • Spray paint the scoop first with a filler primer. Fill pin holes and sand between coats. Suitable is Smooth Prime. Then put a top coat on that matches your later bottom skin.
Evaporator Shelf Mounting
  • The evaporator shelf touches the vertical bulkhead support on its front side and sits flush against the inside edges of the longerons. The manual states that this is roughly 3 inches back from the bulkhead but it's only 2 inches
  • The rivets of the flat shelf support are spaced with a different distance than the side / upper skin rivets that aren't riveted yet. Due to this, it's unavoidable that some rivets will be at the exact same location as the side rivets. New holes need to be found that don't have a conflict.
  • The evaporator shelf can be cut easily with a Dremel 543 Cutoff Wheel
  • The rivets supplied for mounting the evaporator shelf are usable but weaker than necessary. They have a marking of "OIDC" instead of a small center dimple. They are made of a soft alloy. Use proper aircraft AD rivets instead. The rivets are not used in a shear fashion, rather the shelf hangs off the rivets underneath the longeron. They need to be strong.
  • The kit has only one washer per bolt to attach the evaporator shelf to the side braces. Better to use a washer on the top and bottom to distribute forces across the soft fiberglass
Evaporator Mounting
  • There are a lot of loose ends when mounting the evaporator. The issue is that at the point where you would install the AC (before closing out the floor panels), the tailcone bulkhead does not have predrilled holes yet for the closeout panel as it comes from Vans. So the holes in the upper closeout that Airflow sends don't match up with any existing holes.
    1. Attach the 3D-printed inlet vents to the evaporator using the bulkhead cutouts for those vents to align them parallel and with the right distance between them. The vents are not symmetrical, there is a left and right one. Check the notch on the bottom to align with the seam of the evaporator housing. There are no extra pop rivets for the nut-plates, be careful that you do grab the nut-plate before setting the rivets. The screws are really hard to get into the nut-pates. Consider putting each nut-plate in a vice and test-driving the screw in once with a bit of lube and an electric impact driver before mounting them.
    2. Cleco the luggage floors in
    3. Deburr the lower close-out panel to avoid scratches
    4. Cleco the lower close-out panel's bottom edge to the floor panels / bulkhead
    5. Secure the lower close-out panel to the bulkhead so it lays flat on the bulkhead
    6. Screw the AC upper close-out panel and the stock lower close-out panel together at the 4 holes of the seat-belt cable guide (using the largest bolts you can find that fit to align the two)
    7. Clamp the bulkhead to the fuselage. Ensure it centered left/right
    8. Attach the front bracket to the evaporator.
    9. Use wooden shims to align the evaporator with the inlet vent holes. The front bracket needs to sit on a shim (about 0.675 inches) and the rear end of the evaporator needs to sit on a shim (about 0.98 inches). Make sure the evaporator doesn't sit too high as the pipe fixtures that stick out of the evaporator might then interfere with the J-stringer on the right side.
    10. Drill a hole on each side into the evaporator at the top hole of the rear bracket. Put an 8-32 nutsert anchor in, attach the rear bracket and mount the rear bracket on the shelf.
    11. Make a new front bracket that is 0.675 inches taller
  • The cables are brought out on the bottom. There is no grommet and the cables chafe inside the evaporator housing at the fan controller. Consider making a new hole at the top, install a grommet and bring the cables out there. Close the hole on the bottom with a piece of aluminum and 4 pop rivets.
  • The manual doesn't recommend what to use for sealing against air leaks. PERMATEX # 2 SEALANT seems to do a great job.
Hose Routing
  • Three hose diameters are in play which reflect the state of the coolant:
    • #10, the thickest, for when the coolant is all gas at low pressure as it comes cold out of the evaporator back to the compressor up front
    • #8, mid sized, for when the coolant is compressed, hot gas out of the compressor to the condenser/scoop
    • #6, the smallest, for when the coolant is mostly liquid out of the condenser/scoop to the evaporator via the dryer
  • If you want to route the hoses along the right side of the fuse, the thicker fitting needs to be on the copilot side (the Layout diagram shows it the opposite way).
  • There are two options for routing the hoses: through the tunnel or within the side walls. The kit contains only the fittings for the tunnel option (which needs "Z" adapters for the condenser; for routing in the side walls, you need plain 90 degree adapters on the condenser). Specify which routing you want when ordering. Airflow will exchange the Z fittings for 90 degree ones on request however they are made to order and it takes several weeks.
    This builder log from Allen documents using the tunnel: AC-line tunnel routing
  • When running the hoses outside the tunnel, they recommend running them to the right side of the firewall as the left side is busy with the oil cooler.
  • Note: If you use the Aerosport interior panels, keep in mind that the recessed area for maps / the cup holder occupies the space between the panel and the outer skin which is separated by U-profiles all around, where you would probably want to route the hoses through. There is room for one hose all the way on the top but a modification to the right side panel is need if you run the second hose underneath it.
  • No snap bushings come with the kit. You need to keep the holes as small as possible, however the hoses will probably swell a bit under pressure. A compromise is to use larger ones in non critical ribs and webs and smaller ones, or no bushing in the critical u-profiles above the main spar. Consider ordering
  • When picking a spot on the firewall for mounting the fittings, be sure that the engine mount doesn't interfere with the fitting / hose. The bulkhead fitting plus the hose fitting add to quite some length before making a turn. If you need less space, consider using a 90 degree hose fitting with integrated bulkhead mount, e.g. for the #10 hose, part SR1723 from AC Parts. If you buy fittings, they must be "reduced barrier" (thinner walls / smaller OD) and the o-ring type. For inside the fuselage, they should be aluminum with steel sleeves to be light but bulkhead through-wall fittings and fittings within the engine compartment are made entirely out of steel. Check with a magnet to keep them apart.
Crimping Fittings to the Hoses
  • A suitable crimper for the hoses is e.g. $224 at eBay: Standard and Reduced Barrier A/C Hose Hydraulic Crimper Kit with 7pc Die Set
  • Reduced barrier hoses, which are used for ACs, have a second liner on the inside of the hose to keep the gas from leaking. To protect the inner liner, the hose will go onto the fitting very easily, even with a bit of slack, this is normal. The hose sits tight on the center barb after the crimp.
Dryer Mounting
  • Mount the dryer as shown on the drawings of the manual (half way between evaporator and side skin). Make sure it stays clear of the seatbelt shoulder harness that passes through this area.
  • Don't install the pressure switch into the dryer! The dryer is pressurized with nitrogen and neither the caps at the in and out port, nor the cap for the pressure sensor must be removed until you are ready to fill the system. If you accidentally depressurized the dryer, it needs to be replaced.
  • One needs a 2.5 inch hole saw to drill the hole for the dryer. Missing in the list of tools needed for installation.
  • The manual shows a 90 degree fitting for the dryer with service port however the kit contains a 90 degree fitting without a port and a straight hose coupling with port. None of the drawings or pictures show this new variation. See also this FB thread. The kit now assumes, you mount the new inline service port at the front edge of the shelf wherever convenient.
O-Rings
  • It's optional but if want to lubricate the o-rings before assembly, use e.g this special AC oil from Amazon.
  • Replace any O-Rings that come on fabricated fittings as they have heat damage from the soldering process (e.g. the 90-degree fittings that go onto the condenser).
Torques

The manual doesn't mention any torques for the fittings. The internet provides vastly different values, potentially because there are aluminum fittings and steel ones (firewall and forward, use steel fittings):

Retrieved from "https://rv10.org/index.php?title=Airflow_Systems&oldid=2783"