Carwil Type 61

This post will illustrate the differences between the Carwil Type 61 bubble face compass and the more common Airpath bubble face compass. This information is from my 1940 issue of the Airplane Parts and Supplies Catalog No. 101. It appears that the Carwil came first and the Airpath was a later improved model. Here are some pictures from the catalog.

  
Here is the description from the catalog that explains the different models.

I will show some of the differences between the Carwil model and the Airpath. Many of the parts are the same with the biggest difference being the front face appearance. I think this is a 60C even though the name plate says Type 61.

  

Here you can see the unusual compensator , it uses thin rod magnets inserted into drilled holes in a clear plastic block. It uses tiny brass doors to keep the rods in place. If anyone has any instructions for this procedure I would love to see a copy. Here is another shot with the unit removed.

You can see the little doors and the rod magnets.  Now here are a few shots of the later Airpath Compass you can see the difference in the front face.

The top of the back case also has a flat area that the early model does not.

The compensator from the later Airpath is much improved. It allows a much finer adjustment of the magnetic fields.

This side is for E-W adjustment and the other side compensates the N-S direction.

You can see that the later model is much longer and thicker than the original model. I have seen these ground down in a lame attempt to fit the early case. It does not work well.   The front plate is held to the compensator assembly by two small drive screws, then held to the compass by one small screw. I have sen these read Carwil, Airpath, and Taylorcraft.

When I did a Google search for Carwil Type 61 nothing came up maybe this will fix that! If I have time this week I will post some pictures of my antique compasses !

Va EAA Flyin

Today I flew the Cub down to Suffolk, VA for the VA EAA flyin. With a stationary front laying along the VA-NC border the weather forecast was for rain showers in the afternoon so the turnout was light and mostly local. I had a beautiful smooth flight down with a high overcast keeping the temperature a little on the cool side. Here are a few pictures from the day.

I was parked between a Pietenpol and a 1965 7ECA Citabria, down the line is a British Bulldog , a Lancair, and a C-195. you can see the cloudy skies. There was a cold North East wind also. Here's the little Citabria , I've always liked these, this one was a little rough.

The highlight of the day was getting to sit in one of the "new" built ME-262's at the fighter factory hangar. My friend Scott knows the Chief pilot there. I forgot to get a picture of me in it. It is just like the original F-18, "one man, one hour, one bomb" . With only 400 gal fuel and 2 CJ-610 engines, and no RVSM you would be out of fuel in about an hour! Here's Mike and Scott.

I spotted this in the Ultralight area, just where you want to see pipe wrench marks, on the Jesus nut that holds the prop !! For goodness sake buy the right wrench !!

I spotted this in the RV area. I'm not sure if he wanted this effect or if he F'ed up??  Not sure you can really see it in the pictures but the skin was sunken in between the ribs, like a fabric airplane.

How did he do this ? It looks like a plywood covered wing after 20 years. You can see the effect in the reflection in this shot.

There was also this nice Pietenpol over in the camping section.

I left right after the Parade of Flight at 1:30 but I stayed too long and got caught in some rain about 15 south of Williamsburg. I turned this into an opportunity to clean up the Cub so she got a sponge bath and towel dry in the hangar. Since the airport is on wet lands the EPA says we can't wash airplanes.
That's about it  for VA EAA,  nice flight down, great pancake breakfast with good friends, low turn out but some nice aeroplanes. They were actually lucky , it could have been a complete wash out.

Antenna Completed

I finished the wiring of the antenna last week and have been doing some testing. Unfortunately the spring winds have arrived and I have not done much flying. It has been an odd spring, either 70-80 degrees with a strong SW wind or 50 degrees with a strong N wind. Here is a shot of the wiring installed and the cover plate installed.

 The initial test flight was a disappointment, by moving the antenna forward I now had some ignition noise causing the radio to break squelch. The Icom A6 has a very sensitive receiver , it picks up everything wanted or not.  However after some tweaking I think this installation will be OK. First the ANL (automatic noise limiter) got turned off, with it on the ignition noise is barely noticeable. Then by increasing the squelch setting to 15 from 10 (the range is 0-24) the radio worked much better. With the lower sensitivity of the internal antenna I needed the lower squelch setting.
While not perfect this is an acceptable solution. I can now receive the ATIS at Richmond 33nm away at 1500 feet, most importantly when the airplane is pointed that way! Of course there are trade offs. There are a couple narrow blank spots where the landing gear blocks the antenna and directly aft off the tip of the rod.  I would say about 4:30, 6:00 and 7:30 positions are a little weak with fantastic airborne performance from 7:30 around to 4:30 in front of the airplane. Here is a shot of the final install.

  
I fixed one last little item that had been bothering me last week with the oil change. These inter- cylinder baffles kept blowing out of position.

I bought these from WagAero and just assumed they were correct. It seems that the mounting hole is too far outboard and the moment created by the air load allowed these to move out of position. I removed these and relocated the mounting hole 3/4 inch inboard. So far they seem to be staying in position.

With 85 hrs on the engine the oil change was due, compressions were all mid 70's, screen and magnetic drain plug were clean and everything looks clean and tight. Ready for a summer of evening patrols.

Antenna Issues

I have been working to optimize the communication antenna installation on the Cub. My home airport has significant transient traffic, so a good radio is a must for safe operation. I started with just the short antenna that came with the radio, however that had limited range and a tendency to feed back through the microphone wiring.  I had purchased a dipole antenna for my Taylorcraft and could never get it to work properly. It was installed in the tail behind the cockpit. I still had it so I thought I would give it a try in the Cub. Here is a link to the antenna web site.

 http://www.advancedaircraft.com/

To make a long story short, I have tried this antenna vertical, angled right , angled left, angled forward and back, side ways, and curved in every direction . In every case the reception to the sides is great but the signal is blanked directly to the front. The only place it will fit due to it's length is behind the seat in the fuselage.

The combination of tubing , pilot, passenger, engine, fuel tank, and firewall, must shield the antenna from any forward signal. You can turn 15 degrees left or right and receive a usable signal.
My test procedure is to takeoff from KJGG and climb to 1500 feet and tune the ASOS at KAKQ 20 nm away. I then execute a slow 360 degree turn while monitoring the signal. In every case the signal is blanked to the front where you need it the most. On my Taylorcraft I gave up on this antenna and installed a bent whip on the bottom of the boot cowling.
On the Cub this would be more difficult because there is no access to the inside of the boot cowling to install a proper doubler and to attach connectors. It took some brainstorming but I finally figured out a method. I decided to attach the antenna directly to the bottom of the forward floor boards, all the loads would be absorbed here. The physical antenna would protrude through a small hole in the lower boot cowl. Here is the attach bracket I came up with, it's formed from 0.040  2024-T3 aluminum.

Using a 2 inch hole saw I cut a hole in the forward floor boards.

Here is a shot of the completed mounting bracket with nut plates installed and a coat of alodine.

 
With the help of my friend Scott , we figured out a process to install the antenna , add the insulator, install the bracket, and tighten it all up. It was a slow careful process because anything you drop is a frustrating exercise in fishing to recover. If it's not magnetic you have just lost and hour.  Here are some shots installed. Once the wiring and testing are completed I will make an aluminum cover plate and remove the AN970 washers, painted black you will hardly notice it.

The safety wire is the path the antenna wire will follow under the floor boards. Here are some shots outside.

I'm not sure how this will work with the landing gear so close and the limited area for ground plane provided by the narrow boot cowl. It was an improvement on my Taylorcraft so I'm hoping for the same here. I would settle for being able to transmit and receive in the direction I am traveling. I hope to wire and test this on Friday, tomorrow is my father's 91st birthday!   

Tailwheel issues

When I got the  Cub project the tailwheel was missing, so I rebuilt an old 1 1/4 inch Maule SFSA unit I had in stock. It was in pretty good shape but had a little wear on the main bushing, however I did not have the tooling to replace it. Lately I had been experiencing an occasional tailwheel shimmy on landing. Nothing you could not stop with a little forward pressure on the stick but annoying just the same. I thought this was due to the wear in the tailwheel so I ordered a new bushing from Aircraft Spruce and made the tools to do the job correctly. First I had to make a tool to remove the old bushing, my friends at Mid Atlantic Aviation let me use their lathe and I made this tool from some 4130 scrap.

The small end is 0.005 less than the ID of the bushing and the large end is 0.005 less than the ID of the pivot forging. Here is a shot of the new bushing.

Here is the old bushing still installed.

First you have to remove the two screws that hold the unlocking cam and the grease fitting. These extend into the bushing.

Then using the tool in a hydraulic press you can remove the worn bushing.

After cleaning up the forging , I used the tool in the press to install the new bushing.

After installing the bushing I carefully drilled through the threaded holes in the forging and through the new bushing. I then tapped the threads into the bushing. Since installing the bushing slightly reduces it's inside diameter, I reamed the ID to 0.875.

I cleaned and inspected all the other parts and reassembled the tailwheel. The old tire I had been using was worn funny so I installed a new tire.

Here is the completed tailwheel installed on the airplane, notice anything odd?

Notice the pivot axis of the tailwheel. It is actually tilted a little forward when it should be vertical or slightly aft ! This was a real boner on my part because I had installed a 1/8 inch rubber pad between the tailwheel spring and the airplane tail post , this changed the geometry of the spring and changed the pivot axis.

 I removed the pad and no more shimmy. While the tailwheel rebuild was very educational, the wear was probably not the cause of the problem after all. Here it is with the pad removed. I have decided to reinstall the pad and add a couple washers at the front attach bolt to maintain the correct angle. I think the pad does cushion the airframe a little from the tailwheel loads. Here it is all cleaned up , ready for a summer of flying.