Wednesday, December 7, 2016

Sky Demon e20 Build Report

My interest in the e20 electric free flight event came about mainly because I am looking for free flight models that will fly from smaller flying sites. With electronic DT (dethermalizer) it is possible to accurately set the time that the DT will actuate. I have flown my e36 free flights from pretty small fields by setting the DT time to be short. It was my thought also that a model that only weighs around 30 grams will survive some pretty hard landings without damage.

BMJR Sky Demon

Before selecting an airplane I purchased the electric components from Bob Selman at BSD Micro, I knew of Bob from his tiny micro RC components and our mutual friend Floy Richards who passed away several years ago. I purchased a 2.5 gram unit that controls the motor run length and the DT time, the actuator for DT is a tiny servo that moves in one direction. I built a small pivot arm that one end goes under the servo rod that moves and the other end connects to DT line.  With my purchase I also selected the programming box, a Parkzone motor, a propeller, and one battery.  From flying tiny RTF RC planes I have many chargers.

BSD Micro Motot/DT Unit

BSD Micro Programmer

For my first e20 airplane I decided I would build a balsa kit airplane and selected the Sky Demon from BMJR.  This plane looks like it could be a tiny RC plane because it has a full width fuselage; my thought was if I got tired of flying it as an e20 I could install tiny RC gear in the plane. I installed  the motor/DT unit on the outside of the plane with a couple of screws so it could be easily removed.

Motor, Propeller and Battery

EZE Dope

Building the Sky Demon was easy although some of the pieces were rather small and I had to use a tweezers to place them. I covered with Esaki tissue but tried a new to me product EZE Dope to seal the tissue, it doesn’t give off the odor that clear dope I normally use. It did pull the wingtips up when it tightened up giving them washout that I thought might be a good thing. The plane has a left turn under power and glide so I think one wingtip has too much washout.

Sky Demon in Flight
Sky Demon DT in Progress

Last weekend the wind was rather low although it was only 32 degrees F but I decided that was warm enough for test flights. The motor run was set to only 4 seconds and the DT was rather short but long enough to observe the glide. After launch the plane wanted to climb rather steep and to the left, so I launched banked to the right. The firewall of the motor was taped on so I could adjust it later, since then I gave it more downthrust and some right thrust.

Wing and Stab

Stringers in Rear Rather Small

Many flights were made; I am guessing probably around 15 although all were rather short. The plane appeared to fly in a stable manner although the transition from power to glide was not perfect. This will give me something to work on when I fly it again. The DT worked perfectly in those flights although sometimes it was only a couple of feet above the ground on DT.

DT Stab

I am providing the link to NFFS provisional rules for e20. Basically the airplane is limited to 20” wingspan, direct drive brushed motor and 30 grams minimum weight. My airplane weight slightly over 31 grams which I thought was good for a first build.      page 10 E20 Provisional Rules
Bill Kuhl

Related Links  - Sky Demon kit on BMJR website   2.5 gram Motor/DT unit  Programming Box  About Floyd Richards  EZE Dope Video

20 Second Video of Timer / DT

Friday, December 2, 2016

Building the Retro Gnome FF Hi-start Glider

How I decided to build the Retro Gnome hi-start free flight glider has a rather round about history. As my interest in free flight models has increased so has my desire to experiment with different aspects of free flight, in this case it was dethermalizers (DT).  My start with DT’s was with the viscous type which although lightweight, suffers from accuracy issues especially as the temperature changes. I had used the plastic clock windup mechanism that I purchased from Hank Nystrom in water rockets to deploy the parachute and it had worked well. Normally this mechanism runs through rather fast but it is possible to slow it down by putting very small weights on part of the mechanism that vibrate quickly and slow down the unwinding. Some people build their timers like this but I purchased the Micro DT from Hank.

Retro Gnome Farmework

Small Weights on Plastic Clock

To test out the Micro DT I decided I would install it in the free flight hi-start glider that Hank had shown on his website with the timer, the Retro Gnome sold by Retro RC.  I met Mark Freeland (Retro RC) at the 2016 Nats and he showed me a sample of the glider. 

Kit Components

Building the kit is relatively easy as it is laser-cut and there is an instruction manual, in some places the plans and pictures are a little small so I used a magnifying  glass, not going to say I am getting old. The wing seemed like it was not very rigid before covering so I used a technique Dohrman Crawford uses of using some reinforcing tissue strips over the structure before covering with tissue. The finished wing feels plenty rigid.

Wing Structure Before Joining

Fuselage and Stab

This glider uses a simple autorudder that  is pulled to the right by a small rubber band and to the left by a monofilament  line with a pin holding the tension until the pin is pulled out as the tow hook releases and the tow line pulls the pin out. As this is a hi-start glider a very thin rubber strip and line with a small flag make up the hi-start launching system, I purchased this from Retro RC also.

Kit and Launcher

My hope is to do some glide testing of the Retro Gnome this weekend and take additional pictures but no hi-start launches. The glider must be adjusted so that it goes up on tow straight, when the pin releases it should turn right because of the autorudder.  The design includes adjustment screws for rudder movement, stab incidence change, stab tilt, and a tow hook that can be positioned in multiple  locations.

Almost Complete

Stay tuned for future flight reports.

Bill Kuhl

Related Links

Friday, November 18, 2016

Model Airplane Building in Full Swing

Although it has been warm enough to fly model airplanes outdoors so far, the daylight hours have dwindled until it is getting dark just as I leave work.  My evenings are now spent building model airplanes for next flying season although last year I flew some outdoors all winter long.  For next year I am building a variety of competition outdoor free flight model airplanes. 

Wilbur NOS Rubber Model

Selecting models that introduce me to new building techniques that I have not yet tried in previous models makes the build even more interesting, or I might try a new covering type that I have not used before. After going to the 2016 Free Flight Nats and meeting Jim O’Reilly I decided I wanted to build a nostalgia rubber powered model. Jim gave me some recommendations and I settled on the Wilbur rubber model that was designed in the 50’s. This introduced me to a type of fuselage construction where the fuselage was constructed almost entirely of angled strips of balsa. It was a fair amount of work but the fuselage is amazingly rigid.

Polecat X Wing


In the 2016 flying season I flew a beginners P30 model the NJAPF at the Nats and two smaller contests, it worked well for me but it is not considered a super high-performance model. I had previously had purchased plans and rib kit for the Polecat X P30 designed by Don DeLoach so decided to build that model for next contest season. This model introduced me to carbon capped ribs and building a rolled balsa fuselage, I have not attempted the fuselage yet. I plan to cover the model with ¼ mil Mylar covering which will be new to me.

Retro Gnome

Texas Timer Micro DT

Sky Demon E20

Ready for covering is a Retro Gnome free flight hi-start glider, the building techniques are not really new to me but I have to setup the auto rudder function. Auto rudder keeps the glider going straight on tow but when tow line releases the rudder moves enough to cause the glider to fly in a circle. I am also using the Texas Timers Micro DT for the first time. This is a mechanical timer which should be more accurate than the viscus and fuse DT’s.  I am also building a Sky Demon e20 model with conventional construction but will use an electronic timer/DT from BSD Micro that I have not worked with before.

Recently I have had some pictures and writing published in model aviation magazines. A couple of mentions in Aeromodeller Magazine published in the UK, the latest issue mentioned my Fantastic Foam Flyer simple rubber powered model and the after school program created by teacher Jon Kemm in the UK. Ronnie Espolt who lives on the US west coast and works with the foam airplanes also was mentioned. Pictures I had taken of 2016 Nats were in NFFS Digest and my description of the Nats was published in November 2016 Model Aviation Magazine. My hope is that getting the name of people that are promoting model aviation for young people and I into media will create more awareness to what we are trying to accomplish.

Bill Kuhl

Related Weblinks    - Wilbur   - Polecat X   - Retro Gnome  Texas Timers Micro DT  - BSD Micro electronic timer/dt for E20 - Sky Demon e20  - Aeromodeller Magazine  - Model Aviation Magazine - Jon Kemm  - Fantastic Foam Flyer

Monday, November 7, 2016

The Enjoyment from Fast Free Flight

This past year I spent a major amount of my model aviation time learning with competition free flight model airplanes. I still fly RC sailplanes both thermal and slope with some sport electric RC as well. My point in mentioning this is I have a fair amount of experience building and adjusting model airplanes, yet not the complete skill set for fast free flight airplanes. Adjusting the flight of the Pearl e202 E36 model has been much more challenging than the NJAPF P30 rubber model I fly. With my P30 model there has not been a single crash that I can remember, the only adjustments are with the climb and circle amounts.

Pearl E202 E36

P30 Rubber Model Easier to Trim

In previous articles I have mentioned some of the challenges I have had with my e36 model, it has crashed several times but I have been able to repair it fairly quickly. Carbon fiber reinforcement has been added in several places, I think I would do this on a new build. I thought I had the plane adjusted pretty well but this past Saturday the plane started turning to the left on launch in the climb, luckily I used a really short DT, it saved the airplane. I gave it what I thought was a very small amount of right rudder trim but it curved to the right after launch and hit the ground.

Damaged Model

The front of the pylon was smashed like it has been several times before but worse was one wingtip that was broken in many places underneath the covering. I collected the pieces and started the repair job but spent much of the afternoon flying RC gliders. The repairs were finished that evening but I also noticed the dihedral joint in the opposite wingtip was flexing easy. Now I do not know if it happened in the crash but my theory is this issue has been present and causing the model to be out of trim. I should have inspected the model before when I noticed a change in the flight pattern. My excuse was the colder temperatures I was flying it in.  There was nothing visible that you could see to spot the problem but putting any force on the joint it would be obvious.


Flying Again 
I got out early the next morning for test flights before there was any wind. As Hank Nystrom had reminded me, I started with the shortest motor run and quickest DT. That looked good but it was really short, increased the motor run a little more and still looking good. Next I gave the DT just a little more time so I could see the transition; that looked good. Just a little longer DT as I was flying from a small flying site, it looked really good with no stall between power and glide. I was elated and it gave me back some confidence that I was again making progress.

Flying From Farm Land but Trees on Edge

For me the enjoyment in free flight models with a fast climb rate comes from the more challenging aspects adjusting the model and building it correctly to start with. It forces you to really observe the model closely when flying and theorize how it might be improved. When you watch so many power models fly at a contest it looks way too easy because you do not realize the time and effort the experienced modelers put into getting their models to fly so well.

Bill Kuhl

Related Articles

Vendor Websites

Thursday, October 27, 2016

Making Progress in E36

I remember reading the book by Frank Zaic, “Circular Airflow” not really understanding it but amused by his struggles designing a glow powered free flight that would not loop or crash after launch. It really is amazing to me that a free flight airplane can climb so quickly under power and transition smoothly to a slow glide, but not always. My first attempts at a fairly fast powered free flight were when I installed the electric power system I had purchased from Texas Timers for e36 class in an old ½ A glow powered Starduster.  The balance was guessed at and tweaked from test glides but the airplane flew pretty well although I did not build this model.

Pearl E202 at North Branch

The intended model for the electric components was the very popular Pearl e202. As locally I had a very small flying site I added rudder control RC to the model for the first flights. With my inexperience I did not have the stab incidence adjusted correctly and managed to crash the airplane even with the ability to steer it. With enough incidence it flew fine but I needed to fly it as a free flight model. Just before going to the 2016 Free Flight Nats in Muncie Indiana I removed the RC gear thinking I would have plenty of room to fly and many people to help me.  I did have the room and help but a recurring problem was that the plane had a tendency to dive to the right after the top of the climb. 

Lots of Help at 2016 Nats

After returning to Minnesota I flew the plane before two contests near North Branch Minnesota. At the first contest there were some less than perfect power patterns that barely avoid crashing. For the second contest I launched to the left which should not work but it did for some strange reason. The plane was launched to the left for many flights but on occasion there was a small stall on top of the climb. A couple of weeks ago I was flying the Pearl from some farm land and I noticed a crack in the stabilizer leading edge, the trailing edge was warped also.  More flights launching to the left were made after the repairs but then I thought I will try launching to the right with a short DT. That looked pretty good with no dive. Awhile back the plane came down so fast launching to the right that the wing folded in half as it DT’ed just before hitting the ground. I tried more launches to the right and the transition was great.   DT dethermalizer a method for bringing airplane down from thermal air current. 

Wing Folded on DT after Dive

DT over Farm Land

I sure hope I have permanently found and corrected the dive to the right issue. Most everyone with EXPERIENCE have told me launching to the left is going to cause a crash. For me there is no reason to try to prove them wrong. Hopefully I can have many more great flights launching the airplane the way it should work.  E36 is really fun and I will be building a different model a Starduster E36 which should launch to the left because of the high thrustline.

Bill Kuhl

Related Articles

Vendor Websites

Friday, October 21, 2016

Testing New Dethermalizers

As I am advancing from building and flying free flight model airplanes purely for the fun of watching the models fly to flying in competition, I am trying to find out what works for me.  This includes improving my building skills and the products used in completing the models. Recent blog articles have been about the Gizmo Geezer propeller system but I have also been experimenting with dethermalizer systems trying both old and new technology. 

BSD DT Only Electronic DT

In addition to bringing the plane down from a thermal, because of the small flying sites I fly from at times the DT is used to terminate the flight before the airplane flies off the field into a tree. The first DT’s I used were viscous timers on discus launched gliders, for short flights I was able to control it fairly accurately.  When I installed a viscous timer on a P30 model that was making longer flights I found that a lot of adjusting needed to be done to get over 2 minutes before the DT released. It is not just a matter of winding the dt farther as that puts more tension on the spring resulting in the DT running faster. By a lot of trial and error with adjusting spring tension I could get 2 minute DT time but not that accurately.

Fuse DT Guillow's Lancer

From the free flight contests I have entered this year, it is apparent the use of a burning fuse is very prevalent. It is light and relatively inexpensive; with some experimenting it might be fairly accurate. To get some idea how long the fuse would burn for a given length I did some tests burning the fuse hanging out of a tube with a rubber band at the edge of the tube, like how the snuffer tube would work in an airplane. I timed the burn times and found it fairly predictable, so I modified a rubber model I have been flying the Guillow’s Lancer to use a fuse to release the front of the wing bringing the airplane quickly. Some short test flights with the Lancer and the fuse DT looked promising.

E36 in Flight

After using the Texas Timers electronic DT in my e36 model, electronic DT seemed like the ultimate solution. At the Nats and one of the local contests I talked to people using an electric band burner DT on rubber powered models. I ordered one from Starlink for the Wilbur old time rubber model I am building. BSD Micro sells some really lightweight electronic timers that I wanted to try so I ordered one for the E20 event which controls the motor and has a tiny built-in servo to DT the model. There is a rotary dial programmer box available to set the times so I ordered that as well.  In addition I ordered the DT Only unit to try on rubber powered models; this unit only weighs 1.5 grams without 

Starlink Band Burner DT

Charger for Band Burner

BSD Micro E20 DT
Programmer for E20

DT Only

Watch for additional blog posts as I install and the test the various DT methods. I also have the Texas Timers - Micro DT that I will be installing in a hi-start glider.

Bill Kuhl

Vendors Related to this Article  BSD Micro RC  - E20 and DT Only  Gizmo Geezer – rubber propeller systems  Guillow’s  - Lancer sport rubber model Wilbur rubber model Discus Glider with Built-in DT  - E36 Pearl e202  Starlink Flitetech – band burner  Texas Timers – electronic system for e36

Related Articles

Thursday, October 13, 2016

Flying With the Gizmo Geezer

This past weekend I had the chance to fly my NJAPF P30 rubber power model with the Gizmo Geezer installed on a large field in a contest. It worked well with the exception that apparently I didn’t have the shielded sleeve connected properly and it came loose right after winding. The rubber retracted in a hurry back to the rear peg. Luckily damage to the fuselage was just some ripped tissue and I continued to fly the airplane.  I am worried about losing the winding attachment and need to connect it permanently to the blast tube wire.

My P30 using Gizmo Geezer Propeller

Covering Ripped When Connector Came Loose

Inside the Blast Tube
The airplane climbed out well although other P30 models were greater performance designs with rolled tube fuselages. Just the same it placed about halfway in the standings, with one flight the timer lost sight of my plane just as it made a max. I notice Clint Brooks includes the Gizmo Geezer in his Monarch and Boomer Mk III P30 model kits.  I also noticed many of the scale models at the 2016 Nats in Muncie Indiana had Gizmo Geezer propellers.

Gadfly with Gizmo Geezer

Nose Block Sold by Volare Products

I had emailed George Bredehoft of Volare Products
 with a couple questions about the Gizmo Geezer and the nose blocks he sells, I had purchased the generic one but he has special nose blocks to fit certain airplanes. The main purpose of the nose blocks is to get the perfect fit for the nose button which has three bumps sticking out of the round hole. George sells just the Gizmo Geezer nose buttons because some customers want just the ability to easily adjust thrust angles. 

Gizmo Geezer is located in Canada and the company consists of Orville Olm and Marcy Green. There is a lot of information on their website, a good place to start is at the sitemap.

Nose Might Come Out on Landing
Nose Stays on in Glide

As far as testing out the desirable features so far the nose has always remained inside the fuselage of my plane without the rubber band fastener I had over the nose before installing the Gizmo Geezer. Many times the nose will pop out when the plane hits the ground. I have not had a need yet to try adjusting the thrust line.  As far as I can tell the rubber unwinds smoothly and the propeller free wheels easily.

I have more Gizmo Geezer propellers on order.

10-24-2016 Update

Spinner Model

Received another 9.5" propeller with the spinner and also 7" propeller.

Bill Kuhl

Related Articles

Gizmo Geezer Review Part 1

Oktoberflug Free Flight Contest