Thursday, July 31, 2014

Carpe Diem Paddle Club

Living in the Winona area provides many opportunities to see some great scenery and get some upper body workout exercise while floating quietly on water. Every Wednesday evening when the water hasn't changed from a liquid to a solid there is a group of people that meet to paddle kayak or canoe (had to get the science references in there).

Start of the Trip

Entering Backwater

Open Area in Backwater

This Wednesday we put in at the boat ramp in Fountain City Wisconsin for a wonderful evening of paddling, one of the longer routes we have taken providing two hours of solid paddling. The weather was perfect although a little hazy for good photography. This section of the Mississippi River has a relatively narrow main channel and a large amount of backwater area.  It is wise to go with someone that knows the backwaters or you can get lost for a time.  I don't think we were lost on this trip just took one turn that ended in a dead end.

Surrounded by Woods

Fawn was Spotted Along Shoreline

In the backwater the scenery is constantly changing; sometimes it is rather open, other times it is really narrow. The water was down to a more normal level while earlier this season it was at flood level. Often the water is only a few inches deep in the backwater and motorized boats would be stranded. There was only one spot on this trip that we were hitting the bottom with our boats requiring some pushing with our hands on the bottom for a few feet. In other places there are logs in the water or overhead that you must maneuver through.

Entering Narrow Path Single File

Path Through Aquatic Plants was Really Narrow

Getting Closer to Main Channel

We often spot various wildlife along the route. On this trip I saw a bald eagle up close, blue heron, and a fawn that was barely visible along the shoreline. In the fall of the year the near silence can be broken by duck hunters shooting, hopefully not at kayaks.

Boat Landing is Just Ahead

Bill Kuhl


* By using Google Earth someone computed our trips to cover about Seven miles.

Google Earth Image of Route We Took

Additional pictures from the potluck afterwards.

Tuesday, July 29, 2014

Herr Champ Update

There was an inquiry recently about how my Herr Engineering Champ was flying and if there were any pictures of it in flight. So far for me this plane has not flown very successful and in my opinion the airplane is just too heavy for the wing area. I had tried some test flights with 3/32” rubber and the plane would not climb at all, switching to 1/8” rubber the airplane would climb slowly but appeared to me always on the edge of a stall. Downthrust and nose weight were added which did help some, washout in the wings was recommended but that did not help much either. It was suggested that the airplane needed more power so I tried 3/6” wide rubber and now the plane was climbing easily but the number of turns in the rubber that could be used was reduced. If the airplane was not launched just right it would hit the ground harder and finally one wing half broke off.

Herr Engineering Champ

At this point I took my Guillow’s Super Cub out again to fly for a comparison; it flew much better like it always has. The climb is smooth with no hint of a stall, sometimes there is a slight wobble in the flight path. Extra dihedral was used on this airplane, maybe too much. After building a not very successful Guillow’s Cessna 180 I concentrated on building the Super Cub lighter, especially in the tail. No noseweight was needed for the Super Cub, total weight with rubber was 25 grams. With noseweight and heavier rubber in the Champ total weight was almost 22 grams.

Champ Wing Half on Top of Super Cub Wing

Some approximate math calculations were done to compare the wing loadings between the Champ and Super Cub. Wingspan of the Super Cub is 20” with a chord of 3” while Champ has 18” span with 2 ½” chord. Both planes have rounded wingtips but I used the area of rectangular wings and the calculated the wing loadings which showed that the Champ had a 16% greater wing loading. 

Super Cub Chased by a Gull

Someone with success with the Herr Champ had built to 14 grams total weight, at that weight I would expect the Champ to fly well. The design of the kit looks good like it should be light but the strips of wood felt heavy to me as I was building, I should have substituted some lighter wood. 

Bill Kuhl

Wednesday, July 23, 2014

What Can I Learn About Thermal Soaring from the Turkey Vulture

I have noticed that the turkey vulture which appear to be increasingly common in the Mississippi river valley city I live in are easily able to soar in thermal lift which late into the evening when it has been normally thought this lift is very weak. My thought is that with much observation and some research I might be able to improve my model soaring skills by learning from the turkey vulture. Comparing the aerodynamic specifications between the model gliders that I fly and other soaring birds would be where I would start.

Turkey Vulture in Flight

Turkey Vulture Soaring Over Water Which Normally Creates Little Thermal Lift 

The wingspan of turkey is close to 6 feet supporting a weight of around 4 pounds. Their wing is rather wide giving it a lot of wing area but it doesn’t create as much drag as a wing normally would because of the slots in the wing tips created by the feather arrangement. The Turkey vulture is more efficient at thermal soaring than the black vulture which might explain why black vultures are found in southern regions of US where thermal lift might be greater from warmer ground heating.

Notice Wing Tip Feathers

In an article on soaring on Stanford website it said that it had been determined that the minimum sink of the turkey vulture was only 2 feet per second. I then researched what minimum sink might be for a 2 meter radio control glider which is slightly longer in wingspan but would have a narrower chord. Weight varies for 2 meter gliders like does the weight of turkey vultures but I think half the weight of the turkey vulture would be common.  One person had determined that their electric 2-meter glider had a minimum sink of 3.2 feet per second but larger radio control gliders might only be 1 foot per second.  Small lightweight free flight gliders might have a minimum sink of only ½ feet per second.

Sport 2-meter Radio Control Glider

More Efficient RC Glider on Launch

It would appear to me that although the physical characteristics of the turkey vulture in regards to aerodynamics are good but many radio control sailplanes would be superior. The bird however has the ability to change its’ wings in many more ways than the variable camber changing available on the more sophisticated model sailplanes.      

Sometimes Many Turkey Vultures can be Seen Circling in a Thermal

The real question would appear to be how are soaring birds such as the turkey vulture are so good at finding the lift; on this there seems to be many opinions but not much that is a proven fact. It seems very likely the bird could feel when it was going up or down but people think the birds have senses that go beyond this such as detecting thermals with low frequency sound or smells from the ground.

Flying Lower

Flying Even Lower in Downtown

 Like model pilots, soaring birds seem very aware of other birds or even model planes going up in lift and will quickly fly over to join in flying in a spotted thermal. 

Some of My Thoughts from Watching Turkey Vultures Flying

* There would appear to be stronger thermal lift in the evening than many model flyers might realize. 

* Turkey Vultures are soaring in really overcast conditions which again might not appear to be good for thermal flying.

* I need to spend more time observing their flight patterns in thermals, sometimes they appear to change directions, is there a good reason for that? 

Update 7/28/2014

Cold front had moved in a Sunday with high winds but winds were lighter on Monday so I flew my Radian Pro after work. I just couldn't seem to find any lift to speak of except the two times I spotted turkey vultures over the field. Then the Radian was going up rather slowly but not coming down, the birds weren't climbing much either. We were all flying in the same area and height the second time, so much fun.

Please share your thoughts on turkey vultures or other soaring birds.

Bill Kuhl

Monday, July 21, 2014

College for Kids 2014 Recap

Another College for Kids class at Winona State University is now behind me and I feel some relief yet somewhat sad as well. Teaching this class gives me the greatest opportunity to observe the projects on my http://www. website being built by students grades 5 - 8 . For the next year I try to make the building experience go even better by fixing problem areas.  I can see that students like some challenge but if there is too much they give up.  I usually try a new project each year and drop a past project. This year after trying the difficult tumblewing the first day I brought in a very lightweight foam walkalong glider the second day and let students try this, they had better luck with this.

Foam Glider Surfing a Wave of Air 

On the second day the students built the rubber powered airplanes with a balsa stick fuselage. I spoke more about the design this year but still many of the planes did not fly that well. The kids really enjoyed the activity and it was their best opportunity to be creative. All of the other projects are kits that I make up, which is a huge job because there are only limited tools available that I supply. This means all of the sawing and drilling must be done beforehand. On the last day I had asked the students if they had ever done anything like this in school, none of them had.  That is completely understandable to me as to do this for several large classes would be darn near impossible in my opinion. In our small city there are not the science camps that are available in larger cities to build projects all year long which is part of why I see College for Kids vital to the community.

Ready to Launch Rubber Powered Planes

Plane in Flight

This year I tried to lecture a little more in depth before starting an activity. Maybe the students got something out of my short lecture but they are always so anxious to start working on their projects. I was impressed by the last day I saw no kids looking at cellphones or video games.  Some students took their projects home in the evening to work on them further.  Students and parents really were appreciative this year or at least they told me so, which is nice because it inspires me to try harder for the next year.

Gluing the Parts

Mousetrap Car Construction

From the pictures you might notice the lack of girls in the class. Not sure why that was as there have been girls in the past. Enrollment in the class was also down from several years ago when there were parents begging to have their child put on a waiting list in case there was a cancellation.  I see the needed for this type class increasingly important. It was great to see that a class in model solar cars was offered this year an activity that I have included in past years. With all the emphasis on STEM, I still think it is wonderful that Winona State University offers a program with more variety.

Syringe Hydraulic Arms Construction

Happy Students

Bill Kuhl

Be sure to check out Winona State College for Kids on Facebook

Pictures in this blog post are from that source.

Build Articles for Projects in Class Engineering Through Models:

Syringe Hydraulic Arm Article

Rubber Powered Foam Airplanes

Mousetrap Car Construction Article

In the Twin Cities Area of Minnesota Project Building Goes on All Year Long Through:

Bakken Museum
Leonardso's Basement
The Works

Tuesday, July 15, 2014

Trying to Learn Tumblewing Not Easy

Each year that I teach my College for Kids class “Engineering Through Models” I try to test out some new activity while dropping some activity done in the past. Sometimes the activity looks promising with some tweaking for the next year and other years I drop the activity.

Successful Tumblewing Flying

This year I tried to introduce the “tumblewing” walk along activity. It is very inexpensive, quick to build, and lots of fun when it works properly. It does however take some fine adjustments and mastery of the technique to make it work properly. With many years of experience adjusting model airplanes it took me some effort to get a tumblewing flying successfully for any length of time. 

Proper Way to Launch

The tumblewing is just a piece of lightweight paper cut in a rectangular shape with the edges bent up in a manner that it will spin around a horizontal axis. You launch it to start the spin and then approach with large flat piece of material such as cardboard or foamboard and push a wave of air to keep the tumble wing spinning in the wave of air only a few inches away from the board. 

FPG9 Glider Works Well For Almost Everyone - I Start With This

To make this work the tumble wing needs to be bent properly, you have to launch it so it is spinning, and then you need to approach with the board just so as not create too much turbulence yet maintain the wave of air needed to keep it flying. At this point you need to adjust your walking speed and tilt the board to control the direction.  

Cutting Out FPG-9 Gliders

One student was getting the idea but most just could not make it work, became frustrated, and quit. I was not able to help them fast enough to head off the frustration. It was a good lesson to me that even though I can do an activity, being able to teach it effectively is much more difficult.  I need a better idea of what is not correct and how to fix it. 

Being able to master a difficult task through a process of figuring out what needs to be corrected and then making the small corrections is one of the most useful skills that I can think of.  Any form of model aviation no doubt will require this to master. I plan to bring in a couple of very lightweight foam walkalong gliders today to give the students a chance to try to have some success. I plan to have them try it one at a time so I might be able to offer individual assistance.

Bill Kuhl


Walkalong Glider and Foam Store - many options available to purchase foam or gliders even RTF proceeds go to The Physics Factory 

Science Toymaker Website - Slater Harrison

Walkalong Gliders Book - Phil Rossoni   

Darcy Whyte - Inventor/Artist has done much with walkalong gliders

Related Blog Posts

Walkalong Gliders and Indoor Flying

Thermal Soaring a Walkalong Glider

Update from 7/15/2014

Students did much better with foam gliders made from very thin foam.

This glider sent to me by Slater Harrison is so light you can walk at a crawl speed to keep it flying.

Thursday, July 10, 2014

Almost Lost Model Airplane Story

Yesterday looked to be a very good day for model glider flying although slightly gusty at times. Cool morning nicely warming up with many large cumulus clouds looked like there would be some good thermal lift. As soon as I got home from work I grabbed my UMX Radian radio controlled electric glider, a tip-launch free flight glider, and a hand launch free flight glider for some flying. I flew the RC glider first and climbed easily many times in thermals but at times I needed to use electric to come back against the wind.

Looking Across the Pond

Glider Spotted in Zoomed Picture

After probably 30 minutes of the radio control flying I thought I would try one of the free flight gliders, I did not want to risk TLG glider in the wind when there was a small pond downwind. So I made a couple of easy throws with the Maxwell free flight glider and then a gust of wind took it towards the pond. Oh darn, I tried to watch it as close as I could to see where it landed.  There are steep banks around the small pond and monster weeds. When I got to the edge I looked out first in the water hoping I wouldn’t see it floating in the middle and then looked through the weeds at the near edge.

Looking Back and the Jungle to Walk Through

On the other side of the pond I thought I spotted something at the edge that looked like it might be my glider but really couldn’t tell. So I thought I would use the available technology and took a picture with my cellphone camera while zoomed to the max. Looking at the blurry picture I could tell that it was indeed my glider. So I proceeded to trek around the pond and through the jungle of weeds to get down to the edge of the water. I was really careful to check the ground ahead of me when approaching after falling into trout streams a couple of times because I could not tell what I was stepping into. 

Glider Returned

Wet Shoe

I had the picture to look at now to get some reference of where the plane was in regards to the opposite shoreline. Also found a small dead branch that I could use to try to lift the glider from the water, I still had good clothes on and really didn’t want to get wet. Turns out I only got one leg slightly wet and retrieved the glider. Glider looked fine except for some dirt on the stabilizer. 

After this ordeal I had the sense to stop flying for the evening. 

Bill Kuhl

Lost Model - What Can I Learn

Tuesday, July 8, 2014

Science Guy at Stewartville Summerfest 2014

It was another perfect day this year as was last year for the 4th of July celebration – Summerfest in Stewartville Minnesota. This year my table was located closer to the major activities and I had a steady stream of people, mainly children throughout the day.  I try to bring a sample of the projects found on my website; mousetrap car, model wind turbine, syringe hydraulic arm, simple electric motor, model solar cars, and some foam model airplanes. This year I also had the syringe hydraulic mechanical advantage demonstration device and the kit I built of the Leonardo Da Vinci Aerial Screw. Being on top of a hill I could launch model gliders down the hill and they flew a really long distance which impressed most people.

When I arrive I try to arrange everything somewhat neat but it doesn’t take long and it looks really messy because either I am demonstrating or the kids are operating the projects.  It seems for almost every group of kids and/or parents I have to explain what each project is.  I don’t mind that at all because at least it shows some level of interest.  Some parents have their kids guess what the projects are and then expand on how each project works.  At one time there was a grandfather, father, and daughter looking at my projects when a reporter from the local newspaper came by. 

Someone asked me if there were any more 4th small town celebrations in the area, they said Summerfest was wonderful as it was so typical small town USA.  I would have to agree; running race; fishing contest, kid’s rides, pedal tractor pull, craft vendors, live music, and food.  Later in the day there is a parade and fireworks.

Bill Kuhl