Friday, March 29, 2013

Versatility & Cox SkyCruiser

I had been looking at the Cox SkyCruiser sitting on the shelf in my favorite hobby shop Everything Hobby for sometime thinking I could use this plane for slope soaring from small slopes. The plane is a glider with an electric motor on a pod above the wing. Everything is included ready-to-fly for under $100. 

This looks like it might be a good plane to learn to fly radio control with, and it might be except that it will fly fast if you advance the throttle. Any of the crashes I had were at reduced power over fairly soft ground and there was no damage. No doubt crashing fullspeed into pavement would break something, at least the motor is way back from the nose and should not get damaged.

Snow was sticking to the nose on this day.

After the first few flights I could tell that although there was adequate control for turning with the power on, in the glide there was not near enough. My solution to that was to extend the rudder surface with balsa, this helps the turns in the glide, which is really needed for slope soaring. It was getting to be late fall so I only had a couple of chances to try slope soaring from small slopes but it did alright and there was the motor backup if you got in trouble. This should give me the ability to risk flying over slopes that I would not be able to recover the plane from if the lift quickly died.

Preparing to do Touch and Go from Snow

After the first snowfall I got the idea that maybe I could take this plane off the snow because the propeller was way above ground level. It looked like this would work but the radio equipment was moving off center with the cold temperature, it was around 25 degrees F. As one who does not give up easy I tried it again from early spring snow with temperatures in the mid 30's range. It worked great, I had fun taking off and then doing touch and goes. On the next day the snow was sticking more to the plane but I found if I started in a groove made from a ski I could still take off. So now I had a model plane for soaring and for warmer days of flying off the snow.  The next thing is I want to try to thermal soar with the SkyCruiser.

Slimming Across the Snow

Bill Kuhl

Thursday, March 28, 2013

Why I Still Fly Wind-up Airplanes

Background in Model Aviation

Model aviation has been a large part of my life and a source of much enjoyment and some frustration, I have flown many type of model airplanes from the large and very complicated to the very simple. Radio control airplanes of many types including a large plane I designed with a chainsaw engine, pylon racing, and sailplane competition have been part of my model airplane hobby. I continue to enjoy some types of radio control flying but also enjoy equally free flight model planes powered by loops of rubber.

Plane I Designed With Chainsaw Engine

Some of the Appeal of Rubber Free Flight Airplanes

There is such a challenge in getting a model plane with such a small power source and no control to fly consistently for the a long period of time. So many factors play into it such as the specifications of the propeller, rubber motor, design of the plane, covering material, and how it is adjusted to fly.

Having a large number of rubber powered model planes is affordable and practical. Planes can be built in a short amount of time or you can build planes of  incredible detail that take months to build. It is so fun to try different ideas for aircraft; canards, biplanes, or planes that look like a flying circle.

Short Video of Canard Flying 

Rubber powered free flight planes is the best way to introduce kids to model building and flying in a group setting that is affordable. Building any other type of model plane with the exception of small free flight gliders always gets expensive for large groups. Still the kids can learn about the basic aerodynamic principles as well.

It is just so darn cool to see a model plane flying perfectly stable climbing ever higher into the sky. There is also the possibility of flying rubber powered planes indoors in a large room. As your skill increases an indoor model plane can be constructed that flies for minutes indoors.

Bill Kuhl

Highly Recommended Article of Starting in Free Flight

Tuesday, March 26, 2013

DHC-2 Beaver RC Conversion

One of my current projects is to build the DHC-2 Beaver Guillow's kit for electric radio control using the motor and electronics from a Park Zone Champ.  Both planes appear to be about the same size and the Guillow's kit appears to be built extra strong so I think it should work well. I didn't start out thinking I would build it for RC but it just seemed to me there was so much wood in this kit that it would be on the heavy side for a rubber powered free flight model.

If I would have started from the beginning planning to create a radio control plane it might have been a little easier. I ended up cutting into the constructed tail surfaces to build in the movable rudder and elevator. For hinges I decided to use thread like used on the really old radio control airplanes. For the landing gear I am using the gear from the Champ instead the parts for the rubber model thinking it should be able to handle the extra weight on landing.

It will be interesting to see how this this flies, if it works good I have a Cessna 150 kit that I might convert also. Hopefully I will have learned a few things about this type of project also before I attempt another one.  DHC-2 Beaver Kit Link

I am making slow progress but have made some as seen in picture below. The plane appears to be tail heavy even with the radio pushed as far forward as possible. I lightened the tail some and put weight inside the front of the plastic cowl.

Completed DHC-2 Beaver Flies!   My Blog Post on Completing this project.

Bill Kuhl

Monday, March 25, 2013

Trying a New Idea on Rubber Model Nose Plug

On rubber powered free flight models with a full width fuselage it is so often a problem that at the end of the flight when the tension of the rubber motor is gone that the removable nose plug will fall out and be dangling by the rubber motor.  Hopefully the propeller assembly and nose plug will not not detach from the rubber motor and be lost. Normally it just disturbs the glide by causing more drag but it does not look very good either.

Propeller and Nose Plug Dangling on Guillow's Super Cub

There have been many methods tried to keep the nose plug in place during flight but I did not want anything sticking out of the plane which is the case with some types of latches. I have tried the tiny but powerful neodymium magnets and just wanted to try for a cheaper solution. What I came up with was  using some squeezeable foam on the nose plug assembly that puts some pressure against the inside of the fuselage in the nose area of the fuselage and causes a fair amount of friction.

Foam Visible Before Gluing Bottom On 

My concerns with my idea is that the foam might become detacched from the balsa that it is glued to. It will be fun to see how this holds up over time. By the way the plane I am trying this on is a Guillow's Lancer.

Nose Plug Before Gluing Foam

Bill Kuhl

Rubber Powered Helicopter Cheap Fun

I am always on the lookout for cheap toys that might give me project ideas. In a Hobby Lobby craft store I spotted this rubber powered helicopter for only $2.49 that had a foam body, actually a flat profile of the body of the helicopter. Previously I had a similiar helicopter that was made with a wood body profile that seemed too heavy to fly very high. The foam should be lighter and I know on anything that flies weight makes a big difference.

Assembly of the helicopter only takes a few minutes, everything slips together and a clear rubberband holds the foam body profile to the wood stick. The rubber strip that is provided is thin and long so it has to be folded into three loops. Propeller blades go into plastic sockets and twist into a locking arrangement so the angle is set.

To fly the helicopter just wind the propeller up about 75 turns, make sure it is pointed completely vertical and release. It should gain altitude to at least 40 feet and start to descend. The body of the helicopter still rotates slowly because of the torque reaction of the propeller. Shortly after the descent the rubber is unwound and then the helicopter starts fluttering towards the ground in more of a horizontal position. In the dozen flights I tried there was no damage even landing on hard surfaces.

It would be fun to try to build this as a group project, the challenge would be to build an effiencent propeller.  If you can not find this locally this is the website link. Guillow's Copter Toys

Bill Kuhl

Friday, March 22, 2013

Dinkar Narwade - Part III Learning About Rural India

Before I started emailing Dinkar I had such a different idea what life in India was like. My impressions were of large cities with crowded streets and call centers to support companies in the United States. How different I would find life in the rural areas yet the views and interests that Dinkar and I shared were very similiar in many ways.  I so looked forward to the pictures he would send and had many questions, he probably thought my questions were silly. One example I noticed in some pictures the students were wearing uniforms and in other pictures they were not. Apparently they have only one uniform and Thursday it is washed.

Foam Plates & Gliders on Thursday

Students Made me Cards Wearing Uniforms

Excerpts from emails sent by Dinkar:

"Here are some metropolitan cities that contain everything you need. But I am talking about India, that scattered in large rural area. Rural India has totally different face than urban one, and I am working in rural part of India..Hey my school hasn’t a single computer to introduce the world of internet.!! Sometime it makes me feel bad about my student’s future. Now I using a cellphone to send you pc is at my workplace, the nearest town from my school."

"Hi Bill,those are great pictures.I can only saw USA in pictures and movies.I think its nearly impossible for me to visit your country in my entire life!...Hey Bill I am a fan of Hollywood movies.Steven Spielberg is my favorite director.I almost watched his Indiana Jones are some my favorite movies-Titanic,Brave-heart,Troy,Gone
with the wind,Godfather,Enemy at the gates,Brokeback
mountain,Avatar,pirates...Johny depp......etc."

Bill Kuhl

Dinkar Narwade - Part II ScienceGuy Projects

Happy Students with Package I Had Sent
Pictured above are Dinkar and his students with the sample package I had sent, it sure made me feel good to see how thrilled these kids were to receive these items. Besides my project ideas I had also sent a couple of the PITSCO model solar kits were really a hit with everyone.

The contents of the package I had sent included foam gliders, mousetrap car kits, and model solar car kits.  Pictured below is a student with a Thank you sign and another holding completed solar car that really made my day.

Bill Kuhl

Dinkar Narwade - India - Part I the Canada Connection

The story of my connection to Dinkar Narwade a teacher in rural India begins far to the North in Ottawa Canada and a simple rubber powered model airplane know as the Squirrel. Darcy Whyte and I have been emailing for several years do to our mutual interest in model airplanes and more specifically introducing model planes to other people. On my website I have a whole article dedicated to Darcy Whyte and the Squirrel Model airplane. Darcy Whyte & Squirrel Article

Video interview of Darcy Whyte

Darcy had made connections with Dinkar and had sent some Squirrel kits to the school. Thinking that Dinkar might also be interested in the project on my website, he had sent Dinkar my email address. After receiving an email from Dinkar I sent him a sampling of some of the projects on my website. In rural India it is difficult to get materials that would be common anywhere in the United States.

Dinkar & students with Squirrel Model Plane

Story Continues

Bill Kuhl

Thursday, March 21, 2013

How This Picture Was Created

Most people find this picture rather impressive and you might have guessed it was done with some Photoshop trickery. The ground scene was taken from the first radio control model airplane I had for aerial photography. This plane was designed and built by my friend Floyd Richards but he would later sell it to me.  It carried aloft a disposable film camera.

The model plane in the picture which is an AMA Cub I had taken a picture of on a plain background and then erased the background around the edges. The two boys were taken from another image and pasted into the picture. Bring the layers together and this was the result.
Another Picture Taken from Camera Plane

Camera Plane With Camera Removed

Bill Kuhl


Ideas That Did Not Work – First Timer Water Rocket

Most likely if you have ever experimented with getting a parachute to deploy with a water rocket you have discovered the challenge in getting completely reliable operation. Compounding to the problem is that when the parachute fails to deploy properly the rocket is so smashed up when it hits the ground that any mechanism is broke so that you cannot see what state it was in before it should have deployed.
Parachute Deployed Perfect This Time

The first water rockets I built with parachutes I just set the nose loose on the rocket hoping it would stay on until the top of the launch. This did work some of the time maybe half the time but failing even once can break the rocket.  I tried to design some type of shock absorbing nose tip that would hopefully save the rocket from destruction when it hit full speed with no parachute. One of the first rockets of this type I used part of a foam small football on the end of the nose.  There would be some launches the parachute would come out too soon and it would never get very high.

I had read somewhere about people using the wind up mechanism that comes in some toys that walk commonly referred to as the “Tomy Timer”.  This mechanism can also be used in free flight model airplanes and that is where I found a source for some of the wind-up mechanisms. My first rocket to utilize appeared to work fine on the ground but launch testing it is a whole different situation.  First launch worked perfect and luckily I took pictures because the rocket would be destroyed soon afterwards.
Pin was pulled out by string attached to plastic arm

My idea on the first rocket was to have the timer mechanism hold down one side of a compression spring. When the timer mechanism was released to turn it would pull out a small pin that would let the compression spring push a rod that would push off the nose of the rocket letting the parachute deploy. After breaking the first rocket I would even try a second rocket like this with the same results.
Rod seen on side of nose pushed nose off

My theory to what was happening is that the rod did push the nose off the rest of the rocket but the air pushing against the nose was pushing the nose back down again before the parachute could deploy. These were rockets based on 2-liter bottles and like the saying goes, “the bigger they are, the harder they fall”.
Next idea of pushing the nose off picture C is broken timer after crash

All though frustrating, I find that failure can be a good teacher and forces one to think of the challenge before you in greater detail.
Bill Kuhl

Estimating Exercise for Model Airplanes

I had come up with this lesson for estimating the cost to build a bunch of model airplanes, there never seemed to be much interest in it. Then I lost use of the server that it was hosted on, recently I ran across a pdf version. To me it seemed like a good practical exercise in mathematics.

The Exercise

Compute the Total Cost for balsa for 80 airplanes given the bill of materials for one airplane and the price list below. Break down your calculations for the two sources (mail order and hobby shop) and the two balsa types; sheet and stick. Allow for 10% waste on sheet wood and purchase one balsa stripper. Wing hold downs are made from the allowance for waste of the motor sticks (sheet wood only). For sticks allow two extra sticks for each type except 1/8" x 1/8" (wing hold down) only allow one stick extra.
To make the $20 minimum for mail order, add CA glue at $3.00 and CA Accelerator at $3.15, if order is still under $20, add second CA glue.
Calculate the number of packages of propellers needed for 80 planes, 35 propellers in a package. Make sure there are extra propellers but less than 35 extra. Add up all costs.Calculate how many feet of 3/32" rubber strip is in a one pound box. Make sure there is enough for 3 motors for each student (80 students), each motor 2 feet long.

Give your observations on the completed calculations, give advantages / disadvantages for the different options for purchase of balsa.
Bill of Materials Required for One Airplane

2 – 1/16" x 1/8" x 36" balsa strip

1 – 3/8" x 1/8" x 12" balsa motor stick

1 – 1/8" x 1/8" x 4" balsa wing hold down

1 – 6" plastic propeller assembly

3 – 24" lengths of 3/32" FAI Super Sport rubber

Price Lists

Balsa Price List

Balsa in 3" Sheets

Pre-cut Sticks

Additional Items Needed When Using Mail Order

Balsa Stripper $7.00

Shipping $8.00
Minimum Order $ 20.00

Note: If you use only sticks, the balsa stripper is not needed. This will save time as well.
** Purchasing From Hobby Shop, Assume Sales Tax
For this exercise assume 6% sales tax, this will vary between states, some states have none.

Propeller Price

Each plane needs a plastic propeller assembly that must be ordered in packages of 35. $10.56 per 35 plus $6.50 shipping. Shipping Note: there is only one shipping charge, so ordering more propellers the shipping is a smaller portion of the total cost.

Rubber Price

Each plane uses a loop of rubber that is a 24" loop of rubber strip including extra for the knot.

Each student needs three of these motors because of breakage. Compute how many motors would come out of one pound box of rubber. Use .0596 gram per inch as the weight for 3/32" rubber. There are 28.35 grams in one ounce.
Calculations will be for mail order only, as finding rubber strip in the correct size in a hobby shop is difficult and very expensive.
First calculate the length of rubber in feet in a one pound box knowing that rubber
weighs .0596 grams per inch for 3/32" width rubber that you will be using.

Price for one pound of 3/32" rubber is $23.00 + $5.00 shipping

Hints on How to Approach the Exercise


To compute the total cost for the different options, first compute the quantity of materials needed allowing for waste or broken pieces.

With the requirements, create tables of quantities needed of each material, cost per piece, calculations, and extra charges.
For the balsa in sheet wood, the width of the sheet (3") must be divided by the width of the strips needed; either 1/8" or 3/8". Remember to allow 10% waste.
Divide the number of pieces in each sheet into the total pieces needed to arrive at the number of sheets needed.
Three motor sticks can be cut from each 36" strip.

No doubt there are different methods to solve this, but I chose to convert grams to ounces and one pound to 16 ounces. Divide Ounces in a Pound by Ounce per Inch. Convert to feet.


Only need to make sure there are more propellers than needed when ordering propellers in packages of 35.

For an explanation of many aspects of simple aerodynamics with math problems check out my article Basic Aerodynamics With a Lesson

Wednesday, March 20, 2013

Compressed Natural Gas

Thanks to an invitation from Chris Schneider of Honda Motor Werks I attended his presentation at the local high school on compressed natural gas vehicles for an environmental studies class. This isn't a new technology but the popularity has been increasing and now we have a local gas station that offers pumping of compressed natural gas. The Honda vehicle that Chris has been driving has achieved up to 50 mpg with a fuel that is selling for $1.60 per gallon. The range is close to 300 miles.

The issue of fracking did come up which is a real concern in my area because of the growing sand mining in the area. Presently only about 20% of the natural gas is through fracking. What Chris was promoting as a better solution was using methane sources of gas to create the natural gas because the escaping methane is such a harmful greenhouse gas.

CNG Tank

There were some good student questions and then we went outside to exam the Honda automobile that operates on compressed natural gas. It was unfortunate that it was so cold outside but I did managed to take a few pictures.

Bill Kuhl


LED Light Bulbs

Latest LED Bulb I purchased 60 Watt Replacement for $20

I am fascinated by any new energy efficient technologies so have started replacing light bulbs in my house with LED light bulbs. Before that I had replaced some of the bulbs with CFL bulbs but have to admit there are some negatives with the CFL bulbs. Some CFL bulbs have a rather strange light color and are really slow to come up to full brightness.  If the bulb is being turned on and off often it might not last very long either. Then there is the disposal problem for a bulb that contains mercury.

LED bulbs are made up of a semiconductor material like a transister. Many small LED's are grouped together and must be supplied direct current electricty which requires components to convert from the alternating current supplied to the light socket.  The LED's are heat sensitive but do not give off too much heat, the light bulbs do tend to be rather heavy because heat sinks are part of the bulb.

The first LED bulb I purchased was the Sylvania bulb that is labled to be a 40 watt replacement while using only 8 watts.  At the time I purchased this bulb it was $20, larger wattage replacement bulbs were not to be found in the store.  About a year later I would purchase this same bulb for $10 and a 60 watt replacement for around $20.  Most people would question the economics of buying such expensive bulbs, the payback will not be quick at this time for sure. LED bulbs should last at least 10 times as long as incandescent bulbs and use about one fifth the energy.  In my case this is more like an experiment and when I have the urge to do some impulse buying, I invest in another expensive light bulb.

Bill Kuhl

Monday, March 18, 2013

My First Radio Control System

My first radio system was a used Controlaire six channel reeds system, which was really only three functions. This system was out of date when I got into RC in the 1970's. The receiver contained a "reed bank" that consisted of metal strips that would vibrate a certain tone and the corresponding servo would move. Receiver had to be placed in the plane a certain direction for the receiver to operate.

The radio worked pretty well until one day it quit working right after take off in a Midwest Esquire. When the tank ran out, the plane was so high you could not see it. A farmer found the plane several miles away a couple of weeks later. His cows had done some damage to the wings but I repaired the plane and put in proportional radio equipment.
 Reed equipment was not proportional, moving the spring-loaded toggle switch on transmitter started servo moving in one direction until the switch was returned to neutral, then the servo returned to neutral.  Throttle servo did not return to neutral but stayed at the position it was at when the toggle switch was returned to neutral.  Only one function could be performed at a time.  There was no trim or servo reversing.

I later sold the plane for someone to learn on. Another guy sold him a radio and helped him fly the plane. When the owner of the plane got in trouble, he handed the transmitter to the instructor and the plane crashed. The instructor looked at the transmitter and the power switch was off. He asked the student why he shut the switch off and he said, "when you are operating power equipment and there is trouble, the first thing you do is shut the power off." Not a good idea with RC equipment. 
Bill Kuhl 

Aero Ace Biplane - RTF RC Airplane

In my opinion one of the best toys ever sold was the Air Hog Aero Ace Biplane. Sometimes sold for as little as $20 was a radio control electric biplane that was almost indestructible. It was controlled by varying the speeds of the two electric motors that powered the plane. Move one stick right or left and the other stick on the transmitter controlled motor speed which controlled the climb. Not the most precise control but it worked. The plane was made of a compressible foam that would absorb just about any damage when you did crash. Three frequencies were used for these planes so three planes could flown at one time.

Three Frequencies Labeled as C- A - B

I managed to purchase six airplanes with a pair of planes on the same frequency. This way I could have three people flying and have the other three airplanes charging. At least a couple of times I had done a demonstration at a university for engineering students and then had them take turns flying the little biplanes.  Another time I had a group of handicapped people flying the planes and they did well flying the planes.

There would be other Air Hog RC planes come out after this, to see what is currently available check out this link:   It did seem that the popularity of the planes did decline within a couple of years.  I put the electronics gear in one of my Foam Jet II foam gliders and it flew really well: Foam Jet II Webpage

Bill Kuhl