SECTION 10
ENGINE MOUNT, WHEELS, BRAKES AND FAIRINGS
RV-8/8A
10-9
8-s10r9 7/11/11
RV-8A MAIN WHEEL FAIRINGS
The RV-8A uses tapered rod gear legs with integral axles. Details of fitting the main wheel fairings are shown on
DWG C2.
The VA-157 wheel fairing consists of two pieces, the VA-157A forward half and the VA-157B aft half. They should
mate as accurately as possible. Because of the variations possible in fiberglass moldings, the first step must be to
make the halves fit. Use coarse sandpaper glued to a straight stick as a disposable file to remove any material that
prevents the halves from matching smoothly. Typical areas that might need some extra work are shown on Details
D and E; the inside radius of the flange on the rear half, the inside of the front half where glass cloth layers overlap,
etc. Take the time to custom fit the halves of your fairings as exactly as possible.
Drill and cleco the VA-157 fairing halves together. Begin at the tops of the fairings and work down the sides to help
minimize bulging and mismatch between the fairing halves. Space fasteners per Section A-A. Do not install the
second fastener up from the bottom on the inboard side of the fairings as this part of the fairing will be cut away to
clear the axle. The fairings as supplied are symmetrical (no right or left hand fairing) but the asymmetrical
installation of the fasteners will establish which fairing will be installed on the right side of the aircraft and which will
be installed on the left.
Attach front and rear halves of wheel fairings to each other as shown on DWG C2, Sect. A-A’. Mark a lengthwise
centerline across the top of the assembled fairing.
The airplane will need to be supported on jacks to get the wheels on and off the axles. Unfortunately, you may
need to remove and re-install the wheels a few times while getting the bracket-to-disc gap just right. Use caution
while the airplane is on jacks to be sure that it will not tip or fall off the jacks.
Install U-810-L and –R Brackets to the U-403 Brake Mount Flanges using qty 3 each: U-408 Spacers, AN4-11A
Bolts, AN365-428A Nuts, and AN960-416 Washers. There should be 0.032” to 0.094” gap between U-810 and the
brake disc when the wheel/brake assembly is installed.
Raise the airplane on jacks so the tires are just off the ground (zero to 1/16” gap). Level the airplane (longitudinally
and laterally) at the upper longeron. Once again, use caution while the airplane is on jacks! Be sure that it will not
tip or fall off.
Attach U-808 Outboard Brackets to the VA-106 Axle Nuts using AN4-5A Bolts and AN960-416 Washers. There is
not a right hand or left hand U-808, but the brackets do have a top and bottom to them. The longer leg of U-808
goes to the top. Using a carpenters square or drafting triangle on the floor, rotate U-808 so the forward and aft
edges are perpendicular to the floor. Tighten the bolts.
Place a small piece of 1 inch thick wood/metal/plastic on the top of the tire. This spacer established the correct
vertical position of the fairing relative to the wheel/tire. (The 1” dimension assumes a 14” diameter tire. The spacer
thickness should be varied to account for tire wear or inflation pressure.)
Duct tape the spacer to the top of the tire.
The inboard forward edge of the aft fairing must be locally trimmed to clear the axle. The wheel fairing is positioned
correctly in the fore/aft direction when the forward edge of U-808 lines-up with the molded in “step” located
approximately 1” aft of the forward edge of the aft fairing (see DWG C2, Detail C).
Center the rear half of the fairing over the tire while using the spacer to hold it in the correct vertical position. Locate
and use some blocks of wood/metal/plastic to place under the aft end of the fairing to position the center of the aft
edge of the fairing roughly 8 5/8” off the floor (see Wheel Fairing Side View). Mark the area of interference with the
axle, remove the fairing, locally trim a small amount of the fairing, re-position the fairing over the wheel, re-mark and
trim as required to achieve the correct final position. Trim the minimum required to clear the axle as this will make
the shaping of the clay mold for the wheel fairing to gear leg fairing intersection easier.
When the weight of the airplane is off the gear, the wheels naturally camber inward as shown on DWG C2, Section
A-A’. The vertical axis of the fairing is intended to be aligned with vertical axis
of the wheel and tire.
... not
perpendicular to the ground. The tire tread provides a good alignment guide. The centerline on the top of the
fairing and center of the opening on the bottom should align with the center of the tire.
When the aft fairing is located vertically (by the spacer on top of the tire), fore/aft (by alignment of the “step” with the
forward edge of U-808), approximately leveled (by the blocks under the aft end), and aligned with the tire, drill and
cleco it to the U-808 bracket using the pre-punched holes in U-808.
U-808 mates to the wheel fairing in a region where the fiberglass thickness is changing. This will cause
misalignment of the bracket, so a few plies of fiberglass cloth must be bonded to the inner surface of the aft fairing
to make the thickness constant in the two areas where U-808 touches the fairing. Use coarse sandpaper to
roughen the surface of the fairing --really roughen it, don’t be shy --before bonding patches of fiberglass cloth in
place with polyester resin.
RV-8/8A
SECTION 10
ENGINE MOUNT, WHEELS, BRAKES AND FAIRINGS
10-10
8-s10r9 7/11/11
Locate an approximately 1” wide shim thick enough (0.032” to 0.094”) to fit tightly between the U-810 bracket and
the brake disc. This shim will keep the bracket from deflecting excessively when drilling through from the outside of
the fairing. Scrap pieces of aluminum with strips of duct tape added to achieve a snug fit work well.
Attach the forward half of the fairing to the aft half. Now carefully adjust the fairing position until it is aligned with the
aircraft centerline both in a horizontal plane (see DWG C2, Section B-B)
and
in a vertical plane (see wheel fairing
side view). Drop plumb bobs from the center of the fuselage, fore and aft, and mark the position on the floor. Snap
a chalk line through these marks, transferring the centerline to the floor.
With the fairing held in its final position, drill and cleco the fairing to U-810 in four places (two front and two rear). It
is easier and safer to initially drill the holes #40 and then work up to the final #20 size. There are a couple of ways
to locate these holes:
Option 1: Use your “sharpie” pen to make four ink “dots” on U-810 where each of the four fasteners will ideally be
located. Sand away the white gel-coat from the areas where the fairing touches the bracket so the bracket and the
ink dots can be seen through the translucent fiberglass.
Option 2: Create a transfer template that uses the shop floor and axle to index to the correct hole locations in the
bracket.
When the holes are located, reinforce the area about three inches around them by laying up 2 or 3 layers of
fiberglass on the inside of the wheel fairings. Enlarge all holes to final size and remove the wheel fairing. Install
K1000-08 Nutplates to U-810 using AN426AD3-5 Rivets. Attach U-808 to the aft half of the fairing using
AN426AD4-6 Rivets. Remove all blocks, spacers, shims, etc. and install the wheel fairing to the airplane.
INTERSECTION FAIRINGS
To fully fair the landing gear, small intersection fairings cover the intersection of the gear leg or gear leg fairing and
wheel fairing, and the gear leg/fairing and fuselage. Because of the variation between individual airplanes, these
are best made in place.
A mold is made of oil based modeling clay. This can be the common modeling clay found in toy stores, or more
professional variety used by commercial designers. The clay is applied between the gear leg and wheel fairing or
fuselage and formed to a pleasing shape by hand or with any plastic or metal tool. A wet spoon works well.
The clay is oil based and is a natural parting agent. However, since the intersection fairing must part from one or
more of the adjoining metal or fiberglass parts, it will be necessary to use automotive wax, PVA (a special liquid
parting agent) or brown Mylar packaging tape on these parts to prevent adhesion.
A lay up of three thickness of 9 ounce fiberglass cloth is about right for intersection fairings. After the initial lay up
has cured, several more brush coats of resin are applied to fill the cloth weave. The final coat of resin should be
“finishing” resin which cures to harder finish, making sanding easier.
The upper intersection fairings are not permanently joined aft the gear leg. The natural flexibility of the fiberglass
allows them to be opened and removed if necessary.
The intersection fairings for the gear leg/wheel fairings are intended to become an integral part of the wheel fairing,
so sand the fiberglass surface of the wheel fairing with 60 grit sandpaper until all the gel coat is removed and
fiberglass strands start to show. Clean with acetone to improve adhesion.
Lay up the fairing as one piece and when it is cured, split it top and bottom at the wheel pant joint, using a die
grinder and cutting disc. The split can be made by carefully using a small cutting wheel in a Dremel tool. To protect
the gear leg fairing, a 3/8 inch wide piece of scrap 0.016 or 0.020 aluminum which has had one end sanded to an
edge can be slipped under the edge of the uncut intersection and the gear leg fairing at the split line. If the cut is
started at the top of the intersection, the aluminum can be pushed in as the cut progresses down the intersection.
Be very careful not to damage the gear legs or brake lines.
FINISHING THE WHEEL FAIRINGS
After the wheel fairings are fitted, it is necessary to remove them for sanding, filling and paint preparation. If the
initial molded shape is not accurate enough to sand smooth, more fiberglass build up can be added, or a BONDO
type filler can be used, and then re-sanded.
This can take longer than most people realize, but it is necessary to achieve a good finish when you paint. It will
also cure you of any lingering desire to build a whole airplane from fiberglass!
When you put everything back together, remember to install and safety wire the inside brake pads and install the
permanent cotter pin in the wheel nut before re-installing the wheel pants.
