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

NEWS FLASH Kit Available Again New Link

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

Blue Ridge Models Website 

Thread on Hip Pocket Forum About Blue Ridge Special

Tuesday, October 15, 2013

Comparing Two 2-Meter RC Gliders

To be a good scientist it is important to record accurate data but I still think there is some value in making some estimated observations. Recently I started flying a heavy 2-meter radio control sailplane with a fiberglass fuselage and sheeted foam wings. Weight of this glider is 53 ounces which is a little over 3 pounds.  Besides the heavy structure of the fiberglass glider there are 4 servos in the wing plus the 2 in the fuselage. The fiberglass glider is very sleek and no doubt has less drag than the Gentle Lady Sailplane.  Weight of my Gentle lady was 27 ounces which is just about half the weight of the fiberglass glider. The gentle Lady plans show wing area of 663 square inches, I will estimate the wing area or the heavy glider to be the same.

This would give wing loadings of:
Fiberglass Glider  11.5 ounces per square foot
Gentle Lady balsa  7 ounces per square foot

In a previous flying session with the fiberglass glider I had one very good flight in thermal lift of close to 10 minutes. During my comparison day of flying both gliders I had a much better flight with the lighter Gentle Lady. As I have read there are situations where one glider will perform better than another.

I have been studying some about the Lift over Drag Ratio (L/D) after the new record in the Red Bull Flutag event. L/D or glide angle does not change with weight, only the speed down the glide slope changes with increased weight. To me this has been a little hard to believe it is true but I think comparing these two gliders is proving it to me in a visual way.

Drag Reducing Features of Heavy Fiberglass Glider

For a comparison I gave a hard hand launch to both gliders from the same spot. The heavier fiberglass glider did not climb as high in the launch but glided down the field what appeared to be twice as far as the lighter Gentle Lady glider. Besides reduced drag the heavier glider had more kinetic energy pulling it along but to me it was also obvious the L/D of the fiberglass glider is better.

Drag Sources on Lighter Gentle Lady Glider

Besides the small items on the lighter glider that are sticking out into the airflow such as rubber bands on the wing and control horns, the airfoil of the fiberglass glider appears thinner. The more I experiment and compare model airplanes the more I realize that airfoils do matter. Sometimes by a huge amount.

Bill Kuhl
Additional Blog Posts on Soaring
Thermal Soaring This Week
ALES Sailplane Contest
Competition Altimeter for Models - CAM
e-flite Umx Ask 21 Sailplane
STEPS for Girls Summer Program 2006
Slope Soaring Trips
My Start in Radio Control Glider Flying

GoPro Strapped to Gentle Lady Creates Lots of Drag

Monday, October 14, 2013

Syringe Hydraulic Arm - Send Sample Pictures

It is very seldom that I ever get a chance to see how the projects on my website are built by other people. Other than the classes I have taught using the projects which use a kit I make up do I get a chance to see completed projects, very few people ever send me pictures of the completed projects. By chance I found this image of a Syringe Hydraulic Arm that used many of the ideas from my article but is slightly different. I think that is great that people are using their own ideas too with the projects.

SERC version of Syringe Hydraulic Arm

I happened across the above image on the SERC Home School Blog which appears to be connected with the Smithsonian which is closed down now because of the government shutdown. It also appears that the hydraulic arm inspired from my design was used as a demo for the kids.

Syringe Hydraulic Arm I Built is my email to send image files.

Bill Kuhl

Tuesday, October 1, 2013

Pink Floyd Foam Slow Flight RC Airplane

Inspired by my visit to the STEPS program and full of new ideas I set out to design another type of airplane that would allow for easy swapping of the radio control unit and also an electric motor that provided the thrust for the airplane.  The pod unit that housed the radio and electric motor was built from thin plywood but almost the entire airplane was constructed from pink and blue foam with some carbon fiber for reinforcement.
Pink Floyd RC Slow Flight Airplane 
Flying Before Adding Landing Gear
My friend and mentor Floyd Richards had built a very easy to fly airplane that started as an indoor RC airplane with conventional 3-channel controls that he would later sell to me. Construction was primarily balsa framework but there was a pod of blue foam. Most of the flying I have done with this airplane was outside in very low wind conditions using the plane to let anyone fly a radio control airplane. The airplane had such a low wing loading and flew so slow that some people could solo this plane on the first flight.

Airplane That was Inpiration for Pink Floyd

When I designed my airplane which I called “Pink Floyd” I built an all foam airplane of similar proportions.  This airplane was easy to fly but flew some faster at a higher wing loading but still very slow. This airplane has been flown indoors in larger gyms successfully but it was really more suited for flying outdoors in low wind conditions.  The fall of that year I would return to show people at Stout my ideas with the Pink Floyd doing flight demonstrations both outdoors and indoors.  Teaching someone to fly this plane indoors even in a very large gym would be difficult because the altitude is really limited and not the two mistakes high that RC instructors like to have their students fly at outside. Pink Floyd wingspan is 48” with a huge chord which makes it easy to see. As of yet I have not pursued using this airplane for a group project but I think there is potential.

Removeable Radio and Power Pod

Removeable Pod used for STEPS Glider

Camera Attached

Aerial Picture Taken

Bill Kuhl