Tuesday, December 31, 2013

Path to Learning Physics

2013 has been an interesting year with my science guy activities but for 2014 I want to concentrate further on the educational aspects related to the projects on my website. I have been going through a process of trying to re-educate myself on much of what I might have learned in school in math or physics courses. Besides reading books there are so many educational tutorials on the Internet that are really helpful, a resource not available when I was in school.

An outline on how to approach learning physics and math which are so interrelated seemed to be a good first step for me.  To me it starts out with working to get the basic understanding and then work with the sample problems to be become more comfortable. I am finding some of the model aviation books that were rather technical in aerodynamics are now making more sense to me.

My Outline for Learning Physics includes becoming comfortable with the following:

  • The vocabulary
  • The symbols used in equations
  • Units of measure especially the metric system
  • Working easily with the trig functions
  • Working with and interpretation of graphs and working with data
  • Force diagrams

Feel free to comment or add to my outline items.

Happy New Year,

Bill Kuhl

Friday, December 27, 2013

Leonardo Da Vinci Ornithopter Kit

After building the Leonardo Da Vinci Pathfinder kit for the Aerial Screw I decided I just had to build the other flying kit, the ornithopter or flapping wing.  Leonardo was truly an amazing man but I do not think I will get a tattoo of a Leonardo sketch just because Miley Cyrus did.  Working over the Christmas holiday I had the kit assembled in a couple of days, the fit of the parts was good. My plan is to use both of these models in another aviation history presentation.

Completed Kit

Like the Aerial Screw it appears that no prototype was ever actually built by Leonardo, just the same the thought that was put into this is really amazing for the time period.  Model ornithopters are fairly common and I have built or bought a couple.

The Parts

Pilot Cable System Pulls Down Wings

Crank Mechanism Pulls Shaft Back and Forth 
Wings Levers Pull Down and Wings Go Up

The gears that were used in both kits made from wooden dowels and wood circles were of interest to me also, this type of gearing was typical for Leonardo's ideas. To find articles of this on the Internet I had to turn to my model airplane friends on the Internet to point me to the correct terminology. This type of gearing is known as "peg and cage"; the cage gear can also be known as a "lantern gear". The gearing part was just for model operation, if full-scale version the idea was the pilot would be pulling the wing halves down by a cable system as can be seen in the model.

Peg and Cage Gears

I find it interesting that it was not until 2006 that a man carrying flapping wing flying machine flew successfully. This was with the help of a model jet engine providing 60 pounds of thrust and the flight was only for 14 seconds.  Another flapping wing airplane without an engine was also tried but this was towed aloft.  Human powered propeller driven airplanes carrying humans have flown for many miles.

Bill Kuhl

Tuesday, December 17, 2013

Understanding Seconds Squared

In dealing with any physics problem of acceleration you will run across the notation of meters per second squared  m/s² often.  It has been established that the acceleration due to gravity is 9.8 m/s² whether a young Sir Isaac Newton was really hit on the head with an apple and came up with the theory of gravity is questionable.   The square of a number means multiplying it by itself 4² would be 4 x 4 = 16.  It is easy to visualize units of distance squared but the idea of time squared just did n’t make sense to me.  With a quick Internet search I found I was not alone, many people have been asking to have this clarified, and the following are parts of the most understandable explanations for me.

Distance Squared easy to visualize
Think of it Like This

One way of thinking of this is by wording it meter per second per second or as the velocity per second. This can be written out as   velocity  (meters per second) / time (per second).  If you look up the rules for division of fractions you multiply the divisor by the reciprocal.  In other words the numerator and divisor are flipped around the same can be done with the m/s² notation.

Bill Kuhl

Monday, December 16, 2013

Leonardo Da Vinci's Aerial Screw

Completed Kit Leonardo Da Vinci Aerial Screw
Always on the lookout for possible visual aids for aviation history presentations I came across a kit for an “Aerial Screw”, a design that Leonardo Da Vinci had drawn up but never built.  Leonardo was a man of many talents especially for such famous paintings as the Mona Lisa and the Last Supper. Born in 1452 his idea for a helicopter was way ahead of its time considering the first successful man carrying helicopters did not fly until the 1940’s.

Parts for the Kit

The kit is produced by the Pathfinders company in Canada along with many other wood kits. I was really impressed how well the parts were cut out from wood with a smooth finish and no sanding marks or laser burns.  For me the instructions were pretty good but dimensions are in centimeters so a ruler with metric scale is needed.  Working over the Thanksgiving holiday I had the kit assembled within three days using the white glue that is provided with the kit.

Turning a crank the upper screw part of the model turns.  Leonardo thought that four men could be turning cranks to produce enough thrust to lift a full-size Aerial Screw. We know now that would be impossible.

Very short video of cranking the Aerial Screw:

Bill Kuhl

Tuesday, December 3, 2013

Computer Programming in My Past

I ran across a brochure from Watkins Agri the other day that had a graphic representing the output from a computer program I had written many years ago.  Watkins Products based in Winona Minnesota best known for consumer products such as their vanilla also had an agricultural division for many years.  When I worked there as a computer programmer/operator I wrote a program in Turbo Pascal language to create a graph representing milk production in relation to feed additives that Watkins sold.  This would seem to be a good application for a spreadsheet program like Excel but there must have been a reason for not going that route at that time. It was later converted to run through a spreadsheet.

Not Actual Output from Computer

Another project I had was converting the ration balancing program from running on a terminal to running on a smaller system.  The original plan was to convert to a small Unix system, in fact another person and myself went to Unix training.  For whatever reason that I cannot remember now I ended up converting it to run on a personal computer.  The program was written in COBOL and I transferred it to a pc-based COBOL language with no understanding of how the program really worked.  Amazingly it ran faster on a pc even back over 20 years ago.

Ration Balancing Program Ran on CRT

There was another picture of the computer room in the brochure which I worked in also as an operator, never really liked that part of the job.  In the picture there is a punch card reader that was used for doing a certain type of correction but was later phased out.  To the left were the big removable disk packs that were used for some storage and in the background you can see the big tape drives.   Computers sure have come a long ways.


Computer Room

Agri Lab Test

Bill Kuhl

Monday, December 2, 2013

Phantom Flash - Learning From My Mistake

Just completed a Phantom Flash rubber powered free flight from a kit sold by Volare Products with laser-cut parts. The kit is excellent but I think I lost the wing hold down rubber band and substituted a different rubber band. The Phantom Flash is a classic 1937 design by Joe Konefes and was a Comet Kit at one time, the plans can be easily found on the Internet for download. It was my introduction to indoor rubber power flying, my friend Floyd Richards gave me a copy of the plans and had me order really light balsa. The plane flew very well but I had trouble with ground looping for ROG take off.
Missing a Landing Gear Leg

Too Much Climb on this Flight

Landing Gear Intact

Shim in Front Rubber Band Wedged in Rear

Laser-cut Kit Includes Everything even LIGHT Tissue

It was fairly warm this past weekend for late November so I did test flight on my newly completed Phantom Flash. At times the wind was gusty and the ground was very hard but the chance to try out a new plane is always a thrill to me. First flight started fine but plane turned too much to the right and went into the ground rather hard. The plane appeared to be constructed straight so I was puzzled to why there was so much turn, the climb was rather erratic also. Sometimes too much up and other times not enough, on closer inspection I noticed the wing was angled too much one way. The rubber band I had used was not holding it down with enough force allowing the wing to shift which is why the plane would change trim. This was my fault in that I had lost the rubber band that came with the kit and substituted another one, I do not think this one had enough tension.

The plane also needed the wing ahead slightly farther for center of gravity balance but moving it ahead too far the motor stick was angled down which created less positive incidence. For a temporary fix I shimmed up the front wing support and I wedged part of the rubber band into the rear wing support.  Now I was getting good flights but the balsa landing gear had taken a heavy toll, I just kept flying. If I had the wing fastened securely from the start flights would have been better and the landing gear might have been fine. On the other hand maybe using all wire landing gear is a better idea but then that would destroy the nostalgic look.

Important Note: 
It has been suggested the balsa landing gear be reinforced by covering with tissue. Some people have used thin carbon strips for reinforcement also. Another suggestion is to make wire loop in the landing gear to absorb the shock.

Bill Kuhl
Embrace the Challenge

Monday, November 25, 2013

Bernoulli Versus Coanda or What Keeps the Ball Flying

There was an insurance commercial where a woman proclaimed that if you read it on the Internet it had to be true. The more I read on the Internet the more I question the validity of anything I read but that is true for all sources of information.  The path that lead me to the research on air flow started with purchasing a simple kit at Radio Shack known as the RadioShack Turbo Air Kit, cost under $10.

Air Stream Pointed Straight Up

This project assembles very quickly and no soldering is required, what it demonstrates is flying a foam ball in a stream of air. Many people have done this same experiment with either a vacuum cleaner reversed or a hair dryer and a ping pong ball.  Once you get the ball positioned correctly in the air stream it tends to stay in the air stream even if the column of air is tilted but at a certain point the ball will fall out of the stream if tilted too far.

Air Stream Titled at an Angle

What started the confusion and the controversy is when I tried to research physics behind this. Air pressure is pushing the ball upwards with more force than the force of gravity pulling it down, I think everyone would agree on that. The physics that keeps the ball centered in the column of air is where opinions differ.

 Many people cited the "Coanda Effect" for the explanation but other people said it was because of Bernoulli's Principle.  Really trying to simplify the Coanda effect is that it deals with fluid moving around a curved surface. Bernoulli's principle correlate an increase in air velocity decreasing pressure. 

Back of Spoon in Water Stream

The classic example of demonstrating the Coanda Effect is holding the back of a spoon in a stream of water. There is an article on Wikipedia that disputes this experiment as a valid demonstration but this article is labeled as questionable. When doing this research this leads into the discussion of how an airplane wing actually works which appears to be an even bigger can of worms.

Bill Kuhl


Friday, November 8, 2013

Experimenting with NASA FoilSim Website

I have been interested in the more technical side of my hobbies and projects lately and took another look at the FoilSim program on the NASA website.  Your computer needs an update to current version of Java to run and there could be a splash screen about a risk to accept on to get things started.  Through your web browser many aspects of airfoil performance can be simulated in an interactive manner. There is a disclaimer stating that it is for educational purposes and not for designing aircraft.

Link to FoilSim: http://www.grc.nasa.gov/WWW/K-12/airplane/foil3.html

Opening Screen with Default Values

To start with I used default values which provide a wing of 100 square feet flying at 100 mph then I selected the flat bottom airfoil and the flat plate airfoil. Next I started increasing the angle of attack from zero in one degree increments, output data from this included amount of lift, drag, and L/D. To me it was interesting to note that L/D increased until about 3 degrees and then started to diminish. Which means at this point the drag of the wing is increasing faster than the lift.

Starting at 0 Degrees with Flat Bottom Airfoil

Increasing to 3 Degrees

The same data was entered for a wing that might be typical for a small model airplane with a wing area of only 1 square foot flying at 15 mph. Output was somewhat different but followed the same basic pattern. Calculations were also done for the flat plate airfoil.

Changing to Model Size Wing Section

For me this is interesting because I had read many books on model aircraft design theory and it was fun to see the theory simulated. For one degree value of the model size wing I changed the aspect ratio from 4 to almost 8 to see the change in L/D, it improved considerably as predicted.  My data and some of the output were entered in an Excel spreadsheet manually.  Take a look at this fun simulator.

Entering Data into Excel

Bill Kuhl

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

Monday, October 28, 2013

Guillow's DHC-2 Beaver Flies & What I Learned the Hard Way

I think it must be human nature to go ahead and do something first and ask questions later.  That is my excuse for my Guillow’s DHC-2 Beaver free flight rubber powered model to electric power radio control project.  When I purchased I had intensions of building it rubber powered but there just appeared to be so much balsa in the structure that I thought it would be too heavy to fly very long.  To me the electric systems in the small RTF electric airplanes seemed so light and the motor was so powerful that a little extra weight would not be a problem.  After I started building I found the Stick & Tissue thread on Hip Pocket Builders Forum and found out that keeping weight to a minimum could be a real problem.

 When I just about had the airplane finished I tried advancing the speed of the motor and I noticed the propeller shaft was pulling ahead and the gears were slipping. The cowl had to be cut off to get at the motor and then the wires to the receiver were so short I had to cut a big hole in the fuselage to get it connected again.  At least I lengthened the wires after securing the back of the shaft so it would not come ahead. With everything put back together I tried flying it without charging the battery, it flew for a short time before there was not enough power to keep the motor running.  Charged up the battery and this time I tried to fly it the propeller was slipping on further inspection of the plastic gear the gear teeth were ground down. 

Plane Opened Up to Access Radio

The cowl comes off again and I put in a whole new motor/gear drive combination, the cowl is only taped on for now.  A wrecked Parkzone Champ RTF airplane was the source for all the electric components.  Yesterday the wind dropped just before the sun did so I took the airplane out to fly again and fly it did. The problem was if the airplane was not launched with a hard throw it would stall, once it was flying it flew fine and would maintain level flight at half throttle.   

With these observations in mind I did additional reading on the Stick & Tissue RC thread and found out how critical the weight is, the CG balance, and that some people use washout in the wing to help with stalling. My DHC-2 Beaver weighs 72 grams while the Parkzone Champ only weighs 38 grams, from my reading it seems that often the converted planes weigh 80 grams so I did pretty good.

For the next flying session I have removed the tail wheel hoping to move the CG forward and will try additional weight in the nose if I have to.  I have another Guillow’s kit that I plan to convert to RC, a Cessna 150 hopefully I can build that even lighter.  Like other people on the Stick & Tissue RC thread I finding making these planes fly well rather addicting.

** Update 10/28/2013 **

Removing the tiny bit of weight from the tail wheel improved the flying. I had a flight of 10 minutes on the 160 mah lithium battery, even did a loop.  As I have read weight removed from the tail makes a big difference in the balance.

My First Article on DHC-2 Beaver Conversion

Bill Kuhl

** Update 10/4/2014 **

Flying Inside Large Gym

Embrace the Challenge


Wednesday, October 23, 2013

Clifford Quinn You are an Amazing Person

Clifford Quinn I think you are truly more amazing than myself, hopefully in my retirement I will be able to personally reach out to more kids with my activities for now most of what I do is through the Internet.  Thank you so much for the samples of your kite design, it is so simple yet so wonderful in that it so easy to construct and flies so well.  The kite design I had created takes much longer to build and requires using hot glue guns. 
I received the following email from Cliff that I just had to share:

Hello Mr. Kuhl , you are an amazing person... I was searching the AMA site and came across your activities,, fantastic stuff. Please let me introduce myself. I'm Clifford Quinn, I live in eastern Pennsylvania and I have an addiction to Kites. I design kites, make kites, and teach kite making with adults and children. My real enjoyment is working with children.  This summer I spent 4 weeks teaching workshops in children's summer camps.  Kites are an excellent teaching tool.  Science, math, physics, art, history and culture all are tied together with kites. I also go to schools, children's clubs, scouts, actually anywhere I can pass on my passion and teach kids.
   I've been involved with kiting since the early 90's and being retired I have the opportunity to share and make a difference in the lives of children using kites to develop their skills while they have fun.  Besides improving knowledge flying kites are a family activity when parents spend quality time doing something together. In these times cohesive families are so important.
  I'm a member of the American Kitefliers Association  (a 501c3 organization) and on their Outreach Team which is devoted to educating and sharing the joys of kites
The purpose of my e-mail was to introduce myself and to see if you have an interest in sharing information and perhaps working together.

I look forward to your favorable response.

Flying Sample Kite

There are several articles on the Internet about Cliff:

Bill Kuhl

Embrace the Challenge

Monday, October 21, 2013

Rob Romash - Capacitor Powered Model Airplane

In this blog post I am going to start with a little name dropping, Rob Romash has competed and won at the highest levels of model aviation. So when I found out he was designing model airplanes for the toy industry I knew that these model airplanes would fly well. Past experience with model airplanes purchased through toy outlets is that such model airplanes are overweight, underpowered, and fly in an unstable manner.  In a recent phone conversation with Rob I found out that his Flash Fighter capacitor powered model airplane that looks like a jet fighter aircraft is available through Radio Shack. Cracker Barrel is another outlet for his products but there is none where I live so I purchased the Flash Fighter and the Flash Copter at Radio Shack.

Flash Fighter Flying High 

I was anxious to try out both products but the weather was not the best, I did get some flights in before it started to rain and hail. Both products use the same type of charging station which contains 3 AAA batteries. Charge for no more than a minute and launch the flight time will depend on how long the charge was giving some control to how far the flight might range out.  Even with 30 second charges in windy weather the Flash Fighter flew a good flight, the Flash Copter went higher than I would have imagined.  In comparing the Flash Fighter with another capacitor plane that I bought from a toy store that was about the same size, Flash Fighter weighed half as much. A lighter plane will normally climb higher, fly longer, recover better from upsets, and not break as easily.

My experience with capacitor powered model airplanes is from purchasing two toy airplanes and also for building a capacitor model airplane to conform with a Science Olympiad trial event known as Wright Capacitor. The first toy capacitor airplane was from Estes which was at least light but would start to gyrate in pitch before the end of the flight, I put the electric components of that plane in a balsa plane that flew better. Another toy capacitor plane was just too heavy but with enough adjusting I got it to fly. My Wright Capacitor airplane flew well and I used it to mentor a Science Olympiad student that was competing in the event.

Wright Capacitor Plane I Had Designed

Estes Capacitor Plane

Estes Electric in Balsa Airplane

Flash Copter Insides

  Additional Resources
Eclipse Toys website
About Rob Romash
Mini-Stick Poonker Plane by Rob Romash
Mentoring Over the Internet Over the Internet - my blog post about Wright Capacitor
My Wright Capacitor Airplane Flying Outdoors
Too Heavy Capacitor Airplane
Estes Capacitor Plane Components in Indoor Plane

 Bill Kuhl

Friday, October 18, 2013

Rigid Construction for a Simple Rubber Airplane

For me learning something new when taking on a new project is always a thrill.  I have been reading about a simple rubber powered free flight model known as the Blue Ridge Special that uses a more advanced construction technique that creates a very rigid structure.  One person had referred to this as “Union Jack” construction, my search for this brought up mainly information on the official flag of the UK which is known by the same term. The angled lines in the flag do have the look of a pattern of diagonal and crossing horizontal lines like you see in the wing structure.  Diagonal ribs connected to a spar through the wing make for a wing that is very rigid. Tail surfaces also have diagonal bracing.

The price for the kit of the Blue Ridge Special is reasonable but it appears that it is not available right now as a note on the Pal Model Products website indicates they are busy working on products.  I was able to find plans that were similar to the kit and used hobby shop balsa so my plane might be slightly heavier than the kit, weight was 11.32 grams without rubber.

Wing Structure

If you have built other simple rubber models of this size you might be wondering if more advanced construction technique is really necessary. This type of construction is normally seen in higher-powered glow or electric free flight models that scream skyward which can cause wings to flutter.  What I have noticed is that my plane as well as the Blue Ridge Special planes other people have built flew perfect from the start with no trim adjustments needed.  I have to believe that with this method of construction it is easier to build an airframe with no warps.

The airplane has only been out for one flying session so far but it flew very well. Most of the flights were with 3/32” rubber using a 6” diameter propeller.  It was rather windy and I sure did not want lose the new plane so I did not use anywhere near maximum winds in the rubber.  The airplane climbed but not steep, I tried 1/8” rubber with even fewer turns and the climb was steeper.  I am really anxious to try more winds on a calm day and see what this airplane can do.

Bill Kuhl


Additional Resources

New - Blue Ridge Special now available from Volare Products

Thread on Hip Pocket Forum About Blue Ridge Special