Anatomy of the Zenith Nose Gear Action

The Zenith nose gear column is free to rotate and move vertically within the top and bottom bearings. The bearings and bungee pin are fixed to the firewall. Normally, the bungee pin—and thus the firewall—are lifted by the bungee because the firewall top ends are fixed to the nose gear column. As a downward force is applied to the front of the airplane, the nose of the airplane will lower and the nose gear bungee will stretch. However, the nosewheel steering rods stay with the nose gear column as the airplane lowers. (See “DIY Firewall Boots,” KITPLANES, September 2009.)

Bungee Replacement

1. Start by making the bungee tool (Figure 1 and Photo 1).

2. Hang some weight on the tail tie-down to lift the nosewheel off the ground. Two cinder blocks worked for me on my CH 701 (Photo 2).

3. Then use a utility knife to slowly cut through the old bungee (Photo 3).

4. Next, remove the nose gear steering rods. Also remove the lower nose gear bearing pieces (Photo 4) and the nose gear top retainer (some Zeniths don’t have these). Then remove the nose gear and old bungee.

5. Push the new bungee about halfway up behind the bungee pin, which is behind the nose gear. Thread the nose gear column through the lower part of the bungee and through the top nose gear bearing while capturing the upper part of the bungee in the hook on the back side of the nose gear (Figure 2 and Photo 5).

6. Reinstall the bottom nose gear bearing pieces and the nose gear steering rods. Put the lower part of the bungee (now on the front side of the nose gear) on the tool you made (Photo 6). Position the tool over the protrusion on the front of the nose gear and lift on the tool (Figures 3 and 4).

7. With a little tug, the bungee will slide off the tool, which can then be removed (Photo 7).

The post Sagging Zenith Nose Gear? appeared first on KITPLANES.

The main landing gear on the Zenith STOL CH 701 is sandwiched between the gear/strut fitting and the gear plate, but separated top and bottom with flexible spacers. Originally, layers of inner tubes were specified. Later I used automobile heater hose that had been cut lengthwise. The heater hose only worked for a while and then wore through at the upper contact point. Fortunately, Zenith now offers polyurethane spacers (Part Number 7L2-2A/1) that are fairly hard but still flexible. Here’s how I installed them on N701TX, my STOL CH 701.

First, I built a main gear jacking support. This tool is useful for more than upgrading the spacers; it also comes in handy when raising the airplane to remove a wheel for brake work, tire exchange, etc.

Using scraps from around the shop, I made the jacking support from a 10×18-inch piece of 1/2-inch-thick plywood, a 2×6-inch piece of 1/8-inch-thick aluminum plate (glued to the plywood), a second piece of 1/2-inch plywood measuring 3×12 inches and a piece of foam. The aluminum plate protects both the plywood and the 3/8-inch studs that are welded inside the gear/strut fitting. The foam protects the bottom of the fuselage.

After I built the jacking support, the next order of business was to chock the airplane on one side and remove the gear plate and bottom spacer on the other side. Warning! Do not remove the gear plates on both sides at the same time.

Place the jacking support and a jack under the 3/8-inch studs. You can now safely raise the airplane to gain access to the top of the main gear under the gear/strut fitting. The wheel will stay on the ground as the airplane rises, exposing the old top gear spacer for removal.

You may have to trim the new spacers to fit inside the gear/strut fitting and notch them to go around the 3/8-inch studs. The upper spacer notches are not centered, but are offset to reasonably place the spacer under the main load point of the gear/strut fitting. I trimmed one corner of the upper spacer so I could work it into place between the studs. Once the top spacer is securely positioned on top of the main gear, lower the jack so the airplane is resting on the wheel.

The new spacers are fairly thick, thus on N701TX the upper piece of my gear plate had to be separated from the bottom piece. This was simply done by drilling out the rivets.

Next, install the bottom spacer and gear plate and you are finished with the first side. To complete the polyurethane spacer upgrade, repeat the process on the opposite side of the main gear.

The post The Great Spacer Caper appeared first on KITPLANES.

During the summer, this had not been a problem. After taxiing, take off, flight and landing, the thump, thump was still evident. My solution would be to keep the tires off the hangar floor during cold weather with a custom jack.

Jack Detail and Parts Identification

Using 2x4s, 1x2s, hinges, .040-inch aluminum, and quarter-inch threaded rod, I fabricated jacks for the main gear legs. Because the Zenith is light, they’re designed to lift about 250 pounds each.

To raise the tires to clear the floor, I needed to lift the gear legs about 6.75 inches. The main lever is a 48-inches-long 2×4. The 1×2 lateral brace and stacked 2x4s provide the lift needed and are centered about 8 inches from the end of the main lever. The 1×2 lateral brace provides stability to keep the jack upright.

The main lever and lift stack are bolted together with the quarter-inch threaded rod. The aft block, a 5.25-inch 2×4, is attached with a hinge to the end of the main lever. The aft block folds back to allow the main lever to be lowered and placed under the main gear leg. When the gear leg is raised, the aft block is lowered to support the gear leg. The aluminum stop is screwed to the side of the main lever and assures that the gear leg will be properly positioned on the lever.

Using It

When raising the gear leg by standing on the long lever, I use my tow bar handle to pull the aft block forward 0under the main lever. It’s important to be sure you provide lateral stability and a positive means to assure the jack will remain in position under the gear leg. While this setup is quite stable, you need to be sure the airplane will not roll off the jacks. For your airplane, the amount of lift required will depend on the tire size and gear-leg-to-wheel attachment. In the end, I was able to build a pair of these jacks for very little money, and I’m sure they’ll prove their worth to rid my Zenith of the dreaded thump, thump.

The post A Fix for Square Tires appeared first on KITPLANES.

When I bought my CH 701 kit from Zenith, one of my options was the Aeroflash nav/strobe kit with the double flash. The strobe flashes twice very quickly and then repeats every second. The kit comes with a power supply for each wing and works very well. Together the power supplies weigh close to 3 pounds, and each draws 2.7 amps. I have a Jabiru 2200 in my Zenith CH 701 with an alternator that only delivers 10 amps. With strobes, navigation lights, instrument lights, instruments, radio (in receive), etc., my total load is about 9 amps.

With the advent of very bright LEDs, I decided it was time for the CH 701 to lose some amps as well as a few pounds (its empty weight is 580 pounds). I found some 10-watt, 12-volt, 900-lumen, pure-white (6000 K) LEDs. Experimenting a bit, I determined that 15-millisecond flashes separated by 0.1 second were comparable to the original double flashes from the Aeroflash strobes on my CH 701. Not only that, but the LEDs seem to be just as bright with much less power required.

The 555 timer integrated circuit is reliable and easy to use. Two resistors (R1 and R2) and a capacitor (C1) are the main ingredients for an astable multivibrator; this is just a circuit that continuously delivers a positive pulse, then goes to zero for an “off” pulse, and then repeats. Along with C1, R1+R2 define the length of the “on” pulse while just R2 and C1 determine the length of the “off” pulse. The “on” pulse is always longer than the “off” pulse. Picking the right values for R2 can make the “off” pulse much shorter than the “on” pulse. We’ll see why this is important in a moment.

If we want 15 millisecond flashes separated by 0.1 second, we have to drive the LEDs with the “off” pulse and use the “on” pulse between flashes. This means we must invert the output of the 555, or make the “off” pulse go high and the “on” pulse go low. This just takes another transistor and a couple of resistors.

Now we have the LEDs flashing for 15 milliseconds every 0.1 second—close, but not exactly what we want. What we need are two LED flashes and then a waiting period of about 0.9 second before they flash again. Therefore, we need to power the flashing 555 long enough for only two flashes, then remove the power for 0.9 seconds, and repeat. Remembering that we have inverted the flashing 555 output, the first output is a low pulse of 0.1 second, then high for 15 milliseconds, then low for 0.1 second, and then high again for 15 milliseconds. All things considered, about 0.3 second of power is required every second. Thus, the double flash will repeat every second. What we need is another 555 timer (for power control) with an “on” pulse of 0.7 seconds and an “off” pulse of 0.3 seconds. Again, inverting this 555 output, we can now power the flashing 555 for 0.3 second every second.

Circuit Diagram Details

Since the power control circuit is electronically in front of the flash timer, my circuit diagram puts these components at the top and are numbered first. We will call the power control 555 “timer 1” and the flash 555 “timer 2.” Q1 inverts the output of timer 1. Q2 is an emitter follower, which means it follows the inverted output of Q1 but has enough oomph to power the timer 2 circuit. Q3 inverts the output of timer 2. Q4 is a power transistor emitter follower, which can drive the 1-amp LEDs. Note that Q4, driven by Q3, gets its power directly from the 12-volt source. Although the LEDs are 10 watts, their duty cycle is about 5% and thus do not need a heat sink. Nor does Q4 need a heat sink. All of the resistors are 1/4 watt; the capacitors should be 40 volts or higher; Q1, Q2, and Q3 are 2N2222; Q4 is a TPI-120, which can handle 5 amps; and the D1s are 10-watt, 12-volt, 900-lumen, pure-white (6000K) LEDs. When installing the capacitors, be sure to honor their polarity (minus to ground). Most components are readily available, however, I found Q4 and D1 at banggood.com.

Making the LED Mounting Wedge

The Aeroflash xenon flash tube is mounted in a silicone wedge that fits snuggly inside the clear lens and aluminum base. The next step will be to fabricate an equivalent wedge for holding the LEDs. A couple of molds and a tube of silicone will work just fine. Start with the large mold and give the silicone a day or two to cure throughout and then add the second layer.

The LEDs are positioned back-to-back with the minus terminals at the top; these are connected together with a black wire. Each LED’s positive side is connected to a red wire. The LEDs are mounted on the silicone wedge, with the wires going through the wedge. Dabs of silicone at the base of the LEDs will hold them in place for insertion into the clear lens. Dabs of silicone will also anchor the transistors. For the Aeroflash red and green navigation lights, a ground wire is required.

To view the LED strobe in action on my Zenith CH 701, download the video file from Dropbox.

Although, I describe how to modify the Aeroflash unit for LEDs, the LED strobe can be implemented with any clear lens and lamp base.

The post Two Flash or Not Two Flash appeared first on KITPLANES.

The oil quantity in my Jabiru 2200 is just a little over two quarts, so every ounce counts. Occasionally and over time, oil from the filter can leak back into the sump and indicate a higher level. To assure the proper amount, I always check the level before and after each flight. However, when hot, the knob on the dipstick expands and is difficult to remove. After checking with other Jabiru owners, I found that mine is not an isolated case.

To easily remove the dipstick, I fabricated a tool from a 1-1/2-inch-long piece of -inch square steel tubing with 1/16-inch walls. By grinding and cutting, I was able to remove the purple area shown in the drawing from the square tube. A hole was drilled in the center of the top, then filed square to accept a 1/4-inch socket extension.

As you can see in the photo above, a short socket extension was bonded to the tool with epoxy. I then tightened two linked 1/4-inch hose clamps around the dipstick knob.

Placing the tool over the linked 1/4-inch hose clamps on the dipstick knob, I can easily remove the dipstick to check the oil level.

Materials List

• 1-1/2-inch length of 3/4-inch square steel tubing
• 1/4-inch socket extension
• 1/4-inch clamps (2 needed)
• Epoxy

The post Jabiru Dipstick Removal Tool appeared first on KITPLANES.

My Zenith CH 701 (N701TX) brakes had always been marginal during runup, and stopping on an incline required throwing a wheel chock out the door to block the nearest wheel. But I found a solution for these issues with a couple of upgrades, which we’ll take a look at in more detail.

Stopping Power

After landing and rolling down the runway, we use our aircraft’s brakes to slow down. What gives us the power to slow our mighty beast? It is mechanical advantage (MA). In physics and engineering, MA is the factor by which a mechanism multiplies the applied force. Of course, there is no free lunch. The input force must travel a longer distance (D1) than the output force (D2) to gain any advantage. At balance, if the input and output forces are multiplied by their associated moment arms, we have equal moments (much like computing the center of gravity of your airplane). Figure 1 shows a simple lever, and from this illustration we see that a beneficial MA is achieved when the input travel is much greater than the output travel. (Note: The direction of travel is not a factor, only magnitude of the distances traveled.) Mechanical advantage can also be determined from the length of the arms or the forces involved.

Figure 2 shows the geometry of the N701TX toe brake pedal and the master cylinder. Without going into a mathematical proof, I will just say that the more vertical the toe brake and closeness of the master cylinder, the better. In this configuration, the master cylinder downward motion is small compared to the toe-brake motion. But this difference, and the resulting MA, decreases as the pedal moves away from vertical. However, this is not critical, as the output motion of the hydraulic disk brake system is small, requiring only minimal input travel.

The next MA source is based on the implementation of the master and slave cylinders. Mechanical advantage for hydraulics is the ratio of the slave (aka wheel) cylinder piston area to the master cylinder piston area. Here is some good news: My brakes have dual slave cylinders on both wheels. Thus, I have twice the slave piston area providing twice the braking force. With diameters of 1.25 inch for the slave cylinders and 0.625 inch for the master, I have a hydraulic MA of 8. This relates to 0.016 inch of slave cylinder motion and 1⁄8 inch of master cylinder motion.

Now for the bad news. Figure 3 shows the moment arm of the N701TX tire tread (L2) to be much longer than moment arm of the brake pucks (L1) on the disk. Thus, the MA of this component is less than one. (Airplanes with small diameter tires can require less robust brakes.) During runup for magneto checks, I had to really stand on the brakes. Those big tires had way too much leverage to even think about going to full throttle when stopped.

However, there’s also more good news. Matco (the manufacturer of my brakes) has a master cylinder intensifier kit. By reducing the diameter of the master cylinder piston, the same hydraulic output force requires less pedal input force. Now we are getting somewhere. Figure 4 is a photo of the kit (courtesy of Matco). A master cylinder insert, smaller master piston, some seals and keepers make up the kit. I removed the master cylinder from the rudder pedal and secured it upright outside of the airplane. I removed the snap rings, cover plate and piston. Using a syringe, I extracted most of the hydraulic fluid. Per the accompanying instructions, I trimmed the cylinder insert to the proper length and slid it inside the master cylinder. After replacing the old piston with the new smaller one, installing the new seals, and returning the spring and cover, I was home free. I topped off the hydraulic fluid in the master cylinder, and, after pumping the pedal a bit, the brakes were solid; no bleeding was needed. I now have an increase in braking power of about 60%, with the master cylinders moving about 0.2 inches. All in all, N701TX is much more friendly during runup.

Parking Brake

Matco sells single and dual parking brake valves. In the park position, the valves will allow the brakes to be applied and will then hold the pressure to the slave cylinders. By turning the valves to the open position the brakes are released. With dual toe brakes, I would need two valves to lock both wheels. As my brake hydraulic lines do not run together, the dual parking brake valve was not an option. However, with a non-castered nosewheel, I figured locking one wheel should be sufficient for most needs.

First, I determined an out-of-the-way, but easily reached, location for the single valve. Two straight fittings (1⁄8 inch NPT to inch compression) were installed at the valve ends. A mounting bracket of 1⁄16 inch thick by -inch aluminum angle was fabricated and drilled for the valve mounting tabs and fuselage frame attachment. A 1⁄16 by 3⁄4 inch template was drilled to match the fuselage attachment holes. This template is used when drilling the holes in the fuselage frame. See Figure 6.

Figure 7 shows the drilling of the fuselage frame. If you want the holes in the right place, hold the drilling template in place with a clamp and then Cleco the first hole before drilling the second hole.

With the valve temporarily installed, the brake line is marked at the valve ends (flow arrow toward wheel). See Figure 8. Do not cut the line here, but allow inch on each end so the lines can be inserted into the inch compression fittings.

Remove the master cylinder from the brake and rudder pedals, being careful not to spill any fluid. Secure it to the outside of the airplane and upright, as shown in Figures 9 and 10. To avoid much fluid spillage when cutting the hydraulic line, the master cylinder should be slightly lower than where the line will be cut.

Using a razor blade, cut the line going to the wheel, insert it into the compression fitting and tighten (with open end of valve facing up), and cut and plug the line going to the master cylinder. Using a syringe, fill the valve body with fluid. Insert the line from the master cylinder into the valve compression fitting and tighten. I hung the master cylinder from the wing to allow air bubbles to move up the line as shown in Figure 11. With a screwdriver, carefully move the brake pucks away from the disk. This forces fluid up the line and any remaining air out of the open valve. Slowly, the bubbles should move toward the master cylinder and again alleviate the need to bleed the system. If necessary, cycling the master cylinder will seat the brake pucks, which can then be used to force any remaining air from the parking brake valve.

Finish up by reinstalling the master cylinder and attaching the valve bracket to the fuselage frame as shown in Figure 12. The system now works great, and there’s no more unwanted rolling when I depart the airplane.

The post Give Me a Brake appeared first on KITPLANES.

Whenever I encounter a pilot for the first time, the discussion starts out with flying but then might progress to amateur radio. A good many of these folks, especially the homebuilders, are amateur radio (ham) operators. Most are technically inclined and, early on, satisfied this propensity with a ham radio license.

Amateur "packet" radio began in 1980. Packets are short transmitted bursts of digital data. A short time later and to expand on a good idea, Bob Bruninga, WB4APR, developed the Automatic Packet Reporting System or APRS (www.aprs.org). Some now call this the Automatic Position Reporting System. The APRS can transmit (on a ham frequency) periodic real-time data such as weather conditions, text alerts or even GPS coordinates. What! GPS coordinates? You bet, and not only coordinates, but also altitude, heading, speed and time. Neat!

Figure 1 (above): N701TX’s flight path on August 23, 2010.

As with all ham radio activities, volunteers provide any and all facilities including fixed-based stations. But it gets better. The GPS packet data is transmitted on the VHF band and is received by a ham APRS station, which may either relay the packet or send it directly to the Internet for display on any computer in the world (http://aprs.fi). The specific VHF frequencies are standardized almost by continent (144.39 MHz for U.S. and Canada). When flying or driving in the U.S., tracking is almost a sure thing, especially so for flying.

This magazine first reported on APRS in aircraft back in the August 2008 issue ("Found From Space," Page 43), but since that time the available hardware has evolved. I’ll get into that in a minute, but first let me show you the benefits of airborne APRS.

Figure 1 shows my takeoff in N701TX from KBMQ, exiting the pattern and flying to the northeast. Prior to turning west, I executed a standard rate turn. As I was holding a constant rate of turn (a good demonstration of wind effects), the westerly wind elongated the circle to the east. I turned west, then south, entered the traffic pattern upwind, turned crosswind at midfield, flew downwind, base, final and landed back at KBMQ. The gray airplane symbol just off the runway is the last data point. The path shown is the connection of the received data points, based on time.

RTG and GPS units.

My APRS is set up to transmit every 90 seconds or when there is a ground track heading change of 30. The data burst is about 0.5 seconds at 10 watts. Because my unit does not listen for other transmissions but transmits in the blind, some packet collisions occur and are not received by the ground. The turning feature and a gap in data can be seen in Figure 1. By clicking on a data point, the information in the packet is displayed. By looking at points with different headings, you can get a sense of the wind speed and direction from the displayed GPS ground speed. By going to www.aprs.fi and entering my call sign (K5CEA-7) and then searching for tracks on a specific date (2010-08-Mon 23), you can view the packet data for each point in Figure 1.

Hardware

My APRS unit is the new Micro-Trak RTG (Ready to Go) by Byonics (www.byonics.com/microtrak). It is powered externally with 12 volts, is about the size of a deck of cards, has a small separate GPS receiver and 15.5 inch antenna cable. This unit includes the transmitter, packet/data converter and power supplies into one convenient box. Along with the GPS data, the RTG packet may contain comments such as the tail number, but it must contain the ham license call sign. Two configuration sets are available and can be modified using a home computer. I have both airplane and car data sets in my RTG. Other APRS units can even communicate with each other via text messages using a keyboard and text display. However, to keep it small, light and simple, I chose the RTG (about $200).

N701TX’s RTG and GPS receiver are Velcro-mounted in the baggage area (the GPS has a clear view of the sky). It is autonomous; there is a 12-volt outlet nearby that powers the RTG when the aircraft master is on.

The RTG antenna on N701TX.

Value Added

As with most ham activities, there is enjoyment to be had from employing technology as one goes about one’s daily activities. By reviewing the APRS data, you can evaluate the accuracy of instrument approaches, holding patterns, and you can gather overall flight performance data. Additionally, the folks who are at home can track your progress for both local and long cross-country flights. In a forced landing situation or worse, the aircraft’s location can be readily pinpointed.

All that is needed to get started is a Technician class amateur radio license (no Morse code; in fact, Morse code is no longer required for any level of ham license). Check out the specifics at the Amateur Radio Relay League site (www.arrl.org/getting-your-technician-license).

This is really a cool way to have fun, improve your flying skills, stay in touch and add to the safety of flight.

The post Hamming It Up appeared first on KITPLANES.

I fly my Zenith CH 701 from my airfield into a variety of airports, many with no services-not even wheel chocks-and certainly no step ladders. Before returning home, I like to know if I need to stop and get fuel for my next flight. But having fuel tanks in the wing, it is a bit tough to check the fuel level with my measuring stick. I do not trust fuel gauges, so I contemplated my options. This may sound a bit outbound, but being a fan of MacGyver, I decided to build a combination step stool and wheel chock. I scrounged up some -inch PVC pipe and fittings, a 10×14-inch piece of half-inch plywood, four X1 blocks, three 6-32 wingnuts, one 6-32×1.5-inch screw and 10.5 inches of threaded rod (See Figure 1). The fabrication of two end frames is described below. Separately, these can serve as wheel chocks, or connected together they can be legs for the stool.

Drill a 5⁄32-inch hole in the center of each T (See Photo 1). Then, by hand, countersink the hole inside the T with a 3⁄8-inch drill. (This makes it easier to insert the threaded rod into the T from the opposite side. See Photo 2.) Sand the end of one of the legs about 3⁄4 inch up the outside to allow it to easily be inserted into and removed from a cap. Slip on a cap and drill a 5⁄32-inch hole completely through the cap and the leg as shown in Photo 3. (This is where we will store the threaded rod and two wingnuts during flight.) Sand both ends of the crossbar so that without too much difficulty, it will slip into and out of each T on the end frames.

Glue the end pieces into the opposite sides of the Ts and then glue each of the legs into an elbow. Glue caps to the remaining three legs. Temporarily, place the crossbar into the center hole on one of the Ts and glue the elbows/legs to the end pieces with each cap touching a vertical surface and with the T about an inch out from the surface. (This offsets the legs a bit. See Photo 4.) Repeat this procedure to make the other end frame.

With the crossbar in the end frames, slide the 10.5-inch threaded rod through the end frame Ts and secure with the wingnuts. Invert the frame, and center it on the plywood. Drill pilot holes in the blocks and plywood as seen in Photo 5. My blocks are snug enough with the crossbar to keep it in place; otherwise, the plywood will stay in place once the stool is upright.

From above, countersink the holes in the plywood and then attach the blocks to the plywood using carpenters glue and drywall screws (See Photo 6).

Alone, each end frame can serve as a wheel chock (See Photo 7). For wheels smaller than those on my CH 701, both end frames can be used to block a tire.

For flight, the threaded rod and wingnuts are secured in the leg with the removable cap, a 6-32 screw and wingnut (See Photo 8).

The dimensions provided here are for my Zenith CH 701 and may be altered as long as stability is not overly compromised. The combination step stool and wheel chock is simple, lightweight and functional.

The post Dual Time appeared first on KITPLANES.

Several kit airplanes require you to think hard about anything that penetrates the firewall. In most installations, securing fixed components-wiring bundles, engine controls and so on-is relatively easy. There are plenty of methods, both homemade and off the shelf, for protecting these penetrations of the firewall.

But its a different story for components that have to move through the firewall, steering rods as an example. These rods connect the rudder pedals to the nosewheel strut and must be free to move through the firewall to do what they are supposed to do.

My Zenith CH-701 has two slots that are a half inch wide and 3.75 inches high. The steering rods have to move freely fore and aft as the nosewheel steers and, to further complicate things, must move vertically with each strut stroke.

Initially, I attached a rubber gasket to the firewall with slits for the steering rods. However, my Kidd carbon monoxide monitor occasionally showed peak readings of 25 ppm (parts per million). Although a transitory level of less than 30 ppm is generally safe, it was more than I was comfortable with. Taking a hint from a Sonex builder, I lowered this peak level by devising boots to seal the firewall openings. These were easily fabricated using fiberglass cloth that was impregnated with high-temperature RTV silicone sealant.

Boot Fabrication

Start by making a form that is shaped like the desired boot. It must match the hole in the firewall, be long enough to provide a smooth transition from the hole size to the diameter of the rod, and it must be able to accommodate the motion of the rod. To provide a flap for mounting, the form is extended an additional inch.

For the CH-701, I cut out a half-inch plywood form and wrapped it with a sheet of paper to make a pattern. Be sure there is an overlap of about inch. Small slices in the paper may be needed for it to conform to the boot form. Transfer the pattern to the fiberglass cloth with a felt-tip pen. To keep the cloth from unraveling, outline the pattern with a swath of silicone and let it cure before cutting the cloth.

Attach one edge of the cloth to the form with a silicone bead and let it cure. Then wrap the cloth around the form and secure the overlapping edge with a second bead of silicone, and let it cure.

Using a putty knife, spread and fill the cloth with silicone. It is best to do one side at a time, including curing. Any gaps in the boot can be closed with small patches of cloth as needed. For example, a narrow strip of cloth at the rod end of the boot can be added. Add silicone to any thin areas as necessary.

Before curing is complete, slide a putty knife between the boot and the form to ease subsequent form and boot separation. After the silicone has cured, peel the boot from the form.

Cut slits in the corners at the bottom of the boot such that the height of the boot equals the height of the steering-rod slot. Fan out these flaps, fill in with cloth strips and coat with silicone. Now that you’ve done all that: Fabricate a second boot.

Boot Installation

Make a cover plate from 0.040-inch aluminum to match the steering-rod slots in the firewall. Slide the boots onto each steering rod and secure them with the cover plate. The silicone side of the boot goes to the cockpit side of the firewall. I used 8-32 screws to attach the plate, though rivets may also be used. Push the small end of the boot forward to allow movement of the steering rod, and secure the small end with a nylon tie wrap. (The nylon tie is acceptable because it is on the cabin side of the firewall, remember.)

And there you have it. You’ve sealed the firewall and maintained the steering rods movement. Not a bad outcome for a few afternoons work.

The post DIY Firewall Boots appeared first on KITPLANES.

For slow approach speeds and landing on short runways, knowledge of the wind direction is essential. Sometimes my windsock, with its smaller size, can be difficult to see, especially in a slight wind. After studying the problem, I came up with a simple wind tetrahedron that is very sensitive (2 knots) and can easily be seen. Being bright white, 6 feet long and 2.5 feet wide makes it highly visible even from pattern altitude.

Materials You’ll Need

Start with a 6-foot length of white U-panel roofing material (normal width is 38 inches), then add:

• Two 10-foot lengths of three-quarter-inch, thin-wall EMT conduit
• One 4-inch steel electrical box blank cover (unpunched)
• One 4-inch steel electrical box cover with half-inch knockout (actual hole is about 7/8   inch)
• One 7/8-inch diameter metal disk (knockout) from the electrical box cover
• 1 foot of half-inch PVC pipe
• 1 half-inch PVC cap
• 1 half-inch PVC coupling
• 1 half-inch marble or ball bearing
• A 3-foot length of half-inch steel rod
• 6 feet of 2-inch steel pipe
• Three small hose clamps
• One metal or wood spacer disk with a half-inch hole and outside diameter to fit inside 2-inch pipe
• Three 3/4-inch aluminum angles 1 inch long
• Various sheet metal screws, bolts and nuts.

The U-panel will have a ridge down the middle. In the center of the U-panel (36 inches from either end) drill a 7/8-inch hole in the center ridge. From the outer sides of the middle ridge, draw lines to the far corners (Figure 1). The width of the ridge will be the nose of the tetrahedron. Use a metal cutting blade in a circular saw to cut the U-panel to make a triangle. Smooth any rough edges.

Bend the panel at a right angle along each side of the center ridge, keeping the top of the ridge flat. A perfect right angle is not necessary at this point. Cut two pieces of EMT 5 feet long. Screw these to the flat area near the bottom edge of the triangle on each side (Figure 2, Photo 1). Holding the bend to 90, measure the distance at the back of the tetrahedron for the EMT cross brace. Cut an EMT this length. Flatten the EMT ends a bit and screw the cross brace to the side EMT lengths.

With the tetrahedron on its back, use a framing square from the hole in the center ridge to determine where the steel electrical box cover (with half-inch knockout or 7/8-inch hole) will be located. Cut cross EMTs the appropriate length. Flatten the ends of the EMTs, screw the electrical box cover to the EMTs, and then screw the cross EMTs to the side EMTs. Save the half-inch knockout for later.

Drill a half-inch hole in the center of the 4-inch blank box cover, which will be the support and centering plate. Drill a quarter-inch hole in the center of one side of each of the three aluminum angles for the quarter-inch centering bolts. Space and mount the angles evenly (120) around the half-inch hole in the box cover, leaving enough room to fit over the steel pipe. Make the spacer disk (with half-inch hole) to just fit inside the pipe (Photos 2 and 3).

Grind an eighth-inch dimple in the top of the half-inch rod, using a hobby rotary tool, for the bottom-bearing surface. The radius of the dimple should allow the marble to rest at its bottom (Figure 3). File the half-inch knockout so that it will fit inside the PVC cap (it should almost fit already).

Place the knockout (steel disk) into the cap and glue the cap onto a 4-inch length of PVC pipe. Slightly bevel two sides of one end of the PVC coupling so that it will fit into the center ridge of the U-panel. Put the PVC pipe through the hole in the center ridge and glue the coupling to it. Cut another length of half-inch PVC pipe (about 7 inches) so it will extend from the coupling through the hole in the box cover mounted to the cross EMTs (Photo 1).

Solidly mount and level the 2-inch pipe into the ground with about 4 feet remaining above the surface. Using the hose clamps, attach the spacer disk near the bottom end of the half-inch rod. Slide the support plate followed by a hose clamp down the rod about a foot and tighten the clamp (remember this clamp supports the weight of the tetrahedron). Put the rod into the steel pipe, and level and secure it with the leveling bolts (Figure 4, Photo 3).

Place the marble or ball bearing (with a bit of grease) in the dimple and slide the tetrahedron in place. The support plate clamp may be moved up or down to provide clearance for motion. Some weight will have to be added to the front to balance it. When the PVC pipe is not dragging on the sides of the steel rod, the balance is good. (See the black pipe used to balance the tetrahedron in Photo 1.)

Photo 4 shows the tetrahedron in operation. Other materials such as plywood can be used, but keeping it light will enhance its sensitivity, and metal will last for years.

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