Learning From Model Aviation & New Challenges

I was really overwhelmed by the number views (700) to my last blog post about my Wilbur rubber model, the repair was finished and I flew the plane last weekend. I covered the center section with ¼ mil Mylar with tissue over top; this kept the tissue tight in really humid conditions.

Dewey Bird Control Line

Wilbur Flying in the Fog

After the Free Flight Nats was over I wanted to try control line flying again, last fall I was flying an electric powered control line that worked well after initial problems. This year it flew fine but I have been hesitant to try any stunting other than wingovers because it seems rather fragile. So last winter I had ordered a simple ½ A glow powered control line the Sig Dewey Bird. Construction went well but then I was hesitant to install blind nuts because of the challenge it has been for me in the past. This time it went worse in that I got epoxy inside of the threaded area and twisted off a bolt. I tried drilling out the bolt but my drill bit barely scratched the surface. I started asking questions to a free flight listserve group and I received a lot of good suggestions although most were what to do before I twisted the bolt off, like heating the epoxy or plugging the hole before the epoxy. At the local hardware store I bought a cobalt drill bit which did drill through the metal and I tapped it for 2-56. 

Piston and Cylinder Cox Baby Bee .049

Someone gave me a Cox Baby Bee .049 that would not turn over with a rather large wood propeller. I figured the propeller over heated the engine but in asking questions I found out that people run even larger propellers on reed valve Cox .049 engines in the Texaco event. When I took the engine apart the bottom of the piston that connects to the connecting rod looked like it exploded. From my stash of old engine parts I found another piston and pushed out the old one. After putting the engine back together it ran great after a short time, it will be used in the Dewey Bird. With my electric control line I added tip weight that I never put in, it really helped the tension on the line; for the Dewey Bird I used a nickel for tip weight. 

Assembled Sofa

Model Kit Instructions

Furniture Assembly Instructions

A couple of weeks ago I helped a friend assemble some furniture, it went pretty well for me but I have to believe that having built model airplanes was a real help. I have lots of experience reading directions and diagrams with model airplanes. With so much purchased online being able to assemble anything can save a lot of money compared to paying someone to do it. I found this quote from Business Insider about “spatial reasoning ability” interesting:

 https://www.businessinsider.com/spatial-ability-predicts-future-success-2013-7

 “It's no surprise that high verbal and math SAT scores at a young age might predict future success, but when you add a test for spatial reasoning ability to the mix, you get an even better predictor of someone's future accomplishments, creativity, and innovative potential, a recent study found.” 

G-12 Catapult Glider

This week I finished up building the G-12 catapult free flight glider which will be used in Dick Bertrand’s Free Flight Rescue Program. It went together really well as most parts are designed to lock together. In doing some hand launches with the glider it appeared to be really stable. Look for more to come about this glider. 


Bill Kuhl 
http://www.ideas-inpire.com

Related Links

http://scienceguyorg.blogspot.com/2017/11/adventures-in-electric-control-line.html Electric U-control

Repairing Wilbur Wing Learning Experience

In working with my contest free flight models I seem to have reinforced what I might have read about but did not act on become an issue. Let me explain, I have read that to build a competitive balsa free flight model wood selection is important, heavier wood is needed in places where strength is really important, while other parts of the model can utilize lighter wood. Hoping to build lighter models for short kit models I have order lighter density balsa for the balsa needed to finish the model.

Embryo Model Wrinkles from Too Light of Wood

My first big struggle with using too light of wood came when I used too light wood for the longerons in the fuselage of an embryo model. After breaking the fuselage during construction, I could not get the model covered without sags and wrinkles either. More recently I had the wing fold in my Wilbur old time rubber model just after launch. In asking online what normally causes this, everyone told me using too light of balsa for wing spars.  The structure for the wing is minimal on this model so I can see the importance of adequate strength in the spars. 

Wing Folded

Inspecting the Damage

Replacement Spars

To find heavier wood, I purchased several strips from local hobby shop. I weighed the strips and used an online balsa density calculator. This wood was really heavy. The lighter of the 1/8” square strip was almost 13 pound balsa and other strips were over 20 pound per square inch, the lightest strip was used. 

Really Heavy Wood

Not as Heavy

In doing the repair instead of splicing pieces I removed all the covering from the center section and replaced the two spars all the way to the wing panels. Using acetone on the Duco glue joints the broken spars were easily removed. My experience has been that when I splice balsa with another piece doubling it most likely there will be a break in the balsa right next to where the balsa has been doubled. Maybe on a larger piece splicing at an angle would work satisfactorily. I am also repairing a Witch Hawk 500 wing and went a fair distance back from the breaks in replacing with new spars.

Replaced Spars

1/4 mil Mylar Before Tissue

With tissue covering there is also the issue of the covering sagging in times of higher moisture like early morning flying. No doubt the model takes on more weight and the tension tight tissue gives the model structure is less. To help combat this problem in the center I am covering the center with ¼ mil mylar and then covering with tissue over that.

Update 8-25-2018

I finished up covering the center section mylar and tissue then made some flights in really humid conditions. The center section remained tight, tip sections and stab sagged. Someone mentioned the tissue is still taking on water weight.

Bill Kuhl
http://www.ideas-inspire.com

Balsa Density Calculator Link

http://www.nclra.org/Programs/BalsaDensity.php

Flight Video

MMAC Contest & Model Trim

Why do some planes fly pretty consistent day after day while others seem to vary? I thought using a covering that changes a great deal with humidity was the major part of it but it seems there is more to it than that. I have to believe the aerodynamics of some planes results in a plane that has greater stability and the plane is a little more tolerant in slight variations in the trim. I know wood changes with weather conditions and I would assume plastic does to a smaller extent. Many years ago when I first started flying radio control glow planes I remember people warning about the plastic pushrods and how they would change with temperature. The speed of the aircraft multiplies the trim issues. 

Streak Landed on Sandy Road

As I build new planes I go to the extra effort to build in screw adjustments for rudder and stabilizer. I find that I am making small adjustments on different days; it is not just get one trim adjustment and leave it forever. Sometimes it seems the trim changes throughout the day. 

My goal with my competition free flight models has been just to get consistent flights so I can get as much experience as possible without breaking it. After three years I am starting to think more about the performance. Recently I have been working with ½ A Streak glow model. Throughout the first several flying sessions I worked getting a consistent climb and transition. Some of the short first flights were rather nerve racking, on a couple of occasions the plane did a loop after launch, one time it pulled out just as it hit the ground.

Dave B at North Branch

With a washin wedge on inside right panel and tiny amount of right rudder some of the time, the power pattern is good and the plane transitions well. The issue now is it comes down too darn fast, at first I thought I was just launching into bad air but that cannot be the case on every flight. My theory now is the plane is just too heavy; it weighs 6 ounces while other people have built the plane to slightly less than 5 ounces. My Basic Yeller Pee Wee 30 model which has slightly less wing area weighs much less than 4 ounces; a big difference. 

Wilbur Folded Wing

At the last contest I attended near North Branch Minnesota on my second official flight of my Wilbur rubber model the wing folded right after launch. Between the test flight, the first official flight I had added a larger number of turns to the rubber but less than I have used in the past. The wing structure is minimal so I will try to strengthen it without adding too much weight. Even with a big boxy fuselage this model glides pretty well.

More Dramatic Wing Folding

Flew discus launch glider and catapult in the contest as well, with the discus I was getting good altitude compare to others but just couldn’t seem to get the glider in a thermal it could stay with. My catapult glider that I struggled with and broke so many times is now flying consistent.

For a small contest there were several people flying towline glider, as it had gotten windy I did not attempt to fly my Jetstream towline. If you had a good flight there was a good chance it could land in a tree.

Bill Kuhl

Nats Concluded - Finally a Winner

At least one person remarked I packed a lot of airplanes in my small car; I flew most of them but not all in competition. My Jetstream towline glider I never took out of the car. I flew my Wilbur rubber model just for fun but ran out of time to fly it Friday in competition. Friday I had too many events; P30 rubber, PeeWee 30 gas, hi-start glider, classic towline and OT Stick rubber. The last two I never flew, there was about an hour left Friday afternoon and that is not enough time if you are walking. Tuesday evening I ran the E20 event for Bob Stalick but did not fly. Taking pictures, video, and recording scores kept me plenty busy. I had created a scoring spreadsheet for my tablet which worked fine but it is hard to see a screen in sunlight.

Basic Yeller Pee Wee 30

E20 Event Tuesday Evening

Friday morning started with very little wind, I wanted to fly my Polecat X p30 model first because it uses a long 3/32” rubber motor that runs a long time but climbs slowly, good for calm conditions. I had test flown it the day before and a strand of rubber broke, so I replaced the motor. The first contest flight I wound to 1200 turns and the plane barely flew. I tried winding to 1550 turns and the motor broke every strand in the rear. To speed up things I tried tying the strands together, it broke in front this time. New motor from same batch of rubber I carefully wound to 1500 turns.

Polecat X P30

I launch the model and it was stalling like crazy and came down, one attempt. In my stress to get in another flight I put a shim on the rear of the stab instead of the front. It stalls even worse, another attempt. Fix the shim and wind the motor to 1500 turns and the plane is flying better but bouncing around in the wind that is increasing. My last flight took it across the field almost to the camp ground but the duration was short of a max. It just seems to me the previous batch of rubber I used in the plane worked better.

Wilbur Rubber Model

On to my next event PeeWee 30, my Basic Yeller has had many flights just for fun but never flown in competition. The first launch it had a little too much right and not enough rpm and hit the ground breaking the pylon. I glued that up and flew two hand launched flights that were around a minute long. For the last flight I had the motor adjusted better which it needed because the last flight was the ROG flight. I was afraid it might hit a tree going into the wind but it turned back and provided another long walk down the field.  There were 6 people signed up for the event and only 3 flew. I won my first trophy at the Nats and it was for first place. Having my name called in award ceremony for the first time in three years was nice.

Retro Gnome Hi-start Glider

Models Brought to Nats

The last event I flew was not an official event but fun just the same, hi-start glider. One evening I had flown the Retro Gnome glider I had built a couple of years ago using 1/16” rubber on the hi-start instead of 1/8” rubber which is really too much. With the thinner rubber the glider appears to adjust the flight path to straight better than when it launches too fast. Flying in the contest it was gusty but my glider launched without crashing every time. The last flight I think I stretched the rubber a little too much and the glider had a little trouble releasing. One flight resulted in a rather long chase but duration was not great in any of the flights. I was just happy how well it launches.

2018 Sympo

This concludes comments on my trip to the 2018 Free Flight Nats, it sure was a great time that went too fast. I really would have liked to have been more social but it was great getting so much flying in. The 2018 NFFS Sympo was for sale at the Nats, I have two articles in this issue. One is on recruiting kids to free flight and the other is on viscous DT timers.

Bill Kuhl

Nats 2018 Adventures II

Monday morning early there was barely any wind and I thought I could no longer put off flying the Witch Hawk 500 I had built, having completed it not long before the Nats. This was my first larger glow powered free flight with 60” wingspan powered by an old K&B .19 Greenhead. I was really nervous to fly the model but then I didn’t build it to hang from ceiling. This was the first time using bladder pressure and using an electric starter strapped to a stand. If there wasn’t so much equipment needed I would have flown it far from the flightline. 

I Had a Before Picture Taken

First Flight

First short flight it climbs completely straight and stalls. The wing pops off but only damage was a broken propeller. Adjusted the rudder a tiny amount to the right, next flight it climbs slightly right and transitions great. With no wind to drift it the glide circle was going right over the cars and people. I was so afraid it would hit a car but instead it hit a golf cart breaking the wing in half, worse than that it broke the Texas Timers Max IIIa timer. I have the wing almost repaired except for covering.

Super Pearl E-202

Wednesday was the E36 event and I flew the first e36 I built the Super Pearl e202 which is still flying well. Except on the first launch I did not have the stab adjustment screw on the platform, the plane went up rather flat and the glide was a dive, luckily no damage. My next two official flights were okay but short of a max. On the last flight the Pearl makes a huge circle around the edges of the field, I lost sight of where it landed but I had my tracker. This was my chance to use the tracker; I get a rather strong signal from the area by the two metal buildings across the field. 

Dave Comes to the Rescue

As I walk by the buildings I see at least two models but not mine. A guy cutting grass tells me there is a model in the next field beyond the buildings. I walk over there and these were high-tech FAI models, so I walk back towards the camp grounds. By now I am really doubting by ability to use the tracker; Dave Sechrist drives by on his little Honda motorcycle. He thought it could be by campground but drove in that direction and found nothing. It has to be towards the buildings and in a short jaunt on his cycle he found my plane real close to a building. He offered a ride back on the rack of his motorcycle and I accepted. Later I checked my smartphone as to how far I walked that day and it was a little over 14 miles. At least the flight was a max but my only one. What rather shocked me was looking at the results how even experts had poor flights that day.

Not just sure what I flew after that, I think it was catapult glider. I was really tempted to skip the event but thought at least I would try. Still using the catapult glider that I had so much trouble getting to transition early in the 2018 season but it is still flying. I was actually happy the flights were rather short because I did not want to walk too far. As I ended a gentleman gave me some advice on launching which helped, the guy was Ralph Ray.

I stayed out to the field rather late as that was the NFFS banquet night. Really a great meal and program afterwards, I really like the funny speech Bob Hanford gives, and great choices for the Hall of Fame members. Think I need at least one more blog post to cover my Nats adventure.


Bill Kuhl

It Flew Great Back Home – Nats 2018

Last week was my third Free Flight Nats contest in Muncie Indiana; for the most part weather was good, I learned a great deal, and had a fantastic time. I came home with all the planes I brought but some repairs are needed on a couple of the planes. On arriving late Saturday afternoon in rainy weather, I still went out to the field and flew my Super Pearl e36 between rain showers, there was one other plane flying. Sunday is the day many people use for testing before the start of the contest on Monday; I spent the morning flying non-stop and did more observing in the afternoon as the wind increased. My ½ A Streak for One-Design had been flown on small field back home but only the last time out did I feel it was close to trimmed. The flights on Sunday morning looked good, with no sign of trying to loop as it had back home. 

1/2 A Streak

Saturday Evening Flying

In the afternoon I flew my Blue Ridge Special with DT a few times just for fun. The last flight it went a little further and I had a heck of time finding it in the grass. Thought I had a good line on it and so did someone else but it seems that the smaller models such as e20 or this model with 14” wingspan disappear easily in the longer grass. Luckily someone on a motorcycle found it for me; I put it away after that.

Bob with electric Satellite

The rest of the day I was observing Bob fly his e36 Satellite and Craig fly his Big Dog electric. Bob had a very nice looking e36 Satellite that was giving him fits to adjust but had flown well back home. I took video of the second short test flight and the model rolled inverted and crashed, damage was extensive.

Craig with Big Dog Electric

Craig had this well-built larger electric model that just didn’t want to transition properly, it starts on a nice right climb, then straightens out which cause it to stall after the motor cut. At this point it would either dive or do a tail slide.  Larry, Bob, and Jim, a combination of many years of free flight experience had Craig try all sorts of adjustments to thrust, rudder, etc. and it was not helping. After an adjustment had been put in it would be taken out and another adjustment tried. It did get better and I understand it did get sorted before contest flying but was destroyed after hitting something on the field.

Eureka E36

I flew my Eureka e36 many times but was noticing the trim change also. The wing mount appeared to be loose but after fixing it the issue appeared again. After making one official flight, it spiraled in to the right and broke the fuselage. Not an extensive repair needed but I am going to recover the wing with Polyspan Lite. I would have done this before but was running out of time before the contest. With no diagonal structure in the wing, I can image there can be flexing going on when tissue gets loose. I remember last year after a crash from a bad launch of my E36 Starduster the repaired wing would do funny things as the motor run was increased.  The ½ A Streak I covered with Polyspan Lite appeared to stay in trim well. It is not much more work, just that multiple coats of color and dope are needed.

 Just for fun I flew my Flying Aces Moth and it worked well but went back to old habit of crashing to the right, more fuselage repair is needed.

 Paul had a really squirrely flight with a very well built embryo model, it had flown great the day before. We have been discussing ideas of what differences were between the flying on two different days.

In conclusion, free flight can be even more challenging than I had thought. I learned much but also realize there is way more I do not know.  With the air conditions a big part of flight duration, even the experts have bad flights on occasion. 

Bill Kuhl

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