Month: November 2017

Strobe

Posted on Updated on

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.

LED strobe
LED strobe

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.

Advertisements

Curtis Drain Valve Hose

Posted on Updated on

To drain the fuel from the airplane I installed some Curtis quick drain valves CCA-4850 and purchased the Curtis drain hose assembly CCB-39600-5. They claim that “Waste liquid flows through 5 feet of high grade vinyl tubing, preventing messy spills and making a cleaner, safer environment.” A better description would have been “95% of the fluid flows through the hose, the rest makes a messy spill”

At first I thought maybe the particular valve I got was the problem but looking on their site I see that my valve is listed with the hose I have. Upon further inspection of the valve I see the problem. There is no seal between the valve and the valve body when the valve is opened. So some of the fuel leaks between the valve and it’s body while the majority of it runs through the valve into the hose.

Curtis drain valve not sealed between valve and body
Curtis drain valve not sealed between valve and body

I removed the brass piece from the drain hose assembly and decided to make a simple modification. The brass is shaped like a little cup and can catch the fuel that leaks between valve and valve body. So all I needed to do was drill a small hole to allow the captured fuel to drain into the hose instead of overflowing and making a mess. I used a 0.09″ drill bit inside the nipple at a slight angle.

Side view demonstrating the angle of the hole
Side view demonstrating the angle of the hole

Drill bit angled to drill the hole
Drill bit angled to drill the hole
Modified Curtis drain hose, small hole in the
Modified Curtis drain hose, small hole in the “cup”
Modified Curtis drain hose, small hole in the
Modified Curtis drain hose, small hole in the “cup”

After trying out my modified drain hose I discovered that it does work much better but not perfect so I added a second drain hole on the opposite side. At this point I’m satisfied. Some fuel vapors will come out around the connection and sometimes a little will condense on the valve tabs. But fuel was not pouring down the outside of the hose and making a puddle on the floor like it did before the modification.

If it’s not obvious, it has one drawback, if the drain hose is obstructed in any way the fluid will follow out the holes, overflow the cup and make a big mess. Maybe a valve and a nipple to drain the fuel would have been a better choice.

CCB-39600-5 Curtis Drain Hose locked into drain valve
CCB-39600-5 Curtis Drain Hose locked into drain valve

AIS Markings

Posted on Updated on

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 needed more green than what is provided
I needed more green than what is provided

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.

AIS tubing

Posted on Updated on

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.

Pitot tube mount and blocks
Pitot tube mount and blocks

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.

Pitot tube mount and blocks
Pitot tube mount and blocks

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.

Pitot tube hole in leading edge
Pitot tube hole in leading edge

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.

Pitot tube mount nut
Pitot tube mount nut
3/4 socket to tighten pitot mount nut
3/4 socket to tighten pitot mount nut
Vinyl hose for pitot tube
Vinyl hose for pitot tube

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.

Pitot mount and external spacer
Pitot mount and external spacer

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.

Custom wrench
Custom wrench

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.

Turning socket with wrench
Turning socket with wrench

I used my $20 USB endoscope camera hooked up to my phone so I could see if the nut was indeed fully tight.

Pitot mount nut tightened
Pitot mount nut tightened

I retrieved the socket using a magnetic pickup tool.

Retrieved socket with magnet
Retrieved socket with magnet

Next I made a plate to hold the quick disconnect.

Quick disconnect mounting plate
Quick disconnect mounting plate

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.

Tasty center finder
Tasty center finder

Grabbed the hole saw and drilled a hole in the fuselage side. 

Hole in fuselage for pitot disconnect
Hole in fuselage for pitot disconnect

The vinyl tubing was cut to length, disconnect plate varnished and disconnect installed.

Pitot quick disconnect on wing
Pitot quick disconnect on wing

The 90° disconnect inside the fuselage was attached to the vinyl tubing that runs up to the AIS.

Pitot quick disconnect inside fuselage
Pitot quick disconnect inside fuselage

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!