Monday, December 29, 2014

Blue Ridge Dart Rubber Model

Recently someone had sent me a model rubber powered model airplane kit known as the Blue Ridge Dart.  This is a simple all-sheet balsa airplane that had the surfaces already cut out of very nice balsa. To me the wingspan appeared rather short for the length of the fuselage but no doubt that could contribute to the stability of the flight.

Blue Ridge Dart in Flight

Total build time for the plane was probably less than 30 minutes. The moveable wing mount feature was not used by me; instead I pinned the wing on for test flights and then glued the wing to the fuselage. First flights were with reduced winds in front of my house on Christmas day. Later in the day I flew in a larger field with the wing glued on, a small amount of clay was needed for nose weight. I later removed weight towards the tail so hopefully the clay will not be needed.

Test Flight With Wing Pinned On 

With a modest number of turns using a winder the airplane flew in a nice right pattern.  After the climb the plane returned smoothly to level flight and flew slower than I would have expected. As the rubber turns wound down the glide was fairly flat also unlike many small models that head down in a steep spiral.

Now for the bad news, I do not believe this kit is currently available, the Pal Model Products website indicates they are busy creating kits. There was another kit sold by this company known as the Blue Ridge Special, I built a similar model that I reviewed in this article: Rigid Construction for a Simple Rubber Model.

Nice Cruise

Bill Kuhl

Wednesday, December 17, 2014

Science Olympiad Wright Stuff 2015

I recently discovered that for 2015 there will be a rubber powered free flight model airplane event as part of the Science Olympiad.  The last few years there have only been events for catapult launched glider and rubber powered free flight helicopter. There was a trial event for a capacitor powered free flight airplane that I helped a student with online, not an easy task but they did very well.

Student with Wright Stuff Airplane

In 2002 I found out about students that had started with the rubber powered free flight Science Olympiad event and progressed to the most challenging indoor event F1D and won for the US in international competition for their age group. With the help of several people I wrote an article about this that can be seen on the Web at

Plane Overhead

Locally we have never had any Science Olympiad competition but I drove 70 miles one way to help students in Menomonie Wisconsin at least twice. That really wasn’t enough time to be of much help but I did get to see part of the competition.  Some of the older guys including myself that were flying indoors locally using planes that conformed to those rules and had our own competition.

Wright Stuff Plane I Constructed 

Flying Over the Crowd

Rules for 2015 are similar to in the past but not as restrictive in that you can build your own propeller and carbon fiber is allowed in the construction but not boron fibers. There is also a maximum weight for the rubber motor.  Entire rules are not available for free on the Internet but a CD can be purchased or there is a phone app available for a fee.

Wright Capacitor Model Student had Built

Related Links

The Right Stuff for the Gold
Interviews of Some of the Stars in this Event 
Right Stuff Continued - 2002 F1D World Championship
Freedom Flight Order Page – included to give description of available kits
Science Olympiad Wright Stuff Division C
Mentoring Over the Internet - Wright Capacitor Event 

Bill Kuhl

Updated 4/30/2015 - State Tournament Flight Chris Lung

Updated 1/2/2015   Video of Wright Stuff 2014 in Montana  

Update 1/21/2015 As a Result of this Post I Connected Chris Lung With a Club in His Area

Thursday, December 11, 2014

Airfoils and an Aviation Inspired Student

Working with young people that can utilize a small amount of direction that you give them and then follow through on a project is one of the biggest thrills I have had. An area school that I have visited on several occasions to consult on project ideas for a science teacher friend referred a student to me last fall. This is part of the email I received:

One of the classes that I chose to take this year is called Engineering Research.  This class consists mainly of working on a project that you will take to the science fair in Winona later in the year.  There is a wide variety of topics to choose from to base your experiment on.  

In the past few years, I have become very interested in airplanes.  One of the main reasons for this was that I recently went to the airshow in Oshkosh, Wisconsin.  Seeing all of the planes and jets was very fascinating to me.  A few months ago, I joined a club that will allow me to learn to fly airplanes and eventually get my pilots license.  When I graduate from high school, my main goal is to attend the US Air Force Academy in Colorado Springs, Colorado.  My second choice would be ROTC Officer School and my third choice would be Air Force enlisted.

As you can probably tell, I plan on being around airplanes for the rest of my life so I am very interested in doing my project on airplanes. “ 

Model aviation has been a huge part of my life and I was so happy to try to help this student, I sent him several ideas. The area he was most interested in was to design airfoils and test in a wind tunnel. I had sent him a link to the blog post I had written,  “Experimenting with NASA FoilSim Website”. The student took this to a higher level and actually designed some airfoils.

As plotting the airfoils were beyond my experience I enlisted the help of some online friends, Thank you Gary, John, Manuel, and others for your direction. With an online utility from Airfoiltools templates were printed out and I got out my foam cutting equipment to create wing sections. 

Main Part of Wind Tunnel

Yesterday I met the student at his school and we worked on cutting out an additional wing section.  In the lab area he showed me the wind tunnel he was working on and described the diffuser part he was working on at home to dampen the air coming from the fan unit. There were other science projects in the room such a solar collection system that he briefly described to me as well.  He also told about how he had joined Civil Air Patrol and had recently gone for a flight in their airplane.

There is more work to be done but I am completely confident this student will be follow through on this project.

12/21/2014 Update - Another airfoil completed and ready for testing.

Bill Kuhl

Working Wind Tunnel Update 12-16-2014

Tuesday, December 9, 2014

Newton's Laws and the Hybrid Car

I think the biggest reason I purchased a hybrid car was my fascination with the engineering that gives the car such good efficiency. Understanding the basic physics of the car possibly might increase the mpg that your car obtains, this past summer I had reached a 53.5 mpg average. The following post is my attempt to relate some basic physics to how the hybrid car functions. If there are great inaccuracies let me know.

Newton's First Law – object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.   Law of Inertia

This means that a car that is not moving will take a force to get it moving, this normally is provided by converting chemical energy into mechanical energy by the burning of gasoline in an internal combustion engine. Explosions in the cylinders  of the engine rotate a crankshaft that connects to gears and shafts resulting the in drive wheels of the car rotating which moves the car.

Second Law – states that force is proportional to acceleration but acceleration is inversely proportional to mass. The formula Force = Mass x Acceleration relates to this law and the unit of force is the Newton.

Newton’s Second Law relates to how much force is needed to move the car for the mass of the car.  Greater force is needed to accelerate faster and with a larger mass. 

Normally a hybrid car is powered by both a internal combustion engine burning gasoline and an electric motor powered by rechargeable batteries.  Batteries are recharged by the internal combustion engine but also through capturing “kinetic energy” of the moving car, this is known as “regenerative braking”.  

In the hybrid car when it is coasting or braking, the internal combustion engine is turned off and the kinetic energy is converted to electrical energy and stored in batteries. This can be seen in the Energy Monitor display in a Prius hybrid car, the dashed line with the arrow points from the front wheels to the battery. 

Accelerating from a Stop in a Hybrid Car

Thinking of Newton’s First Law again when accelerating the hybrid car, when you gently press on the accelerator pedal the car will start moving with the electric motor. Some of the electricity supplied from the battery may have come from what was generated in the coast and the process of stopping before the car came to rest.

In the Energy Monitor diagram above the arrow points from the battery through the electric motor and towards the front wheels.

Once the car is moving less force is needed to keep it moving. Based on many factors the internal combustion engine will start to help power the car at some point. If the accelerator pedal is depressed hard from the start, the internal combustion engine starts right away along with the electric.

In this diagram the brown arrows indicate the internal combustion engine is helping to power the car and charge the battery.

Bill Kuhl

Monday, December 8, 2014

Modification to Syringe Hydraulic Arm

Currently the most popular project on my website is the Syringe Hydraulic Arm.  Views to this project come from all over the world, with the greatest coming from India but the largest concentration of views are coming from cities in the United States. My assumption is this must be a school project in many US schools.  This is has been a project in the Engineering Through Models class for the last two years as part of College for Kids at Winona State University. Whenever I bring my sample for display kids are always drawn to this project.

Syringe Hydraulic at Summerfest 2014

In designing the arm I tried to make it as simple as possible with wood materials that are easily found and needed a minimum of cutting. I do try making improvements to my projects over time. The latest addition came about not because of any real problem but because I noticed how when the wood arm was pushed up first all the force was on a small edge on the left, then it was pushing fairly flat but then moved to the opposite edge. What was missing from my design was a pivot point between the plastic syringe plunger and the wood arm.

My easy fix to this has been to cut a short length of rigid plastic tubing and hot glue it to the flat surface of the syringe. The wood arm now moves around the curved surface of the tubing and it appears the operation is smoother.  Ideally I think the better solution would be to come up with a bearing that has a round shaft pivoting in a tube. I will have to give this greater thought, if you build the project maybe you will have a better idea.

Rigid Tube Added 

Bill Kuhl

Related Articles

Monday, December 1, 2014

Walkalong Gliders and Indoor Flying

With the cold temperatures outside I have been trying to do some type of model flying indoors whenever I can. Slater Harrison aka ScienceToymaker had sent me some of his latest foam walkalong gliders when it is warmer for testing but I am just now getting more serious about trying the gliders at different places.  The gliders are so light that any unwanted air movement can disturb the flight. A couple of weeks ago I was doing an impromptu demonstration at Everything Hobby of one of the foam gliders. I was able to fly through the hobby shop fairly well until a door was opened changing the airflow.

Walkalong Flying at Everything Hobby

Model Helicopters and Quadcopters at First Gym

Last week I took some vacation time before Thanksgiving and was able to do some flying in three different gyms. I tried demonstrating the walkalong gliders in the first gym but the airflow from the heating system made it really difficult. The radio control helicopters and quadcopters were not bothered so much from the airflow.  I tried to demonstrate a simple rubber powered free flight plane also, the AMA Racer. It tolerated the airflow better and even interested a boy there with his father to want to fly it. My coaching wasn’t good or he wasn’t listening as he tried to launch it like he was throwing a baseball and that didn’t work too well. 

AMA Racer Flying in First Gym

That same evening I flew at an even larger gym, first flying the flying wing I had put together after my Guillow’s RC Cessna 150 had crashed and then the Guillow’s DHC-2 Beaver converted to electric RC. In the large gym I was able to do nice loops and even rolls.  As in each of the three places I flew, I was the only person with model airplanes constructed of balsa wood. Some people do build their own planes but still use foam as it is more forgiving when crashed into hard surfaces. Saw a really clever RC Champ made from two Champs connected together by the inside wing that flew well, the owner had thoughts of connecting three together. I flew the free flight AMA Racer here also and it climbed close to the rafters.

Flying Wing Flew Great Indoors

Double Champ

Larger Gym for AMA Racer

On the next day I flew in another smaller gym with the radio control planes, it forces you to really be aware of the wall, ceiling, and floor boundaries to avoid a crash. The other flying I did was flying the walkalong glider inside the house through three connecting rooms. I found that using a large book for a paddle instead of the big sheet of foamboard worked fine.  To be able to steer the glider through doorways and around obstacles takes a fair amount of practice. Steering with the paddle must be done very smoothly or too much turbulence will be created and the glider will head to the floor.  To keep the rear of the glider close to upper edge of the paddle, walking speed must be just right. 

Flying Through the House 

Glider Surfs a Wall of Air Next to Top of  Paddle

I find so many interesting aspects and challenges with model aviation.

Bill Kuhl

Related Links

Walkalong Glider and Foam Store

Cessna Flies and Cessna Dies

DHC-2 Beaver RC Conversion

Everything Hobby

Trying to Learn Tumblewing Not Easy

Thermal Soaring a Walkalong Glider

Tuesday, November 18, 2014

Cessna 150 Flies and Cessna Died

Not all of my model building projects turn out well, I do try to learn from my mistakes and do better on the next project. On the first conversion of a rubber powered free flight model to electric RC, the Guillow’s DHC-2 Beaver I went into the project with no prior experience with these types of conversions. After the initial problems the airplane flew very well and I think maybe it gave me over confidence for the next project, the Guillow’s Cessna 150.  

Cessna 150 Before Crash Testing

For the new conversion I had a more powerful motor/ battery combination and greater weight although I never weighed the airplane. It felt light and had plenty of power to climb, maybe too much. It was getting towards the end of the flying season and I rushed to get it in the air. The first flight didn’t seem too bad until the wings ripped off the airplane. On trying to fix the airplane and strengthening the wing joint I did not put in enough dihedral and the plane would not turn properly.

Cessna in Flight

After one flying session I grabbed each wing half and broke the wings partially loose to add more dihedral. The wings were still fairly solid on the plane so I flew it that way and it turned better. Repairing the joints with added dihedral the plane still did not turn well. It would appear to not be responding and then go into a spiral dive. Sometimes it didn’t recover before hitting the ground.  The plane never did fly super stable like the DHC-2 Beaver had. After so many repairs, I gave up. 

Wing Halves Bent Up

About this time I purchased the eFlite Sbach 342 which used the same batteries and charger as used in the Cessna. This airplane is a real performer for something so small, it does nice big loops and axial rolls. I wanted to do something with the equipment from the Cessna, so I looked through the treasures in my basement. I found a really lightweight wing structure that my friend Floyd Richards had given me, it was a symmetrical airfoil that was thick and had a good amount of wing area.

RTF Sbach 342

The idea was to build a nose on to the wing for the electric motor and add a vertical fin to build a flying wing. I rushed this project and went out to fly without checking the direction of the elevons. Sure enough this was backwards, when I fixed that the elevator action was backwards. At this point I was forced to read the manual to get it working right.

Flying Wing

It was starting to turn cold and darkness was coming early, if I was going to get a test flight in early morning would be the only time.  With little time to fly before going to work, I flew over the street in front of my house. It flew really well, stable but yet agile.  The wing needs to be recovered as the clear food wrap just isn’t strong enough. I am looking forward to flying this plane more, maybe indoors in a gym where it is warm.

Bill Kuhl

Related Articles

Only Video of Cessna Flying

Monday, November 3, 2014

Dynamic Soaring Weekend

This past weekend the winds were in a favorable direction to try dynamic soaring from a small ridge that I had some luck with DS flying one previous time.  On Saturday the wind was SSE around 10 mph, ideal direction is south or north. I tried the Alula first to see if I could possibly get it to DS, I had watched videos of Soren Jensen ds’ing the Alula but he makes everything look easy.

Slope Facing South Wind

North Facing Side

Super Scooter on the Backside

After some front side flying with the Alula I gained altitude and made a run over the backside, circled the bottom and made it back up to the top. That was the first time I made it back to the top but when it went down again must have pulled too hard as it crashed in an awkward way breaking the tail. No filament tape along so had to repair with masking tape, but that held for the rest of the day.  I never got more than three circuits but I got in lots of practice diving over the hill which was the first thing to scare me with DS.

Cracked Tail on the Alula

Next in the air was my Hyper DL which is the first plane I had success with on this hill.  It keeps the energy well through the circuits but I kept going off course, maybe because the wind was not exactly straight into the hill. Sometimes I must have pulled up too hard on the bottom of the circuit and the glider was shooting straight up, it worries me more not pulling up enough and crashing into the hill. I really don’t want to break this glider because I enjoy DLG thermal flying with it.  It was really fun trying DS again and I am slowly getting more comfortable with it.

Hyper DL

Sunday’s forecast was for south wind with gusts up to 35 mph, I don’t think it was that windy but probably a good 20 mph. This time I brought out the Super Scooter which flies well in high wind but is a much heavier wing loading.  There were times it was a struggle staying up on the front side but other times it climbed fairly high and then I would dive just barely missing the top of the hill. Controls were really too sensitive for DS and the first circuit it got inverted on me and I stuffed it in the ground. Still only masking tape for repair but I had it flying again quickly and got some multiple lap DS circuits.

Busted Nose on the Super Scooter

Took a break for lunch and came back out to try it again.  With the Super Scooter I couldn’t go as far down the backside but I was coming out farther to the front side.  I kept getting braver and came closer to the top of the hill but on the bottom turn often it would be too high and get blown off course. On one occasion I definitely heard the sound of the glider passing through the boundary layer, what a thrill.

 Several years ago I had the opportunity to fly DS on a much larger hill and it was easier but this hill does make it possible and pushes me to improve the technique.  The more I fly; the better I seem to be able to judge the energy level of the glider.  It is one thing to fly a powered plane in horizontal circles close to the ground but harder to fly circles low to a hill that is at a steep angle.

I am feeling the addiction of this challenge pulling me, like others inflicted with the DS addiction I am starting to feel flying on the front side of the slope is a little boring.  My goal this year was to make more than a single DS circuit on a small hill, next flying season I am going to shoot for a dozen or more.

Bill Kuhl

Tuesday, October 28, 2014

Getting Lost at a Scout Camp

On a wonderful recent fall Saturday I was invited to observe model rocket launching and pumpkin chunkin. The scouts had two different types of rockets, very tiny ones with tumble recovery and a slightly bigger rocket with a streamer that slowed it down, making it a little easier to see also. They were also setting up for a “pumpkin chunkin” competition in the afternoon.  I did get to see a couple of pumpkins get launched and it was amazing the distance the pumpkin was hurled through the air.

While at the camp I decided to take a hike on a trail that went into a wooded area, I had heard there was a reservoir lake somewhere in the area that radio control gliders had been flown from. I walked the winding trail that had been cleared noticing the orange plastic ribbons that were found along the path. Any moment I expected to come to the end of the trail but at some point it appeared to follow a half circle and I thought sure I was headed back to where I had started. When I thought I was getting closer I moved off the trail so people riding mountain bikes could get through. At this point it appeared like there was an opening in the woods ahead.

As I left the wooded area there was a big valley with an earth dam at the other side. I crossed a small stream on wood planks spanning the water. Someone else was walking a road up to the top of the dam; I followed them and looked out over the beautiful small lake.  Next I headed down the path I came up and followed a dirt road that two guys were coming my way on with fishing poles. They asked me how fishing was but I said I had no idea and this was the first time I had been here. As the trail went around some trees there was the parking lot for the reservoir with plenty of signs but no trail maps.

Leaving the parking lot was a crushed rock road, but which way to go, right or left? If I would have been a good scout I probably would have used an old fashion compass but I had Google on my smartphone. Turns out it wasn’t so smart but it gave me a warning it was a beta version. It had me going up the hill to the left but was showing the address I was looking for several miles away. On top of the hill I didn’t spot the camp headquarters so I went down the hill. Looked at Google again and it had me going the other direction up another hill. Spotted an exit off the road to what looked like many vehicles, I thought that must be where I came from. When I got to the driveway I could see that it was a farm place not the scout camp. So I went down the hill again and up again. Finally I got up nerve to flag someone down and asked which way to the scout camp, they pointed the other direction and quickly took off.

It was a wonderful day for a walk but this was getting to be a bit much. At the bottom of the hill in the parking lot I spotted a guy getting a bike ready to ride. I asked him if there was a shortcut to the boy scout camp, he didn’t know and his smartphone wasn’t coming up with anything useful either. I continued up the hill past the farm place and spotted the road on top of the hill that goes by the boy scout camp. I certainly didn’t want to walk that far but then I spotted the camp across a field, so walked across tall grass but it was shorter than following the road.

View Across the Field

Almost Back

Pumpkin Chunkin Testing When I Got Back

According to my pedometer I had put on 6 ½ miles that day so I would guess 6 of the miles were my trail adventure. It was now lunch time; I stayed to see a couple of pumpkins flung from a giant wooden contraption and then headed back to the city.

Happy Trails

Bill Kuhl