I’ve put the rear stab and fin on a few times in the past to check alignment and balance. But I’ve always removed it because the garage is just too crowded to leave it on. This time I’m mounting it permanently so I can soon do the final weight and balance.
The first issue was needing to rearrange the garage so everything fits. The left wing is placed against the wall then the right wing behind it. If this order is reversed the right wing tip makes it impossible to get the fuselage with stab into the garage. The wing arrangement leaves a small gap where the stabilizer can move over and line up with the door.
The other problem is making sure the strobe on the fin does not get chopped off by the garage door. To obtain the proper clearance the nose wheel needs placed on a dolly to lower the rear of the airplane. This also makes it much easier to manuver the fuselage in and out of the garage.
With the logistics resolved it was time to get started. I put some loctite and safety wired the teleflex cable bolts.
The vinyl tube and clamp safety was added to the end of the teleflex. This ensures that if the tube on the end of the teleflex was to come loose it cannot fall off and jam the cable.
With the fuselage prepared the fin was bolted to the stabilizer. This must be done before bolting the stab to the fuselage because its nearly impossible to install the rear fin bolt once the stab is attached to the fuselage. Unless you have help, this step needs done indoors. Until the braces are attached wind blowing on the fin could put too much stress on the bottom bolts and break something.
While tightening the bolts I discovered that either the bottom of the fin or the top of the stab was not perfectly flat. Not really sure how I managed to overlook this earlier but it needs addressed. I believe the issue is overlapping fabric at the front bottom of the fin. If the bolts are tightened the bottom of the fin bends a little causing the fabric to wrinkle. To resolve this I added a shim between the stab and fin at the front bolt.
The four angle brackets were bolted to the fuselage but not completely tightened. The stabilizer was bolted to the brackets and then the fuselage bolts were tightened.
Attaching the fin struts was easy except for the bolt on the fin because it has a bracket on both sides. I took a junk 3/8″ socket and ground the outside diameter to 1/2″ making it a super thin wall socket. That was the only way to tighten the lock nut, no other tool could fit into the bracket. To keep the bolt from spinning I jamed a flat blade screwdriver between the bolt head and bracket.
The wires for the strobe were attached and wrapped with self fusing silicon tape to ensure they cannot vibrate loose.
Finally the rudder and elevator were installed by inserting the hinge pins. I’ve not added the grease or cotter pin to hold them on yet since I may need to remove them when I put this on a trailer and take it to the airport.
Empennage competed, now I hope all my measurements are correct and it will actually fit through the garage door. That will need to wait for a warmer day.
The best place for the strobe is on top of the fin. Getting the wiring up through the fin will be difficult since I’ve already covered the fin. Looks like I need to make a 3 foot drill bit.
I got a 1/4 steel rod and sharpened the end to a point on the sander.
Then I used a dremel with a cut off wheel and made two groves 180° apart.
It’s a little slow but works well.
The hard part was getting the angle just right to drill right down the center of the nose ribs. To assist with this I made a small guide block, similar to the guide block used to drill the axle hole in the landing gear.
Once the hole was drilled the wires were routed through the nose of the fin. A hole was drilled in the bottom of the strobe and the strobe base mounted into the fin.
Terminal ends were added to the wire and connected to the strobe.
With the fin mounted the wires were connected and the strobe tested.
In the quest for an affordable strobe I found many suggestions. Some people have used fire alarm strobes, I considered this.
Others just say buy one so I looked into that. The Microavionics MM030 strobe is about $150 and has a xenon flash strobe powered with 20 joules and weighs about 9.5oz. Not really sure how tall or wide it is.
The cheapest pre-made strobe I found is the Skysports Bright Star Strobe avaliable from Aircraft Spruce. It has dual xenon flash tubes using 8 joules, weighs “under 5oz” and is 2.75″ wide and 4″ tall.
In my opinion the Skysports strobe is not bright enough. Sure it meets the need for twilight flying but 99% of my flying will be on sunny days. The main reason I want a strobe is to make my slow small airplane more visible to other faster approaching aircraft, this is especially important when taking off and landing.
I also wanted to avoid a xenon flash tube, the high voltage can cause radio interference. Sure properly grounded it should not be an issue but this is a wood airplane.
After looking I found a nice LED light that fits the bill. It weighs 7oz so it’s lighter than the MM030 but heavier than the Skysports. At 5.5″ tall and 2.75″ wide it has the same footprint as the Skysports just 1.5″ taller. Most importantly it is very bright. It also ended up being the cheapest at $40.49 with free shipping.
Unexpectedly this LED light did cause RF interference with the radio. Each time it flashed you could hear a hiss on the radio. Adding a ferrite core to the power wires resolved this problem. The core was salvaged from an old VGA cable and fits nicely inside the bottom of the light.
I’ll cover mounting it in a future post.
Long ago I ordered some operating range decals from aircraftspruce.com so I can mark the air speed indicator. While the decals worked ok they are a little short. The more expensive decals they sell are full circles so no worries about being too short.
I labeled the stall speed with and without flaps, maximum speed with flaps extend, normal operating range, cautionary range and maximum speed. For three dollar decals they look very professional but you might need two of them to get the job done.
The air speed indicator requires some tubing that goes to the pitot tube and static ports. Previously I wrote about the static port installation, you can read about that here. This article covers the tubing for the pitot tube. I decided to use the removable pitot tube kit, sold by Leading Edge Airfoils, so I can remove the pitot tube when removing the wings.
I thought that putting it out the leading edge of the wing would look nice, trouble is I already built the wings so installing is not going to be a simple task. I created two wood blocks, one to fit inside the wing just below the leading edge stringer and another to fit in the outside of the wing to support the pitot tube mount.
The inside block was threaded to match the pitot tube mount. I added CA glue to the wood as I tapped the threads to ensure the threads remain strong.
The only access hole in the leading edge is where the strut mounts are located so that’s where I decided to mount it. I cut a hole in the leading edge ply and epoxied the threaded block in place.
All of that was done about a year ago, now that the wing is covered in fabric and painted, time to finish. I first run the vinyl tube inside the leading edge from the root to the access hole. There I slid the tube through a 3/4″ deep well socket, then the plastic nut and out the threaded hole.
The outside wood spacer block was slid over the pitot tube mount and then the vinyl tube was slid over the barbs on the mount.
The mount was threaded into the wing, I had to ensure that the vinyl tube inside the leading edge was rotating too instead of rolling up into a knot. Now for the hard part, I used some long forceps to get the plastic nut started on the pitot mount. To tighten the nut I dig around my junk drawer and found the perfect tool, an old useless screwdriver. After a trip to the disc sander and vice it now looks like this.
My newly designed wrench fits into the hole on the side of the socket allowing me to turn the socket about 1/4 turn at a time.
I used my $20 USB endoscope camera hooked up to my phone so I could see if the nut was indeed fully tight.
I retrieved the socket using a magnetic pickup tool.
Next I made a plate to hold the quick disconnect.
Here I forgot to take a picture. Before I drilled that 5/8″ hole in the plate above, I had only drilled a small 1/16″ hole at the center. While chewing some gum I installed the wing so I could mark the center of the quick disconnect on the fuselage.
Grabbed the hole saw and drilled a hole in the fuselage side.
The vinyl tubing was cut to length, disconnect plate varnished and disconnect installed.
The 90° disconnect inside the fuselage was attached to the vinyl tubing that runs up to the AIS.
I’m using the same valved disconnects I used for the fuel lines. So I don’t have to worry about bugs crawling inside my tubing and clogging it while I have the wings removed.
The final result looks great, hope it works well too!
Various parts of the airplane need to be locked for safety or plugged to keep bugs/debris out when the airplane is parked and not in use. These locks and plugs are usually attached to a flag stating “Remove Before Flight.” I purchased some inexpensive, well made, keychains for my flags.
The BRS ( aka ballistic parachute ) came with it’s own flag. This is for safety because you do not want to accidently activate it. It does not have ballistic in it’s name for show, that rocket needs treated like a loaded gun.
The static ports are used to measure atmospheric air pressure and are integral to the air speed indicator (AIS) and altimeter. I bent a small piece of music wire that attaches to the keychain and doors snuggly into the static port.
Maybe not necessary but seemed like a good idea I got a small rubber stopper and eye bolt to make a plug for the exhaust.
The pitot tube, for the AIS, was a little more difficult to block because the tube can be removed. We not to plug the hole the tube goes in or the end of the tube when it’s installed.
Drilled a hole in the side of a 1/4″ aluminum rod to attach the form.
The rod can easily plug the pitot holder.
Added a piece of 1/4″ ID tubing, this will be used to plug the tube when it is installed on the airplane.
With the pitot tube removed the hole is easily plugged and looks nice.
When the pitot tube is installed the same flag can plug the hole. The only downside is that it does add a couple inches to the length.
The droop wing tips I got from TEAM had some flaws. A few voids here and there were no big deal but not fitting the leading edge was a problem.
To fix the front I ground out the seam on the wing tip. Some wax paper was taped onto the leading edge of the wing. Polyester resin was mixed up and new fiberglass added to the wing tip. Another piece of wax paper was placed on top of the wet fiberglass and rubber bands were used to hold everything in pace while the resin dried.
The edge of the wing tips are not straight so I decided to mount them, drill the holes and then trim the edge based on the path of the screw holes.
I marked a line on the wing 2″ from the end around the perimeter, this will be used as a reference to drill the screw holes into the fiberglass tip. The tip was mounted and clamped in place then measured 1.5″ from the line and drilled holes into the wing tip every two inches. This places the center of the screws 1/2″ from the edge.
I would drill a few holes, remove the tip and enlarge the hole in the fiberglass and then bolt it back into the wing and drill a few more holes. Once all the screws were in place I used them as a reference to mark a straight trim line around the tip then cut off all the excess material.
A 1/8″ plywood piece was cut and fit to seal the end of the tip at the aileron.
It is held in place with some fiberglass cloth and resin from the inside of the tip.
The tip did not match up to the aileron as you can see here. Not really necessary but I wanted a better look.
Using a thin diamond cutting blade on the Dremel I cut a slot at the back of the tip.
Then I used some polyester resin to glue in a piece of 1/64″ plywood that I pulled from my R/C airplane parts bin. This was a little tricky to get right because it can easily flare in or out if your not paying attention.
Once that dried I mounted the tip onto the wing and marked where I wanted the tip to end.
The plywood was cut along the mark, then polyester resin and fiberglass cloth was used to build up the tip to the proper thickness.
After applying some filler and sanding the extended wing tip looks great.
Filler was applied to all the other imperfections, the entire surface sanded and primer was applied.
A couple base coats of white were applied and finally the red top coat. Installed they look great!
One last modification was needed to the tips so I can easily remove the aileron with having to remove the tip. I modified the SHCS that hold the bearings on the ends of the aileron so I can install a safety pin so I know the aileron cannot fall off.
To make it easy to pull the pin I drilled a 7/8″ hole in the bottom of the tip directly under the aileron bearing and plugged it with a solid rubber grommet.
Installing the pin is not terribly difficult through the.
To cushion the bottom of the tank I got some 1/8″ thick neoprene. The best deal I found was sold as “tool box drawer liner.” I cut it so it is wider than the bottom so it wrapped up the sides a little then notched out the inboard rear edge to match the plywood.
The tank needed two holes, one for the drain and one for the fuel level sensor. I first drilled a small pilot hole then used a 1/2″ forsner bit. Never use a regular twist drill bit for this step, you will end up with a triangular shaped hole instead of perfectly round and the bushing won’t seal.
Then installed the rubber bushing.
At this point I realized this particular tank is too deformed to install the fuel level sensor because the top and bottom are curved inward so there is not enough clearance for the sensor.
Knowing these tanks do expand the first time they are filled with gasoline I had to stop the installation and fill this tank with gas and hope that resolves the problem. After a few days the tank was still deformed, so I sealed the tank and put a few psi of air pressure in it. The following day I removed the air pressure and let it sit with gasoline in it. After a few more days the tank is back to its normal shape and has held that shape for over a week.
Now I can install the fuel level sensor. I made sure that the sensor was about 1/4″ above the bottom of the tank and pressed it into the bushing.
I was concerned that the polycarbonate cover might bump the calibration switch on the sender so I cut a ring of plywood to protect the switch. I used some silicone to hold the ring in place.
The drain hole in the bottom of the tank was drilled and fittings installed.
Now the tank was installed into the wing. To hold it in place I purchased some tie down straps. They were way too long so I cut them shorter and heat welded the end so it does not fray. I routed then under the plywood and diagonal supports then over the top of the tanks.
The fuel line was routed from the elbow to a tee. Then to the drain and quick disconnect. This was not an easy task to accomplish without kinking the lines. It would have been easier if the quick disconnect was moved an inch or two forward but that would have made the quick disconnect higher which is undesired and more likely to get bumped by my elbows when sitting in the cockpit. Maybe cutting one barb off of the tee would help too.
After installing the cover panel I’m amazed at how well it looks.
Not much remains on the wings now. Grease aileron bearings, safety wire aileron bracket bolts, install wing tips and I need to get the rest of the wing polished so it shines like the tank cover and ailerons.
Time to route the fuel level sensor wires. The first thing I did was mount the wings and locate a location to drill a hole for the wires. After drilling the hole I added a grommet.
After locating the hole I determined how much wire needs to protrude from the fuselage so they can be easily disconnected after removing the wing.
The sensor outputs need routed to the fuel selector switch so I decided to make some splices near the sender switch to accommodate this. I routed the left fuel sensor wire down the left fuselage side, across the floor and up the right side and through the grommet. On the right side near the fuel selector switch I spliced in the fuel selector and right side sender wires.
The red and black (power and ground) are spliced to the right side sender so both senders get power. The white wires from each sender are spliced to the wire going to the selector switch, right to red and left to black. The white wire from the dash and to the selector were spliced.
Terminal ends were added, the resulting harness looks pretty good.
Behind the dash the black is connected to ground, red to power and white to the green EIS Aux input.
Two fuel lines pass through the firewall. One is from the electric fuel pump, the other is gravity feed. In the picture below the right line comes from the electric fuel pump. The inline check valve ensures fuel can only flow towards the engine.
After the check valve is a tee, shown below. Left side connects to the electric fuel pump check valve, right to mechanical pump check valve and the top goes to the carburetor. Behind the tee is the inlet for the mechanical pump. It’s fuel line is connected to the left line in the picture above. Rest assured, the top hose now has a clamp, it was not installed when I took this picture.
Below you can see the mechanical fuel pump on the right. The outlet connects to a check valve that’s connected to the tee. I wrapped some silicone tape around the check valve so won’t chafe nearby components.
The outlet of the tee connects to the fuel inlet banjo on the Dellorto PHBE34BD3 carburetor.
This is one complaint I have about the Hirth F-33, it came with the fuel pump and carburetor. The outlet on the fuel pump is made for 1/4″ (6.3mm) ID hose but the inlet on the carburetor is only 6mm. To resolve this I ordered a new fuel inlet banjo, Dellorto part number 6273 that has a larger diameter barb.
Now all I need to do is fasten the fuel tanks in the wings and install the air filter and she is ready to run!