Friday, February 27, 2015

Aviation Interested Student at Science Fair

I caught up with the student I had given some ideas to for a science fair project relating to designing and testing airfoil sections. He had designed the airfoil sections using a online program provided by NASA, I provided him with the foam cutting equipment I use for for model airplanes.

One wing section was mainly flat on the bottom, another was pretty much symmetrical, and a flat piece of foam was also tested. The airfoils were tested at three different speeds, lift force created was measured with an electronic force probe.

From the data obtained it appeared the results were what had been expected from the data outputted in the simulator program.

It was so much fun helping this young man and he seemed really excited to see me when I found him at the science fair.

Bill Kuhl

Be Sure to Read the First Article

Airfoils and Aviation Inspired Student

Monday, February 23, 2015

Comments on Projects I Wanted to Share

Recently I ran across some comments from various sources on a couple of the projects on my website Over the several years I have been sharing these projects through the Internet, I really do not receive much feedback. Some people have sent comments now that the website is in WordPress format and includes comment capability. I have been able to help a few people with minor problems they were having,but most feedback has been pretty good. In doing this everything has been an expense on my part, I do not complain because it does make me feel good. In the back of my mind I have thought about including some advertising on my blog and website to help pay for some of the cost. This blog now has some advertising, I sure hope this will not be a turn off to some people. 

Below are some of the comments I had found for a foam glider that I named as the "Hammer Down Catapult Glider" and to the Syringe Hydraulic Arm project. I had recently sent a sample kit to a teacher friend in India and the completed project was a big hit with the students.

Hi Bill,
I have read through the .pdf and like the design. The directions seem to be simple to follow as well. I really like the use of "trash" for most of the materials. I use a lot of "trash" in my classroom. I find it is much easier and middle school and high school students are funny to watch as they oooh and aaahh of their finds in my boxes of materials. I believe that I can work this into my next unit of force, motion, and energy. If I give it a try, I will report back with how the students did.
Thanks for sharing.    Susan  

Hi Bill,
Last year when teaching about forces I had a team of retired pilots that volunteered at the Pacific Aviation Museum at Pearl Harbor here on Oahu come in to talk about planes. They brought in pre-cut bamboo model airplanes for me to teach the kids about the parts of a plane. I read through the article and I love the pictures/directions. Looks simple and something I can incorporate this year even if I can't get that same group of volunteers to come in again. The kids loved learning about the forces of flight.

Very detailed and intuitive article. I feel like the real learning would come out of the students being able to make their own glider, although this looks like no simple task, with plenty of room for error.
I can imagine going through all the motions and then being truly excited as me and my group of students run out to the schoolyard to test our gliders, only to find out that we didnt give the wing enough angle or something and the glider barely gets off the ground.

I suppose failure in this instance could be seen as a learning experience, but may also be discouraging and time consuming to have a bunch of grounded student gliders.
If all goes well, the activity could be a real blast. One could teach the physics of everything in great or sparse detail depending on the age group. Would you recommend this for all ages? If I were to teach my elementary students, would you recommend allowing them to build the gliders, or bringing in a few pre-built ones for them to fly before I go over the basic concepts of flight, motion, lift etc. with them?
Thanks for offering.

Hi Bill. I love the resources you share. My middle school kids are dying to do the foam glider activity. I printed the article out and gave it to a few of my second year Design and Engineering students for their review. I told them I wanted them to go through the article, try to visualize it, and then Tuesday next week, we will gather materials and have them be a test group to see how well they were able to build the glider from your directions.
Their next task then is to rewrite the directions in the areas where they were tripped up or found unclear. I’ve never seen a group of students more engaged in the actual process or reading an article and sharing suggestions and brainstormed ideas with one another.
I will ask them to write up formal feedback and provide their input here. What a great tool for students to read for meaning and purpose. I also love the idea they will be using the application process for solving a problem and finding a solution. I look forward to hearing how others did as well.

Wow! This is really cool! Thanks for sharing this. I'd like to say this will be a really great project for my students and my two sons, but who am I kidding, I want to make one for myself! The link gives very detailed instructions and pictures. Great post, it's amazing what you can make out of garbage.

Syringe Hydraulic Arm

This project is presented so well that anyone can do it. I love the steps shown with pictures and the materials are very easy to acquire. I can't wait to try it.
Thanks for providing this to all of us.  Adah

You are my hero Bill. This model is well done. I shared the article with my current Design and Engineering class, and of course they are begging to build it. Their comments included, “Wow! That looks so professional!” , “So, are you saying I can go to my local hardware store and buy the parts and make this for myself? Really?” , “Can I make one this year for extra credit?”

Bill Kuhl

Additional Resources

Foam Plate and Straw Gliders

Foam Jet II Foam Glider

Simple Glider Curriculum

Syringe Hydraulic Arm

Videos I Created

Pictures of ScienceGuyOrg Events 2012 - 3 minute video of the many activities that year

Fun With Foam Gliders - 9 minute video about inspiration and experiments with foam gliders

Tuesday, February 10, 2015

Flying Model Airplanes from Frozen Lake

Finding large open areas without trees is not easy where I live but one local lake provides a very large extremely flat area to fly from during the winter. Now if there was only an ice fishing shack available to wind the rubber motors when flying in the cold, it might be even more enjoyable. Yesterday the wind was light and I was off from work so I took the opportunity to fly from a frozen Lake Winona with two different rubber powered free flight model airplanes.

The larger of the airplanes is known as the Air Hare, this was a kit developed by two students over ten years ago as part of a program at the Eli Whitney Museum, and unfortunately I doubt it is available any longer. In 2002 I had a contest on my website to design an ideal beginner’s rubber powered model airplane. There were not many entries but all were very good designs. I built all of the airplanes and flew them both indoors and outdoors. Neil Dennis designed the first “Denny Dart” which has been a really popular beginners airplane that he sells kits for and gives away many.

Another airplane I flew is similar to the Blue Ridge Special that has been unavailable but might be available again. This small plane features a construction that makes the wing very rigid, whether that is needed in a small rubber model is questionable, the plane does seem to stay in trim better than most models this size however. Faster high-powered free flight needs this type of wing constructions to minimize flutter in the fast climb.

 I walked out on the ice that is solid enough to hold up trucks and wound the rubber motors in temperature that was just below freezing. The airplanes flew very well and the duration seemed comparable to what I saw in warmer weather but without actually having several timed flights from the different temperatures it is hard to know if the performance is less in cold weather. My comfort level was less with cold hands and after several flights on each plane I called it enough.

Related Articles

Bill Kuhl

Tuesday, February 3, 2015

Efficiency and Model Aviation

One of the things in life that really gets me excited is when something is efficient; that is the biggest reason I drive a hybrid car, and enjoy model airplanes that stay airborne with minimum power sources. In looking through definitions I found statements like this; “performing or functioning in the best possible manner with the least waste of resources or effort”.  Much of my flying are model airplanes that are powered by a strip of wound elastic rubber a power source that is easily wasted if not used in a resourceful manner.

Simple Rubber Powered Plane Climbing Outdoors

In starting with simple model gliders you can learn about the concept of “lift over drag” or L/D. Gary Hinze created an excellent tutorial for use with simple gliders that will teach concepts such as L/D that can be found on my website. There is another article about building simple gliders from foam plates and straws. To be efficient the airplane needs to produce the lift needed to support the airplane in flight with the least amount of drag. In level flight the lift only needs to be equal to the weight of the airplane, excess will cause the airplane to climb.  

Gliding from Tutorial

Lift Over Drag

For a longer glide it will be important to reduce the amount of drag as much as possible. Drag is created by the lifting surfaces of the airplane and also by air flowing across all the surface of the airplane. Using the correct airfoil and amount of angle to the wind in the wing will help reduce drag. Reducing the weight of the glider means less lift is needed to be created to oppose the weight of the airplane pulling it down to the earth by gravity; it does not change the L/D but does mean it will glide slower down the glide path.

Adding Power to Glider

Now we add thrust to the airplane in the form of a loop of twisted rubber strip. The challenge is to get the airplane to fly as long as possible on the limited number of turns twisted in the rubber.  With a thinner strip of rubber more turns can be wound in the rubber strip before it breaks. The thinner rubber will have less of a twisting force to spin the propeller that provides thrust to fly the airplane. Also related is the size of the propeller, a thin strip of rubber will spin a larger propeller at a slower speed providing less thrust, if the airplane is very lightweight the thrust will be sufficient to keep the airplane airborne for a very long time. Using a larger rubber strip will provide more thrust but use up the rubber turns faster especially with a smaller propeller.  Getting the optimum combination of rubber width and propeller size is part of the challenge in this type of model aviation.

Stop Watch Resting on Simple Rubber Powered Plane Which Flew 59 Seconds 

From a chart, the maximum turns in a loop of rubber 3/32” wide is 129 turns per inch while for 1/8” rubber strip it goes down to 97 turns per inch. For a rubber loop of 10” this would be 1290 turns for 3/32” and 970 turns for the 1/8” rubber. If the airplane was light enough to fly on the 3/32” the duration of the rubber motor run would be considerably longer. High duration indoor rubber powered free flight models are so light that a huge propeller can turn very slowly to power the model for very long flights. The longest flight ever was just over one hour.

Delicate F1D Model Flies for 30 Minutes Indoors

Adjusting the Flight Path

For a model airplane that is flying without control – free flight, the airplane must have some stability built in and be adjusted to gain altitude and then come down slowly as possible for maximum duration. If the flying is indoors the climb to the maximum height available (the ceiling of the building) should be rather slow but if outdoors reaching maximum altitude possible, quickly is normally the goal. Not only is greater height desired outdoors because it takes longer to come down to the ground but the higher altitude improves the chances of riding thermal air currents.

Powered outdoor free flight airplanes normally are adjusted to circle to the opposite direction of the torque which causes the airplane to circle to the left so the airplane is adjusted to the right. Indoor planes normally are adjusted to circle with the torque to the left.

Airplane in Stall Condition

Important for efficient flight in free flight airplanes is to keep the airplane from stalling in flight which is a loss of lift when the angle of attack is too great, usually after a stall the airplane dives and recovers and the cycle starts over again with a big negative affect on efficiency of the flight.  If the airplane is adjusted without enough climb and flies too fast that is generally not efficient for duration. Adjusting for the optimum flight path throughout a flight is a big part of the fun and challenge to free flight model airplanes.

No doubt I have oversimplified aspects of my explanation, I do hope people check out some of my resources and build some model airplanes.

Bill Kuhl

Important Concepts to the Efficiency of Flight for Free Flight Model Airplane

*  The airplane should fly through the air with just enough lift with a minimum amount of drag, many factors relate to this but important ones relate to size and shape of the wing.

*  Powering the airplane with elastic rubber strip it is important to match the parameters of the rubber motor and the propeller to power the airplane in an efficient flight path.

*  Adjustments to get the proper flight path and avoid stalls or dives are critical for maximum flight times.

Additional Resources  - Gary Hinze Tutorial

Additional Video That Might be Used in Float
Float Documentary Trailer an Upcoming Movie About F1D Indoor Model Airplanes