Wheel Pants and Gear Leg Fairings: Down the Rabbit Hole

I figure I can save someone a headache. After so many, I’ve learned to look forward, read blogs and Van’s Air Force threads, and hold my tongue in the right place. So, let’s take a shot.

I recommend doing this before mounting the engine. Leveling the fuselage is much easier when it doesn’t have 300 pounds hanging off the front. Either way, we need to level the fuselage with tires off the ground. Choose your poison but make it safe. The tools chosen worked for me.

Time to spend some money. There are lots of ways to jack up the airplane and level it with the tires off the ground, but I found this the safest. Here’s a list:

• Thick Kneeling Pad Extra Large
• One HF Motorcycle lift
• Two V Head Pipe Stands
• 0.25T Lever Block Chain
• Klein Tools 93LCLS Laser Level
• One heavy weight (100 pounds)
• Hunk of chain
• 4x6x8
• 2x6x8
• Scraps of quarter-inch plywood
• Scraps of Fiberfrax or other cushioning material
• 1/4×36 all-thread
• Nuts, washers, homemade shims, and brackets

First, the garden kneeling pad. You will be crawling on hands and knees and lying down a lot. Do yourself a favor. Buy a pad. You’re welcome.

The rest is pretty easy to visualize with the photos. I fabricated two wood blocks for the jack stand saddles. They support the fuselage on a section of plywood to distribute the weight under the center section spar. Some leftover Fiberfrax was used for padding. This setup is really stable. I will keep it at the hangar for future use.

The hydraulic lift was required to get the fuselage high enough to slip the stands under. The cradle is sections of the 4×6 and 2×6. The cradle is all bolted together with all-thread to the jack using some scrap aluminum angle for brackets. You could use almost any jack or even an engine hoist, but the fuselage is very unstable until there are stands under each side. Be very careful.

The only place we can lift the fuselage safely is underneath the center section spar. I put the jack back under after the day is done, just for added insurance. The last thing anyone wants is the airplane falling.

The jack stands are easy to adjust precisely to level the fuselage. They have a screw-type post with a big handle.

Nosewheel airplanes will require about 100 pounds of tail weight to pull the nose up and level the longerons. Tailwheel airplanes will require a support, but consider a similar setup with some weight to make sure the nose will not tip over. That would be a shame. An easy option would be a big bucket filled with concrete with a hunk of chain in the middle. Let it set up and you have a nice weight with a built-in chain. I do not recommend anything that involves using a bag of this or that or the bucket handle. Make something strong. I had a farm equipment weight—about 200 pounds. The weight has been buried on our property for over 20 years. I knew it would come in handy.

The mini winch easily pulls the tail down to level the longerons using a chain bolted to the weight. Plus, it ratchets in both directions. No sudden release like web ratchets.

Level the fuselage both ways with tires off the ground. It doesn’t have to go up very far. Just a few inches till the tires are clear of the ground.

Now grab that garden pad, lie down under the fuselage, and mark the center of the fuselage in a few places: forward, center, and aft. Van’s really helped us out here. It’s pretty easy to measure and find center. Apply a strip of yellow Frog Tape over the marks. Measure and make lots of marks from forward to aft, then connect the dots and draw a centerline nose to tail. You could use the laser, but this is the reference line for everything that comes after, so we want it as precise as possible.

Time to play Star Wars. I really like the Klein laser level—it is self-leveling and it has horizontal and vertical laser lines, but it also has a vertical spot. Set it up under the fuselage forward or aft. Line up the spot right above and line up the vertical line along the fuselage centerline. Transfer the line to the floor. A strip of Frog tape works well. While you’re down there, see if you drilled the drain holes in the fuselage. If not, add that task to the list. Fiberglass parts are calling.

Van’s wants us to start with gear leg fairings, but there’s no way to get them the perfect length without pants. Grab a pant and start fitting. The gear leg and tire need clearance. Trim in small increments. When you’re happy, we need to find center on the pant forward and aft. Aft center is easy. Measure and mark the aft edge center both vertically and horizontally. Forward center is tricky. I used a piece of coarse sandpaper taped to the floor. Hold the pant vertically from the aft edge, like a pendulum, and swing it both directions side to side, slowly lowering till it scrapes the sandpaper. Take a look—it should have two nice scratches to draw a center point.

Refer to Drawing “C2 Main Wheel Fairing Side View.” On my RV-7A, “U-808” bracket is aligned to the joggle flange edge on the aft pant. It is a perpendicular reference line. Check your plans. I used the laser level mounted on a tripod with the vertical laser line aligned to that edge. Prop the pant on the bench till the laser aligns with that edge. Adjust the laser up or down till the horizontal laser line is aligned to the aft center point. It should project to the forward center point. Adjust the pant till the level lines are aligned vertically and horizontally. Make tick marks then draw the line along the side. This method worked great on the left side and right side. Top and bottom are easy. Measure from the horizontal side centerlines and make a mark center top and bottom. Use the laser to shoot a line connecting the aft, middle, and forward tick marks. Make a bunch of tick marks in between, then extend with a straightedge. Repeat to make a bottom centerline fore/aft. Use the inboard centerline to draw a grid of 1-inch squares. Pick the size you want. 10×10 inches is plenty. It’s not necessary unless you plan to fabricate intersection fairings.

Now the fun begins … I fought with the pant for days. It has to be aligned in three axes. Longitudinally (yaw) to match the fuselage centerline fore/aft, level to the longerons fore/aft (pitch), and axially (roll) to match the camber of the wheel/tire. The wheel pant is round and floppy, so the slightest touch throws it out of alignment. No way to drill it without it moving. Here’s what I did.

I borrowed this idea from Mike Starkey. He got it from Steve Barnard. Whatever, whoever, thank you. It saved my bacon.

The jig is amazing, but I made a few changes and ended up happy with Version 2.

Spend more money list …

• 1x6x24 hardwood
• 1.5×1.5×24 angle iron
• 1.5 W x 1.5 H x 8 L zinc-plated steel perforated-slotted angle (twice the length of the main wheel pants plus a few inches)
• 6 ea 6-32 x 1 1/4 screws
• 6 ea 6-32 locknuts
• 4 ea 3/8-16 x 4 carriage bolts
• 4 ea 3/8-16 nuts
• 3/16×24 polished steel rod
• Scrap aluminum angle and flat stock
• Clamps

First the jig. I used oak. I prefer hardwood for jigs. Cut the 6×24-inch plank into two pieces for the vertical braces. The two vertical braces need to be higher than the pant centerline plus a little. Twelve inches works fine. Cut the 1.5-inch angle iron piece in half, 12 inches each. Steel is handy because it can be tapped and the threads won’t strip easily. They are end braces. Draw centerlines on the two end braces and mark one end brace for holes for the leveling legs and vertical brace screw holes. Three holes for the vertical braces and two holes for the legs. Holes for the vertical braces can be equally spaced. Holes for the legs need to be 5/8-inch from the edge so the holes in the slotted angle steel side braces will line up.

Start with #40 pilot holes. Clamp the pair of steel end braces together and match drill the holes into the other end brace. Separate, clamp, and drill the other set of holes. The reason is it makes them identical. It’s handy and saves labeling them. Now lay the end brace on a flat bench and use it to match drill one vertical brace for the mounting screws.

Clamp the two vertical braces together and match-drill the other. Finish drilling the end braces and vertical braces to full size. Drill the holes for the vertical braces #29 for #6 screws. Drill the end brace leg holes 37/64-inch so they can be tapped 3/8-16. Cut the perforated-slotted angle in half or cut to a length a few inches longer than the main wheel pant.

Drill two holes dead center in one vertical brace, 4 inches and 10 inches from the bottom. Drill additional every inch in between. Clamp the two vertical braces together so the mounting holes are aligned, centerlines perfectly aligned, then match drill the previously drilled holes. Enlarge the holes to 3/16 inch for the 3/16-inch polished steel rod. Cut between the holes with a jigsaw to form a slot for the pin. Make sure the pin can slide up and down in the slot. Use a file to finish the slot while they were still clamped. The long slot will work for both main and nose pants. Tap the leg holes in the end braces 3/8-16. Our jig parts are ready.

Cut two 12-inch pieces of the polished steel rod. Grab some scrap 6 inches long and make pin clamps. I used some aluminum angle for the outside and 1/8-inch flat stock for the inside. Drill a 3/16-inch hole for the pin in each. The angle and flat piece will be clamped to each vertical brace to lock the pant position. The angle outside and flat piece inside lock the pin square to the vertical brace while allowing the pin to be positioned up and down in the slot and rotated.

Let’s build this thingamajig!

Assemble the jig. 6-32 hardware to hold the vertical braces to the end braces. The 3/8-16 carriage bolts hold the end braces to the slotted steel side braces. The carriage bolts work well as legs. Add nuts to lock the assembly together. Add some centerline markings to each side of the end braces. Oh boy, the jig is ready.

It is handy to have the brace level so the vertical braces are perpendicular to level. All measurements are made using the laser line. The wheel pant floats in the slots and is free to rotate or move up and down. The holes in the slotted side braces allow for adjusting the length of the jig for main or nose wheel pant.

Now we need some other doodads … wrap the tire with yellow Frog Tape and draw a line dead center by spinning the tire while holding the pen centered.

Make a spacer block per plan and drill a #41 hole in the center. Draw crosshairs on a piece of white Gorilla Tape and attach the spacer to the tire so the crosshairs match the centerline of the tire. Refer to your drawings to locate where the hole in the top of the aft pant will be drilled for the spacer block. Drawing “C2 Main Wheel Fairing Side View.” On my RV-7A, “U-808” bracket is aligned to the joggle flange edge on the aft pant. The center hole can be measured from the flange edge then the measurement transferred to the top of the pant. Easy. Drill a #41 hole per plan. Drill the 3/16-inch pin holes in the pant fore and aft exactly at the center points.

Measure the distance from the fuselage centerline on the floor to where the line on the tire intersects the floor and draw a line on the floor fore-aft matching that dimension. Painter’s tape works well. Several marks are enough to align the laser and draw a line.

Remove one leg off the jig. Separate the parts and slip the jig into place. Bolts (legs) can go in from the top or bottom if the holes are tapped. Nuts lock the bolt position and clamp parts together. Assemble as you like.

Cleco the aft pant to the spacer block on the tire and slip the pant into place while rotating the tire so the spacer is at the top. The spacer block with hole centered forces the top of the pant to stay aligned to the centerline of the tire and spaced correctly. Slip the scrap angle over the pin then slide the pin through the vertical brace. Slip the flat scrap piece over the pin then insert the pin into the aft pant. Repeat with the nose part of the pant. Cleco the pant together.

It helps to level the jig. Just level the sides and end braces. The vertical braces will end up perpendicular. The jig end braces each have a centerline. Measure from the end brace centerline to the tire line on the floor. Match the dimension fore-aft. The wheel pant is now aligned to the centerline of the fuselage (yaw). Pretty cool, right?

Use a mirror to look underneath and check the pant centerline is aligned to the tire centerline. Rotate the pant (roll) on the pins till the line matches the line on the tire. This step aligns the wheel pant to the camber of the wheel/tire. The top is locked to the centerline. By rotating, the pant aligns to the camber of the wheel/tire. Pant trimming may be needed. Keep at it till the pant fits. Once it fits, use a piece of dowel wedged between the tire and the pant to hold the pant in the correct camber. Place it at the bottom of the tire so the pant can still be aligned to the other axes.

Set up the laser level from the side, placed on blocks so the vertical line is where it belongs per plan and the horizontal is near the fore-aft centerline. It doesn’t have to be exactly at the horizontal center. It’s actually easier if the laser line is slightly above or below the centerline. Measure the fore-aft centers of the pant from the horizontal laser line and make them match. Clamp the pant position with the two braces clamped to the vertical braces. The wheel pant is aligned to longeron level (pitch). Verify all the dimensions. Mark the floor so you can get close to perfect if you have to disassemble to cut something. Reassemble and verify again.

Drilling is tricky. Use a light and tiny bit. Once you hit a hole, it can be drifted to center. Add the screws. Done!

Draw lines on the pant to mark the mounting bracket edges. We need to fill the gaps between the brackets and the inside of the pant. You could bend the bracket, but the holes won’t match. This is easier and stronger. Before you disassemble, grab a 3/4×3/4-inch block of wood. Use it as a spacer to draw a line around the bottom of the pant. Slide it along the edge against the tire while drawing a line on the pant. The resulting line will be the gap recommended between the tire and the edge of the pant.

Take it all apart. There is probably a gap between the pant and the brackets. The screws will distort the pant and probably cause cracks if the gap is not corrected. Screw bosses are the fix. Go to the neighborhood pharmacy and ask for a 20 ml syringe. Cut the needle flange off leaving the tip. Drill a #30 hole either side of each screw hole to inject flox. Scuff the inside and clean. Apply packing tape to the brackets. Reassemble with waxed screws but leave them loose. Check all the measurements and verify the position again. Mix epoxy with flox and cabosil and squish it into the syringe. Inject it into the holes. About 5 ml per injection is enough to make a temporary boss. We want to fill the space without changing the dimensions. It should be clamped in position. Cure. Remove the wheel pant. The injected flox inside is probably not very pretty, but it should be smooth near the screws. Grind off the excess, reinstall the waxed screws, and apply more flox to fill voids and shape it into a nice round pad. Press a strip of packing tape over the area to ensure the boss retains its original shape matching the bracket.

I wanted screws on the outboard aft pant bracket, so I drilled the holes for #8 screws and installed MK2000-08 (short single leg) nut plates on the brackets. They are tight, but they fit and it’s much stronger. Also, I don’t have to fight with installing and safety wiring that bolt every time the wheel pant is removed. Reinstall the wheel pant with screws. It should be rock solid. Time to move on to the gear leg fairings and intersection fairings.

Cut the gear leg fairing per manual and plans. It will probably be a bit too long. I bought RV Bits Intersection Fairings for my RV-7A, so I have no plans to make molds and layup the fairings. They fit. No need to reinvent the fairing.

I fabricated two upper leg fairing attachment clips. I didn’t like the idea of attaching a leg fairing using a finger of fiberglass per Van’s plans. See drawing. These work much better. The breeze clamp is still used, but it holds the aluminum clamp. The fairing is held to the clamp with screws and nut plates. Pretty solid and adjustable.

The upper intersection fairing is bonded to the gear leg fairing so the clamp holds everything at the top. The lower intersection fairing is bonded to the pant. The gear leg fairing is captured by the lower intersection fairing and floats at the bottom inside the lower intersection fairing.

Van’s method for aligning the fairings must have been written before laser levels were invented. Feel free to crawl around drawing lines on the floor and hanging plumb bobs. There’s an easier way.

Once you have the gear leg fairing cut, slip it in place. We need the leg fairing in trail aligned to the fuselage centerline. Pick a dimension from the fuselage centerline to a spot near the middle of the leg fairing. It doesn’t have to be an exact location, so use an arbitrary measurement that is easy to see on the tape. Make some tick marks on the floor. Lay a tape line down over the tick marks. Measure and draw a new line from the gear back to the tail.

Set up the laser level. Love this thing. Shoot the crosshairs right on the forward side of the leg fairing so the vertical line is visible on the floor and the crosshairs on the forward center of the fairing. It’s easier mounted to a tripod because it allows you to adjust the laser so it matches the lines on the floor and the crosshairs are right on the forward edge of leg fairing.

Set up a vertical pole. The wife’s broomstick works well, but ask first! A bucket of kitty litter works for an adjustable stand. It needs to be straight and plumb. Use a level to make it plumb. Line up the center of the pole on the laser. Mark the vertical pole with the crosshairs matching the laser lines. Leave it all set up.

Next comes the intersection fairings. They will foul up the measurements anyway, so it’s easier to get them ready and bond them along with all this adjustment business.

If you plan to lay up the upper and lower intersection fairings, follow Van’s procedure. Remember, time spent on the mold pays dividends on finish work, so take the time to make them perfect. I used RV Bits Intersection Fairings. They fit really well and are worth buying for the time saved. Once the upper and lower intersection fairings are done, it’s time to make everything fit.

Make notes of what areas need filler, what needs bonding epoxy, and where. Make note of what parts need to be protected from bonding so the assembly will come apart. I use waxed packing tape to protect areas and allow parts to separate. Draw a line on the fuselage where the upper intersection fairing will touch the bottom of the fuselage. The marks make it easier to apply tape where required. Draw lines on the gear leg fairings where the intersection fairing edges intersect. Disassemble and sand bonding areas with 80 grit. Clean the bonding areas. Apply yellow Frog Tape to the fuselage then packing tape. You don’t want anything permanently bonded to the fuselage.

Proceed with bonding. Feel free to do this in steps. Upper intersection fairing to the leg fairing first, then the lower intersection fairing to the wheel pant. The Upper intersection fairing is bonded to the leg fairing. It’s easier to get it perfect if it’s bonded then aligned and left to cure. I recommend a slower epoxy like West 206 or G-Flex. Remember, it needs to come apart at the aft edge seam, so add some waxed tape to the appropriate areas. You want the lower intersection fairing and wheel pant in place because it holds the leg fairing in position, and it will be bonded as well. The lower intersection fairing gets bonded to the pant. You can bond both at the same time but practice. Time goes by pretty quick.

Run a string around the fairing from the crosshair mark back to the vertical pole crosshairs. Measure the space between the fairing and strings and adjust the gear leg fairing so the distance is equal. The leg fairing is in line with the fuselage centerline.

Once it’s all perfectly aligned and clamped, drill three or four #41 holes near the trailing edge of the leg fairing and Cleco the edge together. The Clecos hold the edge in alignment. Drill several #41 holes for Clecos into the lower intersection fairing and both forward and aft halves of the pant. The Clecos help align and hold parts while they cure. The holes into the aft pant allow the aft half of the intersection fairing to be bonded where it belongs after it is cut. After curing, remove the forward half of the pant with the lower intersection fairing attached. Cut the lower intersection fairing in half matching the pant split line. Reassemble the pant and bond the aft half of the intersection fairing to the aft pant. Congratulations. The hard part is done. All the parts are bonded.

Time for the leg fairing hinge. Van’s calls for the gear leg fairing hinge to be oriented flanges forward, eyelets aft. It allows the hinge to be open a bit, making room for the rivet shop heads. That’s all fine. However, they don’t show the hinge position along the trailing edge. I assumed it would be aligned equidistant from the edge and started to install it as such. It’s not! Glad I stopped when something didn’t feel right. Notice in the photo where it was happy. Here’s the trick.

Cleco the leg fairing edge. The holes and Clecos hold the trailing edge in alignment. Mark the hinges and drill the holes #41. I am a bit OCD, so I mark and drill half a hinge, then flip it together with a shim and match drill the other side. Then I use the two halves to drill the other hinge the same way. Finally, I put the hinges back together the way they were and mark the holes with lines. Duplicate hinges.

Slide the hinge into the fairing. Let it settle into a natural position and hold it up to the light. Mark the lengthwise hole line at each end inboard and outboard. Just a tick mark. Remove the hinge and draw a line. Reinsert the hinge and drill. It’s a bit tricky with gel-coated parts. Slide the hinge out to an edge and mark the hole line. Repeat on the other end, then the other side. Draw the line. Measure where the first hole needs to be drilled and start there. If your measurements are accurate, holes should line up, or Cleco the hinge half in place and match drill the holes from the outside. Drill the bottom hole and Cleco, inboard and outboard. Repeat working toward the top and keeping the hinge straight. The rest is easy. Bond the hinge. Countersink the holes. Rivet.

I use G-Flex to bond the hinge, cure, then countersink the holes. G-Flex is very tenacious. It is far stronger than regular epoxy. You may want to trim the excess off the aft edge of the leg fairing at this point so it’s a nice airfoil shape. Blend the shape at the upper and lower intersection fairings by assembling and squishing some flox into the gaps. Remember to add some tape or the parts will get bonded together. Trim the hinge to length then make a 90° bend and drill a hole per plans to safety wire it.

Plans call for optional gear leg stiffeners. Recently my mentor came up with a really cool method to stiffen the gear legs. A section of 1-1/2 x 0.125-inch 2024-T3 cut to the length of the gear leg. It is attached using Adel clamps. The problem I found is traditional Adel clamps would not fit inside my leg fairings. I bought some 1.5-inch cushion clamps on Amazon and removed the cushion, then used them to make symmetrical clamps. The stiffener is drilled and mounted perpendicular to the leg.

The last thing is to drill the holes in the nose pant or tail pant for the tow bar. Grab that laser level again. Set it up on some blocks so the crosshairs are exactly in the center of the tow bar bolt on one side. Assemble the pant. The crosshairs point right at the spot for the hole. Bingo. Drill a pilot hole. Repeat on the other side. Remove and enlarge to 3/4 inch. Most Van’s RV tow bars are 5/8-inch ID and 3/4-inch OD. Some builders add a flange to the outside to protect the paint. That’s about it for fitting. Time to finish.

Here’s a tip for botched screw holes. Sometimes the holes don’t end up perfect. Lay some waxed packing tape over the gear parts. Enlarge the hole in the part as needed till the screws can be inserted. Install the part with loose waxed screws. Smear some flox around the hole. Align the part perfectly. Walk away. When it cures, the holes will be perfect.

Here’s a tip for adjusting fiberglass. Sometimes the parts don’t fit perfectly. Heat the fiberglass with a heat gun but not over 200° F. Clamp the parts and cool. Perfect fit.

The rest is finish work. Rough sand and clean the inside of the pants. Brush a coat of neat epoxy. Cure. That’s fine for the inside, but feel free to paint if you like.

The outside is just like any other fiberglass finishing. Refer to “Canopy Skirt Part 2 & 3.” Thanks for tuning in. See ya when I see ya.